Tracking of Active Sites as Well as the Compositing Effect over a Cu/Ce-Based Catalyst with Superior Catalytic Activity

The replacement of a noble metal catalyst by base metals presents a great challenge for low-temperature CO and volatile organic compounds oxidation. Cu/Ce-based catalysts are expected to achieve this goal with excellent performance, among which the main active sites still need to be further explored. For this reason, CuCe catalysts were further compounded with typical elements (cobalt, Co) to study the main active sites and compositing effect by in-situ enhanced Raman and in-situ ultralow-temperature DRIFTS technologies. The main active site for both CuCe and CuCoCe catalysts was the same Cu-O_V-Ce at the copper-cerium interface, named as asymmetric oxygen vacancy (ASOv). The dispersion of CuO and CeO₂ species was promoted, and the formation energy of ASOv was decreased significantly from 1.502 to 0.854 eV after the addition of Co, which leads to an increase in the ASOv concentration. A small cobalt added can form more Co²⁺ species, improving the activity and stability. The activity of Cu₁Co_0.5Ce₃ catalyst was significantly improved with 100% conversion of CO and toluene at 96 and 227 °C. Here, the ASOv was studied in relative quantification, showing consistency of catalytic activity and ASOv concentration. Meanwhile, the dynamic exchange of ASOv in the reactions was tracked, indicating that the redox equilibrium of ASOv can continuously produce new ASO_V in Cu/Ce-based catalysts that cause long-term catalytic stability. In addition, it is almost difficult for CoCe and CoCu samples to form the ASOv, and the interaction between metals and metals was also weaker than that of CuCe and CuCoCe catalysts.