Suppression of Catalyst Layer Detachment by Interfacial Microstructural Modulation of the NiCo2O4/Ni Oxygen Evolution Electrode for Renewable Energy-Powered Alkaline Water Electrolysis

Alkaline water electrolysis (AWE) is a large-scale hydrogen production technology. A major degradation mode of AWE when using fluctuating power derived from renewable energies is the detachment of the catalyst layer (CL). Here, this study investigates the CL detachment mechanism of NiCo2O4-CL-coated Ni (NCO/Ni) electrodes under an accelerated durability test (ADT) simulating a fluctuating power and the effect of post-annealing on detachment behavior. Microstructural analysis reveals that detachment begins at the nanoscale gaps between the stacked CLs and between CL and the substrate. Post-annealing at 400 °C removes the degradation starting point in CL, and a composition gradient Co-doped NiO interlayer and NiO(111)/Ni(111) epitaxial interface form between CL and the Ni substrate, nearly suppressing CL detachment. Although the electrode performance of the annealed sample is initially lower than that of the as-prepared sample, the overpotential is significantly reduced during ADT due to the formation of the NiCo hydroxide active surface layer. These results demonstrate that interfacial microstructural modulation by post-annealing is a powerful approach to realizing durable electrodes for green hydrogen production by renewable energy-powered AWE.