Co-doped CeO 2 /N-C nanorods as a bifunctional oxygen electrocatalyst and its application in rechargeable Zn-air batteries.

The development of electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high-activity and atability still remain great challenges for rechargeable Zn-air batteries. Herein, a new type of Co-doped Ce-N-C bifunctional electrocatalyst has been synthesized through a simple two-step method, which realizes the high dispersion of Co ₃ O ₄ on the CeO ₂ carbon frame and stabilizes its specific surface area. Benefiting from the synergistic interaction between Co ₃ O ₄ and CeO ₂ , the conductivity of the electrocatalyst is improved and the oxygen reduction reaction/oxygen storage properties are promoted. The resultant Co ₃ O ₄ -CeO ₂ @N-C catalyst shows remarkable ORR activity with the high initial potential ( E ₀  = 0.8 V), the large limiting current density ( j _L  = 6 mA cm ^-2 ), and a low Tafel slope (81 mV dec ^-1 ). In full cell tests, Co ₃ O ₄ -CeO ₂ @NC as the oxygen electrode exhibites superior charge/discharge capacity and excellent cycle stability. The assembled Zn-air battery achieves a maximum power density of 110 mW cm ^-2 at a current density of 180 mA cm ^-2 , and a high specific capacity of 780 mAh g ^-1 at a discharge current density of 10 mA cm ^-2 .
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