Unveiling the Promotion of Fe in Ni₃S₂ Catalyst on Charge Transfer for the Oxygen Evolution Reaction

In recent years, catalysts based on transition metal sulfides have garnered extensive attention due to their low cost and excellent electrocatalytic activity in the alkaline oxygen evolution reaction. Here, the preparation of Fe-doped Ni₃S₂ via a one-step hydrothermal approach is reported by utilizing inexpensive transition metals Ni and Fe. In an alkaline medium, Fe-Ni₃S₂ exhibits outstanding electrocatalytic activity and stability for the OER, and the current density can reach 10 mA cm^-2 with an overpotential of 163 mV. In addition, Pt/C||Fe-Ni₃S₂ is used as the membrane electrode of the anion exchange membrane water electrolyzer, which is capable of providing a current density of 650 mA cm^-2 at a cell voltage of 2.0 V, outperforming the benchmark Ir/C. The principle is revealed that the doping of Fe enhances the electrocatalytic water decomposition ability of Ni₃S₂ by in situ Raman and in situ X-ray absorption fine structure. The results indicate that the doping of Fe decreases the charge density near Ni atoms, which renders Fe-Ni₃S₂ more favorable for the adsorption of OH^- and the formation of ^*OO^- intermediates. This work puts forward an effective strategy to significantly improve both the alkaline OER activity and stability of low-cost electrocatalysts.