| Direct methanol fuel cell(DMFC) is one of the most promising green energy technologies. It has the advantages of small size, easy operation, abundant fuel sources and so on. The anodic catalyst is a key material of the DMFC. At present, transition metals including Pt and Pt-based alloys are still the main materials of the anode catalyst. But the commercialization of DMFC is limited by its defects such as low activity, poisoning and so on. In this work, long chain polymers are introduced into the Pt based catalyst to improve the activity and anti toxicity of the catalysts via the spatial structure change and the interaction. Microwave assisted glycol reduction method is employed, with the introduction of phosphotungstic acid, and other metals for further modification, when preparing a polymer-modified Pt-based catalyst. Transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS) methods are used for the characterizations of catalyst morphology and structure. Electrochemical methods are used to investigate the catalytic activity and anti-poisoning property in methanol electro-oxidation reaction. The main results obtained are outlined as follows:Poly(diallyldimethylammonium chloride)(PDDA) solution was introduced to functionalize Pt based catalysts, and the influences of the dosage and adding sequential of PDDA on Pt Ru/CNT-PDDA catalysts performances were studied. The characterization results show that the average particle size decreases with the increase of Rt Ru particle loading on the PDDA functionalized catalysts. Electrochemical tests show that the Pt Ru/CNT-PDDA catalyst has better activity for methanol oxidation and stronger anti-toxicity property than Pt Ru/CNT catalyst, and the catalyst firstly modified with PDDA has a good catalytic activity. When the mass ratio of Pt to PDDA is 4:1, Pt Ru/CNT-PDDA catalyst has the best catalyst performance. For Pt Ru W ternary catalysts, Pt Ru WOx/CNT catalyst modified with PDDA showed better activity and stronger electrochemical stability than the unmodified one. Pt Ru/CNT catalyst and Pt Ru/GNS catalyst were functionalized by chitosan respectively. The results indicate that the presence of chitosan promotes particle loading and dispersion, and the catalytic activity of catalysts were increased significantly. catalysts prepared from carbon nanotubes and grapheme mofified with chitosan have better performances than the unmodified catalysts.Pt Ru/CNT catalysts were modified by the conducting polymer(polypyrrole and polyaniline). The results show that the supports functionalized with conducting polymer have rough surface. The interaction between the support and the polymer produced good particle distribution and small size of catalysts, and the catalytic activity was promoted. Pt Ru/CNT-PPy catalyst with the mass ratio of Pt to PPy of 3:1 has the best catalytic performance, and ammonium persulfate(APS) has better oxidative effect than Fe Cl3. Pt Ru/CNT-PANI(1:0.15) catalyst has the best charge transfer performance for methanol oxidation. Pt Ru/CNT catalyst functionalized by polyaniline combined with PDDA has better methanol oxidation activity and anti-poisoning ability than Pt Ru/CNT-PANI catalyst.Pt Ru/CNT-HPW catalyst with the mass ratio of Pt to HPW of 2:1 has the best performance for methanol oxidation. TEM results show that the combination of phosphotungstic acid which has large molecular groups with polymer decreased the size of Pt Ru alloy particles and promoted the dispersion. The electrochemical results indicate that the combination of HPW and long chain polymers forms spatial structures. They can promote the adsorption of hydrogen desorption and increase the content of oxygen species on catalyst surface. Moreover, the dynamic performances of catalysts were also effectively improved and the electrochemical stability was enhanced. Catalysts modified with phosphotungstic acid and polymer show higher catalytic performances for methanol oxidation. |
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