Graphite Surface Functionalization for Gold Deposition
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
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
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
………….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
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
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
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
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
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
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
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
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
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
AFM images of nanoparticles
deposited on HOPG from HAuCl4(aq)
HOPG
Untreated
HNO3
treated
HNO3
treated and heated
to 573 K
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
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
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
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
Comparison of HCl and HNO3:
Effect of acid concentration II
0.5 M HCl
10 M HCl
10 M
0.5 M
x10