Ordered Porous Carbons with Tunable Pore Sizes as Catalyst Supports in Direct Methanol Fuel Cell

Abstract

Ordered uniform porous carbon frameworks with pore sizes in the range of 10 to ∼1000 nm were synthesized against removable colloidal silica crystalline templates by carbonization of phenol and formaldehyde as a carbon precursor. The porous carbons were used as supports for a Pt(50)−Ru(50) alloy catalyst to study their supporting effect on the anodic performance of the catalyst in a direct methanol fuel cell (DMFC). The use of the ordered uniform porous carbons resulted in much improved catalytic activity for methanol oxidation in the fuel cell probably due to their high surface areas, large pore volumes, and three-dimensionally interconnected uniform pore structures, which allow a higher degree of dispersion of the catalysts and efficient diffusion of reagents. In general, the smaller the pore sizes in the porous carbons were, the better the catalytic activity for methanol oxidation was. In addition, as pore sizes are getting smaller, the structural integrity with good pore interconnection seems to be getting more important for the catalytic oxidation of methanol. Among the porous carbons studied in this work, the one with about 25 nm in pore diameter (PtRu−C-25) showed the highest performance with power densities of ∼58 and ∼167 mW/cm2 at 30 and 70 °C, respectively. These values roughly correspond to ∼70 and ∼40% increase as compared to those of a commercially available Pt−Ru alloy catalyst (E-TEK), respectively.