Catalyst Structure - Performance Trends for Sibunit Carbon Based Cathodes for Proton Exchange Membrane Fuel Cells

Abstract

Synthetic mesoporous carbon - Sibunit - offers a unique possibility to tune porous structure of the catalyst support without changing other textural parameters, enabling fundamental studies of the support structure - catalyst performance relationship. Three different Sibunit carbons with similar surface area of ca. 450-500 m2/g but widely varying pore size distribution were used for the preparation of the 40 wt% Pt/C catalysts for the cathode in H2/O2 PEMFC. Porous structure of the catalyst support was shown to affect both Pt utilization and the transport properties of the catalyst. Presence of the small - 3-4 nm in diameter - pores was shown to increase the utilization of Pt, while impairing the transport properties of the catalyst. For Sibunit supports, featuring large meso- and macropores, a lower degree of Pt utilization was found. Electrodes prepared using the latter catalysts exhibit excellent transport properties, comparable to those of the commercial benchmark Vulcan XC72 material.