Temperature Dependence of Proton Electroreduction Kinetics at Gold(111) and (210) Surfaces
PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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Rate-potential data are reported for proton electroreduction on Au111 and 210 in acidic perchlorate electrolytes over the temperature range 0-60 C, and examined with regard to temperature dependence of the transfer coefficient alpha. Since the Tafel plots exhibit significant curvature the analysis requires information on the temperature-dependent thermodynamics i.e. the reaction entropy for the proton discharge step. This was estimated from temperature-dependent voltammetry of reversible proton discharge to form adsorbed hydrogen on platinum. When evaluated at a constant overpotential for the proton discharge step, alpha for this reaction on both Au111 and 210 is independent of temperature. An effect of electrocatalysts for proton reduction on Au111 engendered by prior voltametric oxide formation was also observed. This effect is attributed to formation of surface defects on the basis of recently reported scanning tunneling microscopy data. Surface structural changes are also evident in the morphology of cyclic voltammograms obtained in the double-layer region. Electrochemical effects disappear with time when potential is held in the double layer region, and more rapidly at higher temperatures.
- Physical Chemistry
- Metallurgy and Metallography