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The TiO 2 has the problems of low utilization of visible light and high photogenerated carrier recombination rate. The photocatalytic activity of TiO 2 can be significantly improved by introducing F ion and narrow band gap material Ag 2 S. When F ions are present on the {001} surface of TiO 2 , surface F ions drive positively charged holes across the {001} surface, creating a synergistic effect that promotes the separation of electron-hole pairs. During the sample composite process, a certain amount of Ag will be precipitated to form an all-solid Z-type heterojunction structure of Ag 2 S, Ag and F-TiO 2 , which can improve the electron-hole separation efficiency. The results of XPS characterization confirmed the migration of F ion and the precipitation of Ag. The Ag 2 S/F-TiO 2 composite sample was referred to as AT for short, and the corresponding ratio was 1:10,1:20,1:30,1:40, the optimal sample AT 1:20 degraded 95.6% tetracycline hydrochloride within 2 hours. This work simultaneously realizes TiO 2 self-modification (synergistic effect of F ion migration and TiO 2 {001} crystal surface) and composite modification (formation of all-solid Z-type heterojunction), a new idea of studying TiO 2 self-modified cooperative heterostructures is proposed, and the good application potential of AT nanocomposites in photocatalytic water treatment technology is demonstrated. • The construction of TiO 2 {001} crystal surface and F ion migration have a synergistic effect to improve the electron-hole separation efficiency. • Ag precipitates in the reaction process and constructs a Z-type heterojunction structure with Ag 2 S and F-TiO 2. Ag acts as a bridge for electron transfer and promotes electron transfer. [ABSTRACT FROM AUTHOR]

The spinel LiMn 2 O 4 cathode material shows severe capacity degradation due to Jahn–Teller distortion and dissolution of Mn during the charge-discharge process. Herein, a series of single crystal truncated octahedral of LiFe 0.03 B x Mn 1.97−x O 4 (0≤x≤0.10) were synthesized by simple solid-state combustion combined with Fe-B co-doping, morphology and particle size controlling strategy. Through Fe-B co-doping, not only the LiFe 0.03 Mn 1.97 O 4 containing {111}, {100} and {110} planes are successfully controlled to the particles containing only {111} and {100} planes, but also the near-nanometer particles are controlled to bigger submicron sizes. It is found that Fe-B co-doping can enhance the stability of the crystal structure, inhibit Jahn-Teller distortion and reduce the dissolution of Mn. Among them, the optimized LiFe 0.03 B 0.08 Mn 1.89 O 4 forms a truncated octahedral single crystal particle with good crystallization and only {111} and {100} crystal faces, and the particle size is around 349.3 nm, showing exceptional high rate capacity and long cycle life. The LiFe 0.03 B 0.08 Mn 1.89 O 4 releases a high initial discharge capacity of 107.1 mAh/g with a capacity retention of 77.7% after 1000 cycles at 10 C, which is higher than that of the LiFe 0.03 Mn 1.97 O 4 (58.8%). Even at 20 C, LiFe 0.03 B 0.08 Mn 1.89 O 4 still achieves a high reversible specific capacity (90.4 mAh/g) and outstanding long-cycle stability (81.3%, 1000th). This work provides a scientific basis for the crystal surface control and particle size control of spinel LiMn 2 O 4 , which is of great significance for the development of the next generation of high-power lithium-ion batteries. [Display omitted] • The spinel-type LiMn2O4 was modified by the strategy combining Fe-B co-doping, regulation of crystal surface and particle size. • Through Fe-B co-doping, not only the LiFe0.03Mn1.97O4 containing {111}, {100} and {110} planes are successfully controlled to the particles containing only {111} and {100} planes, but also the near-nanometer particles are controlled to bigger submicron sizes. • The optimized truncated octahedral LiFe0.03B0.08Mn1.89O4 exhibited excellent high rate performance and long cycle life. [ABSTRACT FROM AUTHOR]

In this paper, the molecular adsorption behavior and photoelectric properties of tungsten trioxide monohydrate (WO 3 ·H 2 O) (002) crystal plane into tungsten trioxide (WO 3) (002) crystal plane were studied by Density Functional Theory (DFT) and Electrochemical Impedance Spectrum (EIS). DFT simulation shows that the adsorption active sites change from two to one after the transformation of WO 3 ·H 2 O (002) crystal plane to WO 3 (002) crystal plane, which further affects the molecular adsorption behavior of the crystal plane. The crystal plane conversion leads to the decrease of the adsorption energy of water (H 2 O) molecules and the increase of the adsorption energy of oxygen (O 2) molecules, which reduces the adverse effect of water molecules on the gas sensing performance of the material and enhances the adsorption of O 2 molecules. Like O 2 molecules and H 2 O molecules, the adsorption of four kinds of organic molecules on two crystal planes will lead to an increase in the conductivity of the crystal plane. The competitive adsorption of organic molecules with O 2 molecules leads to the decrease of the conductivity of both crystal planes. However, acetone (C 2 H 6 CO) molecules are combined in the form of hydrogen bond on the WO 3 ·H 2 O (002) crystal plane, and the contribution to the increase of the conductivity of the crystal plane is significantly higher than that of O 2 molecules. After the conversion to the WO 3 (002) crystal plane, this hydrogen bond disappears. These results were confirmed by EIS test experiments. The UV-Vis diffuse reflectance absorption spectra and photocurrent spectra show that the band gap increases after the WO 3 ·H 2 O (002) crystal plane is converted into the WO 3 (002) crystal plane. Understanding the influence of crystal plane transformation on molecular adsorption behavior and photoelectric properties is of great significance for optimizing the gas sensing properties and regulating the photoelectric properties of materials. • Crystal transformation affects the surface adsorption and photoelectric properties. • Density functional theory is used to simulate the crystal plane molecular adsorption. • The change of the active sites affects the molecular adsorption behavior. • Different molecules have competitive adsorption at the same adsorption active site. • The adsorption of molecules will change the crystal surface conductivity. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) hybrid perovskite single crystals are promising photovoltaic materials. However, the single crystals grown from solution usually respond poorly to light and other charged particles. The 2D (BDA)CsPb 2 Br 7 single crystals (BDA = 1,4-butanediamine) are grown from a supersaturated solution. The macroscopical growth steps are present on the surface, leading to a large leakage current during device operation. The surface defects are removed to expose a clean and flat surface. This well-defined crystallographic surface enables an Ohmic contact with the electrode, which minimized the dark current and baseline drift. Consequently, the assembled devices exhibit an enhanced response to LED light and X-rays, revealing the surface defect to be one of the culprits underneath the poor performance of solution-grown perovskite single crystals. • The (BDA)CsPb 2 Br 7 perovskite single crystal was grown by solution cooling method. • Surface defects worsen the detection performance of crystals for photons and X-rays. • A surface treatment method was used to remove defects and improve device performance. [ABSTRACT FROM AUTHOR]