Do magnetically modified PtFe/C catalysts perform better in methanol electrooxidation?

Abstract

Motivated by the demonstrated magnetic field effect on the oxygen reduction reaction in polymer electrolyte fuel cells (PEMFC), a number of PtFe/C catalysts with different magnetic characteristics were prepared and tested for methanol electrooxidation in acidic solutions at room temperature. The catalysts were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray microanalysis (EDX) and vibrating sample magnetometry (VSM). The activity and CO tolerance of the catalysts in the methanol oxidation reaction (MOR) was measured by cyclic voltammetry and anodic CO stripping voltammetry, respectively. Heat treatment transformed the as-prepared PtFe/C from a face-centered cubic (fcc) structure into a face-centered tetragonal (fct) structure. Vibrating sample magnetometer (VSM) measurements confirmed the as-prepared PtFe/C as superparamagnetic, and the heat-treated catalysts as ferromagnetic. The heat-treated ferromagnetic catalysts were, however, low in specific mass activity and showed no improvement in CO tolerance relative to the as-prepared one. These results led us to conclude that the magnetic modification of catalysts through heat treatment have no practical contributions to the catalysis of MOR. © 2006 Elsevier Ltd. All rights reserved.