Sustainable chicken manure-derived carbon as a metal-free bifunctional electrocatalyst in Zn-air battery

Bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are needed to improve the kinetics of cathode reaction in rechargeable Zn-air batteries. In this work, using poultry waste (i.e., chicken manures) as the raw material, biomass-derived carbon catalyst is obtained via activation treatment followed by a facile pyrolysis method. The chicken manures impregnated by KOH solution and pyrolyzed at high temperature produce a porous carbon structure with a large surface area of 730.57 m2 g−1 that is beneficial for its catalytic activity. The metal-free carbon-based catalyst exhibits a promising bifunctional catalytic activity in 0.1 M KOH, showing an ORR onset potential of 0.84 V vs. RHE and an OER overpotential of 420 mV at 1 mA cm−2. The rechargeable Zn-air battery with chicken manure-derived carbon catalyst exhibits a peak power density of 30.05 mW cm−2 and excellent cycle stability performance up to 120 discharge/charge cycles. The strategy of converting animal waste into the bifunctional oxygen electrocatalysts demonstrates the viability of biomass waste conversion into value-added material.