research article the synergistic effect of nitrogen dopant and...

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2013 Article ID 268723 13 pageshttpdxdoiorg1011552013268723

Research ArticleThe Synergistic Effect of Nitrogen Dopant and CalcinationTemperature on the Visible-Light-Induced Photoactivity ofN-Doped TiO2

Yao-Tung Lin1 Chih-Huang Weng2 Hui-Jan Hsu1 Yu-Hao Lin1 and Ching-Chang Shiesh3

1 Department of Soil and Environmental Sciences and Center of Nanoscience and NanotechnologyNational Chung Hsing University TaiChung 402 Taiwan

2Department of Civil and Ecological Engineering I-Shou University Kaohsiung 84001 Taiwan3Department of Horticulture National Chung Hsing University TaiChung 402 Taiwan

Correspondence should be addressed to Yao-Tung Lin yaotungnchuedutw

Received 9 January 2013 Revised 28 March 2013 Accepted 29 March 2013

Academic Editor Jiaguo Yu

Copyright copy 2013 Yao-Tung Lin et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The synergistic effect of nitrogen content and calcinations temperature on the N-doped TiO2catalysts prepared by sol-gel method

was investigated The phase and structure chemical state optical properties and surface areapore distribution of N-doped TiO2

were characterized using X-ray diffraction spectrometer high-resolution transmission electron microscope X-ray photoelectronspectroscopy UV-vis diffusion reflectance spectroscopy and Brunauer-Emmett-Teller specific surface area Finding showed thatthe photocatalytic activity ofN-dopedTiO

2was greatly enhanced compared to pure TiO

2under visible irradiation N dopants could

retard the transformation from anatase to rutile phase Namely N-doping effect is attributed to the anatase phase stabilizationTheresults showed nitrogen atoms were incorporated into the interstitial positions of the TiO

2lattice Ethylene was used to evaluate

the photocatalytic activity of samples under visible-light illumination The results suggested good anatase crystallization smallerparticle size and larger surface are beneficial for photocatalytic activity of N-doped TiO

2TheN-doped TiO

2catalyst prepared with

ammonia to titanium isopropoxide molar ratio of 20 and calcinated at 400∘C showed the best photocatalytic ability

1 Introduction

Titanium dioxide (TiO2) is an effective photocatalyst due to

its inexpensiveness chemical stability nontoxicity biologi-cal and chemical inertness and long-term stability againstphoto-corrosion and chemical corrosion [1 2] In the lasttwo decades many works have been done on expandingand augmenting the utility of TiO

2in heterogeneous pho-

tocatalysis (eg water purification air cleaning and watersplitting for the production of hydrogen) [2ndash5] self-cleaningsurfaces [6] inactivation of bacteria and fungi [7 8] solarcells [9] anticorrosive coatings [10] and Li-ion batteries [11]TiO2has three phases in nature brookite (orthorhombic)

anatase (tetragonal) and rutile (tetragonal) It is amorphousat temperature up to 300∘C becoming anatase and rutiletypically at 350 and 800∘C respectively [3] Anatase powderwith good crystallinity small grain size and high specific

surface area is desirable as long as the photocatalytic activityis concerned However its wide band gap of 32 and 30 eVfor anatase and rutile polymorphs respectively requires UVlight for the excitation of electron-hole pairs It only uses 4-5 of the UV light in the solar irradiation To utilize solarenergy effectively many attempts have been made to modifythe properties of TiO

2 such as doping with transition metal

ions [12ndash14] or nonmetal anions [3 15ndash23] and sensitizationwith organic dyes [24 25] Among the nonmetal-dopingTiO2photocatalysts the simplest and most feasible TiO

2

modification approaches for achieving visible-light-drivenphotocatalysis seem to be N-doping that is doping nitrogenatoms into interstitial (or substitutional) sites in the crystalstructure of TiO

2 Sato [4] was the first to report on nitrogen-

doped TiO2 It was treated with various nitrogen sources

such as urea ammonia ammonium chloride and nitricacid Asahi et al have prepared TiO

2minus119909N119909films whose

2 International Journal of Photoenergy

absorption activity not only was shifted toward the longervisible wavelength but also had higher thermal stability andless recombination centers of charge carries than the metal-doped TiO

2[5] However to date little research has been

conducted on gaining in-depth information on the propertiesof the interstitial (or substitutional) N-doped TiO

2 as well as

its photocatalytic activity Different dopants result in TiO2of

different properties and consequently alter the photocatalyticactivity of the materials Currently few works have focusedon the synergistic effects of nitrogen dopant and calcinationtemperature on the characteristics and visible-light-inducedphotoactivity of N-doped TiO

2[6]

In this study we focused on sol-gel synthesis process forthe preparation of nitrogen-doped TiO

2catalysts (N-TiO

2)

because the wet processes have the advantages of low costease of scale-up and stablility for practical applications Theeffects of N atom and calcination temperature on the struc-tural optical and photocatalytic properties of N-TiO

2were

assessedThe gel samples were calcined at 400 500 600 700and 800∘C The photocatalysts were characterized using X-ray diffraction (XRD) high-resolution transmission electronmicroscope (HRTEM) X-ray photoelectron spectroscopy(XPS) UV-vis diffusion reflectance spectroscopy (UV-visDRS) Brunauer-Emmett-Teller (BET) specific surface area(119878BET) and thermogravimetric-differential thermal analysis(TG-DTA) The transition from amorphous to anatase andrutile phases at different calcination temperatures was alsoexplored Ethylene was chosen as a probe reactant becauseit is structurally simple has relatively high reactivity and isthe parent compound of many widespread volatile organiccompounds (VOCs) of environmental concern (eg TCE andtetrachloroethylene) The object of this study is to investigatethe synergistic effects of nitrogen content and calcinationtemperatures in the synthesis process of N-doped TiO

2

prepared by sol-gel process and to investigate the influenceof ethylene on photocatalytic decomposition

2 Materials and Methods

21 Preparation of N-Doped TiO2Catalyst Titanium iso-

propoxide (TTIP C12H28O4Ti 97 Aldrich) a highly re-

active alkoxide was used as precursor Aqua ammonia(NH4OH) was used as nitrogen source A given amount of

aqua ammonia was added to the distilled water while beingstirred until it completely dissolved at room temperatureThen the solution was added dropwise to a constant amountof titanium isopropoxide as to obtain an aqua ammoniato TTIP molar ratio (AT) of 1 1 the TiO

2sample was

designated as N-TO2 While the mixture was being stirred

vigorously the urea solution was introduced to the TTIPHydrolysis and ploycondensation reactions occurred Thereactant was stirred continuously for one hour after all aquaammonia solution was dissipated The sol was aged in air for24 hr to allow further hydrolysis The final sol was left on thebench top to allow thickening After aging the sol was driedat 70∘C for 24 hr to evaporate the solventThe residual xerogelwas crushed to fine powder before calcined in a furnace at400 500 600 700 and 800∘C respectively for 3 hr Pure

TiO2powder was also prepared without the presence of aqua

ammonia following the same procedures as described aboveThe nitrogen-doped samples were labeled AxTy where 119909and 119910 refer to the aqua ammonia to TTIP molar ratio (AT)and calcining temperature respectively For example A20T4means the N-TiO

2prepared with AT molar ratio 20 and

calcinated at 400∘C

22 Characterization The 119878BET of the samples was deter-mined using nitrogen adsorption method measured with aMicromeritics ASAP 2020 adsorption apparatus Pore sizeand pore volume were calculated by the BJH isotherm Thecrystallization behavior and stability of N atoms in N-TiO

2

were monitored using a TG-DTA (STA 6000 PerkinElmer)while the sample was being heated from room temperatureto 1000∘C at 10∘CminThe morphology structure and grainsize of the samples were characterized by a high-resolutiontransparent electromicroscopy (HRTEM JEM-2010 JEOL)To study the optical response of N-TiO

2samples (120582 = 200ndash

800 nm) UV-vis DRS (U3900H Hitachi) were recordedusing a spectrophotometer with an integrating sphere attach-ment and Al

2O3was used as the reference The chemical

environment information and the N concentration of all ofthe samples were measured by X-ray photoelectron spectra(XPS) (PHI 5000 VersaProbeScanning ESCA Microprobewith aC

60ion gun) All sampleswere collected in vacuumand

transferred to the main ultrahigh-vacuum (UHV) chamberfor measurements The shift of binding energy due to relativesurface charging was corrected to the C 1s level at 285 eV asan internal standard The XPS peaks were assumed to haveGaussian line shapes and were resolved into components by anonlinear least-squares procedure after proper subtraction ofthe baseline The crystallinity and phase of the samples wereanalyzed byXRD (PANalytical XrsquoPert-ProMPDPW304060)with Cu-Ka radiation at a scan rate of 005∘ 1s in the rangefrom 20 to 80∘

23 Photooxidation Performance The experiment setup andoperating conditions for photocatalytic activity tests werethe same as those reported previously [7] The catalyst wasprepared by depositing suspension of the as-prepared catalystat the bottom surface of the reactor that was subsequentlydried at ambient conditionThe obtained catalyst film densityon the bottom surface of reactor was kept at 4mgcm2 Theexperiment setup and operating conditions for photocat-alytic activity tests were the same as those in our previousreports [7] The photocatalytic activity experiments of theas-prepared catalysts for the oxidation of ethylene in gasphase were performed at room temperature using a 250mLphotocatalytic reactor Air with 60 relative humidity waspassed through the reactor with the sample inside for 1 hrto reach equilibrium and then a desired amount of ethylenewas injected into the reactor with a gastight syringe Theethylene inside the reactor was taken at regular intervals withgas-tight syringe and analyzed using gas chromatographs(PerkinElmer Clarus 500 USA) equipped with a flameionization detector (FID) and a thermal conductivity detector(TCD) detection The GC instrument was equipped with an

International Journal of Photoenergy 3

Elite-Plot-Q capillary column (Agilent Technologies) Theethylene was allowed to reach adsorption equilibrium withthe catalyst in the reactor prior to irradiation Two 500-W horizontal halogen lamps (95 cm in length PHILIPS)were used to simulate the solar light The lamp equippedwith a cut-off filter (120582 gt 400 nm) was vertically placedoutside the photocatalytic reactor Light intensity at thecatalyst surface was 16mWcm2 Blank experiments usingan uncoated (no catalyst) glass plate had no effect on theethylene concentration and did not generate any carbonmonoxide or carbon dioxide (see supplementary materialonline at httpdxdoiorg1011552013268723) The photo-catalytic activity of the catalyst can be quantitatively evaluatedby comparing the apparent reaction rate constants

3 Results and Discussion

31 Thermal Analysis To investigate the process of phasetransformation of titanium(IV)-oxide-hydroxide to titaniumoxide and the effect of nitrogen doping content on thetransformation from anatase to rutile thermoanalytic tech-niques including TGA and DTA were conducted Typicallythe hydrothermal weight loss is attributed to a multistepof polycondensation of titanium(IV)-oxide-hydroxide andphase transformation of anatase into rutile or brookite fromroom temperature to 700ndash800∘C as shown in Figure 1 andTable 1 DTA measurements established the transformationof TiO

119909(OH)119910into TiO

2including two endothermic and

one exothermic peaks from room temperature to 398∘C(Figure 1) A sharp endothermic peaks at 105∘C due to therelease of absorbed water while the other minor peak at253∘C is referred to as the desorption of organic Therewas a corresponding weight loss from TGA of about 198and 94wt respectively In the region mentioned abovethe finely exothermic peak around 276∘C is ascribed to thethermal decomposition of unhydrolyzed TTIP with about08 wt weight loss The weak thermal effect at 276ndash730∘Cis accompanied by obvious exothermic peak at 451∘C whichcan be assigned to the crystallization of the amorphous phaseto anatase At around 730∘C an obvious exothermic peakwas observed owing to the oxidation of carbon residue andevaporation of chemisorbed water which can be assignedto the phase transformation from anatase titania to rutileTiO2 It can be concluded from the DTA result that the as-

prepared TiO2sample was amorphous According to TGA

the weight loss roughly consists of three distinct stages Thefirst stage was up to 276∘C over which the mass loss is thegreatest A mass loss of up to 30 was observed which isattributed to the evaporation of the physical adsorbed waterand the release of organic The second stage is from 276 to451∘C where the mass loss is about 17This corresponds tothe thermal decomposition of unhydrolyzed TTIP The thirdstage is from 451 to 730∘C and the mass loss is about 07which is attributed to the removal of chemisorbed water Atabout 730∘C no mass loss was observed The exothermicpeaks of N-TiO

2prepared at 05 10 and 20 AT ratios

were at 710 720 and 730∘C respectively (Table 1)The resultsindicated that nitrogen atoms doped in TiO

2could prevent

100

80

60

40

20

0

60

50

40

30

20

10

00 100 200 300 400 500 600 700 800

Wei

ght l

oss (

)

Hea

t flow

(mW

mg)

Temperature (∘C)

198 94 17 07

105∘ C

253∘ C

276∘ C

451∘ C

730

∘ C

Anatase into rutile

Release of adsorbed water

Desorption of organics

Amorphous into anatase

Thermal decomposition of unhydrolyzed TTIP

Figure 1 TG-DTA curve of N-TiO2samples prepared with 20

ammoniaTTIP ratio

phase transition of anatase to rutile because as far as pureTiO2was concerned most TiO

2particles were transformed

into rutile at 700∘C

32 Phase and Structure The characteristics of N-TiO2at

various calcination temperatures and molar ratios of ATare summarized in Table 1 Figure 2 shows the XRD patternof the N-TiO

2samples at various AT ratios and annealed

at different temperatures The presence of peaks (2120579 =2544∘ 3806

∘ and 4824∘) was regarded as an attributive

indicator of anatase titania and the presence of peaks (2120579 =2754∘ 3614


indicator of rutile titaniaThediffraction peaks for the anatase(JCPDSno 21-1272) and rutile (JCPDSno 21-1276) phases aremarked with ldquoArdquo and ldquoRrdquo respectively and the correspondingdiffraction planes are given in parenthesis No N-derivedpeaks were detected in all the patternsThismay be caused bythe lower concentration of the doped species and the limiteddopants may have moved into either the interstitial positionsor the substitutional sites of the TiO

2crystal structure which

is consistent with [8 9] The average grain size was estimatedat 28ndash131 nm comparable to that from the HRTEM imageA comparison of XRD patterns clearly shows that nitrogendoping significantly changes the crystalline size and thecrystal structure of TiO

2

The transformation from the amorphous to the crys-talline form of TiO

2usually requires temperatures close

to 300∘C [8] For the samples prepared with 20 AT andcalcinated at 400ndash500∘C (Figure 2(a)) the intensities ofthe anatase peak are increased and the width of the (101)plane diffraction peak becomes narrower as the calcinationtemperature increases implying an improvement and growthin crystallinity Increasing the temperature to 800∘C theintensity of anatase peak decreases but the rutile peaksappear suggesting the transformation of anatase to rutilephase The average crystalline size was 32 85 and 103 nmand the mass percentage of anatase was 90 60 and 6 forsamples prepared at 20 AT and calcination temperature


Table 1 Characteristics for N-TiO2 at various ammoniaTTIP molar ratios under different calcination temperatures

SampleaXRD BET TG-DTA TEM Optical properties

Phase ratio Crystallite size Surface area (m2g) Abrarr Rc Temp (∘C) Size (nm) 1205821198921 1198641198921 1205821198922 1198641198922

Ab Rc Ab (nm) Rc (nm) (nm) (nm) (nm) (nm)A00T4 90 10 32 mdash 93 703 11 plusmn 1 392 316 mdash mdashA05T4 89 11 28 mdash 108 710 12 plusmn 1 392 316 505 246A10T4 90 10 28 mdash 119 720 12 plusmn 1 391 317 506 245A15T4 87 13 29 mdash 119 728 11 plusmn 1 388 320 513 242A20T4 90 10 32 mdash 98 730 12 plusmn 1 390 318 510 243A25T4 90 10 37 mdash 98 728 12 plusmn 1 392 316 515 241A30T4 92 8 37 mdash 86 729 12 plusmn 1 392 316 514 241A00T5 94 6 46 mdash 50 703 13 plusmn 2 402 308 mdash mdashA05T5 89 11 46 98 64 710 13 plusmn 1 404 307 503 247A10T5 90 10 41 87 68 720 15 plusmn 2 400 310 508 244A15T5 91 9 40 mdash 71 728 15 plusmn 2 396 313 517 240A20T5 94 6 45 mdash 62 730 15 plusmn 2 394 315 513 242A25T5 94 6 49 mdash 55 728 17 plusmn 2 397 312 507 245A30T5 94 6 47 mdash 53 729 17 plusmn 2 397 312 510 243A00T6 34 66 106 156 7 703 24 plusmn 2 420 295 mdash mdashA05T6 14 86 86 128 8 710 40 plusmn 3 422 294 mdash mdashA10T6 14 86 81 132 9 720 40 plusmn 4 425 292 mdash mdashA15T6 22 78 79 141 14 728 35 plusmn 3 424 292 mdash mdashA20T6 60 40 85 184 17 730 34 plusmn 3 415 299 mdash mdashA25T6 78 22 90 184 16 728 35 plusmn 4 416 298 mdash mdashA30T6 74 26 97 169 12 729 36 plusmn 4 415 299 mdash mdashA00T7 6 94 131 177 2 703 80 plusmn 5 424 292 mdash mdashA05T7 3 97 95 148 5 710 145 plusmn 10 428 290 mdash mdashA10T7 3 97 102 149 6 720 145 plusmn 10 429 289 mdash mdashA15T7 3 97 92 159 6 728 150 plusmn 11 428 290 mdash mdashA20T7 6 94 103 163 4 730 170 plusmn 13 428 290 mdash mdashA25T7 15 85 108 178 8 728 60 plusmn 6 426 291 mdash mdashA30T7 15 85 117 182 6 729 60 plusmn 6 427 290 mdash mdashA00T8 1 99 mdash 174 3 703 200 plusmn 17 424 292 mdash mdashA05T8 1 99 mdash 161 3 710 190 plusmn 15 428 290 mdash mdashA10T8 1 99 mdash 159 3 720 160 plusmn 13 429 289 mdash mdashA15T8 1 99 mdash 171 3 728 170 plusmn 15 428 290 mdash mdashA20T8 1 99 mdash 164 2 730 160 plusmn 14 428 290 mdash mdashA25T8 3 97 106 184 4 728 200 plusmn 18 427 290 mdash mdashA30T8 3 97 127 179 3 729 170 plusmn 15 429 289 mdash mdashaAXXTY ammoniaTTIP molar ratio = 0XX calcination temperature = Y00∘CbAnatasecRutile

of 400 600 and 700∘C respectively The maximum meansize of anatase and rutile crystallites was observed at 800∘CResults agreed with those reported that the crystalline sizegrows and the content of anatase diminishes as calcinationtemperature increases [8 10ndash13] For the samples prepared at05 AT the anatase peaks appear at temperatures 400 and500∘C Increasing the temperature to 500∘C the intensity ofanatase peak decreases but the rutile peaks appear Whentemperature is increased further to 600∘C rutile becomesa main phase In this case the anatase-to-rutile phasetransformation temperature is between 400 and 500∘C XRD

patterns of samples prepared at 30 AT and annealed at700∘C show both anatase and a rutile phase indicating thatanatase-to-rutile phase transformation is shifted to highertemperature It can be seen that the presence of nitrogencan restrain the formation and growth of TiO

2crystal phase

thereby retarding the anatase-to-rutile phase transformationThis result is further supported by the appearance of rutilein XRD patterns of sample prepared at 05 and 15 GTat 600∘C and disappearance for samples prepared at GTgreater than 20 at 600∘C (data not shown) Comparedwith P25 the peak position of the (101) plane of N-doped


A A A

A A

AR

R

RR R R

(101) (110) (004) (204)(200)

(105)(211)

(101)

(111)

(210) (211) (220)

Inte

nsity

(au

)

20 30 40 50 60 70 80

Calcination temperature (∘C)400

500

600

700

800

2120579 (deg)

AT ratio 2

(a)

A A A A A A(101) (004) (204)(200)(105)(211)

Inte

nsity

(au

)

20 30 40 50 60 70 80

0051

15

2253

2120579 (deg)

AT ratio

Calcination temperature 400∘C

P25

(b)

Figure 2 XRD patterns of N-TiO2samples prepared (a) at various calcination temperatures and (b) with various ammoniaTTIP ratios

TiO2shifted slightly to higher 2120579 value and the peak was

broader as NT ratio increases suggesting distortion of thecrystal lattice of TiO

2by the incorporation of nitrogen The

crystalline sizes of samples calcinated at 400∘C and pre-pared at 05 15 20 and 30 AT were 28 29 32 and37 nm respectively The average crystalline size of samplesincreases with increase in AT revealing that nitrogen canenhance the growth of N-TiO

2crystals Results agreed with

those reported that the crystalline size grows as nitrogento Ti proportion increases [14] The results reveal that thephase transformation temperature of anatase to rutile wasprogressively increased when the amount of N dopant wasincreased Clearly calcination temperature andAT ratio playa significant role in the formed crystal structure and particlesize (Figure 3)Higher temperature favors the growth of rutilestructure and produces N-TiO

2nanoparticles with larger

particle size Thus a fine control of calcination temperatureand AT ratio is crucial for obtaining a pure phase of N-TiO

2

Further insights into the effect of calcination and dopingon the morphology and structure of the N-TiO

2samples can

be obtained from HRTEM image (Figure 4) The selectedarea electron diffraction pattern and TEM confirmed itshighly crystalline anatase or rutile structure The observedd-spacing from HRTEM image is 3522 A and is comparableto 352 A previously reported for (101) crystallographic planeof undoped anatase [15ndash18] The HRTEM image showedthe nanocrystallines with primary grain size around 11ndash200 nm From the TEM images the particles in N-TiO

2

samples are monodispersed The crystalline form aggregateswith a mesoporous structure The formation of mesoporousstructure is similar to that reported in the literature [1920] First monodispersed amorphous titanium oxide solparticles are formed by the hydrolysis processes Then themonodispersed sol particles are crystallized and aggregatedunder calcination treatment to form mesoporous crystallineBased on the HRTEM results the calcination temperature

100

80

60

40

20

0400 500 600 700 800Calcination temperature (∘C)

AmmoniaTTIP molar ratio

Ana

tase

()

005115

2253

Figure 3 The anatase content of N-TiO2samples as a function of

the various ammoniaTTIP molar ratios

significantly changes the size of particles (Table 1) The grainsize of crystalline is in consistent with the calculated valueobtained from XRD patterns (Table 1) The grain size ofsamples increases with the calcination temperatureMorpho-logical observation by TEM and XRD calculations revealsthat the large particle size of A20T8 was mainly caused byagglomeration and the growth of crystallite size

33 Surface Area and Pore Size Distribution Typical nitrogenadsorption-desorption isotherms of N-TiO

2photocatalyst


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)

Figure 4 TEM images of N-TiO2prepared (a)ndash(e) at various calcination temperatures with 20 ammoniaTTIP ratio and (f) the selected

area electron diffraction of A20T4

are shown in Figure 5 The 119878BET of N-TiO2prepared with 20

AT ratio at calcined 400 500 600 700 and 800∘C was 9862 17 4 and 2m2g respectively Obviously the values of119878BET and pore volume of N-TiO

2prepared with the same AT

ratio decreased with increasing calcination temperaturesSuch phenomenon could be attributed to the collapse of themesoporous structure the growth of TiO

2crystallites and

the removal process of nitrogen core by high-temperaturecalcination Consequently N-TiO

2calcined at 800∘C has the

least 119878BET Based on the results obtained the hysteresis loop ofN-TiO

2is significantly shifted in direction of higher relative

pressures as calcination temperature increases indicatingmuch larger mesorpore The average pore size of N-TiO

2

increased with increasing calcination temperature due to theformation of slit-like pores [21]

The N-TiO2samples obtained at various calcination

temperatures gave different nitrogen adsorption isotherms(Figure 5) implying differences in their porous structureThe N-TiO

2samples prepared at low calcination temperature

(ie 400 and 500∘C) exhibited a type IV isotherm and atype H2 hysteresis loop at lower relative pressure regionwhich are typical characteristics of mesoporous structurewith ink bottle pores Note that the adsorption branches ofthese isotherms resembled type II indicating the presence ofsome macropores Otherwise the N-TiO

2samples prepared

at higher calcination temperature (ie 600ndash800∘C) exhibiteda type V isotherm and a type H3 hysteresis loop at higherrelative pressureThe hysteresis loop at lower relative pressureregion (04 lt 119875119875

0lt 08) was attributed to a smaller mes-

opore while that at the higher relative pressure (08 lt1198751198750lt 10) was of larger mesopores Thus samples prepared

at high calcination temperature (gt600∘C) had a wide poresize distribution in the mesopores scale The isotherm of N-TiO2prepared at higher calcination temperature was below

that of lower calcination temperature (Figure 5) indicatinglower surface area and pore volume of the former Furtherobservation from Table 1 indicated that 119878BET for the N-TiO

2

samples at the same AT ratio increased with increasingcalcination temperature (Figure 5(c)) Results reveal thatall N-TiO

2samples calcined at various temperatures show

monomodal pore size distributions and mesopores may beassigned to the pores among interaggregated particles (datanot shown) With calcination temperature increasing thereis a significant tendency of pore size distribution toward tothe bigger pore size The increase of pore size is due to thecorruption of smaller pores during calcination as the smallerpores endured much greater stress than the bigger poresFormation of bigger crystalline aggregation upon increasein temperature could form bigger pores also Consequentlythe pore size increases while the pore volume decreases with


200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV

AmmoniaTTIP ratio 2Calcination temperature (∘C)

Qua

ntity

adso

rbed

(cm

3g

STP

)

Relative pressure (1198751198750)

(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3

Calcination temperature 400∘CAmmoniaTTIP ratio

Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800

Calcination temperature (∘C)

Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)

Figure 5 Nitrogen adsorption and desorption isotherms of N-TiO2samples (a) calcined at various temperatures (b) prepared with various

ammoniaTTIP molar ratios the surface area as a function of calcination temperature

calcinations temperature increasing Based on the TEM andBET results the mesopores of TiO

2were decreased due

to the heat shrinkage of calcination The results indicatedthat calcination at high temperature and in the presence ofnitrogen atoms will help to improve the thermal stabilityof the photocatalyst While the calcination temperature wasincreased both the specific surface area and the pore vol-ume of N-TiO

2samples decreased This indicated that the

average pore size increased while the pore volume and the

specific surface area decreased with calcination temperatureincreasing

34 Optical Properties The typical UV-vis diffuse reflectancespectra of N-TiO

2are shown in Figures 6(a) and 6(b) It can

be seen that nondoped TiO2(P25) has only one light sharp

edge (120582 = 410 nm) which can be assigned to the band gapof TiO

2 while part of N-TiO

2showed two absorption edges

and a noticeable shift to the visible light region as compared


400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Wavelength (nm)Calcination temp (∘C)

05

04

03

02

01

0350 400 450 500 550

NTi 2 molar ratiocalcination at different temperatures

AT ratio 2

A20T4A20T5A20T6A20T7A20T8

P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540

Calcination at 400∘C temperaturedifferent NTi molar ratios

325

215

1050P25

A00T4A05T4A10T4A15T4

A20T4A25T4A30T4

AT ratio


(b)

Figure 6 The typical UV-vis DR spectra of N-TiO2samples (a) prepared with 20 ammoniaTTIP molar ratio and calcined at various

temperatures (b) prepared with various ammoniaTTIP molar ratios and calcined at 400∘C

to that of the TiO2(ie P25) This phenomenon should be

ascribed to either the nitrogen doping andor sensitizationby a surface-anchored group The calcination temperatureand AT ratio are the crucial factor that can further affectthe absorption as seen in Figure 6 Similar phenomenonhad been reported by previous publications [17 22ndash25] Theabsorption edges of the N-TiO

2samples show continuous

red shift as the calcination temperature changes from 400to 700∘C which can be assigned to the intrinsic band gapabsorption of TiO

2 The shift is too minor to be observed

when the calcination temperature changes from500 to 600∘Cwhich is possibly caused by the synergetic effect of the loss ofthe nitrogen and the increase of the TiO

2crystallinity during

the calcination processThe absorption threshold (120582119892) can be

determined using the onset of the absorption edges by thesection of the fitting lines on the upward and outward sectionof the spectrum (shown in the graph inserted in Figure 6)[23] Table 1 lists the determined 120582

119892(nm) and the derived

band gap energy values The band gap of N-TiO2(119864119892) was

calculated using the 119864119892= 1240120582

119892equation It also can be

seen that N-TiO2samples have two characteristic light

absorption edges One of them corresponds to the band gapof TiO

2(1205821198921= 390sim430 nm) while the other originates from

the N-induced midgap level (1205821198922= 505sim517 nm) The color

of the samples was different with calcination temperatureand AT ratio The color of N-TiO

2samples prepared with

20 AT ratio and calcinated at 400 600 and 700∘C wasvivid yellow yellow and white respectively There is no 120582

1198922

when N-TiO2calcinated above 600∘C It can be ascribed to

the amount of N dopant decreased The color of N-TiO2

prepared with 00 10 20 and 30 AT ratio and calcinatedat 400∘C was white pale yellow yellow and vivid yellow

respectively The phenomenon that the AT ratio increasesthe shifting of the spectra towards visible region was clearlyobserved (Figure 6(a)) The absorption threshold (120582

119892) was

increased with increasing AT ratio It reveals that morenitrogen doping in the matrix of TiO

2structure results in a

shift of absorbance region toward visible light wavelengthThis is possible attribute to the nitrogen incorporated intoTiO2lattice and formation of new electronic state above

valence band caused by nitrogen doping to generate a redshift

35 Analysis of Chemical State The chemical states of dopingimpurity are critical to the optical property band gap andphotocatalytic activity of nitrogen-dopedTiO

2 To investigate

the chemical states of the doping nitrogen XPS spectra wereapplied to examine three regions the Ti 2p core level near460 eV the O 1s core level near 530 eV and the N 1s core levelnear 400 eV Figure 7 shows the experimental observation ofsurface chemical composition and the electronic structuresof N-TiO

2samples using XPS XPS peaks showed that the N-

TiO2contained only Ti O N elements and a small quantity of

carbon The presence of carbon was ascribed to the residualcarbon from the precursor solution and the adventitioushydrocarbon from the XPS instrument itself In Figures 7(a)and 7(b) the binding energy (BE) peaks corresponding toN 1s core levels for N-TiO

2are observed one major peak at

400 eV The N 1s peak at 400 eV is ascribed to the presenceof the oxidized nitrogen species and the nitrogen may beincorporating into the interstitial positions of the TiO

2lattice

and to form a TindashOndashN structure [26 27] No other N 1s peakswere detected in N-TiO

2samples As shown in Figure 7 N 1s

peak at 400 eV slightly decreased with increasing calcination


Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400

Calcination temp (∘C)Ti-O-N

390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)

Calcination temp 400∘C

325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400

Calcination temp (∘C)

Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400

Calcination temp (∘C)AT ratio 2Ti4+2p32

Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)

Figure 7 XPS survey and core level spectra of (a)-(b) N 1s (c)-(d) Ti 2p and (e)-(f) O 1s of N-TiO2samples

temperature This is different from the N-TiO2prepared by

flame oxidation in which nitrogen partially substitutes theoxygen sites in the TiO

2[28] The preparation method plays

an important role in determining the nitrogen state in TiO2

band structure [26 29 30]Depending on the nitrogen source

and experimental conditions N species are incorporated intoTiO2in interstitial form or substitutional form [31 32] The

interstitial N-doping is favored when the doping is carriedout under oxygen-rich conditions and the substation-typeN-doping occurs under reducing conditions [31ndash33] Therefore


from the atomicN 1sXPS spectra the interstitial sites (400 eV)were observed under air atmosphere

The XPS spectra of Ti 2p regions are shown in Figures7(c) and 7(d) The peaks at around 4585 and 4642 eV forP25 are ascribed to Ti 2p

32and Ti 2p

12of TiO

2(data not

shown)The line separation between Ti 2p12

and Ti 2p32

was57 eV which is consistent with the standard binding energyAccording to Figure 7 all spectra of Ti 2p

12are symmetry

The spectra of Ti 2p12

are consistent of single state and thebanding energy of peaks is 4580ndash4583 eV which shows aredshift of 05 eV compared to the binding energy of Ti4+in P25 This suggests that Ti3+ was present in N-TiO

2and

the distance of peaks between Ti 2p12

and Ti 2p32

is 57ndash59 eV The 396 eV peak is assigned to the atomic b-N stateand generally proves the presence of TiAN bonds formedwhen N atoms replace the oxygen in the TiO

2crystal lattice

[30]The peak characteristic for TindashN (396 eV) is not presentindicating the absence of the TiN phase in the N-TiO

2

samples [34]The results show that the binding energies of Ti2p peaks shift to lower energieswith a negative shift ofsim05 eVfor the N-TiO

2due to the N doping [27] The lower binding

energy than a typical Ti 2p signal of Ti4+ oxidation state sug-gests that titanium cation has a considerable interaction withthe doped nitrogen and thus TiO

2lattice is modified [27

35] Nitrogen doping accompanies the formation of oxygenvacancies andor Ti3+ defects resulting in slight shifts of theTi 2p peak toward the lower binding energy [36ndash38] Hencethe red shifts of the Ti 2p peak in comparison with P25 areused to highlight the successful nitrogen doping into the TiO

2

lattice The XRD results did not indicate the formation ofTiN bondsTherefore results indicate that the titanium atombonds with oxygen but not nitrogen Thus a shift towardlower binding energy of Ti 2p and the binding energy of N1s upon nitrogen addition indicate that the nitrogen can beindeed incorporated into the interstitial positions of TiO

2

lattice and the formation of TindashOndashN bonding by partiallyinterstitial with a carbon atom

The incorporation of nitrogen into the oxide latticeshould influence the BE of O 1s as wellTheXPS spectra of theO 1s core level consists of the one peak (Figures 3(e) and 3(f))at around 5293ndash5295 eV which is ascribed to TindashO bondin the TiO

2lattice [30] The O 1s core level moved toward

lower energy state from 5296 eV in P25 to 5294 eV in N-TiO2prepared with AT ratio 30 and calcined at 400∘C The

peak shifts by sim02 eV which might be related to the creationof oxygen vacancies as a result of the nitrogen doping Theshifting of bind energy in both N 1s and O 1s region indicatesthat nitrogen was incorporated into the lattice The shifts ofTi 2p32

and O 1s peaks are due to the introduction of oxygenvacancies into the TiO

2lattice [32] The presence of nitrogen

dopant facilitates the formation of oxygen vacancies Theaforementioned results clearly indicate that nitrogen dopingis accompanied by oxygen vacancy formation The opticaltransitions between the dopant and dopant-induced level andTi3d orbital explain the observed visible light absorptions ofN-TiO

2nanomaterials The observed two absorbance edge

features in the UV-vis spectra are directly related to the abovemodification of the electronic states from the dopants

50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C

Figure 8 The removal efficiency of ethylene photooxidation overN-TiO

2as function of the various ammoniaTTIP molar ratios

Experimental conditions [C2H4] = 200 ppmv [H

2O]= 25060 ppmv

[O2] = 21 light intensity = 16mWcm2 temp = 30∘C reaction time

= 3 h

36 Visible Light Photocatalytic Activity To explore the pho-tocatalytic activity of different N-doped TiO

2at different

calcination temperatures and AT ratios the degradationof ethylene under visible light with a cut-off wavelengthof 400 nm was investigated Carbon dioxide started beingformed immediately after the visible light was turned on andethylene was almost totally converted to CO

2in all mea-

surements It is obviously that the N-TiO2shows significant

progress in the photodegradation of ethylene compared toP25 in visible light system P25 has no obvious photocatalyticactivity (less than 1) under visible light irradiation Resultssuggest modification of TiO

2provides visible-light-sensitive

photocatalyst which can be applied to the photooxidationof ethylene gas as the band gap of TiO

2was modified by

nitrogen doping evidenced by XPS and UV-visible DRSresults Figure 8 shows the activity of N-TiO

2catalysts in the

presence of visible light for photodegradation of ethyleneThe reaction rate increases with the increase in the AT ratiofrom 05 to 20 and then decreases in AT ratio from 20to 30 The enhancement of photocatalytic activity can beascribed to an obvious improvement in anatase crystallinityand larger surface area For the sample prepared with ATratio 20 and 30 however the removal efficiency decreasedrapidly which can be due to its less surface area Thephotocatalytic ability of N-TiO

2samples calcinated at 400

500 and 800∘C is also examined It was found that thephotocatalytic activity decreased with increasing calcinationtemperature The enhancement of photocatalytic activitycan be ascribed to an obvious improvement in anatasecrystallinity at 400∘C calcination temperature Good anatasecrystallization is beneficial for reducing the recombinationrate of the photogenerated electrons and holes due to thedecrease in the number of the defects [39] Zhao and Yangshowed that for photocatalytic oxidation application anataseis superior to rutile (a) the conduction band location foranatase is more favorable for driving conjugate reactions


32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4

eminuseminusTiIII OH

TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV

Figure 9 Schematic diagram for the process in the photooxidation of ethylene and electron transfer process over N-TiO2under visible light

illumination

involving electrons and (b) very stable surface peroxidegroups can be formed at the anatase during photo-oxidationreaction but not on the rutile surface [40] For the samplecalcined at 800∘C the removal efficiency decreased rapidlywhich can be due to its fewer amounts of anatase andsmall 119878BET The result indicates that higher specific surfacearea smaller crystallite size and good anatase crystallizationwill promote the photocatalytic activity in visible light Theresults indicate the N-TiO

2catalyst prepared with AT ratio

20 and calcinated at 400∘C shows the best photocatalyticability

37 The Formation Mechanism of N-Doped TiO2 For the

pure TiO2 the energy of the visible light is not sufficient

to excite electrons from the valence band (VB) as theintrinsic band gap of pure TiO

2 Based on the results of UV-

vis DRS XRD and XPS the nitrogen atoms were weavedinto the crystal structure of TiO

2with structure as TindashOndash

N N-TiO2was active in the visible light irradiation for

the degradation of ethylene The following explanation forthe photocatalytic activity of N-TiO

2in the visible light

spectra can be consideredThe nitrogen existing at interstitialpositions of TiO

2lattice induces localized occupied states and

forms midband gap leading to the red shift of absorptionedge and photocatalytic activity under visible light irradiation[41] The electron (eminus) can be excited from the N-impuritylevel to the conduction band (CB) The exited electrons aretrapped by O

2adsorbed on the catalyst surface producing

O2

minus∙ superoxide anion radicals After a series of reactions(1)ndash(12) ethylene molecules are finally mineralized into CO

2

DFT calcinations and experimental results indicate that N-doping favored the formation of O vacancy (subband levelO119907) which was below the bottom of the conduction band

[42ndash47] Therefore the electrons (eminus) are excited from theN-impurity level bond to the subband level (O

119907) and then

recombine with the hole (h+) as proved in Figure 9 Theholes and electrons react with OHminus and O

2molecules on the

catalyst surface to form ∙OH radicals and O2

minus∙ superoxideanion radicals respectivelyThe protonation yields theHOO∙radicals which after trapping electrons combine to produceH2O2 The O

2

minus∙ radicals then interact with H2O adsorbed to

produce more ∙OH radicals These ∙OH radicals then reactwith gaseous ethylene and mineralize it

TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)

SndashH2O + h+ 997888rarr SndashOH∙ +H+ (2)

SndashOHminus + h+ larrrarr SndashOH∙ (3)

S1015840ndashO2+ eminus 997888rarr S1015840ndashO

2

minus∙ (4)

SndashOH + S1015840ndashO2

minus∙997888rarr SndashHO

2

∙+ S1015840ndashOminus∙ (5)

S1015840ndashO2997888rarr 2S1015840ndashO (6)

S1015840ndashO + eminus 997888rarr S1015840ndashOminus∙ (7)

SndashH2O + S1015840ndashOminus∙ 997888rarr SndashOH∙ + SndashOHminus (8)

SndashHO2

∙+ SndashHO

2

∙997888rarr SndashH

2O2+O2

(9)

SndashH2O2997888rarr 2SndashOH∙ (10)

SndashC2H4+ SndashOH∙ larrrarr SndashC

2H4OH (11)

SndashC2H4OH + S1015840ndashO

2997888rarr intermediates 997888rarr CO

2+H2O(12)

4 Conclusions

The observed changes in the UV-vis DRS XRD and XPSspectra are providing consistent structural information forTindashOndashN formation that is the nitrogen can be incorporatedinto the interstitial positions of TiO

2lattice which leads to

the enhanced photocatalytic activity in N-TiO2samples It

is concluded that the photocatalytic oxidation reactivity ofN-TiO

2under visible light illumination is mainly due to the

presence of localized occupied states caused by interstitialnitrogen and the electronhole pairs generated under visiblelight irradiation It has been found that N dopant retardedthe anatase to rutile phase transformation by forming TindashOndashN incorporated into the interstitial position of TiO

2lattice

Moreover the transformation temperatures of anatase-to-rutile progressively slightly increase when N dopant contentis increased The photocatalyst N-TiO

2prepared with AT

ratio 20 and calcinated at 400∘C shows the highest photo-catalytic activity in the oxidation of ethylene This N-TiO

2

provides an effective visible-light-responsive photocatalystfor future industrial applications in pollution control


Acknowledgment

This research was financially supported by the NationalScience Council of Taiwan ROC under Grant nos NSC-100-2221-E-005-007 and NSC-100-2120-M-005-002

References

[1] T Horikawa M Katoh and T Tomida ldquoPreparation and char-acterization of nitrogen-doped mesoporous titania with highspecific surface areardquo Microporous and Mesoporous Materialsvol 110 no 2-3 pp 397ndash404 2008

[2] K Yang Y Dai and B Huang ldquoStudy of the nitrogen concen-tration influence onN-dopedTiO

2anatase fromfirst-principles

calculationsrdquo Journal of Physical Chemistry C vol 111 no 32 pp12086ndash12090 2007

[3] K Pomoni A Vomvas and C Trapalis ldquoDark conductivity andtransient photoconductivity of nanocrystalline undoped andN-doped TiO

2sol-gel thin filmsrdquoThin Solid Films vol 516 no 6

pp 1271ndash1278 2008[4] S Sato ldquoPhotocatalytic activity of NO

119909-doped TiO

2in the

visible light regionrdquo Chemical Physics Letters vol 123 no 1-2pp 126ndash128 1986

[5] R Asahi T Morikawa T Ohwaki K Aoki and Y TagaldquoVisible-light photocatalysis in nitrogen-doped titaniumoxidesrdquo Science vol 293 no 5528 pp 269ndash271 2001

[6] J Ananpattarachai P Kajitvichyanukul and S Seraphin ldquoVisi-ble light absorption ability and photocatalytic oxidation activityof various interstitial N-doped TiO

2prepared from different

nitrogen dopantsrdquo Journal of Hazardous Materials vol 168 no1 pp 253ndash261 2009

[7] Y T Lin C HWeng and TW Tzeng ldquoPhotocatalysis and cat-alytic properties of nano-sized N-TiO

2catalyst synthesized by

Sol-gel methodsrdquo Journal of Advanced Oxidation Technologiesvol 13 no 3 pp 297ndash304 2010

[8] B Kosowska S Mozia A W Morawski B Grzmil M Janusand K Kałucki ldquoThe preparation of TiO

2-nitrogen doped by

calcination of TiO2sdot xH2O under ammonia atmosphere for

visible light photocatalysisrdquo Solar Energy Materials and SolarCells vol 88 no 3 pp 269ndash280 2005

[9] F Peng L Cai L Huang H Yu and H Wang ldquoPreparationof nitrogen-doped titanium dioxide with visible-light photocat-alytic activity using a facile hydrothermal methodrdquo Journal ofPhysics and Chemistry of Solids vol 69 no 7 pp 1657ndash16642008

[10] H Yu X Zheng Z Yin F Tag B Fang and K HouldquoPreparation of nitrogen-doped TiO

2nanoparticle catalyst and

its catalytic activity under visible lightrdquo Chinese Journal ofChemical Engineering vol 15 no 6 pp 802ndash807 2007

[11] Z Wang W Cai X Hong X Zhao F Xu and C CaildquoPhotocatalytic degradation of phenol in aqueous nitrogen-doped TiO

2suspensions with various light sourcesrdquo Applied

Catalysis B vol 57 no 3 pp 223ndash231 2005[12] A Trenczek-Zajac K Kowalski K Zakrzewska and M

Radecka ldquoNitrogen-doped titanium dioxidemdashcharacterizationof structural and optical propertiesrdquoMaterials ResearchBulletinvol 44 no 7 pp 1547ndash1552 2009

[13] J S Jang H G Kim S M Ji et al ldquoFormation of crystallineTiO2minus119909

N119909and its photocatalytic activityrdquo Journal of Solid State

Chemistry vol 179 no 4 pp 1067ndash1075 2006[14] H L Qin G B Gu and S Liu ldquoPreparation of nitrogen-doped

titania using sol-gel technique and its photocatalytic activityrdquo

Materials Chemistry and Physics vol 112 no 2 pp 346ndash3522008

[15] J Xu Y Ao D Fu andC Yuan J ldquoLow-temperature preparationof anatase titania-coated magnetiterdquo Journal of Physics andChemistry of Solids vol 69 pp 1980ndash1984 2008

[16] DWuM LongW Cai C Chen and YWu ldquoLow temperaturehydrothermal synthesis of N-doped TiO

2photocatalyst with

high visible-light activityrdquo Journal of Alloys andCompounds vol502 no 2 pp 289ndash294 2010

[17] K M Parida and B Naik ldquoSynthesis of mesoporous TiO2minus119909

N119909

spheres by template free homogeneous co-precipitationmethodand their photo-catalytic activity under visible light illumina-tionrdquo Journal of Colloid and Interface Science vol 333 no 1 pp269ndash276 2009

[18] N R Neti R Misra P K Bera R Dhodapkar S Bakardjievaand Z Bastl ldquoSynthesis of c-doped TiO

2nanoparticles by no-

vel sol-gel polycondensation of resorcinol with formaldehydefor visible-light photocatalysisrdquo Synthesis and Reactivity inInorganic Metal-Organic and Nano-Metal Chemistry vol 40no 5 pp 328ndash332 2010

[19] K Bubacz J Choina D Dolat E Borowiak-Palen D Mos-zynski and A W Morawski ldquoStudies on nitrogen modifiedTiO2photocatalyst prepared in different conditionsrdquoMaterials

Research Bulletin vol 45 no 9 pp 1085ndash1091 2010[20] Z Zhang X Wang J Long Q Gu Z Ding and X Fu

ldquoNitrogen-doped titanium dioxide visible light photocatalystspectroscopic identification of photoactive centersrdquo Journal ofCatalysis vol 276 pp 201ndash214 2010

[21] X Z Bu G K Zhang Y Y Gao and Y Q Yang ldquoPrepara-tion and photocatalytic properties of visible light responsiveN-doped TiO

2rectorite compositesrdquo Microporous and Meso-

porous Materials vol 136 no 1ndash3 pp 132ndash137 2010[22] C Liu X Tang C Mo and Z Qiang ldquoCharacterization and

activity of visible-light-driven TiO2photocatalyst codopedwith

nitrogen and ceriumrdquo Journal of Solid State Chemistry vol 181no 4 pp 913ndash919 2008

[23] R Kun S Tarjan AOszko et al ldquoPreparation and characteriza-tion of mesoporous N-doped and sulfuric acid treated anataseTiO2catalysts and their photocatalytic activity under UV and

Vis illuminationrdquo Journal of Solid State Chemistry vol 182 pp3076ndash3084 2009

[24] Z Pap L Baia K Mogyorosi A Dombi A Oszko and VDanciu ldquoCorrelating the visible light photoactivity of N-dopedTiO2with brookite particle size and bridged-nitro surface

speciesrdquo Catalysis Communications vol 17 pp 1ndash7 2012[25] X Z Bu G K Zhang and CH Zhang ldquoEffect of nitrogen dop-

ing on anatase-rutile phase transformation of TiO2rdquo Applied

Surface Science vol 258 pp 7997ndash8001 2012[26] Y P Peng E Yassitepe Y T Yeh I Ruzybayev S I Shah and C

P Huang ldquoPhotoelectrochemical degradation of azo dye overpulsed laser deposited nitrogen-doped TiO

2thin filmrdquo Applied

Catalysis B vol 125 pp 465ndash472 2012[27] H Jie H B Lee K H Chae et al ldquoNitrogen-doped

TiO2nanopowders prepared by chemical vapor synthesis

band structure and photocatalytic activity under visible lightrdquoResearch on Chemical Intermediates vol 38 no 6 pp 1171ndash11802012

[28] S U M Khan M Al-Shahry and W B Ingler ldquoEfficientphotochemical water splitting by a chemically modified n-TiO2rdquo Science vol 297 no 5590 pp 2243ndash2245 2002


[29] X X Wang S Meng X L Zhang H T Wang W Zhong andQ G Du ldquoMulti-type carbon doping of TiO

2photocatalystrdquo

Chemical Physics Letters vol 444 pp 292ndash296 2007[30] N R Khalid E Ahmed Z L Hong Y W Zhang and

M Ahmad ldquoNitrogen doped TiO2nanoparticles decorated

on graphene sheets for photocatalysis applicationsrdquo CurrentApplied Physics vol 12 no 6 pp 1485ndash1492 2012

[31] Q J Xiang J G Yu and M Jaroniec ldquoNitrogen and sulfurco-doped TiO

2nanosheets with exposed 001 facets synthesis

characterization and visible-light photocatalytic activityrdquo Phys-ical Chemistry Chemical Physics vol 13 no 11 pp 4853ndash48612011

[32] J Wang D N Tafen J P Lewis et al ldquoOrigin of photocatalyticactivity of nitrogen-doped TiO

2nanobeltsrdquo Journal of the

American Chemical Society vol 131 pp 12290ndash12297 2009[33] Q Xiang J YuWWang andM Jaroniec ldquoNitrogen self-doped

nanosized TiO2sheets with exposed 001 facets for enhanced

visible-light photocatalytic activityrdquoChemical Communicationsvol 47 no 24 pp 6906ndash6908 2011

[34] Y C Tang X H Huang H Q Yu and L H Tang ldquoNitrogen-doped TiO

2photocatalyst prepared by mechanochemical

method doping mechanisms and visible photoactivity of pol-lutant degradationrdquo International Journal of Photoenergy vol2012 Article ID 960726 10 pages 2012

[35] D E Gu Y Lu B C Yang and Y D Hu ldquoFacile preparationof micro-mesoporous carbon-doped TiO

2photocatalysts with

anatase crystalline walls under template-free conditionrdquo Chem-ical Communications no 21 pp 2453ndash2455 2008

[36] W Ren Z Ai F Jia L Zhang X Fan and Z Zou ldquoLow tem-perature preparation and visible light photocatalytic activity ofmesoporous carbon-doped crystalline TiO

2rdquo Applied Catalysis

B vol 69 no 3-4 pp 138ndash144 2007[37] EM Rockafellow X Fang B G Trewyn K Schmidt-Rohr and

W S Jenks ldquoSolid-state 13C NMR characterization of carbon-modified TiO

2rdquo Chemistry of Materials vol 21 no 7 pp 1187ndash

1197 2009[38] Y Zhang P Xiao X Zhou D Liu B B Garcia and G Cao

ldquoCarbon monoxide annealed TiO2nanotube array electrodes

for efficient biosensor applicationsrdquo Journal of Materials Chem-istry vol 19 no 7 pp 948ndash953 2009

[39] J Yu L Zhang B Cheng andY Su ldquoHydrothermal preparationand photocatalytic activity of hierarchically sponge-like macro-mesoporous Titaniardquo Journal of Physical Chemistry C vol 111no 28 pp 10582ndash10589 2007

[40] J Zhao and X Yang ldquoPhotocatalytic oxidation for indoor airpurification a literature reviewrdquo Building and Environment vol38 no 5 pp 645ndash654 2003

[41] C Di Valentin G Pacchioni and A Selloni ldquoOrigin of thedifferent photoactivity of N-doped anatase and rutile TiO

2rdquo

Physical ReviewB vol 70 no 8 Article ID 085116 4 pages 2004[42] S Livraghi M C Paganini E Giamello A Selloni C

Di Valentin and G Pacchioni ldquoOrigin of photoactivity ofnitrogen-doped titanium dioxide under visible lightrdquo Journal ofthe American Chemical Society vol 128 no 49 pp 15666ndash156712006

[43] X Chen and C Burda ldquoThe electronic origin of the visible-lightabsorption properties of C- N- and S-doped TiO

2nanomateri-

alsrdquo Journal of the American Chemical Society vol 130 no 15pp 5018ndash5019 2008

[44] C Di Valentin G Pacchioni and A Selloni ldquoTheory of carbondoping of titanium dioxiderdquo Chemistry of Materials vol 17 no26 pp 6656ndash6665 2005

[45] HWang and J P Lewis ldquoEffects of dopant states on photoactiv-ity in carbon-dopedTiO

2rdquo Journal of Physics CondensedMatter

vol 17 no 21 pp L209ndashL213 2005[46] H Li D Wang H Fan P Wang T Jiang and T Xie ldquoSynthesis

of highly efficient C-doped TiO2photocatalyst and its photo-

generated charge-transfer propertiesrdquo Journal of Colloid andInterface Science vol 354 no 1 pp 175ndash180 2011

[47] ZWu FDongWZhao and SGuo ldquoVisible light induced elec-tron transfer process over nitrogen doped TiO

2nanocrystals

prepared by oxidation of titaniumnitriderdquo Journal of HazardousMaterials vol 157 no 1 pp 57ndash63 2008

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


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Applied ChemistryJournal of



Theoretical ChemistryJournal of


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Analytical ChemistryInternational Journal of


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Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


absorption activity not only was shifted toward the longervisible wavelength but also had higher thermal stability andless recombination centers of charge carries than the metal-doped TiO

2[5] However to date little research has been

conducted on gaining in-depth information on the propertiesof the interstitial (or substitutional) N-doped TiO

2 as well as

its photocatalytic activity Different dopants result in TiO2of

different properties and consequently alter the photocatalyticactivity of the materials Currently few works have focusedon the synergistic effects of nitrogen dopant and calcinationtemperature on the characteristics and visible-light-inducedphotoactivity of N-doped TiO

2[6]

In this study we focused on sol-gel synthesis process forthe preparation of nitrogen-doped TiO

2catalysts (N-TiO

2)

because the wet processes have the advantages of low costease of scale-up and stablility for practical applications Theeffects of N atom and calcination temperature on the struc-tural optical and photocatalytic properties of N-TiO

2were

assessedThe gel samples were calcined at 400 500 600 700and 800∘C The photocatalysts were characterized using X-ray diffraction (XRD) high-resolution transmission electronmicroscope (HRTEM) X-ray photoelectron spectroscopy(XPS) UV-vis diffusion reflectance spectroscopy (UV-visDRS) Brunauer-Emmett-Teller (BET) specific surface area(119878BET) and thermogravimetric-differential thermal analysis(TG-DTA) The transition from amorphous to anatase andrutile phases at different calcination temperatures was alsoexplored Ethylene was chosen as a probe reactant becauseit is structurally simple has relatively high reactivity and isthe parent compound of many widespread volatile organiccompounds (VOCs) of environmental concern (eg TCE andtetrachloroethylene) The object of this study is to investigatethe synergistic effects of nitrogen content and calcinationtemperatures in the synthesis process of N-doped TiO

2

prepared by sol-gel process and to investigate the influenceof ethylene on photocatalytic decomposition

2 Materials and Methods

21 Preparation of N-Doped TiO2Catalyst Titanium iso-

propoxide (TTIP C12H28O4Ti 97 Aldrich) a highly re-

active alkoxide was used as precursor Aqua ammonia(NH4OH) was used as nitrogen source A given amount of

aqua ammonia was added to the distilled water while beingstirred until it completely dissolved at room temperatureThen the solution was added dropwise to a constant amountof titanium isopropoxide as to obtain an aqua ammoniato TTIP molar ratio (AT) of 1 1 the TiO

2sample was

designated as N-TO2 While the mixture was being stirred

vigorously the urea solution was introduced to the TTIPHydrolysis and ploycondensation reactions occurred Thereactant was stirred continuously for one hour after all aquaammonia solution was dissipated The sol was aged in air for24 hr to allow further hydrolysis The final sol was left on thebench top to allow thickening After aging the sol was driedat 70∘C for 24 hr to evaporate the solventThe residual xerogelwas crushed to fine powder before calcined in a furnace at400 500 600 700 and 800∘C respectively for 3 hr Pure

TiO2powder was also prepared without the presence of aqua

ammonia following the same procedures as described aboveThe nitrogen-doped samples were labeled AxTy where 119909and 119910 refer to the aqua ammonia to TTIP molar ratio (AT)and calcining temperature respectively For example A20T4means the N-TiO

2prepared with AT molar ratio 20 and

calcinated at 400∘C

22 Characterization The 119878BET of the samples was deter-mined using nitrogen adsorption method measured with aMicromeritics ASAP 2020 adsorption apparatus Pore sizeand pore volume were calculated by the BJH isotherm Thecrystallization behavior and stability of N atoms in N-TiO

2

were monitored using a TG-DTA (STA 6000 PerkinElmer)while the sample was being heated from room temperatureto 1000∘C at 10∘CminThe morphology structure and grainsize of the samples were characterized by a high-resolutiontransparent electromicroscopy (HRTEM JEM-2010 JEOL)To study the optical response of N-TiO

2samples (120582 = 200ndash

800 nm) UV-vis DRS (U3900H Hitachi) were recordedusing a spectrophotometer with an integrating sphere attach-ment and Al

2O3was used as the reference The chemical

environment information and the N concentration of all ofthe samples were measured by X-ray photoelectron spectra(XPS) (PHI 5000 VersaProbeScanning ESCA Microprobewith aC

60ion gun) All sampleswere collected in vacuumand

transferred to the main ultrahigh-vacuum (UHV) chamberfor measurements The shift of binding energy due to relativesurface charging was corrected to the C 1s level at 285 eV asan internal standard The XPS peaks were assumed to haveGaussian line shapes and were resolved into components by anonlinear least-squares procedure after proper subtraction ofthe baseline The crystallinity and phase of the samples wereanalyzed byXRD (PANalytical XrsquoPert-ProMPDPW304060)with Cu-Ka radiation at a scan rate of 005∘ 1s in the rangefrom 20 to 80∘

23 Photooxidation Performance The experiment setup andoperating conditions for photocatalytic activity tests werethe same as those reported previously [7] The catalyst wasprepared by depositing suspension of the as-prepared catalystat the bottom surface of the reactor that was subsequentlydried at ambient conditionThe obtained catalyst film densityon the bottom surface of reactor was kept at 4mgcm2 Theexperiment setup and operating conditions for photocat-alytic activity tests were the same as those in our previousreports [7] The photocatalytic activity experiments of theas-prepared catalysts for the oxidation of ethylene in gasphase were performed at room temperature using a 250mLphotocatalytic reactor Air with 60 relative humidity waspassed through the reactor with the sample inside for 1 hrto reach equilibrium and then a desired amount of ethylenewas injected into the reactor with a gastight syringe Theethylene inside the reactor was taken at regular intervals withgas-tight syringe and analyzed using gas chromatographs(PerkinElmer Clarus 500 USA) equipped with a flameionization detector (FID) and a thermal conductivity detector(TCD) detection The GC instrument was equipped with an





119909(OH)119910into TiO







2could prevent

100

80

60

40

20

0

60

50

40

30

20

10

00 100 200 300 400 500 600 700 800

Wei

ght l

oss (

)

Hea

t flow

(mW

mg)

Temperature (∘C)

198 94 17 07

105∘ C

253∘ C

276∘ C

451∘ C

730

∘ C

Anatase into rutile






ammoniaTTIP ratio














2











2crystal phase



A A A

A A

AR

R

RR R R

(101) (110) (004) (204)(200)

(105)(211)

(101)

(111)

(210) (211) (220)

Inte

nsity

(au

)

20 30 40 50 60 70 80


500

600

700

800

2120579 (deg)

AT ratio 2

(a)

A A A A A A(101) (004) (204)(200)(105)(211)

Inte

nsity

(au

)

20 30 40 50 60 70 80

0051

15

2253

2120579 (deg)

AT ratio


P25

(b)










2


2samples can


2


100

80

60

40

20



Ana

tase

()

005115

2253





2photocatalyst


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)







2crystallites and






2






2samples prepared






2





200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





119909(OH)119910into TiO







2could prevent

100

80

60

40

20

0

60

50

40

30

20

10

00 100 200 300 400 500 600 700 800

Wei

ght l

oss (

)

Hea

t flow

(mW

mg)

Temperature (∘C)

198 94 17 07

105∘ C

253∘ C

276∘ C

451∘ C

730

∘ C

Anatase into rutile






ammoniaTTIP ratio














2











2crystal phase



A A A

A A

AR

R

RR R R

(101) (110) (004) (204)(200)

(105)(211)

(101)

(111)

(210) (211) (220)

Inte

nsity

(au

)

20 30 40 50 60 70 80


500

600

700

800

2120579 (deg)

AT ratio 2

(a)

A A A A A A(101) (004) (204)(200)(105)(211)

Inte

nsity

(au

)

20 30 40 50 60 70 80

0051

15

2253

2120579 (deg)

AT ratio


P25

(b)










2


2samples can


2


100

80

60

40

20



Ana

tase

()

005115

2253





2photocatalyst


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)







2crystallites and






2






2samples prepared






2





200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of








2crystal phase



A A A

A A

AR

R

RR R R

(101) (110) (004) (204)(200)

(105)(211)

(101)

(111)

(210) (211) (220)

Inte

nsity

(au

)

20 30 40 50 60 70 80


500

600

700

800

2120579 (deg)

AT ratio 2

(a)

A A A A A A(101) (004) (204)(200)(105)(211)

Inte

nsity

(au

)

20 30 40 50 60 70 80

0051

15

2253

2120579 (deg)

AT ratio


P25

(b)










2


2samples can


2


100

80

60

40

20



Ana

tase

()

005115

2253





2photocatalyst


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)







2crystallites and






2






2samples prepared






2





200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


A A A

A A

AR

R

RR R R

(101) (110) (004) (204)(200)

(105)(211)

(101)

(111)

(210) (211) (220)

Inte

nsity

(au

)

20 30 40 50 60 70 80


500

600

700

800

2120579 (deg)

AT ratio 2

(a)

A A A A A A(101) (004) (204)(200)(105)(211)

Inte

nsity

(au

)

20 30 40 50 60 70 80

0051

15

2253

2120579 (deg)

AT ratio


P25

(b)










2


2samples can


2


100

80

60

40

20



Ana

tase

()

005115

2253





2photocatalyst


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)







2crystallites and






2






2samples prepared






2





200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


400∘C

10nm

(a)

500∘C

10nm

(b)

600∘C

50nm

(c)

700∘C

50nm

(d)

100nm

800∘C

(e) (f)







2crystallites and






2






2samples prepared






2





200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


200

150

100

50

00 02 04 06 08 1

400500600

700800

IV

IV

V

VV


Qua

ntity

adso

rbed

(cm

3g

STP

)


(a)

0 02 04 06 08 1

005115

2253

IV

250

200

150

100

50

0

H3


Qua

ntity

adso

rbed

(cm

3g

STP

)


(b)

0

120

100

80

60

40

20

0400 500 600 700 800


Surfa

ce ar

ea (m

2g

)

05115

2253

AmmoniaTTIP ratio

(c)




2were decreased due













400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


400500600

700800

2

15

1

05

0

Abso

rban

ce (a

u)

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)


05

04

03

02

01

0350 400 450 500 550


AT ratio 2


P25

(a)

2

15

1

05

0

Abso

rban

ce (a

u)

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce (a

u)

Wavelength (nm)

04

04

03

03

02

02

01

01380 400 420 440 460 480 500 520 540


325

215

1050P25


A20T4A25T4A30T4

AT ratio


(b)























1198922





119892) was






2 To investigate







2lattice





Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Bind energy (eV)

Inte

nsity

(au

)800

700

600

500

400


390 395 400 405 410

AT ratio 2

(a)

Bind energy (eV)

Inte

nsity

(au

)


325

2

15

1

05

0

Ti-O-N

390 395 400 405 410

AT ratio

(b)

Bind energy (eV)

Inte

nsity

(au

) 800

700

600

500

400


Ti-O

524 526 528 530 532 534 536

AT ratio 2

(c)

Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti-O

524 526 528 530 532 534 536

AT ratio

(d)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)

4582

4581

4583

458

4583

800

700

600

500

400


Ti4+2p12

(e)

454 456 458 460 462 464 466 468Bind energy (eV)

Inte

nsity

(au

)


3

25

2

15

1

05

0

Ti4+2p32

Ti4+2p12 AT ratio

(f)












32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




32and Ti 2p

12of TiO

2(data not


and Ti 2p32


12are symmetry



2and


and Ti 2p32


2crystal lattice


2






2


2











50

40

30

20

10

00 05 1 15 2 25 3


Rem

oval

effici

ency

()

Calcination temp

400∘C

500∘C

800∘C




2O]= 25060 ppmv


= 3 h


2at different


2in all mea-





2was modified by


2catalysts in the





32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


32 eVCO2 + H2O

IntermediatesH2O

OH∙ C2H4


TiIV OH

TiIV OH

O2

∙O2minus

∙HOO H2O2

TiIV OH+∙

CB

VBh+ NS

OV


illumination

















O2


2



119907) and then


2molecules on the



2



TiO2

h120592997888997888997888997888997888rarr h+ + eminus (1)




2

minus∙ (4)



2





SndashHO2

∙+ SndashHO

2


2O2+O2

(9)



2H4OH (11)



2+H2O(12)

4 Conclusions







2lattice


2prepared with AT


2



Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Acknowledgment


References








119909-doped TiO

2in the










2-nitrogen doped by


















2photocatalyst with



N119909



























2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



2photocatalystrdquo





























2rdquo




2nanomateri-









2nanocrystals











Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article the synergistic effect of nitrogen dopant and...

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