Dual-Porosity Carbon Templated from Monosize Mesoporous Silica Nanoparticles

A mesoporous carbon structure was template-synthesized from small nanoparticles of silica with internal M41S type mesopores. The silica template was synthesized according to Suzuki et al. using an ionic surfactant to create the internal mesopores 1.8−3.5 nm diameter and a nonionic surfactant to limit the overall size of the particle. Larger mesopores in the silica are needed for carbonization to a better structure. This was achieved by the use of a swelling agent, trimethylbenzene (TMB). Characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen sorption analysis showed a mesocellular foamlike carbon structure composed of porous cells with internal hexagonally arranged channels. In addition to the 3 nm internal channels, there were larger mesopores connecting the cellular domains. These larger mesopores were formed in the interparticle voids created during carbonization. The dual porosity network structure had a high surface area (>1000 m 2 /g) and large pore volume (>1.2 mL/g). When loaded with Pt−Ru nanoparticles, the PtRu/carbon became a good electrocatalyst and gave the highest activity for methanol oxidation among several PtRu electrocatalysts including commercial electrocatalysts.