Ultrahigh electrocatalytic activity and durability of bimetallic Au@Ni core-shell nanoparticles supported on rGO for methanol oxidation reaction in alkaline electrolyte

Abstract

The bimetallic Au@Ni core-shell nanoparticles (NPs) supported on reduction graphene oxide (Au@Ni-rGO) nanocomposites are synthesized for the first time in aqueous medium following a successive reduction strategy. The morphology, structure and composition of the Au@Ni-rGO nanocomposites are characterized by transmission electron microscopy (TEM), scanning TEM-high angular annular dark field (STEM-HAADF), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectrometer (EDS) and EDS-mapping. The TEM, STEM-HAADF images and EDS-mapping results demonstrate the formation of core-shell structure with Au core and Ni shell. Besides, the Au@Ni core-shell NPs directly grow on rGO support with good dispersion. From the XPS and EDS results, the Au@Ni-rGO nanocomposites consist of Au, Ni, C and O elements. The electrochemical experiments indicate that the Au@Ni-rGO/glass carbon electrode (Au@Ni-rGO/GCE) displays excellent electrocatalytic activity towards methanol oxidation reaction (MOR) in alkalic electrolyte with a highly mass activity of 1446.7 mA mg−1. Furthermore, it presents outstanding cycling stability in the MOR conditions, with the mass current retention of 87% compared with its initial value after 3 h (10800 s). The electrocatalyst also displays excellent CO tolerance in MOR process. Therefore, the Au@Ni-rGO nanocomposites offer exciting opportunities to be practical application in direct methanol fuel cells as non-Pt electrocatalyst.