Abstract
Copper-ceria (Cu-Ce) catalysts with unique catalytic properties have high prospects as alternatives for noble metals in low-temperature catalytic oxidations. However, the quantitative description of the active sites in the redox processes still remains a challenge. Herein, a series of Cu-Ce catalysts were prepared by regulating the synthesis method, AR_(Cu/Ce) (atomic ratios of Cu to Ce), and pH of precipitation, so as to investigate CO and VOCs oxidations. Cu~+-O_v-Ce~(3+) configuration, as an asymmetric oxygen vacancy (ASO_v), was formed in the copper-ceria interface. Its concentration was accurately regulated under varying pH, and was quantificationally identified by ex-situ techniques in static conditions. The maximum ASO_v concentration was recorded for the CuCe3-11 catalyst, accounting for the best catalytic activity and stability. Moreover, the dynamic exchange behaviors (Cu~+-O_v-Ce~(3+)<-> Cu~(2+)-O_((ad))~(2-)-Ce~(4+)) of the ASO_v were quantificationally studied by in-situ techniques under the same reaction conditions. In the oxygen-containing reaction, 13% ASO_v was first converted to Cu~(2+)-O_((ad))~(2-)-Ce~(4+) species, and then wholly recovered in the presence of CO. In the CO oxidation processes, the dynamic exchange of ASO_v maintained equilibrium under T_(50) and T_(100). This work offers future prospects for the quantification tracking of the active sites in catalysts, while also providing a universal strategy for the rational fabrication of high-performance environmental catalysts.
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