关键词: Fe/N/C催化剂, 氧还原反应, 活性位, 吡啶型N, Fe-N物种

Abstract: The development of Fe/N/C electrocatalyst for oxygen reduction reaction (ORR) is vital for the large-scale applications of proton exchange membrane fuel cells. Understanding the active site structure will contribute to the rational design of highly active catalysts. In this study, the as-prepared Fe/N/C catalyst based on poly-m-phenylenediamine (PmPDA-FeN_x/C) catalyst with the high ORR activity was subjected to the high-temperature heat treatment again at 1000 ~1500 ^oC. The degradation of in the ORR activity of PmPDA-FeN_x/C by with various heat treatments was correlated to the change of elemental compositions, chemical states and textural properties. As the temperature elevated, the Fe atoms aggregated to form nanoparticles, while the gaseous N-containing species volatilized and the amount of N contents decreased, resulting in the destruction of active sites. The XPS analysis revealed that the content of N species with low binding energy show good positive correlation with the ORR kinetic current of catalyst, demonstrating that the pyridinic N and Fe-N species are probably main components of active sites and contribute to the high ORR activity. This study provides a new strategy to investigate the nature of active centre.

Key words: Fe/N/C electrocatalyst, oxygen reduction reaction, active sites, pyridinic N, Fe-N species