Impact of Highly Concentrated Alkaline Treatment on Mesostructured Cobalt Oxide for the Oxygen Evolution Reaction

Commercial alkaline water electrolysis cells typically use highly concentrate KOH as electrolyte, which strongly influences alteration of catalyst and its performance. Herein, the impact of alkaline treatment toward the structural alteration and electrochemical oxygen evolution reaction (OER) activity of well-defined ordered mesoporous Co₃O₄ is systematically studied. The overall morphology of mesostructured Co₃O₄ is relatively resilient to the exposure of highly concentrated alkaline solution up to 13 m KOH. The spectroscopic analyses, including in situ diffuse reflectance infrared spectroscopy, reveal the presence of carbonate-based species after the alkaline treatment due to impurities of the commercial KOH. The pre-treated samples exhibit a higher electrochemically active surface area, decreased charge transfer resistance, and increased current density from 103 to 155 mA cm⁻² at 1.7 V versus RHE. The in situ electrochemical Raman spectroscopy investigation supports formation of active CoOOH phase on KOH pre-treated Co₃O₄, which might play a key role toward enhanced OER activity.