Electronic Structure Engineering of Ni 2 P Through Mo Incorporation With Enhanced Bifunctional Activity for Overall Water Splitting

Engineering a stable bifunctional electrocatalyst through water electrolysis for sustainable hydrogen production that can operate at industrially relevant current densities and also show high activity and versatility at low cost is still a major challenge. In this work, we report the rational design and synthesis of a Mo‐substituted nickel phosphide electrocatalyst using a sequential hydrothermal‐phosphidation strategy and systematically evaluate its bifunctional activity toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Mo‐substituted Ni 2 P (Mo‐Ni 2 P) achieves an overpotential of 240 mV at 10 mA cm −2 for the OER and requires an overpotential of only 231 mV to achieve 10 mA cm −2 for HER, maintaining stable current output over extended testing. When assembled as both anode and cathode in a symmetric two‐electrode configuration, the Mo‐Ni 2 P∥Mo‐Ni 2 P electrolyzer achieves overall water splitting at a low cell voltage of 1.51 V (10 mA cm −2 ), surpassing the conventional RuO 2 ∥Pt/C system and showing excellent stability over 60 h. Further, density functional theory (DFT) calculations also showed that Mo incorporation in Ni 2 P can modulate the adsorption free energies of key reaction intermediates during electrochemical reaction. This work highlights the potential of metal incorporation in Ni 2 P, offering the development of noble‐metal‐free electrocatalysts for efficient water electrolysis.