The Preparation Of Platinum Nanoparticles And Voltammetric Investigation Of Methanol Oxidation Reaction

Direct methanol fuel cell (DMFC) is one of the proton exchange membrane fuel cell with methanol as anode fuel and without methanol reformer, which is viewed as a promising power source for various portable devices due to its simplicity in structure, convenience in storage and higher energy density of the system. But the commerce of DMFC has so many difficulties. Therefore, the mechanism of methanol oxidation and anode electrocatalysts has been extensively studied and is still the subjects of interest. In this thesis, the preparation of platinum nanoparticles and the mechanism of methanol oxidation are investigated systematically.Platinum nanoparticles supported on multi-walled carbon nanotubes are prepared by simple pyrolysis of H2PtCl6 solution. Platinum nanoparticles are uniformly dispersed on MWCNTs which are not destroyed by this pyrolysis procedure. Electrochemical properties of Pt/MWCNTs composites indicate that a higher electrocatalytic activity has been shown in oxidation of methanol.Influence of formaldehyde and formic acid on the methanol oxidation reaction is respectively studied by cyclic voltammetry. The results demonstrate that the enhanced oxidation peak current of methanol is not simply originated from formaldehyde, and thought that there must be some catalysis of formaldehyde or its intermediates for the methanol oxidation reaction. The catalysis pattern of formaldehyde is also proposed. The results obtained from the effect of formic acid on the oxidation of methanol have revealed that formic acid attenuated the oxidation of methanol, probably due to the formation of methyl formiate during the methanol electrooxidation process.Nanoparticles of platinum are electrodeposited on platinum electrode by cyclic voltammetry, chronoampermetry and chronopotentiometry, respectively. The results imply that the modified electrode exhibit significant electrocatalytic activity for methanol oxidation. The platinum electrode modified by platinum nanoparticles prepared by cyclic voltammetry has a higher electorcatalytic activity for the positive oxidation peak.Electrochemical methods are used to investigate the electrooxidation behavior of methanol in different media. It is found that the lower acidity of solution and concentration of Na2SO4 is favorable to methanol oxidation. In alkaline media containing Na2SO4, the addition of NaOH is ibeneficial to the methanol oxidation. But when in alkaline media without Na2SO4, higher concentration of NaOH is not helpful to the oxidation of methanol. When the voltage is lower than -0.3V, an overlap of I-E curve between positive scan and negative scan can be observed.