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1
Surface science & catalysis group
Cardiff Catalysis Institute
XPS, AFM & DFT studies of the
functionalization of graphit...
2
Motivation
• Graphene based sensors
• Intracellular nanodiamond sensors
• Carbon catalyst supports
3
1. Washing:
• HCl, HNO3,
Aqua Regia (HCl & HNO3)
2. Impregnation
• HAuCl4, H2PdCl4 etc
in H2O, HCl, HNO3,
Aqua Regia
3. ...
4
Direct synthesis of H2O2
“Switching Off Hydrogen Peroxide Hydrogenation in
the Direct Synthesis Process.”
Edwards, Hutch...
5
………….oxygen surface groups affect not only the preparation, but also
influence the resistance to sintering and the catal...
6
Strategy
1. Washing:
• HCl, HNO3,
Aqua Regia (HCl & HNO3)
2. Impregnation
• HAuCl4, H2PdCl4 etc
in H2O, HCl, HNO3,
Aqua ...
7
Strategy II
Catalyst
• Carbon powder
• Preparation in air
• Deposition from solution
HOPG
Highly ordered
pyrolytic graph...
8
AFM image of HCl treated HOPG
Clean HOPG surface
9
Local delamination
Bouleghlimat et al. Carbon, 2013, 61, 124–133.
HCl
• What are the oxygen states?
• How do they affect...
10
Functional Group Identification
through Chemically Specific Derivitisation
D. S. Everhart and C. N. Reilley, Anal. Chem...
11
Molecule specific labeling:
Is OH(a) present?
679684689694699
Binding energy /eV
688.8
(d) HCl/573 K
& TFAA
(c) HCl/TFA...
12
Is –CO2H present?
679684689694699
Binding energy /eV
F(1s)
(a) Clean/TFE
(b) HCl/TFE
(c) HCl/573 K
& TFE
688.4
-CO2H
No...
13
527532537542
Binding energy /eV
O(1s)O(1s)O(1s)
(a) Clean
(b) HCl
(c) HCl/573K
531.5
O(1s)
533.3
680685690
688.4
F(1s)
...
14
Conclusions: 1
• Acid treatment of HOPG surfaces leads to local
delamination through functionalisation at
defects.
• HC...
15
Gold deposition
78838893
Binding energy /eV
Au(4f)
84.086.5
(a) Clean
(b) HCl /Au
(c) HCl /573 K
& Au
84.9
HOPG
OH(a)
1...
16
AFM images of nanoparticles
deposited on HOPG from HAuCl4(aq)
HOPG
Untreated
HNO3
treated
HNO3
treated and heated
to 57...
17
The stabilisation of gold by different
functional groups: DFT
Adsorption of Au atom in vicinity of:
OH functionalised e...
18
Increasing HCl concentration:
effect on Gold deposition
• Acid treatment increases HOPG
hydrophobicity!
• Drying time d...
19
Conclusions
• Acid treatment of HOPG surfaces leads to local delamination
through functionalisation at defects.
• HCl &...
20
Surface science & catalysis group
Cardiff Catalysis Institute
Gold 2015
7th International Gold Conference
26th – 29th J...
21
Comparison of HCl and HNO3:
Effect of acid concentration II
0.5 M HCl
10 M HCl
10 M
0.5 M
x10
22
Clean HOPG surface
Deionised water
Control experiments
Ultra pure water
23
Models to account for the features
24
XPS
HNO3
HCl
Clean
HNO3
HCl
Clean
25
HNO3
HCl
HNO3
HCl
XPS
• No Ca, K, Na
• Maximum O(a) ~ 4% monolayer
26
Models to account for the features
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2015 01-8 pr davies spectroscopic and afm studies of the functionalisation of carbon

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Presentation at the first UK catalysis conference held in Loughborough on 8th January 2015.

Published in: Science
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2015 01-8 pr davies spectroscopic and afm studies of the functionalisation of carbon

  1. 1. 1 Surface science & catalysis group Cardiff Catalysis Institute XPS, AFM & DFT studies of the functionalization of graphite surfaces Philip R. Davies Cardiff Catalysis Institute School of Chemistry, Cardiff University Cardiff EP/I038748/1 EP/L000202 David J. Morgan Robert J. Davies, Thomas Jones, Jiří Kulhavý, Ryan Lewis Vaughan Roberts, Amy Lai Theory David J. Willock Carlo Buono Neil Robinson, Experimental Rebecca Burgess Thomas Legge
  2. 2. 2 Motivation • Graphene based sensors • Intracellular nanodiamond sensors • Carbon catalyst supports
  3. 3. 3 1. Washing: • HCl, HNO3, Aqua Regia (HCl & HNO3) 2. Impregnation • HAuCl4, H2PdCl4 etc in H2O, HCl, HNO3, Aqua Regia 3. Drying • 290 oC - 200 oC Preparation of carbon supported metals
  4. 4. 4 Direct synthesis of H2O2 “Switching Off Hydrogen Peroxide Hydrogenation in the Direct Synthesis Process.” Edwards, Hutchings et al. Science 323 (2009) 1037 Table 2. Activity and selectivity of pretreated and untreated carbon-supported catalysts
  5. 5. 5 ………….oxygen surface groups affect not only the preparation, but also influence the resistance to sintering and the catalytic activity of the catalyst. Abstract “The role of carbon materials in heterogeneous catalysis” Francisco Rodriguez-Reinoso, Carbon 1998, 36, 159 “Working with a vacuum, not in one!” Bob Madix, ACS meeting Literature
  6. 6. 6 Strategy 1. Washing: • HCl, HNO3, Aqua Regia (HCl & HNO3) 2. Impregnation • HAuCl4, H2PdCl4 etc in H2O, HCl, HNO3, Aqua Regia 3. Drying • 290 oC - 200 oC Preparation of carbon supported metals Our study must be: • Relevant. • Minimum parameters
  7. 7. 7 Strategy II Catalyst • Carbon powder • Preparation in air • Deposition from solution HOPG Highly ordered pyrolytic graphite Surface Science • Graphite crystal • UHV • Vapour deposition • Surface science tools HOPG “Bench top” surface science • Graphite crystal • Preparation in air • Deposition from solution • Surface science tools
  8. 8. 8 AFM image of HCl treated HOPG Clean HOPG surface
  9. 9. 9 Local delamination Bouleghlimat et al. Carbon, 2013, 61, 124–133. HCl • What are the oxygen states? • How do they affect carbon-metal interactions? • Local delamination • Heating to 573 K removes “bubbles”. 527532537542 Binding energy /eV O(1s)O(1s)O(1s) (a) Clean (b) HCl (c) HCl/573K 531.5 O(1s) 533.3 532.7 XPS data: • One oxygen state, Two states heated to 573 K
  10. 10. 10 Functional Group Identification through Chemically Specific Derivitisation D. S. Everhart and C. N. Reilley, Anal. Chem., 1981, 53, 665–676. C. D. Batich, Appl. Surf. Sci., 1988, 32, 57–73. OH(a) + CF3C(O)OC(O)CF3 (g)  CF3C(O)O-(a) + CF3CO2H(g) -OH groups -CO2H groups -CO2H(a) + CF3CH2OH(g)  CF3C(OH)O-(a) + H2O(g) -C=O groups -CO(a) + CF3CH2NH-NH2 (g)  CF3CH2NH-N=(a) + H2O(g)
  11. 11. 11 Molecule specific labeling: Is OH(a) present? 679684689694699 Binding energy /eV 688.8 (d) HCl/573 K & TFAA (c) HCl/TFAA (a) Clean/TFAA F(1s) OH(a) + CF3C(O)OC(O)CF3 (g)  CF3C(O)O-(a) + CF3CO2H(g) OH(a) 532.7 eV 527532537542 Binding energy /eV O(1s)O(1s)O(1s) (a) Clean (b) HCl (c) HCl/573K 531.5 O(1s) 533.3 HCl & HNO3
  12. 12. 12 Is –CO2H present? 679684689694699 Binding energy /eV F(1s) (a) Clean/TFE (b) HCl/TFE (c) HCl/573 K & TFE 688.4 -CO2H Not significant -CO2H(a) + CF3CH2OH(g)  CF3C(OH)O-(a) + H2O(g) 527532537542 Binding energy /eV O(1s)O(1s)O(1s) (a) Clean (b) HCl (c) HCl/573K 531.5 O(1s) 533.3
  13. 13. 13 527532537542 Binding energy /eV O(1s)O(1s)O(1s) (a) Clean (b) HCl (c) HCl/573K 531.5 O(1s) 533.3 680685690 688.4 F(1s) (a) (d) (c) Binding energy /eV Clean HCl /TFH HCl /573 K /TFH -CO(a) + CF3CH2NH-NH2 (g)  CF3CH2NH-N=(a) + H2O(g) C=O(a) 531.5 eV OH(a) 532.6 eV -C-O-C-(a) 533.3 eV Is C=O present?
  14. 14. 14 Conclusions: 1 • Acid treatment of HOPG surfaces leads to local delamination through functionalisation at defects. • HCl & HNO3 treatment of HOPG gives exclusively OH(a) covered surfaces • Heating to 573 K converts OH(a) to C=O & C-O-C groups E. Bouleghlimat et al., Carbon, 2013, 61, 124–133 C. Buono et al, Faraday Discuss., 2014, 173 257–272
  15. 15. 15 Gold deposition 78838893 Binding energy /eV Au(4f) 84.086.5 (a) Clean (b) HCl /Au (c) HCl /573 K & Au 84.9 HOPG OH(a) 195200205 Binding energy /eV Cl(2p) (a) (b) (c) 198.0 199.7 Au0 Au3+ C. Buono et al, Faraday Discuss., 2014, 173 257–272 R. Burgess et al. J. Catalysis, 2015, DOI: 10.1016/j.jcat.2014.12.021 C=O C-O-C
  16. 16. 16 AFM images of nanoparticles deposited on HOPG from HAuCl4(aq) HOPG Untreated HNO3 treated HNO3 treated and heated to 573 K
  17. 17. 17 The stabilisation of gold by different functional groups: DFT Adsorption of Au atom in vicinity of: OH functionalised edge = ~ -1.27 eV C=O functionalised edge = ~ -0.77 eV OH functionalised step CO functionalised step Flexibility of OH groups allows additional bonding.
  18. 18. 18 Increasing HCl concentration: effect on Gold deposition • Acid treatment increases HOPG hydrophobicity! • Drying time decreased  Gold deposition decreased. • OH increases nucleation rate • OH increases extent of Au3+ reduction 80.0084.0088.0092.00 Binding Energy /eV Au4f Auo Au3+ Au+ 0.25 M 0.5 M 5.0 M 1.0 M Clean
  19. 19. 19 Conclusions • Acid treatment of HOPG surfaces leads to local delamination through functionalisation at defects. • HCl & HNO3 treatment of HOPG gives exclusively OH(a) • Heating to 573 K converts OH(a) to C=O & C-O-C groups • Gold nucleation is more rapid on OH(a) covered surfaces. • Stabilisation of Au on OH(a) is stronger than on C=O covered surfaces because of multiple interactions E. Bouleghlimat et al., Carbon, 2013, 61, 124–133 C. Buono et al, Faraday Discuss., 2014, 173 257–272 R. Burgess et al. J. Catalysis, 2015, DOI: 10.1016/j.jcat.2014.12.021
  20. 20. 20 Surface science & catalysis group Cardiff Catalysis Institute Gold 2015 7th International Gold Conference 26th – 29th July 2015 in Cardiff, UK www.cardiff.ac.uk/gold2015
  21. 21. 21 Comparison of HCl and HNO3: Effect of acid concentration II 0.5 M HCl 10 M HCl 10 M 0.5 M x10
  22. 22. 22 Clean HOPG surface Deionised water Control experiments Ultra pure water
  23. 23. 23 Models to account for the features
  24. 24. 24 XPS HNO3 HCl Clean HNO3 HCl Clean
  25. 25. 25 HNO3 HCl HNO3 HCl XPS • No Ca, K, Na • Maximum O(a) ~ 4% monolayer
  26. 26. 26 Models to account for the features

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