More than just an empty shell: Multishelled Co3O4 microspheres were synthesized as anode materials for lithium-ion batteries in high yield and purity. As their porous hollow multishell structure guarantees a shorter Li+ diffusion length and sufficient void space to buffer the volume expansion, their rate capacity, cycling performance, and specific capacity were excellent (1615.8 mA?h?g-1 in the 30th cycle for triple-shelled Co3O4; see graph).

/pdf/accurate-control-of-multishelled-co3o4-hollow-microspheres-1yxfmmp0zm.pdf

Accurate Control of Multishelled Co3O4 Hollow Microspheres as High-Performance Anode Materials in Lithium-Ion Batteries

Accurate Control of Multishelled Co 3 O 4 Hollow Microspheres as High- Performance Anode Materials in Lithium-Ion Batteries**

In this work, a novel hydrothermal route is developed to synthesize cobalt carbonate hydroxide, Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O. In this method, sodium chloride salt is utilized to organize single-crystalline nanowires into a chrysanthemum-like hierarchical assembly. The morphological evolution process of this organized product is investigated by examining different reaction intermediates during the synthesis. The growth and thus the final assembly of the Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O can be finely tuned by selecting preparative parameters, such as the molar ratio of the starting chemicals, the additives, the reaction time and the temperature. Using the flower-like Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O as a solid precursor, quasi-single-crystalline mesoporous Co{sub 3}O{sub 4} nanowire arrays are prepared via thermal decomposition in air. Furthermore, carbon can be added onto the spinel oxide by a chemical-vapor-deposition method using acetylene, which leads to the generation of carbon-sheathed CoO nanowire arrays (CoO rate at C). Through comparing and analyzing the crystal structures, the resultant products and their high crystallinity can be explained by a sequential topotactic transformation of the respective precursors. The electrochemical performances of the typical cobalt oxide products are also evaluated. It is demonstrated that tuning of the surface texture and the pore size of the Co{sub 3}O{sub 4} products is very important in lithium-ion-battery applications. The carbon-decorated CoO nanowire arrays exhibit an excellent cyclic performance with nearly 100% capacity retention in a testing range of 70 cycles. Therefore, this CoO rate at C nanocomposite can be considered to be an attractive candidate as an anode material for further investigation. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Mesoporous Co3O4 and CoO@C Topotactically Transformed from Chrysanthemum-like Co(CO3)0.5(OH)·0.11H2O and Their Lithium-Storage Properties

Flower power: Various mesoporous Co3O4 architectural structures (see figure) have been successfully prepared through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The electrochemical experiments showed that the specific capacitance of Co3O4 nanosheets was higher than that of Co3O4 microspheres in a KOH electrolyte.

Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co3O4, including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H2O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co3O4 electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co3O4 nanosheets was higher than that of the Co3O4 microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co3O4 nanosheet electrodes exhibited good rate capabilities, and maintained 93 % of the initial capacity at a current density of 5 mA cm−2 in a KOH (3 m) electrolyte solution. The results show that Co3O4 nanosheets might have potential applications as electrode materials for supercapacitors.

Controllable synthesis of mesoporous Co3O4 nanostructures with tunable morphology for application in supercapacitors.

A surface precipitation model for the sorption of cations on metal oxides

Surface analysis and the adsorption of Co(II) on goethite

Adsorption of selected metal ions including Pb(II) and Co(II) on mineral and clay substrates has been carried out. The chemical nature of the adsorbed metal ion has been examined using X-ray photoelectron spectroscopy (XPS). The interpretation of the XPS results indicates that lead (II) is oxidized to lead (IV) on β- and δ-MnO2, and Co(II) is present as Co(II) on illite. The oxidizing agent for Pb(II) is believed to be O2 or MnO2 and a reaction process consistent with the XPS results has been proposed.

C. V. Schenck

Papers

Surface analysis and the adsorption of Co(II) on goethite

X-Ray Photoelectron Spectroscopic (XPS) Studies on the Chemical Nature of Metal Ions Adsorbed on Clays and Minerals