Designing and constructing bifunctional electrocatalysts is vital for water splitting. Particularly, the rational interface engineering can effectively modify the active sites and promote the electronic transfer, leading to the improved splitting efficiency. Herein, free‐standing and defect‐rich heterogeneous MoS 2 /NiS 2 nanosheets for overall water splitting are designed. The abundant heterogeneous interfaces in MoS 2 /NiS 2 can not only provide rich electroactive sites but also facilitate the electron transfer, which further cooperate synergistically toward electrocatalytic reactions. Consequently, the optimal MoS 2 /NiS 2 nanosheets show the enhanced electrocatalytic performances as bifunctional electrocatalysts for overall water splitting. This study may open up a new route for rationally constructing heterogeneous interfaces to maximize their electrochemical performances, which may help to accelerate the development of nonprecious electrocatalysts for overall water splitting.

HIGHLIGHTS • Freestanding Mo-doped NiCoP nanosheets are designed as bifunctional electrocatalysts for overall water splitting. • Remarkable electrocatalytic performances are achieved by Mo doping, where a low-water-splitting voltage of 1.61 V at 10 mA cm −2 is obtained.

Strong chemical bonds between transition metal oxides and carbon materials which enable fast electron transfer kinetics are highly required in supercapacitor electrodes.

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