TiCl4 Research Articles

Titanium Tetrachloride-Assisted Direct Esterification of Carboxylic Acids.

Ester compounds, widely found in pharmaceutical and natural products, play a crucial role in organic synthesis, prompting the development of numerous methods for their synthesis. An important chemical approach in synthesizing esters from carboxylic acids involves the activation of the carboxyl function, requiring the conversion of the hydroxyl group into a suitable leaving group. This paper presents the findings of our investigations into an efficient method for producing esters from carboxylic acids and alcohols, using the Lewis acid titanium tetrachloride. Titanium tetrachloride has proven highly effective as a coupling reagent for the one-pot formation of esters from carboxylic acids and alcohols operating under mild and neutral conditions. Notably, the reaction eliminates the need for bases, yielding carboxylic esters in high purity and yields. The method is efficient, even with long-chain carboxylic acids, and operates well with primary alcohols in dichloromethane. Steric hindrance, potentially present in carboxylic acids, has a moderate effect on the reaction. Alcohol substrates that easily form stable carbocations require, instead, the use of non-polar solvents like hexane for the reaction.

The Use of the Titanium Tetrachloride (Ticl4) Catalysts as a Reagent for Organic Synthesis

Abstract: TiCl4 is a widely utilized reagent in organic synthesis, often functioning through Lewis’s acid-promoted transformations. This review explores the potential for TiCl4 to catalyse various examples, adhering to the classic catalyst definition and allowing for the use of sub-stoichiometric quantities of the catalyst relative to the substrate. The use of metal catalysts in organic synthesis has witnessed a surge in interest due to their ability to facilitate a wide range of chemical reactions. This review article highlights the significance of titanium metal catalysts via comparison with other metal catalysts like Pd [NO3]2, IrO4, Au/Fe2O3, SnCl2, and AlCl3. Among these catalysts, titanium tetrachloride (TiCl4) has gained considerable popularity for its cost-effectiveness, eco-friendliness, enhancing reaction efficiency, and ability to accelerate reactions while reducing reaction times. This comparison helps in determining the most suitable catalyst for different chemical processes, considering efficiency, safety, and economic factors. TiCl4 operates as a non-consumable catalyst, allowing for the use of sub-stoichiometric quantities relative to the substrate. This review discusses TiCl4's applications, efficiency, and mechanisms in organic synthesis. It distinguishes itself by presenting new applications and comparative efficiencies of TiCl4, delving into detailed reaction mechanisms, and discussing its environmental, economic, and safety aspects. TiCl4's role in pivotal chemical reactions, such as Friedel-Crafts acylation and alkylation, epoxidation, cyclization, Mannich reactions, Suzuki-Miyaura reactions, Pechmann condensation, Knoevenagel condensation, anti-Markovnikov hydration, pinacol coupling, and Diels-Alder reactions. These reactions have led to the synthesis of biologically active compounds like zolmitriptan, ropinirole, risperidone, and rivastigmine. TiCl4-catalyzed reactions are characterized by their mild conditions, high efficiency, and selectivity, making them an attractive choice for modern organic cyclic, acyclic, and heterocyclic synthesis.

Design of a 130 MW Axial Turbine Operating with a Supercritical Carbon Dioxide Mixture for the SCARABEUS Project

Supercritical carbon dioxide (sCO2) can be mixed with dopants such as titanium tetrachloride (TiCl4), hexafluoro-benzene (C6F6), and sulphur dioxide (SO2) to raise the critical temperature of the working fluid, allowing it to condense at ambient temperatures in dry solar field locations. The resulting transcritical power cycles have lower compression work and higher thermal efficiency. This paper presents the aerodynamic flow path design of a utility-scale axial turbine operating with an 80–20% molar mix of CO2 and SO2. The preliminary design is obtained using a mean line turbine design method based on the Aungier loss model, which considers both mechanical and rotor dynamic criteria. Furthermore, steady-state 3D computational fluid dynamic (CFD) simulations are set up using the k-ω SST turbulence model, and blade shape optimisation is carried out to improve the preliminary design while maintaining acceptable stress levels. It was found that increasing the number of stages from 4 to 14 increased the total-to-total efficiency by 6.3% due to the higher blade aspect ratio, which reduced the influence of secondary flow losses, as well as the smaller tip diameter, which minimised the tip clearance losses. The final turbine design had a total-to-total efficiency of 92.9%, as predicted by the CFD results, with a maximum stress of less than 260 MPa and a mass flow rate within 1% of the intended cycle’s mass flow rate. Optimum aerodynamic performance was achieved with a 14-stage design where the hub radius and the flow path length are 310 mm and 1800 mm, respectively. Off-design analysis showed that the turbine could operate down to 88% of the design reduced mass flow rate with a total-to-total efficiency of 80%.

Synthesis and characterization of pyrrole-based group 4 PNP pincer complexes

The synthesis, characterization, and reactivity of several group 4 metal complexes featuring a central anionic pyrrole moiety connected via CH2 linkers to two phosphine donors is described. Treatment of [P(NH)P-iPr] with [MCl4(THF)2] (M = Zr, Hf) in the presence of base yields the dimeric complexes [M(PNPiPr)(μ-Cl)(Cl)2]2 featuring two bridging chloride ligands. These complexes react with sodium cyclopentadienyl and SiMe3I to give the mononuclear complexes [M(PNPiPr)(η5-Cp)(Cl)2] and [M(PNPiPr)(I)3], respectively. The latter react with MeMgBr to form the trialkyl complexes [M(PNPiPr)(Me)3]. Upon treatment of [Ti(NMe2)4] with [P(NH)P-iPr] a complex with the general formula [Ti(PNPiPr)(NMe2)3] is obtained. DFT calculations revealed that the most stable species is [Ti(κ1N- PNPiPr)(NMe2)3] featuring a κ1N-bound PNP ligand. When [P(NH)P-iPr] is reacted with [Ti(NMe2)4] in CH2Cl2 complex [Ti(PNPiPr)(Cl)2(NMe2)] is formed. Treatment of a solution of [P(NH)P-iPr] and [Zr(NMe2)4] with SiMe3Br affords the anionic seven-coordinate tetrabromo complex [Zr(PNPiPr)(Br)4][H2NMe2]. The corresponding hafnium complex [Hf(PNPiPr)(Br)4][H2NEt2] is obtained in similar fashion by utilizing [Hf(NEt2)4] as metal precursor. All complexes are characterized by means of NMR spectroscopy. Representative complexes were also characterized by X-ray crystallography.Graphical abstract

Nonthermal Plasma Synthesis of Metallic Ti Nanocrystals

Nanoscale metallic titanium (Ti) offers unique energetic and biocompatible characteristics for the aerospace and biomedical industries. A rapid and sustainable method to form purified Ti nanocrystals is still in demand due to their high oxygen affinity. Herein, we report the production of highly purified Ti nanoparticles with a nonequilibrium face center cubic (FCC) structure from titanium tetrachloride (TiCl4) via a capacitively coupled plasma (CCP) route. Furthermore, we demonstrate a secondary H2 treatment plasma as an effective strategy to improve the air stability of a thin layer of nanoparticles by further removal of chlorine from the particle surface. Hexagonal and cubic-shaped Ti nanocrystals of high purity were maintained in the air after the secondary H2 plasma treatment. The FCC phase potentially originates from small-sized grains in the initial stage of nucleation inside the plasma environment, which is revealed by a size evolution study with variations of plasma power input.

Loss Analysis in Radial Inflow Turbines for Supercritical CO2 Mixtures

Abstract Recent studies suggest that CO2 mixtures can reduce the costs of concentrated solar power plants. Radial inflow turbines (RIT) are considered suitable for small to medium-sized CO2 power plants (100 kW to 10 MW) due to aerodynamic and cost factors. This paper quantifies the impact of CO2 doping on RIT design by comparing 1D mean-line designs and aerodynamic losses of pure CO2 RITs with three CO2 mixtures: titanium tetrachloride (TiCl4), sulfur dioxide (SO2), and hexafluorobenzene (C6F6). Results show that turbine designs share similar rotor shapes and velocity diagrams for all working fluids. However, factors like clearance-to-blade height ratio, turbine pressure ratio, and fluid viscosity cause differences in turbine efficiency. When normalized for these factors, differences in total-to-static efficiency become less than 0.1%. However, imposing rotational speed limits reveals greater differences in turbine designs and efficiencies. The imposition of rotational speed limits reduces total-to-static efficiency across all fluids, with a maximum 15% reduction in 0.1 MW CO2 compared to a 3% reduction in CO2/TiCl4 turbines of the same power. Among the studied mixtures, CO2/TiCl4 turbines achieve the highest efficiency, followed by CO2/C6F6 and CO2/SO2. For example, 100 kW turbines achieve total-to-static efficiencies of 80.0%, 77.4%, 78.1%, and 75.5% for CO2/TiCl4, CO2/C6F6, CO2/SO2, and pure CO2, respectively. In 10 MW turbines, efficiencies are 87.8%, 87.3%, 87.5%, and 87.2% in the same order.

Trace elements and growth patterns in quartz from the Alubaogeshan granite in the Maodeng Mo-Bi-Sn-Cu deposit, southern Great Xing’an Range, NE China

The Maodeng Mo-Bi-Sn-Cu deposit is located in the southern segment of the Great Xing’an Range in northeastern China. The Alubaogeshan complex is the major intrusion in this region, which is composed of porphyritic monzogranite (PMG), granite porphyry (GP), and alkali feldspar granite (AFG). We conducted SEM-CL and LA-ICP-MS analyses to examine internal textures and trace elements of quartz from three facies, aiming to uncover the petrogenetic connections among the different lithologies. Quartz phenocrysts from PMG and GP exhibit smudged pre-resorption core, and post-resorption quartz overgrowths with higher Ti concentration and CL intensity, whereas quartz from AFG shows a taxitic structure, with an outward decrease in Ti concentration and CL intensity. There is a positive correlation between CL intensity and Ti content in magmatic quartz. The Al/Ti and Ge/Ti ratios in quartz indicate that the degrees of differentiation of PMG and GP are comparable and relatively low, while that of AFG is high. Trace element contents also exhibit characteristic evolution during magmatic differentiation, with the higher Al, Be, Ge, Rb, and B, and the lower Ti contents in quartz from the highly evolved AFG, and the higher Ti values in quartz from the less evolved PMG. A strong correlation between Al and Li concentrations suggests that Li+ is a primary charge compensator of Al3+ substituting for Si4+ in quartz, with the remaining Al3+ equilibrating with H+. The entry of Al into quartz is mainly controlled by crystallization temperature in the less evolved granite, but magmatic differentiation exerts a key role in the highly evolved granite. Magma differentiation is a primary factor influencing Ge incorporation into quartz. Quartz crystals from PMG and GP display textural and chemical evidence of high-Ti, -CL, and -temperature overgrowth, indicating multiple recharges of mafic magma into the felsic magma chamber. This process could have supplied abundant metals to the granitic magma system and contributed to the formation of the Maodeng deposit.

Titanium in photocatalytic organic transformations: current applications and future developments.

Titanium, as an important transition metal, has garnered extensive attention in both industry and academia due to its excellent mechanical properties, corrosion resistance, and unique reactivity in organic synthesis. In the field of organic photocatalysis, titanium-based compounds such as titanium dioxide (TiO2), titanocenes (Cp2TiCl2, CpTiCl3), titanium tetrachloride (TiCl4), tetrakis(isopropoxy)titanium (Ti(OiPr)4), and chiral titanium complexes have demonstrated distinct reactivity and selectivity. This review focuses on the roles of these titanium compounds in photocatalytic organic reactions, and highlights the reaction pathways such as photo-induced single-electron transfer (SET) and ligand-to-metal charge transfer (LMCT). By systematically surveying the latest advancements in titanium-involved organic photocatalysis, this review aims to provide references for further research and technological innovation within this fast-developing field.

Analysis of degradation effect of carbon nitride nanomaterials in pollutant treatment

Abstract Photocatalytic technology is known as a green technology in solving energy problems and pollution problems, which can generate clean energy and degrade pollutants. In order to study the degradation performance of carbon nitride and its composites on air pollutants and water pollutants, this paper constructs TiO2/g-C3N4 composite photocatalysts by compositing graphite-like phase carbon nitride (g-C3N4) with titanium dioxide (TiO2) using titanium tetrachloride and melamine as raw materials in a water bath method. The physicochemical properties of the prepared complexes were analytically characterized by X-ray diffraction, UV-Vis diffuse reflectance, and X-ray photoelectron spectroscopy, and their degradation activities were examined and compared. The results of all the tests showed that the prepared 5 wt% TiO2/g-C3N4 nanocomposites performed better compared to other mass percentages of nanomaterials. The degradation of pollutants also resulted in better photocatalytic performance of the 5 wt% nanomaterials, with catalytic efficiencies of 54.2% and 99.5% for NO and methylene blue, respectively, at 30 min, and the good photocatalytic activity remained after five cycles.

First Principles Modelling of Growth of Hybrid Organic-Inorganic Films

Hybrid organic-inorganic materials fabricated with molecular layer deposition (MLD) are a special class of materials that are attracting great interest in many economically and socially relevant technological applications due to their diphasic and tunable organic-inorganic structure. Despite the growing interest in these hybrid materials, knowledge around relevant precursor chemistries and reaction mechanisms, as well as details of many determined experimental results are unknown. Density functional theory (DFT) has proven to be a powerful tool to investigate and understand the atomic level details of the precursor chemistry and address aspects of the MLD experiments.In our work, we use first principles DFT calculations to examine key steps in the mechanism of hybrid film deposition through MLD by modelling precursor-surface and precursor-precursor reactions. We explore the growth mechanism of aluminium and titanium containing hybrid films, namely alucones and titanicones. Both materials are of high interest for passivation layers in batteries. For alucones we investigate in detail the chemistry of the MLD process between the post-trimethylaluminium (TMA) pulse methyl-terminated Al2O3 surface with aromatic compounds with hydroxy and/or amino groups as reactive groups: hydroquinone (HQ), 4-aminophenol (AP) and p-phenylenediamine (PD). Double reactions of HQ, AP and PDA with the Al2O3 surface are explored in detail to assist the interpretation of the experimental findings regarding the differences found for hybrid films grown with aromatic and aliphatic organic precursors. DFT calculations show that in contrast to aliphatic organics, an upright configuration will be present for HQ, AP and PD so that the molecules are self-assembled in an upright configuration, which leads to thicker hybrid films. We predict that aromatic molecules are the best choice for stable hybrid films and their chemistry can be manipulated without degrading stability. [1]We also investigate in detail the chemistry between the most common titanium precursors, namely titanium tetrachloride (TiCl4) and tetrakis(dimethylamido)titanium (Ti(DMA)4), and ethylene glycol (EG) and glycerol (GL) as the organic precursors for the fabrication of titanicone films. We analyse the impact of the substrate on the initial MLD reactions in titanicone film growth using three different surface models: anatase TiO2, rutile TiO2 and Al2O3. This work highlights the role of the phase of TiO2 and Ti-containing precursors in production of titanicone films and provides motivation to develop a new rutile TiO2 based hybrid film suggesting that the desired film growth, flexibility and stability can be achieved. [2][1] A. Muriqi, M. Karppinen and M. Nolan, Role of terminal groups in aromatic molecules on the growth of Al2O3-based hybrid materials, Dalton Transactions, 2021, 50, 17583-17593. doi.org/10.1039/D1DT03195C.[2] Arbresha Muriqi and Michael Nolan, “Role of Titanium and Organic Precursors in Molecular Layer Deposition of “Titanicone” Hybrid Materials”, Beilstein Journal of Nanotechnology, 2022, 13, 1240–1255. doi.org/10.3762/bjnano.13.103.

Epoxide-Mediated Synthesis of Two-Component Al2O3–TiO2 Aerogels and Their UV-Protective Characteristics

A new method was proposed to synthesize aerogels based on Al2O3–TiO2 by the hydrolysis of mixed solutions of titanium tetrachloride and aluminum nitrate in the presence of propylene oxide, followed by supercritical drying of the obtained gels. The aerogels are characterized by a high specific surface area (140–500 m2/g) and a high specific porosity (1.7–2.7 cm3/g). Heat treatment of the Al2O3–TiO2 aerogels at temperatures up to 600°C does not lead to crystallization of titanium dioxide, whereas the formation of crystalline anatase in aerogels based on individual TiO2 is observed already at a temperature of 450°C. Using the standardized ISO 24443-2016 method, the SPF value of the obtained materials was determined, which turned out to be comparable to the characteristics of a commercial inorganic UV filter based on TiO2 (Kronos 1171). At the same time, the photocatalytic activity of the Al2O3–TiO2 aerogels turned out to be more than 120 times lower than the similar characteristics of the commercial UV filter based on titanium dioxide. The results obtained demonstrated that the Al2O3–TiO2 aerogels are promising as components of sunscreens.

Silica-supported catalyst for the synthesis of low entangled UHMWPE suitable for solid-state processing

Different types of silica (mesoporous, spherical and nano-size particles), pre-activated with methylaluminoxane (MAO), are used to activate and support the bis[N-(3‑tert-butylsalicydene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride (FI) complex with the aim to synthesize low-entangled UHMWPE having controlled particle morphology. Through the porosity analysis, nitrogen adsorption and desorption isotherms, a decreased surfaced area of the chosen silica is observed when supported by MAO. From the bonding energy study by XPS, the bonding energy difference of Si and O, between the nano-size silica and in the MAO-nano silica, suggests the formation of Al-O-Si after chemical activation with MAO. Using elementary analysis, ICP-OES and XPS characterization, the aluminum content grafted on the silica surface is found to match with the anticipated amount of MAO on the MAO-Silica/FI catalytic system, indicating a stable grafting after catalyst supporting. From the rheological studies of the polymers, coupled with DSC results using an isothermal crystallization protocol, the resultant entangled state in the semi-crystalline polymers is estimated. The observations are that the entangled state achieved during polymerization from the investigated heterogeneous catalytic systems, is the lowest in PE-MAO-nano silica/FI, increases in PE-MAO-mesoporous silica/FI and is highest in PE-MAO-spherical silica/FI. Silica modification using two different silanes shows significant influence on the catalytic activity, giving lower polymer yield in MAO-modified-mesoporous silica and MAO-modified-nano silica compared to the unmodified MAO-silica. Whereas, no significant spatial effect is observed in the formation of chain entanglement, showing the increased entanglement density of the nascent polymers. By employing heterogeneous catalytic systems, reactor fouling and wall sheeting problems are resolved and the polymers show good morphology replication of the support. The UHMWPE synthesized using the nano silica as support, having the lowest entangled state and loosely packed crystals, can be uniaxially processed in the solid-state to a thin tape having thickness around 34 μm, showing maximum tensile strength of 3.26 N/tex and tensile modulus of 170 N/tex.

Influence of diverse MgClx/R’nClmAly(OR)z activators/supports in tailoring of entangled state of UHMWPE

Heterogeneous MgClx/EtnAly(2-ethyl-1-hexoxide)z dual activator/support, together with bis[N-(3‑tert-butylsalicylidene)pentafluoroanilinato] titanium(IV) dichloride complex, has demonstrated its potential in the synthesis of low entangled UHMWPE under controlled polymerization conditions. The work was corroborated with the solid-state processed uniaxial tapes having ultimate mechanical properties, which were found at par with the polymer synthesized using homogeneous catalysis with the edge to govern nascent polymer morphology. The activator/support is tuned depending on the combination of aluminum-alkyls and alcohols employed in the synthesis. Herein, a series of alcohols (2-ethyl-1-hexanol, 3-methyl-1-butanol, n-butanol, n-pentanol, n-octanol, cyclohexanol, and benzyl alcohol) and phenol are employed in the formation of the MgCl2/ROH adduct followed by reaction with different aluminum-alkyls (TEA, DEAC, TiBAl, and TMA) to form a diverse class of MgClx/R’nClmAly(OR)z activators/supports. The diverse activators are employed in the synthesis of low-entangled UHMWPE, the resultant polymers display controlled fine particle morphology without any reactor fouling/wall sheeting. The characteristics of the synthesized polymers are studied using SEM, DSC, melt rheology, high-temperature NMR, and FT-IR. All the synthesized polymers are found to be linear UHMWPE having a reduced number of entanglement, making them suitable (with exceptions) for solvent-free solid-state processing to produce high-strength and modulus tapes. An attempt is made to illustrate the varying entanglement state by correlating the nascent UHMWPE characteristics (such as particle morphology, particulate density, single crystal lamellae structures, storage modulus build-up, and advanced thermal analysis) with the solid-state processing. The resultant catalytic systems of the type Cat. 1/MgClx/R’nClmAly(OR)z are found to form unique nano dual activator/support, crucial for the supporting of a small number of active sites, thus reducing chain overlap during the polymer synthesis. The developed catalytic systems allow tailoring the molecular weight from 3 to 43 million g/mol and Ð from 3.3 to 38 of the synthesized polymers. The mechanical properties are found to be ∼ 4 N/tex of specific strength and > 200 N/tex of specific modulus.

Cl-terminated decoration to modulate the permittivity of MXene for enhanced electromagnetic-absorbing performance

The explosive growth of communication technology has given rise to a large number of high-quality electromagnetic wave (EMW) absorbing materials, and single-component materials are often difficult to satisfy the demand. In this study, we propose an etching method of molten chlorine salts under vacuum to prepare Cl-terminated MXene (MX-Cl) which can meet the requirements of “thin, light, wide and strong” and realize the application of single-component absorbing materials. In the X and Ku bands, MX-Cl achieves a strong reflection loss of –42.99 dB and an effective absorption bandwidth of 3.44 GHz with the 1.2 mm matching thickness. The presence of Cl groups restricts the free electron movement of surface-Ti, which controls the conductivity of the MX-Cl and optimizes its permittivity. Dipole polarization induced by Ti–Cl, interfacial polarization between MXene layers and multiple scattering effects inside the layers all significantly increase the dielectric loss of the MX-Cl considerably. This study provides a new approach to investigating the effect of single atoms on the dielectric properties of materials. This work also offers a simple and low-cost process for the preparation of single-component MXene EMW-absorbing materials.

Pyrrole-Based Ti(III) and Ti(IV) PNP Pincer Complexes: Insertion of Ketones into the Ti(IV)-Phosphorus Bond.

The synthesis, characterization, and reactivity of pyrrole-based Ti(III) and Ti(IV) PNP pincer complexes are described. [P(NH)P-iPr] (1) reacts with [TiCl4(THF)2] at room temperature in the presence of NEt3 to afford the Ti(IV) complex [Ti(PNPiPr)(Cl)3]. This complex reacts with acetone and cyclopentanone to give complexes [Ti(PNOacet-iPr)(Cl)3] and [Ti(PNOcyclo-iPr)(Cl)3], respectively. Insertion of the ketone into the Ti(IV)-P bond took place, forming a new tridendate PNO-ligand. Treatment of [TiCl3(THF)3] with the lithium salt of [P(NH)P-iPr] afforded, upon workup, complex [Ti(PNP-iPr)(Cl)2(THF)], a paramagnetic complex with an μeff value of 1.8(1) μB which corresponds to one unpaired electron and a formal oxidation state of +III. This compound does not react with ketones. A mechanistic proposal based on DFT calculations is presented. Ketone insertion proceeds via an associative reaction initiated by ketone coordination at the metal center, followed by the opening of the five-membered chelate ring, and finally an intramolecular nucleophilic attack of the noncoordinated phosphine arm at the carbonyl atom of the ketone. All complexes were characterized by X-ray crystallography.

Interfacial Engineering for Efficient Low‐Temperature Flexible Perovskite Solar Cells

AbstractPhotovoltaic technology with low weight, high specific power in cold environments, and compatibility with flexible fabrication is highly desired for near‐space vehicles and polar region applications. Herein, we demonstrate efficient low‐temperature flexible perovskite solar cells by improving the interfacial contact between electron‐transport layer (ETL) and perovskite layer. We find that the adsorbed oxygen active sites and oxygen vacancies of flexible tin oxide (SnO2) ETL layer can be effectively decreased by incorporating a trace amount of titanium tetrachloride (TiCl4). The effective defects elimination at the interfacial increases the electron mobility of flexible SnO2 layer, regulates band alignment at the perovskite/SnO2 interface, induces larger perovskite crystal growth, and improves charge collection efficiency in a complete solar cell. Correspondingly, the improved interfacial contact transforms into high‐performance solar cells under one‐sun illumination (AM 1.5G) with efficiencies up to 23.7 % at 218 K, which might open up a new era of application of this emerging flexible photovoltaic technology to low‐temperature environments such as near‐space and polar regions.

Interfacial Engineering for Efficient Low-Temperature Flexible Perovskite Solar Cells.

Photovoltaic technology with low weight, high specific power in cold environments, and compatibility with flexible fabrication is highly desired for near-space vehicles and polar region applications. Herein, we demonstrate efficient low-temperature flexible perovskite solar cells by improving the interfacial contact between electron-transport layer (ETL) and perovskite layer. We find that the adsorbed oxygen active sites and oxygen vacancies of flexible tin oxide (SnO2) ETL layer can be effectively decreased by incorporating a trace amount of titanium tetrachloride (TiCl4). The effective defects elimination at the interfacial increases the electron mobility of flexible SnO2 layer, regulates band alignment at the perovskite/SnO2 interface, induces larger perovskite crystal growth, and improves charge collection efficiency in a complete solar cell. Correspondingly, the improved interfacial contact transforms into high-performance solar cells under one-sun illumination (AM 1.5G) with efficiencies up to 23.7% at 218 K, which might open up a new era of application of this emerging flexible photovoltaic technology to low-temperature environments such as near-space and polar regions.

Effects of mesoporous TiO2 with addition of V2O5 and rinsing with various solvents on the properties of dye-sensitized solar cells

Dye-sensitized solar cells (DSSC) have received much attention since they are simple, easily manufactured, inexpensive, and offer reasonable conversion efficiency. Mesoporous TiO2 with the addition of V2O5 nano-particles (0, 0.5, 1.0, 1.5 and 2.0 wt%) as a photoanode in DSSC have been successfully fabricated using a spin-coating method. Titanium tetrachloride (TiCl4) was used to synthesize a thin TiO2 blocking layer to enhance the performance of TiO2 photoanode in DSSC. After annealing treatment at 450 °C, the TiO2 blocking layer showed an amorphous structure. Performance was examined after soaking N719 dye and rinsing with five different solvents (ethanol, isopropanol, acetone, methanol, and diethyl ether). The results show that removing unanchored dye molecules using acetone solution can increase the specific surface area and dye adsorption amount of TiO2, resulting in good Jsc and photovoltaic efficiency. A conversion efficiency of 8.5% was achieved using fluorine doped tin oxide glass, a thin blocking layer, mixing 0.5 wt% V2O5 with mesoporous TiO2 and rinsing with an acetone solution.

Stable Loading of TiO2 Catalysts on the Surface of Metal Substrate for Enhanced Photocatalytic Toluene Oxidation.

To promote the practical application of TiO2 in photocatalytic toluene oxidation, the honeycomb aluminum plates were selected as the metal substrate for the loading of TiO2 powder. Surface-etching treatment was performed and titanium tetrachloride was selected as the binder to strengthen the loading stability. The loading stability and photocatalytic activity of the monolithic catalyst were further investigated, and the optimal surface treatment scheme (acid etching with 15.0 wt.% HNO3 solution for 15 min impregnation) was proposed. Therein, the optimal monolithic catalyst could achieve the loading efficiency of 42.4% and toluene degradation efficiencies of 76.2%. The mechanism for the stable loading of TiO2 was revealed by experiment and DFT calculation. The high surface roughness of metal substrate and the strong chemisorption between TiO2 and TiCl4 accounted for the high loading efficiency and photocatalytic activity. This work provides the pioneering exploration for the practical application of TiO2 catalysts loaded on the surface of metal substrate for VOCs removal, which is of significance for the large-scaled application of photocatalytic technology.

Reactions of Thianthrene and 10-Phenylphenothiazine with the Lewis Acids─Titanium Tetrachloride, Titanium Tetrabromide, Tin(IV) Tetrachloride, or Antimony(V) Pentachloride: The Competition between Coordination and Oxidation.

The oxidation of thianthrene and 10-phenylphenothiazine into cation radicals has been examined using redox-active Lewis acids. The reaction of titanium(IV) tetrachloride with thianthrene in toluene produces a solution with an EPR spectrum indicative of oxidation of thianthrene to a cation radical, but the molecular compound (1) (μ-thianthrene)Ti2(μ-Cl2)Cl6 crystallized exclusively. Red crystalline (2) (μ-thianthrene)Ti2(μ-Br2)Br6 formed similarly from titanium(IV) tetrabromide. In contrast, the reaction of antimony(V) pentachloride with thianthrene in toluene yielded crystalline (3) (thianthrene·+)2(Sb2(μ-Cl)2Cl62-)·(SbCl3), while the same reaction in acetonitrile produced crystals of (4) (thianthrene·+)(SbCl6-). The two paramagnetic salts differ in that in (3), the folded (thianthrene·+) cation radicals self-associate, whereas in (4), the (thianthrene·+) cation radicals are isolated from one another and are planar. The reaction of 10-phenylphenothiazine with titanium(IV) tetrachloride in toluene solution resulted in the formation of crystalline paramagnetic (5) (10-phenylphenothiazine·+)(Ti(μ-Cl)3Cl6-) and the reaction of 10-phenylphenothiazine with tin(IV) tetrachloride produced paramagnetic (6) (10-phenylphenothiazine·+)(SnCl5-).