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752 results on '"Deng, Youquan"'

158. CoO@Co and N-doped mesoporous carbon composites derived from ionic liquids as cathode catalysts for rechargeable lithium–oxygen batteries.

Author

Liu, Shimin, He, Yude, Ma, Xiangyuan, Lu, Liujin, Deng, Youquan, Ni, Wenpeng, and Fei, Yuqing

Abstract

The catalytic activity of a cathode material plays a vital role in determining the electrochemical performance of Li–O2 batteries. Herein, N-doped mesoporous carbon-supported CoO@Co nanoparticles are prepared in situ using the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrachlorocobalt ([BMIm]2[CoCl4]) as the precursor with silica as the hard template. The material was characterized by TGA, BET, XRD, TEM, XPS, and H2-TPR. After exposure to air, the species on the surface of the Co is CoO, as verified by XPS. The pore size is about 2 nm, and the CoO@Co nanoparticles were irregularly shaped and sized in the range of 20–300 nm, which may have been due to the aggregation of ultrafine nanoparticles. The existence of an interaction between the CoO@Co nanoparticles and the N-doped support is confirmed by XPS and H2-TPR. The catalyst shows superior activity for oxygen evolution reaction (OER) manifested in its lower charge potential (3.75 V at the current density of 100 mA g−1). Enhanced performances in coulombic efficiency, rate capability, and cycling stability (55 cycles) are also realized. Finally, these improvements, with the exception of the catalytic activity of CoO, may benefit from the interaction between the carbon supporter and the CoO@Co nanoparticles. [ABSTRACT FROM AUTHOR]

Published
2016
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159. CO2 activation and fixation: highly efficient syntheses of hydroxy carbamates over Au/Fe2O3.

Author

Shang, Jianpeng, Guo, Xiaoguang, Li, Zuopeng, and Deng, Youquan

Subjects
CARBAMATES synthesis, CHEMICAL synthesis, EPOXY compounds, AMINES, NUCLEOPHILIC addition (Chemistry)
Abstract

This paper reports an effective route for the syntheses of hydroxy carbamates from the reaction of CO2, epoxides and amines catalyzed by a Au/Fe2O3 catalyst. Under the optimized reaction conditions, various hydroxy carbamates were successfully synthesized with 92–98% isolated yields. The catalyst could be reused for several runs without deactivation. A plausible reaction mechanism was proposed by which the hydroxy carbamate was formed through an ammonium carbamate intermediate and the catalyst mainly promoted further nucleophilic addition between the epoxide and ammonium carbamate. [ABSTRACT FROM AUTHOR]

Published
2016
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175. Dynamic Three-Dimensional Nanowetting Behavior of Imidazolium-Based Ionic Liquids Probed by Molecular Dynamics Simulation

Author

Guan, Yongji, Shao, Qunfeng, Chen, Wenqiong, Liu, Shimin, Zhang, Xiaoping, and Deng, Youquan

Abstract

The dynamic three-dimensional nanowetting behavior of nanodroplets of three kinds of 1-ethyl-3-methylimidazolium ionic liquids (ILs) with radii between 10 and 30 Å is probed by molecular dynamics (MD) simulation on a solid silicon surface at temperatures ranging from 300 to 500 K. The simulation results show that contact angles change greatly and then tend to be saturated from 45° to 75° as the droplet radius of ILs varied from 10 to 20 Å and further to >20 Å. The values of the contact angle are anisotropic and could be 39.5° and 48.7° in the xand ydirections of the droplets spreading on the solid silicon surface when the radius of the IL droplet is 10 Å, and increasing the radius of the droplets can weaken the anisotropy of the contact angle. Further analysis of the interaction among cations, anions, and silicon suggests that the van der Waals (VDW) interaction of ions and silicon substrate varies from −56.5 to −53.5 kJ/mol per ion pair and silicon, and the Coulombic interaction of cations and anions varies from −265.3 to −282.0 kJ/mol per ion pair as the droplet radius of ILs ranged from 10 to 30 Å. Upon increasing the droplet radius, the imidazolium ring of the cation in the adsorbed layer is more nearly parallel to the silicon substrate, and this allows a very effective interaction with the silicon substrate. These changes in the structure of the adsorbed layer in the vicinity of the silicon surface and their effects on the structuring of ions in the bulk liquid layers above this strongly adsorbed layer lead to the difference of VDW and Coulombic interactions as the droplet radius of ILs varied from 10 to 30 Å. Additionally, the impact of the intrinsic viscosity and temperature on the nanowetting behavior of ILs is also investigated.

Published
2017
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176. Preparation of Carbon Nanotubes/Manganese Dioxide Composite Catalyst with Fewer Oxygen-Containing Groups for Li-O2Batteries Using Polymerized Ionic Liquids as Sacrifice Agent

Author

Ni, Wenpeng, Liu, Shimin, Fei, Yuqing, He, Yude, Ma, Xiangyuan, Lu, Liujin, and Deng, Youquan

Abstract

Considering the significant influence of oxygen-containing groups on the surface of carbon involved electrodes, a carbon nanotube (CNT)-based MnO2composite catalyst was synthesized following a facile method while using polymerized ionic liquids (PIL) as sacrifice agent. Herein, the PIL (polymerized hydrophobic 1-vinyl-3-ethylimidazolium bis ((trifluoromethyl)sulfonyl)imide) wrapped CNTs were prepared. The composite was applied to support MnO2by the treatment of KMnO4solution, taking advantage of the reaction between PIL and KMnO4, which excludes or suppresses the oxidation of CNTs, and the as-synthesized material with fewer oxygen-containing groups acted as a cathode catalyst for Li-O2batteries, directly avoiding the application of binders. The catalyst shows enhanced activity compared to that of the samples without PIL, as verified by the lower overpotential during discharging and charging (0.97 V at the current density of 100 mA g–1). Meanwhile, the performance parameters such as Coulombic efficiency and rate capability were also improved for the Li-O2battery utilizing this catalyst. Further, the formation of confined Li2O2particles could be responsible for the reduction of charge potential of Li-O2batteries due to the synergy effect of the intrinsic catalytic activity of MnO2and fewer oxygen functional groups on the catalyst surface.

Published
2017
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