Dual wetting electrode surfaces for alkaline water electrolysis

Abstract

Nickel electrodes are widely used in alkaline water electrolysis, yet the remaining electrode overpotentials are leading to significant losses in electrochemical performance. These are partly due to the electrogenerated bubbles growing at the surface. Tuning the nickel surface for better bubble management is therefore of great relevance. Here, Direct Laser Writing is used to generate pillar-like surfaces with dual wetting behavior. This combines hydrophilic grooves with hydrophobic ripples on top of each pillar. Furthermore, the grooves show superspreading properties due to the capillary forces within them, which enables a fully wetted surface. The hydrophobic pillars serve as initial nucleation sites where the bubbles remain pinned during their growth. This results in a larger detachment size of the bubbles. In combination with an increase of the electrochemically active surface area by a factor of 9, a reduction of the overpotential for hydrogen evolution reaction of $\approx$ 24 % at -100 mA cm⁻² is found.