Growth Of TiO Research Articles

Regulating the Layer Stacking Configuration of CTF-TiO2 Heterostructure for Improving the Photocatalytic CO2 Reduction.

Herein, covalent triazine frameworks in eclipsed AA and staggered AB stacking modes are respectively used for the in-situ growth of TiO2, and two heterostructures are obtained. Due to the highly organized stacking of the molecular layer in CTF-AA that strengthens the interlayer interaction, the light absorption and carrier migration of CTF-AA/TiO2 are both enhanced in comparison to those of its component or CTF-AB/TiO2. Correspondently, the photocatalytic CO2 reduction reaction (CO2RR) of CTF-AA/TiO2 proffers 9.19 μmol·g-1·h-1 CH4 and 2.32 μmol·g-1·h-1 CO production, about 9.2 and 4.3 times greater than that of pristine TiO2, respectively. Even though the innate photoresponse of the triazine unit endows CTF-AB/TiO2 with augmented light capturing, its photocatalytic CO2 conversion is relatively insignificant. According to the analyses of the planar-averaged electron density difference and Bader charge, the unproductive CO2 efficiency might be due to the insufficient interfacial electron transfer from TiO2 to CTF-AB. Given that the ΔG (-3.22 eV) of CHO intermediate generation is lower than that of CO desorption (-1.23 eV), the reaction tends to further generate CH4 other than yielding CO. This study could shed fresh light over the reasonable design of effective photocatalytic heterostructures.

The synthesis of TiO2 using a nanocrystalline cellulose template improves its photocatalytic performance

Using cellulose nanocrystals (CNCs) as a template in the production of TiO2 has a positive impact on its crystal and porous structure, ultimately improving its photocatalytic performance. In this study, TiO2 photocatalysts with mesoporous anatase structures were prepared by acid-catalyzed hydrolysis using sulfate-ester-modified CNCs as the template. The effects of CNC concentration on the structure and performance of TiO2 were investigated in detail. The addition of CNCs was found to inhibit TiO2 transformation from the anatase to rutile phase, and abundant hydroxyl and sulfate ester groups on the CNCs provide narrow confined spaces for the crystal growth of TiO2, leading to the generation of smaller crystals with more exposed (001) crystal faces. Moreover, the CNCs act as a template for the pore structure remaining after calcination, thus increasing the specific surface area of the TiO2. Among the numerous samples evaluated, that prepared with a CNC concentration of 0.15 wt% and calcined at 600 °C had the highest percentage of (001) crystalline surface exposure. In photodegradation tests using phenol as a model pollutant, a degradation rate of 97.4 % and mineralization rate of 79.9 % were achieved with 60 min of light exposure. Thus, this study provides a clear approach for the directional synthesis of mesoporous TiO2 from biomass template materials.

Fabrication of Silica–Titanium Composite Film on Wood Surface and Optimization of Its Structure and Properties

In this thesis, wood loaded with a silica–titanium (Si-Ti) composite film was prepared using the sol–gel method in order to achieve improved wood with high hydrophobicity and photocatalytic activity under visible light. The factors affecting the structure and properties of the composite film, as well as the optimization process, were discussed. Infrared analysis revealed that the vibrational intensity of Si-O-Si, Ti-O-Ti, and Ti-O-Si telescopic vibration peaks increased with an increase in vinyltriethoxysilane (VETS). Additionally, the number of Ti-O-Ti telescopic vibration peaks also increased with an increase in VETS. Furthermore, the intensity of -NO3, Si-O-Si, and Ti-O-Ti telescopic vibrational peaks was enhanced with a higher dosage of nitric acid. Conversely, the intensity of -OH telescopic vibrational peaks decreased with an increase in drying temperature. XRD analysis showed that nitric acid could promote the transformation of TiO2 from amorphous to anatase, while SiO2 would reduce the grain size of anatase TiO2 and promote the growth of rutile TiO2. Additionally, wood surfaces loaded with Si-Ti composite film changed from hydrophilic to hydrophobic, with significant differences observed between different levels of each factor. The photocatalytic activity of surface-loaded Si-Ti composite films on wood was most affected by the amount of nitric acid, which influenced crystallinity of TiO2 and thus impacted the photocatalytic activity. Furthermore, changes in VTES dosage not only affected the crystalline phase of TiO2 and the grain size of Si-Ti composite film but also influenced the crystallinity of TiO2 through generating SiO2. Finally, based on optimal preparation process (titanium–alcohol ratio of 1:5, titanium–silicon ratio of 1:0.2, titanium–acid ratio of 1:0.5, and drying temperature of 100 °C), wood surfaces loaded with Si-Ti composite film achieved a contact angle up to 125.9° and exhibited a decolorization rate for rhodamine B under UV light reaching 94% within 180 min.

In situ oxidative growth to form compact TiO2–Ti3C2 heterojunctions for photocatalytic hydrogen evolution

Solar photocatalytic hydrogen production shows promise in addressing global energy and environmental concerns. The limited efficiency of photocatalysts is mainly due to ineffective separation and transfer of photogenerated charges. To improve this, we enhance the TiO2–Ti3C2 heterojunction by in-situ oxidation through interfacial engineering, resulting in a more compact composition. Subsequently, we anchor single-atom Pt at the TiO2–Ti3C2 interface through photo-Ti3C2 reduction. The in-situ growth of TiO2 on Ti3C2 introduces an interfacial driving force for carrier separation and provides a channel for electron transfer from TiO2 to Ti3C2. This further facilitates transfer onto Pt, shortening the migration distance and enhancing the photocatalytic efficiency. The best Pt/TiO2–Ti3C2 composite demonstrates an impressive hydrogen precipitation efficiency of 767 μmol g−1 h−1, surpassing TiO2 and Pt/TiO2 by factors of 12 times and 1.46 times, respectively. Furthermore, we developed a higher efficiency photocatalyst using the molten salt method to avoid the risks associated with conventional hydrofluoric acid etching. This research opens up new possibilities for the preparation of MXenes interface-modified catalysts, offering a valuable avenue for future exploration in the field.

Enhanced photocatalytic CO2 reduction over Z-scheme β-Ga2O3/TiO2 heterojunction composite catalyst: Synthesis, performance, and mechanism

TiO2, a highly promising photocatalyst, suffers from rapid recombination of photogenerated electron-hole pairs, which impedes its practical application in industrial aspect. Herein, we report the in-situ solvothermal growth of TiO2 on Ga2O3 to form a composite photocatalyst. Compared to pristine TiO2, the TiO2/Ga2O3 composite exhibited a 2.5-fold enhancement in the photocatalytic reduction of CO2 to CO and a remarkable 9.6-fold increase in CH4 production. Through experimental characterizations and density functional theory (DFT) calculations, the underlying mechanisms for the improved catalytic performance were investigated. The synergistic effects between TiO2 and Ga2O3, including efficient charge separation and transfer, as well as the creation of active sites, are believed to contribute to the enhanced photocatalytic activity of the TiO2/Ga2O3 composite for CO2 reduction. The introduction of the wide bandgap Ga2O3 allowed the formation of a Z-scheme heterojunction with TiO2 at the interface, which greatly improved the efficiency of electron-hole pairs separation and migration, as well as the redox capability, thereby unleashing the performance of the TiO2 catalyst. This approach provides insights into the development of efficient, simple, and low-cost composite catalysts for the photocatalytic reduction of CO2 to valuable fuels.

Structure – Catalytic Behavior Relationships in TiO2-Carbon Composite Supported Pt Electrocatalysts: A Case Study

Composite types of supports made of TiO2 and carbonaceous materials provide higher stability for the Pt electrocatalysts under the working conditions of polymer electrolyte membrane fuel cells than the traditional carbon supports. We have demonstrated in our previous work that composites with general formula of 75 wt.% Ti(1-x)MoxO2-25 wt.% C (x = 0–0.2; C = traditional Black Pearls (BP) carbon) were promising supports which provided increased stability for the Pt electrocatalysts. In this study, the effect of nitrogen doping of the carbonaceous component of the composite was explored. 75 wt.% TiO2-25 wt.% carbon composite supports were prepared using graphite oxide (GO), N-doped GO and N-doped multilayer graphene. Electrocatalysts were made by loading the supports with 20 wt.% Pt. The systems were compared based on their physicochemical properties determined by low-temperature nitrogen adsorption, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and conductivity measurements. The activity of the catalysts was investigated by conventional methods in a 3-electrode electrochemical cell. The results of various characterization methods contributed to the understanding of the difference in the electrochemical properties of N-free and N-containing catalyst samples. While GO was favorable for this composite supported catalyst, its N-doping strongly influenced the growth of TiO2, forming an almost continuous coating of small TiO2 crystals. This quasi-insulating TiO2 layer between the Pt catalytic sites and the conductive part of the composite resulted in poor electrochemical activity. Mixing the sample with carbon improved its conductivity, which resulted in a significant increase in the oxygen reduction activity.

Precursor-concentration-controlled Morphology of TiO2 Nanorod/Nanoflower Films for Enhanced Photoelectrochemical Water Splitting and Investigating Their Growth Mechanism

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts for photoelectrochemical (PEC) water splitting. Therefore, numerous efforts have been devoted to improving its PEC water splitting performance. In this study, TiO2 nanorod/nanoflower (NRF) films with controlled morphology were synthesized on fluorine-doped tin oxide (FTO) glass substrates by following a facile one-step hydrothermal method. The TiO2 NRF films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectrometer (EDS), and ultraviolet-visible (UV-Vis) spectrophotometer. FE-SEM showed that the TiO2 films are composed of a simultaneous growth of a primary layer of TiO2 nanorod arrays (NRAs) and a second layer of TiO2 nanoflowers (NFs). The proposed growth mechanism highlighted the influence of precursor concentration on nucleation sites, affecting the preferred crystallographic plane growth of rutile TiO2 and nanorod alignment on the FTO substrate. Intriguingly, TiO2 NRF films prepared with 1.0 mL of titanium butoxide exhibited a maximum photocurrent density of 3.58 mA.cm−2 at 1.23 V versus (vs.) the reversible hydrogen electrode (RHE), along with a maximum photoconversion efficiency of 0.69%. The enhanced photocurrent density and photoconversion efficiency were attributed to the optimum thickness in the range of 4.52-7.31 µm, which caused the film to be formed with a unique morphology of the primary layer with well-vertically aligned nanorods and the second layer of flowers consisting of numerous rods stacked on top of one another. This study demonstrates the importance of designing semiconductors with 1D nanorod/3D nanoflower structures as high-performance photoelectrodes for PEC water splitting. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Growth of Atomic layer-deposited Monoclinic Molybdenum Dioxide Films Stabilized by Tin Oxide Doping for DRAM Capacitor Electrode Applications.

Dynamic random-access memory (DRAM) capacitor electrodes, exemplified by TiN, face performance limitations owing to their relatively low work functions in addition to the formation of a low-k interfacial layer caused by their insufficient chemical stability. With recent advances in device scaling, these issues have become increasingly problematic, prompting the exploration of alternative electrode materials to replace TiN. Molybdenum dioxide (MoO2) has emerged as a promising candidate for this application, outperforming TiN due to its low resistivity, high work function (>5 eV), and excellent chemical stability. Moreover, monoclinic MoO2 exhibits a distorted rutile structure, enabling the in situ growth of high-k rutile TiO2 on MoO2 at low deposition temperatures. However, MoO2 deposition poses challenges because of its metastable nature compared to the more stable molybdenum oxide (MoOx) phases, such as MoO3 and Mo4O11. In this work, we successfully fabricated Sn-doped MoOx (TMO) films by atomic layer deposition (ALD) at 300 °C. A stabilized monoclinic MoO2 phase was achieved using ALD by incorporating SnOx into MoOx on both SiO2 and TiN substrates. The ALD TMO process comprised MoOx and SnOx subcycles, and the MoOx:SnOx subcycle ratio was varied from 100:1 to 20:1. High growth rates ranging from 0.19 to 0.34 nm/cycle were achieved for ALD TMO with varying the MoOx:SnOx subcycle ratio from 20:1 to 100:0. After post-deposition annealing at 500 °C, polycrystalline TMO films were obtained with smooth surface morphology. ALD TMO exhibited excellent interface quality with ALD TiO2, possessing a negligible low-k interfacial layer. Moreover, a rutile TiO2 film with a high dielectric constant of 136 was successfully grown on a 20% Sn-TMO electrode. Overall, this study provides a strategy to stabilize metastable MoO2 films using ALD, and it demonstrates the superiority of ALD TMO as a promising DRAM capacitor electrode material.

Numerical analysis of Al2O3 and TiO2 growth and oxygen dissolution in a metal substrate during the isothermal oxidation of an α-Ti alloy at 973 K

Oxide growth of Al2O3 and TiO2 as well as O dissolution during the oxidation of an α-Ti alloy at 973 K were simulated using the finite volume method coupled with the calculation of phase diagrams (CALPHAD) method. The results indicated that the addition of 11.02 at.% Al to a Ti–O system resulted in the formation of an 18-nm-thick Al2O3 layer, which decelerated TiO2 growth and O dissolution in the substrate. An increase in the O concentration at the oxide–metal interface was also inhibited by Al2O3 formation. A thin Al-depletion zone was formed at the oxide–metal interface. Furthermore, Al2O3 formation was restricted by the low concentration and diffusivity of Al in the substrate.

Enhanced photocatalytic degradation performance of cornstalk templated TiO2 towards ciprofloxacin in hospital wastewater by the synergistic effect of the (101)/(001) facets coexposed and NiO cocatalyst

In this work, a novel TiO2 photocatalyst (marked as yNiO/5 F-CSTG) was designed and synthesized through a solvothermal pathway assisted with a bio-template, which prefectly combined the strategy of crystalline facet engineering and co-catalyst. The experiment and characterization results indicated that the co-exposure of {101}/{001} facets over TiO2, surface heterojunction and NiO cocatalysts jointly promote the photocatalytic performances, which can be attributed to the high separation efficiency of electron-hole pairs. Additionally, the introduction of morphology regulator (i.e., glycerinum) induced the directional growth of TiO2，being beneficial to broaden the responsive range of visible light. Consequently, compared with pristine TiO2 and CST, the photocatalytic removal rate of 1NiO/5 F-CSTG towards CIP increased ∼24.8 and ∼2.6 times. Besides, for tap-water and hospital sewage, its photocatalytic removal rate reached 89.15 % and 56.32 %, respectively. DFT calculation showed that the F- doping into TiO2 led to the formation of impurity energy level, which contributed to the electron transfer between the co-exposure facets of {101}/{001}. This work provides certain valuable hints for the development of bio-templated photocatalysts.

Activation of polyimide by oxygen plasma for atomic layer deposition of highly compact titanium oxide coating

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film.

Graphene oxide doping in tropical almond (terminalia catappa L.) fruits extract mediated green synthesis of TiO2 nanoparticles for improved DSSC power conversion efficiency

The power conversion efficiency (PCE) of a dye-sensitized solar cell (DSSC) device depends on its semiconductor characteristics. Titanium dioxide (TiO2) nanoparticles are a semiconductor material commonly used in the DSSC device whose characteristics depend on the synthesis process. There are many routes to synthesize TiO2, however, they typically involve hazardous approaches, which may cause risk to the environment. Green synthesis is an environmentally friendly alternative method using ecological solvents that eliminates toxic waste and reduces energy consumption. In this work, tropical almond (Terminalia catappa L.) was used as a natural capping agent in the green synthesis to control the growth of TiO2. In addition, graphene oxide (GO) was used as a dopant to increase the performance of DSSC device. The results are convincing, in which the addition of 0.0017 % GO doping in tropical almond extract mediated green synthesis of TiO2 improved the PCE from 0.85 % to 1.72 %. These results suggest that GO-modified TiO2 nanoparticles green synthesized using tropical almond extract have great potential in the fabrication of DSSC devices with good PCE, low cost, and low environmental impact.

Hydrolysis co-deposition of bio-inspired hybrid hydrophilic network antifouling loose nanofiltration membrane for effective dye/salt separation

Nowadays, loose nanofiltration (LNF) membranes with effective filtration performance toward textile wastewater have drawn intensive attention. In this work, a high-performance LNF membrane was prepared via fast co-deposition of bio-inspired TA-based hydrophilic coating with in-situ hydrolysis of tetra butyl titanate (TBT) on polyethersulfone (PES) substrate. Various additives containing amino acid (l(+)-Arginine) and silane coupling agent (KH792) were mixed in the coating solution and researched their synergistic effects during membrane preparation. In-situ growth of TiO2 and co-deposition of TA-based coating endowed the LNF membrane with a uniformly rough hydrophilic surface. Therefore, the optimal LNF membrane showed a significantly high pure water permeability (92.9 L m−2 h−1·bar−1) with high rejection (>99.0 %) in treating negatively charged dyes including Eriochrome Black T, Congo Red, Chlorazol Black T, and Coomassie Brilliant Blue G. Meanwhile, low rejections for inorganic salts (Na2SO4: 7.9 %, NaCl: 2.5 %, MgCl2: 2.8 %, MgSO4: 7.3 %) were reached, and it kept distinguished separation performance in dealing with highly saline dye wastewater (containing 50 g L−1 NaCl and Na2SO4, respectively). Beyond that, the membrane had excellent antifouling properties with low flux decline of multiple model pollutants and stability during separation dye/salt mixture, which revealed the LNF membrane prepared promising potential in actual textile wastewater treatment.

Preparation and Upscaling of Zeolite@TiO2 Core‐shell for the Removal of Pb(II) and Methylene Blue Dye from Wastewater

AbstractThe present work reports the preparation and adsorption kinetics of a Zeolite@TiO2 multifunctional adsorbent for the removal of heavy metal (Pb(II)) and organic pollutants (methylene blue) from wastewater. The design of the material is a core‐shell having a porous core of zeolite and the surface is supported with the growth of nano TiO2 for a tunable surface and interface designing for efficient wastewater treatment. The formation of Zeolite@TiO2 core‐shell has been characterized by XRD, XPS, SEM, TEM, and DRS spectroscopic techniques. BET surface analysis indicated increased surface area for efficient adsorption. The design of multifunctional adsorbent acts as a charged crossing point for quick adsorption and breakdown of pollutants in water. The adsorption of Pb(II) and methylene blue (MB) dye follows the Freundlich adsorption isotherm confirming presence of multilayer of TiO2 in the adsorption process. Complete adsorption for Pb(II) is achieved in 25 minutes whereas MB dye is completely adsorbed within 15 minutes with high adsorption capacities. Photocatalytic degradation activity for MB dye were also analyzed and indicated 30 mg/l was degraded in 10 min. The DRS and photoluminescence life time study support good photocatalytic activity. The regeneration and recyclability of the core‐shell material have also been studied and reported.

Effect of substrate temperature and annealing on the growth of TiO2‐x thin films deposited by using DC‐magnetron sputtering technique

In this study, the effect of annealing on the structural, surface morphology and chemical structure of titanium suboxide (TiO2‐x) thin films has been investigated. TiO2‐x films had been grown on Si substrates by DC‐magnetron sputtering with different sputter powers (75 and 100 W) at room temperature (RT) and 200°C substrate temperature (ST). The films were subsequently annealed for 1 h at 300, 400 and 500°C in vacuum. The impact of ST, post‐annealing and sputter power on crystallinity, surface morphology and chemical state of the films were studied. Grazing incidence X‐ray diffraction (GIXRD) data revealed that the films were amorphous or exhibited a very low crystalline structure while deposited at RT and even after annealing. Moreover, the films showed crystallinity while deposited at ST and exhibited an anatase‐rutile (A‐R) mix phase from anatase (A) annealed at 300°C (75 W at ST). X‐ray reflectivity (XRR) data showed that the mass density of the films increased with the annealing temperature. Images obtained using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) revealed that post‐annealing increased the surface roughness of the films. X‐ray photoelectron spectroscopy (XPS) analysis indicated the films were sub stoichiometric. It was also indicated that Ti was in the form of Ti4+ and Ti3+ states in all films, and the proportion of Ti4+ slightly increased after post‐annealing at 500°C. The findings showed that post‐annealing, ST and sputtering power can all affect the growth of TiO2‐x films.

Photocatalyst TiO2 assisted preparation by phosphonium ionic liquids enhancing degradation rate of VOCs

A series of TiO2 modified by phosphonium ionic liquids (PILs) and additives containing heteroatoms were synthesized. Among them, P, B, F and P, P, F doped catalysts effectively inhibited the crystal growth of TiO2, decreased the pore size and increased the surface area. What's more, PILs-TiO2 exhibited superior characteristics to those mentioned above. The characterization by FTIR, XPS and EPR demonstrated the generation of chemical bands and the introduction of oxygen vacancies and hydroxyl radicals in the samples. The photocatalytic degradation performance was evaluated and compared under simulated visible light for gaseous toluene. Compared with TiO2, degradation rate increased from 10.28 % to 28.42 %, 41.70 % and 46.23 % for [P4443][Br], [P4443][PF6] and [P4443][BF4] modified TiO2, respectively. In addition, the best photocatalytic degradation rate for T-P/Br, T-P/P/F and T-P/B/F increased to 13.54 %, 42.92 % and 43.78 %, respectively. Synergistic effect of elements in PILs resulted in beneficial photocatalytic degradation, which varied depending on the combination of different elements. Both heteroatoms in PILs and structure of PILs have significant effects on photocatalytic performance. The simulation showed that the presence of compactness of hydrogen bond network formed by PILs was beneficial, which was affected by the number of hydrogen bonds and the anion size.

Defects-rich TiO2(B) in-situ grown on carbon fiber cloth as self-standing electrode for high-loading lithium–sulfur batteries

Poor conductivity, severe shuttling of soluble lithium polysulfides (LiPSs), and sluggish sulfur redox kinetics are inherent issues existing in lithium-sulfur batteries (LSBs). Herein, a self-standing electrode was designed and constructed via the in-situ growth of defects-rich TiO2(B) on a carbon cloth (CC) (denoted as TiO2-x(B)@CC). The strong polarity and high electrochemical activity of TiO2-x(B) enables strong chemical adsorption for LiPSs and catalyzes sulfur conversion reactions. CC as growth substrate inhibits the agglomeration of TiO2-x(B) nanosheets and improves electrical conductivity, as well as holds high sulfur loadings. Benefiting from these synergistic effects, TiO2-x(B)@CC-based cathode with a sulfur loading of ∼ 2.5 mgS cm−2 maintained a high specific capacity of 500 mAh/g over 200cycles at 2.0C. Even under high sulfur loading of ∼ 8.1 mgS cm−2 and a low electrolyte/sulfur (E/S) ratio of ∼ 6.5 μL mgS-1, it still achieved good rate capacities.

Delayed parabolic oxidation via transient thermal exposures on a polycrystalline nickel-based superalloy

Multiple oxides were observed during the transient oxidation stage of the polycrystalline Ni-based superalloy, RR1000, before a protective Cr2O3 scale formed. Thermogravimetric analysis, synchrotron grazing incidence X-ray diffraction, and electron microscopy were performed on samples subjected to isothermal exposures at 800 °C for up to 100 h. Transient effects governed the early stages up to 40 h. NiO, spinels (NiCr2O4, (Ni,Co)(Cr,Co)2O4), Cr2O3/(Cr0.88Ti0.12)2O3, NiTiO3, and CrTaO4 formed during the initial stage with pseudo-linear kinetics. At the onset of parabolic kinetics, extensive Cr2O3 and TiO2 growth dominated scale formation with the former emerging as the major passivating oxide.

In situ growth of TiO2 and its immobilization on PVDF films for the adsorption and photocatalytic degradation of dye

Organic pollutants, such as dyes, contaminated water bodies seriously. Suitable materials and efficient technologies for degrading pollutants needed to be explored to protect the environment and human health. In this investigation, PVDF(PAA-g-β-CD)@TiO2 hybrid film was prepared by a combination of “in situ hydrothermal-vapor induction” under mild conditions. The distribution, particle size, and interaction with the film surface for TiO2 were investigated by XRD, XPS, SEM, and EDS. The TiO2 nanoparticles were firmly immobilized and uniformly distributed on the hybrid film surface. Poly (acrylic acid) (PAA) and β-cyclodextrin (β-CD) on the film matrix were connected by the chemical bond, which provided stable nucleation and growth sites for TiO2 while inhibiting photogenerated electron-hole recombination and significantly enhancing the adsorption ability. Furthermore, the multiple interaction forces (hydrogen bonding, coordination, and hydrophilic-hydrophilic interactions) between the film matrix and the TiO2 were evaluated by simulated geometries and theoretical calculations. The multiple interactions reduced the band gap (Eg) while endowing the hybrid photocatalytic film with excellent degradation efficacy (η), stability, and recycling properties. Finally, the η of methylene blue (MB) reached 97.34 % within 120 min and remained above 90 % even after 8 reuses. It was believed that PVDF(PAA-g-β-CD)@TiO2 film provided an approach for the mild preparation of polymer/TiO2 hybrid film with high catalytic activity and optimization of photocatalytic properties.

Defect-induced regulation of crystal growth and phase transition of TiO2 synthesized from Ti-bearing blast furnace slag

Ti-bearing blast furnace slag (TBFS) is an essential secondary Ti resource for TiO2 production. However, the TiO2 is sintered and does not meet the pigment requirements. This study investigated the effect of surface/bulk distribution of defect structures on the crystal growth and phase transition of TiO2 based on the Rietveld method. For the defects of Xn+ (Al3+/Mg2+/Zn2+), the interstitial Xn+ (Xint) is mainly located on the surface of TiO2 particles and inhibits the crystal growth. The substituted Xn+ (Xsub) is primarily located in the bulk and promotes the phase transition. The radius of Xn+ affects the stability of Xint and determines the distribution of Xint/Xsub. Thus, the major defect structures of Al3+, Mg2+, and Zn2+ (increasing radius) are Alint, Mgint/Mgsub, and Znsub, respectively. Based on this, a new co-doping method was proposed. Co-doping modifies the distribution of Xint/Xsub to regulating the crystal growth and phase transition. Finally, TiO2 for pigment with a small particle size (220 ± 60 nm) and high rutile conversion (98.1%) was synthesized from TBFS. The results will help to optimize the process for producing TiO2 pigment from TBFS and provide new insights into the structure regulation of TiO2 materials.