Yitai Qian

Bio: Yitai Qian is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Anode & Nanocrystalline material. The author has an hindex of 108, co-authored 1175 publications receiving 50350 citations. Previous affiliations of Yitai Qian include Jiangsu University & Wenzhou University.

High electrochemical performance of monodisperse NiCo₂O₂ mesoporous microspheres as an anode material for Li-ion batteries

Abstract: Binary metal oxides have been regarded as ideal and potential anode materials, which can ameliorate and offset the electrochemical performance of the single metal oxides, such as reversible capacity, structural stability and electronic conductivity. In this work, monodisperse NiCo2O4 mesoporous microspheres are fabricated by a facile solvothermal method followed by pyrolysis of the Ni0.33Co0.67CO3 precursor. The Brunauer–Emmett–Teller (BET) surface area of NiCo2O4 mesoporous microspheres is determined to be about 40.58 m2 g–1 with dominant pore diameter of 14.5 nm and narrow size distribution of 10–20 nm. Our as-prepared NiCo2O4 products were evaluated as the anode material for the lithium-ion-battery (LIB) application. It is demonstrated that the special structural features of the NiCo2O4 microspheres including uniformity of the surface texture, the integrity and porosity exert significant effect on the electrochemical performances. The discharge capacity of NiCo2O4 microspheres could reach 1198 mA h g–1...

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

Abstract: 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.

Nanoscale Magnesium Hydroxide and Magnesium Oxide Powders: Control over Size, Shape, and Structure via Hydrothermal Synthesis

Abstract: Mg(OH)2 nanocrystallines with rod-, tube-, needle-, or lamella-like morphologies have been synthesized by a hydrothermal reaction using different magnesium precursors and solvents as the reactants. The products appeared to have narrow size distributions with a monodisperse nature. Subsequent thermal decomposition at 450 °C gave nanosized MgO, which preserved well the morphological features of the Mg(OH)2 samples. The specific surface areas of the MgO samples were determined by the BET technique, which gave a feature of high surface area generally larger than 100 m2/g. The channels formed in the thermal dehydroxylation process may account for this feature of the MgO nanocrystallines.

MoSe2‐Covered N,P‐Doped Carbon Nanosheets as a Long‐Life and High‐Rate Anode Material for Sodium‐Ion Batteries

Abstract: MoSe2 grown on N,P-co-doped carbon nanosheets is synthesized by a solvothermal reaction followed with a high-temperature calcination. This composite has an interlayer spacing of MoSe2 expanded to facilitate sodium-ion diffusion, MoSe2 immobilized on carbon nanosheets to improve charge-transfer kinetics, and N and P incorporated into carbon to enhance its interaction with active species upon cycling. These features greatly improve the electrochemical performance of this composite, as compared to all the controls. It presents a specific capacity of 378 mAh g−1 after 1000 cycles at 0.5 A g−1, corresponding to 87% of the capacity at the second cycle. Ex situ Raman spectra and high-resolution transmission electron microscopy images confirm that it is element Se, rather than MoSe2, formed after the charging process. The interaction of the active species with modified carbon is simulated using density functional theory to explain this excellent stability. The superior rate capability, where the capacity at 15 A g−1 equals ≈55% of that at 0.5 A g−1, could be associated with the significant contribution of pseudocapacitance. By pairing with homemade Na3V2(PO4)3/C, this composite also exhibits excellent performances in full cells.

A facile route to synthesize multiporous MnCo2O4 and CoMn2O4 spinel quasi-hollow spheres with improved lithium storage properties

Abstract: A facile and general way for the synthesis of porous and hollow complex oxides is highly desirable owing to their significant applications for energy storage and other fields. In this contribution, uniform Mn0.33Co0.67CO3 and Co0.33Mn0.67CO3 microspheres are firstly fabricated solvothermally just by tuning the molar ratio of Mn and Co. Subsequently, the growth of multiporous MnCo2O4 and CoMn2O4 quasi-hollow microspheres by topotactic chemical transformation from the corresponding precursors are realized through a non-equilibrium heat treatment process. Topotactic conversion further demonstrated that the much larger CoMn2O4 pores than those of MnCo2O4 are possibly due to the longer transfer distance of ions. When evaluated as anode materials for LIBs (lithium ion batteries), after 25 cycles at a current density of 200 mA g−1, the resultant MnCo2O4 and CoMn2O4 quasi-hollow microspheres possessed reversible capacities of 755 and 706 mA h g−1, respectively. In particular, the MnCo2O4 samples could deliver a reversible capacity as high as 610 mA h g−1 even at a higher current density of 400 mA g−1 with excellent electrochemical stability after 100 cycles of testing, indicating its potential application in LIBs. We believe that such good performance results from the appropriate pore size and quasi-hollow nature of MnCo2O4 microspheres, which can effectively buffer the large volume variation of anodes based on the conversion reaction during Li+ insertion/extraction. The present strategy is simple but very effective, and due to its versatility, it can be extended to other binary, even ternary complex metal oxides with high-performance in LIBs.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

Chemistry and properties of nanocrystals of different shapes.

Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Semiconductor-based Photocatalytic Hydrogen Generation

Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519