CeO 2 / Co 3 O 4 p‐n Heterojunction as a Photo‐Responsive Bifunctional Electrocatalyst for Efficient Zinc‐Air Batteries

The introduction of semiconductor materials as bifunctional oxygen reduction/evolution reaction (ORR/OER) electrodes has been proved as an efficient way to improve the reaction kinetics and reduce the overpotential of ORR/OER during the discharge/charge process of rechargeable zinc‐air batteries (RZABs) by combining photochemistry and electrochemistry. Herein, a photo‐responsive bifunctional ORR/OER electrocatalyst with CeO 2 /Co 3 O 4 p‐n heterojunction has been constructed by a facile hydrothermal method for RZABs. Under illumination, photogenerated electrons have been demonstrated by the combination of in‐situ XPS and in‐situ XAS to transfer from Co 3 O 4 to CeO 2 , whereas the holes are in opposite directions, which is beneficial for the formation of built‐in electric field and in turn promoting the separation of photogenerated electron–hole pairs. Benefiting from the unique structural features, the resultant CeO 2 /Co 3 O 4 exhibits the photo‐enhanced ORR/OER performance with half‐wave potential of 0.794 V and overpotential of 360 mV at the current density of 10 mA cm −2 as well as remarkable RZABs performance with the maximum power density of 207.85 mW cm −2 and good round‐trip efficiency under illumination.