CO oxidation over CuOx/TiO2 catalyst: The importance of oxygen vacancies and Cu plus species

It is well documented that the existence of oxygen vacancies and active Cu species can improve CO oxidation activity over TiO2 substrate. Herein, TiO2-supported copper catalysts (CuOx/TiO2) with different ratio of oxygen vacancies (Ov) and Cu+ has been synthesized. The existence and amount of Ov and Cu+ species were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrum (EPR). The synergetic effect between Cu+ and oxygen vacancies was investigated in terms of O2 temperature-programmed desorption (O2-TPD), H2 temperature-programmed reduction (H2-TPR) and in situ DRIFTS spectra. Cu+ is the adsorption site for CO molecules, the abundant Ov can significantly activate molecular oxygen, which effectively oxidize the adsorbed CO molecules. The most suitable ratio between Cu+ and Ov has been confirmed. The CuOx/TiO2(Cu+ rich) catalyst (51% Cu+, 26.3% Ov) shows superior CO oxidation activity (T90 = 136 degrees C) compared to CuOx/TiO2(Ov rich) catalyst (39% Cu+, 28.5% Ov, T90 > 350 degrees C). This work provides comprehensive investigation of the role for abundant oxygen vacancies and Cu+ in CO oxidation reactions.

Automated summary

In this study, TiO2-supported copper catalysts (CuOx/TiO2) with different ratio of oxygen vacancies (Ov) and Cu+ were synthesized, and the existence and amount of Ov and Cu+ species were characterized. The synergetic effect between Cu+ and oxygen vacancies was investigated, and Cu+ was found to be the adsorption site for CO molecules, while abundant Ov could effectively activate molecular oxygen to oxidize CO. The most suitable ratio between Cu+ and Ov was confirmed, and CuOx/TiO2 (Cu+ rich) catalyst exhibited superior CO oxidation activity compared to CuOx/TiO2 (Ov rich) catalyst.