hien nguyen msthesisppt_150521
TRANSCRIPT
Synthesis, Characterization and Catalytic Activity of Ru-N-C Hy-brid Nanocomposite for Ammonia Dehydrogenation
Thesis for the Degree of Master
Nguyen Thi Bich Hien
Advisor: Dr. Chang Won Yoon
Fuel cell Research Center,Korea Institute of Science and Technology,
Clean Energy and Chemical Engineering Korea University of Science and Technology,
May 21, 2015
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Contents
Introduction and research objectives
Experimental
Results and discussion
Conclusions
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2
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1Introduction
Contents
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IntroductionIntroduction: Hydrogen as a future energy carrier
Searching for renewable energiesSolar
energy
Biomass en-ergy
Wind energy
Geother-mal en-
ergy
Hydro-gen en-ergy
Exhaust of fossil fuel & environmental hazards
http://www.britannica.com/
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Introduction: Why hydrogen storage important?
Methane
Wind
Solar
Electrolysis
Reformer
Water
Oxygen
HydrogenStorage
Hydrogen
Fuel cell
Hydrogen production
Hydrogen utilization
Hydrogen Economy
Hydrogen Economy Hydrogen
storage
Renewables energy
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Introduction: Hydrogen Storage Technology
Hydrogen storage
Physical-based Chemical-based
Com-pressed-
GasLiquid
Cryo-ad-sorption
Metal hy-drides
Chemical hydrides
NH3NH3BH3 HCOOH CH3OH etc.
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Introduction: Ammonia as hydrogen career
Dehydrogenation
High hydrogen density (17.8wt%)
Carbon-free chemical energy
Developed technology for synthesis (Haber-Bosch process)
Solid ammine complexes
The capital and operating cost of the NH3 facility cheaper than H2 (20.2 M$ & 63.2 M$, respectively).
7J. Mater. Chem., 2008, 18, 2304–2310
NH3 Dehydrogenation Requires “Catalysts”
Thermodynamically, 98-99% conversion of ammonia to hydrogen is possible at temperatures as low as 425 °C.
2NH3 3H2 + N2 H △ = 46kJ/mol Ammonia decomposi-
tion
It is necessary to develop the catalyst for ammonia dehydrogenation 8
450 475 500 525 550
0
20
40
60
80
100
Temperature (oC)
NH
3 c
onve
rsio
n (%
)
No catalyst
Literature Precedents: Controlling Factors
2NH3 3H2 + N2 H △ = 46kJ/mol Ammonia decomposi-
tion
(1) Influence of Metals:
Ru
Ru > Rh > Ni > Pd Pt > Fe≒
RhNiPd, Pt
S.F. Yin et al., Appl. Catal. A 277 (2004) 1-9S.F. Yin et al., Appl. Catal. 244 (2004) 384-396
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Literature Precedents: Controlling Factors
2NH3 3H2 + N2 H △ = 46kJ/mol Ammonia decomposi-
tion
(2) Influence of Supports:
J. Mater. Chem. A, 2014, 2, 9185–919210
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Rate Determining Step (recombinative desorption of N)
Literature Precedents: Controlling Factors
Chem. Chem. Phys., 2011, 13, 12892–12899 Lee, J.H at all, Inorg. Chim. Acta 2014, 422, 3-7.
Increase electron den-sities of metal
N, K doping ba-sic support
Enhance recombinative desorption of N
(3) Influence of Dopant:
Schematic diagram of synthetic proce-dure of Fe–N–C
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Catalyst Design: “Ru-N-C Hybrid Materials”
Metal : Ru – highly activity for ammonia decomposition
Support : black C sphere – cheap & high surface areas
Promoter : N – increase electron density of metal
N-doped Carbon as supports
Ru
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2 Experimental
Contents
▪ Preparation Catalyst
▪ Reaction design
Experimental – Preparation of catalyst
1 Gram
black C RuCl3.xH20
0.25 Gram
dicyanamide
1 Gram
20 ml H2O
100oC4h
550oC, 4 h in N2ICP
Ru-N-C
0.97 wt%
Ru-C 0.88 wt%
Ru3+ chelated composites
Ru-N-C nanocomposite
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NC RuC RuCN
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Reaction conditionsCatalyst : 100mg, Reduction : 50% H2/N2, 550 , 1h; NH℃ 3 purity :10%, flow rate : 37 mL/min, Temp. : 400 - 550℃ ℃
2NH3 3H2 + N2 H △ = 46kJ/mol Ammonia decomposi-
tion
Experimental – Ammonia cracking process
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Contents
Results & Discussion
▪ Characterization results
▪ Catalytic activity
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Ru-N-C
a
b
aCharacterization: Morphological analysis
17N-containing helped metal dispersion
5nm
20 nm
Hollow graphitized structure
Aggregation Ru
Ru-C
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TEM image & EDX spectrum of Ru-N-C and elements mapping
Characterization: Morphological analysis
Ru, C, and N were well dispersed over the catalyst 18
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25.2°: Carbon sphere
Characterization: XRD
Scherrer equation
Ru particles size (nm)
Ru-N-C 1.3
Ru-C 5.1 19
101
002
Ru
102
110 10
3210
002
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BET surface area, pore size, pore volume of the Ru-based catalysts
Catalyst
BET Surface
Areaa
(m2g-1)
Pore Sizea
(nm)
Pore Volumea
(cm3g-1)
Ru-N-C 898 4.7 1.05
Ru-C 1,110 5.4 1.57 aDetermined by physical adsorption using N2
Surface area of Ru-N-C smaller than Ru-CA slight reduction of the pore size and pore volume in Ru-N-C
Characterization: Textural Properties
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Graphitic
C-O
Graphitic
C(sp2)-N
C(sp3)-N
NitrilePyrrolic
Pyridinic
Characterization: XPS analysis (C1s & N1s)Ru-C
390 400 410
1680
1700
1720
1740
1760
1780
Binding energy (eV)
Inte
nsi
ty (
a.u
.)
N1s
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Ru-N-C
N atoms were introduced into the graphitic structure upon pyrolysis.
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Ru-C
Ru-N-C
Ru 3d
Ru 3d
Characterization: XPS analysis (Ru3p & Ru3d)
Ru-N-C
Ru-C
RuO2
RuO2·xH2O
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RuO2
RuO2·xH2O
Ru-N-C appeared at lower binding energy compared to that of Ru-C the incorporated nitrogen atoms donated electron density into the Ru active sites.
281.1
280.9
23 The activity of Ru-N-C > Ru-C> N-C
Catalytic activity: Influence of temperatureNH3 conversion
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95%GHSV: 7,448 mLg-1h-1
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GHSV 400 oC 450 oC 500 oC 550 oC
2,234 0 44.7 97.7 99.7
4,469 0 27.8 86.8 99.2
7,448 0 0 55.9 94.5
11,172 0 0 31.2 81.5
Catalytic activity: Influence of GHSV & Temp .
500 oC
450 oC
400 oC
550 oC
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GHSV (mLg-1h-1)
NH3 conversion of Ru-N-C increased as GHSV decreased H2 release properties improved as temperature increased
99.7%
81.5%
500 oC; GHSV = 7.448 mLg-1h-1
79%
61%
36% 19%
Catalytic activity: Long-Term Stability
Initially, NH3 conversion started at 79% for Ru-N-C and 19% for Ru-C, a significant difference by 60%.
After 80h, Ru-N-C slightly decreased by 18% while Ru-C increase by 20% Hypothesis: The reactant NH3 acted as a N-doping agent in Ru-C
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HAADF STEM images of Ru-C following the long-tem sta-bility test for 80 h and elemental mapping
Post-analysis of the spent-catalyst:
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Nitrogen0.82wt%
The reactant NH3 acted as a N-doping agent in Ru-C
b) c)
Post-analysis of the spent-catalyst: Continued
Ru-N-C
Fresh
a)
b) c)
d)
Ru-C
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Fresh after reaction for 80 h
Fresh after reaction for 80 h
The graphitic hollow structure are stable during long term reaction. Ruthenium particles in Ru-N-C slightly agglomerated even after 80 hours.
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The improved activity for H2-release from NH3 over Ru-N-C may originate from the incorporation of N species that contributed to:
• The formation of the small-sized Ru nanoparticles by initially anchoring the Ru3+ precursor to prevent them from sintering
• Enhancing the thermal stability of the catalyst
• Increasing the Ru electron density induced by the interaction between Ru & N
Summary
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Contents
Conclusions3
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• The simple synthetic strategy presented herein provides an economical route for large-scale production of the highly active Ru-N-C catalyst.
• The Ru-N-C catalyst displayed excellent performance for NH3 dehydrogenation with high stability.
• The incorporated nitrogen atoms were proposed to play pivotal roles in: Generating uniformly distributed, small-sized Ru nanoparticles. Improving the thermal stability of the catalyst. Donating electron density to Ru via electronic interactions between Ru and N.
The as-developed Ru-N-C hybrid nanocomposite is thus applicable for on-site hy-drogen production from ammonia with relevant catalyst optimization, and further provides insight for the development of various M-N-C catalysts (M = transition metals) for a number of chemical transformations.
Conclusions
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ACKNOWLEDGEMENTThanks to:Advisor: Prof. Yoon Chang Won
Committee members:Prof. Ham Hyung ChulProf. Kim Jin Young
All group members current and past, friends and family:Dr. Kim Young Jeon, Dr. Park Nan Hee, Dr. Lee Jin Hee, Dr. Jeon Mina, Muhammad Ridwan, Kim Hyo Young.
All of our laboratory’s facilities: stations, chemicals,…
For their help and support me during my re-search period in the past 2 years! 30
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Contents
BACKUP SLIDES4
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Benefits of hollow carbon doped N
Hollow nanostructures: Low density High surface-to-volume ration Shell permeability
Hollow carbon nanospheres: Cheap, nontoxic Good chemical stability Good Electrical conductivity- chemical inertness
Carbon nanomaterials with nitrogen: Increase the surface polarity Enhance electrical conductivity & surface basic sites and electron- donor tendency of the carbon matrix
Chem. Commun., 2014, 50, 329
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• Pyridinic N bonds with two C atoms at the edges or defects of graphene and contributes one p electron to the π system; sp2 hybridized
Lowest barrier for electron transfer; coordinate with transition metals.
• Pyrrolic N refers to N atoms that contribute two p electrons to the π system; sp3 hybridized
Nitrogen bonding configurations
Journal of Catalysis 239 (2006) 83–96
ACS Catal. 2012, 2, 781−794
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Ru-N-C indicated reasonable stability up to 500 °C while the decomposition of Ru-C was initiated at 380 °C
The TGA pattern of Ru-C-N and Ru-C.
Characterization: Thermal stability
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380 °C
500 °C
heat 10 °C/min, un-der N2
0 200 400 600 8000
20
40
60
80
100W
eigh
t los
s (%
)
Temperature (oC)
FWHM of D band
FWHM of G band
ID/IG
Ru-C 157.8 100.5 1.15
Ru-C-N 190.1 109.3 1.09
Result & Discussion RAMAN
The ID/IG values of N-C support < C a more graphitic structure & increase the ratio of sp2 to sp3 bonds.
Increase FWHM of D peak increase defect due to N doped on carbon
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Dicyandiamide, 5g +H3B─NH3, 0.25g
+Carbon black, 5g
+RuCl3.xH2O, 0.25g
1) Oil bath 80oC, 6h
2) 550oC, N2
Ru-N-B-C
1) Oil bath 80oC, 6h
2) 550oC, N2
N-B-C
N-B-C, 1g
Y. Wang et al. Chem. Sci. 2011, 2, 446-450.
+ Boron
J. Mater. Chem. A, 2014, 2, 16645–16651
Synthesis of Boron Nitrogen co-doped carbon
RESEARCH PLAN
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BmimPF6, 0.50g
Dicyandiamide, 5g +
+Carbon black, 5g
Y. Zhang et al. J. Am. Chem. Soc. 2010, 132, 6294-6295.
+RuCl3.xH2O, 0.25g
1) Oil bath 80oC, 6h
2) 550oC, N2
Ru-N-P-C
N-P-C, 1g
1) Oil bath 80oC, 6h
2) 550oC, N2
N-P-C
Synthesis of Doped Ru-NP-C
RESEARCH PLAN