Co5.47N loaded N-doped carbon as an efficient bifunctional oxygen electrocatalyst for Zn-air battery
Highly active bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a pivotal role in Zn-air battery. The high cost, scarcity and instability of the precious metal based electrocatalysts of ORR and OER dramatically hamper the practical application in such clean-energy technique. Here we report a highly active Co5.47N loaded N-doped carbon (CoNMC), prepared by the direct NH3 annealing of the millet-CoCl2 mixture, which is a cheap and mass-producible biomass. The optimized product shows a superior ORR activity (half-wave potential of 0.81 V vs. RHE) and electrochemical stability (16.5 mV negative shift of half-wave potential after 2000 cycles) in alkaline media. Besides, it shows an appealing OER activity (operating potential at 10 mA cm−2 of 1.62 V vs. RHE). Such excellent electrochemical performance can be attributed to the formation of active Co5.47N nanoparticles, large specific surface area, abundant nitrogen active sites and high graphitization degree. When assembled in the Zn-air battery, the CoNMC based cell shows the comparable performance as Pt/C-RuO2 one.