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 O-2 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 Delta E 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 (similar to 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.