material katalis dan fotokatalis (mkf) 1
TRANSCRIPT
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Material Katalis dan Fotokatalis (MKF)
• Material Katalis• Material Fotokatalis
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SILABI MATERIAL KATALIS DAN FOTOKATALIS ( MKF )
1. Sejarah dan Perkembangan Material Katalis 2. Konsep Dasar Reaksi Katalisasi 3. Material Katalis Homogen dan Heterogen : Reaksi, Desain Sintesis,
Karakterisasi dan Uji Unjuk Kerja Katalis4. Sejarah dan Perkembangan Material Fotokatalis 5. Sintesis dan Karakterisasi Material Fotokatalis6. Aplikasi Material Fotoaktif : Fotokatalisasi oksidasi dan reduksi serta
Unjuk kerja, Fotokatalis dalam sistem Fotovoltaik dan Unjuk Kerja7. Perkembangan terkini sintesis material fotokatalis : material
responsif cahaya tampak, material core-shell, material nanostruktur (nanorod,nanotube,nanowire)
Prasyarat : KIMIA DASAR SEMESTER GENAPDosen Pengasuh : Prof Dr Wega Trisunaryati
Dr Indriana KartiniDr. Akhmad S
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HETEROGENEOUS CATALYSTS
• Solid catalyst• Photocatalysis by semiconductor
materials
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• A CATALYST is a substance that increases the rate at which a chemical reaction approaches equilibrium, while not being consumed in the process – kinetic aspect
• catalyst provides alternative reaction mechanism of lower activation energy
• materials used: insoluble, nonvolatile solid as catalyst
• important properties:– activity– selectivity
• advantages of using solid catalyst in a fluid-phase reaction – heterogeneous catalyst :– minimal lost of the catalyst– minimal contamination of the reaction products– stay physically in place of the reaction chambers
• Heterogeneous catalysis of a reaction between two molecules can occur only when both molecules are adsorbed on to a solid surface
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Photocatalysis
Photocatalyst
Starch + O2
Organic compound
Chlorophyll
CO2
H2O
CO2 + H2O
Organic Compound
+ H2O + O2
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Photocatalytic Applications
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Antimicrobial Effect
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Antimicrobial Effect
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Self-Cleaning Effect
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When water hit surfaces
Hydrophilic surface=wetting
Water spreads
Hydrophobic surface= beading
Water beads
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Contact angle differences
Contact angles below 90 indicate good wetting, while contact angles above 90 indicate poor wetting (beading).
Poor wetting (beading)Contact angle > 90°
Good wetting Contact angle < 90°
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THE LOTUS LEAF EFFECT
The leaves of Lotus plants have the unique ability to avoid getting dirty.They are coated with wax crystals around 1 nanometre in diameter and have a special rough surface.Droplets falling onto the leaves form beads and roll off taking dirt with them, meaning the leaves are self-cleaning.Sometimes referred to as“The Lotus Leaf effect”
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SELF CLEANING GLASS
Scientists have mimicked nature at the nanoscale to create glass surfaces that are ‘self-cleaning’ like the Lotus leaf.
No more scrubbing of shower screens!
Self cleaning glass Normal glass
No more Spiderman window cleaner!
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SELF CLEANING GLASS
HOW DOES IT WORK?
Glass is coated with a layer of nanocrystalline titanium dioxide (TiO2). The titanium dioxide reacts to the ultraviolet (UV) component of sunlight causing a gradual break down and loosening of dirt. This isknown as the ‘photocatalytic’ stage.
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SELF CLEANING GLASS
HOW DOES IT WORK?
The reaction also causes the glass surface to become super hydrophilic. This forces water to spread across the surface like a sheet, rather than beading, thereby washing away the looseneddebris on the surface ofThe glass as it falls.This is the ‘hydrophilic’ stage.
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SELF CLEANING GLASS
HOW DOES IT WORK?
• Another type of self cleaning glass uses hydrophobicity, not hydrophilicity.
• This type of glass is given a coating which makes it super hydrophobic, meaning water forms beads and runs of the glass.
• This type of glass is used indoors, such as in shower screens, where there is no sunlight enable use of the other type of glass.
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Photocatalysts
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Vacuum level
-3.0
-4.0
-5.0
-6.0
-7.0
-8.0
0
-4.5
TiO2
Rutile
3.0
TiO2
Anatase
3.2
SrTiO3
3.2
FeTiO3
2.7
2.8
MnTiO3
3.2
ZrO2
BaTiO3
5.0
Nb2O5
3.4
3.4
KTaO3WO3
2.8
2.2
ZnO2
3.2
Fe2O3
SnO23.
8
GaP
2.3
1.1
Si
SiC
3.0
CdSe
CdS
1.7
2.5
E vs. NHE
@ pH = 0
H+/H2
-1.0
+2.0
+1.0
+3.0
0
Band Gap Positions in Various Semiconductors
eV
O2/H+
Upper edge position of VB
Lower edge position of CB
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Mechanism of photocatalysis
+
+
B
B+
-
-
A
A-
h
CB
VBh+
e-
hv
+ +Volume recombination
++
surface recombination
photogenerated hole – highly oxidizing
O2
O2-, H2O2
H2O2, OH-, R
OH● , R+
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Why TiO2?
1 n-type TiO2 electrode 2 platinum black counter electrode
3 ionically conducting separator 4 gas buret
5 load resistance 6 voltmeter
Fujishima A.Honda K.,Nature, 1972, 37(1):238-
245.
• Good photoactivity (band gap=3.2ev) oxidation of most VOC & water (Strong oxidizing power)• High Photo & chemical stability, non-toxicity• Low cost, ease of availability, can be reused• Photocatalysis takes place at ambient temperature• Atmospheric oxygen is used for the reaction
Photocatalysis goes to TiO2 era
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Redox potential of h+
1. The redox potential for photogenerated h+ is +2.53 V vs. the
SHE
2. After reaction with water, these h+ can produce •OH
3. Both h+ and •OH are more positive compare to ozone
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Introduction: Photocatalytic Process
Photo-generation
electron/hole pairs
Formation of radicals
Radical oxidation of organic
compound.
TiO 2 hv
e- + h+
h+ + H 2O OH + H+
e- + O 2 O2-
O2- + H+ HO 2
TOC + Ox TOC(partially oxidized species) + CO2 + H 2O
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Photocatalytic ReactionsTiO2 + h TiO2 (e- + h+)
h+ + H2O OH + H+
O2 + e- O2 -
O2 - + H+ HO2
HO2 + HO2 H2O2 + O2
O2 - HO2+
H2O2
O2 + HO2-
HO2- +
H2O2 + h OH2
H2O2 + O2 - HO + OH- + O2
H2O2 + e-HO + OH-
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The applications of TiO2 is a function of specific physicochemical properties
like:
– High Surface area
– Small Crystalline Size
– Anatase form of TiO2
– High crystallinity
– Porous structure
– Activation light source
An appropriate synthetic procedure can provide TiO2 with promising
efficiency
Entail Physicochemical Properties of TiO2
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Challenge of TiO2!!!
Because TiO2 has a high band gap (~ 3.2 eV), it is excited only by UV light (λ <388 nm) to inject electrons into the conduction band. Thus, this limits the use of sunlight (3~5%) or visible light as an irradiation source in photocatalytic reactions on TiO2 .
In addition, the high rate of electron–hole recombination on TiO2 particles results in a low efficiency of photocatalysis
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next will be on:fundamental concepts for
photocatalyst material