Preparation And Characterization Of Porphyrin As Cathode Catalysts For Direct Methanol Fuel Cells

In recent years, direct methanol fuel cell (DMFC) is considered to be a promising electrochemical power source in portable electronic devices due to its high power density, easy charging and environmental compatibility. However, some technical challenges have to be overcome before the development of DMFC, including: (1) the scarce resources; (2) the high cost of platinum; (3)"methanol crossover"problem. It is very important to find new catalyst to improve the catalytic activity for methanol oxidization reaction and oxygen-reduction reaction (ORR).Several aspects were investigated in this thesis as follows:The catalyst of MoN/C were prepared by heat treatment MoTPP/C in NH₃ atmosphere. This catalyst was used as the cathode catalysts of fuel cells. The effect of the heat treatment time, heat treatment temperature and the loading of MoTPP were discussed. The catalyst have the stability and catalytic for the oxygen reduction and have methanol-tolerant.In order to further research the mechanism of the catalyze reaction, the catalyst structure was characterized via X-ray diffraction(XRD),Transmission Electron Microscope(TEM),XPS. TEM shows the particle size distribution, and the average crystallite diameter is about 4-5nm.The XPS reveals that there are three chemical states for molybdenum in the catalyst.The electrochemical behaviours of the catalyst were investigated by linear sweep voltammetry (LSV) and rotating disk electrode(RDE) measurements.The catalyst showed a comparatively good cell performance to oxygen reduction reaction(ORR).The reduction of oxygen in acid solution proceeds by an approximate four-electron pathway.CoTPP-Pt/C co-catalysts were prepared by a balance-adsorption method. Heat-treatment CoTPP-Pt/C co-catalysts owned higher activity for ORR and better methanol oxidation ability.