Origin of Higher CO Oxidation Activity of Pt/Rutile than That of Pt/Anatase

Herein, we show that the weak interaction of CO with Pt/TiO₂ under the CO oxidation condition is the origin of higher CO oxidation activity of Pt/rutile than that of Pt/anatase. The results of CO temperature-programmed desorption (TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicate that the onset temperatures of CO desorption on freshly prepared Pt/rutile and Pt/anatase are the same. However, the CO-TPD curves of Pt/rutile after the reaction test show that the desorption temperature of CO shifts to a lower temperature, while that for Pt/anatase does not change. The in situ pulse reaction using DRIFTS reveals that CO on Pt/rutile reacted with oxygen faster than CO on Pt/anatase. IR spectra with peak deconvolution of adsorbed CO on Pt/rutile exhibit that CO adsorbed on the terrace sites of Pt clusters on rutile (2089 cm^–1) reacts readily with O₂. These results indicate that the higher low-temperature activity of Pt/rutile is related to its weaker interaction with CO compared with Pt/anatase under the reaction conditions. Our findings deepen the fundamental understanding of metal–support interaction and CO oxidation on Pt/TiO₂ catalysts.