Rapid Construction of Karst Landform-Featured Nickel Electrode for Efficient Oxygen Evolution Reaction.

Abstract

Electrodes are essential in alkaline water electrolysis for hydrogen production. However, developing straightforward and effective strategies to optimize the compositions and structures of electrode materials for enhanced performance and gas mass transfer remains a significant challenge. In this work, electrodes featuring karst landform-like surfaces and loaded with Ni-Fe hydroxide catalysts are rapidly fabricated by immersing nickel foam (NF) or nickel mesh (NM) in molten salt for corrosion. The roughened electrode structure, combined with the hydrophilic hydroxides formed on the surface, facilitates bubble formation and detachment. In situ Raman spectroscopy reveals that hydroxides undergo restructuring during the oxygen evolution reaction (OER), transforming into hydroxyl oxides and thereby enhancing electrocatalytic activity. The sample prepared by etching NF in molten salt for 60 s (NF-60s) exhibits outstanding performance in 1 M KOH, with an overpotential of 272 mV at a current density of 100 mA cm^-2 while maintaining stability over 600 h at 500 mA cm^-2. An alkaline water electrolyzer utilizing NF-60s as the anode and commercial Pt/C as the cathode achieved a current density of 500 mA cm^-2 at 1.63 V. This work demonstrates the broad applicability of hydrophilic and aerophobic nickel-based electrodes for water electrolysis at industrial-scale current densities.