| Fuel cells, as one of clean energy sources, have been one of important research topics, owning to the energy crisis and the gradually serious environmental pollution in the world. The study on the electrocatalytic oxidation of small organic molecules has been a very active field for the application of direct small organic molecule fuel cell. The purpose of this thesis is to study the electrocatalytic oxidation of methanol, formaldehyde and formic acid on co-deposited Pt-HxMoO3(hydrogen molybdenum bronze) electrode in sulfuric acid solutions.Several electrochemical methods including cyclic voltammetry, potential step and AC impedance, as well as scanning electron microscopy, are used in this thesis. The reduction of molybdate and the oxidation of the reduced product are studied first. Then deposited platinum and co-deposited Pt-HxMoO3 electrodes on base platinum and polyaniline are prepared. At last, the electrocatalytic oxidations of methanol, formaldehyde and formic acid on the deposited and co-deposited electrodes are studied.In the investigation of the reduction of molybdate and the oxidation of the reduced molybdate, following results are obtained: (l)Hydrogen molybdenum bronze is obtained when molybdate is reduced on the base platinum electrode in H2SO4 solution.(2)The reduction current of molybdate on base platinum electrode is influenced by H2SO4 concentration. The reduction currents of molybdate increase with increasing H2S04 concentration from 0.05mol/L to 3.7mol/L, and reach to a steady value when the H2SO4 concentration is higher than 3.7 mol/L. (3)The oxidation mechanism of hydrogen molybdenum bronze is influenced by H2SO4 concentration. There are two oxidation peaks of the hydrogen molybdenum bronze when the H2SO4 concentration is lower than 2.5mol/L, a third oxidation peak appears when the H2SO4 concentration is higher than 2.5mol/L. (4) The stability of hydrogen molybdenum bronze on base platinum electrode is influenced by H2SO4 concentration. The discomposed speed of hydrogen molybdenum bronze increases with increasing the H2SO4 concentration. (5)The polymerization degree of molybdate decreases with increasing the H2SO4 concentrationIn the investigation of oxidation of methanol, formaldehyde and formic acidVIon deposited platinum electrode (Pt/Pt) and platinum/hydrogen molybdenum bronze co-deposited electrode (Pt-HxMoO3/Pt), following results are obtained: (l)Methanol, formaldehyde and formic acid can be oxidized on the base platinum electrode , but the oxidation is hindered by some poison intermediates (CHX0, x=0,l,2,3). (2) The co-deposited Pt-HxMoO3/Pt electrode can be prepared when the platinum and the substoichiometric hydrogen molybdenum bronze (HxMo03, 0 |
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