Research Of Effect Of Heteropoly Acid To Methanol Anodic Oxidation Behavior

Developed direct methanol fuel cell (DMFC) has been received widespread attention due to the abundant source, the low price, the safety of storage and transportation of fuel. However, the low electro-catalytic activity of anodic catalyst restrict its practical use. In order to improve the electro-catalytic activity of platinum based catalyst to methanol oxidation, in this thesis, firstly prepare heteropoly acid modified Pt/GC electrode with different concentration by cyclic voltammetry method, and then test the cyclic voltammetry curves individually in vitriolic and methanol solution. The study shows the best concentration for both phosphomolybdic acid and phosphotungstic acid is 1×10^-3mol/L. And find the more heteropoly acid modified on electrode, the lower peak-up potential towards methanol because of the existence of oxygenous species.PtRu/C, PtRuWO₃/C and PtRuMoO₃/C are prepared by chemical reduction of the appropriate salt solutions, and structural characterizations are carried out with X-ray diffraction. The result indicates Pt and Ru form alloy and the transition metal oxides are existed in amorphous form. The morphology of the catalysts was characterized with a transmission electron microscope (TEM). Modified the three electrodes with two different heteropolyacid respectively and test the well modified electrodes using the cyclic voltammetry and amperometric i-t curve.The result shows that PtRuMoO₃/C shows the best catalytic activity towards methanol and phosphomolybdic acid modified PtRuMoO₃/C electrode can be considered as the best anodic electrode for DMFC.Finally, great effort on explaining the cooperation of heteropolyacid and carbon supported alloy electrode. Because the tungsten from the phosphotungstic acid could pull out and deposit on the surface of catalyst, and the electronegativity of Mo-O is smaller than that of W-O. The smaller the electronegativity is, the higher oxidation activity is. Thus phosphomolybdic acid shows better catalytic oxidation activity than phosphotungstic acid.