Study On Graphene Supported Pt-ru Based Anode Catalyst For Direct Methanol Fuel Cells

Direct methanol fuel cell(DMFC) is a promising candidate as power source in portable electronic products, electric vehicle, etc., due to its advantages of easy transport and storage of the fuel, low weight, volume and high energy efficiency. At present, the performance and cost of DMFC still have not met the need of commercial applications because of some big technical problems, such as low activities of the anode catalysts and methanol crossover. The problem of the low activity of the anode catalysts is especially more serious, leading to the high metal loading and high cost of DMFC. In order to solve these problems, the main research contents of this thesis is to develop the PtRu-based anode catalysts with new supports such as graphene (G), graphene-carbon nanotubes composite support (G-CNTs) and poly(styrenesulfonic acid sodium)(PSS) functionalized graphene, and to study the relationship between the methanol electro-oxidation activities and the structure of the catalysts by means of various electrochemical methods and catalyst characterization techniques. The main results are as follows:Part Ⅰ:Graphite oxide (GO) was prepared from flake graphite by modified Hummer’s liquid oxidation method. The chemically reduced graphene (CRG) and thermally reduced graphene (TRG) were prepared by chemical reduction method and thermal reduction method, respectively. TRG does not tend to agglomerate, and the content of oxygen containing groups is less than that of CRG, indicating more complete reduction. However, the catalytic activity of PtRu/TRG is lower than that of PtRu/CRG. This is because TRG with less oxygen containing groups can’t appropriately absorb PtRu nanoparticles, and can’t provide enough surface hydroxyl to oxidize the poisoning species of CO.The PtRu/G and PtRuMo/G catalysts were prepared by impregnation method using graphene as the support. The catalytic activity and stability of PtRuMo/G are higher that those of PtRu/G catalyst. The MoOx species can facilitate the water dissociation at lower potentials to produce hydroxyl, which can oxidize the poisoning CO species on Pt to increase the anti-poisoning ability of the PtRuMo/G catalyst.Part Ⅱ:The PtRuMo/G-CNTs catalysts were synthesized by impregnation method using graphene-CNTs as the composite support. The catalytic performance of PtRuMo/G-CNTs catalyst is higher that those of PtRuMo/G and PtRuMo/CNTs. CNTs may act as a nanospacer, electron conductivity intensifier and pore former to prevent the restacking of graphene nanosheets, enhance the electron conductivity of the composite support and increase the mass transport of the reactants, products and electrolyte.Part Ⅲ:Graphene was functionalized by PSS for the first time, and PtRu/PSS-G catalyst were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The results show that the naonparticle dispersion, catalytic activity and stability of PtRu/PSS-G are higher than those of PtRu/G catalyst.The nanocatalysts described in this paper show high catalytic activity and stability for methanol electro-oxidation. The addition of Mo to the PtRu catalysts improves the electrocatalytic activity and anti-poison ability. Novel carbon supports such as G-CNTs and PSS-G have been used to enhance the catalytic activities and stabilities for methanol electro-oxidation, and thus improve the utilization of the precious metal and reduce the cost of the anode catalysts.