Promoting Effect of Tin in Platinum Electrocatalysts for Direct Methanol Fuel Cells (DMFC)

Abstract

Pt-Sn anodic catalysts supported on multiwall carbon nanotubes, mesoporous carbon and Vulcan carbon were prepared using a deposition-reduction technique with sodium borohydride, characterized by different techniques and tested as anodes in a single direct methanol fuel cell at low temperatures. Characterization and CO stripping results indicate the presence of promoting effects of Sn over Pt in catalysts supported on Vulcan carbon and carbon nanotubes. This would mainly be caused both by geometric modifications induced by Sn placed in the surroundings of the active metal phase and probable electronic effects. These promoting effects make the oxidation of CO to CO2 at low potentials easier, thus improving the CO tolerance of the anodic electrocatalyst. On the other hand, Pt-Sn catalysts supported on mesoporous carbon do not show a proper metallic phase needed for a good electrochemical behavior. When catalysts were tested in a DMFC, Pt-Sn catalysts supported on Vulcan carbon and carbon nanotubes gave a better power density than a commercial one mainly when working at low current densities.