Self-repairing hybrid nanosheet anode catalysts for alkaline water electrolysis connected with fluctuating renewable energy

Abstract

Water electrolysis is a core technology in the conversion of renewable energy to hydrogen, which is useful for energy storage and transportation. Alkaline water electrolysis (AWE) is one of the most suitable technologies because of its low cost and applicability to large-scale production of hydrogen; however, the AWE system exhibits electrode degradation under fluctuating electricity from renewable energy such as solar and wind energies. In this study, we demonstrate the use of a hybrid cobalt nanosheet (Co-ns), comprising brucite-type cobalt hydroxide modified with the tripodal ligand tris(hydroxymethyl)aminomethane, to form a highly stable self-repairing catalyst layer on a nickel anode under cycled potential. The Co-ns is functionalized by organic modification as a self-repairing catalyst with high catalytic activity, high dispersibility in an alkaline electrolyte, and protection of the nickel anode from corrosion. The Co-ns supplied from the alkaline electrolyte forms a catalyst layer via the anodic reaction on the surface of the nickel anode. This catalyst layer is detached under cycled potential simulating the fluctuating electricity of renewable energy; however, it is repaired by the constant current electrolysis simulating the steady state operation of AWE. The reaction between the Co-ns and nickel anode strengthens the connection between the catalyst layer and substrate. Furthermore, the Co-ns is less influential to the activity of a commercial cathode, indicating applicability to the conventional AWE system without changing the manifold structure. Consequently, the specially designed Co-ns catalyst shows great potential as a novel self-repairing function in an AWE system, which will enable stable operation under fluctuating electricity from renewable energy.