Fabrication of self-standing carbon catalyst loaded with CoFe nanoparticles embedded carbon nanotube complex for oxygen electrocatalysis and rechargeable zinc-air battery.

Carbon-based catalysts with free-standing structure are essential for rechargeable zinc-air battery as electrodes, which can avoid the side effects brought by organic binder. However, the current preparation methods still can be improved for faster preparation process and morphology control. In this study, we reported a fabrication strategy of self-standing carbon catalyst loaded with CoFe nanoparticles and carbon nanotube as air electrodes for liquid rechargeable zinc-air battery. With a rapidly prepared PAN film used as substrate, ZIF with both Fe and Co elements are loading as active site precursor, which a composite structure of CoFe nanoparticles and carbon nanotube will form on the free-standing catalyst surface after the carbonization process. In this structure, the carbonated PAN film substrate will provide rich conductive paths to promote electron transfer during the reaction process, and the active sites on the surface can promote the contact between intermediates and active sites. The optimized catalyst FeCo@CP-1:1 has the best ORR/OER bifunctional catalytic activity, which exhibits a halfwave potential (E) of 0.89 V (vs. RHE) for the ORR and a potential of 1.47 V at a current density of 10 mA cm (E) for the OER. It can be attributed to the excellent ORR catalytic activity of CoFe nanoparticles and its reconstruction process in OER. Furthermore, FeCo@CP-1:1 exhibits a power density of 154 mW cm and long cyclic stability in liquid ZABs application. This research lays a practical foundation for design and synthesis of free-standing carbon catalyst.