Superior catalytic performance of non-stoichiometric solid solution Ce1 − xCuxO2 − δ supported copper catalysts used for CO preferential oxidation

• Non-stoichiometric Cu/Ce0.978Cu0.022O2 − δ catalyst is highly active for CO PROX.
• The temperatures for 50% and 100% CO conversion are only 73 °C and 115 °C.
• The selectivity of oxygen to CO2 can reach as high as 100% at full CO conversion.
• Ce1 − xCuxO2 − δ solid solution remarkably promotes the reducibility of the catalysts.
• Cu+ and Cu0 are the main active sites for CO and H2 oxidation, respectively.

A series of Ce1 − xCuxO2 − δ non-stoichiometric solid solutions and their supported copper catalysts CuO/Ce1 − xCuxO2 − δ (x = 0, 0.005, 0.022, 0.043) were prepared by co-precipitation and deposition–precipitation, respectively. The CuO/Ce1 − xCuxO2 − δ catalysts show high performance for CO preferential oxidation (CO PROX). Multiple techniques of N2 sorption (BET), XRD, Laser Raman spectroscopy (LRS), HRTEM, H2-TPR, O2-TPO, N2O chemisorption and in-situ DRIFTS were used for catalyst characterization. The results of XRD, LRS and H2-TPR conformably indicate that a small amount of Cu2 + ions can be incorporated into the lattice of CeO2, forming non-stoichiometric solid solutions Ce1 − xCuxO2 − δ, which shows much better reducibility than pure CeO2. The supported CuO/Ce1 − xCuxO2 − δ catalysts exhibit remarkably enhanced activity for CO PROX as compared with CuO/CeO2, especially the catalyst CuO/Ce0.978Cu0.022O2 − δ containing 15% Cu, which displays the best CO PROX performance, showing not only the lowest temperature (115 °C) for CO total conversion, but also the 100% selectivity of O2 to CO2 at this temperature. Several aspects including the presence of more oxygen vacancies, the improved reducibility, and stronger capability for CO chemisorption of this catalyst account well for its superior performance for CO PROX. Based upon the in-situ DRIFTS study, it is revealed that Cu+ is the main active site for CO oxidation, while Cu0 is more active for H2 activation and oxidation.