Novel highly active and selective Fe-N-C oxygen reduction electrocatalysts derived from in-situ polymerization pyrolysis

Abstract

Among several candidates considered to replace expensive platinum based catalysts for oxidation reduction reaction (ORR) in fuel cells, iron-nitrogen-carbon (Fe-N-C) composites attract the most interest. In this work, we design a novel method to prepare Fe-N-C catalysts for ORR in both acid and alkaline media. It involves initial polymerization of different amino-pyridines to form a C-N-C backbone, followed by their high-temperature pyrolysis on silica template, HF etching and second heat treatment in ammonia. Polymerization of 2-amino-6-methylpyridine and 2,6-diaminopyridine was done by in-situ and ex-situ templating methods. The catalysts synthesized by this method possess half-wave potentials of ~ 0.88V versus RHE in O2 saturated 1M KOH electrolyte, and the best catalyst based on 2-amino-6-methylpyridine was seen to achieve an E1/2 greater than 0.7V in the O2 saturated 0.5M sulfuric acid electrolyte. Importantly, the catalysts prepared by this novel method exhibit remarkably low peroxide yield in both acid and base media (< 4% and < 1.3%, respectively) as revealed by rotating ring disk electrode (RRDE) studies.