Ni Vacancy-Regulated NiFe2O4/NiO Heterojunction as an Efficient Bifunctional Water Electrolysis Catalyst

Hydrogen, as an ideal clean energy carrier, its green production technology is at the core of the energy transition. While water electrolysis for hydrogen production can be coupled with renewable energy to achieve “green electricity-green hydrogen” conversion, the high overpotential of the anodic oxygen evolution reaction leads to a significant increase in energy consumption. In this study, we designed and prepared an iron-based heterojunction oxygen evolution reaction (OER)-hydrogen evolution reaction (HER) bifunctional catalyst (VNi0.5-NiFe2O4/NiO) using a hydrothermal combined with alkaline etching strategy. Experiments show that in alkaline media, the overpotential for the oxygen evolution reaction is 234 mV at a current density of 10 mA cm−2, and the overpotential for the hydrogen evolution reaction is 161 mV, demonstrating excellent bifunctional catalytic activity. The divalent cation vacancies of Ni synergistically optimize the electronic structure of the material, forming a nano-flower-like porous morphology, significantly increasing the density of active sites and reducing charge transfer resistance. This study provides new insights into the development of low-cost, high-efficiency non-precious metal water electrolysis catalysts, holding significant implications for advancing the large-scale production of green hydrogen.