Defect-mediated Ru single-atom anchoring on FeCo-LDH/Ni₃S₂ core–shell architectures for durable and efficient AEM water splitting

The synergistic integration of vacancy engineering and single-atom catalysis offers a promising route to overcome the intrinsic limitations of conventional layered double hydroxides (LDHs) for overall water splitting. Here, we report a rationally designed Ru@d-FeCo-LDH/Ni₃S₂ core-shell heterostructure, constructed by selective Zn etching of FeCoZn-LDH to generate abundant cation vacancies that subsequently anchor atomically dispersed Ru. The Ni₃S₂ nanorod core provides high conductivity and efficient electron transport, while the defective LDH shell exposes coordinatively unsaturated Fe/Co sites to accelerate water dissociation, optimizes HER intermediates. Anchored Ru atoms further fine-tune hydrogen adsorption, modulate electronic structure, and promote charge redistribution at the heterointerface. These dual active centers synergistically optimize both HER and OER pathways. As a result, Ru@d-FeCo-LDH/Ni₃S₂ requires only 66 mV and 200 mV overpotentials to achieve 10 mA cm−2 for HER and OER, respectively, showing HER activity close to that of Pt/C and superior OER performance relative to RuO₂. Operando Raman and DFT analyses confirm accelerated interfacial water activation, near-optimal hydrogen adsorption free energy (ΔG_H* = 0.09 eV), and favorable oxyhydroxide reconstruction during OER. When applied in an anion exchange membrane water electrolyzer, the catalyst achieves 500 mA cm−2 at 1.77 V with stable operation for 500 h, highlighting its strong potential for efficient industrial alkaline water electrolysis.