Electrochemical characterization of PtGe and PtIn catalysts supported on carbonaceous materials for DMFC.

N.S. VEIZAGA(1,*), V.A. PAGANIN(2), T.A. ROCHA(2), O.A. SCELZA(1), S.R. DE MIGUEL(1), E.R. GONZALEZ(2).

Simposio; XIX Simpósio Brasileiro de Eletroquímica e Eletroanalítica; 2013

The anodic methanol oxidation over platinum electrodes in an acid electrolite is a catalytic reaction producing CO2 and six electrons per methanol molecule: CH3OH + H2O à CO2 + 6H+ + 6e-. The aim of this paper is to characterize and evaluate little-studied bimetalic systems supported over carbonaceous supports. PtGe and PtIn electrocatalysts were prepared by a reduction-deposition method in liquid phase using NaBH4 and ethylene glycol as reducing agents, the Pt load being 17% and Ge/Pt or In/Pt molar ratios of 0.2 and 0.33. The supports were commercial Vulcan carbon, multi-walled carbon nanotubes and mesoporous carbon. The catalysts were characterized by TPR, XRD, XPS, H2 chemisorption, CO stripping and testing in DMFC cells. From chemical analysis, TPR and XPS results, it could be concluded that the reduction-deposition in liquid phase with NaBH4 or ethylene glycol leads to a practically total reduction of Pt to zerovalent state (about 70-80%), whereas the second metal (Ge or In) remains mainly in oxidized state. By CO stripping, it could be observed a certain promotional effect of Ge (see Figure) on Pt, which would allow the adsorbed CO to be oxidized at lower potentials than with monometallic Pt. Similar results were obtained with PtIn catalysts. Besides catalysts showing CO oxidation at lower potentials were tested in DMFC. PtGe and PtIn electrocatalysts supported on Vulcan carbon displayed the best behaviour, even higher than that shown by a commercial E-TEK catalyst.