Integrated core-shell assembly of Ni₃S₂ nanowires and CoMoP nanosheets as highly efficient bifunctional electrocatalysts for overall water splitting

A paradigm for the rational design of active, abundant, and inexpensive bifunctional electrocatalysts with acceptable electrochemical energy conversion rates has yet to be achieved. Here, we describe the assembly of a superior bifunctional electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities based on a CoMoP/Ni₃S₂ multicomponent, heterointerface consisting of a freestanding electrocatalyst prepared by hydrothermal-phosphidation, consisting of one-dimensional Ni₃S₂ covered with Cereus cactus–like hierarchical CoMoP nanosheets. The resulting three dimensional CoMoP/Ni₃S₂ core-shell heterostructure exhibited remarkable HER and OER electrocatalysis, benefiting from modulated electronic structures, rapid mass diffusion, reduced charge-transfer resistance, and a larger electrochemically active surface area. Due to these superior functionalities, the CoMoP/Ni₃S₂ requires only 96.8 mV (at η₁₀) for HER catalysis and 270 mV (at η₅₀) for an OER process. Furthermore, a stable water-splitting device using CoMoP/Ni₃S₂ for both the anode and cathode required a low cell voltage of 1.54 V at 10 mA cm⁻². This work represents a significant advance in interface construction of transition-metal phosphide/sulfide for long-term water splitting.