Heterointerface manipulation in the architecture of Co-Mo₂C@NC boosts water electrolysis

Heterostructures with tunable electronic properties have shown great potential in water electrolysis for the replacement of current benchmark precious metals. However, constructing heterostructures with sufficient interfaces to strengthen the synergistic effect of multiple species still remains a challenge due to phase separation. Herein, an efficient electrocatalyst composed of a nanosized cobalt/Mo₂C heterostructure anchored on N−doped carbon (Co−Mo₂C@NC) was achieved by in situ topotactic phase transformation. With the merits of high conductivity, hierarchical pores, and strong electronic interaction between Co and Mo₂C, the Co−Mo₂C@5NC−4 catalyst shows excellent activity with a low overpotential for the hydrogen evolution reaction (HER, 89 mV@10 mA cm⁻² in alkaline medium; 143 mV@10 mA cm⁻² in acidic medium) and oxygen evolution reaction (OER, 356 mV@10 mA cm⁻² in alkaline medium), as well as high stability. Furthermore, this catalyst in an electrolyzer shows efficient activity for overall water splitting and long−term durability. Theoretical calculations reveal the optimized adsorption−desorption behaviour of hydrogen intermediates on the generated cobalt layered hydroxide (Co LDH)/Mo₂C interfaces, resulting in boosting alkaline water electrolysis. This work proposes a new interface−engineering perspective for the construction of high−activity heterostructures for electrochemical conversion.