Summary Recently, the development of durable electrocatalysts with bifunctional and high‐efficiency applications in overall water splitting has become a hot spot in the energy field. Herein, Mo2C@g‐C3N4@NiMn‐LDH, a bifunctional electrocatalyst, is obtained through self‐assembly strategies of heat treatment, g‐C3N4 coating, and hydrothermal growth of NiMn‐LDH nanosheets using homogeneous Mo2C precursor nanowire as template. Specifically, Mo2C and NiMn‐LDH are located on the inner wall and outer wall of g‐C3N4, respectively, realizing separate‐sided different functions of g‐C3N4 by electronic control of the interface. The Mo2C@g‐C3N4@NiMn‐LDH composite exhibits excellent bifunctional electrocatalytic performance, in which the inner Mo2C@g‐C3N4 are the dominant catalytic active center for hydrogen evolution reaction (HER) and the outer NiMn‐LDH acts as co‐catalyst, whereas the active center transfer to g‐C3N4@NiMn‐LDH for oxygen evolution reaction (OER) and the inner Mo2C turns into the co‐catalyst. The performance of Mo2C@g‐C3N4@NiMn‐LDH electrocatalyst is reflected by the overpotential of 116 mV (for HER) and 290 mV (for OER) at the current density of 10 mA cm−2 in alkaline medium, respectively. In addition, the voltage required for overall water splitting to reach 10 mA cm−2 is only 1.587 V, and the sample has excellent stability under constant applied voltage. This work provides a strategy for the development of high‐performance electrocatalysts with controllable active sites through interface engineering, so as to achieve competitive equilibrium of different reaction processes.

Maximizing the usable space of electrocatalysts and fine-tuning the interface geometry as well as the electronic structure to facilitate hydrogen and oxygen evolution reactions (HER and OER) have always been the focus of research. Herein, a homogeneous porous nanoparticle construction strategy was proposed, in which molybdenum nitride (Mo2N) particles were prepared by controlled heat treatment of the precursor nanoparticle induced by polyethylene glycol, and the Mo2N/Co-C3N4 heterostructure with a pore size of about 1.13 nm was obtained by compounding Co-anchored graphitic carbon nitride. In particular, exploring the change of charge distribution at the interface based on the principle of “electron complementation” shows that under the regulation of nitrogen with high electronegativity, the affinity of active site Co to oxygenated species in the OER process and the adsorption as well as cleavage ability of HER reactants in the active site were effectively optimized. Thus, Mo2N/Co-C3N4 not only inherits the functions of each component, but also provides an ideal heterogeneous interface for exhibiting impressive bifunctional activity, which only needs 100 and 210 mV to deliver 10 mA cm–2 for the HER and OER, respectively. In addition, the Mo2N/Co-C3N4 catalyst also demonstrates high overall water splitting stability with a slight current decrease after 95 h. Manipulating the electronic structure of multiple sites by constructing electronically complementary interfaces may provide another avenue to develop highly active catalysts for overall water splitting and other applications.