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 H2–Ar (10 vol%-H2) atmosphere at 900 °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 Å 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 °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.