Ni3S2@NiFePx electrode with dual-anion-modulated layer for efficient and stable oxygen evolution

The rational construction of high-performance and stable electrocatalyst for oxygen evolution reaction (OER) is a prerequisite for efficient water electrolysis. Herein, we develop a broccoli-like Ni₃S₂@NiFeP_x (Ni₃S₂@NFP) catalyst on nickel foam (NF) via a sequential two-step layer-by-layer assembly electrodeposition method. X-ray diffraction, in situ Raman and Fourier-transform infrared spectra have mutually validated the element segregation and phase refusion during OER condition. The reconstruction of double layer Ni₃S₂@NFP facilitates the formation of the active (oxy)hydroxides, which is modulated by the dual anionic layer with mixed sulfate and phosphate ions. As a result, the obtained Ni₃S₂@NFP electrode exhibits low overpotential (329 mV) and long-term durability (～500 h) for OER at current density of 500 mA/cm². Moreover, the self-supported Ni₃S₂@NFP can act as an efficient and durable anode in alkaline anion exchange membrane water electrolysis device (AEMWE). This work provides a facile and scaled-up strategy to construct self-supported electrocatalyst and emphasizes the crucial role of anions in pre-catalyst reconstruction and enhancing OER performance.