Ti Bonds Research Articles

Effect of Atomic Oxygen and Electron Irradiation on the Electronic Structure of KTiOPO4 Crystal

AbstractKTiOPO4 (KTP) crystals are prepared by the top‐seeded solution growth method. Effects of space irradiation on KTP crystal structure have been investigated using Space Tribology in‐situ Analysis System: KTP crystal (001) surfaces were irradiated by atomic oxygen (AO) and electron (EL), and the electronic structure was analyzed using X‐ray photoelectron spectroscopy (XPS). The AO has strong oxidizing property which results in decreases in the intensity of C 1s peak. The content of P increases after AO/EL irradiation, while the content of Ti decreases after AO irradiation. The reduced ΔBE (O─P) shows stronger ionicity of P─O bonds after AO/EL irradiation compared with pristine KTP crystal. The deconvolution of O 1s photoemission line reveals that peaks at 530.8–531.0 and 530.1 eV are assigned to O─P and O─Ti bonds, respectively. Additionally, variations in the trend of O─P bond and O─Ti bond contents are resembled to that of P and Ti after AO/EL irradiation.

Photoelectrochemical, photocatalytic and electrocatalytic behavior of titania films modified by nitrogen and platinum species

Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhance the electrocatalytic and photocatalytic activity of the films. Herein, the different approaches of synthesis procedure of Pt- and Pt,N–TiO2 films were used to investigate their effect on the platinum oxidation states. The resulting different species of Pt led to the changes in the electronic structure of TiO2, with consequent bandgap narrowing, anodic shift of the flat band potential, and cathodic shift of the valence band The quantum yield efficiency was correlated with Pt0 atomic content and the relative atomic content of Ptn+–O–Ti fragments, whereas its decrease for some samples can be caused by the presence of N and Ptn+. The highest response for N2O photocatalytic decomposition was observed over Pt,N–TiO2 films. The presence of metal and non-metal species in TiO2 structure resulted in synergistic effect including (1) inhibition of recombination of the electrons and holes and (2) narrowing of the bandgap. Electrocatalytic properties in hydrogen and oxygen evolution reactions were improved by Pt doping. The formed Pt2+–O–Ti bonds rather than Pt nanoparticles are suggested to be responsible for the highest electrocatalytic activity. The additional UV exposure of the electrodes led to Pt NPs aggregation as a result of photodeposition of Pt ions. The mechanism of the Pt2+ photoreduction in TiO2 structure is proposed.

Structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3 from hybrid density functional calculations

The ferromagnetic (FM)-antiferromagnetic (AFM) transition is experimentally observed in Y1-xLaxTiO3. The underlying microscopic mechanism for FM-AFM transition is still an open problem and far from fully understood. Here, structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3 with x = 0, 0.25, 0.5, 0.75, and 1 are studied using hybrid density functional method. Y1-xLaxTiO3 stabilizes in an orthogonal perovskite structure. As x increases, the lattice parameters and unit volume almost increase linearly. Y1-xLaxTiO3 is an FM insulator at x = 0 and 0.25, an A-type AFM insulator at x = 0.5 and 0.75, and a G-type AFM insulator at x = 1. A spin-glass behavior is predicted to emerge at 0.25 < x ≤ 0.5. The calculated lattice parameters, band gaps, and magnetic ground states of Y1-xLaxTiO3 are in good agreement with available experimental data. The Ti–O–Ti bond angels increase with increasing x while the total energy difference between the AFM and FM states decreases and then is less than 0 meV. An FM-AFM phase transition is strongly favored with decrease of the GdFeO3-type distortion. The present study reproduces structural, electronic and magnetic properties of Mott insulating Y1-xLaxTiO3, and interprets well experimentally-observed magnetic phase transition.

Visible light photocatalytic degradation of methylene blue by hydrated titanium dioxide nanoparticles incorporated within rice straw

A novel photocatalyst was successfully synthesized by immobilizing hydrated titanium dioxide (HTO) nanoparticle within rice straw (RS) via a sol–gel method. The HTO nanoparticles were successfully loaded onto the surface of RS confirmed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) model. Through Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR), the formed C–O–Ti bond in RS-HTO gave rise to a strong link and, hence, the charge transportation rate was improved. In the photocatalytic processes, the recombination of electrons and holes was smothered. In addition, thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) proved RS-HTO had good thermal stability. The photocatalytic activity of RS-HTO nanocomposites was measured by the photo-degradation performance of methylene blue (MB) solution under visible light. The study showed that the photo-degradation rate of MB could reach 95.18%, which was higher than RS (approximately 20%). Meanwhile, based on experiment (ESR), MB was degraded by hydroxyl radicals (·OH). These results demonstrated that HTO nanoparticle within RS was an effective method for dyestuffs wastewater treatment.

Strain Engineering of a MXene/CNT Hierarchical Porous Hollow Microsphere Electrocatalyst for a High‐Efficiency Lithium Polysulfide Conversion Process

AbstractTensile‐strained Mxene/carbon nanotube (CNT) porous microspheres were developed as an electrocatalyst for the lithium polysulfide (LiPS) redox reaction. The internal stress on the surface results in lattice distortion with expanding Ti−Ti bonds, endowing the Mxene nanosheet with abundant active sites and regulating the d‐band center of Ti atoms upshifted closer to the Fermi level, leading to strengthened LiPS adsorbability and accelerated catalytic conversion. The macroporous framework offers uniformed sulfur distribution, potent sulfur immobilization, and large surface area. The composite interwoven by CNT tentacle enhances conductivity and prevents the restacking of Mxene sheets. This combination of tensile strain effect and hierarchical architecture design results in smooth and favorable trapping–diffusion–conversion of LiPS on the interface. The Li‐S battery exhibits an initial capacity of 1451 mAh g−1 at 0.2 C, rate capability up to 8 C, and prolonged cycle life.

Inside Cover: Strain Engineering of a MXene/CNT Hierarchical Porous Hollow Microsphere Electrocatalyst for a High‐Efficiency Lithium Polysulfide Conversion Process (Angew. Chem. Int. Ed. 5/2021)

A tensile-strained MXene/CNT porous microsphere was developed by Xin Wang, Zhongwei Chen, and co-workers in their Research Article on page 2371 as an electrocatalyst for high-performance lithium–sulfur batteries. A unique O-Ti-C interface was constructed on the MXene surface through a spray-drying process and heat treatment to produce internal stress, inducing lattice distortion and expansion of the Ti−Ti bonds.

Heteroatom coordination induces electric field polarization of single Pt sites to promote hydrogen evolution activity.

Herein, we reported a kind of single Pt site (Pt-SA) stabilized on an MXene support (Pt-SA/MXene) via the formation of Pt-O and Pt-Ti bonds to effectively catalyze the hydrogen evolution reaction (HER). Due to the local electric field polarization derived from its unique asymmetric coordination, Pt-SA/MXene displays remarkably higher catalytic HER activity in an alkaline electrolyte. In detail, the Pt-SA/MXene electrocatalyst only needs a low overpotential of 33 mV to reach a current density of 10 mA cm-2 and maintains the performance over 27 h. Besides, Pt-SA/MXene also has a competitive mass activity, 23.5 A mgPt-1, at an overpotential of 100 mV, which is 29.4 times greater than that of the commercial Pt/C counterpart. Density functional theory (DFT) calculations revealed that the polarized electric field could efficiently tailor the electronic structure of Pt-SA/MXene and reduce the energy barrier of adsorption/desorption of the H* intermediate step, further improving its HER catalytic activity.

Effect of Laser Texturing and Ti Bond Coat for Film Forming Property of Cold Sprayed Fluoropolymer Coatings

Effect of Laser Texturing and Ti Bond Coat for Film Forming Property of Cold Sprayed Fluoropolymer Coatings

Electrochemical nitrogen fixation via bimetallic Sn-Ti sites on defective titanium oxide catalysts

The efficient adsorption and activation of inert N2 molecules on a heterogeneous electrocatalyst surface are critical toward electrochemical N2 fixation. Inspired by the bimetallic sites in nitrogenase, herein, we developed a bi-metallic tin-titanium (Sn–Ti) structure in Sn-doped anatase TiO2 via an oxygen vacancy induced engineering approach. Density functional theory (DFT) calculations indicated that Sn atoms were introduced in the oxygen vacancy sites in anatase TiO2 (101) to form Sn–Ti bonds. These Sn–Ti bonds provided both strong σ-electron accepting and strong π-electron donating capabilities, thus serving as both N2 adsorption and catalytic N2 reduction sites. In 0.1 M KOH aqueous solution, the Sn-TiO2 electrocatalyst achieved a NH3 production rate of 10.5 μgh−1cm−2 and a corresponding Faradaic efficiency (FENH3) of 8.36% at −0.45 V vs. reversible hydrogen electrode (RHE). Our work suggests the potential of atomic-scale designing and constructing bimetallic active sites for efficient electrocatalytic N2 fixation.

Enabling High Dielectric Response in PVDF/V2C MXene–TiO2 Composites Based on Nontypical V–F–Ti Bonding and Fermi-Level Overlapping Mechanisms

High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO2 with low dielectric constant and V2C MXene with high work function are n...

Structural, mechanical, electronic properties, and Debye temperature of quaternary carbide Ti3NiAl2C ceramics under high pressure: A first-principles study* *Project supported by Fujian Science & Technology Innovation Laboratory for Energy Devices of China (21C-LAB) (Grant No. 21C-OP-202013), the National Natural Science Foundation of China (Grant No. 12064027), the International Science and Technology Cooperation Program of China (Grant No. 2015DFA61800), and the

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material, and it has advantages in certain aspects compared with Ti2AlC, Ti3AlC2, and Ti3SiC2 structural materials. In this paper, quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural, mechanical, electronic properties, and Debye temperature. Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure (0–110 GPa). At zero pressure, quaternary carbide Ti3NiAl2C ceramics only has three bonds: Ti–Al, Ni–Al, and Ti–C. However, at pressures of 20 GPa, 30 GPa, 40 GPa, 60 GPa, and 70 GPa, new Ti–Ni, Ti–Ti, Al–Al, Ti–Al, and Ti–Ti bonds form. When the pressure reaches 20 GPa, the covalent bonds change to metallic bonds. The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72% of its original volume at most. Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics. At 50–60 GPa, its mechanical strength can be comparable to pure tungsten, and the material changes from brittleness to ductility. However, the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure. In addition, we also investigated the Debye temperature, density, melting point, hardness, and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.

Fe1 /TiO2 Hollow Microspheres: Fe and Ti Dual Active Sites Boosting the Photocatalytic Oxidation of NO.

Recently, single-atom catalysts have aroused extensive attention in fields of clean energy and environmental protection due to their unique activity and efficient utilization of the active atoms. It is of great importance but still remains a great challenge to unveil the effect of single atoms on precise catalysis. Herein, it is reported that doping TiO2 hollow microspheres (TiO2 -HMSs) with single atomic Fe can boost the photoreactivity of TiO2 -HMSs towards NO oxidation due to the synergistic effects of atomically dispersed Fe and bonded Ti atom which act as dual active sites. The atomically dispersed Fe atoms occupy the subsurface Ti vacancies, and the interaction between Ti 3d and Fe 3d orbitals result in the formation of FeTi bond. Single atomic Fe modulates the electronic structure of the bonded Ti atoms by electron transfer, which facilitates the adsorption and activation of NO and O2 at Fe and bonded Ti sites, respectively. In addition, the introduction of single atomic Fe sharply suppresses the production of toxic NO2 byproduct. The synergistic effects of the dual active sites then cause a drastic promotion in photocatalytic oxidation of NO.

CHARACTERIZATION OF TALC/TiO2COMPOSITE PARTICLE MATERIAL PREPARED BY MECHANO-CHEMICAL METHOD

Talc/TiO2composite particle was prepared with TiO2coating on the surfaces of the talc particles by mechano-chemical method. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to investigate the microstructures and morphologies of the composite particles. The mechanism of the mechano-chemical reaction was researched by infrared spectra (IR) and X-ray photoelectron spectroscopy (XPS). The prepared talc/TiO2composite particle has similar pigment properties compared with TiO2, with its hiding power 10.45[Formula: see text]g/cm3and whiteness 97.49%. The results show that TiO2coated evenly on the surfaces of the talc particles by Si–O–Ti and Mg–O–Ti bonds through surface dehydroxylation reaction.

Binder-free TiO2 hydrophilic film covalently coated by microwave treatment

A binder-free attachment method for TiO2 on a substrate has been sought to retain high active photocatalysis. Here, we report a binder-free covalent coating of phase-selectively disordered TiO2 on a hydroxylated silicon oxide (SiO2) substrate through rapid microwave treatment. We found that Ti–O–Si and Ti–O–Ti bonds were formed through a condensation reaction between the hydroxyl groups of the disordered TiO2 and Si substrate, and the disordered TiO2 nanoparticles themselves, respectively. This covalent coating approach can steadily hold the active photocatalytic materials on the substrates and provide long-term stability. The binder-free disordered TiO2 coating film can have a thickness (above 38 μm) with high surface integrity with a strong adhesion force (15.2 N) against the SiO2 substrate, which leads to the production of a rigid and stable TiO2 film. This microwave treated TiO2 coating film showed significant volatile organic compounds degradation abilities under visible light irradiation. The microwave coated selectively reduced TiO2 realized around 75% acetaldehyde degradation within 12 h and almost 90% toluene degradation after 9 h, also retains stable photodegradation performance during the cycling test. Thus, the microwave coating approach allowed the preparation of the binder-free TiO2 film as a scalable and cost-effective method to manufacture the TiO2 film that shows an excellent coating quality and strengthens the application as a photocatalyst under severe conditions.

Visible‐light driven photodegradation of phenol over niobium oxide‐loaded fibrous silica titania composite catalyst

AbstractBACKGROUNDHeterogeneous photocatalysis has been demonstrated to be a promising alternative to treating emerging pollutants in wastewater. Phenol, an extremely toxic substance among existing pollutants, can cause long‐term unintended effects when improperly disposed. An effective measure to address this problem is to develop suitable heterojunctions. Among various photocatalyst, titanium dioxide (TiO2) appears to be an excellent photocatalyst in the degradation of organic pollutants.RESULTSSynthetization of well‐constructed heterojunction composite of niobium oxide (Nb2O5) and fibrous silica titania (FST) for enhanced photocatalytic degradation of phenol has been investigated. The photocatalytic performance demonstrated that 5 wt% Nb2O5 loaded on FST (5 Nb/FST) gave the maximum phenol degradation rate (1.70 × 10−2 mM min−1) of 10 mg L−1 phenol at pH 5 using 1000 mg L−1 catalyst within 180 min. Meanwhile, under the same conditions, 1 Nb/FST, FST, 10 Nb/FST and Nb2O5 only delivered 1.51 × 10−2, 1.30 × 10−2, 1.01 × 10−2 and 0.07 × 10−2 mM min−1, respectively. Further phenol photocatalytic degradation routes by 5 Nb/FST reveal that the main intermediates detected are hydroquinone, catechol, maleic, fumaric, and malonic acid.CONCLUSIONIn this work, 5 Nb2O5/FST composite, as an effective‐performance photocatalyst for phenol degradation, was well‐constructed. The advanced activity can primarily be attributed to the regulated Nb2O5 loading with FST and the effect of Nb/FST microsphere heterojunctions, synergistically. Besides, larger crystallite size, high impurity levels and Si‐O‐Nb and Nb–O–Ti bonds, offers excellent phenol degradation. © 2020 Society of Chemical Industry (SCI)

Visible‐light‐driven photocatalytic activity of kaolinite: Sensitized by in situ growth of Cu‐TiO2

AbstractSensitized kaolinite with improved visible‐light catalytic activity was prepared via a facile in‐situ growth of nanosized Cu‐TiO2 on the surface of the sulfated kaolinite impregnated in Cu‐TiO2 sol. The as‐prepared photocatalysts were characterized in terms of various techniques. The transmission electron microscope and energy dispersive spectrometer results revealed that Cu‐TiO2 could grow on the surface of the pretreated kaolinite and the aggregation of Cu‐TiO2 was successfully inhibited. The X‐ray photoelectron spectrum confirmed the formation of AlOTi bonds between Cu‐TiO2 and sulfated kaolinite in the sensitized kaolinite composite. The sensitized kaolinite composite exhibited significantly improved performance in the degradation of Rhodamine B (RhB), leading to about 87% of RhB degradation in 180 min, which is superior to that of the kaolinite, calcined kaolin, and sulfated calcined kaolin under visible‐light irradiation. The superior photodegradation activity of the sensitized kaolinite composite was primarily attributed to the synergetic effect of Cu‐TiO2 sensitization and sulfation, resulting from the efficient transfer and separation of the photo‐induced charge carriers between Cu‐TiO2 and kaolinite.

A systemic study on Gd, Fe and N co-doped TiO2 nanomaterials for enhanced photocatalytic activity under visible light irradiation

In this study, the gadolinium (Gd), iron (Fe), and nitrogen (N) doped TiO2 nanomaterials have been synthesized by a sol–gel method with slight modification. While the effect of Gd on the crystalline morphology, specific surface area, chemical composition, and bandgap of the doped samples have been investigated by SEM, TEM, BET, XRD, UV–vis, and XPS. The bonds of Ti–O–Gd, N–Ti–O, and O–N–Ti induced by Gd and N substitution inside the TiO2 crystal lattice structure have been investigated by XPS. The UV–vis spectra showed that the absorption edges of all doped samples are significantly red-shifted, further extending towards the visible spectrum, owing to the impurity band formation of the above valence band (VB) by doping of N. With the increase in the Gd doping amount, the photocatalytic efficiency of GFNTO (tri-doped samples) followed the sequence: G2.0FNTO > G2.5FNTO > G3.0FNTO > G1.5FNTO > G3.5FNTO > G1.0FNTO. The first-order reaction constant of G2.0FNTO for photodegradation of methylene blue (MB) is ten times higher than that of un-doped TiO2. The significant improvement in the performance of the co-doped sample is due to the finer particle size, larger specific surface area, narrowed bandgap, more defect sites, and oxygen vacancies induced by the substitution of Ti4+ by N, Fe3+, and Gd3+. The recycling experiment showed that the photocatalytic efficiency of G2.0FNTO can still reach 95% after its five cycles, further exhibiting the excellent stability and re-usability.

Mechanism, Thermodynamics and Kinetics of Rutile Leaching Process by Sulfuric Acid Reactions

Rutile decomposition by sulfuric acid, including the formation of two salts, Ti(SO4)2/TiOSO4, is thermodynamically modelled. It is shown that TiO2 can spontaneously dissolve in H2SO4 solutions. However, titania is considered as an inert (ballast) phase component of titanium-containing raw materials due to the decelerated separate nature of such chemical transformations. It is concluded that the hampered related kinetics of dissolution can be attributed to the lability of Ti(IV) cations/the specific engineered features of the hierarchical crystalline structure. It is suggested that the breaking of Ti–O–Ti bonds without additional mechanical strains in crystal lattice geometry becomes more advantageous when smaller negative anions/fluoride ions can be used. The analysis of sulfate-fluoride extraction leaching of titanium confirmed that a decrease in the Gibbs energy in the presence of F occurs. It is indicated by kinetic research studies that the addition of corrosive sodium reagent (NaF) reduces the activation by 45 kJ/mol, which results in intensification. A mechanism is proposed for the interactions involving the Ti–O–Ti cleavage on the surface/the H2SO4-induced Ti dioxide degradation on the sites of defects. Moreover, F acts as a homogeneous/heterogeneous bifunctional catalyst.

Reinvestigation of the photostrictive effect in lanthanum‐modified lead zirconate titanate ferroelectrics

AbstractPhotostriction of lanthanum‐modified lead zirconate titanate (PLZT) was commonly attributed to the combination of anomalous photovoltaic effect and inverse piezoelectric response. Herein, distinct photostrictions are detected in both poled and unpoled PLZT ceramics under 405 and 520 nm laser illuminations. The maximum photostriction around 0.09% is obtained in unpoled PLZT under 405 nm illumination, which is nine times of previously reported value that deduced from poled PLZT. The photoelectric and photovoltaic characterizations of poled/unpoled PLZT further evidence that the detected photostriction shows no direct association with the photovoltage‐induced inverse piezoresponse. The light‐induced microstructure changes observed by in situ piezoelectric force microscopy are revealed by domain evolutions along the boundaries. The possible photostriction mechanism of PLZT is attributed to the strong photo‐induced electron‐lattice coupling, which is suggested by the light‐induced changes of the Zr/Ti‐O‐Zr/Ti bonds reflected by the power‐dependent Raman spectra. This study extends the photostriction of PLZT to visible light range and will also stimulate reappraisal of the underlying mechanism of photostrictive effect involving ferroelectrics.

Lattice-confined Ru clusters with high CO tolerance and activity for the hydrogen oxidation reaction

An efficient catalyst for the hydrogen oxidation reaction (HOR) must maintain an oxide-free metal surface in a relatively high potential range. This requirement automatically excludes ruthenium because it is susceptible to oxidation in the hydrogen adsorption/desorption potential region. Herein we report Ru clusters partially confined in the lattice of urchin-like TiO2 crystals (Ru@TiO2) that can effectively catalyse the HOR up to a potential of 0.9 VRHE with a mass activity higher than that of a PtRu catalyst under both acidic and basic conditions. Moreover, the HOR activity of this Ru@TiO2 catalyst is not affected by 1,000 ppm CO impurity. Even at a high CO content of 10 vol%, Ru@TiO2 still selectively catalyses the HOR. Confined Ru clusters grow along the lattice of TiO2 with abundant Ru–Ti bond formation. Such atomically connected co-crystals offer efficient electron penetration from electron-rich TiO2 to Ru metal, leading to sluggish CO adsorption kinetics during the HOR. Efficient hydrogen oxidation catalysts must maintain an oxide-free metal surface in a relatively high potential range. Now, a catalyst consisting of Ru clusters partially confined in the lattice of urchin-like TiO2 crystals is shown to catalyse the reaction up to a potential of 0.9 VRHE with high mass activity and CO tolerance under both acidic and basic conditions.