Support Effects on Water Activation and Oxygen Reduction over Au-SnOx Electrocatalysts Observed with X-ray Absorption Spectroscopy
Gold nanoparticles supported on hydrous tin oxide (Au-SnOx) and mixed with Vulcan carbon are active electrocatalysts for the four-electron oxygen reduction reaction (ORR) to water in acid electrolyte below 0.55 V vs a reversible hydrogen electrode. In comparison, gold on Vulcan carbon (Au/VC) is inactive for the ORR in acid and generates mostly peroxide (i.e., two-electron reduction). These results imply that the SnOx support imparts the ORR activity of the Au. We study this metal support interaction by in situ X-ray absorption fine structure and near edge spectroscopy at the Au L3 and Sn K edges in an electrochemical cell. The results for 10 wt % (2 nm) and 20 wt % (2.7 nm) Au nanoparticles supported on SnOx suggest that a bifunctional mechanism plays the dominant role in the ORR reaction below 0.55 V. O2 adsorbs and dissociates on the SnOx surface with apparent simultaneous electron transfer from the Au and then is reduced further to water by electron transfer from the Au. Enhanced O[H] adsorption occurs at potentials above 1.2 V on the Au-SnOx catalysts. This O[H] adsorption is enhanced through a ligand mechanism involving the SnOx support but has no apparent effect on the ORR.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959722
- Report Number(s):
- BNL-82708-2009-JA; JESOAN; TRN: US201016%%866
- Journal Information:
- Journal of the Electrochemical Society, Vol. 155, Issue 8; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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