| The energy crisis and environmental pollution are two potential problems that constraint the sustainable socio-economic development in the 21 st century. Fortunately, direct methanol fuel cell(DMFC) can provide an effective way in order to solve the current energy crisis and environmental pollution; while the catalyst research is the critical technology to solve the low-temperature catalysis for methanol fuel cells. In this paper, titanium dioxide and platinum(Pt/TiO2) are adopted as our catalyst system. The modifications of Pt and TiO2 are carried out in order to enhance its catalytic activity in methanol oxidation reaction(MOR) and the enhanced catalytic mechanism are explored as well through the first principles theory. According to our findings, we firstly bring a new concept that hydrogen-treated direct methanol fuel cell. This study has a great significance not only for new and improved catalysts, but also provides a theoretical basis for the design of new energy devices. The main contents and conclusions are as follows:(1) The interface effect between platinum-nickel cluster and anatase {101} are studied through the first-principles and periodic boundary model, and the catalytic mechanism of methanol dissociation based on Pt-Ni/TiO2 system are investigated as well. A density functional theory(DFT) based method in conjunction with the projector augmented wave and pseudopotential methods have been applied to investigate the adsorption of Pt4 and Pt3 Ni on the anatase TiO2 {101} surface. Two stable Pt3 Ni adsorptions with considerable adsorption energies on the anatase TiO2 {101} surface were identified. Analysis of the partial density(PDOS) of states and Bader charge suggest that the electronic structure of Pt is modified by Ni due to the electron transfer from Ni to Pt atoms in the Pt3 Ni clusters. The 2cO(3cO)-Pt Ni-5cTi conformation of the adsorbed Pt3 Ni on the anatase TiO2 {101} surface provides a more feasible model for electron injection through the Pt3Ni/TiO2 interface. Finally, the reactivity of Pt3Ni/TiO2 is superior to Pt4/TiO2 and effectively manifests itself in the eased decomposition of O-H bonds derived by methanol and alleviative CO adsorption.(2) Single-crystalline anatase TiO2 nanobelts with dominant surface of {101} facet are hydrogenated and used as a substrate of platinum for MOR. The hydrogenated TiO2 anatase {101} supporting Pt exhibits a 228% increase of current density for methanol oxidation compared with the same system without hydrogenation in dark condition. The synergetic interactions of hydrogenated anatase {101} with Pt cluster are investigated through first principle calculations, and find that the hydrogenation shifts the conduction band minimum to the Fermi level of pristine TiO2, and reduces the activation barrier for methanol dissociation considerably. Thus, this work provides an experimental and theoretical basis for developing non-carbon substrate with high electro-catalytic activity toward MOR.(3)Titanium dioxide nanowires are prepared through hydrothermal method and treated in the hydrogen of different concentrations(5%-20%). Platinum nanoparticles are deposited on titanium dioxide nanowires through optical deposition method. With the increase of hydrogenation concentration, the depositon amount of platinum nanoparticles on titanium dioxide increases, and subsequently decreases. Among of them, the platinum nanoparticles which deposited on the 10% H-treated titanium dioxide have the largest chemical activity area. For the corresponding system, Pt/10%H-TiO2, has the highest electro-catalytic activity toward MOR in alkaline solution. After analyzing the structures of the titanium dioxide treated with different hydrogen concentrations and find that moderate concentration of defects and vacancies induced during hydrogenation is favorable for the deposition and growth of platinum nanoparticles. |
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