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 CeO 2 and spinel structure Co 3 O 4 (CeO 2 /Co 3 O 4 ) by a built-in p – n heterojunction. The strongly coupled p – n heterojunction interface allows a rapid interfacial charge transfer from CeO 2 to Co 3 O 4, which leads to a high concentration of oxygen vacancies and the generation of Co 2+ octahedral (Co 2+ (O h )) sites from the reduction of Co 3+ (O h ) at the CeO 2 /Co 3 O 4 interface. Consequently, the CeO 2 /Co 3 O 4 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.