Evaluation of porous carbon substrates as catalyst supports for the cathode of direct methanol fuel cells

This paper presents an investigation into the effect of the cathode catalyst substrate morphology on the performance of supported catalysts for direct methanol fuel cells (DMFC). Two porous carbons were synthesized by a sacrificial templating method, one using disordered, macroporous silica diatomaceous earth, the other using ordered, mesoporous SBA-15. The Pt particles deposited onto the synthesized mesoporous substrate and commercial Vulcan XC-72 were shown to have fairly uniform dispersion, with particle size in the range 2-3 nm, and high catalyst surface areas. In situ single cell DMFC testing showed that the Pt catalyst supported on carbon based on diatomaceous earth (Pt/C-Celatom) exhibited the lowest cell impedance, which may be attributed to the large pores, which facilitate oxygen transport, and to the low porosity, which enhances protonic and electronic conductivity of the catalyst layer. In DMFC polarization tests, the Pt/C-Celatom also exhibited the highest power output of the tested catalysts, with a peak power density 28% better than the current commercial standard, Vulcan XC-72.