Periodic one-dimensional subsurface channels induced by ordered oxygen vacancies on CeO2 (110)

The distribution and interaction of oxygen vacancies (VOs) critically influence the properties of metal oxides, especially ceria, which is widely used in high-temperature industrial applications. However, VO behavior at elevated temperatures remains poorly understood due to the complexity of their interactions and the lack of predictive models. Here, we uncover a periodic one-dimensional subsurface channel on CeO2 (110), formed by ordered VO distributions at high temperatures. This discovery is enabled by in-situ scanning transmission electron microscopy (STEM), first-principles calculations, and a compressed sensing-assisted cluster expansion model. Strong repulsive interactions between neighboring VOs drive their ordering, which relieves local stress from VOs and polarons and promotes channel formation. A large band gap between the occupied O 2p and unoccupied Ce 4 f band centers helps stabilize this structure. The resulting subsurface channel features sub-nanometer pores and polaron accumulation, enabling directional proton transfer and provides insights into the high catalytic activity of ceria in hydrogenation reactions. These findings not only offer a deeper understanding of VO interactions and their underlying mechanisms but also suggest strategies for tailoring VO behavior in metal oxides for advanced catalytic and energy applications.