Nanostructured Pt-Fe/C cathode catalysts for direct methanol fuel cell: The effect of catalyst composition

A series of carbon supported Pt-Fe bimetallic nanocatalysts (Pt-Fe/C) with varying Pt:Fe ratio were prepared by a modified ethylene glycol (EG) method, and then heat-treated under H-2-Ar (10 vol%-H-2) atmosphere at 900 degrees C. The Pt-Fe/C catalysts were characterized by X-ray diffraction (XRD), transmission electron spectroscopy (TEM), energy dispersive analysis by X-rays (EDX) and induced coupled plasma-atomic emission spectroscopy (ICP-AES). XRD analysis shows that Pt-Fe/C catalysts have small crystalline particles and form better Pt-Fe alloy structure with Fe amount increasing. TEM images evidence that small Pt-Fe nanoparticles homogeneously deposited on carbon support and addition of Fe can effectively prevent Pt particles agglomeration. EDX and ICP-AES show that Fe precursor cannot be fully reduced and deposited on carbon support through the adopted EG reduction approach. The electrochemical surface area of Pt-Fe/C catalyst obtained through hydrogen desorption areas in the CV curve increases with Fe atomic percentage increasing from 0 to ca. 50%, and then decreases with more Fe in the Pt-Fe/C catalyst. RDE tests show that the Pt-Fe/C with a Pt:Fe ratio of 1.2:1 and an optimized lattice parameter of around 3.894 angstrom has the highest mass activity and specific activity to oxygen reduction reaction (ORR). As cathode catalyst, this Pt-Fe/C (Pt:Fe ratio of 1.2:1) exhibits higher direct methanol fuel cell performance at 90 degrees C than Pt/C and other Pt-Fe/C catalysts, this could be attributed to its smaller particle size and better Pt-Fe alloy structure. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.