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.

A highly efficient (>6%) Cd1−xMnxSe quantum dot sensitized solar cell

Abstract: Quantum dot sensitized solar cells (QDSCs) have attracted considerable attention recently and become promising candidates for realizing a cost-effective solar cell. The design and synthesis of quantum dots (QDs) for achieving high photoelectric performance is an urgent need imposed on scientists. Here, we have succeeded in designing a QDSC with a high efficiency η of 6.33% based on Cd0.8Mn0.2Se quantum dots by facile chemical bath deposition (CBD). The effects of Mn2+ ions on the physical, chemical, and photovoltaic properties of the QDSCs are investigated. The Mn2+ ions doped into QDs can increase the light harvesting to produce more excitons. In addition, the Mn2+ dopant also raises the conduction band of CdSe, accelerates the electron injection kinetics and reduces the charge recombination, improving the charge transfer and collection. The increase of the efficiencies of light-harvesting, charge-transfer and charge-collection results in the improvement of the quantum efficiency of the solar cells. The power conversion efficiency of the solar cell is increased to 6.33% (Voc = 0.58 V, Jsc = 19.15 mA cm−2, and FF = 0.57).

Two-Dimensional Covalent Organic Frameworks with Cobalt(II)-Phthalocyanine Sites for Efficient Electrocatalytic Carbon Dioxide Reduction.

Abstract: The rapid development in synthesis methodology and applications for covalent organic frameworks (COFs) has been witnessed in recent years. However, the synthesis of highly stable functional COFs still remains a great challenge. Herein two-dimensional polyimide-linked phthalocyanine COFs (denoted as CoPc-PI-COF-1 and CoPc-PI-COF-2) have been devised and prepared through the solvothermal reaction of the tetraanhydrides of 2,3,9,10,16,17,23,24-octacarboxyphthalocyaninato cobalt(II) with 1,4-phenylenediamine and 4,4'-biphenyldiamine, respectively. The resultant CoPc-PI-COFs with a four-connected sql net exhibit AA stacking configurations according to powder X-ray diffraction studies, showing permanent porosity, thermal stability above 300 °C, and excellent resistance to a 12 M HCl aqueous solution for 20 days. Current-voltage curves reveal the conductivity of CoPc-PI-COF-1 and CoPc-PI-COF-2 with the value of 3.7 × 10-3 and 1.6 × 10-3 S m-1, respectively. Due to the same Co(II) electroactive sites together with similar permanent porosity and CO2 adsorption capacity for CoPc-PI-COFs, the cathodes made up of COFs and carbon black display a similar CO2-to-CO Faradaic efficiency of 87-97% at applied potentials between -0.60 and -0.90 V (vs RHE) in 0.5 M KHCO3 solution. However, in comparison with the CoPc-PI-COF-2&carbon black electrode, the CoPc-PI-COF-1 counterpart provides a larger current density (jCO) of -21.2 mA cm-2 at -0.90 V associated with its higher conductivity. This cathode also has a high turnover number and turnover frequency, amounting to 277 000 and 2.2 s-1 at -0.70 V during 40 h of measurement. The present result clearly discloses the great potential of 2D porous crystalline solids in electrocatalysis.

Enhanced electric displacement induces large energy density in polymer nanocomposites containing core–shell structured BaTiO3@TiO2 nanofibers

Abstract: High energy density polymer nanocomposites are quite promising for film capacitors and many other electronic devices. In this study, the promising strategy is to increase the electric displacement in high breakdown strength nanocomposites with low loading nanofillers. The core–shell structured barium titanate@titanium dioxide nanofiber (BTO@TO-nf) reported herein is designed based on interfacial engineering and prepared using coaxial electrospinning. In the PVDF nanocomposites containing the core–shell nanofibers, the dielectric permittivity as well as the electric displacement increase significantly, due to the additional polarization induced by the charge shifting in the interfacial zone between BTO on the inside and TO on the outside, which contributes significantly to the electric displacement. In addition, the breakdown strength of the nanocomposite is maintained through the charge shifting being limited to the interfacial zone so it cannot form a percolation path in the matrix. A large discharged energy density of ca. 10.94 J cm−3 is achieved at a field of 360 kV mm−1 for the nanocomposite film with 3% volume fraction of BTO@TO-nf, which is higher than those of the referenced PVDF nanocomposites under the same electric field. The present study demonstrates the advantages of the core–shell structured nanofibers in improving the dielectric properties and provides a new way to enhance the energy density of polymer nanocomposites.