Effect of Pt Particle Size and Valence State on the Performance of Pt/TiO2 Catalysts for CO Oxidation at Room Temperature

A series of Pt/TiO2 catalysts with various Pt particle sizes and valence states were prepared and tested for CO oxidation at room temperature. Field-emission transmission electron microscopy and X-ray photoelectron spectroscopy analyses confirmed that the activity of the Pt/TiO2 catalyst was influenced by the particle size and valence state of the catalyst particles. Excellent CO oxidation activity was observed at room temperature using highly dispersed, small metallic Pt particles. Increasing the Pt-metallic/Pt-total ratio resulted in an increase of turnover frequencies. According to the Fourier-transform infrared spectroscopy results, the linear CO species that was adsorbed on metallic Pt sites at 25 degrees C reacted with atmospheric O-2 and was easily desorbed. However, linear CO species adsorbed on PtOx (x >= 2) sites was only desorbed at temperatures >= 100 degrees C, confirming the lack of CO oxidation activity at room temperature with ionic Pt catalysts.