Double redox process to synthesize CuO-CeO₂ catalysts with strong Cu-Ce interaction for efficient toluene oxidation

In this study, a novel double redox (DR) method was developed to synthesize highly active CuO-CeO₂ (CuCe-DR) catalyst for catalytic oxidative decomposition of toluene. Compare with CuCe-C catalyst prepared by co-precipitation method, CuCe-DR catalyst exhibits a higher Ce³⁺ ion and incorporated Cu²⁺ ion concentration, and has a stronger Cu-Ce interaction. Ce³⁺ and incorporated Cu²⁺ ions can induce the formation of oxygen vacancies, and thus increasing the amount of surface chemisorbed oxygen on CuCe-DR catalyst. The strong Cu-Ce interaction can promote the electron transfer between CuO and CeO₂, which improves the redox properties of CuCe-DR catalyst. Although CuCe-DR catalyst has a lower toluene adsorption capacity, CuCe-DR exhibits much higher toluene oxidation performance than CuCe-C at the temperature below 300 °C. Moreover, CuCe-DR shows higher stability than CuCe-C during 100 h long-term test due to its high oxygen mobility which inhibits coking. Finally, the possible reaction pathways and promotional mechanism on CuCe-DR in toluene oxidation are proposed. We expect this study to shed more light on the nature of the surface active site(s) of CuCe catalyst for VOCs oxidation and the development of novel redox preparation method for the synthesis highly-active catalysts.