Cu oxide deposited on shape-controlled ceria nanocrystals for CO oxidation: influence of interface-driven oxidation states on catalytic activity

Abstract

The design of a catalyst with a highly active and stable oxidation state is of great interest in heterogeneous catalysis. Herein, the relationship between catalytic activity and oxidation state on Cu deposited on CeO₂ nanocrystals has been elucidated by varying the shape of the ceria (CeO₂) support. Three types of CeO₂ nanocrystals were prepared for supporting Cu oxide (CuO_x): CeO₂ nanocubes (NCs), nanorods (NRs) and nanospheres (NSs). The Cu oxide deposited on CeO₂NC has shown higher CO oxidation activity at a lower temperature than that over the NR and NS surfaces. Furthermore, characterization of structure and oxidation states revealed that the stable Cu¹⁺ oxidation state on the surface of CuO_x/CeO₂NC formed at a low loading of copper (∼1.5 wt%), which acts as an active site for the CO oxidation. In contrast to the high surface area and redox properties, a systematic catalytic activity trend was observed among the catalysts with the extent of the Cu¹⁺ oxidation state. We demonstrate that the polar (100) surface facets of NCs contribute significantly to the formation of surface hydroxyl groups, which are required for the selective and stable Cu¹⁺ state at a low loading.