Efficient Hydrogen Evolution Reaction on Ni₃S₂ Nanorods with a P/N Bipolar Electrode Prepared by Dealloying Sulfurization of NiW Amorphous Alloys

Rationally designing a new type of earth-abundant and environmentally friendly material with high performance and durability that can convert water to energy by the control point defect method is still a challenge. Herein, we report a newly adjusted method to prepare Ni₃S₂ nanorods (NRs) by combining transition metals and nanostructures while introducing sulfur vacancies as a means of promoting electron–hole pair transfer. It shows excellent hydrogen evolution electrocatalytic (HER) activity with an overpotential of 162 mV at j = 10 mA cm^–2 and chemical stability in 1 M NaOH solution. Electrochemically active surface area (ECSA) calculation results of 0.36 m² g^–1 confirm the superior performance of Ni₃S₂ with sulfur vacancies compared to other materials. The Mott–Schottky (M-S) and electrochemical impedance spectroscopy (EIS) results allowed effective optimization of the nanorods after obtaining sulfur vacancies and, surprisingly, showed that they are a P/N-type semiconductor. We speculate that the HER of the Ni₃S₂ NRs is mainly dominated by the Heyrovsky process. At the same time, the synergistic reaction produced by the electron–hole transfer guided by sulfur vacancies promotes the Heyrovsky process, thus jointly improving the effectiveness of the Ni₃S₂ NRs. The method of introducing sulfur vacancies in the nanomaterial is simple and has excellent properties, which suggests broad applications for research in the fields of environment and energy.