掺锰五磷酸铈晶体的生长及锰离子的价态

用蒸发溶液法从磷酸溶液中生长出不同掺锰量的五磷酸铈晶体。在合适的生长条件下可获得优质的光学晶体。用电子顺磁共振确定晶体中锰离子为二价。CeP_5O_(14)-Mn(II)的激发光谱和发射光谱表明,Ce~(3+)-Mn~(2+)间存在着能量转移。     

Intercalation of cobaltammine complex ions into layered manganese oxide

The intercalation of Co(2+), [Co(NH(3))(6)](3+), and [Co(NH(3))(5)Cl](2+) ions into layered manganese oxide (birnessite) was studied by chemical, XRD, SEM, IR, and DTA-TG analyses. The intercalation reaction progressed by a 2:1 or 3:1 ion-exchange mechanism depending on the valence of the starting ions. The oxidation state of cobalt did not change with the intercalation reaction. The intercalation of [Co(NH(3))(6)](3+) ions resulted in an increase of basal spacing from 0.716 to 0.956 nm, giving a layered structure material consisting mainly of platelike particles. The chemical analysis results showed that the structure of [Co(NH(3))(6)](3+) ions was maintained in the interlayer. On the other hand, an H(2)O/NH(3) ligand exchange reaction progressed for the intercalation of [Co(NH(3))(5)Cl](2+) ions, resulting in an increase in the basal spacing from 0.716 to 0.956 nm.     

Lithium manganese oxide with excellent electrochemical performance prepared from chemical manganese dioxide for lithium ion batteries

Chemical manganese dioxide (CMD) is synthesized by the SEDEMA process and adopted as a precursor for lithium manganese oxide with a spinel structure (LMO). LMO is also prepared from electrolytic manganese dioxide (EMD) as a reference for comparison. X-ray diffraction (XRD) shows that CMD is composed of γ-MnO₂, and scanning electron microscopy (SEM) with transmission electron microscopy (TEM) shows that the nanorods cover a spherical core with a diameter < 1 μm. The LMO prepared from CMD shows a much better rate capability and cycle life performance than that from EMD at high temperatures and high current densities. The excellent electrochemical performance is attributed to the structural stability during charge and discharge and the morphology of the LMO, a loose aggregation of the octahedral particles with a uniform size (<1 μm) and shape, which originated from that of CMD.     

The paper chromatography of some manganese and copper valency states

Chromatographic separations upon paper strips are described for Mn⁺² and Mn⁺³, Mn⁺³ and Mn^VII, and Cu⁺ and Cu⁺². The last separation was performed in an atmosphere of CO₂ to prevent the oxidation of Cu⁺. An unstable cuprous-8-hydroxyquinoline complex was prepared from cuprous chloride and oxine inpyridine medium. Analysis of the complex suggested the composition (CuC₉H₆ON.C₉H₇ON)₂. C₅H₅N.     

Uncovering an oxide ion substitution for the OH− + CH3F reaction

Theoretical investigations on chemical reactions allow us to understand the dynamics of the possible pathways and identify new unexpected routes. Here, we develop a global analytical potential energy surface (PES) for the OH⁻ + CH₃F reaction in order to perform high-level dynamics simulations. Besides bimolecular nucleophilic substitution (S_N2) and proton abstraction, our quasi-classical trajectory computations reveal a novel oxide ion substitution leading to the HF + CH₃O⁻ products. This exothermic reaction pathway occurs via the CH₃OH⋯F⁻ deep potential well of the S_N2 product channel as a result of a proton abstraction from the hydroxyl group by the fluoride ion. The present detailed dynamics study of the OH⁻ + CH₃F reaction focusing on the surprising oxide ion substitution demonstrates how incomplete our knowledge is of fundamental chemical reactions.

Reaction dynamics simulations on a high-level ab initio analytical potential energy surface reveal a novel oxide ion substitution channel for the OH⁻ + CH₃F reaction.     

Magnesium isotope separation by ion exchange using hydrous manganese(IV) oxide

The magnesium isotope effects were investigated by chemical ion exchange with a hydrous manganese(IV) oxide. The capacity of manganese(IV) oxide was 0.5 meq g(-1). The distribution coefficient of magnesium ions on the MnO(2) was determined by a batch method. The heavier isotopes of magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the hydrous MnO(2) phase. The separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays. The separation factors of (24)Mg(2+)-(25)Mg(2+), (24)Mg(2+)-(26)Mg(2+), and (25)Mg(2+)-(26)Mg(2+) isotope pair fractionations were 1.011, 1.021, and 1.011, respectively.     

Lithium ion phase-transfer reaction at the interface between the lithium manganese oxide electrode and the nonaqueous electrolyte

The lithium ion phase-transfer reaction between the spinel lithium manganese oxide electrode and a nonaqueous electrolyte was investigated by the ac impedance spectroscopic method. The dependence of the impedance spectra on the electrochemical potential of the lithium ion in the electrode, the lithium salt concentration in the electrolyte, the kind of solvent, and the measured temperature were examined. Nyquist plots, obtained from the impedance measurements, consist of two semicircles for high and medium frequency and warburg impedance for low frequency, indicating that the reaction process of two main steps for high and medium frequency obey the Butler-Volmer type equation and could be related to the charge-transfer reaction process accompanied with lithium ion phase-transfer at the interface. The dependency on the solvent suggests that both steps in the lithium ion phase-transfer at the electrode/electrolyte interface include the desolvation process and have high activation barriers.     

Synthesis of a new hollandite-type manganese oxide with framework and interstitial Cr(III)

Hollandite with Cr(III) in both tunnel and framework sites has been prepared hydrothermally from layered manganese oxide precursors.     

Pillared layered manganese oxide

Keggin ion-pillared buserite was prepared by ion-exchanging the hexylammonium ion-expanded buserite with Keggin ions, [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺. The starting material was synthetic Na-buserite, which is a layered manganese oxide of composition Na₄Mn₁₄O₂₆ xH₂O. The thermal and redox properties of this oxide and its pillared derivative were compared in O₂, N₂ and H₂ environments using TG, DSC and XRD. The results indicated an improvement in thermal stability of pillared compound relative to Na-buserite in all gaseous environments. By using these compounds in catalysing the oxidation of ethane, it was found that they were very active for complete oxidation.     

New layered manganese oxide halides

The first layered manganese(III) oxide chlorides, Sr2MnO3Cl and Sr4Mn3O8-yCl2, have been synthesised; Sr2MnO3Cl adopts a K2NiF4 type structure with sheets of MnO5 square based pyramids linked through oxygen and separated by SrCl layers; it is the end member of a new family of Ruddlesden-Popper type manganese oxide halides which includes the three-layer member Sr4Mn3O8-yCl2 also reported herein.     

Rational design of interfacial bonds within dual carbon-protected manganese oxide towards durable aqueous zinc ion battery

Manganese-based cathode materials are promising candidates for aqueous zinc ion batteries(AZIBs) by reason of their low cost and high energy density. However, their practical applicability is hampered by the intrinsic defects of poor electrical conductivity, sluggish reaction kinetics, and severe structural deterioration. Herein, we constructed a hierarchically porous structure composed of carbon-encapsulated Mn O nanoparticles(MOC) and three-dimensional(3D) nitrogen-doped graphene aerogel(NGA)(...     

Anodic deposition of layered manganese oxide into a colloidal crystal template for electrochemical supercapacitor

Electrodeposition of the layered manganese oxide was conducted in a colloidal crystal template formed by self-assembly of polystyrene particles on an indium tin oxide substrate. The resulting macroporous film exhibited good pseudocapacitive behavior in neutral electrolyte, as a result of contributions of the surface of macropores and the interlayer space of the multilayered structure.     

Self-assembly of microporous manganese oxide octahedral molecular sieve hexagonal flakes into mesoporous hollow nanospheres

Manganese oxide hollow nanospheres were prepared using a straightforward, template-free synthesis. The resulting material was mesoporous, crystalline, and of uniform diameter. The nanospheres were characterized by XRD, HR-SEM, and HR-TEM, and pore size distributions were calculated from nitrogen desorption. Unlike previous synthesis methods that use an inorganic template, this procedure requires no separation after synthesis to remove the template. The nanospheres are composed of hexagonal gamma-manganese oxide flakes and are approximately 400 nm in diameter. gamma-MnO2 is composed of a ramsdellite matrix (1 x 2 tunnels) with randomly distributed microdomains of pyrolusite (1 x 1 tunnels). These materials could have applications as cathodic battery materials, oxidation catalysts, catalyst supports, and adsorbents for pollutants.     

Synthesis of dumbbell-shaped manganese oxide nanocrystals

Dumbbell-like homogeneous MnO nanocrystals are obtained for the first time via the pyrolysis of manganese formate in trioctylamine/oleic acid media and the orientation aggregation mechanism is proposed for this 1D growth route.     

Ultrathin hollow nanoshells of manganese oxide

Novel hollow nanoshells of Mn(2)O(3) with controllable ultrathin shell thickness have been fabricated through layer-by-layer assembly of exfoliated MnO(2) nanosheets and polyelectrolytes on polymer bead templates, followed by removal of the polymer cores via calcination.     

Room-temperature synthesis of manganese oxide monosheets

Preparation of single-layer manganese oxide nanosheets (monosheets) comprised of edge-shared MnO(6) octahedra has relied on multistep processing involving a high-temperature solid-state synthesis of bulk templates, and ion-exchange and exfoliation reactions in solutions, requiring high cost and long processing time. Here we demonstrate the first single-step approach to directly access the MnO(2) monosheets, by the chemical oxidation of Mn(2+) ions in the presence of tetramethylammonium cations in an aqueous solution. Of importance is that this template-free reaction readily proceeds within a day at room temperature. The ability of the MnO(2) monosheets to self-assemble allows aggregation, to form layered structures with potassium cations and cationic tetrathiafulvalene analogues as intercalants. Furthermore, Langmuir-Blodgett (LB) films composed of the MnO(2) monosheets were successfully fabricated by the LB deposition method, in which about one layer of the monosheets was deposited for each process.     

Thermochemistry of iron manganese oxide spinels

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (Mn_xFe_1−x)₃O₄ at 298 K from the oxides, tetragonal Mn₃O₄ (hausmannite) and cubic Fe₃O₄ (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.67<x<1.0. Relative to cubic Mn₃O₄ (stable at high temperature) and cubic Fe₃O₄ (magnetite), the enthalpy of formation is negative for all compositions. The enthalpy of formation is most negative near x=0.2. There is no significant difference in the trend of enthalpy of formation versus composition for cubic (x<0.6) and tetragonal (x>0.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. ΔS_mix, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4.     

1.2 Volt manganese oxide symmetric supercapacitor

Capacitance fading of MnO₂ supercapacitor electrode under negative polarization below 0.0 V (versus Ag/AgCl/sat. KCl_(aq)) arises from extensive reduction of Mn(IV) to form inactive Mn(II) species, and this has typically limited the operating voltage window of an aqueous symmetric MnO₂ supercapacitor to be no greater than 0.8 V. As this lower potential limit is close to the onset potential of MnO₂-catalyzed oxygen reduction reaction (ORR), the fading problem can be alleviated by effectively passing the accumulated electrons in the oxide electrode to the dissolved oxygen molecules in electrolyte in order to avoid the formation of the surface Mn(II) species. This has been demonstrated by either increasing the dissolved oxygen content or using the Ti(IV)/Ti(III) redox couple in the electrolyte as a charge-transfer mediator to enhance the electrocatalytic activity of MnO₂ for ORR. Therefore, a MnO₂ symmetric supercapacitor showing remarkable cycling stability over an operating voltage window of 1.2 V has been achieved by using Ti(IV)-containing neutral electrolyte (1 M KCl_(aq)).     

Synthesis of manganese oxide electrodes with interconnected nanowire structure as an anode material for rechargeable lithium ion batteries

Manganese oxide electrodes composed of interconnected nanowires are electrochemically synthesized in manganous acetate solution at room temperature without any template and catalyst. Annealing temperature affects the electrode morphology, crystallization, and electrochemical performance. Scanning electron microscope (SEM) results show that nanowires are uniformly distributed and sizes are about 12-18 nm in diameter; the diameter decreases to about 8-12 nm after annealing at 300 degrees C. X-ray diffraction (XRD) and transmission electron microscope (TEM) images indicate that nanowires have poor crystalline characteristics. The higher the annealing temperature, the higher the crystalline degree is in manganese oxide. The synthesized anode material shows a much larger capacity than the traditional graphite materials for lithium storage. After annealing at 300 degrees C, the electrode's reversible capacity reaches 800 mAhg(-1), and the specific capacity retention remains nearly constant after 100 cycles.