Co 2 P@N,P-Codoped Carbon Nanofiber as a Free-Standing Air Electrode for Zn-Air Batteries: Synergy Effects of CoN x Satellite Shells.

Here first a free-standing electrode composed of cobalt phosphides (Co2P) supported by cobalt nitrides moieties (CoNx) and N, P-codoped porous carbon nanofiber (CNF) in one-step electrospinning of environmentally friendly benign phosphorous precursors is reported. Physiochemical characterization revealed the symbiotic relationship between Co2P crystal and surrounding nanometer size CoNx moieties embedded in N, P-codoped porous carbon matrix. The Co2P@CNF shows high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance owing to the synergistic effect of Co2P nanocrystals, and the neighboring CoNx moieties which have the optimum binding strength of reactants and facilitates the mass transfer. The free-standing Co2P@CNF air-cathode based Zn-air batteries deliver a power density of 121 mW cm-2 at a voltage of 0.76 V. The overall overpotential of Co2P@CNF based Zn-air batteries can be significantly reduced, with low discharge-charge voltage gap (0.81 V at 10 mA cm-2) and high cycling stability which outperforms the benchmark Pt/C based Zn-air batteries. The one-step electrospinning method can serve as a universal platform to develop other high-performance transition metal phosphide catalysts benefited from the synergy effect of transition nitrides satellites shell. The free-standing and flexible properties of Co2P@CNF make it a potential power for wearable electronic devices.