Study On Microstructure Characterization And Electrocatalytic Activities Of Pt-sn/cms

Platinum is the most effective catalyst of direct methanol fuel cells (DMFC) electrode so far. The improvement of electrocatalysis activity and CO oxidation are key points for electrocatalysis of DMFC. On one hand, intermediate(CO) will be strongly adsorbed on Pt in methanol oxidation so that the catalytic activity of Pt reduces. On the other hand, Pt is comparatively expensive as noble metal. So many scholars are studying Pt-M binary catalyst in order to overcome insufficiency of monobasic catalyst. The cost of Sn is cheap, and electrochemical activity of Pt-Sn/C is better, so it is a hot topic in research field.In this paper, PtSn nanoparticles were loaded on Carbon Microspheres(CMS) with impregnation-reduction method. Compare with Pt/CMS, the composition was characterized by X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), X-ray diffraction (XRD), High resolution transmission electronmicroscopy (HRTEM) and cyclic voltammetry (CV).The results show that:1.Pt-Sn/CMS catalyst was perpared by impregnation-reduction method. The nanoparticles are well dispersed on the surface of the CMS, and mean particle diameter is 4nm. 2. XRD, XPS indicated that the addition of Sn was mostly in form of both PtSn alloy and SnO₂ in Pt-Sn/CMS catalyst.3. The cyclic voltammetry shows electrocatalysis activity of Pt-Sn/CMS is better than that of Pt/CMS. The results suggest that the presence of Sn, which changes the Pt lattice parameter, allows methanol to be adsorbed and dissociated at lower potentials than that observed on the commercial Pt/CMS catalyst. The Sn sites are always free to adsorb OHads, which prefer to be adsorbed mostly onto Sn sites rather than on Pt sites. Moreover, Sn or Sn oxide are able to form oxygen-containing species at lower overpotentials than Pt. Therefore, Sn or Sn oxide improves the methanol oxidation at lower potentials and increases the reaction rate.