Construction of Ni Atomic Single Layer on Au Single Crystal Surface and Its in Situ Scanning Tunneling Microscopic Studies under Oxygen Evolution Reaction

• 1、College of Chemistry and Chemical Engineering,Hunan University

Abstract：The large-scale application of industrial water electrolysis was limited by the sluggish dynamics of oxygen evolution reaction (OER). The research of using cheap non-noble metal-based OER electrocatalyst replacing noble metals has recently attracted much attention. It is well known that the electrode surface of non-noble metal as well as their related compounds can be easily oxidized to the corresponding metal oxides or hydroxides in alkaline electrolytes for OER, which serves as the actual active species. However, there are few in-situ studies on this oxidation process, resulting in the limited understanding on the nature of active sites after chemical and structural transformation. In this paper, a series of single atomic layer of Ni islands at different surface coverage was constructed on Au(111) single crystal surface by under-potential electrodeposition. In situ electrochemical scanning tunneling microscope (EC-STM) was employed to study the chemical transformation and structural evolution upon the oxidation process, with special emphasis on the structural nature of OER active sites. The combined electrochemical measurements and EC-STM studies reveals a quasi linear relationship between the OER activity and the total edge length of Ni islands, demonstrating the active nature of edge sites of Ni islands for OER. In situ EC-STM studies reveals the structural evolution from atomically flat single layer Ni islands to rougher Ni-hydroxide islands. The roughing process was observed starting initially from the edge sites evolving to the inner phase area, which demonstrating unambiguously again the OER active nature of edge sites for Ni-based electrocatalysis.

Keywords： Oxygen evolution reaction Model catalyst In situ structural characterization Electrochemical scanning tunneling microscopy Single crystal electrode