Titanium Mixed Oxides Research Articles

Bifunctional acid–base strontium–titanium mixed oxides supported on SBA-15 for selective synthesis of renewable branched bio-jet fuel precursor

Herein, furfural, which is a lignocellulose-derived platform chemical, was converted into a bio-jet fuel precursor via aldol condensation with 2-butanone using strontium (Sr) and titanium (Ti) mixed oxides (STO) loaded onto mesoporous silica SBA-15 (SBA15). A series of acidobasic STO/SBA15 catalysts were prepared via incipient wetness impregnation by systematically varying the mixed oxide loading and Sr:Ti molar ratio of the catalysts. The STO/SBA15 catalysts exhibited a well-mesostructured order, high dispersion of metal oxides, and good textural properties. The acidic and basic properties of the catalysts were facilely controlled by varying the metal oxide composition and amount of STO loaded onto the SBA15 support. The aldol condensation was carried out batchwise under a pressurized nitrogen atmosphere. The products formed in the reaction comprised 9–18 carbon atoms. The yield and selectivity of α,β-unsaturated C9 ketone with branched molecular structure (C9B) were strongly influenced by the acid–base properties of the catalyst and the reaction conditions. 20STO(2:1)/SBA15 was the suitable catalyst, realizing > 99% furfural conversion and 78.3% C9B yield under the following optimized conditions: 4 wt% catalyst loading, 1:5 furfural:2-butanone molar ratio, 180 °C reaction temperature, and 5 h reaction time.

Preparation of pH-sensitive surface based on mixed oxides of titanium and iridium for early detection of inflammation around the implant

The surface of an implant used during operation is a preferred site for the attachment of harmful microorganisms. These subsequently affect the surrounding tissue with their metabolic products, including the tissue's pH. The possibility of sensing the pH around the implant could be a way of detecting the infection in the early stages. Transition metal oxides can be used for these applications. The most common alloys used for the manufacture of implants are titanium alloys which are characterized by a passive TiO2 surface layer that can be modified. In this work, the Ti–6Al–4V alloy whose surface was nanostructured was used. Iridium particles were subsequently deposited on the prepared surface by various methods to increase the sensitivity to pH change. The potentiostatic mode was chosen as the most suitable method of deposition. Energy dispersive analysis and X-ray photoelectron spectroscopy verified the success of iridium particle deposition. The electrochemical response was measured in a physiological saline solution and monitoring the open circuit potential change proved to be the most appropriate sensing method. After subsequent oxidation process, the prepared surface showed a sensitivity of 64 mV/pH at 37 °C.

Characterization of spherical silica–titania mixed oxide particles synthesized by using a dry process

Silica–titania mixed oxides have excellent properties, such as a low thermal expansion coefficient and a refractive index that can be adjusted by changing the Ti content. However, when the Ti content increases, silica and titania phases in silica–titania mixed oxides can separate. This phase separation leads to the precipitation of the titania component as rutile or anatase crystals. When silica–titania mixed oxides undergo phase separation, their properties become unstable; for example, the refractive index of the particles becomes non-uniform. Therefore, it is preferable to synthesize silica–titania mixed oxides in an amorphous state without causing phase separation. Based on our previous studies on particle size control in silica synthesis, we employed a dry process using organosilicon compounds to synthesize silica–titania mixed oxides. In this study, spherical amorphous silica–titania mixed oxide particles were obtained via flame synthesis using organosilicon and organotitanium compounds. The purpose of this study was to characterize the obtained powder and explore the possibility of controlling particle size during synthesis. By studying the dry process synthesis of spherical silica–titania mixed oxide particles, we confirmed the relationships: between the Si/Ti molar ratio and the obtained crystal structure and between the adiabatic flame temperature and the particle size.

Influence of various parameters on the current distribution and protection degree of impressed current cathodic protection for reinforced concrete with TiMMO mesh anodes

Impressed current cathodic protection (ICCP) is an effective technique to control reinforcement corrosion in concrete structures. The efficiency and design of an ICCP system with titanium mixed metal oxide (TiMMO) anodes in a mortar overlay is strongly influenced by the current distribution to the different reinforcement layers of a reinforced concrete element. An in-depth experimental study is performed to investigate the effect of various parameters on the current distribution and degree of corrosion protection: (i) chloride content, (ii) cement type, and (iii) reinforcement configuration. 24-hour depolarization measurements (EN ISO 12696:2022) indicate that an increase in chloride concentration in the concrete, related to an increase in the rate of reinforcement corrosion, leads to a general decrease in the degree of protection. The use of a CEM III/A cement leads to a large increase in concrete electrical resistivity compared to concrete with an ordinary Portland cement (CEM I). This causes a lower total current output to the reinforcement and a less uniform distribution of current. Finally, a lower steel reinforcement density resulted in a larger current density, as the total current is distributed over a smaller steel surface area, causing higher depolarization values.

Characterization of thermal and anodic oxide layers on β- and on near-β-titanium alloys for biomedical application

Abstract β- and near-β-Ti alloys for biomedical applications show a favourable mix of mechanical, biological and biocompatible properties. In this study, oxide layers on Ti13Nb13Zr, Ti15Mo5Zr3Al, Ti30Nb and Ti30Ta were prepared by thermal and anodic oxidation, in order to adjust constant, reproducible and well-defined surface properties. The thickness, the phase composition and the element composition of the oxide layers were determined. The corrosion properties were investigated by current density –potential curves under physiological conditions. Depending on the oxidation parameters, film thicknesses in the range 10 – 250 nm can be prepared. The thermal oxide layers consist predominantly of TiO2 in rutile structure while the anodized samples show a mixture of anatase and amorphous TiO2. In addition, certain amounts of mixed oxides of titanium and alloying elements such as TiZrO4 or TiNb2O7 are found in the oxide films. The corrosion resistance of the oxidized samples is increased as compared with the polished samples whose current densities in the range of passivity are comparable to that of Ti6Al4V.

Influence of g-C3N4 doping on the NH3-SCR activity of Cerium–tungsten–titanium mixed oxide catalyst

Influence of g-C3N4 doping on the NH3-SCR activity of Cerium–tungsten–titanium mixed oxide catalyst

Praseodymia-titania mixed oxide supported gold as efficient water gas shift catalyst: modulated by the mixing ratio of oxides.

Modulating the active sites for controllable tuning of the catalytic activity has been the goal of much research, however, this remains challenging. The O vacancy is well known as an active site in reducible oxides. To modify the activity of O vacancies in praseodymia, we synthesized a series of praseodymia–titania mixed oxides. Varying the Pr : Ti mole ratio (2 : 1, 1 : 2, 1 : 1, 1 : 4) allows us to control the electronic interactions between Au, Pr and Ti cations and the local chemical environment of the O vacancies. These effects have been studied study by X-ray photoelectron spectroscopy (XPS), CO diffuse reflectance Fourier transform infrared spectroscopy (CO-DRIFTS) and temperature-programmed reduction (CO-TPR, H2-TPR). The water gas shift reaction (WGSR) was used as a benchmark reaction to test the catalytic performance of different praseodymia–titania supported Au. Among them, Au/Pr1Ti2Ox was identified to exhibit the highest activity, with a CO conversion of 75% at 300 °C, which is about 3.7 times that of Au/TiO2 and Au/PrOx. The Au/Pr1Ti2Ox also exhibited excellent stability, with the conversion after 40 h time-on-stream at 300 °C still being 67%. An optimal ratio of Pr content (Pr : Ti 1 : 2) is necessary for improving the surface oxygen mobility and oxygen exchange capability, a higher Pr content leads to more O vacancies, however with lower activity. This study presents a new route for modulating the active defect sites in mixed oxides which could also be extended to other heterogeneous catalysis systems.

Metal Substitution in Rutile TiO2: Segregation Energy and Conductivity

State-of-the-art acidic oxygen evolution reaction catalysts are mainly based on mixed oxides of titanium and iridium or ruthenium. Because of its high chemical corrosion resistance and stability in acid, $${\hbox {TiO}_2}$$ is a promising support material, yet with poor electrical conductivity. We herein theoretically examined the stability and the electronic properties of substituted rutile-phase titania, in which Ti is partly replaced by elements of the fourth, fifth and sixth period. For negative values of the calculated segregation energy, we conclude that the heteroelement M forms a solid solution for 25% or 50% substitution. For these heteroelements, we calculate the electrical conductivity. Since it is known that the electronic structure of transition metal oxides strongly depends on the applied theoretical method, we performed self-consistent optimizations of the Hartree-Fock contribution to the exchange functional in a hybrid functional for every compound. Experimentally, two favorable and two unfavorable elements were synthesized with 25% foreign metal concentration. The most promising candidates to improve the electronic properties of titania are Ta and Nb.

Microwave-assisted sol–gel synthesis of TiO2-mixed metal oxide nanocatalyst for degradation of organic pollutant

Abstract Titanium dioxide (TiO2) is the most effective photocatalysts for low-cost degradation of organic pollutant; however, the wide band gap and the high recombination rate of the charge carriers are drawbacks that hinders it practical application. In this study, TiO2 and titanium mixed metal oxides ternary (V/Ag/TiO2) nanocatalyst was synthesized through a microwave-assisted sol–gel route using Ti(C4H9O)4, NH4VO3, and AgNO3 as precursors. The XRD analysis of the synthesized TiO2 and V/Ag/TiO2 depicts lattice fringes for rutile and anatase crystalline phases. Raman spectra indicate the formation of a mesoporous multiphase sample mixture of rutile and anatase phases. The spectrum shift to the visible light region was demonstrated by the UV-visible spectroscopy analysis. Diffuse reflectance spectroscopy (DRS) reveals a reduced band gap of 2.9 eV for TiO2 and 2.65 eV for V/Ag/TiO2. Brunauer–Emmett–Teller (BET) indicates a large surface area of 92.8 and 84.8 m2 g−1 for TiO2 and V/Ag/TiO2, respectively. Nitrogen adsorption–desorption isotherm exhibits type IV isotherm, signifying the presence of the mesoporous structure. SEM portrays a cluster of rod-like aggregate particles, while the HRTEM analysis illustrates nanoparticles of rod-like cylindrical shape with a homogeneous size diameter. The synthesized nanocatalyst demonstrated a significant photocatalytic ability in the degradation of methyl orange (MO) and methylene blue (MB). V/Ag/TiO2 shows higher activity in the visible region. Thus, the present report suggests efficient, suitable, and economical microwave-assisted sol–gel techniques to yield V/Ag/TiO2 nanocatalysts with harnessed photocatalytic performance for the degradation of toxic organic pollutants in the presence of visible light irradiation.

Selective catalytic reduction of NOx with NH3 over cerium–tungsten–titanium mixed oxide catalyst: Synergistic promotional effect of H2O2 and Ce4+

Abstract

Optimal synthesis of aromatic carbonyl compounds by electrooxidation of soda lignins on stainless steel and TiMMO anodes

Electrooxidation (EO) studies were conducted on wheat straw soda lignin (WSSL), and bagasse soda lignin (BSL) for the synthesis of aromatic carbonyl compounds (COarom). Stainless steel (SS), and titanium mixed metal oxide (TiMMO) anodes were used for the purpose. Experiments were designed according to Box Behnken Design (BBD), and Central Composite Design (CCD). The process parameters, namely EO current density, and EO time, were optimized using Response Surface Methodology (RSM) to obtain the maximum yields of different COarom, individually as well as collectively. A maximum of 30% cumulative yield of COarom, based on the total amount of lignin, could be obtained from BSL under optimized conditions of 2.24 mA.cm-2 EO current density, and 18 h EO time using SS anode. Among individual compounds, vanillin was produced with the highest yield of 20% of starting BSL with EO current density, and EO time optimized to 5.87 mA.cm-2, and 18 h, respectively. In all cases, SS anode fares better than TiMMO anode.

Investigation of the CdS quantum dot sensitized solar cells based on a series of zinc titanium mixed metal oxides

In this work, a series of zinc titanium mixed metal oxides obtained from the zinc titanium layered double hydroxides as precursor were prepared as the photoanode material of the CdS quantum dot-sensitized solar cells. CdS quantum dots were deposited on photoanodes by the successive ionic adsorption and reaction method. It was investigated that the effects of photoanode based on different Zn–Ti molar ratios on the photovoltaic performance of solar cells. The essential parameters of samples were investigated by UV–vis absorption spectrum, incident photon-to-current conversion efficiency, photoelectric conversion efficiency and electrochemical impendence spectrum. The varying Zn–Ti ratios influence adsorption properties and charge mobility. As a result, the cells based on Zn–Ti MMOs achieved an optimum power conversion efficiency of 2.71% when the Zn–Ti ratio is 7:1.

Laser ablation of silicon monoxide and titanium monoxide in liquid: formation of mixed colloidal dispersion with photocatalytic activity

Silica–titania mixed oxides and composites have been extensively studied, whereas to the titanium monoxide (TiO) –silicon monoxide (SiO) counterparts has been devoted very little attention. Laser ablation of SiO and TiO in liquids is in according with literature completely unexplored. Here we report on Nd:YAG pulse laser ablation of SiO and TiO in ethanol which allows generation of SiO- and TiO-based nanoparticles and their agglomerates.Mixed SiO-TiO colloid has been prepared by simple mixing of ablatively prepared individual colloids in 1:1 volume ratio. Measurement of size distribution by Dynamic Light Scattering (DLS) determines sizes of 24.85 nm and 262.3 nm for SiO colloid, 494.8 nm for TiO colloid and 35.2 nm and 397.5 nm for mixed colloid. Zeta potential values suggest incipient instability for all measured systems. Morphology of the particles captured on Ta substrate by evaporation of ethanol was studied using Scanning Electron Microscopy (SEM). Round-shaped, oval, and sheet-like particles and their agglomerates have been observed. Raman spectroscopy of the mixed SiO-TiO colloid revealed multiphase structure consisting of anatase and/or rutile, crystalline and amorphous silicon and silica and crystalline and amorphous titanium silicide TiSi2. Formation of TiSi2 demonstrates unexpected low temperature disproportionation of SiO and TiO-based species and mutual reducing interactions. Catalytic activity of individual SiO and TiO colloids and of their mixture has been tested in terms of methylene blue (MB) degradation under the daylight. TiO-SiO mixture exhibits higher solar-light catalytic activity compared to individual colloids which could by explain by the presence of highly photocatalytic TiSi2. These results represent potential of SiO and TiO reducing interactions which are favorable for generation of photocatalytic materials for water remediation.

A novel ZnS/SiO2 double passivation layers for the CdS/CdSe quantum dots co-sensitized solar cells based on zinc titanium mixed metal oxides

The surface passivation strategy is one of the effective ways to improve the power conversion efficiency (PCE) of quantum dots-sensitized solar cells (QDSSCs). In this work, a novel ZnS/SiO2 coating serves as the passivation layers for the CdS/CdSe co-sensitized solar cells based on zinc titanium mixed metal oxides (MMOs) obtained from layered double hydroxides (LDHs) precursor. The incorporation of passivation layers effectively improved the performance of the corresponding CdS/CdSe quantum dots co-sensitized solar cells and the best PCE of 4.91% has been achieved, which represents an over 55% improvement than that of devices without passivation. The effects of ZnS/SiO2 double passivation layers were systematically investigated, especially by 2D time-resolved fluorescence imaging and electrochemical impedance spectroscopy technique. It was revealed that the existence of ZnS/SiO2 outer layers caused the suppression of charge recombination, higher electrons collection efficiency, and superior surface quality.

Simultaneous electroanalysis of dopamine, paracetamol and folic acid using TiO2-WO3 nanoparticle modified carbon paste electrode

In this study, mixed titanium oxide and tungsten trioxide nanoparticles (TiO2-WO3NPs) were prepared and characterized by different characterization techniques. The prepared materials TiO2-WO3NPs were used as modifiers in carbon paste electrode (TiO2-WO3NPs/MCPE) to study the electrochemical behaviour of dopamine (DA) in phosphate buffer solution (PBS) at pH 7.4 by using cyclic voltammetric (CV) technique. The TiO2-WO3NPs/MCPE shows enhanced electrocatalytic activity compared to bare CPE. As a result, the TiO2-WO3NPs/MCPE was used for further electrochemical studies. The effect of pH proposed that an equal number of electron and proton are involved in the electrochemical reaction of DA. The DA concentration determination was in the range 2 × 10−6 M to 18 × 10−6 M and the limit of detection (LOD) and limit of quantification were found to be 10.18 nM and 34.32 nM. From the scan rate study the oxidation of DA was found to be adsorption controlled and simultaneous detection of DA, PA and FA were well separated in CV and differential pulse voltammetric (DPV) technique. Moreover the stability and reproducibility of TiO2-WO3NPs/MCPE at DA was studied and furthermore successfully demonstrated for the detection of DA in blood serum and injection samples.

The photovoltaic performance of CdS/CdSe quantum dots co-sensitized solar cells based on zinc titanium mixed metal oxides

Abstract New photoanode based on zinc titanium mixed metal oxide (MMO) was successfully prepared using the layered double hydroxide precursor. The successive ionic layer adsorption and reaction method and chemical bath deposition method were used to fabricate CdS/CdSe co-sensitized quantum dot sensitized solar cells (QDSSCs). When the reaction cycle of CdS quantum dot is nine, the highest power conversion efficiency of 2.85% has achieved, with the lowest recombination rate and the biggest current density. This work demonstrated that 9 cycles of sensitization of CdS QD was the best for the CdS/CdSe QDs co-sensitized solar cells based on ZnTi MMO photoanode.

Encapsulation of nano-sized iron(III)–titanium(IV) mixed oxide for the removal of Co(II), Cd(II) and Ni(II) ions using continuous-flow column: multicomponent solution

ABSTRACT Encapsulation of nano-sized iron(III)–titanium(IV) mixed oxide was achieved using sodium alginate to produce encapsulated Fe–O–Ti beads for the removal of Co(II), Cd(II), and Ni(II) from multicomponent solution using fixed-bed column. The column performance was 57.6, 49.2, and 34.0% for Ni(II), Co(II), and Cd(II), respectively. The breakthrough curves were better described by Thomas model than Yoon-Nelson model. Regeneration of the ions-loaded adsorbent was performed at 0.1 mol/L HCl, at which the desorption percent was 88.8, 86.4, and 83.3% for Co(II), Ni(II), and Cd(II) respectively. Finally, the encapsulated Fe–O–Ti can be recommended for the removal of Co(II), Cd(II), and Ni(II) from multicomponent media.

Mixed Titanium Oxide Strategy for Enhanced Photocatalytic Hydrogen Evolution.

Titanium dioxide is a promising photocatalyst material for water splitting, but is limited by its low utilization of solar energy and rapid recombination of electron-hole pairs. Herein, a mixed titanium oxide strategy, utilizing TiO2/Ti2O3 heterostructures consisting of in situ grown TiO2 nanotubes with mixed anatase and rutile phases on bulk Ti2O3 materials, is demonstrated for efficient and recyclable hydrogen evolution from photocatalytic water splitting. Taking advantage of the formed heterostructures and the created porous structures, the photogenerated electrons from the conduction band of anatase TiO2 can be first delivered to rutile TiO2 and then transferred to Ti2O3. Meanwhile, the presence of Ti2O3 in TiO2/Ti2O3 heterostructures can substantially promote the charge mobility and suppress the recombination of photogenerated electron-hole pairs. Hence, with a tuned band gap structure that enables rapid electron-hole separation, increased charge carrier density, and enhanced light absorption, the TiO2/Ti2O3 heterostructures provide an enhanced photocatalytic hydrogen evolution rate as high as 1440 μmol g-1 h-1 under full-sunlight irradiation and without any other cocatalyst. This mixed titanium oxide strategy may open up new avenues for designing and constructing highly efficient TiO2-based photocatalytic materials for various applications.

Preparation and photovoltaic properties of dye-sensitized solar cells based on zinc titanium mixed metal oxides

A novelty method has been replenished for getting one kind of photoanode materials for dye-sensitized solar by an ingenious way. Using the ZnTi layered double hydroxide (LDH) as a precursor of photoanode materials, the ZnTi-LDH with different ratios were produced through urea method. Since the thermal treatment of LDH precursor at 500 ℃, the ZnTi mixed metal oxides (MMO) were easily obtained and then DSSC based on different ratios of ZnTi-MMO were fabricated with two kinds of dyes (C101 and Z907). The different ZnTi cationic ratios and diverse dyes make a big difference on the performance of DSSC. As the amount of Zn2+ increasing, the photocurrent and power conversion efficiency (PCE) of the cells first increase and then decrease. The optimal efficiency under C101 condition gets up to 1.57% at 9:1 cationic ratio of the ZnTi-LDH precursor. The C101 dye exhibits a more impressive performance than the Z907 where the DSSC is equipped with same MMO and other conditions.

The effect of CuS counter electrodes for the CdS/CdSe quantum dot co-sensitized solar cells based on zinc titanium mixed metal oxides

The highly catalytic copper sulfide (CuS) thin films were designed and combined with the FTO substrates by the chemical bath deposition method and were used as counter electrodes (CEs) for the CdS/CdSe quantum dot-sensitized solar cells (QDSSCs) based on zinc titanium mixed metal oxides (MMOs) deriving from the layered double hydroxide precursor for the first time. Formation of CuS films was confirmed by X-ray diffraction and X-ray photon spectroscopy. The surface morphology of CuS films was observed by scanning electron microscopy (SEM). Systemic electrochemical test was used to investigate the catalytic performance of CuS films and the photovoltaic performance of QDSSCs. When the number of deposition cycles (30 min per cycle) was two, the CuS CEs of excellent performance were obtained. The CuS CEs exhibited higher performance for QDSSCs based on ZnTi MMOs than the conventional platinum (Pt) CEs. The best power conversion efficiency of CdS/CdSe QDSSCs using optimal CuS CEs reached 3.95%, which is more than twice higher than that of Pt CEs.