Encapsulating Cobalt Nanoparticles in Interconnected N-Doped Hollow Carbon Nanofibers with Enriched Co-N-C Moiety for Enhanced Oxygen Electrocatalysis in Zn-Air Batteries

Rational design of bifunctional efficient electrocatalysts for both oxygen reduction (ORR) and oxygen evolution reactions (OER) is desirable-while highly challenging-for development of rechargeable metal-air batteries. Herein, an efficient bifunctional electrocatalyst is designed and fabricated by encapsulating Co nanoparticles in interconnected N-doped hollow porous carbon nanofibers (designated as Co@N-C/PCNF) using an ultrafast high-temperature shock technology. Benefiting from the synergistic effect and intrinsic activity of the Co-N-C moiety, as well as porous structure of carbon nanofibers, the Co@N-C/PCNF composite shows high bifunctional electrocatalytic activities for both OER (289 mV at 10 mA cm(-2)) and ORR (half-wave potential of 0.85 V). The Co-N-C moiety in the composite can modulate the local environmental and electrical structure of the catalysts, thus optimizing the adsorption/desorption kinetics and decreasing the reaction barriers for promoting the reversible oxygen electrocatalysis. Co@N-C/PCNF-based aqueous Zn-air batteries (AZAB) provide high power density of 292 mW cm(-2), and the assembled flexible ZAB can power wearable devices.