Well-defined CoSe₂@MoSe₂ hollow heterostructured nanocubes with enhanced dissociation kinetics for overall water splitting

Abstract

Hollow heterostructures have tremendous advantages in electrochemical energy storage and conversion areas due to their unique structure and composition characteristics. Here, we report the controlled synthesis of hollow CoSe₂ nanocubes decorated with ultrathin MoSe₂ nanosheets (CoSe₂@MoSe₂) as an efficient and robust bifunctional electrocatalyst for overall water splitting in a wide pH range. It is found that integrating ultrathin MoS₂ nanosheets with hollow CoSe₂ nanocubes can provide abundant active sites, promote electron/mass transfer and bubble release and facilitate the migration of charge carriers. Additionally, the surface electron coupling in the heterostructures enables it to serve as a source of sites for H⁺ and/or OH^- adsorption, thus reducing the activation barrier for water molecules adsorption and dissociation. As a result, the title compound, CoSe₂@MoSe₂ hollow heterostructures, exhibits an overpotential of 183 mV and 309 mV at a current density of 10 mA cm^-2 toward hydrogen evolution reactions and oxygen evolution reactions in 1.0 M KOH, respectively. When applied as both cathode and anode for overall water splitting, a low battery voltage of 1.524 V is achieved along with excellent stability for at least 12 h. This work provides a new idea for the design and synthesis of high-performance catalysts for electrochemical energy storage and conversion.