Surface-confinement assisted synthesis of nitrogen-rich single atom Fe-N/C electrocatalyst with dual nitrogen sources for enhanced oxygen reduction reaction.

The utilization of earth abundant iron and nitrogen doped carbon as a precious-metal-free electrocatalyst for oxygen reduction reaction (ORR) significantly depends on the rational design and construction of desired Fe-Nmoieties on carbon substrates, which however remains an enormous challenge. Herein a typical nanoporous nitrogen-rich single atom Fe-N/C electrocatalyst on carbon nanotube (NR-CNT@FeN-PC) was successfully prepared by using CNT as carbon substrate, polyaniline (PANI) and dicyandiamine (DCD) as binary nitrogen sources and silica-confinement-assisted pyrolysis, which not only facilitate rich N-doping for the inhibition of the Fe agglomeration and the formation of single atom Fe-Nsites in carbon matrix, but also generate more micropores for enlarging BET specific surface area (up to 1500 m·g). Benefiting from the advanced composition, nanoporous structure and surface hydrophilicity to guarantee the sufficient accessible active sites for ORR, the NR-CNT@FeN-PC catalyst under optimized conditions delivers prominent ORR performance with a half-wave potential (0.88 V versus RHE) surpass commercial Pt/C catalyst by 20 mV in alkaline electrolyte. When assembled in a home-made Zn-air battery device as cathodic catalyst, it achieved a maximum output power density of 246 mW·cmand a specific capacity of 719 mA·h·goutperformed commercial Pt/C catalyst, holding encouraging promise for the application in metal-air batteries.