In order to solve the problems of high cost and low electrolytic efficiency of traditional catalysts and realize the development of large-scale green hydrogen production technology, an interfacial catalyst based on transition metal was constructed by structural design and synthesis optimization in this study. The Ni₃Se₂/NiSe@NF heterojunction bifunctional electrocatalyst with interface structure was prepared on a nickel foam (NF) substrate by a two-step hydrothermal method. The strong charge transfer at the heterogeneous interface of Ni₃Se₂/NiSe@NF effectively optimizes the electronic structure of Ni₃Se₂/NiSe@NF compared with the single interface (Ni₃Se₂@NF and NiSe@NF), thus increasing the activities of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The prepared Ni₃Se₂/NiSe@NF has an overpotential of 71 and 207 mV (10 mA·cm^-2) at 1 mol/L KOH, respectively, and has impressive stability (no significant degradation within 500 h). In addition, when the current density is 10 mA·cm^-2, the current of the monolithic water decomposition electrolyzer with Ni₃Se₂/NiSe@NF as anode and cathode can be reduced to 1.52 V. Therefore, this study provides a new idea for the development of low-cost and high-stability catalysts for water electrolysis, which is expected to accelerate the integration of green hydrogen preparation and renewable energy systems, and help realize the goal of “dual-carbon”.