CeO2 quantum dots embedded in 3D hierarchical porous foliaceous N-doped carbon as an efficient oxygen reduction electrocatalyst for metal-air battery

•A novel CeO2 quantum dots@NC was prepared using a self-sacrifice template method.•CeO2 @NC possesses a 3D hierarchical foliaceous framework and more oxygen vacancies.•The ORR performance of CeO2 @NC-900-2 outperforms that of commercial Pt/C catalyst.•The metal-air battery using CeO2 @NC-900-2 catalyst exhibits excellent performance.