Porous carbon layers wrapped CoFe alloy for ultrastable Zn-Air batteries exceeding 20,000 charging-discharging cycles

Developing high active and stable bifunctional electrocatalysts towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for the development of rechargeable Zn-air batteries. Herein, a facile strategy to synthesize the porous carbon layers wrapped CoFe alloy (C/CoFe) through the pyrolysis of a homogeneous mixture containing Co, Fe ions and N-doped carbon quantum dots (N-doped CQDs) was reported. The prepared carbon layers with multi-level pore structures provides more active sites and optimizes the homogeneity of the electron and mass transport. In addition, the carbon layers, which is doped by Co/Fe/N atoms, is responsible for high ORR activity, while the CoFe alloy plays a vital role in OER performance. The as-synthesized catalyst exhibits an excellent bifunctionality for electrochemical oxygen reactions, which is comparable to the commercial Pt/C and IrO2 benchmarks. Owing to the carbon layers protects CoFe alloy nanoparticles from the harsh environment, the rechargeable Zn–air battery with the C/CoFe catalyst delivers excellent stability during 20,000 charging-discharging cycles.