Mixed TiO2 Research Articles

Sunlight responsive superhydrophilic rGO-TiO2 nanocomposite coatings for photovoltaic applications

Transparent, superhydrophilic surfaces have a wide range of applications, especially for self-cleaning coatings in window panes and solar panels. Herein, reduced graphene oxide (rGO) decorated titanium dioxide (rGO-TiO2) nanocomposites (NCs) were synthesized by in-situ hydrothermal method. The X-ray diffraction and Raman spectroscopy confirmed the formation of anatase-brookite mixed phases TiO2 wherein rGO facilitates the anatase-brookite phase transformation. The NCs exhibit the transmittance of ∼79 % in the visible range and the lowest band gap of 3.03 eV. The wettability studies revealed that the films of rGO-TiO2 NCs became superhydrophilic (water contact angle <10°) upon 60 min sunlight exposure.

Competition between surficial and volumetric diffusion in sintering TiO2 polymorphs by molecular dynamics simulation

AbstractThe competition between surficial and volumetric diffusion during the sintering process for ceramic polymorphism at different sintering temperatures is worth deeply exploring. In the current work, various sintering cases of mixed TiO2 nanoparticles with rutile and anatase types were investigated and the effects of crystalline phase, sintering temperature, and particle size on the sintering process were systematically investigated. The difference in thermodynamic stability and surficial activity of the crystalline phase could promote the decomposition and densification of the nanoparticles. Comparing the mixed‐phase sintering process at different sintering temperatures, the results showed that the particle binding process at low temperature relied mainly on surficial diffusion, however, volumetric diffusion played a crucial role at high temperature. The internal occurrence of volumetric diffusion inhibited the surficial diffusion, resulting in a smaller diameter of the sintering neck and a different sintering rate. In the case of sintering three nanoparticles with rutile and anatase types, it could be found that the decomposition of nanoparticles is more uniform in mixed‐phase sintering at high temperatures and the sintering rate is not significantly influenced by the sintering temperature. This work demonstrates the advantage of a mixed‐phase sintering strategy for TiO2 nanoparticles, which could provide insight into ceramic materials with polymorphism.

Varistor response and structural analysation of silver mixed TiO2 (anatase) nanoparticles

Varistor response and structural analysation of silver mixed TiO2 (anatase) nanoparticles

Improved photocatalytic performance of Sn/Cl co-doped TiO2 nanoparticles via a novel volatilization solid solution method

Sn/Cl co-doped TiO2 nanoparticles were synthesized via a novel volatile solid solution method. The effect of SnCl2·2H2O concentration (0–35.4 mol.%) and calcination temperature on thermal effect, crystal structure, morphology, composition, light absorption and photocatalytic performance of TiO2 nanoparticles was investigated by TG-DSC, XRD, SEM, EDS, TEM, HRTEM, SAED, UV–Vis, PL, photocurrent test, EIS and XPS. Results indicate that Sn and Cl are co-doped into TiO2 crystal lattice forming a mixed anatase-rutile TiO2 phase without SnO2 phase when SnCl2·2H2O concentration is below 17.7 mol.%, and excess SnCl2·2H2O caused the rutile SnO2 generation and simultaneous rutile TiO2 disappearance. The degradation efficiency of methyl orange reaches 98.7 % using 17.7 mol.% SnCl2·2H2O modified TiO2 calcined at 380 °C after 2 h of 15 W UV light irradiation, which is 19.72 % and increases by two times compared with that of pure TiO2 (8.98 %) after 2 h of 15 W visible light irradiation, both showing the maximum photocatalytic performance possibly due to the simultaneous increased active surface sites, enhanced light absorption and improved separation efficiency of photogenerated electron-hole pairs resulted from small particle size, reduced energy band gap and formation of mixed anatase-rutile TiO2 phases. Reactive species scavenging experiments revealed that O.-2 and h+ play a dominant role in photodegradation process.

Correction to: Efficiency enhancement due to the combined mixed cation effect and TiO2 nanofiller effect in PEO and ionic liquid-based dye-sensitized solar cells

Correction to: Efficiency enhancement due to the combined mixed cation effect and TiO2 nanofiller effect in PEO and ionic liquid-based dye-sensitized solar cells

Unraveling the origin of the high photocatalytic properties of earth-abundant TiO2/FeS2 heterojunctions: insights from first-principles density functional theory.

Herein, first-principles density functional theory calculations have been employed to unravel the interfacial geometries (composition and stability), electronic properties (density of states and differential charge densities), and charge carrier transfers (work function and energy band alignment) of a TiO2(001)/FeS2(100) heterojunction. Analyses of the structure and electronic properties reveal the formation of strong interfacial Fe-O and Ti-S ionic bonds, which stabilize the interface with an adhesion energy of -0.26 eV Å-2. The work function of the TiO2(001)/FeS2(100) heterojunction is predicted to be much smaller than those of the isolated FeS2(100) and TiO2(001) layers, indicating that less energy will be needed for electrons to transfer from the ground state to the surface to promote photochemical reactions. The difference in the work function between the FeS2(100) and TiO2(001) heterojunction components caused an electron density rearrangement at the heterojunction interface, which induces an electric field that separates the photo-generated electrons and holes. Consistently, a staggered band alignment is predicted at the interface with the conduction band edge and the valence-band edge of FeS2 lying 0.37 and 2.62 eV above those of anatase. These results point to efficient charge carrier separation in the TiO2(001)/FeS2(100) heterojunction, wherein photoinduced electrons would transfer from the FeS2 to the TiO2 layer. The atomistic insights into the mechanism of enhanced charge separation and transfer across the interface rationalize the observed high photocatalytic activity of the mixed TiO2(001)/FeS2(100) heterojunction over the individual components.

Enhanced low-temperature H2-selective catalytic reduction performance and selectivity of Pt/ZSM-5–TiO2 washcoated monolithic catalysts for NOx reduction

Hydrogen-selective catalytic reduction (H2-SCR) is a promising technology for reducing nitrogen oxide (NOx) emissions at low temperatures, but the selectivity of this process is limited by the generation of N2O. To achieve enhanced denitrification (deNOx) performance, H2-SCR catalysts with mixed zeolite and TiO2 supports washcoated on monolithic cordierite were developed. The catalyst support, active metal type and content, and monolithic cordierite cell density significantly influenced the H2-SCR performance. The xPt/TiO2 catalysts (where x is the metal content, wt.%) achieved >90% NOx conversion 135–180 °C, whereas the xPd/TiO2 catalysts exhibited poor H2-SCR activity, with <30% NOx conversion. In contrast to 0.5Pt/TiO2, the 0.5Pt/zeolite catalysts achieved high NOx conversion at 140–150 °C (91% at 140 °C for 0.5Pt/ZSM-5 > 89% at 140 °C for 0.5Pt/BETA >85% at 150 °C for 0.5Pt/SSZ-13), suggesting that zeolite supports significantly promote H2-SCR activity at low reaction temperatures. For the 0.5Pt/ZSM-5 washcoated monolithic catalyst, increasing the cell density from 400 to 900 cpsi significantly improved the NOx conversion from 52% to 90% at 100 °C owing to the increased geometric surface area and open frontal area of monolithic cordierite. For catalyst with mixed supports (0.5Pt/yZSM-5zTiO2) changing the ZSM-5/TiO2 ratio (y:z) from 25:75 to 90:10 increased the low-temperature NOx conversion from 39% to 89% at 100 °C, indicating that the deNOx characteristics can be tuned. With NO as the reactant, the 0.5Pt/90Z10T catalyst produced the lowest N2O share (8–17%) within the temperature window of maximum NOx conversion, resulting in an increased N2 share (83–88%). Thus, the synergetic effect of mixed ZSM-5/TiO2 catalyst supports can enhance low-temperature NOx conversion and mitigate N2O formation.

Fabrication of Smart Ventilation Blocks Enhanced with Mixed TiO2 Nanoparticles for Improved Compressive Strength

Fabrication of Smart Ventilation Blocks Enhanced with Mixed TiO2 Nanoparticles for Improved Compressive Strength

Probing rutile solid-phase crystallization of atomically mixed Mn-alloyed TiO2 coatings through XANES analysis

Probing rutile solid-phase crystallization of atomically mixed Mn-alloyed TiO2 coatings through XANES analysis

Controlling Composite TiO2 Powder Characteristics in the Solid-State Synthesis of BaTiO3 Powders for Improved Sintering and Permittivity: A Comparative Study

In this study, the anatase–rutile phase fraction of TiO2, which would play a vital role in the solid-state synthesis of BaTiO3, was controlled to form a composite phase. The composite TiO2 was applied to a solid-state synthesis reaction, and the tetragonality, dielectric properties, and microstructure of the resulting BaTiO3 powders were analyzed under different synthesis conditions of TiO2. Furthermore, a comparative analysis of solid-state-synthesized BaTiO3 powders prepared using anatase, rutile, and mixed (anatase + rutile) TiO2 was performed to elucidate the mechanism of improvement in the sintering behavior and dielectric properties of the BaTiO3 powder synthesized using the composite TiO2. As a result of applying composite TiO2, BaTiO3 powder with excellent tetragonality was synthesized. In addition, it is effective in powder growth and the control of powder morphology, so sintering and dielectric properties can be improved at relatively low temperatures.

Effect of nano-ceramic coating on surface property and microbial adhesion to poly(methyl methacrylate).

To improve surface properties of poly(methyl methacrylate) (PMMA) using nano-ceramic coatings and assess microbial adherence after long-term use of a chemical cleanser. Thirty-six PMMA samples were fabricated, polished and coated with a nano-thin TiO2 or mixed TiO2 /ZrO2 , with uncoated samples as controls. Six samples in each group (n=12) were soaked in Polident denture cleaner 180 times for 30 min, while six were soaked in deionized water. Surface roughness of PMMA before and after being soaked in Polident was assessed. All samples were subsequently exposed to Candida albicans for 6h and the adherent cells were determined by viable colony count. Two-way analysis of variance was performed for statistical analysis. No significant difference in surface roughness was noted between the uncoated and coated PMMA before soaking. After soaking, surface roughness of the uncoated PMMA increased from 0.164 to 0.532 μm (p < .05). No significant change was observed for TiO2 -coated (0.105-0.143 μm) or TiO2 /ZrO2 -coated PMMA (0.104-0.141 μm). Attachment of C. albicans to PMMA soaked in water showed significantly less attachment to both TiO2 -coated (1.4 × 103 cfu/ml) and TiO2 /ZrO2 -coated PMMA (1.6 × 103 cfu/ml) than to the uncoated PMMA (2.6 × 103 cfu/ml). After soaking in Polident, the uncoated PMMA had significantly less C. albicans attachment than coated samples. Less attachment was noted on the TiO2 /ZrO2 -coated PMMA then the TiO2 -coated samples (p < .05). Nano-ceramic TiO22 /ZrO2 coating of PMMA denture base material alters surface properties thus reduces oral microbial adhesion. It represents a promising alternative to the chemical disinfection for PMMA denture materials.

Development of maintenance-free coatings using composite titania and silica

Atmospheric conditions and the effect of pollutants on the frequently exposed glass furnishings like windows in constructions and windshield in automotive industries often require maintenance due to their extensive usage and heavy exposure. This demanded an additional coating on the conventional glass furnishings to free from the pollutants without additional cleaning cost. Hydrophilicity and hydrophobicity are properties of titania (TiO2) and silica (SiO2) dielectric materials, although when coated as a composite material, they exhibit a larger affinity for water than carbon contamination. Hence, the contamination adsorbed on the surface of the glass can be easily cleaned by water without help of any detergent or cleaning agents. In this work, we report the fabrication and analysis of three TiO2-SiO2 composite coatings (single coated 1C, double coated 2C and triple coated 3C) on glass substrates using the sol-gel spin coating technique. The coatings were subjected to X-ray diffraction (XRD) analysis, which revealed a broad peak at Bragg angle 25 °, confirming the existence of mixed anatase TiO2 and amorphous SiO2. Fourier transform infrared transmission spectroscopy (FT-IR) studies on the coatings demonstrated peaks at 906 cm−1 and 768 cm-1 that corresponds to the characteristic bond of Si-O-Ti, and stretching bond of Ti-O-Ti respectively. The ultraviolet visible and near-infrared spectroscopy (UV-Vis-NIR) studies on the coatings endorsed 40% reflection in the ultraviolet and near-infrared spectral regions and found increasing the composite coating can increase the reflectance further. Finally, water contact angle (WCA) analysis indicated the hydrophilic character of the coatings, with contact angles of 74.8 ° (1C), 83.3 ° (2C), and 112.7 ° (3C) and suggested as a maintenance free coating on the glass furnishings.

Pyrolysis of Delonix regia using metal oxide catalysts and solvent effect on fuel fraction of bio-oil

Delonix regia (DR) lignocellulosic biomass waste contributes to large quantities of daily solid waste which is having high volatile matter that can be utilized for the production of bio-oil by pyrolysis. The pyrolytic raw bio-oil consists of both fuel and non-fuel fractions which can be separated by organic solvents. Further, application of mixed or individual metal oxide catalysts in pyrolysis reactor along with the feed reduces the corrosiveness and improves stability of pyrolytic bio-oil. Therefore, novelty statement includes catalytic pyrolysis of DR carried out in the presence of mixed metal oxide catalysts, TiO2 and ZnO; followed by separation of fuel and non-fuel fractions of pyrolytic bio-oil using dichloromethane and n-hexane solvents. The improvement of product quality was realized by catalytic activity though the yield is almost unaffected compared to that of non-catalytic pyrolysis. Addition of solvents, helped improving quality of bio-oil by separating out non-fuel phase from it. Each experiment repeated thrice to ensure repeatability and reliability. Higher heating value (HHV) of pyrolytic raw liquid oil increased by 16.2% by the use of catalyst compared to that of non-catalytic pyrolytic raw liquid oil whereas the pH enhanced from 3.72 to 4.77, which indicated catalytic bio-oil has become less acidic. In addition, the physical and fuel properties of fuel fraction obtained by n-hexane are found to be superior to those obtained by dichloromethane. For instant, HHV of fuel portion separated with n-hexane is 23% higher than that obtained with dichloromethane. Density of fuel part obtained by n-hexane was found to be 0.74 g/ml (close to that of commercial gasoline) which is much low as compared to that obtained by using dichloromethane that is having density of 1.01 g/ml. Fourier-Transform InfraRed (FTIR) spectroscopy and proton Nuclear Magnetic Resonance (NMR) spectroscopy of fuel fraction of liquid product indicated partial deoxygenation of bio-oil by separating it with n-hexane.

Aerosol-assisted chemical vapour deposition of highly efficient mixed anatase-rutile TiO2 for photoelectrochemical water splitting

New and bespoke precursors have been used to fabricate mixed anatase-rutile TiO2 with exceptional photoelectrochemical performance towards water splitting.

An optofluidic planar microreactor with photoactive Cu2O/Mo2C/TiO2 heterostructures for enhanced visible light-driven CO2 conversion to methanol

Mixing TiO2 with Mo2C has recently been proposed to improve the photocatalytic conversion of CO2 to methanol under visible light irradiation, although further efforts are still needed to enhance process performance. In this context, the use of p-type semiconductors (i.e., Cu2O) in co-doping strategies can enhance not only the redistribution of electric charges due to its narrowing bandgap, but also the selectivity of the reaction towards methanol. This work focuses on the development of a continuous visible light-driven CO2 photoconversion to methanol process in an optofluidic microreactor using Cu2O/Mo2C/TiO2 heterostructures. A significant improvement in process performance can be seen under visible light with the heterostructures containing 4 wt% of Cu2O. Superior methanol production rates (36.3 µmol∙g−1∙h−1) with an apparent quantum yield = 0.64% and a reaction selectivity = 0.93 are reached, in comparison with the results achieved at Cu2O-free Mo2C/TiO2 photocatalytic surfaces (11.8 µmol∙g−1∙h−1, 0.21% and 0.92, respectively). This can be adscribed to the role of Cu2O in the selectivity of the reaction towards methanol. The synergetic effect between Cu2O, Mo2C, and TiO2 in the heterostructures may also provoke a more efficient charge separation and transfer, while enhancing the visible light absorption properties of the material and its photocatalytic stability. The maximum methanol rate outperforms most of the values previously reported in slurry batch reactors and evidences the possibility of enhancing the continuous visible light-driven CO2-to-methanol photoconversion process with efficient metal co-doping approaches in optofluidic microreactors.

Enhanced visible light sensitized photoreaction by mixed phase titania nanotubes

In this work, we demonstrate the synthesis of mixed crystalline TiO2 nanotubes (TiNT) using a rapid breakdown anodization process and investigate its application in visible light photocatalytic degradation of rhodamine-B (RhB) dye pollutant. Nanotubes with different anatase to rutile crystalline phases were achieved during thermal annealing by tuning the amount of perchlorate ions. Increasing the rutile content decreased the nanotubes' bandgap and surface area. Photocatalytic studies of TiNT with different crystalline phase ratios revealed promising RhB degradation under visible light compared to commercial TiO2. Herein we propose the humidity conditioning (99% relative humidity) of TiNT as a surface modification method to enhance the –OH group on the oxygen defective sites. FTIR and XPS analysis of the TiNT before and after surface modification showed significant change in the surface –OH groups. The surface area normalized apparent-first order kinetic rate constant was higher for all the TiNTs than commercial TiO2. We report for the first time the higher photocatalytic activity of the humidity conditioned nanotubes with high –OH groups compared to the respective catalyst with less –OH group. The simple method proposed for –OH group incorporation shows a possible way of developing an efficient photocatalyst without complex surface modification techniques.

Oxidation behavior of Ti3SiC2 powder synthesized by using biochar, Si and Ti

Biochar was proposed as a novel carbon source for synthesizing Ti3SiC2 powder with high purity by a simple pressureless sintering at 1673 K, and Ti3SiC2 grains exhibited the typical nanolayered structure. The oxidation behavior of Ti3SiC2 powder showed the parabolic law during isothermal oxidation from 1273 K to 1473 K. Dense and continuous oxidation layer consisting of mixed TiO2 and SiO2 was formed rapidly on the surface of Ti3SiC2 particles as a diffusion barrier, which effectively retarded the inward diffusion of oxygen, conferring good oxidation resistance of the powder.

Mixed valence Ce-doped TiO2 with multiple energy levels and efficient charge transfer for boosted SERS performance

Considering the variable valence characteristics of rare earth elements, they can be in a variety of valence forms coexistence. Doping of rare earth element with different valence states may produce different energy levels to tune the semiconductor energy band structure. We utilize rare earth element Ce doping TiO2 for the development of high-performance semiconductor surface-enhanced Raman scattering (SERS) substrates based on an energy-level tuning strategy. Ce doping not only forms multiple energy levels including Ce3+ and Ce4+ metal doping energy levels in the bandgap of TiO2, but also enriches the surface state level of TiO2 itself, which together promote the separation of photogenerated carriers and improve charge transfer efficiency between substrates and absorbed molecules. This endows TiO2 semiconductor substrate with a higher SERS enhancement factor, which can reach 2.2 × 106. The detectable concentration of methylene blue can be as low as 10−10 mol/L. Moreover, the semiconductor substrate exhibits excellent uniformity and stability. This study not only provides a new strategy to develop excellent semiconductor SERS substrate with multiple energy levels, but also lays the foundation for promising practical application of semiconductor substrate.

Branched core-shell a-TiO2@N-TiO2 nanospheres with gradient-doped N for highly efficient photocatalytic applications

A branched core-shell nanosphere composed of an anatase TiO2 (a-TiO2) core and a TiO2 nanobranch shell with gradient-doped N (a-TiO2@N-TiO2) is synthesized by a simple in situ doping method, in which mixed crystal anatase-rutile TiO2 (ar-TiO2) nanosphere is first prepared by oxidizing Ti using H2O2, and then is etched by NH3·H2O to form (NH4)2TiO3 nanobranches, which is converted into a-TiO2@N-TiO2 following an ambient annealing process. The diameter of a-TiO2 core is ∼500 nm, and the thickness of N-TiO2 branched shell is ∼100 nm with gradually increased N concentration from the bottom to the edge. Ultra-thin amorphous coating layers on the branches are also observed. The morphology of the composites could be further tuned by the amount of NH3·H2O, and its effect on the photocatalytic performance is also investigated. The optimized a-TiO2@N-TiO2 shows an outstanding hydrogen evolution rate of 308.1 µmol g−1 h−1 under air mass (AM) 1.5 illumination, and also exhibits highly active in photocatalytic degradation of various refractory organic pollutants, including organic dyes, phenols, antibiotics, and personal care products, with removal ratios higher than 96% after 2 h operation. This can be due to the gradient-doped N-TiO2 nanobranches, which not only provide bending band structure and defect level derived from the N impurities and O vacancies, resulting the formation of n-n+ heterojunctions to improve the charge separation, but also enhance the charge transfer at the liquid-solid interface due to the numerous nanobranches and amorphous coating layers.

Carbon nanosheets wrapped in SnO2–TiO2 nanoparticles as a high performance anode material for lithium ion batteries

Material Nano-genesis has gradually obtained more technical feedback and support in the study of lithium batteries, but problems such as volume expansion still need in-depth study. In this paper, SnO2–TiO2–CNS ternary composites were prepared by hydrothermal method and ball milling. Depending on the layered structure, the SnO2–TiO2 nanoparticles are uniformly attached to carbon nanosheets. It is noteworthy that the volume variation of SnO2 was alleviated by mixed TiO2 and CNS, thus generating a wider space to move around for the lithium ion during the conduction process. The STC was tested for 100 cycles at 0.2 Ag-1 and the capacity was achieved 1046.1 mAhg−1. At 1.0 Ag-1, the capacity of STC can attain 1443.3 mAhg−1 after 1000 cycles. Then, the SEM image of the recovered electrode material was measured, and it was observed that the SnO2–TiO2–CNS composite remained stable.