Titanium Cerium Research Articles

Dual-edged sword effects of sulfation/hydration on Ce-doped TiO2(001) single-atom catalyst for NH3-SCR reaction: A first-principles study

SO2/H2O-resistance remains challenges for selective catalytic reduction with NH3 (NH3-SCR). The detailed promotion and/or inhibition effects of sulfation/hydration on cerium-titanium (CT) catalysts for NH3-SCR are still controversial. Herein, a series of adsorption characteristics, bonding strengths, electronic effects, and reaction pathways were performed by first-principles density functional theory calculations to explore the structure-performance/resistance of CT catalysts and unravel the effects of sulfation/hydration for NH3-SCR. We constructed six CT catalyst structures based on three TiO2 facets [(001)/(101)/(100)] and two surface configurations [single-atom (SA)/interface (IF)]. CT(001)-SA could protect the active Ce site from sulfation/hydration with TiO2(001) as SO2/H2O-trapping site, which was the optimal SO2/H2O-resistant structure among six CT catalyst structures. An electron-deficient state of CT(001)-SA was caused by sulfation/hydration through electron capture behavior. From the perspective of reactants adsorption, this electron-deficient state not only promoted the NH3/NO adsorption but also suppressed the secondary sulfation/hydration. As for NH3-SCR pathways, hydration promoted NH3 dissociation, N-N coupling, and N-O breaking, but inhibited the H1 transfer (rate-determining step). Sulfation impaired the redox ability of Ce site, promoted H1 transfer and N-O breaking, but inhibited the NH3 dissociation, N-N coupling, and H2 transfer (rate-determining step). Hence, sulfation/hydration exhibited “dual-edged sword” effects for NH3-SCR on CT(001)-SA via electronic effects.

Low-Index Facet Polyhedron-Shaped Binary Cerium Titanium Oxide for High-Voltage Aqueous Zinc-Vanadium Redox Flow Batteries.

Aqueous zinc-vanadium hybrid redox flow battery systems are an efficient strategy to address the problems of low voltage and high cost of conventional all-vanadium redox flow batteries. However, the low electrochemical activity of carbon-based electrodes toward a vanadium redox reaction limits the performance of redox flow batteries. In this study, polyhedral binary cerium titanium oxide (Ce2/3TiO3, CTO) is synthesized using molten salt synthesis. CTO is fabricated by adjusting the temperature and composition. Notably, the prepared CTO obtained at 1000 °C shows the highest catalytic activity for a VO2+/VO2+ redox reaction. Further, CTO is prepared as a composite electrocatalyst and applied to a high-voltage aqueous zinc-vanadium redox flow battery. The cell adopts an alkali zinc electrolyte containing a Zn/[Zn(OH)4]2- redox pair and exhibits a high operating voltage of 2.26 V. Remarkably, a zinc-vanadium redox flow battery using the composite electrocatalyst exhibits a high energy density of 42.68 Wh L-1 at 20 mA cm-2 and an initial voltage efficiency of 90.3%. The excellent cell performance is attributed to structural defects caused by A-site deficiency in the perovskite oxide structure as well as oxygen vacancies resulting from the low valence state of the metal ion, which enhance the catalytic activity of the vanadium ions.

Promotion Effect of the Keggin Structure on the Sulfur and Water Resistance of Pt/CeTi Catalysts for CO Oxidation

Developing a catalyst with high SO2 and H2O resistance to achieve high-performance CO oxidation for specific industrial applications is highly desirable. Here, three catalysts were prepared using cerium titanium composite oxide (CeTi), molybdophosphate with Keggin structure-modified CeTi (Keg-CeTi), and molybdophosphate without Keggin structure-modified CeTi (MoP-CeTi) as supports, and their sulfur and water resistance in CO oxidation were tested. The characterization of XRD, BET, SO2/H2O-DRIFTS, XPS, TEM, SEM, NH3/SO2-TPD, H2-TPR, and ICP techniques revealed that the high SO2 and H2O resistance of Pt/Keg-CeTi in CO oxidation was related to its stronger surface acidity, better reduction of surface cerium and molybdenum species, and lower SO2 adsorption and transformation compared to Pt/CeTi and Pt/MoP-CeTi.

Mesoporous titania–ceria mixed oxide (MTCMO): a highly efficient and reusable heterogeneous nanocatalyst for one-pot synthesis of β-phosphonomalonates via a cascade Knoevenagel–phospha-Michael addition reaction

Mesoporous titania–ceria mixed oxide (MTCMO) was synthesised in a sol–gel method using cerium chloride and titanium isopropoxide (TTIP) as CeO2 as well as TiO2 precursors and sodium dodecyl sulphate (SDS) as a structure-directing agent and its application was evaluated in the synthesis of aromatic β-phosphonomalonate derivatives via cascade Knoevenagel–phospha-Michael addition reaction. The catalyst characterised by various techniques like FT-IR spectroscopy, XRD, SEM, EDS, TEM and N2 adsorption-desorption. Partial substitution of Ti4+ cations with Ce4+ improved the BET surface area because TiO2 crystallites were suppressed to be grown. Furthermore, as a consequence of charge imbalance in the obtained Ti-O-Ce solid solution, some oxygen vacancies have generated that act as Lewis base sites while cations (Ti and Ce) around the oxygen vacancies act as Lewis acid sites. Reusability up to eight consecutive runs without significant decrease in reactivity, Mild reaction conditions, environmentally benign and compatibility with various functional groups are some of the advantages of this work.

Efficient removal of bisphenol A from wastewaters: Catalytic wet air oxidation with Pt catalysts supported on Ce and Ce–Ti mixed oxides

Catalytic wet air oxidation (CWAO) of an aqueous solution of bisphenol A (BPA) was investigated at 160 ℃ and 2.0 MPa of air in a batch reactor. Activity of supported platinum catalysts (2.5 wt%), prepared by wet impregnation, was compared with pure cerium and cerium–titanium oxide catalysts. Supported platinum catalysts showed higher activities in the removal of BPA than pure CeO2, Ce0.8Ti0.2O2 and Ce0.2Ti0.8O2. The oxidation reaction was followed the pseudo-first order rate law and the highest BPA removal, 97% and 95%, was achieved with Pt/CeO2 and Pt/Ce0.8Ti0.2O2 catalysts respectively. The CWAO of BPA aqueous solution was not a surface area specific reaction but the more important factor affecting the activity of studied catalysts was the amount of chemisorbed oxygen of these samples.

Structural, optical and photocatalytic activity of cerium titanium ferrite

Perovskite phase Cerium Titanium Ferrites (CeTi1-xFexO3-δ) are prepared via sol-gel route, by varying mole ratios (X=0, 0.5 & 1.0) and the synthesized nanocatalysts used for the degradation of Methylene Blue organic pollutant. The as synthesized photo catalysts (CTFO-1, CTFO-2 and CTFO-3) were characterized using UV–vis, FT-IR, TG-DTA, PXRD, SEM and VSM techniques to study their optical, structural, thermal and magnetic properties. The photocatalytic activity on methylene blue dye using the synthesized nanocatalysts was analyzed and the experimental result was recorded using UV–vis spectrophotometer. The percentage reduction of methylene blue dye was estimated and found to be 99% on irradiation under UV lamp and 2.70% in the absence of UV lamp irradiation. The recyclability of the synthesized catalyst for four successive cycles indicates that the catalyst can be estranged and efficiently reused. The performance of CeTi0.5Fe0.5O3-δ nano photocatalyst was observed to be better than CeTiO3-δ and CeFeO3-δ. The photo-catalytic property of the prepared nanomaterial makes it suitable in amputation of dye effluents from the fabric industries.

Effect of fluoride doping for catalytic ozonation of low-temperature denitrification over cerium–titanium catalysts

Nanostructure cerium–titanium catalysts including fluoride (F−) doped ones were prepared by impregnation (Ce/TiO2 and Ce/F–TiO2) and co-precipitation (CeTi and CeTiF) method, and tested as ozonation catalysts for low-temperature NOX removal ranging from 40 to 180 °C. Interestingly, the doping of F− promotes the NOX removal for CeTi whereas inhibits the removal for Ce/TiO2. The NOX removal presents linear relationship with the concentration of hydroxyl radicals (OH). The surface –OH linked to Ce atoms as well as the H2O adsorption over Ce atoms play the important role in the generation of ·OH radicals. The doping of F− into CeTi improves the activation of Ce–OH linkage bonds and the adsorption of H2O over Ce atoms, thus increasing the concentration of OH radicals and catalytic activities. Although the doping of F− into Ce/TiO2 enhances the density of surface –OH, the ones linked to Ce atoms remain constant and the H2O adsorption over Ce atoms are declined, finally declining the catalytic activities.

Promotional effect of microwave hydrothermal treatment on the low-temperature NH3-SCR activity over iron-based catalyst

Microwave hydrothermal was introduced into the preparation of iron–cerium–titanium mixed oxide catalyst for NH3-SCR of NOx, and the catalysts after microwave hydrothermal treatment or not are characterized by X-ray diffraction (XRD), Infrared spectrum (IR), Transmission Electron Microscope (TEM), nitrogen adsorption–desorption and temperature programmed desorption (NH3/NO-TPD). Microwave hydrothermal treatment enhanced the low-temperature NH3-SCR activity of iron–cerium–titanium mixed oxide catalyst, and made its NH3-SCR reactive temperature window shift to the low-temperature region. Microwave hydrothermal treatment accelerated the crystallite rate of the precursors for iron–cerium–titanium mixed oxide catalysts, adjusted the microscopic pore structure of catalyst, and enlarged the pore diameter and the pore volume of catalyst. Microwave hydrothermal treatment increases Fe and Ce dispersion on the surface of catalyst, and the molar ratio of Ce3+/Ce4+ on the surface of mixed oxide catalyst could also be enhanced after microwave hydrothermal treatment, and improved the relative concentration of Ce3+, thereby enhanced the oxidation and reduction properties of catalyst. At the same time, microwave hydrothermal treatment enhanced the low-temperature adsorption intensity of NH3 over catalyst, thereby enhanced the low-temperature SCR activity of iron–cerium–titanium mixed oxide catalyst.

Improvement in thermal stability and catalytic activity of titanium containing mordenite by cerium using hydrothermal methods for hydroxylation of benzene into phenol

Cerium–titanium–mordenite (Ce–Ti/Mor) were synthesized using ortho-phenylenediamine (OPDA) as a templating agent, and varying amounts of cerium (0.5–4.0 mol%) have been successfully prepared by direct hydrothermal synthesis. These micropore materials were compared with pure mordenite synthesized at the same conditions. The influence of Ce/Ti–Mor composite on the phase, crystal structure and morphology has been investigated by X-ray diffraction (XRD), scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The probable assignments of the thermal degradation products of OPDA in Ce–Ti/Mor samples were studied by complementary thermogravimetric analysis and differential scanning calorimetry. XRD appeared of α-quartz (Si3O6) phase in Ti–Mor disappeared by the addition of Ce and reformation of pure mordenite structure. The increase in unit cell parameters observed with replacement Al by Ti is indicative of incorporation of Ti into the framework structure of microporous material mordenite, while a decrease in unit cell by replacement of Ti by Ce attributed to the presence of Ce–O–Ti bond on the surface of mordenite. The hydroxylation of benzene to phenol has been extensively investigated using hydrogen peroxide as an oxidant. All the Ce-supported catalysts exhibited high catalytic activity in the oxidation of benzene.

Derivation of the optical constants of spin coated CeO 2–TiO 2–ZrO 2 thin films prepared by sol–gel route

Ternary thin films of cerium titanium zirconium mixed oxide were prepared by the sol–gel process and deposited by a spin coating technique at different spin speeds (1000–4000 rpm). Ceric ammonium nitrate, Ce(NO 3) 6(NH 4) 2, titanium butoxide, Ti[O(CH 2) 3CH 3] 4, and zirconium propoxide, Zr(OCH 2CH 2CH 3) 4, were used as starting materials. Differential calorimetric analysis (DSC) and thermogravimetric analysis (TGA) were carried out on the CeO 2–TiO 2–ZrO 2 gel to study the decomposition and phase transition of the gel. For molecular, structural, elemental, and morphological characterization of the films, Fourier Transform Infrared (FTIR) spectral analysis, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), cross-sectional scanning electron microscopy (SEM), and atomic force microscopy (AFM) were carried out. All the ternary oxide thin films were amorphous. The optical constants (refractive index, extinction coefficient, band gap) and thickness of the films were determined in the 350–1000 nm wavelength range by using an nkd spectrophotometer. The refractive index, extinction coefficient, and thickness of the films were changed by varying the spin speed. The oscillator and dispersion energies were obtained using the Wemple–DiDomenico dispersion relationship. The optical band gap is independent of the spin speed and has a value of about E g ≈2.82±0.04 eV for indirect transition.

The Study of Method Preparing Golden Yellow Melted Glass and its Optical Performance

This paper presents the method of preparing a new golden yellow glass with relatively strong absorption of ultraviolet light. This golden yellow glass is to be produced from the glass raw material, Na2O-CaO-SiO2, as fundamental material with addition of cerium(IV) Oxide (CeO2) and titanium(IV) Oxide (TiO2) in combination as colorants.The analysis of spectrum transmittance and chroma Index have been carried out on the plates of this golden yellow glass by light dispersion equipment CARY500. Results indicate that the optical performance and chorma index of this new Golden Yellow melted Glass are largely depended on the factors such as concentration of colorants , oxidizability – reducibility of mixed batch and addition of fluorite.

A Review of Selected Engineered Nanoparticles in the Atmosphere: Sources, Transformations, and Techniques for Sampling and Analysis

A state-of-the-science review was undertaken to identify and assess sampling and analysis methods to detect and quantify selected nanomaterials (NMs) in the ambient atmosphere. The review is restricted to five types of NMs of interest to the Office of Research and Development Nanomaterial Research Strategy (U.S. Environmental Protection Agency): cerium oxide, titanium dioxide, carbon nanostructures (carbon nanotubes and fullerenes), zero-valent iron, and silver nanoparticles. One purpose was determining the extent to which present-day ultrafine sampling and analysis methods may be sufficient for identifying and possibly quantifying engineered NMs (ENMs) in ambient air. Conventional sampling methods for ultrafines appear to require modifications. For cerium and titanium, background levels from natural sources make measurement of ENMs difficult to quantify. In cases where field studies have been performed, identification from bulk analysis samples have been made. Further development of methods is needed to identify these NMs, especially in specific size fractions of ambient aerosols.

Release studies of corrosion inhibitors from cerium titanium oxide nanocontainers

Cerium titanium oxide nanocontainers were synthesized through a two-step process and then loaded with corrosion inhibitors 2-mercaptobenzothiazole (2-MB) and 8-hydroxyquinoline (8-HQ). First, polystyrene nanospheres (PS) were produced using polymerization in suspension. Second, the PS spheres were coated via the sol–gel method to form a cerium titanium oxide layer. Finally, the nanocontainers were made by calcination of the coated PS nanospheres. The size of the containers was 180 ± 10 nm as determined by Scanning Electron Microscopy (SEM). X-Ray Diffraction Analysis (XRD) showed that the nanocontainers consist of anatase and cerianite crystalline phases. The presence and loading of the inhibitors in the nanocontainers was confirmed with Fourier Transform Infrared Spectroscopy (FT–IR) and Thermo Gravimetric Analysis (TGA), respectively. TGA revealed the amount of 10.43 and 4.61% w/w for 2-MB and 8-HQ in the nanocontainers, respectively. Furthermore, the release kinetics of the inhibitors from the nanocontainers was studied in corrosive environment using electrochemical impedance spectroscopy (EIS) in the presence of aluminum alloys 2024-T3 (AA2024-T3).

Total oxidation of volatile organic compounds on Au/Ce–Ti–O and Au/Ce–Ti–Zr–O mesoporous catalysts

Cerium–titanium mixed oxides and mesoporous cerium-modified titanium and cerium-modified titanium–zirconium mixed oxides were synthesized in order to obtain active support for gold volatile organic compound (VOC) oxidation catalysts. Ce–Ti mixed oxides were synthesized by sol–gel method. Mesoporous TiO2 and Ti–Zr mixed oxides were prepared through the surfactant templating technique. Gold was loaded on supports by deposition-precipitation method. The catalysts were characterized by thermal analysis, XRD, N2 analysis, TPR, DR/UV–vis and IR. The results evidenced the beneficial role of ceria modifying additive in decreasing the degree of crystallinity of mesoporous support and its particle size. A high degree of synergistic interaction between ceria and mesoporous oxide was observed. H2-TPR revealed that the reducibility of the catalysts is greatly enhanced in the presence of gold. Considering the light off temperature, the activity of Au/mesoporous cerium-modified titanium oxide is particularly interesting for VOC oxidation comparatively to the same catalysts with a classical support. The gold particles would be more dispersed and stable. However, the sample Au/mesoporous cerium-modified titanium–zirconium mixed oxide is less interesting for VOC oxidation, particularly for toluene oxidation whose activity depends essentially on the adsorption of toluene molecule.

Differential Scanning Calorimetry Investigation on Vinyl Ester Resin Curing Process for Polymer Nanocomposite Fabrication

Two different ceramic (cerium oxide and titanium oxide) nanoparticles were introduced into vinyl ester resin for nanocomposite fabrication. The curing process of the vinyl ester resin was investigated by a differential scanning calorimetery (DSC). The incorporation of nanoparticles in the resin affects the curing process due to the physicochemical interaction between the nanoparticles and the polymer matrix. The particle loading has a significant effect on the initial and peak curing temperatures, reaction heat and curing extent. The fully cured vinyl ester resin nanocomposites reinforced with cerium oxide nanoparticles were fabricated after a 24-hour room temperature curing and a one-hour postcuring at 85 degrees C. Particle functionalization favors the composite fabrication with a higher curing extent after room-temperature curing as compared to the as-received nanoparticle filled vinyl ester resin nanocomposites. The nanofiller materials were observed to significantly affect the curing process. In comparison to cerium oxide nanoparticles, titanium oxide nanoparticles prohibit the curing process with a much higher initiating curing temperatures. The fully cured nanocomposites reinforced with titanium oxide nanoparticles were fabricated by one-hour postcuring at 85 degrees C.

Formation of coloring complexes in glass colored with cerium and titanium oxides

The valence state of cerium and titanium ions in barium-strontium aluminosilicate glass with a different ratio of cerium and titanium oxides was investigated and the possible composition of the cerium-titanium complexes formed in silicate glass was analyzed. It was found that an active separate reaction between cerium and titanium oxides with the appearance of complex color centers takes place in synthesis of the glass. It is hypothesized that color centers primarily form between tetravalent cerium and tetravalent titanium in glass-forming melts.

Microstructural characteristics and photoluminescence performance of nanograined thermally treated CeO2-TiO2 xerogels

Nanostructured thermally treated xerogels have been synthesized using a sol-gel process involving cerium (Ce) chloride heptahydrate and titanium (Ti) propoxide mixed in different Ce:Ti molar ratios. Structural features of the xerogels have been correlated with their photoluminescence (PL) response. The crystallite sizes in the samples lie in the nanorange. The x-ray diffraction and transmission electron microscopy results have confirmed the coexistence of CeO2 and TiO2 nanocrystallites in these xerogels. In general, a decrease in the CeO2 crystallite size and an increase in the TiO2 crystallite size are observed in the xerogels as a function of Ti content. Scanning electron microscopy results have evidenced the evolution of ordered structure in the xerogels as a function of TiO2 content. Although both of the phases (CeO2 and TiO2) have exhibited PL in ultraviolet and visible regions, the major luminescence contribution has been made by the CeO2 phase. The largest sized CeO2 crystallites in 1:1 thermally treated xerogel have led to its highest PL response. PL emission in the xerogels is assigned to their nanocrystalline nature and oxygen vacancy-related defects.

Variations in the structural, optical and electrochemical properties of CeO2–TiO2 films as a function of TiO2 content

Abstract Alcohol based sols of cerium chloride (CeCl 3 ·7H 2 O) and titanium propoxide (Ti(OPr) 4 ) in ethanol mixed in different mole ratios have yielded mixed oxide films on densification at 500 °C. The reversibility of the intercalation/deintercalation reactions has shown electrochemical stability of the films. Addition of TiO 2 in an equivalent mole ratio manifests in producing highly transparent films with appreciable ion storage capacity. The electrochemical studies have revealed the significant role of TiO 2 in controlling the ion storage capacity of the films, as it tends to induce the disorder. In addition, the films prepared from an aged sol are observed to exhibit a much higher ion storage capacity than the films deposited using the as-prepared sol. The X-ray photoelectron spectroscopic studies have provided information on the variation of Ce 4+ /Ce 3+ ratio as a function of increased TiO 2 content in the films. This study has led to a better understanding of the increased ion storage capacity with the increased TiO 2 proportion. The transmission electron microscopic study has demonstrated the presence of CeO 2 nanograins even in films, which are amorphous to X-rays. Elucidation of the structural, optical and electrochemical features of the films has yielded information on aspects relevant to their usage in transmissive electrochromic devices. The films have been found to exhibit properties that can find application as counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion, high enough for practical uses. Also, the fastest coloration–bleaching kinetics for the primary electrochromic electrode (WO 3 ) working in combination with Ce/Ti (1:1) electrode stimulates the use of latter in electrochromic windows (ECWs).

New sunscreen materials based on amorphous cerium and titanium phosphate

Cerium–titanium pyrophosphates Ce 1− x Ti x P 2O 7 (with x = 0, 0.50, and 1.0), which are novel phosphate materials developed as UV-shielding agents for use in cosmetics, were characterized by X-ray diffraction, X-ray fluorescent analysis, UV–vis reflectance, and Raman spectroscopy. Since the optical reflectance shifted to lower wavelengths by the crystallization of the phosphates and the stabilization of the amorphous state of the cerium–titanium pyrophosphates was carried out by doping niobium (Nb). Raman spectroscopic study of the phosphate showed that P O P bending and stretching modes decreased with the loading of Nb, accompanying with the formation of Nb O stretching mode. Therefore, the increase in the amount of the non-bridging oxygen in the amorphous phosphate should be the reason for the inhibition of the crystallization. This stabilization is a significant improvement, which enables to apply these amorphous phosphates not only to cosmetics and paints, but also plastics and films.

Investigation of Hydrothermal Routes to Mixed‐Metal Cerium Titanium Oxides and Metal Oxidation State Assignment Using XANES.

AbstractFor Abstract see ChemInform Abstract in Full Text.