Hierarchical 3D porous carbon with facilely accessible Fe-N4 single-atom sites for Zn-air batteries†

Abstract

Here, we report a highly efficient ORR electrocatalyst with Fe-N4 active sites uniformly dispersed on a three-dimensional (3D) interconnected porous nitrogen-doped carbon network synthesized by pyrolyzing SiO2@ZIF-8 composites loaded with iron salts. The as-prepared single-atom Fe 3D-ordered mesoporous carbon (SA-Fe-3DOMC) possesses a high specific surface area of 1357.8 m2 g−1 and a high Fe loading of 0.84 wt% as well. Benefiting from these favourable structural properties, SA-Fe-3DOMC exhibits a superior ORR half-wave potential (E1/2) of 0.901 V and negligible activity loss (only 3 mV) after 10 000 cycles in alkaline media, surpassing the state-of-the-art Pt/C electrocatalyst. Particularly, an integrated zinc-air battery with SA-Fe-3DOMC as the air electrode shows a remarkable peak power density (140 mW cm−2) and a high specific capacity (786.6 mA h g−1), demonstrating great potential for practical application.