A Highly Active Oxygen Reduction Composite Electrocatalyst of Fe3C with a N, F Dual-Doped Carbon Layer Hide

Abstract

In low-temperature fuel cells, effective and low-cost electrocatalysts for oxygen reduction reaction (ORR) have played an critical role in achieving a practical performance. In this study, a class of non-precious composite electrocatalyst of Fe3C nanoparticles hided in N, F dual-doped carbon layer (Fe3C@NFC) for ORR is successfully synthesized through a facile strategy by heat-treating iron chloride, melamine hydrogen fluoride together with carbon black at high temperature. The obtained Fe3C@NFC pyrolyzed at 800 °C (Fe3C@NFC800) shows the best ORR electrocatalytic activity, where its ORR peak potential and half-wave potential are 0.908 V and 0.882 V, respectively, and the ORR process is dominated by a major direct 4-electron reaction pathway (n = 3.8–4.0) in alkaline solution. Furthermore, it owns more methanol tolerance and stability than those of 20 wt% Pt/C. The high ORR electrocatalytic performance of this Fe3C@NFC800 origins from the synergistic effect between Fe3C crystal and N, F dual-doped carbon layer to form a core–shell structure, having a specific surface area of 786 m2 g−1 with high defect degree (ID/IG is ∼1.2), where Fe3C species are beneficial to the formation of pyridinic N, pyrrolic N and graphitic N for enhancing catalytic ORR process.