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

The distribution and interaction of oxygen vacancies (V_Os) critically influence the properties of metal oxides, especially ceria, which is widely used in high-temperature industrial applications. However, V_O 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 V_O 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 V_Os drive their ordering, which relieves local stress from V_Os 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 V_O interactions and their underlying mechanisms but also suggest strategies for tailoring V_O behavior in metal oxides for advanced catalytic and energy applications.