Morphology reconstruction and electronic optimization: Nickel-iron selenide nanospheres with Mo-doping as an efficient bifunctional electrocatalyst for overall water splitting

Developing high-performance bifunctional electrocatalysts can significantly simplify the water electrolysis system and raise the efficiency of hydrogen production. In this paper, Nickel-iron selenide with Mo-doping grown on nickel foam (Mo-NiFe-Se/NF) synthesized by two hydrothermal reactions, which shows excellent catalytic performance for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) in 1 mol/L KOH electrolyte, is an efficient bifunctional electrocatalyst. As the reaction skeleton, the unique 3D structure of nickel foam (NF) benefits the conduction of electrons and the diffusion of gases. Furthermore, compared with the undoped NiFe-Se/NF, the introduction of Mo leads to the structural reconstruction of the precursor, and the hydrotalcite flakes become small spheres with tiny nano-flakes on the surface, which dramatically increases the number of the active catalytic centers. In addition, the electronic coupling between MoSe 2 and Ni, Fe enhances the HER and OER activities of the material. When used in an overall water splitting system, the voltage at the current density of 10 mA·cm -2 is only 1.51 V. The research provides a new way to optimize the properties of metallic selenide materials and design bifunctional catalysts with higher efficiency and lower cost for water electrolysis. • The introduction of Mo generated nanospheres with large specific surface area; • Accelerated electron transfer efficiency and optimized electron structure; • Bifunctionality of the sample derives from the dual effects of doping; • Voltage at η 10 is only 1.51 V when used in overall water splitting system.