Herein, three supported catalysts, CuO/Al 2 O 3 , CeO 2 /Al 2 O 3 , and CuO-CeO 2 /Al 2 O 3 , were synthesized by the convenient impregnation method to reveal the effect of CeO 2 addition on catalytic performance and reaction mechanism for toluene oxidation. Compared with CuO/Al 2 O 3 , the T 50 and T 90 (the temperatures at 50% and 90% toluene conversion, respectively) of CuO-CeO 2 /Al 2 O 3 were reduced by 33 and 39 degrees C, respectively. N 2 adsorptiondesorption experiment, XRD, SEM, EDS mapping, Raman, EPR, H 2 -TPR, O 2 -TPD, XPS, NH 3 - TPD, Toluene-TPD, and in -situ DRIFTS were conducted to characterize these catalysts. The excellent catalytic performance of CuO-CeO 2 /Al 2 O 3 could be attributed to its strong coppercerium interaction and high oxygen vacancies concentration. Moreover, in -situ DRIFTS proved that CuO-CeO 2 /Al 2 O 3 promoted the conversion of toluene to benzoate and accelerated the deep degradation path of toluene. This work provided valuable insights into the development of efficient and economical catalysts for volatile organic compounds. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.