Comparative study of CeO2/CuO and CuO/CeO2 catalysts on catalytic performance for preferential CO oxidation

The CeO2/CuO and CuO/CeO2 catalysts were synthesized by the hydrothermal method and characterized via XRD, SEM, H2-TPR, HRTEM, XPS and N2 adsorption–desorption techniques. The study shows that the rod-like structure is self-assembled CeO2, and both hydrothermal time and Ce/Cu molar ratio are important factors when the particle-like CeO2 is being self-assembled into the rod-like CeO2. The CuO is key active component in the CO-PROX reaction, and its reduction has a negative influence on the selective oxidation of CO. The advantage of the inverse CeO2/CuO catalyst is that it still can provide sufficient CuO for CO oxidation before 200 °C in the hydrogen-rich reductive gasses. The traditional CuO/CeO2 catalyst shows better activity at lower temperature and the inverse CeO2/CuO catalysts present higher CO2 selectivity when the CO conversion reaches 100%. The performance of mixed sample verifies that they might be complementary in the CO-PROX system.

Graphical abstractFor the inverse CuO/CeO2-D, the CeO2 crystallites (about 3–8 nm) gather into many small islands, which are dispersed on the bulk CuO with 20–50 nm size. The reaction may occur at the contact interface of the CeO2 islands and bulk CuO. For the traditional CuO/CeO2-E, most of CeO2 crystallites (about 5–10 nm) self-assemble into the rod-like CeO2, and CuO as well as particle-like CeO2 with nano size are located on the outside of rod-like CeO2 nanostructures. The active sites are distributed on the outer surface of CeO2 nanorods.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► CeO2/CuO and CuO/CeO2 catalysts were synthesized by hydrothermal method. ► CuO reduction has a negative influence on selective oxidation of CO. ► Traditional CuO/CeO2 catalyst shows better activity at lower temperature. ► CeO2/CuO catalysts present higher CO2 selectivity when CO conversion reaches 100%. ► Performance of mixed sample verifies that they may be complementary in CO-PROX.