A DFT Study of the Extractive Desulfurization Mechanism by [BMIM]⁺[AlCl₄]⁻ Ionic Liquid

In this work, the interaction nature between [BMIM]⁺[AlCl₄]⁻ ionic liquid (IL) and aromatic sulfur compounds (thiophene, benzothiophene, and dibenzothiophene) has been studied by means of density functional theory (M06-2X functional) combined with an implicit solvation model. Although [BMIM]⁺[AlCl₄]⁻ is a metal-containing IL, its extractive desulfurization mechanism is different from other metal-containing ILs but similar to non-metal-containing ILs. Important reactions involved in extractive desulfurization (EDS) were systematically studied. Our results have demonstrated that both the cation and the anion play important roles in EDS. On the basis of the structure analysis, reduced density gradient analaysis (RDG), and energy decomposition analysis, [BMIM]⁺ cation affords a π–π interaction while [AlCl₄]⁻ anion provides a hydrogen bonding interaction. Electrostatic potential analysis implies the dominant π–π interaction and hydrogen bonding interaction are driven by electrostatic interaction between IL and aromatic sulfur compounds. Interaction energy between [BMIM]⁺[AlCl₄]⁻ and thiophene (TH), benzothiophene (BT), and dibenzothiophene (DBT) follows the order TH < BT < DBT. Moreover, Al-containing IL with a high molar ratio of AlCl₃ ([BMIMCl]/2­[AlCl₃]) has also been studied. Results show that [Al₂Cl₇]⁻ species will be formed with excess AlCl₃. However, the [Al₂Cl₇]⁻-based IL cannot improve the EDS performance. Improvement of EDS performance with a high molar ratio of AlCl₃ is credited to the Lewis acidity of AlCl₃. Charge analysis reveals that there is no obvious charge transfer during the reaction, which is different from Fe-containing ILs as well as solid sorbents. In addition, CH−π interaction is not important for the current system

Carbon Quantum Dots Induced Ultrasmall BiOI Nanosheets with Assembled Hollow Structures for Broad Spectrum Photocatalytic Activity and Mechanism Insight

Carbon quantum dots (CQDs) induced ultrasmall BiOI nanosheets with assembled hollow microsphere structures were prepared via ionic liquids 1-butyl-3-methylimidazolium iodine ([Bmim]­I)-assisted synthesis method at room temperature condition. The composition, structure, morphology, and photoelectrochemical properties were investigated by multiple techniques. The CQDs/BiOI hollow microspheres structure displayed improved photocatalytic activities than pure BiOI for the degradation of three different kinds of pollutants, such as antibacterial agent tetracycline (TC), endocrine disrupting chemical bisphenol A (BPA), and phenol rhodamine B (RhB) under visible light, light above 580 nm, or light above 700 nm irradiation, which showed the broad spectrum photocatalytic activity. The key role of CQDs for the improvement of photocatalytic activity was explored. The introduction of CQDs could induce the formation of ultrasmall BiOI nanosheets with assembled hollow microsphere structure, strengthen the light absorption within full spectrum, increase the specific surface areas and improve the separation efficiency of the photogenerated electron–hole pairs. Benefiting from the unique structural features, the CQDs/BiOI microspheres exhibited excellent photoactivity. The h⁺ was determined to be the main active specie for the photocatalytic degradation by ESR analysis and free radicals trapping experiments. The CQDs can be further employed to induce other nanosheets be smaller. The design of such architecture with CQDs/BiOI hollow microsphere structure can be extended to other photocatalytic systems

Nitrogen-Doped Carbon Quantum Dots/BiOBr Ultrathin Nanosheets: In Situ Strong Coupling and Improved Molecular Oxygen Activation Ability under Visible Light Irradiation

Novel nitrogen-doped carbon quantum dots (N-CQDs)/BiOBr ultrathin nanosheets photocatalysts have been prepared via reactable ionic liquid assisted solvothermal process. The one-step formation mechanism of the N-CQDs/BiOBr ultrathin nanosheets was based on the initial formation of strong coupling between the ionic liquid and N-CQDs as well as subsequently result in tight junctions between N-CQDs and BiOBr with homodisperse of N-CQDs. The photocatalytic activity of the as-prepared photocatalysts was evaluated by the degradation of different pollutants under visible light irradiation such as ciprofloxacin (CIP), rhodamine B (RhB), tetracycline hydrochloride (TC), and bisphenol A (BPA). The improved photocatalytic performance of N-CQDs/BiOBr materials was ascribed to the crucial role of N-CQDs, which worked as photocenter for light harvesting, charge separation center for separating the charge carriers, and active center for degrading the pollutants. After the modification of N-CQDs, the molecular oxygen activation ability of N-CQDs/BiOBr materials was greatly enhanced. A possible photocatalytic mechanism based on experimental results was proposed

S, N Codoped Graphene Quantum Dots Embedded in (BiO)₂CO₃: Incorporating Enzymatic-like Catalysis in Photocatalysis

In this study, S, N codoped graphene quantum dots/(BiO)₂CO₃ hollow microspheres have been fabricated by a facile electrostatic self-assembly method. The nanosized S, N:GQDs, which can be obtained by a bottom-up approach, are superior surface modification materials for photocatalytic applications due to their better electron transfer and peroxidase mimetic properties. The excellent oxidation property of the synthesized nanocomposite is confirmed by degradation of different model pollutants, such as rhodamine B, tetracycline, and bisphenol A under light irradiation or dark situation. Based on several experiments, the essential roles of S, N:GQDs can be described as (i) a photocarrier transport center strengthening photoinduced charge carriers (h⁺–e^–) separation and (ii) an enzymatic-like catalysis center to accelerate H₂O₂ decomposition to produce ·OH because the surface accumulation of H₂O₂ is harmful for photocatalytic processes. The present work may pave the way for integrating enzymatic-like cocatalysis into a photocatalytic process to generate more reactive oxygen species, thus advancing the field of environmental remediation and synthetic chemistry

High-Capacity and Long-Cycle Life Aqueous Rechargeable Lithium-Ion Battery with the FePO₄ Anode

Aqueous lithium-ion batteries are emerging as strong candidates for a great variety of energy storage applications because of their low cost, high-rate capability, and high safety. Exciting progress has been made in the search for anode materials with high capacity, low toxicity, and high conductivity; yet, most of the anode materials, because of their low equilibrium voltages, facilitate hydrogen evolution. Here, we show the application of olivine FePO₄ and amorphous FePO₄·2H₂O as anode materials for aqueous lithium-ion batteries. Their capacities reached 163 and 82 mA h/g at a current rate of 0.2 C, respectively. The full cell with an amorphous FePO₄·2H₂O anode maintained 92% capacity after 500 cycles at a current rate of 0.2 C. The acidic aqueous electrolyte in the full cells prevented cathodic oxygen evolution, while the higher equilibrium voltage of FePO₄ avoided hydrogen evolution as well, making them highly stable. A combination of in situ X-ray diffraction analyses and computational studies revealed that olivine FePO₄ still has the biphase reaction in the aqueous electrolyte and that the intercalation pathways in FePO₄·2H₂O form a 2-D mesh. The low cost, high safety, and outstanding electrochemical performance make the full cells with olivine or amorphous hydrated FePO₄ anodes commercially viable configurations for aqueous lithium-ion batteries