University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

Atomic layer deposited TiO2 on a nitrogen-doped graphene/sulfur electrode for high performance lithium–sulfur batteries

Abstract: Nitrogen-doped graphene (NG) has been fabricated and used as a carbon matrix for sulfur impregnation to construct cathodes for lithium–sulfur (Li–S) batteries. Atomic layers of TiO2 were further deposited on the electrode and the thickness was controlled by adjusting the number of deposition cycles to 0, 5, 20 and 40. The results showed that all the surface modified electrodes demonstrate high capacity, good rate capability, and enhanced cyclability compared to the bare electrode. Specifically, the electrode contained 59% (by weight, wt%) sulfur and with the addition of 20 cycle-TiO2 it demonstrated a superior boost in the active sulfur utilization (discharge capacity: 1374 mA h g−1 at 0.1C). It also delivered initial discharge capacity up to 1069.5 mA h g−1 and 918.3 mA h g−1 after 500 cycles at 1C with an average coulombic efficiency of about 99.7%. Moreover, the capacity retention increased from 42% to 61% from 0.1C to 4C with the addition of 20 cycle-TiO2. The improved electrochemical performance could be attributed to the on-site TiO2 absorption for polysulfide retention as well as the charge transfer enhancement. Theoretical calculations revealed that TiO2 exhibits a strong binding energy for lithium polysulfide species. These results suggest that the TiO2 modified NG has potential to be used as a cathode for high-performance Li–S batteries.

Chemical Unit Cosubstitution and Tuning of Photoluminescence in the Ca2(Al1–xMgx)(Al1–xSi1+x)O7:Eu2+ Phosphor

Abstract: The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of "chemical unit cosubstitution" as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al(1-x)Mg(x))(Al(1-x)Si(1+x))O7:Eu(2+) solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu(2+) ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model.

Shape-Controlled Synthesis of Co2P Nanostructures and Their Application in Supercapacitors

Abstract: Co2P nanostructures with rod-like and flower-like morphologies have been synthesized by controlling the decomposition process of Co(acac)3 in oleylamine system with triphenylphosphine as phosphorus source. Investigations indicate that the final morphologies of the products are determined by their peculiar phosphating processes. Electrochemical measurements manifest that the Co2P nanostructures exhibit excellent morphology-dependent supercapacitor properties. Compared with that of 284 F g–1 at a current density of 1 A g–1 for Co2P nanorods, the capacitance for Co2P nanoflowers reaches 416 F g–1 at the same current density. Furthermore, an optimized asymmetric supercapacitor by using Co2P nanoflowers as anode and graphene as cathode is fabricated. It can deliver a high energy density of 8.8 Wh kg–1 (at a high power density of 6 kW kg–1) and good cycling stability with over 97% specific capacitance remained after 6000 cycles, which makes the Co2P nanostructures potential applications in energy storage/conver...