Spontaneous heterophase atomic structure engineering of NiMo(S)/NiMoP for enhanced overall electrochemical water splitting in neutral media

Hydrogen/oxygen evolution reactions catalyzed by transition metals have sluggish kinetics during prolonged water electrolysis in neutral media. Covering the surface with an amorphous protecting layer can improve the reactivity and stability of these catalysts; however, the rational design of crystalline–amorphous electrocatalysts for efficient and stable water electrolysis in neutral media has been challenging. Here, we present a unique and facile strategy for the in situ synthesis of the heterophase-structured cNiMo(S)/aNiMoP catalyst with a crystalline–amorphous phase boundary. The high-density active sites present on the surface and at the interface of the heterophase is responsible for the excellent electrochemical activity and operational stability of water electrolysis in neutral media. For the overall water splitting reaction, the cNiMo(S)/aNiMoP || cNiMo(S)/aNiMoP system displays a low cell voltage of 1.67 V to achieve a current density of 100 mA cm⁻². Moreover, negligible performance degradation was observed during a continuous long-term stability test for 100 h.