Reaction and surface characterization studies of titania-supported Co, Pt and Co/Pt catalysts for the selective oxidation of CO in H₂-containing streams

The selective, catalytic oxidation of CO in H₂-containing streams was investigated over titania-supported Co, Pt and Co/Pt catalysts. The work was motivated by the need to remove CO from the reformate fed to a polymer electrolyte fuel cell (PEFC) before it can poison the Pt anode. Pt/TiO₂ catalysts were active over a broad range of temperatures with a maximum at 120 °C. Co/TiO₂ catalysts were effective for CO oxidation at high temperatures (>100 °C). Mixed metal Co/Pt catalysts were quite effective, even at room temperature. The presence of H₂O and CO₂, major components of actual reformate, reduced the activity of all the catalysts tested, but less so for the Co/Pt catalyst. Activity decreased over long times but an intermittent, high-temperature "purge" regenerated the original activity. X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to understand the synergism between metal components. The Pt either influenced activity by helping reduce the Co, or the Pt and/or Co stabilized a Ti suboxide state that may play a role in the reaction process. The latter is most likely attributable to the strong metal support interaction (SMSI) effect previously noted on Pt/TiO₂ catalysts.