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−Nx moieties 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−Nx sites in carbon matrix, but also generate more micropores for enlarging BET specific surface area (up to 1500 m2·g−1). 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·cm−2 and a specific capacity of 719 mA·h·g−1Zn outperformed commercial Pt/C catalyst, holding encouraging promise for the application in metal-air batteries.