Study On Structural Characterization, Electrocatalytic Activities Of Pt-Sn/graphene

As promising power sources for portable devices, direct methanol fuel cells (DMFC) have attracted great attention due to their high energy density, reduction of fossil fuel consumption, and low operating temperature. Despite significant progresses in DMFC research, there remain some critical issues, such as the low efficiency of fuel cells at cathode for oxygen-reduction reaction (ORR), the easy poisoning of Pt by CO, etc. Therefore, catalysts play a pivotal role in determining the efficiency, activity and costs of the fuel cells. Wherein, the performance of catalysts is strongly correlated to the structure and monodispersity of the catalyst material, which can be tuned by the selection of conductive supporting materials, as they have effect on the adhesion and dispersion of the catalysts. Up till the present moment, varieties of carbon materials were used as the catalysts support, including mesoporous carbon, carbon nanotubes and carbon microspheres, etc. The effect carbon support materials are largely influenced by their electrical properties, morphology and crystallographic structures. Graphene, a honeycomb like carbon material, offers extraordinary electronic, thermal and mechanical properties and are expected to find a variety of applications. Since the graphene sheets enable to be synthesized by chemical method, it is possibly realizable to utilize this unique material in fuel cells as electrode materials. To improve the electrocatalytic activity of noble metal catalysts and reduce the total cost of fuel cell system, Pt can be alloyed with transition metals or noble metals, such as Ru, Pd. Thus, it is urgent to replace the noble metals by cheap metals as the additional materials. In our experiment, with non-noble Sn element as the co-catalysts, Pt-Sn/graphene catalysts were prepared and their enhanced electrocatalytic activity was investigated as cathode catalysts of DMFCModified Hummers method was employed to synthesize graphene oxide, and Pt-Sn/graphene catalysts were prepared using a chemical reducing approach in one step. X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) were employed to characterize the prepared samples.The experimental results indicate that:graphene oxide was reduced to graphene in suit. The nanoparticles were uniformly dispersed on graphene surface with a diameter of3.19nm. Partly of Sn existed in the formation of SnO2. According to the results of electrochemical characterization, the electrocatalytic property of graphene-based catalysts were apparently better than that of carbon black-based catalysts. As the Pt-Sn/graphene possessing a favourable catalytic effect, the oxidation of methonal can be proceeding under lower potential. With the synergistic effect of Sn and graphene, tolerance toward CO of Pt was effectively strengthened, and the IF/IR reached to2.18.