Beijing University of Technology

About: Beijing University of Technology is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: Microstructure & Laser. The organization has 31929 authors who have published 31987 publications receiving 352112 citations. The organization is also known as: Běijīng Gōngyè Dàxué & Beijing Polytechnic University.

Delicate control of crystallographic facet-oriented Cu2O nanocrystals and the correlated adsorption ability

Abstract: In this work, we demonstrate the systematic and delicate geometry control of Cu2O nanocrystals by taking advantage of the selective surface stabilization effect. A variety of Cu2O architectures, evolved from cubes through truncated cubes, cubooctahedrons, truncated octahedrons and finally to octahedrons, were achieved by simply adjusting the added PVP. Based on the understanding of the intrinsic structural features of the cuprite Cu2O and PVP, we elucidated the underlying shape evolution mechanism. The as-prepared products demonstrated a crystallography-dependent adsorption ability with methyl orange (MeO) as the pollutant. With the advantage of a low cost, high yield and straightforward procedure without pre-formed crystals as sacrificial templates, this method may provide a good starting point for the study of shape construction and morphology-dependent properties of other nanocrystals.

Boron- and Nitrogen-Doped Graphene Quantum Dots/Graphene Hybrid Nanoplatelets as Efficient Electrocatalysts for Oxygen Reduction

Abstract: The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media.

Significantly enhanced recoverable energy storage density in potassium–sodium niobate-based lead free ceramics

Abstract: Ceramic-based dielectric materials are regarded as the best candidates for advanced pulsed power capacitors because of their excellent mechanical and thermal properties. Nevertheless, lead-free bulk ceramics show relatively low recoverable energy storage density (Wrec < 2 J cm−3) owing to their low dielectric breakdown strength (DBS < 200 kV cm−1). In order to significantly increase Wrec, we proposed a strategy (compositions drive the grain size to submicrometer) to improve the DBS of lead-free ceramics. In this work, (1 − x)(K0.5Na0.5)NbO3–xSrTiO3 (KNN–ST) ceramics were chosen as a representative to verify the validity of this strategy. The (1 − x)KNN–xST ceramics (x = 0.15 and 0.20) with submicrometer grains (about 0.3 μm) were prepared using pressureless solid state sintering. A large Wrec (4.03 J cm−3) and DBS (400 kV cm−1 with a thickness of 0.2 mm) were achieved for 0.85KNN–0.15ST ceramics. The value of 4.03 J cm−3 is superior to all other Wrec in lead-free bulk ceramics and 2–3 times larger than that of other lead-free bulk ceramics. A large Wrec (3.67 J cm−3) and energy storage efficiency (72.1%) were simultaneously achieved for 0.80KNN–0.20ST ceramics. The results confirm that the (1 − x)KNN–xST ceramics (x = 0.15 and 0.20) are desirable materials for advanced pulsed power capacitors. The findings in this study could push the development of a series of KNN-based ceramics with enhanced DBS and Wrec in the future. On the other hand, this work could broaden the applications of KNN materials in a new field.