Synthesis of MgCo2O4-coated Li4Ti5O12 composite anodes using co-precipitation method for lithium-ion batteries

Journal of Solid State Electrochemistry - In the present work, we report synthesis of MgCo2O4 (MCO)/Li4Ti5O12 (LTO) composites for Li-ion battery anodes by a co-precipitation method. The objective...     

First-principles calculations of stable local structures and electronic structures of magnesium secondary battery cathode materials,MgCo2−xMnxO4 (x = 0, 0.5), in second charged state after first discharge

Journal of Solid State Electrochemistry - The stable structures associated with the second charge of MgCo2−xMnxO4 (x = 0, 0.5), where Mg is removed from the stable first-discharge...     

Mg助剂对Co/Mg/HZSM-5催化剂结构及其催化甲烷部分氧化制合成气性能的影响

采用XRD、TEM、H2-TPR、Raman、XPS和活性评价等方法, 研究了Mg助剂对Co/Mg/HZSM-5催化剂物理化学性质和甲烷部分氧化(POM)制合成气反应性能的影响. 研究发现, 在Co/HZSM-5催化剂中添加Mg助剂, 可有效地提高催化剂的催化活性和稳定性. 在750 ℃和空速1.0×10⁵ mL·h^-1·g^-1反应条件下, Co/Mg/HZSM-5在连续反应30 h的实验时间内催化活性稳定不变, 而Co/HZSM-5因其活性中心Co0转化生成CoAl2O4非活性相, 反应10 h后即迅速失活. 催化剂表征结果表明, 在Co/Mg/HZSM-5催化剂中钴物种除以Co3O4存在外, 一部分钴物种还与Mg助剂发生强相互作用生成较难还原的MgCo2O4, 由此导致还原后钴金属的分散度较高. 关联催化剂表征和活性评价结果, 讨论了催化剂结构与性能之间的关系.     

碱促进的钴酸镁催化剂上的氧化亚氮分解

The direct decomposition of N2O was investigated over a series of magnesium cobaltite catalysts,MgxCo1-xCo2O4(0.0 ≤ x ≤ 1.0) ,which were prepared by the thermal decomposition of stoichiometric amounts of magnesium hydroxide and cobalt acetate. The thermal genesis of the different catalysts from their precursors was explored using thermogravimetric analysis,differential thermal analysis,and X-ray diffraction. Texture analysis was carried out using N2 adsorption at -196 °C. We found that all the catalysts tha...     

Synthesis, crystal structure, and catalytic properties of MgCo6Ge6

The ternary compound MgCo6Ge6 represents a novel member of the RM6X6 phases, which contains a graphite-type Ge network, Kagomé nets of Co atoms, and Ge2 dumbbells with an unexpected short Ge-Ge contact in the range of a localized Ge-Ge single bond. The title compound shows a large variety of chemical bonding, which ranges from metallic to multicenter and covalent bonding. The role of polar intermetallic alloys as promising candidates for the application as catalysts for the selective hydrogenation of alpha,beta-unsaturated aldehydes is discussed. MgCo6Ge6 possesses a remarkable activity and selectivity for the hydrogenation of cis/trans-citral to geraniol and nerol.     

Monitoring dehydration and condensation processes of Na2HPO4*12H2O using thermo-Raman spectroscopy

Thermal dehydration and condensation processes of disodium hydrogen phosphate dodecahydrate (Na2HPO4*12H2O) were monitored by thermo-Raman spectroscopy (TRS). Various hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were observed, followed by condensation of Na2HPO4 to sodium pyrophosphate (Na4P2O7) in a dynamic thermal process. Representative Raman spectra of all the hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were detected in both H2O and PO4(3- )regions are reported. The thermo-Raman intensity (TRI) thermogram also showed systematic loss of water in five steps of dehydration, with the differential TRI thermogram in agreement shows five dips corresponding to the five steps of dehydration, respectively. Thermogravimetry (TG) and differential thermogravimetry (DTG) are in harmony with the results of TRS, though, the two could not resolve the steps involved.     

Syntheses and structures of organic-inorganic hybrid compounds based on metal-fluconazole coordination polymers and the beta-Mo8O26 anion

Five organic-inorganic hybrid compounds, namely, [Co2(fcz)4(H2O)4][beta-Mo8O26].5H2O (1), [Ni2(fcz)4(H2O)4][beta-Mo8O26].5H2O (2), [Zn2(fcz)4(beta-Mo8O26)].4H2O (3), [Cu2(fcz)4(beta-Mo8O26)].4H2O (4), and [Ag4(fcz)4(beta-Mo8O26)] (5), where fcz is fluconazole [2-(2,4-difluorophenyl)-1,3-di(1H-1,2,4-triazol-1-yl)propan-2-ol], were synthesized under hydrothermal conditions, and crystal structures of 1-5 have been determined by X-ray diffraction. In compounds 1 and 2, metal cations are linked by fluconazole ligands to form hinged chain structures and [beta-Mo8O26]4- anions act as counterions. In compound 3, Zn(II) cations are bridged by fluconazole ligands to form 2D (4,4) networks, and each pair of these networks is linked by [beta-Mo8O26]4- anions to form a sandwich double-layer structure. In compound 4, Cu(II) cations are bridged by fluconazole ligands to form 2D (4,4) networks, and these networks are connected by [beta-Mo8O26]4- anions to form a 3D framework. In compound 5, AgI cations and [Ag2]2+ units are bridged by fluconazole ligands to form 2D Ag-fcz layers, and these layers are further connected by [beta-Mo8O26]4- anions to form a complicated 3D structure with the topology of (7(2).8(1))2(7(3).8(3))(7(2).8(11).10(1).12(1))2. Thermogravimetric analyses for these compounds are also discussed in detail. The complexes exhibit antitumor activity in vitro, as shown by MTT experiments.     

First principles study on the solvation and structure of C2O4(2-)(H2O)n, n = 6-12

The structures and energies of hydrated oxalate clusters, C2O4(2-)(H2O)n, n = 6-12, are obtained by density functional theory (DFT) calculations and compared to SO4(2-)(H2O)n. Although the evolution of the cluster structure with size is similar to that of SO4(2-)(H2O)n, there are a number of important and distinctive futures in C2O4(2-)(H2O)n, including the separation of the two charges due to the C-C bond in C2O4(2-), the lower symmetry around C2O4(2-), and the torsion along the C-C bond, that affect both the structure and the solvation energy. The solvation dynamics for the isomers of C2O4(2-)(H2O)12 are also examined by DFT based ab initio molecular dynamics.     

Tetranuclear clusters containing a CrIII-doped MnIII4O2 core: syntheses, structures, and magnetic properties

The oxidation of MnII carboxylates by (NBu4)Cr2O7 in the presence of different phosphonic acids and chelating ligands results in six CrIII-doped tetranuclear manganese clusters formulated [Mn3CrO2(O2CCH3)4(O3PC5H4N)2(bpy)2] (1), [Mn3CrO2(O2CCH3)4(O3PC5H4N)2(phen)2] (2), [Mn3CrO2(O2CPh)4(O3PC5H4NO)2(phen)2] (3), [Mn3CrO2(O2CPh)4(O3PC6H11)2(bpy)2] (4), [Mn 3CrO2(O2CPh)4(O3PC6H11)2(phen) 2] (5), and [Mn3CrO2(O2CCH3)4(O3PC6H11)2(bpy)2] (6). Single-crystal X-ray analyses reveal that all the compounds contain similar [M4O2]8+ cores with the four metal sites arranged in planar topologies. The metal ions within the core are bridged by both carboxylate and phosphonate ligands. Temperature-dependent magnetic measurements show that in all cases dominant antiferromagnetic interactions are propagated between the metal centers. The ac magnetic measurements on compounds 5 and 6 reveal that both the in-phase and the out-of-phase signals are frequency dependent, characteristic of single-molecule magnet behaviors.     

Solid state coordination chemistry: structural consequences of variations in tether length in the oxovanadium-copper-bisterpy-[O3P(CH2)nPO3]4- system, n= 1-6 (bisterpy = 2,2':4',4'':2'',2'''-quarterpyridyl-6',6''-di-2-pyridine)

Hydrothermal reactions of Na3VO4, an appropriate Cu(II) source, bisterpy and an organodiphosphonate, H2O3P(CH2)nPO3H2 (n = 1-6) yielded a family of materials of the type [Cu2(bisterpy)]4+/VxOy(n-)/[O3P(CH2)nPO3]4-. This family of bimetallic oxides is characterized by an unusual structural diversity. The oxides [[Cu2(bisterpy)]V2O4[O3PCH2PO3H]2] (1), [[Cu2(bisterpy)(H2O)]VO2[O3P(CH2)3PO3][HO3P(CH2)3PO3H2]] (4) and [[Cu2(bisterpy)]V2O4[O3P(CH2)6PO3H]2].2H2O (7.2H2O) are one-dimensional, while [[Cu2(bisterpy)(H2O)2]V2O4[O3P(CH2)2PO3][HO3P(CH2)2PO3H]2] (2), [[Cu2(bisterpy)]V4O8[O3P(CH23PO3]2].4H2O (3.4H2O) and [[Cu2(bisterpy)]V2O4(OH)2[O3P(CH2)4PO3]].4H2O (5.4H2O) are two-dimensional. The V(IV) oxide [[Cu2(bisterpy)]V4O4[O3P(CH2)5PO3H]4].7.3H2O (6.7.3H2O) provides a relatively unusual example of a three-dimensional bimetallic oxide phosphonate. The structures reveal a variety of V/P/O substructures as building blocks.     

LnCu2O4(Ln=Gd,Nd)电子结构的XPS研究

用XPS测定了LnCu2O4(Ln=Gd, Nd)的内层和价层电子能谱,观察到LnCu2O4中稀土金属的3d电子结合能比相应的稀土金属简单氧化物的3d结合能低0.8～0.9 eV,而Cu的2p电子结合能比CuO的高0.4～0.5 eV,因此推断在LnCu2O4的Ln－O－Cu链中存在Cu→O→Ln电荷转移.XPS分析还表明LnCu2O4的Cu原子上有较低的电荷密度,但不存在混合价态.此外,通过比较价电子能谱,发现NdCu2O4的Ln 4f Cu 3d O 2p价带中心比GdCu2O4的价带中心向Fermi能级移近了3.4 eV,而且NdCu2O4的价带谱更窄.     

LnCu_2O_4(Ln=Gd,Nd)电子结构的XPS研究

用 XPS测定了 LnCu2O4(Ln=Gd, Nd)的内层和价层电子能谱,观察到 LnCu2O4中稀土金属的 3d电子结合能比相应的稀土金属简单氧化物的 3d结合能低 0.8～ 0.9 eV,而 Cu的 2p电子结合能比 CuO的高 0.4～ 0.5 eV,因此推断在 LnCu2O4的 Ln－ O－ Cu链中存在 Cu→ O→ Ln电荷转移 .XPS分析还表明 LnCu2O4的 Cu原子上有较低的电荷密度,但不存在混合价态 .此外,通过比较价电子能谱,发现 NdCu2O4的 Ln 4f Cu 3d O 2p价带中心比 GdCu2O4的价带中心向 Fermi能级移近了 3.4 eV,而且 NdCu2O4的价带谱更窄 .     

Structure and Stability of P1Om Cages and Their Highly Charged Protonated Clusters P1OmHn^（n＋）：Insight from Density Functional Calculations

Density functional calculations are used to determine structural and electronic properties of P4,P4O6,P4O10,P20O30 and P20O50 clusters and their protonated derivatives.These oxygen-rich phosphorus oxides are predicted to have relatively high stabilities with respect to their components P4 and O2,and their unsaturated P and end-on O atoms as the proton acceptor can accommodate multiple protons to generate highly positively charged cationic clusters,such as P20O30H1010+.Calculations indicate that P4O6 and P20O30 have higher reactivity toward the proton capture than the P4,P4O10 and P20O50 clusters,and the most stable protonated clusters among these different series of cationic clusters are P4H22+,P4O6H22+,P4O10H33+,P20O30H44+ and P20O50H44+,respectively.The cage skeleton of the phosphorus oxide clusters shows high stability for the consecutive protonation,and the unsymmetrical stretching of the skeletal P-O bond and the wagging mode of P-H coupled with the P-O bond stretching have strong adsorptions.These computational findings are useful for further experimental and theoretical studies of novel phosphorus oxide clusters and their highly positively charged derivatives.     

Hybrid organic-inorganic 1D and 2D frameworks with epsilon-Keggin polyoxomolybdates as building blocks

Organic-inorganic hybrid materials based on polyoxometalate building blocks with capping La3+ ions and bidentate oxygenated ligands have been obtained by reaction at room temperature of the [epsilon-PMo12O36(OH)4[La(H2O)4]]5+ polyoxocation with glutarate (C5H6O(2)(2-)) and squarate (C4O(4)(2-)) organic ligands. [epsilon-PMo12O37(OH)3[La(H2O)4(C5H6O4)0.5]4].21 H2O (1) and [epsilon-PMo12O39(OH)[La(H2O)6]2-[La(H2O)5(C4O4)0.5]2].17 H2O (2) form unprecedented 1D chains built from alternating polyoxocations and organic ligands connected through LaO links. The structures of these materials are compared to the 2D hybrid organic-inorganic framework [NC4H12]2-[Mo22O52(OH)18[La(H2O)4]2[La(CH3CO2)2]4].8H2O (3) isolated from the hydrothermal reaction of elemental precursors (MoO(4)(2-), Mo, La3+) in acetate buffer. Compound 3 is built from previously undescribed polyoxometalate units with twenty-two MoV centers capped by six La3+ ions, four of which are bridged by acetate ligands.     

The Ag2O-V2O5-HF((aq)) system and crystal structure of alpha-Ag3VO4

Reactions between the three components Ag2O, V2O5, and HF(aq) were investigated under hydrothermal conditions, and the recovered phases were, in increasing Ag:V content, Ag2V4O11, beta-AgVO3, Ag4V2O6F2, Ag4V2O7, and alpha-Ag3VO4. A higher ratio of Ag2O to V2O5, as compared to a stoichiometric ratio, was required to synthesize Ag4V2O6F2, Ag4V2O7, and alpha-Ag3VO4. Owing to their solubility differences, the crystallization regions are not centered around the respective 2:1 and 3:1 Ag2O/V2O5 tie-lines but rather are centered along the 4:1 and 8:1 Ag2O/V2O5 tie-lines. Reactions with a 4:1 Ag/V ratio either resulted in Ag4V2O6F2 at 150 degrees C or Ag4V2O7 at 200 degrees C. Products were recovered in between 80% and 100% yield based on V2O5. Red transparent crystals of alpha-Ag3VO4 crystallize in the monoclinic space group C2/c, with cell parameters a = 10.1885(16) A, b = 4.9751(8) A, c = 10.2014(17) A, beta = 115.754(3) degrees .     

Experimental and theoretical study of hydrogen atom abstraction from n-butane by lanthanum oxide cluster anions

Lanthanum oxide cluster anions are prepared by laser ablation and reacted with n-C(4)H(10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. (La(2)O(3))(m=1-3)OH(-) and La(3)O(7)H(-) are observed as products, which suggests the occurrence of hydrogen atom abstraction reactions: (La(2)O(3))(m=1-3)O(-) + n-C(4)H(10) → (La(2)O(3))(m=1-3)OH(-) + C(4)H(9) and La(3)O(7)(-) + n-C(4)H(10) → La(3)O(7)H(-) + C(4)H(9). Density functional theory (DFT) calculations are performed to study the structures and bonding properties of La(2)O(4)(-), La(3)O(7)(-), and La(4)O(7)(-) clusters. The calculated results show that each of La(2)O(4)(-) and La(4)O(7)(-) contains one oxygen-centered radical (O(-?)) which is responsible for the high reactivity toward n-C(4)H(10). La(3)O(7)(-) contains one oxygen-centered radical (O(-?)) and one superoxide unit (O(2)(-?)), and the O(-?) is responsible for its high reactivity toward n-C(4)H(10). The O(-?) and O(2)(-?) can be considered to be generated by the adsorption of an O(2) molecule onto the singlet La(3)O(5)(-) with electron transfer from a terminally bonded oxygen ion (O(2-)) to the O(2). This may help us understand the mechanism of the formation of O(-?) and O(2)(-?) radicals in lanthanum oxide systems. The reaction mechanisms of La(2)O(4)(-) + n-C(4)H(10) and La(3)O(7)(-) + n-C(4)H(10) are also studied by the DFT calculations, and the calculated results are in good agreement with the experimental observations.     

In search of covalently bound tetra- and penta-oxygen species: a photoelectron spectroscopic and Ab initio investigation of MO4- and MO5- (M = Li,Na, K,Cs)

Although neutral and ionic O4(0/-/+) species have been observed experimentally and considered for energetic materials, O4(2-) and O5(2-) dianions have not yet been explored. O4(2-) is valent isoelectronic to the well-known ClO3- and SO3(2-) anions, and O5(2-) is valent isoelectronic to ClO4- and SO4(2-). All are stable, common anions in solutions and inorganic salts. In this article, we explore the possibility of making covalently bound O4(2-) and O5(2-) species stabilized in the forms of M+O4(2-) and M+O5(2-) (M = Li, Na, K, Cs) in the gas phase. Laser vaporization experiments using M-containing targets and an O2-seeded carrier gas yielded very intense mass peaks corresponding to MO4- and MO5-. To elucidate the structure and bonding of the newly observed MO4- and MO5- species, we measured their photoelectron spectra and then compared them with ab initio calculations and the spectra of ClO3-, Na+SO3(2-), ClO4-, and Na+SO4(2-). Careful analyses of the experimental and ab initio results showed, however, that the observed species are of the forms, O2-M+O2- and O2-M+O3-. The more interesting M+O4(2-) and M+O5(2-) species were found to be higher-energy isomers, but they are true minima on the potential energy surfaces, which suggests that it might be possible to synthesize bulk materials containing covalently bound tetra- and pentatomic oxygen building blocks.     

Oxygen-17 NMR study of aqueous peroxotungstates

Aqueous peroxotungstates have been studied from pH 0.5 to 9.0, over a range of peroxide concentrations. Although equilibria are not always established, many anions can be identified by 17O NMR because the ratio of deltaO(W anion)/deltaO(known Mo anion) is consistently 79 +/- 3%. They are [WO3(HO2)]-; [WO(OH)(O2)2]-; [WO(OH2)(O2)2]0; [W2O3(O2)4]2-; [W2O3(OH)(O2)4]3-; [W4O12(O2)2]4-; [W7O23(O2)]6- and [W7O22(O2)2]6-. Their pKa values, where measurable, are about 2 units lower than the corresponding peroxomolybdates, e.g. 0.0 for [WO(OH2)(O2)2]0 and 8.0 for [W2O3(O2)4]2-. Other peroxotungstate species are also present but can only be broadly identified. These include Keggin structures with relatively low peroxo content, and a very unsymmetrical anion appearing at pH ca. 7 that bears no obvious structural relationship to any species previously reported. The main product from the reaction of powdered W metal with 30% aqueous peroxide is provisionally identified as the symmetrical anion [W6O13(OH)2(OH2)2(O2)5]2-, although other minor species are also formed, probably having fewer peroxo substituents.     

Self-assembly of two- and three-dimensional coordination networks with hexamethylenetetramine and different silver(I) salts

Interesting two-dimensional networks with square or hexagonal cavities, and three-dimensional networks with different channels, have been obtained by varying the counterions, the molar ratio of metal to hmt (hmt = hexamethylenetetramine) and the pH values of the initial solutions. Among the eleven products isolated and structurally characterized, two have a metal-to-hmt molar ratio of 2:1 and are the first examples of Ag-hmt square networks, namely [Ag2(mu4-hmt)(NO2)2] (1) and [Ag2(mu4-hmt)(SO4)(H2O)].4H2O (2), two have a metal-to-hmt molar ratio of 1:1 and are 2-D networks with hexagonal cavities, namely [Ag(micro3-hmt)(NO2)] (3) and [Ag2(micro3-hmt)2](S2O6).2H2O (4), and seven present the metal-to-hmt molar ratios of 3:1, 2:1, 3:2, or 4:3 and are 3-D networks of novel topologies and with different channels, namely [Ag2(mu4-hmt)(micro4-ox)] (5), [Ag3(micro4-hmt)2(H2O)2](SO4)(HSO4). 2H2O (6), [Ag2(mu4-hmt)(mu2-O2CMe)](MeCO2).4.5 H2O (7), [Ag2(mu4-hmt)(mu3-maleate)].5H2O (8), [Ag3(mu4-hmt)(mu2-O2CPh)3] (9), [Ag4(mu4-hmt)3(H2O)](SO4)(NO3)2.3H2O (10), and [Ag12(mu4-hmt)6(mu3-HPO4)(mu2-H2PO4)3(H2PO4)7(H2O)](H3PO4).10.5H2O (11).     

Copper-complex-linked polytungsto-bismuthate (-antimonite) chain containing sandwich Cu(II) ions partially modified with imidazole ligand

Two sandwich-type complexes Na9n(Cu(im)4(H2O)2)1.5n(Cu(im)4(H2O))n[{Cu(im)4}{Na(H2O)2}3{Cu3(im)2(H2O)}(XW9O33)2]2n .(xH2O)n (im=imidazole, X=Bi (1), Sb(2), x=42.5 (1), 40 (2)) have been synthesized and structurally characterized. Basic frameworks of 1 and 2 are built from sandwich-type [{Na(H2O) 2} 3{Cu3(im)2(H2O)}(XW9O33)2](9-) (X=Bi or Sb) anions and [Cu(im) 4](2+) cations. The Cu(2+) and Na(+) ions in the central belt are coordinated by alpha-[XW9O33](9-) units, im, and water molecules to form {CuO4(im)}, {CuO4(H2O)}, and {NaO4(H2O)2} groups in which Cu (2+) ions are partially modified with im ligands. These groups connect alternately forming a six-membered ring including six alpha-[XW9O 33](9-) units. Neighboring anions are further linked by [Cu(im) 4](2+) cations to display an unprecedented anionic chain, which is first observed in sandwich-type tungsto-bismuthate (-antimonite) system. Two kinds of isolated copper complexes and sodium ions are located as counterions, which cause three-dimensional packings of 1 and 2 to present interesting cage structures. The magnetic properties for 1 and 2 both indicate dominant antiferromagnetic interactions among trinuclear Cu(II) clusters.