Preparation And Characterization Of Carbon Aerogel Supported Pt Based Catalysts For Fuel Cells

Polymer electrolyte fuel cells, particularly direct methanol fuel cells (DMFCs), are recognized to be a promising electrochemical device. Fuel cells convert the chemical energy to electric power stored in fuels and oxidants by the electrochemical reaction in which catalysts play a key role. Durability and cost that have closely related to catalysts are main problems. In this thesis, novel support and catalysts are prepared and the relevant elcetrocatalysis have been done. The main progress of this study is summarized as follows:1. Organic aerogels were prepared by sol-gel polycondensation of resorcinol and formaldehyde and dried under a semi-sealed condition at ambient pressure. Carbon aerogels were obtained by the dried organic aerogels carbonized at high temperature. Carbon aeogel is characterized by Raman, Infrared Spectroscopy, BET, TEM, and XRD. Carbon aerogel has typical three-dimensional continuous disorder nano-network. The size of carbon aerogel ranges from 30 to 40nm. The average pore size of carbon aerogel is 18.18nm, and the pore size distributes intensively. BET surface area of carbon aerogel is 634.7 m2/g. The results of electrochemical measurements indicate that carbon aerogel has good electrochemical property.2. Pt/carbon aerogel catalysts were prepared by the microwave-assisted polyol process. The Pt-doped carbon aerogels showed good platinum dispersion, with a sharp particle size distribution between 2.0 and 5.0nm, which is suitable as catalysts for direct methanol fuel cell applications. A face-centered cubic (fcc) structure are observed from the characteristic diffraction peaks of Pt particles. The Pt/carbon aerogel catalyst shows higher electrochemical catalytic activity and stability for methanol oxidation than Pt/C catalyst of the same Pt loading. The unique structure of the carbon aerogel supported Pt catalyst makes this catalyst the most promising novel catalyst for PEM and DMFC operation.3. The PtAu/carbon aerogel catalysts were prepared by the microwave-assisted polyol process. PtAu/carbon aerogel catalysts show typical characteristic peaks which demonstrates the PtAu catalyst has a face-centered cubic (fcc) structure. All the particle sizes appear to be well-dispersed on the surface of carbon aerogel and have a relatively narrow particle size distribution. Little major agglomeration is observed on the carbon aerogel support. The results of electrochemical measurements indicate that when the atom ratio of Pt:Au is 2:1, PtAu/carbon aerogel catalyst appears higher catalytic activity and stability towards methanol oxidation.4. Carbon aerogel supported PtCo catalysts were synthesised by the microwave-assisted polyol process. PtCo particles are well-dispersed on the surface of carbon aerogel with a size of 2.0-4.0nm. XRD characteristic peaks of PtCo/carbon aerogel catalysts were shifted to higher angles with increasing Co content. For the catalysts, the optimum atom ratio of Pt to Co is Pt3Co1/carbon aerogel, and its catalytic activity and stability are highest compared with other PtCo/carbon aerogel.