Dual Optimization of an Earth-Abundant Electrocatalyst for Sustainable Water Oxidation

The development of acidic proton exchange membrane water electrolyzers (PEMWEs) is limited by the need for scarce and costly noble metal catalysts for the oxygen evolution reaction (OER). Here, we use Ba-and Mn-codoped Co 3 O 4 as a model system to establish a dissolution-mediated reconstruction strategy for durable acidic OER catalysis. The optimized catalyst delivers an overpotential of 380 mV at 10 mA cm −2 in acid, remains stable for 375 h at 50 mA cm −2 in a three-electrode configuration, and sustains 160 h operation at 500 mA cm −2 in a PEMWE device. Mechanistic studies indicate that Mn enhances the intrinsic activity of Co sites, whereas Ba leaching during operation leads to the in situ formation of a BaSO 4 protective phase that suppresses metal dissolution. This work provides a strategy for developing stable earth-abundant electrocatalysts for acidic water oxidation.