Synergistic effects of Ni³⁺–Cu0/+ dual sites for efficient and stable hydrogen production in AEM water electrolysis

Achieving efficient and stable hydrogen evolution reaction (HER) with earth-abundant electrocatalysts is pivotal for boosting the efficiency of alkaline water electrolysis. Here, we report an oxygen vacancy (O v )-rich Cu₂O/NiO heterostructure, which triggers a peculiar interfacial charge transfer from NiO to Cu₂O, creating catalytically active Ni³⁺–Cu 0/+ dual sites to synergistically promote water dissociation and hydrogen adsorption. The Cu₂O/NiO heterostructure exhibits a low overpotential of 19.7 mV at 10 mA cm⁻² with Tafel slope of 36 mV dec⁻¹, outperforming most of the reported catalysts. The anion exchange membrane (AEM) electrolyzer equipped Cu₂O/NiO electrode enables 1.78 V to reach 1 A cm⁻² for more than 200 hours of continuous operation. A thorough characterization study involving HRTEM/XPS/EPR/XANES and DFT calculation exemplifies the interfacial charge transfer dynamics in Cu₂O/NiO heterostructure and its HER catalytic mechanism, offering a new paradigm for rational design of noble metal-free HER electrocatalysts for practical AEM water electrolysis. • Interfacial charge transfer from NiO to Cu₂O in oxygen vacancy-rich Cu₂O/NiO • Catalytically active Ni³⁺–Cu 0/+ dual sites promote HER • 19.7 mV overpotential at 10 mA cm⁻² with 36 mVdec⁻¹ Tafel slopes were obtained • HRTEM/XPS/EPR/XANES and DFT exemplified interfacial charge transfer in Cu₂O/NiO