Preparation and application of nanoporous carbon templated by silica particle for use as a catalyst support for direct methanol fuel cell

Polymer-silica composites were synthesized by resorcinol-formaldehyde polymerization in the presence of uniform size silica particles. After carbonization and subsequent removal of the silica template, these polymer-silica composites turned into nanoporous carbon xerogel with high surface area and large pore size. By controlling the initial pH of the carbon precursor solution, nanoporous carbons with different textural properties could be fabricated. As the pH of the reaction mixture was decreased, the pore size of nanoporous carbon increased because the aggregated silica particles, i.e., larger templates, were generated in low pH condition. Although the pore size of nanoporous carbon was increased with decreasing pH, the templating effect was reduced with decreasing pH, leading to the formation of significant microporous carbon framework in carbon xerogels. For DMFC application, the PtRu (1:1) alloy was supported on nanoporous carbons and activated carbon by a formaldehyde reduction method. It was revealed that the textural properties of carbon supports played important roles in the metal dispersion and DMFC performance of the supported PtRu catalysts. The support with large pore size and high surface area (especially, meso-macropore area) was favorable for high dispersion of PtRu catalyst and easy formation of triple-phase boundary. Microporous framework, resulted from the destruction of structural integrity, was insufficient for high dispersion of PtRu species. The catalysts with higher metal dispersion and structural integrity showed higher catalytic activities in the methanol electro-oxidation and the DMFC performance test.