Fe-N4/Co-N4 active sites engineered porous carbon with encapsulated FeCo alloy as an efficient bifunctional catalyst for rechargeable zinc-air battery

Abstract

Design and synthesis of earth-abundant elements-based electrocatalysts with sufficient activity and stability remain challenging for oxygen-involved electrochemical energy conversion and storage devices. In this work, catalyst with simultaneously engineered Fe-N4 and Co-N4 active sites and graphitic carbon multilayer-encapsulated FeCo alloy is developed by pyrolysis of metal salts doped G-g-C3N4. The obtained composite material exhibits promising catalytic activity and good stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte, as evidenced by the positive shift of half-wave potential by 44 mV compared to 20% Pt/C for ORR and the potential of 1.596 V at current density of 10 mAcm−2 for OER. In addition, the thus-assembled rechargeable zinc-air battery using the synthesized material as cathode delivers a maximum power density of 311.2 mWcm−2 with an open circuit potential of 1.51 V and a long-term cycling stability. DFT calculation results indicate that catalyst with composite active sites displays smaller energy barrier than that with single active site.