Study On The CO Tolerant Electrocatalysts And The Electrode Structure For The Proton Exchange Membranes Fuel Cells

The selection of the fuel is a key problem for the development and the application of proton exchange membrane fuel cells (PEMFCs), and the fuel produced by the reforming of methanol, gasoline or natural gas should be the most proper candidate for the mature reforming technology and the availability of the carbon containing fuels. However, the component of CO in the reforming gas (1-2%) is a severe poison to the anode electrocatalyst of PEMFCs, and the cell performance would decease seriously due to the CO poisoning of the anode electrocatalysts. Therefore, to solve the CO problem of PEMFC is crucial for the development and application of PEMFCs.A modified impregnating method for preparing highly dispersed PtRu/C electrocatalyst with an enhanced CO tolerance was developed in this thesis, which was characterized with the employment of alcohols as the surface active agent to lower the conglomerating inclination of the catalyst particles during their forming processes. The effect of the pore structure of the carbon support on the dispersion of the catalyst was investigated. It is found that the most proper structure should be of high surface area and the meso-pore distribution. At the same time it was brought forward that the enhancement of the activity and the function of the electrocatalyst could be achieved by modifying the structure and the component of the supports. According to modifying the carbon support with an additional component of the transitional metal oxide, e.g. HxMeO3/C (Me=W or Mo), the CO tolerant electrocatalysts of PtRu-HxMeO3/C were prepared through the modified impregnating method. The catalysts of PtRu-HxMeOs/C kept similar dispersion withthe PtRu/C and showed higher CO tolerance than the PtRu/C due to the spill-over effect of the fuels on the composite support. Except for the CO tolerant electrocatalysts, we have developed a novel kind of CO tolerant anode with a composite catalyst layer structure based on the electrooxidation mechanism. It was pointed out that the key factor for the achievement of CO tolerance was to acquire a proper distribution of the different catalysts in the anode. According to the above view, two kinds of the composite anode were developed with an enhanced CO tolerance in comparison with the traditional electrode.