Promotion effect of ultraviolet light on NO + CO reaction over Pt/TiO2 and Pt/CeO2–TiO2 catalysts

• UV irradiation promotes the thermo-catalytic reaction of CO  + NO over Pt/TiO2 and Pt/CeO2–TiO2.
• Photo-excitation of TiO2 act as electron donor to increase the surface electron densities of active sites.
• CeOx promotes the photo-generated electron transfer from TiO2 to Pt by the process of Ce4+ → Ce3+.
• High electron densities of active sites promote the adsorption and activation of CO and NO.

Pt catalysts supported on TiO2 and CeO2–TiO2 (Pt/TiO2 and Pt/CeO2–TiO2) were prepared by a two-step precipitation–deposition method, respectively. As compared to Pt/TiO2, Pt/CeO2–TiO2 exhibits a higher thermo-catalytic activity and stability for CO + NO reaction, and also exhibits a stronger effect of ultraviolet light (UV) on promoting this reaction. The in-situ FTIR results indicate that the doped CeO2 can significantly improve the adsorption of NO at Pt/CeO2–TiO2, while UV light further enhance the adsorption of NO and its activation. Based on the results of Raman spectrum, electron paramagnetic resonance and the X-ray photoelectron spectroscopy testing, it is proposed that UV irradiation can cause the increase in surface electron density of Pt nanoparticles by the photo-induced electron transfer from TiO2 to Pt. Moreover, the doped CeO2 can further improve the electron transfer from TiO2 to Pt through a process of Ce4+ → Ce3+ under UV irradiation, resulting in the adsorption and activation of CO and NO species at Pt/CeO2–TiO2. This result also indicates that the photo-excitation of supports can strengthen the strong interaction between support and metal nanoparticles, and then promote the thermo-catalytic reactivity of catalysts.

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