摘要 :
A general microwave synthesis method was developed to synthesize cerium orthovanadate (CeVO_4) nanostructures without the use of any catalysts or templates. This method is able to control the shape and size of the products by adju...
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A general microwave synthesis method was developed to synthesize cerium orthovanadate (CeVO_4) nanostructures without the use of any catalysts or templates. This method is able to control the shape and size of the products by adjusting the pH of precursor solutions to be 1-10. Phase, purity, and different morphologies of the products were characterized by XRD, FTIR, SEM, and TEM.They showed that the as-synthesized products exhibited pure single crystalline CeVO4 with tetragonal structure. Their morphologies developed in sequence as nanoparticles (pH = 4-10), nanorods (pH = 2, 3), and microflowers (pH = 1). UVvisible spectra were used to estimate the direct energy gaps of CeVO_4 nanorods and microflowers: 3.77 and 3.65 eV, respectively. Photoluminescence (PL) of CeVO_4 microflowers showed strong emission intensities at 578 nm. These results were in the range of possible application for photocatalysis, investigated by studying the degradation of methylene blue.
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Size-controlled CeVO_4 nanoparticles have been synthesized by a simple microwave iradiation processing.The products were characterized by X-ray diffraction,transmission electron microscopy,and UV-Vis spectroscopy.the results showe...
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Size-controlled CeVO_4 nanoparticles have been synthesized by a simple microwave iradiation processing.The products were characterized by X-ray diffraction,transmission electron microscopy,and UV-Vis spectroscopy.the results showed that the size of as-synthesized CeVO_4 powderswas in the range of 6-18nm and was extremely dependent on the solution pH value.The optical absorption measurements displayed the obvious quantum-size effect of the products.
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The present work deals with precipitation followed by the hydrothermal method
for the synthesis of cerium vanadate decorated nitrogen doped reduced graphene
oxide (CeV/NRGO) nanocomposite. The crystallographic and Raman spectros...
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The present work deals with precipitation followed by the hydrothermal method
for the synthesis of cerium vanadate decorated nitrogen doped reduced graphene
oxide (CeV/NRGO) nanocomposite. The crystallographic and Raman spectroscopic
characterization confirm the formation of CeV/NRGO nanocomposite.
A computational study on crystal structure using Material Studio, confirms the
presence of zircon-like CeV with VO_4 tetrahedra sharing corners and edges with
CeO_8 dodecahedra in CeV/NRGO nanocomposite. X-ray photoelectron spectroscopic
(XPS) analysis supports the presence of Ce in +3 and +4 oxidation
state. The optical characterization shows the decreased bandgap in CeV/NRGO
nanocomposite (2.03 eV) compared to pristine CeV (2.35 eV). Enhanced photocatalytic
activity is observed towards hydrogen evolution in CeV/NRGO
(15 124 μmol) compared to CeV (7215 μmol) and NRGO (2034 μmol). In addition,
CeV/NRGO, CeV, and NRGO are evaluated for degradation of Alizarin Yellow
(AY) and Orange G (OG) dyes in presence of visible light. CeV/NRGO managed
to degrade 97% and 94% of AY and OG, respectively in 80 min. The electron spin
resonance (ESR) studies show superoxide radicals and hydroxyl ions are the
active species responsible for photocatalytic reactions. Based on the liquid
chromatography-mass spectroscopy (LC-MS) results, a possible photocatalytic
mechanism has been discussed. The good stability and reusability of CeV/NRGO
nanocomposite could be a choice of material for energy and environmental
related research.
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The structural, elastic, magnetic, and electronic properties of the tetragonal zircon-type CeVO_4 are investigated with first-principles method. We use the local density approximation (LDA), generalized gradient approximation (GGA...
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The structural, elastic, magnetic, and electronic properties of the tetragonal zircon-type CeVO_4 are investigated with first-principles method. We use the local density approximation (LDA), generalized gradient approximation (GGA), LDA + U, and GGA + U methods to find the most stable structure of the zircon-type CeVO_4. By employing pure density functional theory (DFT), we obtain a ferromagnetic (FM) metallic ground state, which is in disagreement with experiments; While LDA + U (U = 6 eV) can give an antiferromagnetic (AFM) insulating ground state for CeVO_4, according well with the experimental finding. For the AFM CeVO_4, LDA + U calculation gives a band gap of 2.957 eV and a magnetic moment of 1.03 μ_B per Ce atom, which are in good accordance with the experimental results. In addition, the elasticity-related properties, such as the elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Debye temperature, are also systematically investigated. The calculated bulk modulus of CeVO_4 is 100.6 GPa, which agrees with the experimental result of 112 GPa. The partial density of states (PDOS) and Mulliken populations are also analyzed.
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Selective oxidation of H_2S to elemental sulfur was investigated in a fixed bed reactor using Ce-V mixed oxides and cerium oxide (CeO_2) catalytic materials prepared by the complexation technique.The Ce-V mixed oxide with a V/Ce a...
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Selective oxidation of H_2S to elemental sulfur was investigated in a fixed bed reactor using Ce-V mixed oxides and cerium oxide (CeO_2) catalytic materials prepared by the complexation technique.The Ce-V mixed oxide with a V/Ce atomic ratio of one and with the CeVO_4 crystal structure gave very high sulfur selectivity values (close to one) at almost complete conversion of H_2S,for O_2/H_2S mole ratios close to 0.5.Best operation temperature was found as 250 deg C with this catalyst.CeO_2 gave lower selectivities,causing the formation of some SO_2,even at sub-stoichiometric O_2/H_2S feed ratios.It also showed a fast deactivation due to the partial sulfidation of the catalyst surface during the reaction.XPS analysis of the fresh and the used catalysts containing different V/Ce ratios strongly indicated that the selective oxidation of H_2S to elemental sulfur over the Ce-V mixed oxides involved a redox cycle of cerium,rather than a redox cycle of vanadium.
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In this paper, CeVO_4 micro/nano hollow spheres (CVO-HS) composed of closely packed nanoparticles are prepared via a facile critic acid-assisted hydrothermal method. The crystalline phase, composition, structure and morphology of ...
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In this paper, CeVO_4 micro/nano hollow spheres (CVO-HS) composed of closely packed nanoparticles are prepared via a facile critic acid-assisted hydrothermal method. The crystalline phase, composition, structure and morphology of the obtained samples are characterized by several techniques. The formation mechanism of the final hollow structure with an inside-out Ostwald ripening process is also suggested. When tested as anode material for lithium-ion batteries (LIBs) at a current density of 0.1 A g~(-1) in 0.01-3.0 V, a stable discharge capacity of 367.4 mAh g~(-1) is achieved after 100 cycles, while only 187 mAh g~(-1) for CeVO_4 nanoparticles (CVO-NP). The excellent electrochemical performances of CVO-HS are mainly ascribed to the short distance in the nanoparticle subunits for lithium ions/electron diffusions and the inner hollow space for buffering the volume change. Hence, the CVO-HS might be considered as a good host material for next LIBs.
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In this paper, with the aim of improving hydrogen storage efficiency, cerium vanadate/reduced graphene oxide (CeVO_4/ rGO) nanocomposite was synthesized through a one-step hydrothermal method due to its unique characteristics, inc...
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In this paper, with the aim of improving hydrogen storage efficiency, cerium vanadate/reduced graphene oxide (CeVO_4/ rGO) nanocomposite was synthesized through a one-step hydrothermal method due to its unique characteristics, including suitable electrochemical behavior, high specific surface area, and high porosity. In addition to controlling the growth of CeVO_4 nanoparticles, hydrazine reduces graphene oxide (GO) to reduced graphene oxide (rGO) and enables one-step synthesis. FESEM images showed that the rod-like CeVO_4 nanoparticles were dispersed on the graphene plates. According to the obtained storage results, with the addition of graphene, the synergistic effect between the layers has increased and, as a result, the hydrogen storage capacity has increased. The highest amount of electrochemical storage of hydrogen in the synthesized nanocomposite was about 5430 mAh/g, which is a significant result compared to other nanostructures used.
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Rice husk silica was utilized as the promoter of ceria for preparing supported vanadia catalysts.Effect of vanadium content was investigated with 2-10 wt.% V_2O_5 loading over the support.Structural characterization of the catalys...
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Rice husk silica was utilized as the promoter of ceria for preparing supported vanadia catalysts.Effect of vanadium content was investigated with 2-10 wt.% V_2O_5 loading over the support.Structural characterization of the catalysts was done by various techniques like energy dispersive X-ray (EDX),X-ray diffraction (XRD),BET surface area,thermal analysis (TGA/DTA),FT-infrared spectroscopy (FT-IR),UV-vis diffused reflectance spectroscopy (DR UV-vis),electron paramagnetic spectroscopy (EPR)and solid state magnetic resonance spectroscopies (~(29)Si and ~(51)V MASNMR).Catalytic activity was studied towards liquid-phase oxidation of benzene.Surface area of ceria enhanced upon rice husk silica promotion,thus makes dispersion of the active sites of vanadia easier.Highly dispersed vanadia was found for low V_2O_5 loading and formation of cerium orthovanadate (CeVO_4)occurs as the loading increases.Spectroscopic investigation clearly confirms the formation of CeVO_4 phase at higher loadings of V_2O_5.The oxidation activity increases with vanadia loading up to 8 wt.% V_2O_5,and further increase reduces the conversion rate.Selective formation of phenol can be attributed to the presence of highly dispersed active sites of vanadia over the support.
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Vanadia/ceria catalysts(2-10 wt% of V_2O_5)were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution.Structural characterization was done with energy dispersive X-ray analysis(EDX),powder X-ray diffraction...
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Vanadia/ceria catalysts(2-10 wt% of V_2O_5)were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution.Structural characterization was done with energy dispersive X-ray analysis(EDX),powder X-ray diffraction(XRD),BET surface area measurements,FT-IR spectroscopy and nuclear magnetic spectral analysis(~(51)V MASNMR).XRD and ~(51)V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO_4 phase at higher V_2O_5 loading.The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H_2O_2 as oxidant.The oxidation activity is increased with loading up to 8 wt% V_2O_5 and then decreased with further increase in V_2O_5 content to 10 wt%.Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation.The CeVO_4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
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A simple method was proposed for the preparation of CeVO_4. The as-synthesized CeVO_4 was, for the first time, demonstrated to exhibit both peroxidase-like and oxidase-like activity, which catalyzes the oxidation of 3, 3', 5, 5'-t...
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A simple method was proposed for the preparation of CeVO_4. The as-synthesized CeVO_4 was, for the first time, demonstrated to exhibit both peroxidase-like and oxidase-like activity, which catalyzes the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to form a typical blue solution in the presence or absence of H_2O_2. Moreover, the mechanism of its dual-enzyme activity was investigated in detail. The Michaelis constant (K_m) value for CeVO_4 (0.136mM) was lower than that of horseradish peroxidase (0.424mM) with TMB as the substrate. Interestingly, hydroquinone (H_2Q), dihydroxybenzene isomer, undergoes reduction accompanying the oxidation of TMB by the CeVO_4 oxidase mimic along with a visible color change, while the other two dihydroxybenzene isomers, i.e., resorcinol (RC) and catechol (CC), do not. Based on these findings, a colorimetric platform was developed to discriminate H_2Q from RC and CC. Under optimal conditions, a linear relationship between the H_2Q concentration and absorbance was observed from 0.05 to 8 μM, and a limit of detection of 0.04 μM was achieved. Moreover, this colorimetric platform can selectively reveal H_2Q concentrations in the presence of other dihydroxybenzene isomers.
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