Thin‐Layered Cobalt‐Based Catalysts on Stainless‐Steel Microfibers for the Efficient Electrolysis of Water

Herein, we introduce a highly catalytic core–shell microfiber electrode based on a cobalt oxygen‐evolving catalyst (Co‐OEC) electrodeposited on a three‐dimensional (3 D) mat of stainless‐steel (SS) microfibers. The resulting core–shell microfibers (Co‐MF) with a catalytic shell exhibit a turnover frequency and a current density that are much higher than those of a conventional Co‐OEC on a flat SS foil (Co‐F) at neutral pH. The onset potential of the catalytic wave of Co‐MF is also appreciably lower than that of Co‐F owing to a combination of the higher surface activity of the Co‐OEC and the enhanced local electric field in the 3 D network of the metal microfibers. This study suggests that cost‐effective, stable, and earth‐abundant SS microfibers can be a promising substrate to enhance the surface activity of water‐oxidation electrocatalysts.