Pure Ceria Research Articles

Pyrolysis of bamboo over Ce/Fe composite metal oxide catalyst to enhance the production of hydrocarbons and ketonic hydrocarbon precursors

AbstractTo obtain high‐value bio‐oil, pure ceria (CeO2) and a series of Ce/Fe composite metal oxides were synthesized via precipitation method and were used to enhance hydrocarbons and ketones production during catalytic pyrolysis of bamboo sawdust. The characterization results were comprehensively analyzed and revealed that doping CeO2 with Fe promoted the formation of a solid solution structure, which further increased the surface area and number of oxygen vacancies of the catalyst for deoxygenation. Experimental consequences demonstrated that, compared to non‐catalytic trial, the catalytic pyrolysis over CeO2 generated lower amounts of acids and aldehydes, and enhanced the conversion of large oxygenates to monofunctional hydrocarbon precursors via decarboxylation, deoxidation, and ketonization. The concentrations of hydrocarbons and ketones obtained over Ce/Fe catalysts were significantly higher than those obtained over CeO2, and that was attributed to the higher surface area and oxygen storage capacity of Ce/Fe catalysts. Particularly, the composite catalyst with the Ce/Fe molar ratio of 4 (Ce0.8Fe0.2) presented the most optimal deoxidation capacity in this study. The relative concentration of hydrocarbons generated over Ce0.8Fe0.2 was the highest, and monocyclic aromatics and short‐chain aliphatic hydrocarbons accounted for 47.13% and 29.72%, respectively, of the total hydrocarbons. Simultaneously, the amount of ketones, the main hydrocarbon precursors, obtained over Ce0.8Fe0.2 was significantly higher than that obtained over CeO2, and the fraction of linear and cyclic ketones of the total ketones increased from 45.96% for the non‐catalytic pyrolysis to 97.57%. This further confirmed that the mesoporous Ce/Fe composite catalysts efficiently catalyzed the aldol condensation and ketonization reactions.

Assessment of Cell Toxicity and Oxidation Catalytic Activity of Nanosized Zinc-doped Ceria UV Filter

The abundance of cerium in natural resources, its ability to absorb UV light while being transparent to visible light, as well as low photocatalytic activity make ceria (CeO2) a promising candidate for UV filter material in sunscreens. Doping with different elements can further decrease ceria catalytic and photocatalytic activity, thus preventing the <br /> degradation of other sunscreen ingredients. In this work, pure and zinc-doped ceria <br /> nanoparticles were prepared by a simple and environmentally benign hydrothermal synthesis, and characterized using various techniques. Fine ceria and doped ceria nanoparticles with particle sizes of 6.1±0.9 and 4.2±0.4 nm were prepared. In both samples, cubic ceria was the only crystalline phase, but the homogeneous distribution of zinc in the doped sample was confirmed by energy dispersive X-ray spectrometry. Nanoparticles exhibited transparency in the visible region and absorbance in the UV region with band gap of 3.23 to 3.14 eV for pure and doped sample, respectively. The oxidation stability time, determined through Castor oil oxidation process, was 23 hours for the pure and 15 hours for the doped sample, which is quite satisfactory. In vitro cytotoxicity study showed that the prepared nanoparticles were well tolerated by human skin keratinocytes (HaCaT cell line) with no significant differences in skin cells viability. However, further investigations on in vivo systems are necessary to reach a firm conclusion regarding the toxicity of ceria and doped ceria nanoparticles, and other potential dopants should be considered for improvement of ceria properties.

Glycine-assisted hydrothermal synthesis of pure and europium doped CeO2 nanoparticles and their structural, optical, photoluminescence, photocatalytic and antibacterial properties

Pure and europium doped cerium dioxide (CeO2) nanoparticles were synthesized for the first time via glycine-assisted hydrothermal process and comparatively investigated their structural, optical, photoluminescence, photocatalytic and antibacterial properties. The synthesized pure cerium dioxide (PCDO) and Eu3+ doped cerium dioxide (ECDO) samples were subjected to the powder XRD, W-H plot, TEM, EDX, XPS, UV–visible, PL, photocatalytic and antibacterial studies. Based on the above analysis, ECDO found relatively smaller size, higher band gap and oxygen vacancy defects, better photocatalytic degradation and antibacterial properties compared to the PCDO sample. Moreover, the ferromagnetism characteristics of the ECDO were found in the M−H loop.

Experimental demonstration of vanadium-doped nanostructured ceria for enhanced solar thermochemical syngas production

Solar-driven thermochemical routes enable storage of solar energy in chemical form for off-sun use by means of synthetic fuel production. Here, we explore vanadium-doped ceria materials for partial oxidation of methane, followed by an efficient splitting of CO2 and H2O into syngas. The primary role of the dopant is to enhance and optimize the cycle capacity of ceria at low isothermal temperatures. The intake capacity of ceria lattice reached its saturation level with 5% of vanadium addition and further increase in V (%) forms a secondary phase (CeVO4), which significantly affects the role of vanadium towards the syngas production performance enhancement. For instance, vanadium atoms migrate to the powder surface with V ≥ 5% and cause cracking of methane, while the lattice vanadium atoms (V < 5%) enhances the cycle capacity by providing reducing sites for the redox reactions and improve the oxygen mobility by inducing lattice distortions. The cycle capacity of V-doped ceria is four times higher than pure ceria, while the temperature for the methane partial oxidation reaction is decreased by up to 178 °C with elevated peak syngas production rates, after vanadium doping. The long-term redox activity of V-doped ceria materials for 200 cycles with up to 4.5 mmol g−1/cycle of syngas is reported. This study demonstrates the concept of utilizing V-doped ceria to produce syngas via high temperature chemical looping reforming of methane and helps to strategically evaluate the redox materials as an efficient oxygen carrier for syngas production.

A kinetic model for evolution of H2 and CO over Zr-doped ceria

Among notable catalytic assisted processes by ceria-abased materials are the production reactions of H2 and CO from solar thermochemical splitting of water and carbon dioxide, respectively, for applications pertinent to hydrogen fuel cell and synthesis of syngas. Doping ceria with isovalent cations, most notably Zr, was shown to enhance the yield of O2, H2, and CO. Via sophisticated measurements techniques, literature provided several global-like rates for the overall evolutions of H2 and CO. However, these values remain without a mechanistic verification by means of first-principles calculations. Herein, we map out mechanisms and construct a detail chemistry kinetic model for the dissociative adsorption of H2O and CO2 over pure and Zr-decorated ceria surfaces. The overarching objective of the kinetic model is to deduce temperature-dependent profiles that account for the experimentally observed evolution of O2, H2, and CO during the redox cycles of ceria and to reveal the effect of Zr dopants. Ce surface atoms in the latter incur higher positive charges, and hence more affinity to capture gas phase molecules. Splitting of H2O into a gas phase H2 over the Zr-substituted surface ensues in two consecutive steps through activation energies of 77.7 kJ/mol and 191.2 kJ/mol. Our computed rate constant for evolution of H2 over ceria amounts to 2.67 mL/g. min, within the narrow range of the experimental values scattered between 1.5–5.4 mL/g. min. Formation of H2 and CO arises at a ∼ 100 K lower temperature over the Zr-doped surface in reference to pure ceria. The developed kinetic model is expected to describe - on a precise atomic basis - the H2O/CO2 redox cycles of ceria-based materials and the promoting effects of dopants.

Structural and Electrical Study of Boron Doped Ceria Ceramics Electrolytes for SOFC

Abstract The world’s present reserves in terms of fossil fuels are exhausting speedily. Such rapid energy consumption can be caused of unsustainable worldwide progress. Therefore, the researcher’s challenge is to identify the most efficient and economical energy conversion method to provide a viable replacement for the ongoing conventional energy converters. In this context, fuel cell technology (solid oxide fuel cells (SOFCs)) can play a key role and convert hydrocarbon energy into electrical energy. The conventional electrolyte YSZ based SOFCs work at high temperature ∼1000 °C. In this present research, the new ceramics electrolytes materials boron doped ceria (BDC) have been developed by auto-combustion technique. The prepared materials have been characterized by X-ray diffraction (XRD) and TEM. The crystallite sizes of all prepared samples are in the range of 50–80 nm applying Scherer’s formula. The electrical studies and fuel cell performance have been completed at temperature ≤ 700 °C. The doping of boron into ceria has significantly improved the electrical conduction of pure ceria oxide which has been studied using four-probe setup. The maximum ionic conductivity and power density of B0.20:Ce0.80 (molar ratio) electrolyte material named as E4 have been achieved and found to be 0.09 S/cm at 700 °C and 198.125 mW/cm2 at 650 °C. It has been observed that all electrochemical results are consistent with the doping of boron into ceria.

Ionic and thermal conductivity of pure and doped ceria by molecular dynamics

Numerous parametrizations of pair potentials have been developed to investigate various properties of pure and doped ceria in recent decades. In this paper, we assess frequently applied sets of pair potentials for pure and gadolinia doped ceria with respect to the prediction of the bulk properties lattice parameter, bulk modulus, and thermal expansion coefficient as well as defect properties including defect formation energies, defect interactions and anion migration energy. We furthermore apply molecular dynamics simulations to obtain the thermal and ionic conductivity of the material using the Green-Kubo and electric field methods, respectively. We found that none of the applied potentials is able to reproduce all of the monitored properties correctly. Nonetheless, we provide a recommendation of suitable potential sets for different applications.

Cerium oxide (CeO2-x) nanoparticles with high Ce3+ proportion synthesized by pulsed plasma in liquid

Cerium oxide (CeO2-x) nanoparticles were synthesized using a simple one-step method known as the pulsed plasma in liquid (PPL). XRD analysis showed the production of pure cubic cerium oxide (Fm 3‾ m). HRTEM and XANES analysis confirmed the monophase cubic CeO2-x, and exclude the presence of the hexagonal Ce2O3 and/or mix phase of CeO2/Ce2O3 in the particle layers. HRTEM analysis showed that most particles were about 3 nm in diameter. XPS analysis showed that the cerium oxide nanoparticles synthesized by the PPL method had a higher Ce3+ proportion (42.2%) than some commercial powders, and also higher than the previous reported nanoparticles. The present cerium oxide nanoparticles showed high visible light-induced photocatalytic activity in the degradation of methyl orange (MO) and better polishing characteristics of quartz glass, compared to commercial samples. These results may attribute to the high Ce3+-ion content and/or the small particle size.

Two-step CO2 and H2O splitting using perovskite-coated ceria foam for enhanced green fuel production in a porous volumetric solar reactor

Solar thermochemical cycles offer a viable option for the production of green synthetic fuels from CO2 and H2O. Two-step cycles using redox materials consist of a high-temperature reduction creating oxygen vacancies, followed by a re-oxidation step with an oxidant gas (CO2 and/or H2O), resulting in CO and/or H2 production. This study focuses on the thermochemical performance in a solar reactor of a new kind of composite reactive material: reticulated ceria foam with uniform perovskite coating, forming a dual-phase layered heterostructure. La0.5Sr0.5Mn0.9Mg0.1O3 (LSMMg) was selected as perovskite coating due to its high fuel productivity and thermochemical stability upon cycling. The perovskite coating improves the reduction step by increasing the reduction extent reached by the reactive material. The results revealed significant enhancement of oxygen exchange in the dual-phase composite material during reduction compared to individual components. The enhanced reduction extent had a beneficial effect on the oxygen release rate and the total amount of fuel produced by CO2 and H2O splitting, whereas an adverse impact on the peak rate during H2/CO evolution was noticed. Decreasing the reduction pressure allowed enhancing the non-stoichiometric oxygen extent, while the re-oxidation extent increased with the inlet oxidant molar fraction. With suitable operating conditions (reduction at 0.100 bar and oxidation in 100 % CO2), the LSMMg-coated ceria foam produced a higher amount of fuel but with lower fuel production rate in comparison with pure ceria foam. This study points out the beneficial effects of composite redox materials consisting of LSMMg-coated ceria foam in enhancing the oxygen exchange capacity of ceria for solar fuel production.

Study of doped mesoporous ceria with tailored oxygen vacancies for enhances activity for ethylbenzene oxidation application

Herein, we present a ligand-assist induction self-assembly method to prepare mesoporous CeO2 (mCeO2) nanospheres. Then, a series of mCeO2 catalysts with Ni or Co ions doped with various Ce/Ni (Co) ratios were prepared by this method. These mCeO2:xNi/Co (mCeO2 with different mound Ni or Co ions doping) samples were studied using a range of characterization techniques (XRD, N2 adsorption-desorption, SEM, TEM, XPS, H2-TPR, O2-TPD and Raman spectroscopy). Both mCeO2 and mCeO2:xNi/Co nanospheres show high surface areas. XPS spectra reveal that the ratios of Ce3+/Ce4+ increase as the doping concentration of Ni/Co ions increasing, which indicated that mCeO2:xNi/Co samples are more reducible than pure mCeO2. The H2-TPR, O2-TPD, and Raman analysis results reveal that the doping of Ni or Co ions significantly increased the concentration of surface oxygen vacancies in mCeO2. As for ethylbenzene oxidation reaction, doping-mesoporous ceria catalysts exhibited a superior catalytic activity when compared to pure mesoporous ceria catalysts prepared by the same method.

Structural characterization and electrical properties of Ce1-xSmxO2-δ by sucrose-pectin–assisted auto combustion process

Ce1-xSmxO2-δ (x = 0.0, 0.1, 0.2, 0.3) samples were prepared by sucrose and pectin–assisted auto combustion method. The phase identification, morphology, spectroscopic properties, and electrical properties of the samples are studied by XRD, FESEM, Raman spectrometer, and impedance spectroscopy. Rietveld refinement was carried on XRD samples for structural properties. Samples showed a single phase with the cubic fluorite structure. The average crystallite size was in the range of 10–17 nm. The sample Ce0.8Sm0.2O2−δ exhibits improved conductivity with low activation energy in comparison with pure ceria.

Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation.

We investigate the mechanism of H2 activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce3+ ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces. Although the reactivity of ceria toward H2 oxidation improves when a fraction of Ce cations is substituted with Ag, the concentration of reduced Ce3+ ions in Ag-modified ceria is found to be lower than in pure ceria under the same conditions. This behavior is observed even though the number of surface oxygen vacancies caused by the thermal treatment under hydrogen exposure is larger for the Ag-modified surface. These results are explained in terms of a change of the oxidation state of the surface Ag, which is able to acquire some of the extra surface electrons created by the oxygen vacancies and the adsorbed hydrogen atoms. Our findings provide new insights into the reactivity of Ag-modified ceria, which has been proposed as a promising alternative to platinum electrodes in electrochemical devices.

Europium-Doped Ceria-Gadolinium Mixed Oxides: PARAFAC Analysis and High-Resolution Emission Spectroscopy under Cryogenic Conditions for Structural Analysis.

Gadolinium-doped ceria or gadolinium-stabilized ceria (GDC) is an important technical material due to its ability to conduct O2- ions, e.g., used in solid oxide fuel cells operated at intermediate temperature as an electrolyte, diffusion barrier, and electrode component. We have synthesized Ce1-xGdxO2-y:Eu3+ (0 ≤ x ≤ 0.4) nanoparticles (11-15 nm) using a scalable spray pyrolysis method, which allows the continuous large-scale technical production of such materials. Introducing Eu3+ ions in small amounts into ceria and GDC as spectroscopic probes can provide detailed information about the atomic structure and local environments and allows us to monitor small structural changes. This study presents a novel approach to structurally elucidate europium-doped Ce1-xGdxO2-y:Eu3+ nanoparticles by way of Eu3+ spectroscopy, processing the spectroscopic data with the multiway decomposition method parallel factor (PARAFAC) analysis. In order to perform the deconvolution of spectra, data sets of excitation wavelength, emission wavelength, and time are required. Room temperature, time-resolved emission spectra recorded at λex = 464 nm show that Gd3+ doping results in significantly altered emission spectra compared to pure ceria. The PARAFAC analysis for the pure ceria samples reveals a high-symmetry species (which can also be probed directly via the CeO2 charge transfer band) and a low-symmetry species. The GDC samples yield two low-symmetry spectra in the same experiment. High-resolution emission spectra recorded under cryogenic conditions after probing the 5D0-7F0 transition at λex = 575-583 nm revealed additional variation in the low-symmetry Eu3+ sites in pure ceria and GDC. The total luminescence spectra of CeO2-y:Eu3+ showed Eu3+ ions located in at least three slightly different coordination environments with the same fundamental symmetry, whereas the overall hypsochromic shift and increased broadening of the 5D0-7F0 excitation in the GDC samples, as well as the broadened spectra after deconvolution point to less homogeneous environments. The data of the Gd3+-containing samples indicates that the average charge density around the Eu3+ ions in the lattice is decreased with increasing Gd3+ and oxygen vacancy concentration. For reference, the Judd-Ofelt parameters of all spectra were calculated. PARAFAC proves to be a powerful tool to analyze lanthanide spectra in crystalline solid materials, which are characterized by numerous Stark transitions and where measurements usually yield a superposition of different contributions to any given spectrum.

Morphology and chemical states of Ni supported on Ti-modified CeOx(111) interfaces

Low coverage of Ni was deposited onto well-ordered Ti-doped CeOx(111) (1.5 < x < 2) thin films at 300 K under ultrahigh vacuum conditions. The morphology and interaction of Ni with Ti-ceria interfaces were investigated with X-ray photoelectron spectroscopy and scanning tunneling microscopy. Ti doped-CeOx(111) mixed oxide interfaces can be prepared by physical vapor deposition of submonolayer coverages of Ti onto both fully oxidized CeO2(111) and partially reduced thin films (e.g. CeO1.92) at room temperature followed by heating to 700 K. Ti is oxidized to Ti4+ at the cost of ceria reduction. Titania features are uniformly distributed on CeOx with an average height of 0.31 nm. Upon Ni deposition over both Ti-CeO2(111) and Ti-CeO1.92 surfaces at 300 K, oxidation of Ni to NiO occurs and thus both metallic Ni and Ni2+ species are present in the particles formed over Ti-CeOx surfaces. The extent of Ni oxidation depends on the nature of Ti-CeOx. 28% of deposited Ni is in the +2 state over Ti-CeO2. With heating to 700 K, the percent of the Ni2+ species increases to 37% over Ti-CeO2. However, metallic Ni is the predominant species over Ti-CeO1.92. The difference in the Ni species present in the particles results in a different particle sintering behavior with heating. Compared to pure ceria, modifications of ceria with addition of Ti metal dopants can significantly stabilize Ni as smaller nanoparticles upon heating.

NADİR TORPAQ ELEMENTLƏRİNİN LANTANOİDLƏR QRUPUNA AİD OLAN SERİUM METALININ XÜSUSİYYƏTLƏRİ VƏ ADSORBSİYA XASSƏLƏRİNİN ÖYRƏNİLMƏSİ

Cerium was the first metal discovred among rare earth elements. The chemical symbol of the serium is "Ce." The atomic number is 58, the atomic mass is 140.11, and the density is 6.77. The melting point is 799 degrees and the boiling point is 3443 degrees. It is silvery, silvery-white, soft, artificial metal. Pure cerium can be cut with a knife and can easily be used. Cerium is named after the düarf planet "Ceres", it has different characterisatins from other lanthanoids. Therefore, the scope of use is different and broad. It is an element that can be used in burn medicines. After the discovery, the gas lamp was used as a torch. The flame burner consists of 50% cerium. Cerium has no biological role for human health. On average it shows toxic properties. Cerium turnings self-ignite in air between 65 and 80 degrees. The adsorption properties of aqueous solutions with various composite adsorbents of cerium metal were studied. At this time ph, concentration, contact duration, etc. evaluated.The pH 5,5-pH 6,5 range for the cerium was determined to be the optimal pH. Isotherm models such as Langmur and Frendlix have also been studied. Desorption specifications are defined for reuse. Key words: cerium metal, adsorption, adsorption properties

Quantitative nanoscale tracking of oxygen vacancy diffusion inside single ceria grains by in situ transmission electron microscopy

Oxygen vacancy formation and migration in ceria is critical to its electrochemical and catalytic properties in systems for chemical and energy transformation, but its quantification is rather challenging especially at atomic-scale because of disordered distribution. Here we report a rational approach to track oxygen vacancy diffusion in single grains of pure and Sm-doped ceria at −20 °C to 160 °C using in situ (scanning) transmission electron microscopy ((S)TEM). To create a gradient in oxygen vacancy concentration, a small region (∼30 nm in diameter) inside a ceria grain is reduced to the C-type CeO1.68 phase by the ionization or radiolysis effect of a high-energy electron beam. The evolution in oxygen vacancy concentration is then mapped through lattice expansion measurement using scanning nano-beam diffraction or 4D STEM at a spatial resolution better than 2 nm; this allows direct determination of local oxygen vacancy diffusion coefficients in a very small domain inside pure and Sm-doped ceria at different temperatures. Further, the activation energies for oxygen transportare determined to be 0.59, 0.66, 1.12, and 1.27 eV for pure CeO2, Ce0.94Sm0.06O1.97, Ce0.89Sm0.11O1.945, and Ce0.8Sm0.2O1.9, respectively, implying that activation energy increases due to impurity scattering. The results are qualitatively supported by density functional theory (DFT) calculations. In addition, our in situ TEM investigation reveals that dislocations impede oxygen vacancy diffusion by absorbing oxygen vacancies from the surrounding areas and pinning them locally. With more oxygen vacancies absorbed, dislocations show extended strain fields with local tensile zone sandwiched between the compressed ones. Therefore, dislocation density should be reduced in order to minimize the resistance to oxygen vacancy diffusion at low temperatures.

Infinite dilution in doped ceria and high activation energies

Oxygen ion diffusion determines the performance of materials in energy conversion, energy storage and catalysis. For nominally pure cerium oxide, experiments measure high activation enthalpies while calculations predict low activation enthalpies. Moreover, for doped oxides, e.g. doped ceria, experiments show a high activation enthalpy for both pure ceria and for high dopant fractions, leading to a minimum in activation enthalpy for small dopant fractions. While for high dopant fractions the increase in activation enthalpy is correlated with the association of oxygen vacancies and dopant ions, which are both created by doping, the minimum in activation enthalpy is assumed in the literature to be related to the maximum in ionic conductivity at similar dopant fractions. In this study, density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations are combined in order to calculate the ionic conductivity and activation enthalpy in doped oxides. We show that the experimental ionic conductivity and activation energy in nominally pure cerium oxide is dominated by impurities. We resolve the discrepancy between activation enthalpies of nominally pure oxides in experiments as opposed to calculations. This will lead to a more comprehensive understanding of the oxygen ion conductivity and its underlying atomistic mechanisms. Moreover, such a focus will be of great benefit to the future development of sustainable and efficient materials.

Effect of CeH2.73-CeO2 Composites on the Desorption Properties of Mg2NiH4.

A series of CeH2.73/CeO2 composites with different ratios of hydride and oxide phases are prepared from the pure cerium hydride via oxidation treatments in the air at room temperature, and they are subsequently doped into Mg2NiH4 by ball milling. The desorption properties of the as-prepared Mg2NiH4+CeH2.73/CeO2 composites are studied by thermogravimetry and differential scanning calorimetery. Microstructures are studied by scanning electron microscopy and transmission electron microscopy, and the phase transitions during dehydrogenation are analyzed through in situ X-ray diffraction. Results show that the initial dehydrogenation temperature and activation energy of Mg2NiH4 are maximally reduced by doping the CeH2.73/CeO2 composite with the same molar ratio of cerium hydride and oxide. In this case, the CeH2.73/CeO2 composite has the largest density of interface among them, and the hydrogen release effect at the interface between cerium hydride and oxide plays an efficient catalytic role in enhancing the hydrogen desorption properties of Mg2NiH4.

The oxygen ion conductivity of Lu doped ceria

The oxygen ion conductivity of polycrystalline samples of Lu doped ceria is studied using impedance spectroscopy. Lutetium doped ceria is of particular interest as Lu has a similar ionic radius as the host cation Ce. The change of the ionic conductivity as a function of the Lu dopant fraction is investigated in detail revealing a similar behavior as Sm doped ceria that has one of the highest ionic conductivity in ternary cerium oxides. In comparison with simulations, the experimental dependence of the conductivity on the dopant fraction reveals that migration barriers for oxygen vacancy jumps around Lu ions are slightly higher than for jumps in pure ceria. The absolute conductivity is small due to the strong trapping of oxygen vacancies near Lu dopants.

Effects of Transition Metal Doping to Cerium-Oxides in Thermal Reduction Reaction

Considering our lives, novel energy production is so required, and many scientists have been investigated this problem from a lot of views. One of the ways for the new energy productions is the solar power thermochemical production by an oxidation-reduction reaction of the ceramics CeO2 (ceria). In this research, the ceria is used for obtaining an H2 gas in vapor reaction in high-temperature thermal equipment which has a heat production system consisting by focused sun light. Nowadays technology has been also developed to keep a human living, not to harm the Earth environment. From these points, it is realized that how important the H2 gas is for our lives, so we are trying to improve the thermochemical H2 gas production by means of a ceria as a catalyst. Our purpose in this study is, to point out what effects occur in doped ceria’s thermal reduction (TR) reaction by using DV-Xα method. Comparing the models between the pure ceria and the Mn doped ceria, we have realized the difference by the reaction. In this appearance, one of the considerations is a view from p-DOSs (partial-Density of States), in which there are different O-2p DOSs by different crystal structures. From this view, we considered that the ceria structure would become more stable to keep the stable cyclic thermal reaction in Mn doped ceria.