Theoretical Investigation of the Activity of Cobalt Oxides for the Electrochemical Oxidation of Water

The presence of layered cobalt oxides has been identified experimentally in Co-based anodes under oxygen-evolving conditions. In this work, we report the results of theoretical investigations of the relative stability of layered and spinel bulk phases of Co oxides, as well as the stability of selected surfaces as a function of applied potential and pH. We then study the oxygen evolution reaction (OER) on these surfaces and obtain activity trends at experimentally relevant electro-chemical conditions. Our calculated volume Pourbaix diagram shows that β-CoOOH is the active phase where the OER occurs in alkaline media. We calculate relative surface stabilities and adsorbate coverages of the most stable low-index surfaces of β-CoOOH: (0001), (011̅2), and (101̅4). We find that at low applied potentials, the (101̅4) surface is the most stable, while the (011̅2) surface is the more stable at higher potentials. Next, we compare the theoretical overpotentials for all three surfaces and find that the (101̅4) surfac...