Robust template-activator cooperated pyrolysis enabling hierarchically porous honeycombed defective carbon as highly-efficient metal-free bifunctional electrocatalyst for Zn-air batteries

Nonprecious bifunctional electrocatalysts with satisfactory cost and high catalytic performance toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential to promote the commercialization of metal-air batteries. Herein, 3D honeycombed hierarchical porous N, O-doping carbon (HHPC) is fabricated via a facile and scalable strategy of hard template-activator assisted pyrolysis. The obtained HHPC displays unique macro-meso-microporous framework, N, O-codoped effect and order-disorder hybrid characteristic, providing sufficient space for O2 and electrolyte transport, abundant defect sites, enhanced electronic conductivity and stability for oxygen conversion reaction. As such, the HHPC exhibits superior bifunctional electrocatalytic activity with a narrow ΔE value of 0.8 V. And a long-term stability and reversibility with a narrow voltage gap increasing of 0.09 V over 1165 cycles (∼388 h) at 10 mA cm−2 are achieved in the HHPC-based rechargeable Zn-air battery, outperforming most of the state-of-the-art carbon-based Zn-air batteries.