Ultrathin amorphous MnO2 modified prawn shells-derived porous carbon towards robust oxygen electrocatalyst for rechargeable Zn-air battery

Precious metal-free bifunctional electrocatalysts with efficient performance to ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) are the prerequisite to the commercialization of rechargeable Zn-air battery (RZAB). Here, ultrathin amorphous MnO2 modified prawn shells-derived porous carbon (U–MnO2/PSNC) is designed and synthesized via a self-template assisted pyrolysis coupling in-situ redox reaction strategy. In this composite, the ultrathin amorphous MnO2 provides high surface defects and homogeneous catalytic active sites. The conductive prawn shells-derived porous carbon displays macro-meso-microporous structure, promoting electric conductivity and offering fast pathway for mass diffusion. With optimized composition, the U–MnO2-0.01/PSNC delivers an excellent bifunctional to ORR/OER with a small ΔE (bifunctional activity parameter) value of 0.776 V. Moreover, the RZAB equipped with U–MnO2-0.01/PSNC displays a considerable stability with narrow decay of battery efficiency (1.10%) for ∼334 h (500 cycles) at 10 mA cm−2. This work enlightens a new pathway to design cost-effective bifunctional electrocatalysts for metal-air battery.