A new 3D crosslinked polymer strategy for highly efficient oxygen reduction Fe–Nx/C catalysts

Abstract

The development of non-precious metal (NPM) catalysts with superior performance to replace Pt/C is critical for the wide application of proton-exchange membrane fuel cells. In this work, a three-dimensional crosslinked polymer with highly dispersed iron–nitrogen (Fe–N) coordination units and a mechanically robust framework is designed, synthesized and used as the sole precursor to obtain Fe-coordinated nitrogen-doped carbon (Fe–N_x/C) oxygen reduction reaction (ORR) catalysts. After optimization of the pyrolysis conditions and the use of SiO₂ templates to modify the catalyst nanostructure, a highly active catalyst of T-FeNC-800R is obtained, which exhibits a high half-wave potential of 751 mV in 0.1 M HClO₄. Besides, the T-FeNC-800R catalyst has an excellent ORR activity with onset and half-wave potentials of 1030 and 873 mV in 0.1 M KOH, respectively, which are higher than those of Pt/C (onset and half-wave potentials are 1009 and 855 mV vs. RHE, respectively). Moreover, this catalyst exhibits an almost four electron transfer process, high long-term stability, and better methanol tolerance than Pt/C catalyst in acidic media. The excellent oxygen reduction reaction performance of T-FeNC-800R can be attributed to the mesoporous structure, high specific surface area and a large number of exposed active sites. Moreover, the effects of the SiO₂ template, secondary pyrolysis and iron element on the catalytic performance are systematically discussed.