Selective Electrochemical Alkaline Seawater Oxidation Catalyzed by Cobalt Carbonate Hydroxide Nanorod Arrays with Sequential Proton-Electron Transfer Properties

Abstract

Seawater oxygen evolution is one of the promising energy conversion technologies for large-scale renewable energy storage. It requires efficient catalysts to accelerate the oxygen evolution reaction (OER) for sustained water oxidation, avoiding chlorine evolution under acidic conditions or hypochlorite formation in alkaline solutions. Conventional metal oxide-based OER catalysts follow the adsorbate evolution mechanism that involves concerted proton-electron transfer steps at the active sites. Thus, on the scale of reversible hydrogen electrode, their catalytic activity is independent of the pH of electrolytes. In the present study, nanostructured cobalt carbonate hydroxide (CoCH) with sequential proton-electron transfer properties was tested as a catalyst for seawater oxygen evolution. CoCH exhibited pH-dependent water oxidation activities, thereby providing larger potential and current operating windows for selective water oxidation compared to the catalysts with pH-independent OER activities. The operating window can be further expanded by increasing the pH of the electrolyte.