The relationship between the structure and ethanol oxidation activity of Pt-Cu/C alloy catalysts

In this study, the Pt-Cu/C alloy with nominal composition of Pt0.25Cu0.75 was produced via three different methods: impregnation, impregnation in the presence of sodium citrate additive and microwave assisted polyol method. Each method produced catalysts with differing structural and electrochemical properties. These catalysts were also heat treated to induce changes in the crystalline structure which in turn altered the activity towards the ethanol oxidation reaction (EOR). The crystalline structure, particle dispersion and chemical composition of the Pt-Cu samples were studied by Thermogravimetric Analysis (TGA), X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM) Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS). The ICP, XPS, TGA and TEM results indicate each synthetic method produced catalysts with different chemical composition, metal loadings and particle dispersion. The XRD analysis showed that the heat treatment of the Pt-Cu/C samples resulted in ordered intermetallic crystalline structures such as PtCu and PtCu3. The highest EOR activity was observed for samples rich in intermetallic ordered phases, PtCu in particular. XPS and CO stripping measurements indicates that the electronic structure of the Pt-rich surface of the Pt-Cu particles was altered due to formation of intermetallic phases and the Cu-rich core.