Synergistic Mo and S co-doping on NiSe₂ electrodes for reduced kinetic barrier of water electrolysis

Hydrogen is an ideal energy carrier that can replace non-renewable fossil fuels in the future, and its production using electrochemical water splitting is one of the cleanest and best effective approaches. However, the commercialization of large-scale H₂ production technologies requires earth-abundant electrocatalysts that exhibit Pt-like activity. This study reports, the dual doping of cations (Mo) and anions (S) into metallic NiSe₂ using a green electrodeposition method to upgrade the H evolution reaction (HER) activity and durability of NiSe₂, at the same time. Sulfur doping into NiSe₂ provides an additional active site, whereas dual doping of Mo/S into NiSe₂ boosts the HER kinetics and durability. Additionally, a NiSe₂ matrix is doped with different concentrations of Mo/S and their HER performance is studied. A 5% Mo/S–NiSe₂ has an optimized H∗ absorption energy, which is favorable for high HER performance. To drive the current densities of −10 and −100 mA cm⁻², 5% Mo/S–NiSe₂ electrode requires a small overpotentials of 89 and 222 mV, respectively, and the corresponding Tafel slope is 57 mV dec⁻¹. The enhanced HER activity of Mo/S–NiSe₂ is credited to the electronic structure adjustment, generation of a porous structure, and ample electrochemically active surface area owing to Mo/S dual doping. This strategy is promising for exploring new functional electrocatalysts for clean H₂ production.