Structure Of CeO2 Research Articles

La-Doped CeO2 Quantum Dots: Novel Dye Degrader, Antibacterial Activity, and In Silico Molecular Docking Analysis.

The current work demonstrates a novel synthesis of different concentrations of La-doped (2, 4, and 6 wt %) CeO2 quantum dots (QDs) using a hydrothermal approach. This research aimed to examine the dye degradation efficiency, antibacterial activity, and in silico molecular docking analysis of La-doped CeO2 QDs. The structure, elemental composition, optical properties, d-spacing, and morphological features of QDs were examined using various methods. XRD spectra exhibited the cubic structure of CeO2, and the crystallinity was suppressed upon La doping. TEM revealed the formation of cubic-shaped QDs of CeO2, and the incorporation of La decreased agglomeration. UV-vis absorption spectra showed a red shift upon La doping, assigned to a decrease in band gap energy. 6% La-doped CeO2 showed significant antibacterial activity against Escherichia coli at higher concentrations in comparison to ciprofloxacin. La-CeO2 was proposed as a putative inhibitor of β-lactamase E.coli and DNA gyrase E.coli relying on the outcomes of a molecular docking analysis that was in improved accord with in vitro bactericidal activity. Moreover, the prepared QDs exhibited a remarkable photocatalytic degradation of methylene blue in a basic medium.

Efficient adsorption and antimicrobial application of bio-synthesized porous CeO2 nanoparticles

The present research demonstrates the green synthesis of CeO2 nanoparticles (NPs) using the Acacia Concinna fruit extract by sol–gel route. The synthesized CeO2 NPs are applied for the adsorptive removal of Reactive Blue (RB) azo dye and antimicrobial activities. The CeO2 NPs are characterized using different techniques e.g. X-ray Diffraction Spectroscopy (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), UV–vis Spectroscopy, Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Dynamic Light Scattering (DLS), Raman Spectroscopy, etc. The structural investigations (XRD) reveal the single-phase cubic fluorite-type structure of CeO2 with 22.7 nm of crystallite size. The spectral analysis (FTIR) shows a strong vibration band below 849 cm−1 owing to Ce-O-Ce stretching vibrations. A porous network-like morphology of the CeO2 NPs is observed by SEM, where HR-TEM micrographs reveal that the nanoparticles are roughly spherical in nature. Raman spectroscopy confirms the vibrational mode of the cubic fluorite type structure of CeO2 NPs at 462 cm−1. The maximum loading capacity of CeO2 NPS is 188.67 mg/g. The antibacterial activity of the CeO2 NPs is evaluated against S. pneumoniae and E.coli, which shows 96.17 % and 96.89 % growth inhibition at 20 mg/l.

Transition metal and Pr co-doping induced oxygen vacancy in Pd/CeO2 catalyst boosts low-temperature CO oxidation

Cerium oxide-based materials have wide application prospects in catalytic oxidation reactions. Doping valence metals in CeO2 is an effective strategy to increase the content of oxygen vacancy of CeO2 and regulate the surface and interface structure of CeO2 supported metal catalysts. In this work, transition metal (M = Fe, Co and Mn) and Pr co-doped CeO2 nanorod were prepared by hydrothermal method and used to support Pd, which significantly improved the activity of CO catalytic oxidation. Under dry and wet condition, the T99 (temperature to achieve 99% conversion of CO) decreased from 190 °C and 165 °C for single-doped Pd/Pr-CeO2 catalyst (Pd content of 0.2 wt%) to 125 °C and 107 °C for co-doped Pd/FePr-CeO2 catalyst under reaction condition with GHSV (gas hourly space velocity) of 70, 000 mL gcat.-1h−1, respectively. Moreover, the Pd/FePr-CeO2 catalyst showed an excellent stability and kept its activity more than 2400 min. The systematic characterizations revealed that the outstanding CO catalytic performance is attributed to the co-doping of Pr and Fe, which increases the oxygen vacancy content on the catalyst surface, promotes the activation of lattice oxygen in the support, and strengthens the interaction and electron transport ability between Pd and the support. This work opens promising perspectives to enhance the activity of supported metal catalysts in oxidation reactions by co-doping of valence metals in oxide supports.

Structural, electronic and optical study of Zr:CeO2 thin films by computational and experimental approach

Transition metal oxide shows some exceptional optical and electronic properties explore in recent investigations. In this context, the current study presents first principal and experimental investigations of pure and Zr doped CeO2 thin films. The simulations were performed using density functional theory based Wien2k-code with PBE-GGA approximation. The uniform and well-distributed granular thin films were grown for experimental investigations. The simulations and experimental results show a good resemblance in outcomes. The density of states predicts the p-d hybridization between Ce and O atoms while band structure reduce with Zr incorporation in CeO2 structure. Crystallographic analysis reveals the presence of crystalline cubic phase with space-group 225-F-m3m in thin films. Experimentally observed bandgap follows the reducing trend with Zr incorporation as predicted by simulations data and found as 2.38 eV for pure CeO2 and 1.51 eV for 6.25% Zr doping content. Optical parameters were recorded as a function of photon energy which strongly influenced by Zr concentration. The sharp increase in optical absorption and real part of dielectric constant in Zr containing composition makes these materials more efficient and favorable for photovoltaic and optoelectronic applications.

Comparison of the different distribution functions in Gd-doped ceria system by molecular dynamics simulations

Cerium dioxide-based materials are among the most studied for applications in the energy and environmental fields and are also of interest in biology and medicine. The fluorite structure of CeO2 is locally distorted by the concomitant presence of doping cations, such as Gd3+ and oxygen vacancies. The cation-anion bond length distribution then becomes increasingly asymmetric with the doping ratio and temperature. In these cases, the MD simulation results indicate that the commonly used maximum of the pair correlation function g(r) first peak can no longer be adopted to estimate the mean bond length. To determine the true cation-anion bond length, the analysis of the radial distribution function R(r) first peak is necessary. Furthermore, the asymmetry of this peak must be accounted for when extracting the mean value of the distribution. The gap between the g(r) maximum and the R(r) mean position derived from the fit using a skewed Gaussian function clearly increases with the doping ratio and temperature, leading to different conclusions concerning bond length evolution. The present study also suggests that care must be taken when the bond length is deduced from the pair distribution functions G pdf(r) as is the case in total scattering experiments (x-ray and neutrons). Finally, relations between the cumulants of the effective distribution of distances as determined in extended x-ray absorption fine structure experiments and the cumulants describing the real distance distribution are proposed considering that both these distributions are modelled by a skewed Gaussian function.

Optimizing oxygen vacancies and electrochemical performance of CeO2-δ nanosheets through the combination of di- and tri-valent doping.

Ceramic fuel cells presently hold an important position in the future of sustainable energy. However, new concepts and designs are vital for each individual cell's component materials to improve the overall power output and stability. The limited ionic conductivity of the electrolyte component is one major challenge among these. In the present work, we developed nanosheets with a cubic fluoride structure of CeO2 and introduced the di- and tri-valent doping of La and Sr to study their impact on oxygen vacancies and its ionic transport, keeping in mind the fact that CeO2 is reduced when exposed to a reducing atmosphere. The attained La- and Sr-doped fluorite structures of CeO2 exhibited good ionic conductivity of >0.05 S cm-1 at low temperature, and their use in a fuel cell resulted in achieving a power output of >900 mW cm-2 while operating at 550 °C. Therefore, we have found that laterally combining di- and tri-valent doping could be textured to give a highly oxygen-deficient CeO2 structure with high ionic transport. Furthermore, various microscopic and spectroscopic analyses, such as HR-TEM, XPS, Raman, UV-visible, EIS, and density functional theory, were applied to investigate the change in structural properties and mechanism of the ionic transport of the synthesized La and Sr co-doped CeO2 electrolyte. This work provides some new insights for designing high-ionic-conductivity electrolytes from low-cost semiconductor oxides for energy storage and conversion devices.

Preparation of a CeO2 ball-core structure and its application in quantum dot sensitized solar cells.

A pomegranate-like nanosphere structure of CeO2 was prepared by a simple one-step hydrothermal method, and the novel CeO2 structure was printed on a TiO2 film to form a scattering layer, which constituted the composite structure of a photoanode in a thin film optoelectronic device. Then ZnCuInSe quantum dots, a ZnS passivation layer and a CuS counter electrode were prepared, and these parts were assembled into quantum dot-sensitized solar cells. By changing the thickness of the scattering layer film in the photoanode, the quantum dots were adsorbed on TiO2 more effectively. By using the special ball-core structure, light was scattered so that the photoanode used the light many times, which effectively increased the efficiency of photoelectron production. After electrochemical testing of the device, it was found that the photoconversion efficiencies of the TiO2 transparent layer and the CeO2 scattering layer composite photoanode were greater than that of a single TiO2 photoanode without a scattering layer. The results showed that when the thickness of the scattered layer was 10 ± 1 μm, the highest photoelectric conversion efficiency (PCE) was obtained, which was 20% higher than that seen with TiO2 alone.

Plasma-etched CeO2 nanorods with rich defect sites and acidity for dichloroethane oxidation

Adjusting the structure and surface profiles of CeO2 could significantly modify its catalytic performance for CVOCs.

Hydrothermal aging mechanism of K/CeO2 catalyst in soot catalytic combustion based on the Ostwald ripening mechanism

The thermogravimetric analysis (TGA) experiment of CeO2 and K/CeO2 catalysts prepared with the incipient wetness impregnation method was carried out for the soot catalytic combustion at different K loadings before and after hydrothermal aging. The structure, morphology, and catalytic activity of CeO2 and K/CeO2 catalysts were thoroughly investigated with the means of N2 adsorption/desorption, XRD, XPS, and H2-TPR. The density functional theory (DFT) operation was applied to explain the mechanism of the decrease in catalytic activity of CeO2 and K/CeO2 catalysts after hydrothermal aging. TGA showed that the Tmax of the hydrothermal aging K/CeO2 catalyst was 505 °C, which was higher than CeO2 at 473 °C. After hydrothermal aging, CeO2 catalysts were less agglomerated than K/CeO2, and the ratio of Ce3+/Ce4+ decreases, but the mobile oxygen OII/OI ratio in the lattice were increased compared to CeO2 catalysts. DFT calculations showed that K doping significantly increases the surface energy and decreases the oxygen vacancy formation energy of (1 1 1), (2 0 0), (2 2 0), and (3 1 1) crystal planes, leading to enhanced catalytic combustion performance of the K/CeO2 catalyst soot based on the Mars-Van Krevelen mechanism. Furthermore, K doping decreased the adsorption energy of H2O and the energy barrier of K atoms diffusing near the surface of K/CeO2 catalyst crystals from 5.92 eV to 2.46 eV, which resulted in the loss of the active center number because of migration and coalescence (sintering) caused by crystal plane instability based on the Ostwald ripening mechanism.

Enhanced dielectric constant and mechanical investigation of epoxidized natural rubber with TM-doped CeO2 nanocomposites

The dielectric constant and mechanical properties of epoxidized natural rubber (ENR) were improved by forming composites with CeO2 and various types of transition metal (TM) doped CeO2 nanoparticles (TM-doped CeO2 such as Fe-CeO2, Co-CeO2, Ni-CeO2, Cu-CeO2, Mn-CeO2 and Zn-CeO2). The CeO2 samples and TM-doped CeO2 nanoparticles were prepared using a co-precipitation method at room temperature and were calcined at 600 °C. The composites were prepared with 2 phr of CeO2 and TM-doped CeO2 nanoparticles referred to as CeO2 @ENR, Fe-CeO2 @ENR, Co-CeO2 @ENR, Ni-CeO2 @ENR, Cu-CeO2 @ENR, Mn-CeO2 @ENR and Zn-CeO2 @ENR. A carbon black (CB) and ENR composite was also prepared for comparison and referred to as CB@ENR. The morphology, phase and valence states of prepared samples were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), field emission scanning electron microscopy, X-ray photoelectron spectroscopy. The samples exhibited XRD peaks and TEM-selected area electron diffraction corresponding to a face centered cubic CeO2 structure, confirming a single phase. They showed average crystallite sizes in the range of 10.5 ± 0.3–15.0 ± 1.4 nm. All TM-doped CeO2 @ENR composites exhibited higher dielectric constants and lower dielectric losses at room temperature as a function of frequency than that of CB@ENR composites. A maximum value of ∼392.6 at 102 Hz for the Cu-CeO2 @ENR composite was shown. Additionally, this dielectric constant was about 3 and 4.7 times higher than those of CeO2 @ENR and CB@ENR, respectively. Also, the breakdown strength of the Cu-CeO2 @ENR nanocomposite was increased compared to CB@ENR. Furthermore, TM-doped CeO2 nanocomposites display increased torque, higher 100% & 300% moduli and greater tensile strength caused by nano-filler affects. As a result, this research may open up new avenues for the development of insulating elastomers.

Structure and thermal behavior of CeO2 and TiO2 nanopowders doped with noble metals

Structure and thermal behavior of CeO2 and TiO2 nanopowders doped with noble metals

Experimental study of the phase relationships in the CeO2–Gd2O3 system at 1200°C to 1600°C in air

Phase relationships in the CeO2–Gd2O3 slag system were experimentally investigated based on the equilibrated alloy technique at 1200, 1400 and 1600 °C. The phase analysis in the stove-cooled samples was carried out by X-ray diffraction, scanning electron microscopy and electron probe microanalysis. The phase diagram was constructed in the whole compositional range based on experimental results. Three single phase regions, namely monoclinic (B) modification of Gd2O3, cubic (C) of Gd2O3, and fluorite (F) structure of CeO2, were observed. The solubility of Gd2O3 in F reaches up to 60.4 mol.% at 1600 °C, while СeO2 hardly dissolves in the B phase at 1200–1600 °C. No intermediate compounds were found under the conditions of our study. The lattice parameters of unit cells and the boundaries of the homogeneity field for solid solutions were carefully determined.

Effect of Metal Dopant on the Performance of Ni@CeMeO2 Embedded Catalysts (Me = Gd, Sm and Zr) for Dry Reforming of Methane

Biogas upgrading by a catalytic process has been studied in order to obtain syngas using renewable source of methane. This work evaluates the influence of metal dopant (Gd, Sm, and Zr) on the CeO2 structure for the dry reforming of methane over Ni nanoparticle embedded catalysts. The doping with Zr improved the thermal stability of the catalyst, leading to the formation of small Ni nanoparticles, while Ni metal sintering was observed for Ni@CeO2, Ni@CeGdO2, and Ni@SmO2, according to in situ XRD under reduction conditions. The ceria reducibility was affected by the dopant nature, for which the addition of Zr caused distortions in the ceria lattice, promoting the diffusion of oxygen bulk to surface. The doping with Gd and Sm created oxygen vacancies by charge compensation, and the saturation of oxygen vacancies in the fresh samples decreased the degree of Ce reduction, according to TPR results. The larger Ni particles and poor redox behavior for Ni@CeGdO2 and Ni@CeSmO2 were responsible for the high carbon formation on these catalysts during the DRM reaction. The Ni@CeZrO2 catalyst did not present coke formation because of smaller Ni crystallite size and higher ceria reducibility. Therefore, the control of Ni particle size and the high oxygen mobility in the Ni@CeZrO2 catalyst inhibits carbon deposition and enhances the mechanism of carbon removal, promoting the catalyst stability.

Co-Based Catalysts Supported on Ceria with Different Shape Structures for Hydrodeoxygenation of Guaiacol

CeO2 with three different morphologies of nanorods (CeO2-r), particles (CeO2-p), and cubes (CeO2-c) was prepared, and the guaiacol hydrodeoxygenation over their corresponding Co-based catalysts was performed at 160–220 °C, 2 MPa, a H2 flow rate of 80 mL/min, and a weight hourly space velocity of 0.7 h–1. Compared with Co/CeO2-p and Co/CeO2-c, Co/CeO2-r has smaller Co particle sizes, a higher Brunauer–Emmett–Teller surface area, and larger amount of Co active centers, oxygen vacancies, and weak acid sites. These better physicochemical properties for Co/CeO2-r provide more Co active sites for guaiacol hydrodeoxygenation, favor the adsorption and activation of guaiacol, and contribute to the cleavage of C–O. Therefore, Co/CeO2-r presents a maximum guaiacol conversion of 97.1% and the highest yield of cyclohexanol of 91.7% among these catalysts. The result shows that the shape structure of CeO2 has an important influence on the guaiacol hydrodeoxygenation performance over its corresponding catalysts.

Dual-mode nanoprobes for reactive oxygen species scavenging and treatment of acute lung injury

Oxidative stress plays an important role in acute and chronic inflammatory diseases. However, the clinical treatment options for oxidative stress-related diseases are limited. Nanozyme with excellent reactive oxygen species (ROS) catalytic capacity are promising for preventing ROS-related inflammation. Herein, we designed CeO2:Yb7Tm0.5 with a butterfly-like structure of upconversion nanoparticles (UCNPs) with enzyme-mimicking ability. The CeO2:Yb7Tm0.5 UCNPs have catalase and glutathione peroxidase-mimicking enzyme properties, which can treat acute lung injury (ALI). The CeO2:Yb7Tm0.5 UCNPs turn blue, green, white, and red under upconversion luminescence with increasing temperature from 298 K to 358 K. Here, the changing of color are examined over the temperature range of in 298 K-373 K in 10 K increments. Maximum absolute and relative sensitivities (Sa and Sr) of 2.3 % K−1 and 2.7 % K−1 are obtained at 298 K and 373 K, respectively. The butterfly-like structure of CeO2:Yb/Tm is promising for biological application, such as accurate cell temperature detection, bio-catalysis diagnostics and ALI treatment.

CeO2-C nanorods obtained by high-temperature carbonization of Ce-MOF as separator coating for Li-S battery

Lithium-sulfur batteries (LSBs) are of great interest to researchers due to their high theoretical specific capacity and high energy density. Unfortunately, because of sulfur's weak conductivity and the shuttle effect of polysulfides, the application prospects of LSBs are facing great challenges. To suppress the shuttle effect of polysulfides, nanorod-like CeO2 and CeO2-C using Ce-MOF as the precursor was successfully prepared and applied to the separator of LSBs. Coating CeO2 and CeO2-C obtained by calcination in different atmospheres on PE separators can effectively enhance the electrochemical properties of LSBs due to the excellent chemisorption and catalytic effect of CeO2 on lithium polysulfides. In particular, CeO2-C which is obtained by calcination of Ce-MOF in N2 atmosphere has abundant micro and meso porous structures, which can quickly adsorb polysulfide in the electrolyte and accelerate the redox kinetics at the same time. Moreover, the nano-rod structure of CeO2 and CeO2-C also improves the conductivity of the separator. After a series of electrochemical tests, it was discovered that the discharge capacity of the CeO2-C coated separator battery on the first cycle was 1240 mA h g−1 when the cathode sulfur loading was approximately 2.5 mg cm−2, and that the discharge capacity remained 520 mA h g−1after 500 loops at 0.5 C. Even when the sulfur loading reaches 5.5 mg cm−2, it also has a good cyclic stability, demonstrating its application potential.

The effect of stress on electronic structure and optical properties of CeO2

The effect of stress on the electronic structure and optical properties of CeO2 is studied using the ultrasoft pseudopotential plane wave method based on density functional theory. The results show that the band gap decreases quasi-linearly with the negative stress increasing and increases quasi-linearly with the increase of positive stress. Combining with the density of states (DOS) analysis, the main reason for the change of the band gap is Ce 4f electrons are significantly affected by the stress. When the stress changes from −25 to 30 GPa, the DOS of Ce 4f is far away from the Fermi level and gradually decreases. The influence of stress on optical properties mainly shows two obvious features. The first feature is that the optical properties are gradually appeared as the stress changes from −25 to 30 GPa and the optical edges are moved to high energy direction, in the energy range of 0–3 eV. Another feature is that there is an obvious peak value under the stress of −25–0 GPa, but does not significantly change under the stress of 0–30 GPa, in the energy range of 3–6 eV. The results show that the negative stress enhances the electronic transition, which is beneficial to improve the utilization of light.

Liquid phase sintering of alumina–silica co-doped cerium dioxide CeO2 ceramics

Pure and low α-Al2O3/SiO2 co-doped ceria specimens were prepared by conventional ceramic processing using powder metallurgy. This study investigated the effect of co-doping on the microstructural and structural properties of cerium dioxide was investigated by means of optical microscopy, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The co-addition of alumina and silica promoted liquid phase sintering and significantly contributed to grain growth, even in the small concentrations of the present study (1 and 2 wt%). A glassy look phase precipitated at the grain boundaries, a characteristic feature of liquid phase sintering. The addition of dopants to the formulation greatly enhanced the grain growth process without disturbing the CeO2 structure.

Crystalline structure, oxygen defects and textural properties of the CeO2/SBA-15 nanomaterials

In this study, a series of CeO2/SBA-15 nanomaterials were synthesized by varying the CeO2 content. These materials were characterized by different techniques to determine their textural, surface chemical and crystalline properties. Crystallite size and oxygen defects were determined by Microanalysis Using X-Ray Diffraction (MAUD) software based on the Rietveld refinement method. The results showed that the crystallite size slightly increased from 5.6 to 8.4 nm and the surface area decreased from 620 to 370 m2/g as CeO2 content increased from 5 to 10, 15 to 20wt%. The oxygen occupancy that was associated with oxygen defects was found in the crystalline structure of CeO2. The defect concentration was between 6.18 and 14.42%, depending on the ceria content and dispersion. This study confirmed that the CeO2/SBA-15 nanomaterials have larger surface area, highly dispersed CeO2 nanoparticles, and a big number of oxygen defects in the crystalline structure, which can be used in different catalytic reactions.

Composition dependence of ferroelectric properties in (111)-oriented epitaxial HfO2-CeO2 solid solution films

The composition dependence of ferroelectric properties was investigated for (111)-oriented epitaxial HfO2-CeO2 solid solution films. Twenty nanometer thick films with different compositions were prepared on (111)ITO//(111)YSZ substrates at room temperature by pulsed laser deposition and subsequent heat treatment at 1000 °C under atmospheric N2 or O2 gas flow. All the films had fluorite structures, and their crystal symmetries changed from monoclinic through orthorhombic to tetragonal/cubic phases as x increased for the (Hf1−x Ce x )O2 (x = 0.12–0.25) films. The orthorhombic phase was confirmed by X-ray diffraction analysis for films with x = 0.15 and 0.17. On the other hand, ferroelectric properties were observed in films with x = 0.15–0.20, suggesting that a field-induced phase transition takes place for films with x = 0.20. The film composition showing ferroelectricity was the widest range of doping concentration for reported epitaxial HfO2-based films. Their remanent polarization (P r) and coercive field (E c) were almost identical, at 17–19 μC cm−2 and 2.0–3.0 MV cm−1. This wide ferroelectric composition range with relatively similar ferroelectricity is due to the solid solution of the same fluorite structure of HfO2 and CeO2 with monoclinic and cubic symmetries, that are respectively lower and higher crystal symmetries of the ferroelectric orthorhombic phase.