| The low-temperature fuel cells that can run directly on liquid fuel such as methanol and so on are attracting more and more interest, especially for the large potential market for the vehicle applications. The direct methanol fuel cells(DMFCs) are more compact without heavy and bulky fuel reformer and can be applied to power electric vehicles. Liquid fuels, such as low-molecular weight alcohols, featuring higher volumetric and gravimetric energy densities and better energy efficiency, can be easily handled, stored and transported compared to the gas fuels such as pure hydrogen. Among these low-molecular weight alcohols, methanol currently appears to be aparticularly favorite fuel for these DMFCs.The DMFCs research has been paid much attention and great investments in the past decade, due to its numerous advantages, such as high energy density, ease of handling a liquid, and low operating temperatures. High activity of methanol oxidation on platinum makes this metal a suitable electro-catalyst for the DMFC anode. However, as well-known, pure platinum at room or moderate temperatures is readily poisoned by carbon monoxide(CO), a byproduct of methanol oxidation. So far, the best method has been to use alloy catalysts based upon platinum.In order to increase catalytic activity for methanol electrooxidation, we can controled catalyst surface structure and electronic structure through improvement of Pt and Pt-based alloy catalyst preparation method. Rare earth elements easy and metal to form a strong chemical bond-type role in the absorption with metal, and can form a variety of coordination compounds with small organic molecules, because of their rich d electron orbit. The surface structure of catalyst and catalyst support can be changed by modification with rare earth elements. Since ion beam sputtering(IBS) method in the preparation of films with Pt containing a small amount of particle diameter of nano-clusters, particle dispersion better than the large surface area, it was become a DMFC anode catalyst preparation methods.The PtRuNd thin-film and multilayer PtRu/PtNd alloy nanostructure thin-film used for anode catalytic electrodes of micro-direct methanol fuel cells (DMFCs) was fabricated by multi-target IBS. For PtRuNd/C thin-film catalyst at different times of the Nd substrate oxidation treatment. The surface chemical state, structure, surface layer structure, and morphology of the PtRu/PtNd thin-film were characterized by XPS, XRD, GIXD, AFM. Electrochemical properties were examined by CO-stripping voltammetry, CV, LSV, CA.(1) The results showed that the surface roughness of the PtRu/Nd thin-film catalyst was increased and the preferred growth was inhibited because of strong interaction of Pt+, Ru+ with Nd film layer. The electrochemical specific surface area of PtRu/Nd/C catalyst was increased. The catalytic activity of PtRu/Nd/C catalyst was increased obviously for methanol electrooxidation in acidic environment.(2) After at different times oxidization, the PtRuNd thin-film surface was coarsening have been found, XPS analysis results showed that the activity was further improved due to the presence of higher amount of RuO2 on the surface of PtRuNd/C thin-film. Accelerated the electrooxidation of methanol in the process of intermediate products to CO2, which improve the catalyst for methanol electrooxidation.(3)Research results indicated that PtRu/PtNd thin-film the surface chemical state and structure were changed due to the strong interaction between Pt+, Ru+ and Pt+, Nd+ during the ion beam alternate sputtering depositiong process. An abnormal widen of the peaks on XRD spectra and the electron transfer between Pt and Nd have been found. It was shown that the PtRu/PtNd thin-film has a special multiphase structure and electronic structure, and the electrochemical activity specific surface area of PtRu/PtNd thin-film was 115m2·g-1. Therefor, the PtRu/PtNd thin-film catalysts exhibited a higher catalytic activity for methanol electrooxidation in acidic environment. |
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