Surface Oxidation of AuNi Heterodimers to Achieve High Activities toward Hydrogen/Oxygen Evolution and Oxygen Reduction Reactions.

Abstract

Although much attention has been paid to the exploration of highly active electrocatalysts, especially catalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the development of multifunctional catalysts remains a challenge. Here, we utilize AuNi heterodimers as the starting materials to achieve high activities toward HER, OER and ORR. The HER and ORR activities in an alkali environment are similar to those of Pt catalysts, and the OER activity is very high and better than that of commercial IrO2 . Both the experimental and calculated results suggest that the surface oxidation under oxidative conditions is the main reason for the different activities. The NiO/Ni interface which exists in the as-synthesized heterodimers contributes to high HER activity, the Ni(OH)2 -Ni-Au interface and the surface Ni(OH)2 obtained in electrochemical conditons gives rise to promising ORR and OER activities, respectively. As a comparison, a Au@Ni core-shell structure is also synthesized and examined. The core-shell structure shows lower activities for HER and OER than the heterodimers, and reduces O2 selectively to H2 O2 . The work here allows for the development of a method to design multifunctional catalysts via the partial oxidation of a metal surface to create different active centers.