Interfacial Engineering of Iron–Cobalt Hydroxide Nanosheet on Nickel Oxide Heterostructure for Efficient Overall Water Splitting by Reducing the Energy Barrier

Designing cost-effective and durable bifunctional electrocatalysts is critical for efficient water electrolysis and sustainable hydrogen production. Herein, we report an interfacial engineering approach to construct layered iron–cobalt hydroxides (Fe 1– x Co x (OH) 2 @ S1, where “ S1 ” represents the molar ratio of Fe:Co (3:1) and x = 0.25) with optimized Fe–O–Co active centers. The engineered heterointerface promotes charge redistribution and accelerates reaction kinetics, thereby reducing adsorption energy barriers for the key intermediates. The Fe 1– x Co x (OH) 2 @ S1 electrode achieves low overpotentials of ∼0.270 V for oxygen evolution and ∼0.192 V for hydrogen evolution at 10 mA cm –2, alongside a turnover frequency of 0.165 s –1 and high mass activity (∼11.2 A g –1 ). When used as both an anode and cathode, the symmetric electrolyzer operates at only 1.61 V to deliver 10 mA cm –2, rivaling the RuO 2 ∥Pt/C benchmarks. These results highlight the crucial role of Fe–Co–Ni interfacial coupling in modulating electronic structures and catalytic energetics. This work offers a generalizable strategy for developing advanced multimetal hydroxide catalysts toward highly efficient alkaline water electrolysis.