Pt/Fe/N/C Catalyst with Improved Activity and Stability Toward Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cell

Abstract

Proton exchange membrane fuel cell (PEMFC) is promising in transportation applications due to its advantages such as cleanliness, high efficiency, easy operation, low working temperature and fast start-up[1]. Pt-based catalysts have been accepted as oxygen reduction reaction (ORR) catalyst in PEMFC since their high activity and stability. In last decade, FeN/C catalysts have received much attention since their excellent activity toward ORR. However, the high price and rare reserves of platinum, as well as the poor stability of FeN/C restrict the large-scale application of Pt-based and FeN/C catalysts[2-3]. In this work, platinum-based catalysts with FeN co-doped carbon support were prepared by ethylene glycol reduction method. Their activity and stability toward ORR were investigated by electrochemical techniques. The structure and physical characteristics of catalysts and their supports were studied by an array of techniques such as Brunauer-Emmet-Teller (BET)surface area and pore size distribution measurements, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and etc.The electrochemical results showed that Pt/FeNGR using Fe, N co-doped graphene as carbon support had best initial ORR activity but poor stability. While Pt/FeNBP, using FeNBP which obtained by pyrolyzed the mixture of Black Pearl 2000 (BP), iron acetate and 1,10-phenanthroline at 900°C in amonia for 10 minutes, had much better stability than commercial Pt/C catalyst.Combined the results obtained from electrochemical techniques, BET, TEM, XPS, etc, the doping of Fe and N on carbon materials modified their physical characteristics such as surface area, defects, types of elements and functional group on surface, etc. The dispersion and size of platinum particles, the interaction between platinum particles and carbon support were improved due to the modification of carbon supports. Most of surface nitrogen in Pt/Fe(N)GR existed as pyridine N and N-Fe may be the key factor for its better initial ORR activity. The large surface area of BP, and the most of surface nitrogen existed in Pt/Fe(N)BP as graphite-N may be crucial to its best stability.