Super-Nernstian Shifts of Interfacial Proton-Coupled Electron Transfers: Origin and Effect of Noncovalent Interactions

详细信息    查看全文

• 作者：Christopher Wildi ; Gema Cabello ; Martín E. Zoloff Michoff ; Patricio Vélez ; Ezequiel P. M. Leiva ; Juan José Calvente ; Rafael Andreu ; Angel Cuesta
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 28, 2016
• 年：2016
• 卷：120
• 期：29
• 页码：15586-15592
• 全文大小：373K
• 年卷期：0
• ISSN：1932-7455

文摘

Anions whose specific adsorption involves a proton-coupled electron transfer (PCET) include adsorbed OH (OH_ad), which plays an enormously relevant role in many fuel-cell reactions. OH_ad formation has often been found to happen in alkaline solutions at potentials more negative than expected from a Nerstian shift, and this has been proposed as the reason for the often easier oxidation of organic molecules in alkaline media, as compared to acids. Noncovalent interactions with electrolyte cations have also been shown to affect the stability of OH_ad. Using cyanide-modified Pt(111) as a model, we show here that interfacial PCETs will show a super-Nernstian shift if (i) less than one electron per proton is transferred and (ii) the plane of proton–electron transfer and that of the metal surface do not coincide. We also show that electrolyte cations have a double effect: they provoke an additional shift by blocking the site of transfer but decrease the super-Nernstian contribution by separating the plane of transfer from the outer Helmholtz plane.