Towards Efficient Bifunctional Electrocatalysis: Molybdenum-Tuned Nickel Sulfoselenide Electrodes for Alkaline Water Splitting

A highly efficient bifunctional electrocatalyst, denoted as M-NSSe, has been rationally designed and synthesized for overall alkaline water splitting via a hydrothermal-calcination route. The introduction of molybdenum (Mo) into the nickel sulfur-selenide (NiSSe) framework effectively modulates its electronic structure, enhancing the intrinsic electrocatalytic properties. When integrated into a practical two-electrode electrolyzer, the M-NSSe catalyst achieves a current density of 10 mA cm - 2 at a low cell voltage of 1.45 V, highlighting its excellent catalytic efficiency. Electrochemical analysis reveals low overpotentials of 170 mV for the oxygen evolution reaction (OER) and 110 mV for the hydrogen evolution reaction (HER), demonstrating its superior bifunctional activity. Moreover, long-term stability tests indicate that M-NSSe maintains consistent performance over 24 hours, suggesting remarkable durability under operational conditions. The outstanding performance can be attributed to Mo-induced electronic structure modulation, which increases the density of states near the Fermi level, thereby accelerating charge transfer kinetics and facilitating rapid adsorption/desorption of reaction intermediates. Structural and morphological characterizations confirm the formation of a homogeneous and robust nanosheet architecture with abundant active sites, which further contributes to the enhanced electrochemical performance. This work not only elucidates the fundamental mechanism by which Mo doping improves the electrocatalytic behavior of nickel chalcogenides but also underscores the practical potential of the hydrothermal-calcination strategy for constructing cost-effective, high-performance electrocatalysts for sustainable hydrogen production. The findings provide a promising avenue for the rational design of next-generation catalysts in energy conversion technologies.