Phase‐Stabilized Nickel–Molybdenum Electrocatalyst by Samarium Doping for Hydrogen Evolution in Alkaline Water Electrolysis

Abstract Although the nickel–molybdenum electrocatalyst exhibits excellent activity in the alkaline hydrogen evolution reaction (HER), its stability is poor mainly due to molybdenum leaching. This work reports that doping samarium into nickel–molybdenum electrocatalyst effectively suppresses molybdenum leaching by forming a stable phase consisting of Sm, Mo, and O elements. The resulting electrode displays no noticeable activity degradation during the long‐term testing (> 850 h) under a current density of 500 mA cm −2 in 1 м KOH . This enhanced stability is ascribed to the formation of a robust phase within the HER potential windows in alkaline electrolytes, as evidenced by the Pourbaix diagram. Furthermore, the samarium‐modified electrocatalyst exhibits increased activity, with the overpotential decreasing by ≈59 mV from 159 to 100 mV at 500 mA cm −2 compared to the unmodified counterpart. These remarkable properties stem from samarium doping, which not only facilitates the formation of a stable phase to inhibit molybdenum leaching but also adjusts the electronic properties of molybdenum to enhance water dissociation.