Novel Route to Fe-Based Cathode as an Efficient Bifunctional Catalysts for Rechargeable Zn-Air Battery

Efficient bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts are of great importance for rechargeable metal-air batteries. Herein, FeNx/C catalysts are synthesized by pyrolysis of thiourea and agarose containing alpha-Fe2O3 nanoplate as Fe precursor, where alpha-Fe2O3 nanoplate can prevent the aggregation of carbon sheets to effectively improve the specific surface area during the carbonization process. The FeNx/C-700-20 catalyst displays excellent catalytic performance for both ORR and OER activity in alkaline conditions with more positive onset potential (1.1 V vs the reversible hydrogen electrode) and half-wave potential, higher stability, and stronger methanol tolerance in alkaline solution, which are all superior to that of the commercial Pt/C catalyst. In this study, the detailed analyses demonstrate that the coexistence of Fe-based species and high content of Fe-N-x both play an important role for the catalytic activity. Furthermore, FeNx/C-700-20 as cathode catalyst in Zn-air battery possesses higher charge-discharge stability and power density compared with that of commercial Pt/C catalyst, displaying great potential in practical implementation of for the rechargeable energy devices.