Preparation And Electrocatalytic Properties Of Multilayered Composites Constructed From Polyoxometallates,Metal And Poly(Amidoamine)Dendrimer

Direct liquid fuel cells are becoming a promising power source owing to its high efficiencies, low emission, and reliability. Platinum and other precious metals are commonly used as the anode catalysts in direct liquid fuel cells. However, the direct liquid fuel cell commercial development is still limited because of its high cost, rarity, low catalytic efficiency and easy poisoning by intermediates (e.g. CO). Therefore, enhancing the activity, stability and intermediates tolerance ability of catalysts play a key role in developing commercial application of direct liquid fuel cells.In this paper, the {POMs/metals/PAMAM}n multilayer nanocomposites were fabricated on the electrode surfaces by electrodeposition technique in order to improve activity, stability and intermediates tolerance ability of Pt-based catalysts. The influences of preparation conditions and different pH values on morphology and catalytic properties of the catalyst were investigated. The resulting multilayer nanocomposites were characterized by XPS, XRD, CV, SEM, EIS and UV-vis. The experiment data showed that inorganic and organic components were incorporated into the multilayer composites and their original structures and properties were remained no changes. The growth process of the composites was quantitative and highly reproducible from layer to layer. It was found that we can choose the deposition potential and other conditions to control the morphology of the catalyst, and then regulate the electroactivities of the catalyst used in fuel (e.g. methanol, ethanol, formic acid) oxidation.The multilayer films consisting of palladium(II)-substituted Keggin-type polyoxometalates and G4poly(amidoamine)(PAMAM) dendrimer were fabricated on electrode surface by layer-by-layer self-assembly technique. The multilayer composite films were stable and exhibited good catalytic activities for the reduction of BrO3and H2O2in the NaAc-HAc buffer solution. The catalytic activity was linearly proportional to the number of layers within a certain range. And this composite film was an excellent co-catalyst on methanol and other liquid fuels electro-oxidation. In addition, the optimal obtained composite catalysts of {PdPW11/Pt/PAMAM}n and {PMo12/Pt-Cu/PAMAM}n exhibited good catalytic activity stability and CO tolerance ability toward the electrooxidation of methanol, ethanol and formic acid. The nano-particles on the surfaces of above-mentioned multilayer composites modified electrodes displayed uniform and high dispersion. The catalytic activity was linearly proportional to the number of layers within a certain range.