Approach to High Performance Electrode Catalysts for DMFC

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The mesoporous carbons were synthesized by using mesoporous silica materials such as MCM-48 and SBA-15 as a template, respectively. Typically, the templates were impregnated with sucrose as a carbon source and sulfuric acid as an acid catalyst. Following dehydration-condensation of the carbon source, the carbonization was carried out mainly at 900℃ under flowing argon. The silica was removed from the silica-carbon composite by treating it with hydrofluoric acid, producing mesoprpus carbons CMK-1, CMK-3, and CMK-5. Another type of carbon has been also synthesized by using petroleum pitch. MCF carbons can be synthesized by using MCF silica as a template. A carbon structure composed of spherical hollows with closed walls with mesopores of around 4 nm in diameter is prepared by the two-step impregnation of sucrose followed by carbonization. The mesoporous structure was maintained up to 1400℃. Platinum is loaded on these mesoporous carbons. TEM observations revealed the presence of metal particles of below 2 nm in the mesoporous material treated at 1100℃. The metal dispersion is highly dependent not only on the carbon structures but also on the temperature for thermal treatments in inert gas atmosphere. The latter is interpreted in terms of the change in the surface functional groups and their density, which probably affect the interaction of the surface and Pt sources. Oxygen reduction activity of the Pt-loaded electrode on CMK-1 was higher than that of the acetylene derived carbon. The performance of Pt catalyst was affected not only by the Pt dispersion but also by their distribution in the carbon electrode.