Periodic One-Dimensional Subsurface Channels Induced by Ordered Oxygen Vacancies on CeO2 (110)

The distribution and interaction of oxygen vacancies (V _O s) play a crucial role in determining the properties of metal oxides, particularly ceria, which is widely used in high-temperature industrial applications. However, information about V _O behavior at high temperatures is scarce in the literature due to the inherent complexity of V _O interactions and the lack of accurate models to describe and predict these interactions under such conditions. Consequently, the existence of long-range ordered Vos remains elusive. Here, we reveal an unexpected periodic one-dimensional subsurface channel induced by ordered V _O distributions on CeO ₂ (110) at high temperatures, using in-situ scanning transmission electron microscopy (STEM), first-principles calculations, and a compressed sensing-assisted cluster expansion model. The strong repulsive interactions between neighboring V _O s drive their ordered distribution, which, in turn, facilitates the formation of the periodic one-dimensional subsurface channels by relieving stresses induced by V _O s and polarons. The large energy gap between the occupied O 2 p band center and the unoccupied Ce 4 f band center was identified to underpin these processes and maintain this abnormal subsurface channel. This subsurface channel on CeO ₂ (110) exhibits sub-nano-level pores and an accumulation of polarons, making it well-suited for the directional transfer of protons, which provides new insights into the high catalytic activity of ceria in hydrogenation reactions. These findings offer not only a deeper understanding of V _O interactions and their underlying mechanisms but also a new approach for manipulating V _O s for specialized applications.