The self-sustained combustion of carbon monoxide (CO) has been studied over the CuCe0.75Zr0.25O delta catalyst by sol-gel method, and compared with the CuCe0.75Zr0.25O delta (H) and CuCe0.75Zr0.25O delta to investigate sensitivity of different active sites, such as dispersed CuO, Cu-Ce and Ce-Zr solid solution. The CuCe0.75Zr0.25O delta (H) is obtained via CuCe0.75Zr0.25O delta sonicated in nitric acid to remove surficial CuO species, and the CuCe0.75Zr0.25O delta is prepared as the reference catalyst. Using the temperature programmed oxidation of CO together with an infrared camera (CO-TPO FLIR75Zr0.25O delta (81 degrees C) > CuCe0.75Zr0.25O delta(H) (131 degrees C) > CuCe0.75Zr0.25O delta (167 degrees C) at the flow rate of 200 mL/min, but also by corresponding limits of lean combustion (equivalence ratio Phi) of 0.06-0.09, 0.10-0.13, 0.24-0.37, respectively, under the flow rate of 100-1000 mL/min. The M-K mechanism, in which adsorbed CO reacts with lattice oxygen, is crucial for all the catalysts via temperature programmed surficial reaction and in situ infrared analysis (TPSR + DRIFT). The sensitivity of active sites as follows: well-dispersed CuO > Cu-Ce solid solution > Ce-Zr solid solution. As rate-determining step for CO self-sustained combustion, CO is preferentially adsorbed on surficial dispersed CuO to yield carbonyls, and then the carbonyls interact with lattice oxygen to form CO2 release. CO is secondly adsorbed on the surficial oxygen of copper and cerium sites in solid solution to yield carbonates. The carbonates formed are more stable and thus CO2 is produced at the lower rate than carbonyls, indicating that the solid solution is less active than dispersed CuO. Exposed Ce3+ favors to form vacancies on the Cu-Ce solid solution surface, which is beneficial to adsorbing both CO and O-2, thus presenting the higher activity than Ce-Zr solid solution. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.