Coating of Al2O3 on layered Li(Mn1/3Ni1/3Co1/3)O2 using CO2 as green precipitant and their improved electrochemical performance for lithium ion batteries

Li(Mn_1/3Ni_1/3Co_1/3)O₂ cathode materials were fabricated by a hydroxide precursor method. Al₂O₃ was coated on the surface of the Li(Mn_1/3Ni_1/3Co_1/3)O₂ through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NHCO₃-H₂CO₃ buffer was formed spontaneously when CO₂ was introduced into the NaAlO₂ solution. Compared with bare Li(Mn_1/3M_1/3Co_1/3)O₂, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ electrodes delivered a discharge capacity of about 115 mAh·g^?1 at 2 A·g^?1, but only 84 mAh·g^?1 for the bare one. The capacity retention of the Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ was 90.7% after 50 cycles, about 30% higher than that of the pristine one.     

Vibrational spectra of MII3Pb(P2O7)2 (MII = Ni,Co)

Raman and IR spectra of polycrystalline Ni₃Pb(P₂O₇)₂ and Co₃Pb(P₂O₇)₂ have been recorded and analyzed. The internal modes are assigned in terms of PO₃ and POP vibrations. The results point to a bent POP bridge configuration in Co₃Pb(P₂O₇)₂ as in Ni₃Pb(P₂O₇)₂. In the cobalt compound, the P₂O⁴⁻₇ ions are distorted. Non-coincidence of the majority of the Raman and IR bands confirms a centrosymmetric structure for Ni₃Pb(P₂O₇)₂, and Co₃Pb(P₂O₇)₂. The POP bridge angle is slightly higher in the cobalt compound than in the nickel compound.     

Basische Carbonate des Dysprosiums: Dy2O2(CO3) und Dy(OH)(CO3)

Basic Carbonates of Dysprosium: Dy₂O₂(CO₃) and Dy(OH)(CO₃) Single crystals of the basic carbonates Dy₂O₂(CO₃) and Dy(OH)(CO₃) are obtained via hydrothermal synthesis from a mixture of DyCl₃ · 6 H₂O and K₂CO₃ and Cs₂CO₃, respectively, as well as CO₂ and H₂O in a steel autoclave at 480 and 400 °C, respectively. The crystal structures are isotypic with those of II‐Nd₂O₂(CO₃) and B–Nd(OH)(CO₃), respectively; Dy₂O₂(CO₃): hexagonal, P6₃/mmc, Z = 2; a = 386.9(2), c = 1516.3(3) pm; Dy(OH) · (CO₃): hexagonal, P‐6, Z = 18; a = 1201.0(1), c = 971.8(9) pm.     

[Co7(μ4‐O)2(O2C–CH3)8(NCO)2(HNPEt3)4] · 2 OEt2, ein siebenkerniger Komplex mit vier‐, fünf‐ und sechsfach koordinierten Cobalt‐Atomen

[Co₇(μ₄‐O)₂(O₂C–CH₃)₈(NCO)₂(HNPEt₃)₄] · 2 OEt₂, a Seven Nuclearity Complex with Four, Five, and Sixfold Coordinated Cobalt Atoms The title compound was prepared from cobalt(II) acetate with Me₃SiNPEt₃ at 180 °C and subsequent crystallization from diethylether to give blue, moisture sensitive single crystals, which were characterized by a crystal structure determination. Space group P2₁/n, Z = 2, lattice dimensions at –80 °C: a = 1544.0(1), b = 1522.1(2), c = 1702.0(1) pm, β = 103.911(10)°, R = 0.0490. [Co₇(μ₄‐O)₂(O₂C–CH₃)₈(NCO)₂ · (HNPEt₃)₄] has a centrosymmetric cluster‐like structure in which the octahedrally coordinated central cobalt atom is connected with the remaining six cobalt atoms via two μ₄‐oxygen atoms as well as via four bridging acetato groups to form a Co(Co)₆ octahedral skeleton. Four of the peripheric cobalt atoms have a distorted trigonal‐bipyramidal coordination sphere, the other two cobalt atoms are tetrahedrally coordinated. The latter are connected with the nitrogen atoms of the cyanato groups.     

Effect of Al2O3 -coating on the electrochemical performances of Li3V2(PO4)3/C cathode material

The effect of Al₂O₃ -coating on Li₃V₂(PO₄)₃/C cathode material for lithium-ion batteries has been investigated. The crystalline structure and morphology of the synthesized powders have been characterized by XRD, SEM, and HRTEM, and their electrochemical performances are evaluated by CV, EIS, and galvanostatic charge/discharge tests. It is found that Al₂O₃ -coating modification stabilizes the structure of the cathode material, decreases the polarization of electrode and suppresses the rise of the surface film resistance. Electrochemical tests indicate that cycling performance and rate capability of Al₂O₃-coated Li₃V₂(PO₄)₃/C are enhanced, especially at high rates. The Al₂O₃-coated material delivers discharge capacity of 123.03 mAh g^?1 at 4 C rate, and the capacity retention of 94.15 % is obtained after 5 cycles. The results indicate that Al₂O₃ -coating should be an effective way to improve the comprehensive properties of the cathode materials for lithium-ion batteries.     

A quarter of a century after its synthesis and with >200 papers based on its use, `Co(CO3)0.5(OH)·0.11H2O′ proves to be Co6(CO3)2(OH)8·H2O from synchrotron powder diffraction data

The successful attempt to solve the crystal structure of Co(CO₃)_0.5(OH)·0.11H₂O (denoted CCH ), based on synchrotron powder diffraction data, leads to a drastic revision of the chemical formula to Co₆(CO₃)₂(OH)₈·H₂O [hexacobalt(II) bis(carbonate) octahydroxide monohydrate] and to a hexagonal cell instead of the orthorhombic cell suggested previously [Porta et al. (1992). J. Chem. Soc. Faraday Trans. 88 , 311–319]. This results in a new structure‐type related to malachite involving infinite chains of [CoO₆] octahedra sharing edges along a short c axis, delimiting tunnels having a three‐branched star section. All reports discussing cobalt hydroxycarbonates ( CCH ) without any structural knowledge and especially its topotactic decomposition into Co₃O₄ have, as a result, to be reconsidered.     

Cathodic performance of anatase (TiO2)-coated Li(Ni0.8Co0.2)O2

We report the use of Li(Ni_0.8Co_0.2)O₂ coated with different amounts of anatase (TiO₂) as a cathode material for lithium-ion cells. Electrochemical behavior is modified owing to coating and/or incorporation of titanium into the first few surface layers of Li(Ni_0.8Co_0.2)O₂. Compositions with molar concentrations of x=0.005 and 0.02 exhibit better capacity retention than the mother compound (40 cycles, 0.5 C rate, 2.75–4.30 V). Electronic Publication     

An ESR study of photochemical reactions of Co2(CO)6(PBu3)2 with quinones and phenothiazine

The photochemical reactions of Co₂(CO)₆(PBu₃)₂ with various quinones and phenothiazine were studied by ESR. The results indicate that the photolysis of Co₂(CO)₆(PBu₃)₂ in the presence of o-quinones led to the observation of an ESR spectrum, showing a broad 8 or 12 groups of hyperfine lines due to interaction with cobalt (Co, 1 = 7/2). The results show that with o-quinones the cobalt radical adducts are formed via metal chelation to the carbonyl oxygens. However, when Co₂(CO)₆(PBu₃)₂ was irradiated in the presence of p-quinones, only the para-semiquinone radicals were observed. The photolysis of Co₂(CO)₆(PBu₃)₂ with phenothiazine in toluene yields phenothiazine radical. The sixteen and eighteen electrons rule have been used to account for these observations.     

Cobalt(II) complexes with aminopolycarboxylate 1,3-pdta-type ligands: synthesis and characterization of trans(O6)-[Mg(H2O)6][CoII(1,3-pddadp)]·H2O

Starting from Ba₂(1,3-pddadp)·8H₂O (1,3-pddadp=1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) and CoSO₄, a new hexadentate [Co^II(1,3-pddadp)]²⁻ complex has been prepared. The trans(O₆) geometry of this complex was confirmed by comparison of its i.r. and u.v.–vis. spectra with those of [Co^II(1,3-pdta)]²⁻ (1,3-pdta is the 1,3-propanediaminetetraacetate ion) and trans(O₆)-[Co^III(1,3-pddadp)]⁻ complexes of known X-ray crystal structure. Magnetic and electrolytic conductivity properties of these complexes have also been discussed.     

Thermal behaviour,surface properties and vibrational spectroscopic studies of the synthesized Co3xNi3−3x(PO4)2·8H2O (0 ≤ x ≤ 1)

Co_3xNi_3−3x(PO₄)₂·8H₂O (x = 1, 0.8, 0.6, 0.4, 0.2, and 0) were synthesized via simple wet chemical reaction and energy saving route method. The final decomposition products of hydrates are corresponding anhydrous tri(cobalt nickel) diphosphates. The metal and water contents of the synthesized hydrates were confirmed by AAS and TG/DTG/DTA techniques, respectively. The observed metal and water contents agree well with the formula of the title compounds. The crystal structures and lattice parameters as well as crystallite sizes of the studied compounds were determined using XRD data. The results from XRD and TG/DTG/DTA techniques confirmed that Co_3xNi_3−3x(PO₄)₂·8H₂O at all ratios were the single phase. The FTIR spectra of studied compounds were recorded and assigned. The thermal behaviours of single and binary tri(cobalt nickel) diphosphate octahydrates were studied for the first time. The morphologies of the studied compounds were investigated by using the SEM technique. The micrographs of all studied compounds exhibited the thin plated morphology. The surface area and the pore size data of anhydrous forms were measured by N₂ adsorption at −190 °C according to the BET method. The anhydrous forms of binary metal phosphate at x = 0.8, Co_2.4Ni_0.6(PO₄)₂, exhibits the highest surface area and expects to improve the catalytic activity.     

THERMAL DEHYDRATION OF BARIUM AND CALCIUM TRIMETAPHOSPHATE HEXAHYDRATES: Ba3(P3O9)26H2O AND Ca3(P3O9)26H2O

Abstract

Ba₃(P₃O₉)₂6H₂O and Ca₃(P₃O₉)₂6H₂O have mobile H₂O's which, under a dynamic vacuum of about 0.133 Pa, leave the lattice without disrupting it. Under water-vapor pressure, dehydration is accompanied by hydrolysis of P₃O₉ ^3- rings. The final product of dehydration is the β polyphosphate.     

水热合成Co3O4的制备参数调变及其催化分解N2O性能

以十六烷基三甲基溴化胺（CTAB）为模板剂,通过调变CTAB浓度水热合成了氧化钴前驱体,焙烧制得棒状形貌的Co₃O₄,在其表面浸渍K₂CO₃溶液制得K改性的Co₃O₄催化剂,用于N₂O分解。用X射线衍射（XRD）、N₂物理吸附（BET）、扫描电镜（SEM）、X射线光电子能谱（XPS）、H₂程序升温还原（H₂-TPR）和O₂程序升温脱附（O₂-TPD）等技术对催化剂进行了表征,考察了CTAB/钴及尿素/钴物质的量比等制备参数对Co₃O₄催化分解N₂O活性的影响。结果表明,CTAB浓度为0.05 mol/L、CTAB/钴离子物质的量比为1、尿素/钴离子物质的量比为4时,所制备的Co₃O₄催化剂具有较高的N₂O分解活性,而K改性可以进一步提升其催化性能。K改性的Co₃O₄在有氧有水气氛中400℃下进行N₂O分解反应,50 h后N₂O转化率仍保持在91%以上。     

Syntheses,characterizations and crystal structures of two new complexes, [Co2(CH2 =C(CH3)CO2)4(phen)2(H2O)2] and [Pb2(CH2 =C(CH3)CO2)4(phen)2]

Two new complexes, [Co₂(CH₂=C(CH₃)CO₂)₄(phen)₂(H₂O)₂] (1) and [Pb₂(CH₂=C(CH₃)CO₂)₄(phen)₂] (phen = 1,10-phenanthroline) (2), have been synthesized and structurally characterized by single crystal X-ray diffraction methods. There are two cocrystallized conformers of [Co(CH₂=C(CH₃)CO₂)₂(phen)(H₂O)] in the asymmetric unit of 1 with the Co atoms displaying similar coordination modes. In the asymmetric unit of 2, there exist two crystallographically independent [Pb(CH₂=C(CH₃)CO₂)₂(phen)] molecules with the Pb atoms showing completely different coordination geometries. Weak intermolecular interactions such as hydrogen bonding and π–π stacking are responsible for the supramolecular assembly and stabilization of the crystal structures of 1 and 2. The complexes are characterized by elemental analysis, IR spectra, and UV–Vis spectra. The fluorescent properties of 2 are also discussed.     

Chemical Processing of Potassium Substituted (Pb0.6Ba0.4)Nb2O6 Powders and Thin Films Through Metallo-Organics

Highly oriented tungsten bronze K_0.4(Pb_0.6Ba_0.4)_0.8Nb₂O₆ ferroelectric thin films have been prepared from metal alkoxides and metal acetate by chemical process. The formation of solid solution with potassium was found to be very effective to form the tungsten bronze phase at lower temperatures compared with (Pb_0.6Ba_0.4)Nb₂O₆. The amount of potassium in the composition of K_x(Pb_0.6Ba_0.4)_{1 – x/2}Nb₂O₆ [0 x 0.4] is also important to crystallize in the tungsten bronze phase. K_0.4(Pb_0.6Ba_0.4)_0.8Nb₂O₆ films with c-axis preferred orientation were successfully synthesized on MgO(1 0 0) and Pt(1 0 0)/MgO(1 0 0) substrates above 700°C. KPBN60 thin film on Pt(1 0 0)/MgO(1 0 0) showed a remnant polarization of 20 C/cm² and a coercive field of 140 kV/cm at –150°C.     

Synthesis of Co3O4 nanorod bunches from a single precursor Co(CO3)0.35Cl0.20(OH)1.10

Co₃O₄ nanorods were successfully synthesized from a single precursor via a thermal decomposition and oxidization route. The precursor used was Co(CO₃)_0.35Cl_0.20(OH)_1.10, which was prepared by a hydrothermal reaction using CoCl₂⋅6H₂O with CO(NH₂)₂ at 95–120 °C. Both the precursor and the as-prepared Co₃O₄ were characterized with XRD, TEM, SEM, TGA and XPS. The precursor, as well as Co₃O₄, was found to be composed of nanorods that were radially bunched. The Co₃O₄ nanorods obtained through a thermal treatment at 300 °C for 5 h were found to have a porous structure.     

Synthesis, Characterization and Crystal Structure of a New Cobalt Phosphomolybdate that Contains [(Mo16O32)Co16(H2O)18(PO4)6(HPO4)18] Wheels

A new compound, [Co(H₂O)₆][{Co₂(H₂O)₆}{Co(H₂PO₄)₂}{(PO₄)₆(HPO₄)₁₈(Mo₁₆O₃₂)Co₁₆(H₂O)₁₈}] · 23H₂O (1), has been prepared under mild hydrothermal conditions and structurally characterized by elemental analyses, i.r. spectrum, XPS spectrum and single-crystal X-ray diffraction. Compound (1) consists of [(Mo₁₆O₃₂)Co₁₆- (H₂O)₁₈(PO₄)₆(HPO₄)₁₈] wheel-shape clusters as the structural motif, which are covalently linked by [Co₂(H₂O)₆] and [Co(H₂PO₄)₂] fragments to form a two-dimensional layer framework. It is the first time that such wheels have been linked by both mononuclear and dimeric Co^II octahedra. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Degradation of 4-nitrophenol by electrocatalysis and advanced oxidation processes using Co3O4@C anode coupled with simultaneous CO2 reduction via SnO2/CC cathode

Herein, we prepared novel three-dimensional (3D) gear-shaped Co₃O₄@C (Co₃O₄ modified by amorphous carbon) and sheet-like SnO₂/CC (SnO₂ grow on the carbon cloth) as anode and cathode to achieve efficient removal of 4-nitrophenol (4-NP) in the presence of peroxymonosulfate (PMS) and simultaneous electrocatalytic reduction of CO₂, respectively. In this process, 4-NP was mineralized into CO₂ by the Co₃O₄@C, and the generated CO₂ was reduced into HCOOH by the sheet-like SnO₂/CC cathode. Compared with the pure Co0.5 (Co₃O₄ was prepared using 0.5 g urea) with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP (60 mL, 10 mg/L) increased from 74.5%–85.1% in 60 min using the Co0.5 modified by amorphous carbon (Co0.5@C). Furthermore, when the voltage of 1.0 V was added in the anodic system of Co0.5@C with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP increased from 85.1%–99.1% when Pt was used as cathode. In the experiments of 4-NP degradation coupled with simultaneous electrocatalytic CO₂ reduction, the degradation efficiency of 4-NP was 99.0% in the anodic system of Co0.5@C with addition of PMS (30 mg, 0.5 g/L), while the Faraday efficiency (FE) of HCOOH was 24.1 % at voltage of −1.3 V using the SnO₂/CC as cathode. The results showed that the anode of Co₃O₄ modified by amorphous carbon can markedly improve the degradation efficiency of 4-NP, while the cathode of SnO₂/CC can greatly improve the FE and selectivity of CO₂ reduction to HCOOH and the stability of cathode. Finally, the promotion mechanism was proposed to explain the degradation of organic pollutants and reduction of CO₂ into HCOOH in the process of electrocatalysis coupled with advanced oxidation processes (AOPs) and simultaneous CO₂ reduction.     

Sequential Synthesis of 3 d–3 d, 3 d–4 d,and 3 d–5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions

The Co₇(AlePy)₂ polyoxometalate, which encloses a {(PW₉)₂Co^II₇} core covalently bound to two free aminopyridine groups through bisphosphonate ligands ( AlePy ), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc ( Co₇(AlePyZn)₂ ), cobalt/palladium ( Co₇(AlePyPd)₂ ), and cobalt/platinum ( Co₇(AlePyPt)₂ ) species. A composite based on the water‐insoluble precious metal‐free Co₇(AlePyZn)₂ compound and the low‐cost carbon material Vulcan XC‐72 has been selected as a cathode material ( Co₇Zn/C ) for oxygen reduction reaction studies. The electrocatalytic performances of the Co₇Zn/C hybrids were assessed at neutral and basic pH, showing that Co₇Zn/C exhibits high selectivity for the four‐electron reduction of O₂. Moreover, its durability is superior to that of a commercial Pt/C catalyst with 20 % loading. Also, comparative studies performed in the presence of methanol have indicated that Co₇Zn/C has a much better tolerance to the crossover effect than Pt/C . Altogether, these results indicate for the first time that, even in neutral media, polyoxometalate/carbon composites can represent low‐cost oxygen reduction catalysts that can function stably, for a long time, and with high performance.     

Tetradecacobalt(II)‐Containing 36‐Niobate [Co14(OH)16(H2O)8Nb36O106]20− and Its Photocatalytic H2 Evolution Activity

A gigantic Co₁₄‐containing 36‐niobate, Na₁₂K₈[Co₁₄(OH)₁₆(H₂O)₈Nb₃₆O₁₀₆] ? 71H₂O ( 1 ), has been prepared by the hydrothermal method and structurally characterized. Polyanion [Co₁₄(OH)₁₆(H₂O)₈Nb₃₆O₁₀₆]^20? ( 1 a ) comprises a central Co₇ core, surrounded by another seven isolated Co²⁺ ions and six Lindqvist‐type (Nb₆O₁₉) hexaniobate fragments. This is the first example of a high‐nuclear cobalt‐cluster‐containing polyoxoniobate. The photocatalytic H₂ evolution activity of Pt‐loaded 1 was observed in methanol solution under irradiation using a 300 W Xe lamp.     

Biomimetic Synthesis of Metal Ion‐Doped Hierarchical Crystals Using a Gel Matrix: Formation of Cobalt‐Doped LiMn2O4 with Improved Electrochemical Properties through a Cobalt‐Doped MnCO3 Precursor

We have synthesized spinel type cobalt‐doped LiMn₂O₄ (LiMn_2?yCo_yO₄, 0≤y≤0.367), a cathode material for a lithium‐ion battery, with hierarchical sponge structures via the cobalt‐doped MnCO₃ (Mn_1‐xCo_xCO₃, 0≤x≤0.204) formed in an agar gel matrix. Biomimetic crystal growth in the gel matrix facilitates the generation of both an homogeneous solid solution and the hierarchical structures under ambient condition. The controlled composition and the hierarchical structure of the cobalt‐doped MnCO₃ precursor played an important role in the formation of the cobalt‐doped LiMn₂O₄. The charge–discharge reversible stability of the resultant LiMn_1.947Co_0.053O₄ was improved to ca. 12 % loss of the discharge capacity after 100 cycles, while pure LiMn₂O₄ showed 24 % loss of the discharge capacity after 100 cycles. The parallel control of the hierarchical structure and the composition in the precursor material through a biomimetic approach, promises the development of functional materials under mild conditions.