The effect of plasma pre-treatment of carbon used as a Pt catalyst support for methanol electrooxidation

Vulcan XC-72 carbon black for use as a catalyst support was treated in three different plasma atmospheres, H2, Ar and O2. The results showed that the microstructure and surface functional groups were significantly changed after plasma treatment. Pt/C catalysts were prepared by chemical reduction of H2PtCl6 with HCHO and those with untreated and plasma treated carbon black supports were characterized and tested for methanol electrooxidation. TEM showed that the platinum nanoparticles on H2 and Ar plasma treated carbon were uniform and well distributed. Those on untreated carbon were uniform in most regions but coalesced in others. On O2 plasma treated carbon agglomeration of the platinum nanoparticles was significant. XRD showed that the catalysts were composed of face-centered cubic Pt nanoparticles and XPS showed that they were metallic with no oxides present. Cyclic voltammetry and chronoamperometry were used to study methanol electrooxidation on the Pt/C catalysts in a solution of 0.5 M H2SO4 + 0.5 M CH3OH, and showed that the catalytic activity those using H2 and Ar plasma treated carbon was higher than for the untreated one. Catalysts supported by O2 plasma treated carbon showed no catalytic activity. The treatment atmosphere of carbon therefore had a large effect on the catalyst performance, with the H2 plasma being the best.