| Highly dispersed catalysts loaded on conductive support, commonly platinum and platinum-based catalysts, are used as electrode materials in low-temperature fuel cells. Carbon materials, such as carbon black and carbon nanotubes, are commonly used as fuel cell catalysts supports. Graphene, as a two-dimensional one-atom-thick planar sheet of sp2bonded carbon atoms, with the high surface area, high conductivity and unique graphitized basal plane structure, recently has been investigated as a support for low-temperature fuel cell catalysts.Different methods have been developed to prepare Pt/graphene catalysts. By the performance study, scholars found that compared to Pt/carbon black, Pt/graphene has a better catelytic performance. To improve the electrocatalytic activities of graphene, many attempts have been tried by introducing other elements, such as Ru、Pd to synthesis Pt-Ru、Pt-Pd alloys, and acceded anticipating results. In this study, Sn was introduced to further reduce the cost and improve the efficiency. Physical properties and electrocatalytic activities of those catalysts were investigated. Modified Hummers method was employed to synthesize graphene oxide. With H2PtCl6and SnCl2as precursors, Pt-Sn/GNs catalysts were obtained by one-step reduction of ethylene alcohol. The structural characteristics of specimens were performed by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Photoelectron Spectra (XPS). Meanwhile, the electrocatalytic properties were conducted by Cyclic Voltammetry method.The result shows that:(1) Platinum and tin nanoparticles are uniformly dispersed on graphene. It also indicated that in the Pt/C, Pt/GNs and Pt-Sn/GNs catalysts, Pt is mainly existed as Pt(O), while Sn is mainly presented as Sn(Ⅱ&Ⅳ) in the Pt-Sn/GNs catalysts.(2) Compared with Pt/C and Pt/GNs, Pt-Sn/GNs has a better catalytic performance. Pt nanoparticles have a smaller particle size according to the large specific surface area and great amount of attachment sites on Pt-Sn/GNs. Whileas, the Pt nanoparticles are agglomerated apparently when GNs has a higher Pt loading. In conclusion, by introducing Sn, the Pt lattice structure is changed, the agglomeration of Pt is effectively restrained, the electrochemical active surface area of Pt is highly increased and the methanol oxidation activity of the sample is greatly improved. |
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