Magnetic Properties of Synthetic Libethenite Cu2PO4OH: a New Spin-Gap System

Recent Progress on Honeycomb Layered Oxides as a Durable Cathode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb-layered-oxides (HLOs) manifest outstanding structural stability, high redox potential, and long-life electrochemistry. Here, recent progress on HLOs as well as Na₃ Ni₂ SbO₆ and Na₃ Ni₂ BiO₆ as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state-of-the-art sodium-ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure-property relationship, and inspire more interest in high output voltage, long lifespan sodium-ion batteries.

Influence of the Metal Incorporation into Hydroxyapatites on the Deactivation Behavior of the Solids in the Esterification of Glycerol

The effects of the metal incorporation into hydroxyapatites on the deactivation behavior of the solids were examined in the esterification of glycerol (EG) reaction. The introduction of Cu, Co, or Ni ions by ion exchange in calcium-deficient hydroxyapatites resulted in active catalysts for the EG reaction. The metal contents were varied from 2.0 to 17.0%, providing better performances at rather high metal contents. Part of metal species existed in the hydroxyapatite lattice structure and also as isolated Cu2+, Ni2+, and Co2+ entities on the surface, as shown by XPS and EPR. The effects of the reaction temperature, reaction time, and glycerol to acetic acid molar ratios were deeply investigated. The spent solids used in this study were characterized by XRD, FTIR, SEM-EDS, chemical analyses, EPR, and XPS. The Cu2+–OH acid pairs could promote a superior catalytic performance of Cu-containing hydroxyapatites due to the resistance of these solids against leaching of the active species, which is even better than those of Co and Ni-containing counterparts with high metal contents. Cu into hydroxyapatite had a good reusability and long-term utilization for five consecutive cycles of 24 h under a glycerol to acetic acid molar ratio of 0.25 at 80 °C, and longer reaction times provide triacetin formation. This was due to the fact that Cu was stabilized by interacting with Ca, PO4, and OH sites into the hydroxyapatite lattice, being highly active for the EG reaction. The results also revealed that isolated Cu2+ sites played an important role in enhancing the glycerol conversion, intrinsically due to the Cu-containing hydroxyapatites ability to avoid strong adsorption of glycerol oligomers on the catalytic sites.

Synthesis, crystal structures, and magnetic properties of one-dimensional alkali metal copper chlor-tellurites A(NH4)Cu4Te2O6Cl6 (A = K, Cs), NaCu4Te2Cl5O6 and Rb3(NH4)2Cu12Te6Cl16.5O18(OH)0.5

Four new alkali metal copper chlor-tellurites, [Cs(NH4)]layer[Cu4Te2O6Cl6]layer (I), [Rb3(NH4)2(OH)0.5]layer[Cu12Te6Cl16.5O18]layer (II), [K(NH4)]layer[Cu4Te2O6Cl6]layer (III) and [NaCl]layer[Cu4Te2O6Cl4]layer (IV), have been synthesized via hydrothermal reactions using mixtures of AF (A = Cs, Rb, K, Na), CuCl2·2H2O, TeO2, and hydrazine monohydrate. They have two-dimensional (2D)-layered [Cu4Te2Cl5+x-yO6]∞ (x = 0, 2/3, 1; y = 0, 1/6) structures that are separated by different layers comprised of various cations and anions, including A+, NH4+ Cl- OH-, etc. The blocks feature S-shaped ∞[Cu2O3Cl3-x] chains linked by TeO3 trigonal pyramids. The magnetic susceptibility shows a broad maximum at 220 K for I and 240 K for III, which is well simulated by using an alternating antiferromagnetic chain model. The J2/J1 ratio within the alternating chain is estimated to be 0.60(1), and the spin gaps are refined to be 152 K for I and 136 K for III.

Twinned olivenite from Cap Garonne, Mine du Pradet – structure and magnetic behavior

Systematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F 2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/k B = 157(3) K.

Metal (M = Co, Ni) phosphate based materials for high-performance supercapacitors

With the ever increasing demand for clean, sustainable energy, electrochemical supercapacitors with the advantages of high power density, high efficiency and long life expectancy have become one of the major devices for energy storage and power supply, and have found wide application in hybrid power sources, backup power sources, starting power for fuel cells and burst-power generation in electronic devices.

Structural and magnetic studies on three new mixed metal copper(II) selenites and tellurites

Three new transition metal copper(II) selenites or tellurites, namely, CdCu(SeO3)2 (1), HgCu(SeO3)2 ()2, and Hg2Cu3(Te3O8)2 (3), have been obtained by conventional hydrothermal reactions of CdO (or Hg2Cl2), CuO and SeO2 (or TeO2). Compounds 1 and 2 are isostructural and crystallize in P2(1)/c. Their structures feature a 3D anionic framework of Cu(SeO3)2(2-) with 1D channels of eight-membered rings (MRs) along the c-axis and a-axis, respectively, which are filled by Cd(2+) or Hg(2+) cations. Compound 3 crystallizes in a tetragonal system of space group P42(1)2. Its structure is characterized by a [Cu3(Te3O8)2](2-) honeycomb layer composed of [Te3O8](4-) anions interconnected by Cu(2+) ions with 1D channels of 8-MRs along the c-axis. TOPOS analysis indicates that the copper(ii) tellurite layer exhibits a new topological structure with a Schläfli symbol of {4(6)·8(9)}(2){4(6)}(3). The above anionic copper(II) tellurite layers are further linked by dumbbell Hg2(2+) cations to form a novel 3D framework. Magnetic measurements based on magnetic susceptibility and heat capacity indicate that compounds 1 and 2 show a spin-singlet ground state with a spin gap based on the [Cu2O8](12-) dimeric model, whereas compound e3 xhibits a 2D spin-system with an antiferromagnetic ordering around 25 K correlated with its honeycomb [Cu3(Te3O8)2](2-) layer. Furthermore, crystalline structures, thermal stabilities, IR spectra and UV-Vis diffuse reflectance spectra have also been studied.

Vis/NIR light driven mild and clean synthesis of disulfides in the presence of Cu2(OH)PO4 under aerobic conditions

A highly efficient one-pot strategy has been developed for the synthesis of disulfide in the presence of air under the irradiation of Vis/NIR light.

Cu2(OH)PO4/g-C3N4 composite as an efficient visible light-activated photo-Fenton photocatalyst

The synergistic effect of Cu₂(OH)PO₄/H₂O₂ and g-C₃N₄ highly boosts the catalytic activity towards photo-Fenton photocatalytic degradation of rhodamine B.

High pressure structural and vibrational properties of the spin-gap system Cu2PO4(OH)

The structural and vibrational properties of the spin-gapped system Cu(2)PO(4)(OH) have been investigated at room temperature under high pressure up to ~20 GPa by Raman scattering and synchrotron-based x-ray diffraction and infrared (IR) spectroscopic measurements. The orthorhombic phase (space group Pnnm, z = 4) remains stable up to at least 7 GPa where it undergoes a weakly first order structural transition (with negligible volume drop) to a monoclinic phase (space group P2(1)/n, z = 4) with an abrupt monoclinic distortion. Refinement of atomic positions has been performed for the low pressure phase. The conspicuous changes in the vibrational spectra (Raman as well as far-IR) confirm this phase transition. At further higher pressures the monoclinic angle increases rapidly and the system transforms irreversibly into a disordered phase. Detailed vibrational analyses have been performed in the orthorhombic phase and pressure-induced structural evolution has been correlated with the vibrational modes corresponding to the Cu-O bonds. A strong negative pressure dependence of hydroxyl mode frequencies (as observed from the mid-IR absorption spectra) supports the pressure-induced structural disordering at higher pressures.

Spin interactions in mineral libethenite series: evolution of low-dimensional magnetism

Interesting magnetic properties and spin-exchange interactions along various possible pathways in the half-integral spin quantum magnetic tetramer system: A(2)PO(4)OH (A=Co, Cu) are investigated. Interplay of structural distortion and the magnetic properties with the evolution of localized band structure explain the gradual transition from a three-dimensional antiferromagnet to a low-dimensional frustrated magnetic system along the series. A detailed study of the exchange mechanism in this system explores various possibilities of complex magnetic interaction. The electronic structure of this series, studied with the help of different appropriate density functional approaches such as Nth order muffin-tin orbital (NMTO) and plane-wave pseudopotential calculations incorporating onsite Coulomb repulsion (U), identifies the underlying magnetic exchange mechanism of this series. Thereafter a generalized minimal model spin-Hamiltonian is constructed for the low-dimensional system. Solution of this model Hamiltonian within first-order perturbation theory results in the evaluation of spin-gap in the spin-tetramer system. In addition, the effects of size confinement and volume reduction on the relevant exchange integrals and spin-gap of the low-dimensional system are also discussed.