CeO2-Induced Interfacial Co2+ Octahedral Sites and Oxygen Vacancies for Water Oxidation

Electrocatalytic oxygen evolution reaction (OER) is a key process in electrochemical energy conversion and storage. Cobalt-containing spinel oxides are promising candidates for OER, but suffer from cation deficiency during OER, because of the high stability and reversibility of the spinel structure. Herein, we combine catalytically inactive CeO2 and spinel structure Co3O4 (CeO2/Co3O4) by a built-in p–n heterojunction. The strongly coupled p–n heterojunction interface allows a rapid interfacial charge transfer from CeO2 to Co3O4, which leads to a high concentration of oxygen vacancies and the generation of Co2+ octahedral (Co2+(Oh)) sites from the reduction of Co3+(Oh) at the CeO2/Co3O4 interface. Consequently, the CeO2/Co3O4 interface with the optimal ratio of Ce/Co exhibits high OER activity with an overpotential of only 265 mV at the current density of 10 mA cm–2, a Tafel slope of 68.1 mV dec–1, and long-term durability in an alkaline medium.