The influence of ceria on Cu/TiO2 catalysts to produce abundant oxygen vacancies and induce highly efficient CO oxidation†
Ce and Cu species deposited on TiO2 (CuCex/TiO2) are employed as catalysts for CO oxidation. The CuCex/TiO2 catalysts can apparently provide a higher turnover frequency (TOF) rate and lower activation energy than a Cu/TiO2 catalyst without a Ce additive. Compared to a CuCe/SiO2 catalyst, TiO2 as a catalyst support can promote a high surface ratio of Cu/Ce and the formation of small CeO2 particles on the Cu/TiO2 catalysts. The presence of a Cu–CeO2 interaction on the CuCex/TiO2 catalysts may increase the likelihood of an increase in the concentration of Ce3+ species and an abundance of oxygen vacancies with the CeO2 particles. The abundance of oxygen vacancies on the CuCex/TiO2 catalysts may result in a high catalytic rate for CO oxidation. Furthermore, the oxygen vacancies can significantly activate the oxygen reactant, thus acting as an oxygen supplier and further catalyzing CO oxidation. The activated oxygen molecule can form active oxygen and/or lattice oxygen to oxidize CO on the Cu surface. On the other hand, a bidentate formate intermediate generated from CO adsorbed on the CuCex/TiO2 surface is also an important factor for high CO oxidation activity. Adsorbed CO at an interface between Cu and CeO2 can combine with nearby active oxygen to form a bidentate formate intermediate that can react with CO to form CO2. In this work, catalyst characterization was performed and reaction kinetics and reaction mechanisms were investigated and correlated to the reaction rate of CO oxidation.