A novel transition metal ion bridging bis(diphosphopentamolybdates) has been synthesized and characterized by elemental analysis,IR spectrum,UV spectrum and single-crystal X-ray diffraction.The single-crystal struct...A novel transition metal ion bridging bis(diphosphopentamolybdates) has been synthesized and characterized by elemental analysis,IR spectrum,UV spectrum and single-crystal X-ray diffraction.The single-crystal structure analysis shows that the compound consists of seven charge-compensating 2,2'-biimidazole cations (BIIM=2,2'-biimidazole) and one dumbbell-like [Mn(H2O)4(P2Mo5O23)2]10-heteropolyanion which is constructed by two [P2Mo5O23]6-clusters bridged through one [Mn(H2O)4]2+ cation.展开更多
Two new polyoxomolybdate compounds,namely CuII2(HL)3]2[Mo8O26]·(H2O)4(1) and [NiII(HL)3]2(Mo8O26)·(H2O)3(2)(HL = 3-(2-pyridyl)pyrazole),were designed and synthesized under hydrothermal cond...Two new polyoxomolybdate compounds,namely CuII2(HL)3]2[Mo8O26]·(H2O)4(1) and [NiII(HL)3]2(Mo8O26)·(H2O)3(2)(HL = 3-(2-pyridyl)pyrazole),were designed and synthesized under hydrothermal conditions.X-ray diffraction analyses reveal that compound 1 consists of one β-Mo8O264-cluster and a Cu2 dimer which is built from two Cu(II) ions linked by three 3-(2-pyridyl)pyrazole ligands.Compound 2 is generated by two kinds of polyoxomolybdate clusters of α-[Mo8O26]4-and β-[Mo8O26]4-.In complexes 1 and 2,the multi-dimensional frameworks are con-structed with the help of hydrogen-bonding links between the terminaloxygen atoms of [Mo8O26]4-,water molecules,and 3-(2-pyridyl)pyrazole ligands.Crystal data of 1:C24H25Cu2Mo4N9O15,Mr = 1190.37,monoclinic,space group P21/c,a = 10.850(2),b = 18.510(4),c = 17.230(3) ,β = 100.57(3)°,V = 3401.6(12) 3,Z = 4,Dc = 2.324 g/cm3,F(000) = 2312,μ = 2.742 mm-1,R = 0.0302 and wR = 0.0775(Ⅰ 〉 2σ(Ⅰ));Crystal data for 2:C48H48Mo8N18Ni2O29,Mr = 2225.98,monoclinic,space group P21/n,a = 20.799(2),b = 14.7970(13),c = 23.141(2) ,β = 91.6180(10)°,V = 7119.0(11) 3,Z = 4,Dc = 2.077 g/cm3,F(000) = 4344,μ = 1.968 mm-1,R = 0.0309 and wR = 0.0696(Ⅰ〉 2σ(Ⅰ)).展开更多
Ar<sup>+</sup> ion bombardment induced reduction effect on Bi<sub>2</sub>O<sub>3</sub>, MoO<sub>3</sub> and Bi-Mo complex oxides, α-Bi<sub>2</sub>Mo<sub&...Ar<sup>+</sup> ion bombardment induced reduction effect on Bi<sub>2</sub>O<sub>3</sub>, MoO<sub>3</sub> and Bi-Mo complex oxides, α-Bi<sub>2</sub>Mo<sub>3</sub>O<sub>13</sub>, β-Bi<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>, and γ-Bi<sub>2</sub>MoO<sub>6</sub>, has been studied with XPS. The results show that, owing to the presence of the oxygen anion bridge in Bi(Ⅲ)-O(Ⅱ)-Mo(Ⅵ), the reduction behavior of Bi(Ⅲ) and Mo(Ⅵ) metal ions in all the three complex oxides is contrary to that in the single oxides. While Mo(Ⅵ) in MoO<sub>3</sub> is reduced to Mo(Ⅵ) in UHV under Ar<sup>+</sup> ion bombardment, the valence state of Bi(Ⅲ) in Bi<sub>2</sub>O<sub>3</sub> is unchanged. However, Bi(Ⅲ) in the three complex oxides is reduced to Bi(0) without noticeable reduction of Mo(Ⅵ). Nevertheless, the rates of Bi(Ⅲ) reduction are in correspondence with the difference in Bi/Mo atomic ratio and the crystallographic features of the three phases of bismuth molybdate are decreasing in the order of α-Bi<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub>≥β-Bi<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>】γ-Bi<sub>2</sub>MoO<sub>6</sub>. A new O -species is observed on the bismuth molybdate surface reduced by Ar<sup>+</sup> ion bombardment.Wc discuss the above phenomena展开更多
Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work,...Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work, a series of visible-light-driven Y^(3+)-doped BMO(Y-BMO) photocatalysts were synthesized via a hydrothermal method. Degradation experiments on Rhodamine B and Congo red organic pollutants revealed that the optimal degradation rates of Y-BMO were 4.3 and 5.3 times those of pure BMO, respectively. The degradation efficiency of Y-BMO did not significantly decrease after four cycle experiments. As a result of Y^(3+)doping, the crystal structure of BMO changed from a thick layer structure to a thin flower-like structure with an increased specific surface area. X-ray photoelectron spectroscopy showed the presence of highintensity peaks for the O 1s orbital at 531.01 and 530.06 eV, confirming the formation of oxygen vacancies in Y-BMO. Photoluminescence(PL) and electrochemical impedance spectroscopy measurements revealed that the PL intensity and interface resistances of composites decreased significantly, indicating reduced electron–hole pair recombination. This work provides an effective way to prepare high-efficiency Bibased photocatalysts by doping rare earth metal ions for improved photocatalytic performance.展开更多
CO_(2)hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes,as well as to produce valuable chemicals from renewable and abundant resources.Iron catalysts are commonly...CO_(2)hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes,as well as to produce valuable chemicals from renewable and abundant resources.Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons.Iron-molybdenum catalysts have found numerous applications in catalysis,but have been never evaluated in the CO_(2)hydrogenation.In this work,the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal(Li,Na,K,Rb,or Cs)were characterized using X-ray diffraction,hydrogen temperatureprogrammed reduction,CO_(2)temperature-programmed desorption,in-situ^(57)Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy.Their catalytic performance was evaluated in the CO_(2)hydrogenation.During the reaction conditions,the catalysts undergo the formation of an iron(Ⅱ)molybdate structure,accompanied by a partial reduction of molybdenum and carbidization of iron.The rate of CO_(2)conversion and product selectivity strongly depend on the promoting alkali metals,and electronegativity was identified as an important factor affecting the catalytic performance.Higher CO_(2)conversion rates were observed with the promoters having higher electronegativity,while low electronegativity of alkali metals favors higher light olefin selectivity.展开更多
The supercapacitor electrode materials suffer from structure pulverization and sluggish electrode kinetics under high current rates.Herein,a unique NiMoO_(4)@Co-B heterostructure composed of highly conductive Co-B nan...The supercapacitor electrode materials suffer from structure pulverization and sluggish electrode kinetics under high current rates.Herein,a unique NiMoO_(4)@Co-B heterostructure composed of highly conductive Co-B nanoflakes and a semiconductive NiMoO_(4) nanorod is designed as an electrode material to exert the energy storage effect on supercapacitors.The formed Mott-Schottky heterostructure is helpful to overcome the ion diffusion barrier and charge transfer resistance during charging and discharging.Moreover,this crystalline-amorphous heterogeneous phase could provide additional ion storage sites and better strain adaptability.Remarkably,the optimized NiMoO_(4)@Co-B hierarchical nanorods(the mass ratio of NiMoO_(4)/Co-B is 3:1)present greatly enhanced electrochemical characteristics compared with other components,and show superior specific capacity of 236.2 mA h g^(-1)at the current density of 0.5 A g^(-1),as well as remarked rate capability.The present work broadens the horizons of advanced electrode design with distinct heterogeneous interface in other energy storage and conversion field.展开更多
A new series of solid solutions Lu2W3-xMoxO12 (0.5≤r≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperat...A new series of solid solutions Lu2W3-xMoxO12 (0.5≤r≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth ttmgstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients (TEC) of Lu2W3_xMoxO12 are determined as -20.0× 10^-6 K^-1 for x=0.5 and -16.1×10^-6 K^-1 for x=2.5 but -18.6× 10^-6 and -16.9× 10^-6K^-1 for unsubstituted Lu2W3012 and Lu2M03012 in the identical temperature range of 200 to 800℃. High-temperature X-ray diffraction (XRD) data and bond length analysis suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.展开更多
A simple way to prepare α- and β-CoMoO4 nanorods is reported in this paper. CoMoO4xH2O nanorod precursors were obtained using the microwave-assisted hydrothermal (MAH) method. By annealing the as-prepared CoMoO44xH2...A simple way to prepare α- and β-CoMoO4 nanorods is reported in this paper. CoMoO4xH2O nanorod precursors were obtained using the microwave-assisted hydrothermal (MAH) method. By annealing the as-prepared CoMoO44xH2O precursor at 600℃ for 10 min in a domestic microwave oven, α- and β-CoMoO4 nanorods were prepared. These powders were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform Raman microscopy and ultraviolet visible absorption spectroscopy (UV-vis spectra) as well as photoluminescence (PL) measurements. Based on the results, these materials revealed nanorod morphology. PL spectra obtained at room temperature for α- and β-CoMoO4 particles exhibited maximum components around the blue light emission. The results show that the domestic microwave oven has been successfully employed to obtain α- and β-CoMoO4 nanoparticles.展开更多
The Eu^3+:BaMoO4 nanostructures were synthesized by a simple hydrothermal method,and characterized by XRD,transmission electron microscopy,high-resolution transmission electron microscopy,excitation and emission spe...The Eu^3+:BaMoO4 nanostructures were synthesized by a simple hydrothermal method,and characterized by XRD,transmission electron microscopy,high-resolution transmission electron microscopy,excitation and emission spectra. Eu^3+:BaMoO4 nanostructures show a lotus leaf-shaped morphology,and exhibit a strong red emission at 612 nm,which may afford an opportunity for the development of other nanostructure materials.展开更多
Solid-state reaction of praseodymium (III) oxide,K2CO3 and MoO3 at high temperature leads to a potassium lanthanide double molybdate,namely,KPr(MoO4)2. The structural and optical properties of the title compound h...Solid-state reaction of praseodymium (III) oxide,K2CO3 and MoO3 at high temperature leads to a potassium lanthanide double molybdate,namely,KPr(MoO4)2. The structural and optical properties of the title compound have been investigated by means of single-crystal X-ray diffraction and spectroscopic measurements at room temperature. KPr(MoO4)2 crystallizes in tetragonal,space group I41/a with a = 5.401(3),c = 12.044(10),Z = 2 and R (I 〉 2σ(I)) = 0.0416. It features the famous scheelite-type structure (CaWO4),which can be thought as the substitution of two Ca^2+ ions in CaWO4 by a couple of K^+ and Pr^3+ ions in a statistical manner,and W^6+ by Mo^6+ cations.展开更多
This article investigated molybdenum recovery from oxygen pressure water leaching residue of Ni-Mo ore using alkaline leaching, followed by chemical treatment of leach liquor. Parameters affecting Mo leaching rate, su...This article investigated molybdenum recovery from oxygen pressure water leaching residue of Ni-Mo ore using alkaline leaching, followed by chemical treatment of leach liquor. Parameters affecting Mo leaching rate, such as sodium hydroxide concentration, reaction time, a liquid- to-solid ratio, and temperature for the preliminary alkaline leaching were experimentally determined. The results showed that more than 88 % of molybdenum was leached under the optimum conditions (2.5 ml.g-1 NaOH, 80 ℃, a liquid to solid ratio 3 ml.g-1, and reaction time 3 h). After the purification of leach liquor, a CaMoO4 product of 99.2 % purity could be obtained by CaCla precipitation method. The whole Mo recovery reached about 82.7 %.展开更多
Trivalent samarium ion (Sm^(3+)) activated calcium molybdate (CaMoO_4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO_4∶Sm shows that the CaMoO_4∶Sm single phase is develop...Trivalent samarium ion (Sm^(3+)) activated calcium molybdate (CaMoO_4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO_4∶Sm shows that the CaMoO_4∶Sm single phase is developed fully through our preparation procedure. The excitation spectrum of CaMoO_4∶Sm is composed of a broad absorption of host and some sharp lines of the f-f transition absorption of Sm^(3+). Illustrated in photoluminescence spectrum, CaMoO_4 doped with Sm^(3+) displays orange red emission that is ascribed to the inner 4f^5 electron transitions ~6H_(7/2)(orange)and ~6H_(9/2)(red)of Sm^(3+). Different from the sites of Sm^(3+) in CdWO_4, the Sm^(3+) ions substitute for the Ca^(2+) and form only one type emission center in the CaMoO_4 crystal lattice.展开更多
In order to effectively improve the corrosion resistance of aluminum alloys, anodic oxidation technique was used to generate the oxide film. We investigated the influences of two inorganic corrosion inhibitors(ammoniu...In order to effectively improve the corrosion resistance of aluminum alloys, anodic oxidation technique was used to generate the oxide film. We investigated the influences of two inorganic corrosion inhibitors(ammonium dihydrogen phosphate and sodium molybdate) on the corrosion resistance of anodic oxidation films on 2024 aluminum alloy, and studied the synergistic effect of two corrosion inhibitors. The corrosion resistance of anodic oxidation film in 3.5 wt% NaCl solution was evaluated by electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization curves. Results show that, after adding the single ammonium dihydrogen phosphate or sodium molybdate of 0.01 M to oxalic acid electrolyte, inhibition efficiencies of the anodized samples are 10% and 47%, respectively. However, in the presence of two inhibitors with the same concentration of 0.01 M, inhibition efficiency can be as high as 92%. Therefore, we observed the significantly synergistic corrosion inhibition effect of molybdate and phosphate ions for anodic oxidation film formed on 2024 aluminum alloy.展开更多
In order to prepare fluorescent material for white Light Emitting Diodes (LEDs), a new Eu^3+ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction (XRD) showed that the dop...In order to prepare fluorescent material for white Light Emitting Diodes (LEDs), a new Eu^3+ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction (XRD) showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3+ concentration on the luminescent properties of Eu^3+ doped SrMoO4 was investigated and the 25% (mole fraction) was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.展开更多
In this work, both the thermal expansion and electrical conductivity of nanocrystalline La2Mo2O9 were studied.The nanocrystalline powder of La2Mo2O9 was obtained by sol-gel method, and with the help of SHP (superhigh ...In this work, both the thermal expansion and electrical conductivity of nanocrystalline La2Mo2O9 were studied.The nanocrystalline powder of La2Mo2O9 was obtained by sol-gel method, and with the help of SHP (superhigh pressure)up to 4.5 × 104 atm at 700 ℃ for a short time, and the nanocrystalline powder was densified without obvious particle size growth. The electrical conductivity of nanocrystalline La2Mo2O9 was one orderof magnitude lower than that of the microcrystalline sample at the same temperature. Owing to the phase transition, the microcrystalline La2Mo2O9 has an abrupt increase of thermal expansion with a peak value of 48 × 10-6 K-1 at 556 ℃. For the nanocrystalline material, the peak value increases to 112 × 10-6 K-1 at 520 ℃. On the other hand, above 600 ℃ the significant growth of particle size of the nanocrystalline La2Mo2O9 was observed, accompanying by a tremendous increase of thermal expansion with a peak value of third higher than that of La2Mo2O9.展开更多
One novel polyoxometalate compound connected via trivalent cerium cation as bridge H2{ [K(H2O)212[Ce(H2O)5]2(H2Mo1.16W10.84O42)}.8H2O 1 was designed and synthesized in aqueous solution. X-ray diffraction analysi...One novel polyoxometalate compound connected via trivalent cerium cation as bridge H2{ [K(H2O)212[Ce(H2O)5]2(H2Mo1.16W10.84O42)}.8H2O 1 was designed and synthesized in aqueous solution. X-ray diffraction analysis reveals that the structure of 1 is a three-dimensional framework assembled from the arrangement of H2Mo1.16W10.84O42 (named paradodecmetalate-B) and Ce(H2O)5^3+ containing two planes, which are constructed through the unification of H2Mo1.16W10.84O42^10- and Ce(H2O)5^3+ along the [100] and [001] directions. Crystal data: H96Ce4KaMo2.32O128W21.68, Mr = 7074.89, monoclinic, P21/n, a = 12.5037(17), b = 17.002(2), c = 12.7473(17)A, β = 105.966(2)°, V = 2605.4(6)A^3, Z = 1, Dc = 4.509 g/cm^3, F(000) = 3132,μ = 26.098 mm^-1, R = 0.0377 and wR = 0.0789 (I 〉 2σ(I)).展开更多
The purpose of this work was to enhance the corrosion resistance of the passive fi lm on 304 stainless steel(SS)by chemical modifi cation in alkaline phosphate–molybdate solutions.The 304 SS was passivated in both ph...The purpose of this work was to enhance the corrosion resistance of the passive fi lm on 304 stainless steel(SS)by chemical modifi cation in alkaline phosphate–molybdate solutions.The 304 SS was passivated in both phosphate and phosphate–molybdate mixed solutions to investigate the eff ect of molybdate on its corrosion resistance.The experimental results indicated that the passive fi lm showed better corrosion resistance in Cl?-containing solutions after modifi cation in phosphate–molybdate solutions than in phosphate-only solutions.Energy-dispersive spectroscopy analyses revealed that the passive fi lm formed in phosphate–molybdate solutions contained Mo and P after modifi cation,which is the reason for the enhanced corrosion resistance.展开更多
This study was conducted to comprehensively evaluate the effects of salicylic acid and sodium molybdate on cold tolerance of an ornamental plant Bougainvillea glabra and to provide a theoretical guidance for landscape...This study was conducted to comprehensively evaluate the effects of salicylic acid and sodium molybdate on cold tolerance of an ornamental plant Bougainvillea glabra and to provide a theoretical guidance for landscape maintenance.B.glabra plants were treated with 0.5 mmol/L salicylic acid and 2.0 μmol/L alone or in combination,and then exposed to low temperature stress before physiological indices were measured.The results showed that all salicylic acid and sodium molybdate treatments reduced the relative conductivity and malondialdehyde( MDA) content of B.glabra to varying extents under the stress of low temperature,and more significant effect was achieved by using the two agents in combination.Oxygen free radicals production rate increased with decreasing temperature from 20 to 6 ℃,but declined with temperature decreasing from 3 to-3 ℃.The SOD activity of the control( CK) was significantly lower than that of other treatments at 0 and-3 ℃.The treatments with salicylic acid and sodium molybdate alone and in combination increased POD activity of B.glabra plants,especially at 0 ℃,as the POD activity of treatments T1,T2 and T3 was significantly higher than that of CK at 0 ℃.In addition,under low temperature stress,the contents of soluble sugar,starch and proline increased initially and decreased subsequently with temperature decreasing.The soluble sugar content at 3 ℃,starch and proline contents at 0 and-3 ℃ in treatments with salicylic acid and sodium molybdate alone and in combination were significantly higher than those of CK.All above results proved that salicylic acid and sodium molybdate are able to improve cold tolerance of B.glabra,and better effect can be achieved by using them together.展开更多
Er3+/Yb3+ co-doped Li3Ba2Gd3(MoO4)8 phosphors were synthesized by conven- tional solid state reaction method, and their structure and spectral properties were investigated. The diffuse reflectance spectra showed t...Er3+/Yb3+ co-doped Li3Ba2Gd3(MoO4)8 phosphors were synthesized by conven- tional solid state reaction method, and their structure and spectral properties were investigated. The diffuse reflectance spectra showed that the 4I15/2→4I11/2 transition of Er3+ and the 2F7/2→2F5/2 transition of Yb3+ ions were highly overlapped. Under the excitation of 980 nm, three up-conver- sion (UC) luminescence bands around 530, 555 and 660 nm were observed, corresponding to the 2H11/2→ 4I15/2, 4S3/2 → 4I15/2 and 4F9/2-→4I15/2 transitions of Er3+ ions, respectively. The effects of the concentration and pumping power on the UC intensities of Li3Ba2Gd3(MoO4)8:Er3+/yb3+ phosphors were investigated, and the possible UC mechanism was proposed based on the results.展开更多
基金Supported by the Natural Science Foundation of Henan Province (No. 0611011900)
文摘A novel transition metal ion bridging bis(diphosphopentamolybdates) has been synthesized and characterized by elemental analysis,IR spectrum,UV spectrum and single-crystal X-ray diffraction.The single-crystal structure analysis shows that the compound consists of seven charge-compensating 2,2'-biimidazole cations (BIIM=2,2'-biimidazole) and one dumbbell-like [Mn(H2O)4(P2Mo5O23)2]10-heteropolyanion which is constructed by two [P2Mo5O23]6-clusters bridged through one [Mn(H2O)4]2+ cation.
基金Supported by the 973 Key Program of the MOST (2006CB932904,2007CB815304)the National Natural Science Foundation of China (20873150,20821061,and 50772113)+2 种基金the Chinese Academy of Sciences (KJCX2-YW-M05)the Chinese Academy of Sciences (''Hundred Talents Program'') Ministry of Science and Technology of China (Project of ''973'' plan,No. 2007CB607606),and Shandong Provincial Education Department and Qilu Normal University
文摘Two new polyoxomolybdate compounds,namely CuII2(HL)3]2[Mo8O26]·(H2O)4(1) and [NiII(HL)3]2(Mo8O26)·(H2O)3(2)(HL = 3-(2-pyridyl)pyrazole),were designed and synthesized under hydrothermal conditions.X-ray diffraction analyses reveal that compound 1 consists of one β-Mo8O264-cluster and a Cu2 dimer which is built from two Cu(II) ions linked by three 3-(2-pyridyl)pyrazole ligands.Compound 2 is generated by two kinds of polyoxomolybdate clusters of α-[Mo8O26]4-and β-[Mo8O26]4-.In complexes 1 and 2,the multi-dimensional frameworks are con-structed with the help of hydrogen-bonding links between the terminaloxygen atoms of [Mo8O26]4-,water molecules,and 3-(2-pyridyl)pyrazole ligands.Crystal data of 1:C24H25Cu2Mo4N9O15,Mr = 1190.37,monoclinic,space group P21/c,a = 10.850(2),b = 18.510(4),c = 17.230(3) ,β = 100.57(3)°,V = 3401.6(12) 3,Z = 4,Dc = 2.324 g/cm3,F(000) = 2312,μ = 2.742 mm-1,R = 0.0302 and wR = 0.0775(Ⅰ 〉 2σ(Ⅰ));Crystal data for 2:C48H48Mo8N18Ni2O29,Mr = 2225.98,monoclinic,space group P21/n,a = 20.799(2),b = 14.7970(13),c = 23.141(2) ,β = 91.6180(10)°,V = 7119.0(11) 3,Z = 4,Dc = 2.077 g/cm3,F(000) = 4344,μ = 1.968 mm-1,R = 0.0309 and wR = 0.0696(Ⅰ〉 2σ(Ⅰ)).
基金Project supported by the National Natural Science Foundation of China
文摘Ar<sup>+</sup> ion bombardment induced reduction effect on Bi<sub>2</sub>O<sub>3</sub>, MoO<sub>3</sub> and Bi-Mo complex oxides, α-Bi<sub>2</sub>Mo<sub>3</sub>O<sub>13</sub>, β-Bi<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>, and γ-Bi<sub>2</sub>MoO<sub>6</sub>, has been studied with XPS. The results show that, owing to the presence of the oxygen anion bridge in Bi(Ⅲ)-O(Ⅱ)-Mo(Ⅵ), the reduction behavior of Bi(Ⅲ) and Mo(Ⅵ) metal ions in all the three complex oxides is contrary to that in the single oxides. While Mo(Ⅵ) in MoO<sub>3</sub> is reduced to Mo(Ⅵ) in UHV under Ar<sup>+</sup> ion bombardment, the valence state of Bi(Ⅲ) in Bi<sub>2</sub>O<sub>3</sub> is unchanged. However, Bi(Ⅲ) in the three complex oxides is reduced to Bi(0) without noticeable reduction of Mo(Ⅵ). Nevertheless, the rates of Bi(Ⅲ) reduction are in correspondence with the difference in Bi/Mo atomic ratio and the crystallographic features of the three phases of bismuth molybdate are decreasing in the order of α-Bi<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub>≥β-Bi<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>】γ-Bi<sub>2</sub>MoO<sub>6</sub>. A new O -species is observed on the bismuth molybdate surface reduced by Ar<sup>+</sup> ion bombardment.Wc discuss the above phenomena
基金financially supported by the National Natural Science Foundation of China (No.21271022)。
文摘Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work, a series of visible-light-driven Y^(3+)-doped BMO(Y-BMO) photocatalysts were synthesized via a hydrothermal method. Degradation experiments on Rhodamine B and Congo red organic pollutants revealed that the optimal degradation rates of Y-BMO were 4.3 and 5.3 times those of pure BMO, respectively. The degradation efficiency of Y-BMO did not significantly decrease after four cycle experiments. As a result of Y^(3+)doping, the crystal structure of BMO changed from a thick layer structure to a thin flower-like structure with an increased specific surface area. X-ray photoelectron spectroscopy showed the presence of highintensity peaks for the O 1s orbital at 531.01 and 530.06 eV, confirming the formation of oxygen vacancies in Y-BMO. Photoluminescence(PL) and electrochemical impedance spectroscopy measurements revealed that the PL intensity and interface resistances of composites decreased significantly, indicating reduced electron–hole pair recombination. This work provides an effective way to prepare high-efficiency Bibased photocatalysts by doping rare earth metal ions for improved photocatalytic performance.
基金financial support from European Union(Interreg FWVL V project PSYCHE)from the French National Research Agency(Multiprobe project,ANR-20-CE42-0007)。
文摘CO_(2)hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes,as well as to produce valuable chemicals from renewable and abundant resources.Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons.Iron-molybdenum catalysts have found numerous applications in catalysis,but have been never evaluated in the CO_(2)hydrogenation.In this work,the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal(Li,Na,K,Rb,or Cs)were characterized using X-ray diffraction,hydrogen temperatureprogrammed reduction,CO_(2)temperature-programmed desorption,in-situ^(57)Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy.Their catalytic performance was evaluated in the CO_(2)hydrogenation.During the reaction conditions,the catalysts undergo the formation of an iron(Ⅱ)molybdate structure,accompanied by a partial reduction of molybdenum and carbidization of iron.The rate of CO_(2)conversion and product selectivity strongly depend on the promoting alkali metals,and electronegativity was identified as an important factor affecting the catalytic performance.Higher CO_(2)conversion rates were observed with the promoters having higher electronegativity,while low electronegativity of alkali metals favors higher light olefin selectivity.
基金supported by the National Natural Science Foundation of China(52261040,51971104)the Outstanding Postgraduate Innovation Star Project of Gansu Provincial Department of Education(2022CXZX-383)。
文摘The supercapacitor electrode materials suffer from structure pulverization and sluggish electrode kinetics under high current rates.Herein,a unique NiMoO_(4)@Co-B heterostructure composed of highly conductive Co-B nanoflakes and a semiconductive NiMoO_(4) nanorod is designed as an electrode material to exert the energy storage effect on supercapacitors.The formed Mott-Schottky heterostructure is helpful to overcome the ion diffusion barrier and charge transfer resistance during charging and discharging.Moreover,this crystalline-amorphous heterogeneous phase could provide additional ion storage sites and better strain adaptability.Remarkably,the optimized NiMoO_(4)@Co-B hierarchical nanorods(the mass ratio of NiMoO_(4)/Co-B is 3:1)present greatly enhanced electrochemical characteristics compared with other components,and show superior specific capacity of 236.2 mA h g^(-1)at the current density of 0.5 A g^(-1),as well as remarked rate capability.The present work broadens the horizons of advanced electrode design with distinct heterogeneous interface in other energy storage and conversion field.
基金supported by the China Postdoctoral Science Foundation (No.20080430556)the Major State Basic Research and Development Program of China (No.2006CB705600)
文摘A new series of solid solutions Lu2W3-xMoxO12 (0.5≤r≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth ttmgstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients (TEC) of Lu2W3_xMoxO12 are determined as -20.0× 10^-6 K^-1 for x=0.5 and -16.1×10^-6 K^-1 for x=2.5 but -18.6× 10^-6 and -16.9× 10^-6K^-1 for unsubstituted Lu2W3012 and Lu2M03012 in the identical temperature range of 200 to 800℃. High-temperature X-ray diffraction (XRD) data and bond length analysis suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.
基金financial support of Brazilian agencies CNPq,FAPESP and CAPES.
文摘A simple way to prepare α- and β-CoMoO4 nanorods is reported in this paper. CoMoO4xH2O nanorod precursors were obtained using the microwave-assisted hydrothermal (MAH) method. By annealing the as-prepared CoMoO44xH2O precursor at 600℃ for 10 min in a domestic microwave oven, α- and β-CoMoO4 nanorods were prepared. These powders were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform Raman microscopy and ultraviolet visible absorption spectroscopy (UV-vis spectra) as well as photoluminescence (PL) measurements. Based on the results, these materials revealed nanorod morphology. PL spectra obtained at room temperature for α- and β-CoMoO4 particles exhibited maximum components around the blue light emission. The results show that the domestic microwave oven has been successfully employed to obtain α- and β-CoMoO4 nanoparticles.
基金Supported by the NNSFC (No. 60778035)the Key Project of Science and Technology of Fujian Province (2001F004)
文摘The Eu^3+:BaMoO4 nanostructures were synthesized by a simple hydrothermal method,and characterized by XRD,transmission electron microscopy,high-resolution transmission electron microscopy,excitation and emission spectra. Eu^3+:BaMoO4 nanostructures show a lotus leaf-shaped morphology,and exhibit a strong red emission at 612 nm,which may afford an opportunity for the development of other nanostructure materials.
基金Supported by the NNSFC (20373073)the National Basic Research Program of China (No. 2007CB815307)+2 种基金the Funds of CAS (KJCX2-YW-H01)Fujian Key Laboratory of Nanomaterials (No. 2006L2005)the Knowledge Innovation Program of CAS
文摘Solid-state reaction of praseodymium (III) oxide,K2CO3 and MoO3 at high temperature leads to a potassium lanthanide double molybdate,namely,KPr(MoO4)2. The structural and optical properties of the title compound have been investigated by means of single-crystal X-ray diffraction and spectroscopic measurements at room temperature. KPr(MoO4)2 crystallizes in tetragonal,space group I41/a with a = 5.401(3),c = 12.044(10),Z = 2 and R (I 〉 2σ(I)) = 0.0416. It features the famous scheelite-type structure (CaWO4),which can be thought as the substitution of two Ca^2+ ions in CaWO4 by a couple of K^+ and Pr^3+ ions in a statistical manner,and W^6+ by Mo^6+ cations.
基金supported by the National High Technology Research and Development Program of China(No.2009AA06Z106)Yunnan Provincial Science and Technology Department of China(No.2011GA004)
文摘This article investigated molybdenum recovery from oxygen pressure water leaching residue of Ni-Mo ore using alkaline leaching, followed by chemical treatment of leach liquor. Parameters affecting Mo leaching rate, such as sodium hydroxide concentration, reaction time, a liquid- to-solid ratio, and temperature for the preliminary alkaline leaching were experimentally determined. The results showed that more than 88 % of molybdenum was leached under the optimum conditions (2.5 ml.g-1 NaOH, 80 ℃, a liquid to solid ratio 3 ml.g-1, and reaction time 3 h). After the purification of leach liquor, a CaMoO4 product of 99.2 % purity could be obtained by CaCla precipitation method. The whole Mo recovery reached about 82.7 %.
文摘Trivalent samarium ion (Sm^(3+)) activated calcium molybdate (CaMoO_4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO_4∶Sm shows that the CaMoO_4∶Sm single phase is developed fully through our preparation procedure. The excitation spectrum of CaMoO_4∶Sm is composed of a broad absorption of host and some sharp lines of the f-f transition absorption of Sm^(3+). Illustrated in photoluminescence spectrum, CaMoO_4 doped with Sm^(3+) displays orange red emission that is ascribed to the inner 4f^5 electron transitions ~6H_(7/2)(orange)and ~6H_(9/2)(red)of Sm^(3+). Different from the sites of Sm^(3+) in CdWO_4, the Sm^(3+) ions substitute for the Ca^(2+) and form only one type emission center in the CaMoO_4 crystal lattice.
基金Funded by the General Program of Natural Science Foundation of Jiangsu Province of China(No.BK20171440)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(NY218039)
文摘In order to effectively improve the corrosion resistance of aluminum alloys, anodic oxidation technique was used to generate the oxide film. We investigated the influences of two inorganic corrosion inhibitors(ammonium dihydrogen phosphate and sodium molybdate) on the corrosion resistance of anodic oxidation films on 2024 aluminum alloy, and studied the synergistic effect of two corrosion inhibitors. The corrosion resistance of anodic oxidation film in 3.5 wt% NaCl solution was evaluated by electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization curves. Results show that, after adding the single ammonium dihydrogen phosphate or sodium molybdate of 0.01 M to oxalic acid electrolyte, inhibition efficiencies of the anodized samples are 10% and 47%, respectively. However, in the presence of two inhibitors with the same concentration of 0.01 M, inhibition efficiency can be as high as 92%. Therefore, we observed the significantly synergistic corrosion inhibition effect of molybdate and phosphate ions for anodic oxidation film formed on 2024 aluminum alloy.
基金Project supported by the Hebei Developing Foundation of Science &Technology (51215103b)
文摘In order to prepare fluorescent material for white Light Emitting Diodes (LEDs), a new Eu^3+ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction (XRD) showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3+ concentration on the luminescent properties of Eu^3+ doped SrMoO4 was investigated and the 25% (mole fraction) was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.
文摘In this work, both the thermal expansion and electrical conductivity of nanocrystalline La2Mo2O9 were studied.The nanocrystalline powder of La2Mo2O9 was obtained by sol-gel method, and with the help of SHP (superhigh pressure)up to 4.5 × 104 atm at 700 ℃ for a short time, and the nanocrystalline powder was densified without obvious particle size growth. The electrical conductivity of nanocrystalline La2Mo2O9 was one orderof magnitude lower than that of the microcrystalline sample at the same temperature. Owing to the phase transition, the microcrystalline La2Mo2O9 has an abrupt increase of thermal expansion with a peak value of 48 × 10-6 K-1 at 556 ℃. For the nanocrystalline material, the peak value increases to 112 × 10-6 K-1 at 520 ℃. On the other hand, above 600 ℃ the significant growth of particle size of the nanocrystalline La2Mo2O9 was observed, accompanying by a tremendous increase of thermal expansion with a peak value of third higher than that of La2Mo2O9.
基金NNSFC (No. 20501011) Liaocheng University (31801)
文摘One novel polyoxometalate compound connected via trivalent cerium cation as bridge H2{ [K(H2O)212[Ce(H2O)5]2(H2Mo1.16W10.84O42)}.8H2O 1 was designed and synthesized in aqueous solution. X-ray diffraction analysis reveals that the structure of 1 is a three-dimensional framework assembled from the arrangement of H2Mo1.16W10.84O42 (named paradodecmetalate-B) and Ce(H2O)5^3+ containing two planes, which are constructed through the unification of H2Mo1.16W10.84O42^10- and Ce(H2O)5^3+ along the [100] and [001] directions. Crystal data: H96Ce4KaMo2.32O128W21.68, Mr = 7074.89, monoclinic, P21/n, a = 12.5037(17), b = 17.002(2), c = 12.7473(17)A, β = 105.966(2)°, V = 2605.4(6)A^3, Z = 1, Dc = 4.509 g/cm^3, F(000) = 3132,μ = 26.098 mm^-1, R = 0.0377 and wR = 0.0789 (I 〉 2σ(I)).
基金supported by the National Natural Science Foundation of China(No.51701140).
文摘The purpose of this work was to enhance the corrosion resistance of the passive fi lm on 304 stainless steel(SS)by chemical modifi cation in alkaline phosphate–molybdate solutions.The 304 SS was passivated in both phosphate and phosphate–molybdate mixed solutions to investigate the eff ect of molybdate on its corrosion resistance.The experimental results indicated that the passive fi lm showed better corrosion resistance in Cl?-containing solutions after modifi cation in phosphate–molybdate solutions than in phosphate-only solutions.Energy-dispersive spectroscopy analyses revealed that the passive fi lm formed in phosphate–molybdate solutions contained Mo and P after modifi cation,which is the reason for the enhanced corrosion resistance.
基金Supported by Applied Basic Research Project of Yunnan Province(2017FD087)National Natural Science Foundation of China(31660559)
文摘This study was conducted to comprehensively evaluate the effects of salicylic acid and sodium molybdate on cold tolerance of an ornamental plant Bougainvillea glabra and to provide a theoretical guidance for landscape maintenance.B.glabra plants were treated with 0.5 mmol/L salicylic acid and 2.0 μmol/L alone or in combination,and then exposed to low temperature stress before physiological indices were measured.The results showed that all salicylic acid and sodium molybdate treatments reduced the relative conductivity and malondialdehyde( MDA) content of B.glabra to varying extents under the stress of low temperature,and more significant effect was achieved by using the two agents in combination.Oxygen free radicals production rate increased with decreasing temperature from 20 to 6 ℃,but declined with temperature decreasing from 3 to-3 ℃.The SOD activity of the control( CK) was significantly lower than that of other treatments at 0 and-3 ℃.The treatments with salicylic acid and sodium molybdate alone and in combination increased POD activity of B.glabra plants,especially at 0 ℃,as the POD activity of treatments T1,T2 and T3 was significantly higher than that of CK at 0 ℃.In addition,under low temperature stress,the contents of soluble sugar,starch and proline increased initially and decreased subsequently with temperature decreasing.The soluble sugar content at 3 ℃,starch and proline contents at 0 and-3 ℃ in treatments with salicylic acid and sodium molybdate alone and in combination were significantly higher than those of CK.All above results proved that salicylic acid and sodium molybdate are able to improve cold tolerance of B.glabra,and better effect can be achieved by using them together.
基金supported by the Natural Science Foundation of Shandong Province(ZR2014JL029,BS2015CL012,ZR2015BM005)
文摘Er3+/Yb3+ co-doped Li3Ba2Gd3(MoO4)8 phosphors were synthesized by conven- tional solid state reaction method, and their structure and spectral properties were investigated. The diffuse reflectance spectra showed that the 4I15/2→4I11/2 transition of Er3+ and the 2F7/2→2F5/2 transition of Yb3+ ions were highly overlapped. Under the excitation of 980 nm, three up-conver- sion (UC) luminescence bands around 530, 555 and 660 nm were observed, corresponding to the 2H11/2→ 4I15/2, 4S3/2 → 4I15/2 and 4F9/2-→4I15/2 transitions of Er3+ ions, respectively. The effects of the concentration and pumping power on the UC intensities of Li3Ba2Gd3(MoO4)8:Er3+/yb3+ phosphors were investigated, and the possible UC mechanism was proposed based on the results.