Effect of Ti3+ on TiO2-supported Cu catalysts used for CO oxidation.

In this paper, we have shown that Cu/TiO2 catalysts are highly active in CO oxidation. For instance, a 3.4% Cu/TiO2 catalyst exhibits a higher turnover rate for the effective removal of CO in air than 3–5% Pt/TiO2 and 20% Cu/ZnO/Al2O3 catalysts. A small amount of Cu+ species is formed during the calcination treatment at 225 °C, which is the main active phase for the CO oxidation. However, it is proposed that some highly dispersed CuO can also form in the TiO2 lattice during the calcination treatment. Furthermore, a strong electron interaction between Cu2+ in highly dispersed CuO and Ti3+ on rutile TiO2 (Cu2++Ti3+→Cu++Ti4+) has been shown to occur. Overall, the reduction of Cu+ is a major factor that contributes to the reaction rate of the CO oxidation.