Advanced Design and Electrical Properties Simulation of Two-Dimensional Photovoltaic Devices

Advanced Design and Electrical Properties Simulation of Two-Dimensional Photovoltaic Device

In Situ STEM Determination of the Atomic Structure and Reconstruction Mechanism of the TiO₂ (001) (1 × 4) Surface

The widely studied anatase TiO₂ (001) surface usually shows a (1 × 4) reconstruction, which may directly influence its physical and chemical properties. Although various atomic models are proposed, the debates regarding the models and the formation mechanism of such reconstruction remain until now due to the lack of direct experimental evidence at the atomic level. Herein, we report the atomic-scale determination of the atomic structure and the reconstruction mechanism of the TiO₂ (001) (1 × 4) surface by in situ spherical aberration corrected scanning transmission electron microscopy (STEM) at elevated temperature. The atomic features of the reconstructed surface are unambiguously identified in our experiments, providing a solid evidence to verify the ad-molecule model, which was predicted by the calculations 15 years ago. Furthermore, the mysterious reconstruction route is revealed by our real time STEM images, which involves a new metaphase of the (001) surface. These results are expected to help resolve current dispute concerning the reconstruction models and understand the true performances of the anatase TiO₂ (001) surface

Real-Time Observation of Reconstruction Dynamics on TiO₂(001) Surface under Oxygen via an Environmental Transmission Electron Microscope

The surface atomic structure has a remarkable impact on the physical and chemical properties of metal oxides and has been studied extensively by scanning tunneling microscopy. However, acquiring real-time information on the formation and evolution of the surface structure remains a great challenge. Here we use environmental transmission electron microscopy to directly observe the stress-induced reconstruction dynamics on the (001) surface of anatase TiO₂. Our in situ results unravel for the first time how the (1 × 4) reconstruction forms and how the metastable (1 × 3) and (1 × 5) patterns transform into the (1 × 4) surface stable structure. With the support of first-principles calculations, we find that the surface evolution is driven by both low coordinated atoms and surface stress. This work provides a complete picture of the structural evolution of TiO₂(001) under oxygen atmosphere and paves the way for future studies of the reconstruction dynamics of other solid surfaces

Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C₂ Hydrocarbons

One-step purification of ethylene (C2H4) from ternary C2 hydrocarbon mixtures is a crucial task and an enduring challenge because of their similar molecular size and physical properties. Owing to their intriguing structural dynamics, flexible MOFs have attracted more attention for gas adsorption and separation. Herein, we report a flexible MOF FJI-W-66 that exhibits rarely seen “breathing” behaviors for C2 hydrocarbons. Upon activation, the channels of guest-free FJI-W-66a significantly contract to a nearly closed-pore state. FJI-W-66a shows the stepwise adsorption isotherms for C2 hydrocarbons, which suggests the occurrence of structural transformation between less open and more open phases. Breakthrough experiments provide evidence that FJI-W-66a can selectively separate C2H4 from C2H2/C2H4/C2H6 mixtures with different ratios under ambient conditions, realizing the one-step acquisition of C2H4 from ternary C2 hydrocarbons