Efficient hierarchically synthesized Fe2P nanoparticles embedded in an N,P-doped mesoporous carbon catalyst for the oxygen reduction reaction

Abstract

The construction of nonprecious metal catalysts for the oxygen reduction reaction (ORR) is highly desirable but remains as a key challenge for fuel cells and metal–air batteries. Herein, we designed and synthesized novel Fe₂P nanoparticles embedded in an N,P co-doped mesoporous carbon catalyst (Fe₂P/NPC) through direct pyrolysis of o-methylaniline in the presence of FeCl₃·6H₂O, H₃PO₄, silica nanospheres, and hexadecyltrimethyl ammonium bromide (CTAB) micelles. Transmission electron microscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction and X-ray photoelectron spectroscopy measurements demonstrated that the obtained three-dimensional mesoporous Fe₂P/NPC catalyst possessed a considerable specific surface area of 785 m² g⁻¹ with high contents of Fe₂P nanoparticles, pyridinic N, and graphitic N species. Electrochemical evaluations showed that the formed Fe₂P/NPC exhibited superior ORR performance to Pt/C in terms of a comparable onset potential (−0.01 V vs. Ag/AgCl electrode), about 20 mV higher half-wave potential, excellent stability and remarkable methanol tolerance in alkaline media. The synergistic effect of pyridinic N, graphitic N and Fe₂P species together with its three-dimensional porous structure contribute to the impressive ORR performance. This research, most importantly, provides new clues to the rational development of cost-effective FeP_x-based catalysts for the ORR.