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CO electroxidation on gold in alkaline media: a combined electrochemical, spectroscopic, and DFT study

CO electroxidation on gold in alkaline media: a combined electrochemical, spectroscopic, and DFT study
CO electroxidation on gold in alkaline media: a combined electrochemical, spectroscopic, and DFT study
The aim of the present work is to provide a deeper understanding of gold catalysis for CO electrooxidation in alkaline media, through a combined electrochemical, spectroscopic, and DFT study. Voltammetric and spectroscopic measurements evidence that the amount of CO irreversibly adsorbed on gold increases as the adsorption potential becomes more negative (vs SHE). This explains why higher CO coverages can be achieved in more alkaline solutions, since the value of adsorption potential vs RHE becomes more negative vs SHE with increasing pH. On the other hand, the combination of FTIRRAS experiments and DFT calculations shows that the adsorption site of irreversibly adsorbed CO on Au(111) depends on the value of the adsorption potential. It is concluded that CO adsorption on top sites takes place at all studied potentials, and hollow and bridge sites also become occupied for adsorption potentials lower and higher than 0 V vs RHE, respectively. However, it should be noted that our DFT calculations give values of the CO binding energies that are not strong enough to explain CO irreversible adsorption. This may be partly attributed to the fact that OH coadsorption is not included in the calculations. Indeed, this work presents two experimental facts that suggest that CO adsorption on gold promotes the coadsorption of OH species: (i) CO irreversibly adsorbed on Au(111) and Au(100) leads to an unusual voltammetric feature, whose charge indicates the stabilization of one OH species per adsorbed CO species; (ii) the apparent transfer coefficient of this unusual state is close to unity, suggesting that it is due to a presumed structural transformation coupled to OH adsorption. Finally, the effect of the adsorption potential on the bulk CO electrooxidation is also studied. It is found that, on Au(111), an increased occupation of CO on multifold (hollow) sites seems to result in a less efficient catalysis. However, on Au(110), an increased coverage of CO on top sites does not produce any significant change in catalysis
0743-7463
12425-12432
Rodriguez, Paramaconi
5a751a4e-490e-42bb-9c22-7b0fc72e9a09
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Koverga, Andrey
0be72741-3582-484f-b044-679ed271f492
Frank, Stefan
552b3842-9a95-40c9-8005-83fcb4133128
Koper, Marc T.M.
40a12fab-f3d3-4518-b739-95b4720ac120
Rodriguez, Paramaconi
5a751a4e-490e-42bb-9c22-7b0fc72e9a09
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Koverga, Andrey
0be72741-3582-484f-b044-679ed271f492
Frank, Stefan
552b3842-9a95-40c9-8005-83fcb4133128
Koper, Marc T.M.
40a12fab-f3d3-4518-b739-95b4720ac120

Rodriguez, Paramaconi, Garcia-Araez, Nuria, Koverga, Andrey, Frank, Stefan and Koper, Marc T.M. (2010) CO electroxidation on gold in alkaline media: a combined electrochemical, spectroscopic, and DFT study. Langmuir, 26 (14), 12425-12432. (doi:10.1021/la1014048).

Record type: Article

Abstract

The aim of the present work is to provide a deeper understanding of gold catalysis for CO electrooxidation in alkaline media, through a combined electrochemical, spectroscopic, and DFT study. Voltammetric and spectroscopic measurements evidence that the amount of CO irreversibly adsorbed on gold increases as the adsorption potential becomes more negative (vs SHE). This explains why higher CO coverages can be achieved in more alkaline solutions, since the value of adsorption potential vs RHE becomes more negative vs SHE with increasing pH. On the other hand, the combination of FTIRRAS experiments and DFT calculations shows that the adsorption site of irreversibly adsorbed CO on Au(111) depends on the value of the adsorption potential. It is concluded that CO adsorption on top sites takes place at all studied potentials, and hollow and bridge sites also become occupied for adsorption potentials lower and higher than 0 V vs RHE, respectively. However, it should be noted that our DFT calculations give values of the CO binding energies that are not strong enough to explain CO irreversible adsorption. This may be partly attributed to the fact that OH coadsorption is not included in the calculations. Indeed, this work presents two experimental facts that suggest that CO adsorption on gold promotes the coadsorption of OH species: (i) CO irreversibly adsorbed on Au(111) and Au(100) leads to an unusual voltammetric feature, whose charge indicates the stabilization of one OH species per adsorbed CO species; (ii) the apparent transfer coefficient of this unusual state is close to unity, suggesting that it is due to a presumed structural transformation coupled to OH adsorption. Finally, the effect of the adsorption potential on the bulk CO electrooxidation is also studied. It is found that, on Au(111), an increased occupation of CO on multifold (hollow) sites seems to result in a less efficient catalysis. However, on Au(110), an increased coverage of CO on top sites does not produce any significant change in catalysis

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Published date: 2010
Organisations: Electrochemistry

Identifiers

Local EPrints ID: 345751
URI: https://eprints.soton.ac.uk/id/eprint/345751
ISSN: 0743-7463
PURE UUID: 300d55d9-a8d3-4909-b712-0ca110ad7cdf
ORCID for Nuria Garcia-Araez: ORCID iD orcid.org/0000-0001-9095-2379

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Date deposited: 29 Nov 2012 14:54
Last modified: 19 Nov 2019 01:37

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