Abstract: Transition metal (cerium and cobalt) doped γ-MnO2 (M-γ-MnO2, where M represents Ce, Co) catalysts were successfully synthesized and characterized. Cerium-doped γ-MnO2 materials showed ozone (O3) conversion of 96% for 40 ppm of O3 under relative humidity (RH) of 65% and space velocity of 840 L g–1 h–1 after 6 h at room temperature, which is far superior to the performance of the Co-γ-MnO2 (55%) and γ-MnO2 (38%) catalysts. Under space velocity of 840 L g–1 h–1, the conversion of ozone over the Ce-γ-MnO2 catalyst under RH = 65% and dry conditions within 96 h was 60% and 100%, respectively, indicating that it is a promising material for ozone decomposition. XRD and HRTEM data suggested that Ce-γ-MnO2 formed mixed crystals consisting of α-MnO2 and γ-MnO2 with specific surface area increased from 74 m2/g to 120 m2/g compared to undoped γ-MnO2, thus more surface defects were introduced. H2-TPR, O2-TPD, XPS, Raman, and EXAFS confirmed that Ce-γ-MnO2 exhibited more surface oxygen vacancies and surface defects, whi...

Abstract: Cerium oxide nanoparticles are known to catalyze the decomposition of reactive oxygen species such as superoxide radical and hydrogen peroxide. Herein, we examine the superoxide dismutase (SOD) and catalase (CAT) mimetic catalytic activities of nanoceria and demonstrate the existence of generic behaviors. For particles of size 4.5, 7.8, 23 and 28 nm, the SOD and CAT catalytic activities exhibit the characteristic shape of a Langmuir isotherm as a function of cerium concentration. Results show that the catalytic effects are enhanced for smaller particles and for the particles with the largest Ce3+ fraction. The SOD-like activity obtained from the different samples is found to superimpose on a single master curve using the Ce3+ surface area concentration as a new variable, indicating the existence of particle independent redox mechanisms. For the CAT assays the adsorption of H2O2 molecules at the particle surface modulates the efficacy of the decomposition process and must be taken into account. We design an amperometry-based experiment to evaluate the H2O2 adsorption at nanoceria surfaces, leading to the renormalization of the particle specific area. Depending on the particle type the amount of adsorbed H2O2 molecules varies from 2 to 20 nm-2. The proposed scalings are predictive and allow determining SOD and CAT catalytic properties of cerium oxide solely from physico-chemical features.

Abstract: Cerium (IV) oxide (CeO2) is the most accessible noble rare earth metal oxide for the excitation of the excitons by light-harvesting performance. The present work is focused on Erbium doped ceria nanoparticles that were beneficially obtained by hydrothermal method from cerium nitrate and Erbium nitrate as precursors for decomposition of Rhodamine-B (RhB) dye in the polluted waste water removed from the industries. Dye removal efficiency of the catalyst was found to be nearly ~94%. The structural phases, functional groups and the transitions are identified with the help of various techniques. XRD pattern determines the development of cubic phase with the particle size is 20 nm. Highly crystalline nature of as-synthesized nanomaterials with an average diameter of 35 nm was investigated by HRSEM. The crystalline size, shape and textural morphology, of the Erbium doped ceria nanostructures were analysed by HRTEM. Our results suggest, that the concentration of OH– ion determines the lattice constants and oxygen vacancy in the nanostructures which stimulate the probability of photocatalytic decomposition effect of organic pollutants, due to synergistic approach. In this context, both unhydrolyzed things and their swiftly drip from deceased or scratched cells with conceded membranes, even when the cells embrace some are outstanding attention. Although, the loss of viable cells also depends on epithelial cell dynamically conceal of numerous molar matrix.

Abstract: In this work, phase boundary engineered cerium oxide–cerium nitride (CeO2/CeN) is synthesized and used as a high performance photocatalyst for photo-thermocatalytic degradation of organic pollutants in wastewater. A CeO2/CeN composite is obtained through simply annealing CeO2 nanowires under an ammonia atmosphere. Both theoretical and experimental analyses are used to study the interfacial interaction between CeO2 and CeN crystallites. Benefiting from the interface engineering, the as-prepared CeO2/CeN composite exhibits higher photo-thermocatalytic performance than pristine CeO2 for the removal of organic pollutants. Electron spin resonance (ESR) spectroscopy and liquid chromatography tandem mass spectrometry analysis of intermediates and products are used to further confirm the synergetic effect and degradation mechanism of the photo-thermocatalysis reactions. The results of this work suggest that the synergetic effect of the photo-thermal reaction can be considered as one of the most efficient strategies for environmental pollution remediation.

Abstract: Cerium metal–organic framework based composites (Ce-MOF/GO and Ce-MOF/CNT) were synthesized by a wet chemical route and characterized with different techniques to characterize their crystal nature, morphology, functional groups, and porosity. The obtained Ce-MOF in the composites exhibit a nanorod structure with a size of ∼150 nm. The electrochemical performance of the composites was investigated in 3 M KOH and 3 M KOH + 0.2 M K3Fe(CN)6 electrolytes. Enhanced electrochemical behavior was obtained for the Ce-MOF/GO composite in both electrolytes and exhibited a maximum specific capacitance of 2221.2 F g−1 with an energy density of 111.05 W h kg−1 at a current density of 1 A g−1. The large mesoporous structure and the presence of oxygen functional groups in Ce-MOF/GO could facilitate ion transport in the electrode/electrolyte interface, and the results suggested that the Ce-MOF/GO composite could be used as a high-performance supercapacitor electrode material.

Abstract: New ceria and sulfate co-modified V2O5-TiO2 aerogel catalysts were developed, using the one-step sol gel method associated with the supercritical drying process, for Diesel DeNOx technology. N2 adsorption-desorption, XRD, H2-TPR, NH3-TPD, Raman and DRUV-Vis spectroscopy were employed to probe the physico-chemical properties of TiO2, V2O5-TiO2, V2O5-CeO2-TiO2 and V2O5-CeO2-TiO2-SO42− aerogel materials. XPS was used to obtain further information about the oxidation states of the active sites on the surface of the novel V2O5-CeO2-TiO2-SO42− aerogel catalyst. The characterization results showed the successful synthesis of a new generation of well nanostructured aerogel catalysts with high surface area, large porosity and good thermal stability. V, Ce and SO42− actives species were found highly dispersed on TiO2 surface and their presence strongly influenced the surface acidity and the redox properties of the aerogel catalysts. Sulfate anions created strong acid sites and most probably contributed to the stabilization of V and Ce surface species at their 4 + and 3 + oxidation state, respectively. In the SCR-NO by NH3 under oxygen rich conditions, V2O5-TiO2 aerogel catalyst exhibited low NO conversions in 150–500 °C temperature range. The addition of cerium significantly increased the NO conversion at low temperature (220–400 °C). However, the simultaneous incorporation of cerium and sulfate has led to a novel V2O5-CeO2-TiO2-SO42− nanostructured aerogel catalyst with superior catalytic performances, at high temperature (450–500 °C), with respect to V2O5-WO3/TiO2 commercial one (EUROCAT).

Abstract: Various methods for deliberate design electron and hole trapping materials are explored with a study on double lanthanide doped rare earth ortho phosphates. Cerium acts as recombination center while lanthanide codopants as electron trapping centers in LaPO4:0.005Ce3+,0.005Ln3+. The electron trap depth generated by lanthanide codopants can be tailored by the choice of lanthanide, and for fixed set of lanthanide dopants like in Gd1-xLaxPO4:0.005Ce3+,0.005Ho3+ solid solutions by changing x leading to conduction band (CB) engineering. Here, the electrons liberated from Ho2+ recombine through the conduction band at Ce4+ to yield Ce3+ 5d-4f emission. In contrast, samarium, europium and ytterbium are recombination centers, while Tb3+ and Pr3+ act as hole trapping centers in double lanthanide doped YPO4. For Tb3+ and Pr3+ codopants recombination is realized via hole release rather than the more common reported electron release. The holes recombine via the valence band with the electrons trapped at Yb2+, Sm2+, or Eu2+ to generate 4f-4f luminescence from Yb3+, Sm3+, or Eu3+. Lu3+ was introduced in YPO4 to tailor the valence band (VB) energy and to tune the hole trap depths of Tb3+ and Pr3+ in Y1-xLuxPO4:0.005Ln3+ solid solutions. Our results promote the deliberate design electron and hole trapping materials from deep understanding of trap level locations and on the transport and trapping processes of charge carriers.

Abstract: The modification mechanism of cerium (Ce) on oxides and multilayer carbontrides in H13 steel is investigated by industrial trials and thermodynamic calculations. The morphology, composition, and size of inclusions are analyzed by scanning electron microscopy and energy dispersive spectroscopy. The main inclusions in H13 steel without Ce content in the molten steel are MgAl2O4 spinel inclusions and multilayer carbonitrides. The carbonitrides have a multilayer structure in which MgAl2O4 acts as the nucleation core and the second layer is (Ti, V)(C, N). As the cerium content in molten steel increases from 0 to 0.03 wt%, the MgAl2O4 is effectively modified into cerium oxide (Ce–O) and cerium oxy‐sulfide (Ce–O–S), and the evolutionary process is as follows: MgAl2O4 → CeAlO3 → Ce–O and Ce–O–S. Likewise, the structure of multilayer carbonitrides in the H13 steel also changed. The MgAl2O4 and CeAlO3 act as heterogeneous nucleation cores of multilayer carbonitrides. However, Ce–O and Ce–O–S can effectively inhibit the heterogeneous nucleation of carbonitrides. The number density of large‐size carbontrides is remarkably reduced with increasing Ce content. A prediction model of optimum Ce content in molten steel is built, which has remarkable agreement with the experimental observations.

Abstract: A great challenge for cheap and active Ni‐based catalysts to be utilized for CO2 (dry) reforming of methane (DRM) reaction is their high‐carbon‐deposition problem. Herein, we designed multi‐Ni‐core@Ni phyllosilicate@CeO2 (Ni@NiPhy@CeO2) shell hollow sphere catalysts using a facile precipitation method. Compared with Ni@NiPhy without CeO2 shell, Ni@NiPhy@CeO2 exhibits high carbon resistance for the DRM reaction at both high GHSV value of 1880 L g−1 cat h−1 at 700 °C and a low reaction temperature of 600 °C. In addition, they show high and stable CH4 and CO2 conversions of 72.8 % and 79.1 % respectively at 700 °C under normal GHSV value of 36 L g−1 cat h−1. The good catalytic performance of Ni@NiPhy@CeO2 can be attributed to their high sintering resistance of both Ni and CeO2 which yields a high concentration of oxygen vacancies thereby a high catalytic performance and carbon resistance for DRM reaction. The facile synthesis method in this work can easily be applied to design other core–shell hollow catalysts such as Ni–M (M=Mg, Co, Cu, and Fe) silicate@CeO2 according to specific applications.

Abstract: In this study, the catalytic performance of the CeO2 promoted Ni-MgO-Al2O3 catalysts with different preparation methods was studied in carbon dioxide reforming of methane (CDRM) for the production of synthesis gas. The nitrogen adsorption/desorption (BET), X-ray diffraction (XRD), temperature-programmed reduction and oxidation (TPR and TPO), scanning electron microscopy (SEM) techniques were used to characterize the samples. The obtained results showed that the Ce addition to Ni-MgO-Al2O3 catalyst with the high specific surface area has a significant influence on the metal crystallite size, reduction properties, and coke deposition. The CeO2-Ni-MgO-Al2O3 catalyst with cerium content of 3 wt.% prepared by the impregnation method possessed the highest resistance against carbon formation in CDRM. In addition, the catalytic results confirmed that the feed ratio (CO2/CH4) and GHSV affected the catalytic activity. However, the CH4 and CO2 conversions improved when the cerium was added to Ni-MgO-Al2O3 catalysts.

Abstract: Molecular cerium complexes are a new class of tunable and energy-efficient visible- and UV-luminophores. Understanding and controlling the emission brightness and color are important for tailoring them for new and specialized applications. Herein, we describe the experimental and computational analyses for series of tris(guanidinate) (1–8, Ce{(R2N)C(NiPr)2}3, R = alkyl, silyl, or phenyl groups), guanidinate-amide [GA, A = N(SiMe3)2, G = (Me3Si)2NC(NiPr)2], and guanidinate-aryloxide (GOAr, OAr = 2,6-di-tert-butylphenoxide) cerium(III) complexes to understand and develop predictive capabilities for their optical properties. Structural studies performed on complexes 1–8 revealed marked differences in the steric encumbrance around the cerium center induced by various guanidinate ligand backbone substituents, a property that was correlated to photoluminescent quantum yield. Computational studies revealed that consecutive replacements of the amide and aryloxide ligands by guanidinate ligand led to less nonradia...

Abstract: This present work focuses on the synthesis of cerium-doped hydroxyapatite (Ce/HAp-US) using an ultrasonic-assisted sol-gel technique under varying concentration of Ce from 0.5% to 2.0%. The preparative method utilized the stoichiometric molar ratio of Ca to P of 1.67 where the Ce/HAp samples were calcined at 600 °C for 2 h. The structural properties of Ce/HAp samples were characterized by various techniques including X-ray absorption near edge spectroscopy (XANES), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Results from the XANES spectra of xCe/HAp samples at the Ce L3-edge reveal that the dominant species of cerium was Ce4+ along with some Ce3+, which have been incorporated into the HAp lattice. Results of the EDX analysis show that the Ca/P molar ratio of xCe/HAp decreased with an increase in Ce content. XRD analysis confirms that Ce3+ and Ce4+ were partially incorporated into the hexagonal framework of HAp and rhombohedral structure of β-tricalcium phosphate (β-TCP). FT-IR measurements identified the main functional groups of Ce/HAp to be hydroxyl (OH−), phosphate ( PO 4 3 - ) and carbonate ( CO 3 2 - ). The morphology obtained from TEM analysis illustrates that pure HAp-US is composed of very fine spherical particles. By incorporating Ce ions into the HAp lattice, the presence of dense dark spots, possibly the loaded Ce species, were observed.

Abstract: Nickel/cerium–zirconium oxide (Ni/Ce50–Zr50) and manganese promoted Ni/Ce50–Zr50 (Ni–Mn/Ce50-Zr50) catalysts were prepared using an impregnation method and used in the dry reforming of methane. The catalysts were characterized by H2 temperature-programmed reduction, transmission electron microscopy, X-ray photoelectron spectroscopy, CO2 temperature-programmed desorption, X-ray diffraction, in situ diffuse reflectance infrared Fourier transform spectra, and thermogravimetric analysis. A manganese promoter facilitated the formation of the reaction intermediate—CH2OH species at low temperature. A synergistic effect between Ni and Mn species enhanced the adsorption of CO2 on Ni–Mn/Ce50-Zr50. A manganese promoter not only enhanced the catalytic activity but also led to a high H2/CO ratio product. At 600 °C, under atmospheric pressure, with 20 000 h–1 gas hourly space velocity and CH4/CO2/Ar = 1:1:8, on a Ni–Mn/Ce50-Zr50 catalyst, the CH4 conversion (38.7%), CO2 conversion (40.4%), and the H2/CO ratio (0.83) we...

Abstract: The presence of contaminants in potable water is a cause of worldwide concern. In particular, the presence of metals such as arsenic, lead, cadmium, mercury, chromium can affect human health. There is thus a need for advanced techniques of water decontamination. Adsorbents based on cerium dioxide (CeO2), also named ‘ceria,’ have been used to remove contaminants such as arsenic, fluoride, lead and cadmium. Ceria and composites display high surface area, controlled porosity and morphology, and abundance of functional groups. They have already found usage in many applications including optical, semiconductor and catalysis. Exploiting their attractive features for water treatment would unravel their potential. We review the potential of ceria and its composites for the removal of toxic metal ions from aqueous medium. The article discusses toxic contaminants in water and their impact on human health; the synthesis and adsorptive behavior of ceria-based materials including the role of morphology and surface area on the adsorption capacity, best fit adsorption isotherms, kinetic models, possible mechanisms, regeneration of adsorbents; and future perspectives of using metal oxides such as ceria. The focus of the report is the generation of cost-effective oxides of rare-earth metal, cerium, in their standalone and composite forms for contaminant removal.

Abstract: This work demonstrates the inhibition effects of single-stranded (ssDNA) on the oxidase-like activity of a mixed-valence state cerium-based metal-organic framework, denoted as MVC-MOF. The MVC-MOF was synthesized by partial oxidation of cerium(III) which leads to the presence of both Ce(III) and Ce(IV) ions. The latter endows the MVC-MOF with a typical oxidase-like activity. However, on addition of ssDNA, the catalytic activity of the MVC-MOF is inhibited because it binds the MVC-MOF and thereby shield its active sites. This prevents the access of substrates. The inhibition by ssDNA depends on its length but not its sequence. By contrast, negligible changes in the oxidase-mimicking activity are observed if double-stranded DNA (dsDNA) is added. By employing a thymine-rich ssDNA (T-ssDNA) as a model DNA, a colorimetric assay was developed for the determination of Hg(II). This ion binds to T-ssDNA and causes the formation of T-dsDNA. Hence, the oxidase-mimicking activity is compromised. By using the oxidase substrate 3,3′,5,5′-tetramethylbenzidine that gives a colored product in the presence of oxygen, the assay has a linear response that covers 0.05 to 6 μM Hg(II) with a detection limit of 10.5 nM, and exhibits high selectivity over other metal ions. The assay was successfully applied to the determination of Hg(II) in environmental water samples.