A new strategy to immobilize molecular Fe sites into a cationic polymer to fabricate an oxygen reduction catalyst

Abstract

We report a new method of generating catalytic active sites for the oxygen reduction reaction (ORR) through the immobilization of molecular Fe sites in a cationic polymer (CXL-HCP-Fe) via counterion exchange combined with pyrolysis. Pyrolysis at different temperatures leads to the formation of novel non-precious metal catalysts consisting of Fe3C nanoparticles encapsulated in porous graphitic carbon materials (CXL-HCP-Fe-t). Electrochemical characterization shows that the CXL-HCP-Fe-900 obtained at a pyrolysis temperature of 900 °C has excellent ORR electrocatalytic activity that is comparable to the commercial Pt/C catalyst, and even better catalytic durability. In addition, 57Fe Mössbauer spectroscopy, inductively coupled plasma spectrometry and X-ray diffraction measurements show that Fe3C-based active sites with relatively high crystallinity species and content contribute to the high ORR catalytic activity of CXL-HCP-Fe-900.