Synthesis and characterization of Na11[CuO4][SO4]3

Na₁₁[CuO₄][SO₄]₃ was obtained from a redox reaction of CuO with Na₂O₂ in the presence of Na₂O and Na₂SO₄ in sealed Ag containers under Ar atmosphere at 600°C. The crystal structure has been determined from X-ray single crystal data at 293 and 170 K (Pnma, Z=4). The lattice parameters have been refined from X-ray powder data at 293 K as well: a=1597.06(6) pm, b=703.26(3) pm, c=1481.95(6) pm. The structure contains isolated distorted square-planar [CuO₄]⁵⁻ anions and non-coordinating sulfate groups. Furthermore, we report calculations of the Madelung Part of the Lattice Energy (MAPLE) and some of the physical properties of Na₁₁[CuO₄][SO₄]₃.     

水系混合离子全电池LiMn2O4//NaTi2(PO4)3

分别以LiMn_2O_4,NaTi_2(PO_4)_3为正负极,1 mol·L~(-1) Li_2SO_4和0.5 mol·L~(-1) Na_2SO_4的混合水溶液为电解液组装成一种水系混合离子全电池。分别将正负极材料在3种不同水相电解液(1 mol·L~(-1) Li_2SO_4、0.5 mol·L~(-1)Na_2SO_4以及1 mol·L~(-1) Li_2SO_4+0.5 mol·L~(-1)Na_2SO_4混合电解液)中进行循环伏安和恒流充放电测试,结果发现,LiMn_2O_4在上述电解液中仅有Li~+的脱出/嵌入而Na~+由于半径较大而不参与该过程,NaTi_2(PO_4)_3在3种电解液中Li+、Na+均参与嵌入/脱嵌过程,且Li~+和Na~+的嵌入/脱出峰电位相差不大,分别为-0.82和-0.64 V,-0.95和-0.75 V;全电池在265 mA·g~(-1)电流密度下平均放电电压为1.55 V,充放电比容量分别为100.1和74.9 m Ah·g~(-1)。     

Electrochemistry of Na2SO4 (I) solid solutions with aliovalent cation substitution

Conductivity data of several Na₂SO₄(I) solid solutions with cation substitutions are presented. The substitution of sodium by bi- and trivalent atoms generates cation vacancy concentrations up to 30% in the structure of Na₂SO₄(I) thus creating high mobility of Na⁺. Electrochemical measurements showed that Na⁺ ion conductivity prevails and that the electronic partial conductivity is negligible. Complex impedance diagrams were used to determine the influence of the vacancy concentration on the ionic conductivity of Na₂SO₄(I) solid solutions. It was found that the conductivity is strongly correlated to the vacancy concentrations, whereas the size and the charge of the substituting ions show no effect within the accuracy of the measurements. The activation energy as function of the vacancy concentration exhibits a minimum of 0.7 eV at a vacancy concentration of 1%. The maximum of conductivity was found to be 1.5 × 10^?2 Ω^?1 cm^?1 at 500°C with 7% vacancies.     

The crystal structure of Na7Mg4.5(P2O7)4

The crystal structure of Na₇Mg_4.5(P₂O₇)₄ has been solved by direct methods from the three-dimensional X-ray data. The space group is $\text{P}\text{1}$. The crystal structure consists of Mg²⁺, Na⁺, and P₂O^4?₇ ions. One magnesium atom at symmetry center (0,0,0) and two sodium atoms at ±(?0.0421, ?0.0596, 0.2230) display occupation factors 0.5 each. A short interatomic distance between these Na⁺ and Mg²⁺ ions (1.80 ± 0.01 Å) excludes the occupation of both sites in the same unit cell. The crystal structure of Na₇Mg_4.5(P₂O₇)₄ consists of unit cells containing Na₈Mg₄(P₂O₇)₄ or Na₆Mg₅(P₂O₇)₄ with a statistical occurrence 1:1.Each Mg²⁺ ion is octahedrally coordinated by six O^2? ions at distances 1.979 – 2.270 Å. The coordination polyhedra around the Na⁺ ions are ill-defined. The bond angles POP in the P₂O^4?₇ groups are 126.6 and 133.6° (±0.3°). The final reliability factor R is 7.1%.     

Thermodynamic representation of the NaCl + Na2SO4 + H2O system with electrolyte NRTL model

A comprehensive thermodynamic model based on the electrolyte NRTL (eNRTL) activity coefficient equation is developed for the NaCl + H₂O binary, the Na₂SO₄ + H₂O binary and the NaCl + Na₂SO₄ + H₂O ternary. The NRTL binary parameters for pairs H₂O-(Na⁺, Cl⁻) and H₂O-(Na⁺, SO₄²⁻), and the aqueous phase infinite dilution heat capacity parameters for ions Cl⁻ and SO₄²⁻ are regressed from fitting experimental data on mean ionic activity coefficient, heat capacity, liquid enthalpy and dissolution enthalpy for the NaCl + H₂O binary and the Na₂SO₄ + H₂O binary with electrolyte concentrations up to saturation and temperature up to 473.15 K. The Gibbs energy of formation, enthalpy of formation and heat capacity parameters for solids NaCl_(s), NaCl·2H₂O_(s), Na₂SO_4(s) and Na₂SO₄·10H₂O_(s) are obtained by fitting experimental data on solubilities of NaCl and Na₂SO₄ in water. The NRTL binary parameters for the (Na⁺, Cl⁻)-(Na⁺, SO₄²⁻) pair are regressed from fitting experimental data on dissolution enthalpies and solubilities for the NaCl + Na₂SO₄ + H₂O ternary.     

DSC investigation of the thermal behaviour of (NH4)2SO4, NH4HSO4 and NH4NH2SO3

Gaseous products evolved from (NH₄)₂SO₄, NH₄HSO₄ and NH₄NH₂SO₃ during successive heating and cooling cycles were flushed with inert gas into analyzer Dräger tubes hooked tightly to the terminal port of the DSC cell base. This simple procedure allowed the starting temperature of the decomposition to be determined and the amount of the individual gases in the mixture to be identified and even estimated. NH₄NH₂SO₃ at 523 K in humid air produced HNH₂SO₃ initially and, on further cycling, (NH₄)₂SO₄ and NH₄HSO₄ also appeared. The ΔH_f values for NH₄HSO₄ were (kJ mole^?1): in an airtight sample holder 12.67, in a dry argon atmosphere 11.93, and in a static air atmosphere 10.92. Endothermic peaks for (NH₄)₂SO₄ and 498 and 411 K represented the incongruent melting point and the polymorphic transition of (NH₄)₂SO₄·NH₄HSO₄. After the first heating in air to 530 K, (NH₄)₂SO₄ and NH₄HSO₄ exhibited closely similar cyclic DSC curves. The endothermic peaks at about 393–420 K may be assigned to different combinations of (NH₄)₂SO₄ and NH₄HSO₄.     

Influence of the preparation conditions on the textural properties andn-hexane isomerization activity of Pt/SO42??ZrO2

The effect of Na₂SO₄ and PhCOONa on the aquation of [Fe(Me₄phen)₃]²⁺ has been investigated in pure Triton X-100 as solvent. The rate and mechanism of the aquation are explained in terms of changes in the mobility, activity and structure of H₂O in the restricted environment of water pockets in the Triton X-100 solvent.     

(Nb2W4O19), TMA2, Na4(OH2)14(SO4): a new layered structure with Lindqvist heteropolyanions, XAS characterization of the HPAs

The new (Nb₂W₄O₁₉),TMA₂, Na₄(OH₂)₁₄(SO₄) has been evidenced as a minor phase during the Nb₂W₄O₁₉TMA (tetramethylammonium) salt synthesis. Its crystal structure has been refined from single crystal X-ray diffraction data, system monoclinic, a=10.166(5) Å, b=17.93(1) Å, c=24.81(1) Å, β=93.057(7)°, space group (S.G.) C2/c, Z=4, R₁=3.96%, wR₁=4.50%. It shows the stacking of cationic and anionic bidimensional layers. The anionic layer of formula [(Nb₂W₄O₁₉), TMA₂ ]²⁻ is formed of isolated Lindqvist HPAs surrounded by TMA groups. The isolated layers adopt a trigonal symmetry that is lost in the crystal by the association of the cationic sheets. These later, of formula [Na₄(OH₂)₁₄(SO₄)]²⁺ form porous net-like sheets with nearly circular cavities of diameter 7.5 Å. groups host the available cavities in a disordered manner. The cohesion between the sheets is performed by both electrostatic interactions and a set of hydrogen bonds. In the cationic layers, the highly symmetrical surrounding of HPAs by TMA groups yields a homogeneous electrostatic field at their external surface leading to a statistic Nb/W disorder over the three available independent metallic positions. Then, XAS experiments at the L₁/L₃-W edge complementarily helped to highlight the preferential cis configuration of (Nb₂W₄O₁₉)⁴⁻ anions, help to the strong Nb vs W contrast in their contribution to the backscattering paths. Previously to these experiments, it was of course checked that both the two phases present in the prepared sample contain Nb₂W₄O₁₉ anions with nearly unchanged geometry.     

Structure cristalline de K2SO4(SbF3)2

The crystal structure of K₂SO₄(SbF₃)₂ was determined by X-ray diffraction on a single crystal (R = 0.035 for 2264 reflections). There are two families of antimony atoms showing two different environments: AX₅E octahedron (6 coordination) and AX₆E 3.3.1 monocapped octahedron (7 coordination). The SO^2?₄ unit weakly bonded to four antimony atoms is not very distorted. This arrangement permits the minimization of π-E interactions. Infrared and Raman spectra are discussed in terms of diffraction results.     

Phase relations,dopant effects,structure, and high electrical conductivity in the Na2WO4Na2MoO4 system

The x, T-phase diagram of the binary system Na₂WO₄Na₂MoO₄ has been redetermined at ambient pressure, taking into account the influence of hysteresis effects. Thermodynamic calculations, based upon transition entropies as determined by precision DSC (differential scanning calorimetry), indicate that the system is almost ideal with respect to the high-temperature phases.As anion dopes, Na₂SO₄ and Na₂CrO₄ give a metastable extension of the β-phase of Na₂WO₄ at decreasing temperature, involving some 40°C at 0.01 mole fraction of dopant. Cation dopes like Li₂WO₄ and K₂WO₄ behave quite differently.The electrical conductivity through the phase diagram is high in the α-phase (σ ～ 10^?2 mho cm^?1) almost regardless of composition. The anomalous high conductivity of the β-phase decreases with increasing molybdate content. In pure Na₂MoO₄ an anomaly occurs at the α-α₂ transition, resembling the behavior of Na₂WO₄ at the β-α transition. The (highest) α₂-phase is hexagonal, ($\text{P6}{}_3\text{mmc}$, showing large anisotropic thermal vibrations. The α-phase is orthorhombic (Fddd) as is the β-phase (probably Pbn2₁).     

A study of the reaction Na2SO4·10H2O→Na2SO4+10H2O in the temperature range 0 to 25°C

Thermogravimetry was used to obtain data on the isothermal rate of dehydration and hydration of the reaction Na₂SO₄·10H₂O→Na₂SO₄+10H₂O in the temperature range 10 to 25°C. The thermodynamic functions, ΔH, ΔG and ΔS were calculated and compared with data in the literature. The dissociation pressures of Na₂SO₄·10H₂O at temperatures in the range 0 to 25°C were measured in a volumetric dissociation apparatus. The results obtained were compared with those using thermogravimetry and the accuracy of the two techniques was assessed.     

Influence of Adding SiO2 into ZrO2 on SO2-4/ZrO2 Solid Superacid

用共沉淀法和负载法制备了一系列SO     

NASICON型Na4FeV(PO4)3的合成、晶体结构和电化学性能

采用高温熔盐法制备了NASICON型Na_4Fe V(PO_4)_3单晶。单晶X射线衍射数据分析表明,Na_4Fe V(PO_4)_3属于六方R3c空间群,单胞参数为a=b=0.878 17(4) nm,c=2.170 1(2) nm,Z=6,V=1.449 31(18) nm~3。该磷酸盐属于典型的NASICON结构,由PO_4四面体和Fe/VO_6八面体共顶点组成三维框架结构,提供多维的Na~+传输通道,2种不同类型Na~+位于框架的间隙。以Na_4Fe V(PO_4)_3/C粉末样品作为钠电池正极材料并以金属钠为对电极制备电池时,电化学测试结果表明其具有较高的容量。     

纳米复合固体超强酸SO42-/CoFe2O4的制备和表征

采用纳米化学制备技术合成了新型的纳米复合固体超强酸催化剂ＳＯ４＾２－／ＣｏＦｅ２Ｏ４。用ＸＲＤ、ＴＥＭ、ＸＰＳ、红外光谱和比表面测定等技术研究了该催化剂的结构形态,结果表明：所研制的ＳＯ４＾２－／ＣｏＦｅ２Ｏ４２催化剂为晶态纳米粒子（〈５０ｎｍ）,比表面积很大（１５７ｍ＾２．ｇ＾－１）,ＳＯ４＾２－与氧化物的金属离子呈无机齿螯合状配位化合物的结合形式。以乙酸乙酯合成为模型反应考究了该催化剂的催化活     

A new structure type of phosphate: Crystal structure of Na2Zn5(PO4)4

A new compound, Na₂Zn₅(PO₄)₄, was identified in the system ZnONa₂OP₂O₅ and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F² and the refinement converged to R₁=0.0233 and wR₂=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn₅P₄O₁₆]_n²ⁿ⁻ covalent framework consisting of [Zn₄P₄O₁₆]_n⁴ⁿ⁻ layers. The powder diffraction pattern of Na₉Zn₂₁(PO₄)₁₇ is explained by simulating a theoretical pattern with NaZnPO₄ and Na₂Zn₅(PO₄)₄ in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na₂Zn₅(PO₄)₄ melts congruently at 855 °C and its conductivity is 5.63×10⁻⁹ S/cm.     

Conductivity properties of Na2SO4/CaCO3 catalysts and their effect on catalytic activities for oxidative coupling of methane

A series of Na₂SO₄ doped CaCO₃ catalysts were prepared. It was observed that the C₂ yields and selectivities of Na₂SO₄/CaCO₃ catalysts for OCM are intimately related to their conductivities. The effect of conductivity on the catalytic activity is discussed together with the conductivities and catalytic activities of the catalysts. The higher the conductivities, the higher the C₂ yields and selectivities are.     

Investigation of phase equilibria in the systems K2SO4Sc2(SO4)3, Rb2SO4Sc2(SO4)3 and Cs2SO4Sc2(SO4)3

Phase diagrams of the systems K₂SO₄Sc₂(SO₄)₃, Rb₂SO ₄Sc₂(SO₄)₃ and Cs₂SO₄ Sc₂(SO₄)₃ have been investigated by X-ray diffraction phase analysis and differential thermal analysis techniques. A salient feature of all the systems is the formation of M₃Sc(SO₄)₃, which melt incongruently, and MSc(SO₄)₂, which on heating decompose in the solid state.     

Li3V2(PO4)3/C和Li2.5Na0.5V2(PO4)3/C的结构和电化学性能的比较研究

采用溶胶-凝胶法合成了锂离子正极材料Li3V2(PO4)3/C(LVP/C)及Li2.5Na0.5V2(PO4)3/C,并用XRD、循环伏安及交流阻抗等方法,研究了大量Na+掺杂对材料结构和电化学性能影响。结果表明,大量钠离子的掺杂会使LVP结构由单斜向菱方转变。掺杂化合物Li2.5Na0.5V2(PO4)3/C在0.5 C充电1 C放电时,首次放电容量为118 mAh.g-1,50次循环后容量保持率为92.4%,并发现与单斜LVP存在多个放电平台不同,Li2.5Na0.5V2(PO4)3/C仅在3.7 V处有一个放电平台。     

The VO3−4 and Eu3+ luminescence in oxides with ordered β-K2SO4 structure

The VO^3?₄ and Eu³⁺ luminescence in compounds with ordered β-K₂SO₄ structure is reported. The ratio of the Eu³⁺ and vandate emission intensity depends on the excitation energy.