Rationally designed nickel-cobalt oxide/sulfide heterostructure for high-performance oxygen evolution reaction and anion exchange membrane water electrolysis

Abstract

To realize the practical application of anion exchange membrane water electrolysis (AEMWE), it is essential to develop highly active, durable, and cost-effective electrocatalyst for oxygen evolution reaction (OER). Herein, we report a hollow-structured Ni_xCo_1−xO/Ni₃S₂/Co₉S₈ heterostructure synthesized via sequential template-assisted growth, thermal oxidation, and controlled sulfidation process. The abundant bimetallic heterointerfaces not only provide additional active sites but also promote electronic modulation via charge redistribution. Additionally, the porous and hollow architecture enhances active surface area and mass transfer ability, thereby increasing the number of accessible active sites for alkaline OER. As a result, the prepared electrocatalyst achieves low overpotential of 310 mV at 10 mA cm⁻² and small Tafel slope of 55.94 mV dec⁻¹, demonstrating the exceptional electrocatalytic performance for alkaline OER. When integrated as the anode in an AEMWE cell, it delivers outstanding performance with only 1.657 V at 1.0 A cm⁻² and reaches high current density of 5.0 A cm⁻² at 1.989 V, surpassing those of commercial RuO₂. The cell also shows excellent long-term durability over 100 h with minimal degradation. This study highlights the strong potential of rationally engineered oxide/sulfide heterostructures for next-generation alkaline water electrolysis.