Low-valence Cations Research Articles

Impacts of Oxo Interactions on Np(V) Crown Ether Complexes.

Intermolecular interactions between the oxo group of an actinyl cation and other metal cations (i.e., cation-cation interactions) are dependent on the strength of the actinyl bond. These cation-cation interactions are prominently observed for the neptunyl cation [Np(V)O2]+ and are sufficiently stable enough to explore using a variety of chemical techniques. Herein, we investigate these intermolecular interactions in the neptunyl 18-crown-6 system, because this macrocyclic ligand provides both stable coordination and the proper sterics to engage the oxo group in bonding with both low-valent metal cations and neighboring neptunyl units. We report the structural and spectroscopic characterization of five neptunyl, [Np(V,VI)O2]+,2+, compounds: Np1a ([NpO2(18-crown-6)]ClO4), Np1b ([NpO2(18-crown-6)]AuCl4), Na-Np ([Np(V)O2(18-crown-6)(Na(H2O)(18-crown-6)][Np(VI)O2Cl4], Np-Np ([NpO2(18-crown-6)](NpO2Cl2NO3)], and Np-Cl (NpO2Cl(H2O)1.75). Each of these compounds were prepared from the ambient reactions of Np(V) in HX (where X = Cl, NO3) with the 18-crown-6 ether molecule. Structural information obtained from single-crystal X-ray diffraction data was paired with solid-state and solution Raman spectroscopy to provide information on the interaction of the neptunyl oxo atom with neighboring cations. Neptunyl (Np═O) bond lengths are not perturbed upon interaction with the Na+ cation (Na-Np), but elongation is observed upon formation of a neptunyl-neptunyl interaction (Np-Np). This is also the first structurally characterized isolated, molecular complex that contains a simple T-shaped neptunyl-neptunyl interaction. Raman spectroscopy indicates little perturbation to the neptunyl bond until the formation of the neptunyl-neptunyl motif, which also results in activation of the ν3 asymmetric stretch. Additional spectroscopic studies indicated that the neptunyl 18-crown-6 inclusion complexes form in solution and persist in the presence of other low-valence cations.

Tent-pitching-inspired high-valence period 3-cation pre-intercalation excels for anode of 2D titanium carbide (MXene) with high Li storage capacity

MXenes exhibit potentials as electrode materials for metal ion batteries because of high electronic conductivity. However, ionic conductivity of MXenes has set the bottleneck to meet high energy and powder density demand in energy storage. Even though significant progresses have been made for more delicate design of electrodes, it remains very challenging for how to enhance the ion transport capability with the aid of external electric field upon charging process. Herein, high-valence cation (i.e., Al3+ in Period 3) pre-intercalation was utilized to construct an expanded ion transfer channel, which allows for further broadening upon the charging process, in order to enhance the ionic conductivity. This approach was confirmed to effectively improve Li storage capacity and cyclic stability of 2D Ti3C2Tx MXene anode. Compared to low-valence cation Na+, high-valence Al3+ into MXenes layer affords a strong Coulombic interaction upon lithiation/charging process to sustain ion transport channels. Moreover, the common deformation of electrodes upon cycling was limited due to a lower Li diffusion barriers. These findings raise the prospects of an enhanced ion transport capability and reinvent our knowledge of high-valence cations incorporation into 2D and layered materials.

Formation of Two-dimensional Electron Gas at Amorphous/Crystalline Oxide Interfaces

Experimentally, we found the percentage of low valence cations, the ionization energy of cations in film, and the band gap of substrates to be decisive for the formation of two-dimensional electron gas at the interface of amorphous/crystalline oxide (a-2DEG). Considering these findings, we inferred that the charge transfer from the film to the interface should be the main mechanism of a-2DEG formation. This charge transfer is induced by oxygen defects in film and can be eliminated by the electron-absorbing process of cations in the film. Based on this, we propose a simple dipole model that successfully explains the origin of a-2DEG, our experimental findings, and some important properties of a-2DEG.

Nano-TiNb2O7/carbon nanotubes composite anode for enhanced lithium-ion storage

Although with a large capacity, TiNb2O7 as an anode material of lithium-ion batteries suffers from a poor rate capability. To solve this challenge, nano-TiNb2O7 and its carbon nanotube (CNT) nanocomposites were prepared by direct hydrolysis of TiNb2O7/CNTs suspension followed by calcination in air and N2, respectively. The TiNb2O7 nanoparticles in the composites have a Ti2Nb10O29-type crystal structure with O2− vacancies and lower-valence cations, leading to improved Li+-ion diffusion coefficient and increased electronic conductivity in TiNb2O7. The evenly distributed CNTs have good contact with the TiNb2O7 particles, thereby reducing their particle sizes and improving the electrical conduction. As a result of these improvements, the nanocomposites present outstanding electrochemical performances. For example, it delivers a large reversible capacity (346 mAh g−1 at 0.1 C) and a prominent rate capability (still 163 mAh g−1 at the ultra-large current rate of 30 C). Exceptional cyclic stability is also demonstrated with over 100 cycles at 10 C with large capacity retention of 97.6%. These results reveal that the nano-TiNb2O7/CNTs composites can be a promising anode material for lithium-ion batteries of electric vehicles.

Preparation of porous oxide layers by oxygen bubble templated anodic deposition followed by galvanic displacement

Galvanic displacement reactions between porous PbO2, prepared by oxygen bubble templated anodic deposition, and the low-valent cations Mn2+, Co2+ and Sn2+, have been studied using electrochemical methods, SEM-EDS and XPS. These reactions occur at open circuit by immersion of PbO2 coated electrodes in aqueous solutions of the cations and lead to the formation of outer oxide layers onto porous PbO2, whose composition and chemical nature have been assessed by XPS. The growth of the outer oxide layers has been studied by combining Evans’ diagrams with SEM-EDS and XPS results, as a function of experimental variables, such as the chemical nature of the cations, their concentration and the solution temperature. The combination of oxygen bubble templated anodic deposition and galvanic displacement provides a route for the preparation of porous low-conductivity electroactive oxides not attainable by direct electrodeposition. Deposition of Co3O4 thin layers by galvanic displacement results in a strong enhancement of the activity of porous PbO2 electrodes in the oxygen evolution reaction.

Hidden Oceans? Unraveling the Structure of Hydrous Defects in the Earth's Deep Interior.

High-pressure silicates making up the main proportion of the earth's interior can incorporate a significant amount of water in the form of OH defects. Generally, they are charge balanced by removing low-valent cations such as Mg2+. By combining high-resolution multidimensional single- and double-quantum 1H solid-state NMR spectroscopy with density functional theory calculations, we show that, for ringwoodite (γ-Mg2SiO4), additionally, Si4+ vacancies are formed, even at a water content as low as 0.1 wt %. They are charge balanced by either four protons or one Mg2+ and two protons. Surprisingly, also a significant proportion of coupled Mg and Si vacancies are present. Furthermore, all defect types feature a pronounced orientational disorder of the OH groups, which results in a significant range of OH···O bond distributions. As such, we are able to present unique insight into the defect chemistry of ringwoodite's spinel structure, which not only accounts for a potentially large fraction of the earth's entire water budget, but will also control transport properties in the mantle. We expect that our results will even impact other hydrous spinel-type materials, helping to understand properties such as ion conduction and heterogeneous catalysis.

Photocatalytic activity of binary metal oxide nanocomposites of CeO2/CdO nanospheres: Investigation of optical and antimicrobial activity

We report the synthesis of high quality CeO2-CdO binary metal oxide nanocomposites were synthesized by a simple chemical precipitation and hydrothermal method. Cerium nitrate and cadmium nitrate were used as precursors. Composition, structure and morphology of the nanocomposites were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD pattern proves that the final product has cubic phase and the particle size diameter of the nanocomposites are 27nm, XRD results also indicated that the crystalline properties of the nanocomposite were improved without affecting the parent lattice, FESEM analysis indicates that the product is composed of spherical particles in clusters. The morphological and optical properties of CeO2-CdO nanosamples were characterized by HRTEM and DRS spectroscopy. The IR results showed high purity of products and indicated that the nanocomposites are made up of CeO2 and CdO bonds. Absorption spectra exhibited an upward shift in characteristic peaks caused by the addition of transition metal oxide, suggesting that crystallinity of both the metal oxide is improved due to specific doping level. TGA plots further confirmed the purity and stability of nanomaterials prepared. Hence the nanocomposite has cubic crystal lattice and form a homogeneous solid structure. From the result, Cd2+ ions are embedded in the cubic crystal lattice of ceria. The growth rate increases which are ascribed to the cationic doping with a lower valence cation. Ce-Cd binary metal oxide nanocomposites showed antibacterial activity, it showed the better growth inhibition towards p.aeruginosa. Exploit of photodegradation and photocatalytic activity of large scale synthesis of CeO2-CdO binary metal oxide nanocomposites was reported.

Exploration of Dopant Species for Lanthanum Polyphosphate

Doped lanthanum polyphosphate (LaP3O9) exhibits relatively high proton conductivity. For the practical applications such as the electrolyte of fuel cells, however, its conductivity must be improved by 2 orders of magnitude. Protons are introduced into matrix by lower-valent cation doping, and proton conductivity depends on dopant species. To date, LaP3O9 has been doped with only Ca, Sr and Ba. In this work, we tried to dope LaP3O9 with Na+, K+, Mg2+ and Pb2+, as the new dopant species, due to their close ionic radii to La3+. Among them, only Pb could substitute for La at a comparable concentration to those of alkaline earth metals and its highest doping level was 6.4 mol% (Doping level is defined as the concentration ratio of dopant (M) to host cation (La) site in matrix (≡M/(La + M) × 100 (mol%))). Though Pb can exist as either divalent or tetravalent state, Pb in LaP3O9 was identified to be divalent state by XPS analysis. Proton conduction was demonstrated by H/D isotope effect. The electrical conductivity of Pb-doped LaP3O9 increased with Pb-doping level, owing to the increase in proton concentration. The conductivity of 4.5 mol% Pb-doped LaP3O9 was about one order of magnitude lower than that of 7.9 mol% Sr-doped LaP3O9.

Molecular Dynamics Simulation on Oxide Ion Conduction of La-Based Perovskite Oxides for SOFCs Electrolyte

La-based perovskite oxides have various physical and electrical properties by substitution of various elements at A and/or B-sites. Especially, doping of low-valent cation generates oxygen vacancies to maintain charge neutrality, leading to high oxide ion conductivity. Also, B-site is comprised of transition metals such as Co, Mn or Fe, the La-based perovskite oxides become a mixed ionic-electronic conducting material. So, these La-based perovskite oxides can be applied to electrode, electrolyte or interconnect materials of solid oxide fuel cells (SOFCs). Recently, the SOFCs operating temperature is getting lower, much attention has been paid to the La-based perovskite oxides to alternate a conventional electrolyte material, yttria-stabilized zirconia (YSZ). To obtain an optimal La-based perovskite oxide with high oxide ion conductivity, it is very important to understand a correlation between experimental variables such as dopant type or concentration and various factors affecting the electrical conductivity. Therefore, we microscopically analyzed the effects of A-site dopant types and B-site cation types in LaInO3 perovskite oxide with orthorhombic structure on the oxide ion conductivity using molecular dynamics simulation. La0.9A0.1InO2.95 (A=Ca, Sr and Ba) and La0.9Sr0.1MO2.95 (In, Ga and Sc) compositions were modeled. The pair potential used in this study has two parts. One part represents long-range interaction described by Coulombic force. The other part represents short-range interaction by Born-Mayer-Huggins pair potential. The simulation box consisted of a total of 3960 atoms with periodic boundary conditions. Main calculations were carried out for 1.6ns with time step of 1fs after relaxation under NPT ensemble. From the radial distribution function results, it was found that the interionic distance between oxide ion and A-site dopant is important factor determining the ionic conductivity.

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP2O7

The effects of doped low-valence cations on the properties of the SnP2 O7 proton conductor at ambient temperature are investigated from changes in solid-state NMR spectra and nuclear magnetic relaxation times. Although the T1 H values increased with decreasing acidity as a result of cation exchange, the (1)H chemical shifts moved to lower field in Al- and In-doped materials compared with undoped ones. Furthermore, the shifts changed to higher field in Mg-doped materials, suggesting the existence of different protonic species in those materials. The bulk phosphate chemical shifts in the (31)P dipolar-decoupling MAS NMR spectra were very similar, regardless of the nature and amount of the doping species. On the other hand, by (1)H/(31)P cross-polarization MAS NMR, P2O7 signals interacting with an interstitial proton [Q(1)(proton)] were observed in all the undoped and doped SnP2 O7, while acidic P-OH-type phosphate signals [Q(1)(acid)] were additionally observed in the Mg-doped conductor. The different affinity of the proton with the dopants and phosphates caused lower conductivity and larger activation energy in the Mg-doped materials, compared with those in the In- and Al-doped materials.

Ammonothermal Synthesis and Photocatalytic Activity of Lower Valence Cation-Doped LaNbON2

Highly crystalline pure perovskite-type LaNbON2powders were synthesized in supercritical ammonia using sodium hydroxide as an oxygen source. Additionally, doping LaNbON2with cations of lower valence than that of the parent cation was performed to inhibit reduction of Nb5+. Various characterization methods indicated that crystallinity, particle morphology, and absorption edge of the product, that is, the factors possibly affecting photocatalytic activity, were not significantly changed by the doping of a lower-valence cation. Nevertheless, the doped LaNbON2synthesized using the ammonothermal method evolved hydrogen, suggesting that this type of doping decreases the formation of reduced niobium species and consequently enhances the photocatalytic activity of LaNbON2. In case of doped LaNbON2synthesized using conventional method, no hydrogen evolution was observed. This difference is probably due to the higher crystallinity of ammonothermally synthesized LaNbON2. Therefore, we successfully produced LaNbON2with improved potential for photocatalytic activity for hydrogen evolution under visible light irradiation using ammonothermal synthesis and lower-valence cation doping.

Conductivity enhancement of yttria doped ceria by spark plasma and ac assisted sintering methods

CeO2 doped with lower valence cations, such as Y3+, Sm3+, Gd3+, etc., is considered as electrolyte material for low temperature solid oxide fuel cells. Doping introduces additional oxygen vacancies and improves ionic conductivity. This work describes the preparation of yttria–calcia doped ceria precursor material, its sintering in DC and AC field methods, and characterisation of sintered electrolytes with respect to the ionic conductivity. Doped precursor materials were prepared by a controlled co-precipitation process. Sintering of prepared, pelletised particulates was carried out using three different methods such as: conventional, spark plasma sintering, and an alternating current field at 1125°C (AC assisted sintering). The conductivity was determined as a function of defect density, grain boundary area and phase stability. It was found that the applied field during sintering, either via pulsed DC (spark plasma), or AC, produced marginal effects on yttria doped ceria microstructure. However, it should be noted that because the sintering conditions were not optimised there is room for substantial conductivity improvements.On considère le CeO2 dopé avec des cations à valence plus faible, comme le Y3+, le Sm3+, le Gd3+, etc., comme matériau électrolyte pour les piles à combustible d’oxyde solide à basse température. Le dopage introduit des lacunes additionnelles d’oxygène et améliore la conductivité ionique. Ce travail décrit la préparation de matériau précurseur d’oxyde cérique dopé à l’oxyde d’yttrium-calcia, son frittage par des méthodes de champ CD et CA et la caractérisation des électrolytes frittés par rapport à la conductivité ionique. On a préparé les matériaux précurseurs dopés au moyen d’un procédé de co-précipitation contrôlée. On a effectué le frittage des particules préparées en boulette en utilisant trois méthodes différentes: conventionnelle, frittage au plasma à étincelles et un champ de courant alternatif à 1125°C (frittage assisté au CA). On a déterminé la conductivité en fonction de la densité de défaut, de la superficie de joint de grain et de la stabilité de phase. On a trouvé que le champ appliqué lors du frittage, soit par CD à impulsion (plasma à étincelles) ou par CA, produisait des effets marginaux sur la microstructure de l’oxyde cérique dopé à l’oxyde d’yttrium. Cependant, on doit noter que parce que les conditions de frittage n’étaient pas optimisées, il y a place pour des améliorations substantielles de la conductivité.

A bond-topological approach to theoretical mineralogy: crystal structure, chemical composition and chemical reactions

Here, I describe a theoretical approach to the structure and chemical composition of minerals based on their bond topology. This approach allows consideration of many aspects of minerals and mineral behaviour that cannot be addressed by current theoretical methods. It consists of combining the bond topology of the structure with aspects of graph theory and bond-valence theory (both long range and short range), and using the moments approach to the electronic energy density-of-states to interpret topological aspects of crystal structures. The structure hierarchy hypothesis states that higher bond-valence polyhedra polymerize to form the (usually anionic) structural unit, the excess charge of which is balanced by the interstitial complex (usually consisting of large low-valence cations and (H2O) groups). This hypothesis may be justified within the framework of bond topology and bond-valence theory, and may be used to hierarchically classify oxysalt minerals. It is the weak interaction between the structural unit and the interstitial complex that controls the stability of the structural arrangement. The principle of correspondence of Lewis acidity–basicity states that stable structures will form when the Lewis-acid strength of the interstitial complex closely matches the Lewis-base strength of the structural unit, and allows us to examine the factors that control the chemical composition and aspects of the structural arrangements of minerals. It also provides a connection between a structure, the speciation of its constituents in aqueous solution and its mechanism of crystallization. The moments approach to the electronic energy density-of-states provides a link between the bond topology of a structure and its thermodynamic properties, as indicated by correlations between average anion coordination number and reduced enthalpy of formation from the oxides for [6]Mg [4] Si n O(m+2n) and MgSO4(H2O) n .

Effects of shock-wave loading in oxides

This paper reports results of experimental study of the influence of shock waves on the structure, ion valence, and phase composition of oxides, including the minerals tenorite (CuO) and hausmannite (Mn3O4) and perovskite-structured manganite LaMnO3. Shock-wave loading (SWL) was modeled by explosion experiments in spherical and cylindrical (in the case of tenorite) configurations. The results of strong quasi-static shear deformations of oxides under pressure are also given for comparison. The main focus was the investigation of shock wave-induced changes in oxides at the level of chemical bonds, disturbances of ionic composition and stoichiometry, relation of these processes to the formation of micro(nano)structures in the minerals, and stages and microscopic mechanisms of the development of new dense phases. It was shown that SWL-affected oxides can be successfully investigated by various methods of X-ray spectroscopy (photoelectron, absorption, and emission) and nuclear techniques (Rutherford back scattering, nuclear reaction analysis, and positron annihilation spectroscopy). Crystal structure and phase composition were explored by X-ray and neutron diffraction methods. Microscopic structures were investigated by optical, scanning electron, and scanning tunneling microscopy. It was shown that the effects of SWL are initially manifested in oxides as a stoichiometry violation, an increase in the number of low-valence cations, and formation of a micro(nano)structure. Plastic deformations developed during SWL are especially important for these processes. The decomposition of oxides during the solid-phase stage of shock metamorphism under the influence of high pressures, temperatures, and severe plastic deformations produces oxides with a low degree of oxidation and free oxygen, which can migrate over considerable distances to form new compounds. The ultradeep penetration of particles of the surrounding matrix into the target mineral during SWL can also serve as a mechanism of shock metamorphism at the solid-phase stage of transformation.

Synthesis, characterization, and crystal structures of uranyl compounds containing mixed chromium oxidation states

The mixed-valence chromium uranyl compounds Li5[(UO2)4(Cr(V)O5)(Cr(VI)O4)4](H2O)17 (1), (Mg(H2O)6)5[(UO2)8(Cr(V)O5)2(Cr(VI)O4)8] (2) and (NH4)5[(UO2)4(Cr(V)O5)(Cr(VI)O4)2]H2O11 (3) have been synthesized and characterized. Each contains an identical sheet of cation-centered polyhedra. Central to the connectivity of the sheet are four uranyl pentagonal bipyramids that share some of their equatorial vertices, giving a four-membered ring. The Cr(V) cation located near the center of this ring is coordinated by O atoms in a square pyramidal arrangement. The Cr(VI) is tetrahedrally coordinated by O atoms, and these tetrahedra link the four-membered rings of bipyramids. The mixed-valence nature of the sheet was verified by XANES, an EPR spectrum, and bond-valence analysis. Low-valence cations and H2O groups reside between the sheets of uranyl and chromate polyhedra, where they provide linkages between adjacent sheets.

Lewis Base Mediated Autoionization of GeCl2 and SnCl2

Cationic and anionic species of heavier low-valent group 14 elements are intriguing targets in main group chemistry due to their synthetic potential and industrial applications. In the present study, we describe the synthesis of cationic (MCl(+)) and anionic (MCl(3)(-)) species of heavier low-valent group 14 elements of germanium(II) and tin(II) by using the substituted Schiff base 2,6-diacetylpyridinebis(2,6-diisopropylanil) as Lewis base (LB). Treatment of LB with 2 equiv of GeCl(2)·dioxane and SnCl(2) in toluene gives compounds [(LB)Ge(II)Cl](+)[Ge(II)Cl(3)](-) (1) and [(LB)Sn(II)Cl](+)[Sn(II)Cl(3)](-) (2), respectively, which possess each a low-valent cation and an anion. Compounds 1 and 2 are well characterized with various spectroscopic methods and single crystal X-ray structural analysis.

Tubular chains in the structures of natural and synthetic silicates

Tubular chains in the structures of natural and synthetic silicates have been described and systematized using the theory of graphs and by unfolding the tube topology onto a plane. Eight types of tubular chains have been considered: seven silicon-oxygen chains and one mixed titanosilicate chain; their topological and geometric characteristics are analyzed. It is shown that the presence of large cavities in tubes is generally related to their occupation by large low-valence cations (K+, Cs+, Ba2+, Sr2+, etc.) and water molecules. The overwhelming majority of minerals containing tubular silicate fragments were found in hydrothermal veins of alkaline massifs in Russia and abroad.

Charge compensation in trivalent cation doped bulk rutileTiO2

Doping of TiO2 is a very active field, with a particularly large effort expended using density functional theory (DFT) to modeldoped TiO2; this interest has arisen from the potential for doping to be used in tuning the band gap ofTiO2 for photocatalytic applications. Doping is also of importance for modifying the reactivity ofan oxide. Finally, dopants can also be unintentionally incorporated into an oxide duringprocessing, giving unexpected electronic properties. To unravel properly how dopingimpacts on the properties of a metal oxide requires a modelling approach that candescribe such systems consistently. Unfortunately, DFT, as used in the majority ofstudies, is not suitable for application here and in many cases cannot even yield aqualitatively consistent description. In this paper we investigate the doping of bulk rutileTiO2 with trivalent cations, Al, Ga and In, using DFT, DFT corrected for on-site Coulomb interactions (DFT + U, withU on oxygen 2p states) and hybrid DFT (the screened exchange HSE06 exchange correlationfunctional) in an effort to better understand the performance of DFT in describing suchfundamental doping scenarios and to analyse the process of charge compensation with thesedopants. With all dopants, DFT delocalizes the oxygen hole polaron that results fromsubstitution of Ti with the lower valence cation. DFT also finds an undistortedgeometry and does not produce the characteristic polaron state in the band gap.DFT + U and hybrid DFT both localize the polaron, and this is accompaniedby a distortion to the structure around the oxygen hole site.DFT + U and HSE06 both give a polaron state in the band gap. The band gap underestimation present inDFT + U means that the offset of the gap state from both the valence and the conductionband cannot be properly described, while the hybrid DFT offsets should becorrect. We have investigated dopant charge compensation by formation ofoxygen vacancies. Due to the large number of calculations required, we useDFT + U for these studies. We find that the most stable oxygen vacancy site has either a very smallpositive formation energy or is negative, so under typical experimental conditions, anionvacancy formation will compensate for the dopant.

Role of Local and Electronic Structural Changes with Partially Anion substitution Lithium Manganese Spinel Oxides on Their Electrochemical Properties: X-ray Absorption Spectroscopy Study

The electronic and local structures of partially anion-substituted lithium manganese spinel oxides as positive electrodes for lithium-ion batteries were investigated using X-ray absorption spectroscopy (XAS). LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0, 0.018, 0.036, 0.055, 0.073, 0.110, 0.180) were synthesized by the reaction between LiMn(1.8)Li(0.1)Ni(0.1)O(4) and NH(4)HF(2). The shift of the absorption edge energy in the XANES spectra represented the valence change of Mn ion with the substitution of the low valent cation as Li(+), Ni(2+), or F(-) anion. The local structural change at each compound with the amount of a Jahn-Teller Mn(3+) ion could be observed by EXAFS spectra. The discharge capacity of the tested electrode was in the order of LiMn(2)O(4) > LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0.036) > LiMn(1.8)Li(0.1)Ni(0.1)O(4) while the cycleability was in the order of LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0.036) ≈ LiMn(1.8)Li(0.1)Ni(0.1)O(4) > LiMn(2)O(4). It was clarified that LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) has a good cycleability because of the anion doping effect and simultaneously shows acceptable rechargeable capacity because of the large amount of the Jahn-Teller Mn(3+) ions in the pristine material.

Enhanced catalytic performance of assembled ceria necklace nanowires by Ni doping

Ceria and nickel-doped ceria necklace-like nanowires were synthesized by a facile, surfactant free method, through an unconventional assembly route. Homogeneous doping of lower-valent cations introduces elastic strain, resulting in extrinsic surface defects and higher catalytic performance in CO oxidization.