Carbon-supported Catalyst Layer Fabrication

Saab et al. [92, 93] developed a doctor-blade spreading technique for preparing the catalyst layers in a faster and highly reproducible fashion. The ink was coated onto laser jet transparency material wifli a doctor blade device driven by an X-Y chart recorder time base. The chart recorder time base is a highly accurate mechanical drive with a broad range of selectable speeds (20-0.05 cm/s), which is useful when compensating for liquids of varying viscosity. Machined aluminum 

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The DMFC based on carbon supported catalyst with low catalyst loading (1.3 mg/cm ) has been successfully tested in a methanol/air environment. The cell shows better performance in comparison to the cell based on unsupported catalyst with twice the Pt-black loading. These results are explained by the higher surface area of Pt carbon supported catalyst and are in good correlation with CV and BET data. The results show that carbon supported catalyst can be successfully used as the electrode material for the fabrication of relatively cheap cathode catalyst layers in DMFC. Further work is needed to estimate the lower concentration limit of the catalyst, which is sufficient to maintain stable performance and long-term endurance. 

Liu, D.-J. and Yang, J., Method of Fabricating Electrode Catalyst Layers with Directionally Oriented Carbon Support for Proton Exchange Membrane Fuel Cell, U.S. Patent Application 20060269827, November 30, 2006. 

Because it is believed that carbon nanotubes will play an important role in ultrasmall device preparation in the future (see Chap. 5), fabricating regular supramolecular assembhes of carbon nanotubes represents an important challenge. One example is shown in Fig. 4.56. A layer of porous sihcon is first prepared on a silicon support, and iron is then deposited on the porous silicon using an appropriate mask and an electron beam. When the patterned surface is exposed to ethylene gas, carbon nanotubes grows selectively on the sites covered with the iron catalyst. Again, this technique allows a range of different catalysts and patterns to be used, and various patterns of carbon nanotube arrays are easily fabricated. 

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