High oxygen reduction reaction activity on various iron loading of Fe-PANI/C catalyst for PEM fuel cell

Abstract

Herein, the iron loading of Fe-PANI/C is systematically studied to understand the changes in oxygen reduction reaction (ORR) activity related to structure, oxidation state, and coordination number. First, Fe-PANI/C was prepared via the chemical oxidative polymerization of polyaniline (PANI) and then physically mixed with FeCl2·4H2O in an ethanol solution, namely, with 4 wt.%, 7 wt.%, and 10 wt.% iron loading. The Fe-PANI/C with 7 wt.% iron loading exhibited the highest ORR activity with an electron transfer number of 3.98. This is attributed to the proportional amount of iron content that can improve ORR activity. The major nitrogen functional group of 7 wt.% Fe-PANI/C is pyrolic N by about 44.03%. Furthermore, X-ray absorption near-edge structure (XANES) analysis shows that all catalysts containing Fe2+ have the oxidation state of Fe3+. The stability test of 7 wt.% PANI/C has 55-mV decay in the acid solution.