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

Abstract

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 (Ov)-rich Cu₂O/NiO heterostructure, which triggers a peculiar interfacial charge transfer from NiO to Cu₂O, creating catalytically active Ni³ ⁺–Cu0/+ 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 1.0 A cm⁻² for >200 h of continuous operation. Thorough characterizations including HRTEM/XPS/EPR/XANES and DFT calculations exemplify the interfacial charge transfer dynamics in the Cu₂O/NiO heterostructure during HER, offering a new paradigm for rational design of noble metal-free HER electrocatalysts for AEM water electrolysis.