3D Rosa centifolia-like CeO2 encapsulated with N-doped carbon as an enhanced electrocatalyst for Zn-air batteries.

Reasonable design and synthesis of high-efficiency rare earth oxides-based materials as alternatives to noble-metal catalysts are of great significance for oxygen electrocatalysis. Herein, we report three-dimension (3D) Rosa centifolia-like CeO2 encapsulated with N-doped carbon (NC) composites (CeO2@NC) for enhancing oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities. This synthetic method allows CeO2 to tune the oxygen vacancy concentration and electronic structure of a series of CeO2@NC catalysts due to its large oxygen-storage-capacity (OSC) property. Moreover, benefiting from the exposed active sites in NC as well as the synergy between CeO2 and NC, among as-prepared samples, the resultant CeO2@NC-900 delivers a half-wave potential (E1/2) of 0.854 V, which is more positive compared with counterpart of NC-900 (0.806 V) and even comparable to that of commercial Pt/C catalyst (0.855 V). This indicates that the ORR electrocatalytic activity of CeO2@NC-900 is significantly improved. Meanwhile, CeO2@NC-900 exhibits satisfactory performance toward OER. For practical application, the CeO2@NC-900 involved rechargeable Zn-air battery possesses excellent energy efficiency, superior stability, and large energy density (666.1 Wh kgZn-1 at 5 mA cm-2). This approach provides a valid way to develop advanced rare earth oxides-based materials for energy applications.