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

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-N x active sites are protected and the micro-mesoporous structures are constructed. Benefiting from the synergistic effects of the high loaded contents of Fe-N x active sites and the hierarchically porous nanostructure, Fe–N/C-SA exhibits the excellent electrocatalytic performance over ORR with E 1/2 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. • Fabrication of Fe single-atom hierarchical porous carbon nanospheres. • Enhanced ORR performance by high Fe-N x content and hierarchical porous structure. • The Zn-air battery assembled with Fe–N/C-SA exhibits excellent performance. • A new insight to design of single-atom catalysts with non-precious metals.