Fe-Incorporated Co _<b>3</b> O _<b>4</b> Microsheets for Oxygen Evolution at High Current Densities in All-Platinum-Group-Metal-Free Alkaline Anion Exchange Membrane Electrolyzers

The development of active, durable, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) remains a key challenge, as the catalysis at the anode accounts for major voltage losses in anion-exchange membrane water electrolyzers (AEMWE), particularly during operations at high current densities. Addressing this, Co₃O₄ emerges as a promising electrocatalyst, with its spinel structure allowing substitutions of cobalt with various transition metals to create more catalytically active sites and improve OER activities. In addition, advances in wet-chemistry synthesis allow careful control over the fabrication of the morphology of Co₃O₄ to achieve enhanced catalytic properties. This work presents Fe-incorporated Co₃O₄ with unique perforated sheet morphology as OER electrocatalysts. Even a minute amount of Fe in Co₃O₄ significantly improves the electrocatalytic activity, with an optimum Fe content at ∼4.7%. An all-platinum-group-metal-free (PGM-free) alkaline AEMWE with Fe-incorporated Co₃O₄ as the anode catalyst reaches a competitive current density of 1 A·cm^-2 at 1.95 V_cell, with a promising degradation rate of 0.4 mV·h^-1 after the initial deteriorations, primarily associated with the degradation of membranes and ionomer/binders. The PGM-free electrolyzer further demonstrates great potential for operation at a higher current density of 2 A·cm^-2 at 2.06 V_cell.