Nonprecious-metal Fe/N/C Catalysts Prepared from π-Expanded Fe Salen Precursors toward an Efficient Oxygen Reduction Reaction

Article abstract of DOI:10.1002/cctc.201701629

Non-precious metal electrocatalysts are under investigation as alternatives to platinum-group metal electrocatalysts for the oxygen reduction reaction (ORR), which is required for cathode materials in fuel cells. Herein, we describe a new method for the synthesis of metal and nitrogen-containing carbon (M/N/C) catalysts with high ORR activity using π-expanded Fe(Salen) precursors. The Fe/N/C ORR catalysts were obtained by pyrolysis of a mixture of carbon support (Vulcan XC-72R) and the iron complex precursors. The Fe/N/C catalyst prepared from N,N'-bis(2-hydroxy-1-naphthylidene)-1,2-phenylenediamino-iron(III) chloride has an onset potential of 860 mV, which is positively shifted by 60 mV from that of the catalyst prepared from the simple Fe(Salen) complex. The catalyst promotes efficient four-electron reduction in the ORR. XAFS and XPS studies reveal that the Fe/N/C catalysts have atomically-dispersed iron active sites and that the activity depends on the high content of pyridinic nitrogen. This new methodology facilitates the design of non-precious metal-carbon catalysts with excellent ORR activity.