Preparation And Electrochemical Properties Of Nano Tungsten Oxide Composite Catalyst

Direct methanol fuel cell （DMFC） has a low operating temperature, high-energy density and easy package to carry, simple cell structure and security features, and has broad application prospects in the field of portable electronic equipment and automotive. But some question such as high price of catalytic noble metal, easily poisoned and slow kinetics of anode reaction prevent large-scale commercial applications of DMFC Therefore, we need to study new catalysts with high catalytic activity, selectivity and low cost, in order to facilitate a wide range of commercial applications.In this paper, carbon nanotubes （CNTs）, mesoporous WO₃ and WO₃/VCNTs composite materials were respectively used as the carriers. Highly dispersed supported catalysts were prepared by means of NaBH4 chemical reduction and microwave-assisted ethylene glycol reduction. Structure and morphology of catalysts were characterized by X-ray diffraction analyzer （XRD）, X-ray photoelectron spectroscopy （XPS）, high-resolution perspective microscopy （HRTEM） and spectroscopy （EDX）. Performances of electro-catalytic oxidation of methanol were tested by the electrical tests. The specific research work was reflected in the following aspects:（1） The reaction conditions of uniformly dispersed MW-Pt/CNTs catalyst by microwave-assisted ethylene glycol were researched. The results found that as reaction temperature increased, Pt loading amount of CNTs were increased. When the reaction temperature reached 160℃, Pt ions in the solution could be fully reduced, and Pt nanoparticles could be fully loaded on the surface of carbon nanotubes. Cyclic voltammetry and chronoamperometry test results showed that MW-Pt/CNTs-160 exhibited higher electrocatalytic activity, better anti-poisoning ability, and good stability during methanol oxidation in comparison to BH-Pt/CNTs with NaBH4 as a reducing agent.（2） Mesoporous tungsten trioxide （m-WO₃） was synthesized by hard template methods. Pt/m-WO₃ electro-catalyst was synthesized by reduction of chloroplatinic acid precursors and catalyst was characterized. On the one hand, the presence of the mesoporous WO₃ inhibited agglomeration of Pt particles. On the other hand, Pt/m-WO₃ catalyst had larger electrochemical active surface area and better resistance to CO poisoning due to strong interaction and hydrogen spillover effect between m-W03 and Pt.（3） Two WO₃-CNTs nanocomposites were respectively prepared by immersion precipitation method and surface modification technology. Pt nanoparticles were loaded on the surface of WO₃-CNTs by microwave-assisted ethylene glycol reduction. The introduction of WO₃ nanoparticles improved the catalytic performance of Pt-based electrocatalysts. On the one hand, the modificaion of WO₃ reduced Pt nanoparticles size, while the metallic state of Pt content was increased. On the other hand due to the bifunctional mechanism that methanol adsorption occurs mainly on the Pt-bit while oxidation of intermediate COads on the WO₃ position. Under the same conditions, as compared with the impregnated catalyst obtained by the precipitation method, the surface modification prepared catalyst for the methanol oxidation in acidic solution had higher reactivity and stability. On the one hand, WO₃ nanoparticles prepared by surface modification technology were uniformly dispersed on the surface of CNTs, while WO₃ nanoparticles prepared by immersion precipitation method had apparent agglomeration. On the other hand, Due to strong interaction between Pt and WO₃ nanoparticles prepared by surface modification technology.