Addition Of Transition Metal Oxides Research Articles

Improving the Performance of a Co-CeO2 Catalyst for Hydrogen Production via Water Gas Shift Reaction by Addition of Transition Metal Oxides

Improving the Performance of a Co-CeO₂ Catalyst for Hydrogen Production via Water Gas Shift Reaction by Addition of Transition Metal Oxides

VAPOR-PHASE OXIDATION OF 2-METHYLPYRIDINEON V-Zr-O-CATALYSTS MODIFIED WITH TIN AND NIOBIUM OXIDES

Vapor-phase catalytic oxidation of pyridine alkyl derivatives is an effective method for obtaining a variety of physiologically active substances that are widely used in practice, as well as for the synthesis of solvents, starting materials for the production of dyes, herbicides, etc. For the process, a cheap oxidizing agent is used -atmospheric oxygen. Of great importance is the choice and creation of an active and selective process catalyst. Basically, the oxidation processes are carried out in the presence of catalysts based on vanadium oxide with the addition of transition metal oxides. The aim of the work.Study of the behavior of V-Zr-O catalysts modified with tin and niobium oxides in the vapor-phase oxidation of 2-methylpyridine. Metodology. Vapor-phase oxidation of 2-methylpyridine was carried out in a flow-type reactor simulating an element of an industrial contact apparatus. The reaction products were analyzed by chromatographic method. Results and disscution. It was shown that the component composition of the contact determines the catalytic action in the studied process, affecting not only the activity of the catalyst, but also the composition of the reaction products. By varying the conditions of the vapor-phase catalytic oxidation of 2-methylpyridine, such as temperature, the molar ratio of the initial substance:О2:Н2О, it is possible to obtain both oxygen-containing derivatives (pyridine-2-aldehyde and picolinic acid) and pyridine, a product of oxidative demethylation. Conclusion.It has been established that pyridine, which is one of the important products of the vapor-phase oxidation of 2-methylpyridine, can be obtained in 85.3% yield on a V-Zr-O catalyst modified with niobium oxide.

Trends on the Development of Hybrid Supercapacitor Electrodes from the Combination of Graphene and Polyaniline

The high demand for efficient energy devices leads to the rapid development of energy storage systems with excellent electrochemical properties, such as long life cycles, high cycling stability, and high power density. SC is postulated as a potential candidate to fulfill this demand. The combination of graphene and polyaniline can create SC electrodes with excellent electrical conductivity, high specific surface area, and high capacitance. The graphene/polyaniline hybrid electrodes represent an attractive means to overcome the major drawbacks of graphene or polyaniline non-hybrid (single) electrode materials. In this review article, the trend in the development of various graphene/polyaniline hybrid electrodes is summarized, which includes the zero-dimension graphene-quantum-dots/polyaniline hybrid, one-dimension graphene/polyaniline hybrid, two-dimension graphene/polyaniline hybrid, and three-dimension hydrogel-shaped graphene/polyaniline hybrid. Several strategies and approaches to enhance the capacitance value and cycling stability of graphene/polyaniline hybrid electrodes are discussed in this review article, such as the addition of transition metal oxides and metal-organic frameworks, and modification of graphene into functionalized-graphene. The performance of the electrodes prepared from the combination of graphene with other conducting polymers (i.e., polypyrrole, polythiophene, and polythiophene-derivatives) is also discussed.
 
 

Auδ−–Ov–Ti3+: Active site of MOx-Au/TiO2 catalysts for the aerobic oxidation of 5-hydroxymethylfurfural

Despite wide applications of noble metal-based catalysts in 5-hydroxymethylfurfural (HMF) oxidation, promoting the catalytic performance at low loading amounts still remains a significant challenge. Herein, a series of metal oxide modified MOx-Au/TiO2 (M = Fe, Co, Ni) catalysts with low Au loading amount of 0.5 wt% were synthesized. Addition of transition metal oxides promotes electron transfer and generation of the Auδ−–Ov–Ti3+ interface. A combination study reveals that the dual-active site (Auδ−-Ov-Ti3+) governs the catalytic performance of the rate-determining step, namely hydroxyl group oxidation. Auδ− site facilitates chemisorption and activation of O2 molecules. At the same time, Ov-Ti3+ site acts as the role of “killing two birds with one stone”: enhancing adsorption of both reactants, accelerating the activation and dissociation of H2O, and facilitating activation of the adsorbed O2. Besides, superoxide radicals instead of base is the active oxygen species during the rate-determining step. On this basis, a FDCA yield of 71.2% was achieved under base-free conditions, complying with the “green chemistry” principle. This work provides a new strategy for the transition metal oxides modification of Au-based catalysts, which would be constructive for the rational design of other heterogeneous catalysts.

The role of some metal ions in enhancement of photocatalytic activity of Fe2O3-V2O5 binary oxide.

Fe2O3-V2O5 mixed oxides were synthesized with solid-state dispersion (SSD) and coprecipitation methods. In addition, transition metal oxides such as CuO, NiO, and CO3O4 were successfully loaded on the synthesized catalyst (Fe2O3-V2O5) using the SSD method. The composite catalysts were inspected for their photocatalytic activities in degrading 2,4-dichlorophenol under UV light enforcement. The produced samples were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, scanning electron microscopy, photoluminescence, and the Brunauer–Emmett–Teller method. The addition of transition metal oxides improved the photocatalytic activity of Fe2O3-V2O5 (SSD). 1CuO wt% Fe2O3-V2O5 exhibited the highest percentage of 2,4-dichlorophenol degradation (100%) and the highest reaction rate (1.83 mg/L min) in 30 min. This finding is attributed to the distribution of CuO.

Addition of transition metal oxides on silver tellurite glass for radioactive iodine immobilization

The long-lived radioactive forms of iodine pose significant environmental threats. Therefore, it is important to capture and immobilize radioactive iodine. In this study, an iodine immobilization matrix was developed and investigated by adding transition metal oxides such as WO3, MoO3, and V2O5 to the AgI-Ag2O-TeO2 glass system. The immobilization was confirmed by melting the glass precursor mixtures at 800°C for 1 h without a significant loss of the elements that comprising the glass. The loading of iodine in the matrix was approximately 13-15% by weight, excluding elemental oxygen. The normalized releases of all the elements obtained by PCT-A were below 10−1 g/m2, thereby satisfying the USA regulations (2 g/m2). The structural factors related to the chemical durability of the glass were discussed. The addition of WO3, MoO3, and V2O5 suppressed the release of iodine by densifying the TeO4 polyhedra. The silver release was not significantly affected by increasing the concentrations of the transition metal oxides. The additives stabilized tellurium, which is a glass network former, to prevent its release from the glass matrix. All the transition metals considered in this study remained stable in the silver tellurite glass in comparison to the release of tellurium.

ZnO–PVA Polymer Matrix with Transition Metals Oxide Nano-fillers for High Dielectric Mediums

Polymer-based nanocomposites are considered promising candidates for flexible modern electronic devices. ZnO–PVA polymer nanocomposites have gained recent research interest due to excellent optical and dielectric properties. Transition metals (Cr, Mn, Fe, Ni, Cu) oxide nanoparticles incorporated ZnO–PVA composite matrix are investigated in this work for a comprehensive study of its structure, morphology, optical and dielectric parameters. Crystallographic information revealed the presence of crystalline zinc oxide and transition metals oxides reflections in specific orientations in the PVA matrix. The inter-particle distance and interfacial interaction of transition metal oxide nanoparticles in host polymer are observed as important factors for improved dipole polarization. The nanoparticles of metal oxides in matrix induce the enhanced negative charge carriers and exhibit robust interactions with positive carriers of the polymer surface. A sharp and substantial increment in real dielectric permittivity from 74 for ZnO–PVA to maximum 350 for ZnO–PVA–Fe2O3 composition was observed by the addition of transition metal oxides in the PVA matrix with same loss factor value of 0.1.

Effect of gamma ray on some properties of bismuth borate glasses containing different transition metals

This work aims to study the influence of gamma irradiation on some bismuth borate glasses doped with different transition metal oxides (CuO, CoO, ZnO and CdO). The structure of the glass matrix was analyzed by Fourier transform infrared and ultraviolet–visible spectroscopy before and after gamma irradiation at doses of 1 kGy, 20 kGy and 50 kGy. Additionally, the attention is made in determining the attenuation parameters against gamma rays. Mass attenuation coefficient determined experimentally and calculated theoretically by WinXCom program, which is a significant program in the field of radiation shielding. It is found that the attenuation parameters of gamma ray have higher values of the sample without transition metal oxides and the other doped with CdO. From hardness measurements before and after irradiation, it was found that hardness increases with the addition of transition metal oxides to glass. The results of different techniques show that these glasses possess a slight effect on the network structure of the samples against gamma irradiation. So, it can be used in different applications of nuclear fields.

The Effect of Transition Metal Oxide Addition on the Conductivity of Commercially Available Gd-Doped Ceria

The effect of addition of transition metal oxides on the charge transport of commercially available Gd-doped ceria (Ce0.9Gd0.1O2−δ) was assessed with special emphasis on the electronic partial conductivity. The samples were doped by adding 2, 4 or 6 cat% of or or 2 mol% of the transition metal oxides V2O5, MnO2, and CuO, respectively. All samples with transition metal oxides showed predominant ionic conductivity at high temperatures and for all materials except for MnO2 addition, the electrical conductivity was slightly increased at temperatures ≤500 °C compared to pure CGO. For Co other than for Fe addition, the electronic conductivity strongly depends on the Co concentration. Also an increasing electronic conductivity with decreasing oxygen partial pressure from 10−8 to 10−4 bar at temperatures below 600 °C indicates the changing redox state of Co from divalent at low oxygen partial pressures to trivalent under ambient oxygen partial pressure. Additionally, it was found that 2 mol% of CuO already lead to a significantly decreased blocking effect of the grain boundaries in the temperature range below 500 °C.

Effect of catalysts on the burning rate of phase stabilized ammonium nitrate based composite propellants

The Ammonium Nitrate based composite propellants are widely used in the applications of tactical missiles and explosives due to its least toxicity and smokeless combustion. The main disadvantage of ammonium nitrate based propellants is its poor burning rate. Hence, it is required to enhance its burning rate for attaining a better performance. One of the several methods of upgrade the burning rate of composite solid propellants is the addition of catalysts to the propellant. The present study aims to investigate the effect of addition of transition metal oxides as the catalysts to the phase-stabilized ammonium nitrate based composite solid propellants and to study its thermal decomposition characteristics.

Assessment of the Effect of Transition Metal Oxide Addition on the Conductivity of Commercial Gd-Doped Ceria

The effect of addition of transition metal oxides on the charge transport of commercially available Gd-doped ceria (Ce0.9Gd0.1O2-δ) was assessed with special emphasis on the electronic partial conductivity. The samples were doped by adding 2, 4 or 6 cat% of CoO3/4 or FeO2/3, or 2 mol% of the transition metal oxides V2O5, MnO2, and CuO, respectively. It was found that even small amounts of transition metal oxides severely change the partial electronic conductivity of ceria while the majority oxygen ion conductivity was only mildly affected: for high oxygen ion conductivity, Fe or Mn oxide addition as well as small amounts of Co oxide are beneficial, as especially the grain boundary conductivity is slightly increased. Addition of V or Cu oxide in contrast increases the minority charge carrier conductivity of electrons and thus enhances the mixed ionic-electronic conductivity. For Co oxide addition, an increasing electronic conductivity with decreasing oxygen partial pressure from 10−8 to 10−4 bar at temperatures below 600°C indicates the changing redox state of Co from divalent at low oxygen partial pressures to trivalent under ambient oxygen partial pressure.

Grain-boundary states in solid oxide electrolyte ceramics processed using iron oxide sintering aids: a Mössbauer spectroscopy study

In order to appraise microstructure-determined defect formation processes and minor intergranular states in the solid electrolyte materials sintered employing transition metal oxide additives, the transmission Mossbauer spectroscopy analysis of Zr0.85Y0.15O2 − δ, Ce0.9Gd0.1O2 − δ, and (La0.9Sr0.1)0.98Ga0.8Mg0.2O3 − δ ceramics containing 2 mol% 57Fe isotope probe was combined with X-ray diffraction and scanning electron microscopy studies. The sintering aids tend to dissolve in yttria-stabilized zirconia and lanthanum gallate where Fe-rich domains, magnetically ordered at 4 K, co-exist with interfacial iron species remaining paramagnetic. For the electrolyte ceramics processed at 1373 K, this dissolution is accompanied with an appearance of insulating phase impurities, such as monoclinic zirconia. On the contrary, low iron solubility in gadolinia-doped ceria leads to the segregation of trace amounts of hematite and perovskite-type GdFeO3 phases, which enhance densification and affect p-type electronic transport. The iron cations incorporated into the fluorite-type cubic zirconia and ceria lattices are predominantly trivalent, with reduced oxygen coordination relative to the host cations, while the Fe4+ states prevailing in the gallate ceramics sintered in air exhibit atypical disproportionation into Fe3+ and Fe5+ even at room temperature.

A computational study of the addition of ReO3L (L=Cl(-), CH3, OCH3 and Cp) to ethenone.

The periselectivity and chemoselectivity of the addition of transition metal oxides of the type ReO3L (L = Cl, CH3, OCH3 and Cp) to ethenone have been explored at the MO6 and B3LYP/LACVP* levels of theory. The activation barriers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of ReO3L (L = Cl−, OCH3, CH3 and Cp) with ethenone, the concerted [2 + 2] addition of the metal oxide across the C=C and C=O double bond to form either metalla-2-oxetane-3-one or metalla-2,4-dioxolane is the most kinetically favored over the formation of metalla-2,5-dioxolane-3-one from the direct [3 + 2] addition pathway. The trends in activation and reaction energies for the formation of metalla-2-oxetane-3-one and metalla-2,4-dioxolane are Cp < Cl− < OCH3 < CH3 and Cp < OCH3 < CH3 < Cl− and for the reaction energies are Cp < OCH3 < Cl− < CH3 and Cp < CH3 < OCH3 < Cl CH3. The concerted [3 + 2] addition of the metal oxide across the C=C double of the ethenone to form species metalla-2,5-dioxolane-3-one is thermodynamically the most favored for the ligand L = Cp. The direct [2 + 2] addition pathways leading to the formations of metalla-2-oxetane-3-one and metalla-2,4-dioxolane is thermodynamically the most favored for the ligands L = OCH3 and Cl−. The difference between the calculated [2 + 2] activation barriers for the addition of the metal oxide LReO3 across the C=C and C=O functionalities of ethenone are small except for the case of L = Cl− and OCH3. The rearrangement of the metalla-2-oxetane-3-one–metalla-2,5-dioxolane-3-one even though feasible, are unfavorable due to high activation energies of their rate-determining steps. For the rearrangement of the metalla-2-oxetane-3-one to metalla-2,5-dioxolane-3-one, the trends in activation barriers is found to follow the order OCH3 < Cl− < CH3 < Cp. The trends in the activation energies for the most favorable [2 + 2] addition pathways for the LReO3–ethenone system is CH3 > CH3O− > Cl− > Cp. For the analogous ethylene–LReO3 system, the trends in activation and reaction energies for the most favorable [3 + 2] addition pathway is CH3 > CH3O− > Cl− > Cp [10]. Even though the most favored pathway in the ethylene-LReO3 system is the [3 + 2] addition pathway and that on the LReO3–ethenone is the [2 + 2] addition pathway, the trends in the activation energies for both pathways are the same, i.e. CH3 > CH3O− > Cl− > Cp. However, the trends in reaction energies are quite different due to different product stabilities. The formation of the acetic acid precursor through the direct addition pathways was unsuccessful for all the ligands studied. The formation of the acetic acid precursor through the cyclization of the metalla-2-oxetane-3-one is only possible for the ligands L = Cl−, CH3 whiles for the cyclization of metalla-2-oxetane-4-one to the acetic acid precursor is only possible for the ligand L = CH3. Although there are spin-crossover reaction observed for the ligands L = Cl−, CH3 and CH3O−, the reactions occurring on the single surfaces have been found to occur with lower energies than their spin-crossover counterparts.

Effect of Addition of Transition Metal Oxides on the Optical and Structural Properties of Phosphate Glasses

Effect of Addition of Transition Metal Oxides on the Optical and Structural Properties of Phosphate Glasses

Removal of ethylene from air stream by adsorption and plasma-catalytic oxidation using silver-based bimetallic catalysts supported on zeolite

Dynamic adsorption of ethylene on 13X zeolite-supported Ag and Ag–MxOy (M: Co, Cu, Mn, and Fe), and plasma-catalytic oxidation of the adsorbed ethylene were investigated. The experimental results showed that the incorporation of Ag into zeolite afforded a marked enhancement in the adsorptivity for ethylene. The addition of transition metal oxides was found to have a positive influence on the ethylene adsorption, except FexOy. The presence of the additional metal oxides, however, appeared to somewhat interrupt the diffusion of ozone into the zeolite micro-pores, leading to a decrease in the plasma-catalytic oxidation efficiency of the ethylene adsorbed there. Among the second additional metal oxides, FexOy was able to reduce the emission of ozone during the plasma-catalytic oxidation stage while keeping a high effectiveness for the oxidative removal of the adsorbed ethylene. The periodical treatment consisting of adsorption followed by plasma-catalytic oxidation may be a promising energy-efficient ethylene abatement method.

Doping with Metal and Compound to Improve the Properties of Hydrogen Storage of MgH&lt;sub&gt;2&lt;/sub&gt;

Recently, Magnesium hydride MgH2is one of the attractive hydrogen storage materials because it reaches a high hydrogen capacity. However, the reaction kinetics is too slow and needs high temperature for progressing hydrogen absorption and desorption reactions, which hinders the process of practical applications and it is necessary to improve the hydrogen storage propesties. In this paper, most used or under research methods (Doping with metal and compound) of improving on the hydrogen storage of magnesium hydride are reviewed, in particular to elements substitution, addition of transition metal oxides or fluorine and so on. The advantages and disadvantages of vaious methods of improving on the hydrogen storage of magnesium hydride are compared. The trend of the methods of improving is also introduced.

Effect of transition metal oxide additives on the activity of an Ag/SiO2 catalyst in carbon monoxide oxidation

The catalysts of silver supported on mesoporous silica modified with Co3O4, CeO2, and ZrO2 were prepared by an impregnation method; characterized by X-ray diffraction analysis, temperature-programmed reduction, and low-temperature nitrogen adsorption; and studied in a model reaction of CO oxidation. It was found that the Ag/SiO2 system exhibited high activity in the reaction of CO oxidation, and the addition of transition metal oxides led to reduction of the temperature of 50% CO conversion by 40°C. The modification of Ag/SiO2 with cerium dioxide was found most effective because of the interaction of silver particles and CeO2 on the surface of silica gel.

Physical and optical properties of Co2+, Ni2+ doped 20ZnO + xLi2O + (30 − x)K2O + 50B2O3 (5 ≤ x ≤ 25) glasses: Observation of mixed alkali effect

Co2+ and Ni2+ ions doped 20ZnO+xLi2O+(30−x)K2O+50B2O3 (5≤x≤25) mol% glasses are prepared using melt quenching technique. Structural changes of the prepared glasses by addition of transition metal oxides, CoO and NiO are investigated by UV–vis–NIR, FT-IR spectroscopy and XRD. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of the all glasses revealed that the network structure of the glasses are mainly based on BO3 and BO4 units placed in different structural groups in which the BO3 units being dominant. The optical absorption spectra suggest the site symmetry of Co2+ and Ni2+ ions in the glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. The optical band gap and Urbach energies exhibited the mixed alkali effect. Various physical parameters such as density, refractive index, optical dielectric constant, polaron radius, electronic polarizability and inter-ionic distance are also determined.

Characterization of Fe- and Mn-doped GDC for low-temperature processing of solid oxide fuel cells

This study reports the development of a low-temperature solid oxide fuel cell (SOFC) based on gadolinium-doped-ceria (Gd 0.1Ce 0.9O 1.95, GDC) electrolyte and copper anode. Single cells were fabricated by sintering of all three SOFC components – electrolyte, copper-based anode and composite cathode – in a single step at low temperature (900 °C). Low-temperature sintering was necessitated due to the low melting point of copper and was achieved by the addition of transition metal oxides (TMOs) (Fe and Mn) to the GDC electrolyte. The sinterability of TMO-doped GDC samples was evaluated over 900–1400 °C. Key functional properties – density, mechanical strength and electrical conductivity – of the doped GDC were determined. Acceptable levels of density (>95% of theoretical) and mechanical strength were achieved for the samples sintered at 900 °C. Scanning electron micrographs (SEMs) of the doped-GDC samples showed no open pores at the lowest sintering temperature of 900 °C. The electrical conductivities of the doped-GDC samples sintered at 900 °C at a test temperature of 650 °C were determined to be 0.0067 S cm −1 and 0.009 S cm −1 for Fe- and Mn-doped samples, respectively, but lower than that of undoped-GDC sintered at 1100 °C ( σ 650 °C = 0.027 S cm −1). Single cells were prepared by slurry painting of CuO–GDC anode on one side of TMO-doped GDC electrolyte and Gd 0.1Ce 0.9O 1.95 (GDC)–La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) composite cathode on the other side of the electrolyte followed by co-sintering of all the three layers at 900 °C. The performance of the single cells was evaluated over 650–700 °C using humidified hydrogen as fuel and air as oxidant.

Synthesis Gas Generation by Chemical-Looping Reforming Using Ce-Based Oxygen Carriers Modified with Fe, Cu, and Mn Oxides

Chemical-looping reforming (CLR) is a technology that can be used for partial oxidation and steam reforming of hydrocarbon fuels. It involves the use of a metal oxide as an oxygen carrier, which transfers oxygen from combustion air to the fuel. Composite oxygen carriers of cerium oxide added with Fe, Cu, and Mn oxides were prepared by co-precipitation and investigated in a thermogravimetric analyzer and a fixed-bed reactor using methane as fuel and air as oxidizing gas. It was revealed that the addition of transition-metal oxides into cerium oxide can improve the reactivity of the Ce-based oxygen carrier. The three kinds of mixed oxides showed high CO and H-2 selectivity at above 800 degrees C. As for the Ce-Fe-O oxygen carrier, methane was converted to synthesis gas at a H-2/CO molar ratio close to 2:1 at a temperature of 800-900 degrees C; however, the methane thermolysis reaction was found on Ce-Cu-O and Ce-Mn-O oxygen carriers at 850-900 degrees C. Among the three kinds of oxygen carriers, Ce-Fe-O presented the best performance for methane CLR. On Ce-Fe-O oxygen carriers, the CO and H-2 selectivity decreased as the Fe content increased in the carrier particles. An optimal range of the Ce/Fe molar ratio is Ce/Fe > 1 for Ce-Fe-O oxygen carriers. Scanning electron microscopy (SEM) analysis revealed that the microstructure of the Ce-Fe-O oxides was not dramatically changed before and after 20 cyclic reactions. A small amount of Fe3C was found in the reacted Ce-Fe-O oxides by X-ray diffraction (XRD) analysis.