Spontaneous formation of core-shell silver-copper oxide by carbon dot-mediated reduction for enhanced oxygen electrocatalysis

Abstract

Water-soluble carbon dots (CDs) were successfully synthesized by a simple electrochemical technique and used as a clean, green reductive agent to prepare core-shell, silver-copper oxide (Ag@CuO) nanoparticles under organic ligand-free conditions. In a typical procedure, ethanol was used as a source of carbon to produce CDs in alkaline media. Surfactant-free Ag@CuO nanostructure was spontaneously formed by spontaneous redox reaction between Ag+/Cu2+ and CDs. Physicochemical characterization by X-ray diffraction, UV–Vis spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy identified the presence of core-shell structures and of Cu in oxidation state II. For comparison purposes, Ag and CuO nanoparticles were prepared in the same manner. A detailed electrochemical investigation revealed that enhanced oxygen reduction reaction (ORR) was synergistically achieved using the Ag@CuO nanoparticles, which greatly accelerated the electrochemical reduction of intermediate peroxide (HO2−) during ORR.