Transformation of novel TiOF2 nanoparticles to cluster TiO2-{001/101} and its degradation of tetracycline hydrochloride under simulated sunlight

Preparation of Zn3Nb2O8 anode material for high-performance lithium/sodium-ion batteries

Niobium-based oxides (M-Nb-O) as promising lithium/sodium-ion storage anode materials have attracted much attention. More types of niobium-based oxides are prepared in order to provide more candidates for anode materials. Herein, Zn3Nb2O8 as a novel intercalation-type anode material has been reported for the first time. Arborescent Zn3Nb2O8 particles (Zn3Nb2O8-A) and stump-like Zn3Nb2O8 particles (Zn3Nb2O8-B) have been prepared by solid-state and solvothermal methods, respectively. Benefiting from the microsized stump-like structure and the exposure of the (110) facet, Zn3Nb2O8-B delivers superior long-term cycling stability with a 139.6% capacity retention (291.8 mA h g-1) over 650 cycles at 0.5 A g-1 and a large reversible specific capacity of 91.4 mA h g-1 at 4.0 A g-1 in lithium-ion batteries. Furthermore, the Zn3Nb2O8-B electrode exhibits outstanding cycling stability (100.1 mA h g-1 with 94.5% capacity retention after 400 cycles at 0.5 A g-1) in sodium-ion batteries. The excellent electrochemical performance of the stump-like Zn3Nb2O8-B materials can be attributed to the exposure of the (110) facet, enlarged interlayer spacing, small charge transfer resistance, and high pseudocapacitive contribution. Therefore, Zn3Nb2O8-B has great application prospects as an anode material for lithium/sodium-ion storage.

Construction of TiO2/TiOF2 heterojunction as a cathode material for high-performance Mg2+/Li+ hybrid-ion batteries

Anatase TiO₂ has attracted significant interest as a cathode material for Mg-ion batteries or Mg²⁺/Li⁺ hybrid-ion batteries. However, owing to the semiconductor property and slower Mg²⁺ diffusion kinetics it still suffers from poor electrochemical performance. Herein, a TiO₂/TiOF₂ heterojunction consisting of in situ formed TiO₂ sheets and TiOF₂ rods, was prepared by adjusting the amount of HF in the hydrothermal process, and used as cathode of Mg²⁺/Li⁺ hybrid-ion battery. The TiO₂/TiOF₂ heterojunction prepared by adding 2 mL HF (TiO₂/TiOF₂-2) exhibits high electrochemical performance, with a high initial discharge capacity (378 mAh/g at 50 mA/g), an outstanding rate performance (128.8 mAh/g at 2000 mA/g), and good cycle stability (capacity retention of 54 % after 500 cycles), which is much superior to that of Pure TiO₂ and Pure TiOF₂. The reactions of Li⁺ intercalation/detercalation in the TiO₂/TiOF₂ heterojunction are revealed by investigating the evolution of the hybrids during different electrochemical states. Moreover, theoretical calculations prove that the Li⁺ formation energy in the TiO₂/TiOF₂ heterostructure is much lower than that of TiO₂ and TiOF₂, demonstrating that the heterostructure plays a crucial role in the enhanced electrochemical performance. This work provides a novel method to design cathode materials with high performance by constructing heterostructure.

The Ovs surface defecting of an S-scheme g-C3N4/H2Ti3O7 nanoheterostructures with accelerated spatial charge transfer

Semiconductor photocatalysis was a rising star in the sustainable transformation of solar energy for environmental problems governance. Herein, an S-scheme g-C₃N₄/H₂Ti₃O₇ heterostructure was constructed and applied to tetracycline hydrochloride (TCH) destruction. The g-C₃N₄/H₂Ti₃O₇ composite has a superior photocatalytic property to degrade TCH in contrast with bare g-C₃N₄ and H₂Ti₃O₇. The 20% g-C₃N₄/H₂Ti₃O₇ (CNHTO20) composite exhibited the optimum photocatalytic performance, and the degradation efficiency of 20 mg/L TCH reached 87.37% within 3 h (K = 0.572 min^-1). The affluent active sites of the g-C₃N₄ nanosheet and effective interfacial charge separation of the S-scheme pathway facilitated the excellent performance. Moreover, the ample oxygen vacancies (Ovs) act as the electron mediator, not only reducing the band gap energy by producing the formation of defect levels, but also broadening the photo response range and promoting the interfacial charge transfer. The coordination complexes formed between TCH molecules and Ti (IV) ions in CNHTO20 composites induce strong visible light absorption through ligand-metal charge transfer (LMCT). The Ti⁴⁺/Ti³⁺ metal cycle in CNHTO20 was conducive to the separation of the photogenerated electron-hole pairs on the heterojunction interface as well. The ESR characterization and trapping experiments certified that the dominant substances were OH, O₂^- and h⁺. The AQY calculated by the COD removal rate was 0.16%. Conclusively, the S-scheme heterojunction between H₂Ti₃O₇ and g-C₃N₄ enabled the CNHTO photocatalyst with high redox ability and boosted photocatalytic performance accordingly. This study may shed some enlightenment on the construction of heterojunctions and the realistic treatment of wastewater.

Preparation of a Z-Type g-C3N4/(A-R)TiO2 Composite Catalyst and Its Mechanism for Degradation of Gaseous and Liquid Ammonia

In this study, an (A-R)TiO2 catalyst (ART) was prepared via the sol-gel method, and g-C3N4 (CN) was used as an amendment to prepare the g-C3N4/(A-R)TiO2 composite catalyst (ARTCN). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, N2 adsorption-desorption curves (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of the catalysts. The results showed that when the modifier CN content was 0.5 g, the dispersion of the ARTCN composite catalyst was better, with stronger light absorption performance, and the forbidden band width was smaller. Moreover, the photogenerated electrons in the conduction band of ART transferred to the valence band of CN and combined with the holes in the valence band of CN, forming Z-type heterostructures that significantly improved the efficiency of the photogenerated electron-hole migration and separation, thus increasing the reaction rate. Gaseous and liquid ammonia were used as the target pollutants to investigate the activity of the prepared catalysts, and the results showed that the air wetness and initial concentration of ammonia had a great influence on the degradation of gaseous ammonia. When the initial concentration of ammonia was 50 mg/m3 and the flow rate of the moist air was 0.9 mL/min, the degradation rate of gaseous ammonia by ARTCN-0.5 reached 88.86%, and it had good repeatability. When the catalytic dose was 50 mg and the initial concentration of NH4+ was 100 mg/L, the degradation rate of liquid ammonia by ARTCN-0.5 was 71.60% after 3 h of reaction, and small amounts of NO3- and NO2- were generated. The superoxide anion radical (·O2-) and hydroxyl radical (·OH) were the main active components in the photocatalytic reaction process.

In situ composite of Co-MOF on a Ti-based material for visible light multiphase catalysis: synthesis and the photocatalytic degradation mechanism

A Co-MOF/Ti-based Z-type heterojunction prepared by an in situ growth method exhibits good photocatalytic activity for tetracycline.

Preparation of F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as precursor and its photocatalytic degradation activity

Photocatalytic degradation is an eco-friendly and sustainable method for the treatment of water pollutants especially tetracycline hydrochloride (TCH). Herein, we developed F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as a precursor by simple alkali hydrothermal and ion-exchange methods. The phase structure, surface composition, optical properties, specific surface areas and charge separation were analysed by a series of measurements. The effects of KOH concentration on the structure and properties of H2Ti3O7 were investigated. It is confirmed that the TiOF2/H2Ti3O7 composite can be formed in low concentration KOH solution (1 mol L-1), while the H2Ti3O7 single phase can be formed in high concentration KOH solution (>3 mol L-1). The prepared F-doped H2Ti3O7-{104} nanorods provide a high specific surface area of 457 m2 g-1 and a macroporous volume of 0.69 cm3 g-1. The appropriate mesoporous structure of the photocatalyst makes TCH have a stronger affinity on its surface, which is more conducive to the subsequent photodegradation. Moreover, a synergistic mechanism of photosensitization and ligand-metal charge transfer (LMCT) in the photocatalytic degradation of TCH was proposed. In addition, the prepared F-doped H2Ti3O7-{104} nanorods showed excellent cycle stability and resistance to light corrosion. After five cycles of photodegradation, the degradation rate of TCH was only reduced from 92% to 83%. This low-cost strategy could be used for the mass production of efficient photocatalysts, which can be used for TCH clean-up in wastewater treatment.

The preparation of three-dimensional flower-like TiO2/TiOF2 photocatalyst and its efficient degradation of tetracycline hydrochloride

A kind of high-efficiency photocatalyst of the three-dimensional flower-like TiO2/TiOF2 was synthesized by a one-step hydrothermal method. XRD, FE-SEM, EDS, HTEM, BET, XPS, PL, and UV-Vis-DRS were utilized to characterize the photocatalyst. The photocatalyst of TiO2/TiOF2 shows a narrow band gap of 2.8 eV. The generation of Ti3+ and an oxygen vacancy (Ov) in the photocatalyst are helpful to increase the absorption of visible light, and to inhibit faster charge recombination by capturing photogenerated carriers. Through the degradation of tetracycline hydrochloride (TCH) under simulated sunlight, the photocatalytic activity and stability of the synthesized samples were investigated. The results showed that the removal rate of tetracycline hydrochloride was 59% only in 0.5 h of dark reaction and 85% in 0.5 h of simulated sunlight. The removal efficiency of the photocatalyst for the adsorption and photocatalytic degradation of TCH is higher than that of the single TiO2, TiOF2, and Degussa P25. The synthesized three-dimensional flower-like TiO2/TiOF2 has great application potential in the treatment of antibiotic wastewater.