Construction of hierarchically porous carbon spheres supported nonprecious metal single-atom electrocatalysts for oxygen reduction reaction

Abstract

Design of a highly efficient nonprecious metal electrocatalysts towards oxygen reduction reaction (ORR) is essential for the commercialization of sustainable and economical energy conversion and storage devices containing metal-air batteries and fuel cells. Herein, we present a facile strategy to fabricate the hierarchical porous carbon nanospheres with isolated single-atom iron sites by using the dual-template method of combination of triblock polymers F127 and silica as soft and hard templates, respectively. Owing to the simultaneous hydrolysis of tetraethoxysilane (TEOS) and polymerization of 2,6-diaminopyridine (DAP), the Fe-Nx active sites are protected and the micro-mesoporous structures are constructed. Benefiting from the synergistic effects of the high loaded contents of Fe-Nx active sites and the hierarchically porous nanostructure, Fe–N/C-SA exhibits the excellent electrocatalytic performance over ORR with E1/2 of 0.89 V, which is superior than that of Pt/C (0.84 V). In addition, the as-obtained catalyst exhibits excellent stability and methanol tolerance compared to commercial Pt/C catalysts. Most importantly, the Zn-air battery assembled with Fe–N/C-SA exhibits a gratifying peak power density of 265.0 mW cm−2, large specific capacity of 798.2 mAh g−1, excellent long-term stability and remarkable rate capability.