A high-performance Fe and nitrogen doped catalyst derived from diazoniapentaphene salt and phenolic resin mixture for oxygen reduction reaction

Abstract

A high-performance ORR catalyst has been synthesised by pyrolysis of quaternary nitrogen-containing 4a,8a-diazoniapentaphene dibromide (DAP), phenolic resin and FeBr₂ mixture. The catalyst (Fe/DAP) was characterized by XPS, SEM and TEM analysis. The ORR activity was studied using rotating ring–disk electrode voltammetry (RRDE) and the onset potential of ORR was found to be 0.95 V vs. RHE in 0.5 M H₂SO₄ solution, which is very close to that of the state-of-the-art Pt/C catalyst. The stability of the catalyst was studied using LD and SSD tests and found to be highly stable even after 11 110 potential-steps in the LD test. The kinetic and mechanistic analyses of the ORR on the catalyst indicate that the ORR, as a whole, follows a 4-electron (parallel) pathway. The relative changes in the nitrogen content after the durability test was estimated using N 1s XPS spectra which may be associated with the activity loss after the durability test. The loss of ORR activity was observed after the acid washing of the catalyst which suggests the role of Fe in the direct 4-electron reduction of O₂.