Spatial confinement: An effective strategy to improve HO and SO resistance of the expandable graphite-modified TiO-supported Pt nanocatalysts for CO oxidation.

The expandable graphite (EG) modified TiO nanocomposites were prepared by the high shear method using the TiO nanoparticles (NPs) and EG as precursors, in which the amount of EG doped in TiO was 10 wt.%. Followed by the impregnation method, adjusting the pH of the solution to 10, and using the electrostatic adsorption to achieve spatial confinement, the Pt elements were mainly distributed on the exposed TiO, thus generating the Pt/10EG-TiO-10 catalyst. The best CO oxidation activity with the excellent resistance to HO and SO was obtained over the Pt/10EG-TiO-10 catalyst: CO conversion after 36 hr of the reaction was ca. 85% under the harsh condition of 10 vol.% HO and 100 ppm SO at a high gaseous hourly space velocity (GHSV) of 400,000 hr. Physicochemical properties of the catalysts were characterized by various techniques. The results showed that the electrostatic adsorption, which riveted the Pt elements mainly on the exposed TiO of the support surface, reduced the dispersion of Pt NPs on EG and achieved the effective dispersion of Pt NPs, hence significantly improving CO oxidation activity over the Pt/10EG-TiO-10 catalyst. The 10 wt.% EG doped in TiO caused the TiO support to form a more hydrophobic surface, which reduced the adsorption of HO and SO on the catalyst, greatly inhibited deposition of the TiOSO and formation of the PtSO species as well as suppressed the oxidation of SO, thus resulting in an improvement in the resistance to HO and SO of the Pt/10EG-TiO-10 catalyst.