In Situ Resolving the Atomic Reconstruction of SnO₂ (110) Surface

Understanding surface reconstruction of nanocrystals is of great importance to their applications, however it is still challenging due to lack of atomic-level structural information under reconstruction conditions. Herein, through in situ spherical aberration corrected scanning transmission electron microscopy (STEM), the reconstruction of nanocrystalline SnO₂ (110) surface was studied. By identifying the precise arrangements of surface/subsurface Sn and O columns through both in situ bright-field and high-angle annular dark-field STEM images, an unexpected added Sn₂O model was determined for SnO₂ (110)-(1 × 2) surface. The protruded Sn^δ+ of this surface could act as the active sites for activating O₂ molecules according to our density functional theory (DFT) calculations. On the basis of in situ observation of atomic-level reconstruction behaviors and DFT calculations, an energy-driven reconstruction process was also revealed. We anticipate this work would help to clarify the long-standing debate regarding the reconstruction of SnO₂ (110) surface and its intrinsic property.