Microwave heated polyol synthesis of carbon-supported PtSn nanoparticles for methanol electrooxidation

PtSn nanoparticles supported on Vulcan XC-72 carbon were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The PtSn nanoparticles, which were uniformly dispersed on carbon, were 2-7 nm in diameter. All Pt/C and PtSn/C catalysts (except Pt₃₅Sn₆₅/C) displayed the characteristic diffraction peaks of a Pt face-centered cubic (fcc) crystal structure, whereas the Pt₃₅Sn₆₅/C catalyst showed the X-ray diffraction pattern of Pt face-centered cubic (fcc) and cassiterite SnO₂ phases. XPS analysis revealed that the catalysts contained mostly Pt(0) and Sn(IV), with traces of Pt(II), Pt(IV) and Sn(0). The electro-oxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results showed that the alloy catalyst was catalytically more active and durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell using the Vulcan carbon-supported PtSn alloy as anode catalyst showed high power density.