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 Ptmetallic/Pttotal 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
°C reacted with atmospheric O2 and was easily desorbed.
However, linear CO species adsorbed on PtO
x
(x ≥ 2) sites was only desorbed at temperatures
≥100 °C, confirming the lack of CO oxidation activity
at room temperature with ionic Pt catalysts.
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