RESUMO
The severe shuttle effect of soluble polysulfides hinders the development of lithium-sulfur batteries. Herein, we develop a three-dimensionally ordered macro/mesoporous (3DOM) Nb2O5/Nb4N5 heterostructure, which combines the strong adsorption of Nb2O5 and remarkable catalysis effect of Nb4N5 by the promotion "adsorption-transformation" mechanism in sulfur reaction. Furthermore, the high electrocatalytic activity of Nb4N5 facilitates ion/mass transfer during the charge/discharge process. As a result, cells with the S-Nb2O5/Nb4N5 electrode delivered outstanding cycling stability and higher discharge capacity than its counterparts. Our work demonstrates a new routine for the multifunctional sulfur host design, which offers great potential for commercial high-performance lithium-sulfur batteries.
RESUMO
Organic-inorganic hybrid metal halides have attracted widespread attention as emerging optoelectronic materials, especially in solid-state lighting, where they can be used as single-component white-light phosphors for white light-emitting diodes. Herein, we have successfully synthesized a zero-dimensional (0D) organic-inorganic hybrid mixed-metal halide (Bmpip)2PbxSn1-xBr4 (0 < x < 1, Bmpip+ = 1-butyl-1-methyl-piperidinium, C10H22N+) that crystallizes in a monoclinic system in the C2/c space group. Pb2+ and Sn2+ form a four-coordinate seesaw structure separated by organic cations forming a 0D structure. For different excitation wavelengths, (Bmpip)2PbxSn1-xBr4 (0 < x < 1) exhibits double-peaked emission at 470 and 670 nm. The emission color of (Bmpip)2PbxSn1-xBr4 can be easily tuned from orange-red to blue by adjusting the Pb/Sn molar ratio or excitation wavelength. Representatively, (Bmpip)2Pb0.16Sn0.84Br4 exhibits approximately white-light emission with high photoluminescence quantum yield up to 39%. Interestingly, the color of (Bmpip)2PbxSn1-xBr4 can also be easily tuned by temperature, promising its potential for application in temperature measurement and indication. Phosphor-converted light-emitting diodes are fabricated by combining (Bmpip)2PbxSn1-xBr4 and 365 nm near-UV LED chips and exhibit high-quality light output.
RESUMO
Nonlinear-optical (NLO) crystals, which can regulate the laser wavelength through a cascading second-harmonic-generation technique, have been widely utilized in the field of optoelectronics. In this work, we grew the NLO borate crystal Rb3YB6O12 (RYBO) using the spontaneous crystallization method. RYBO crystallizes in a chiral trigonal space group of R32 with a new type of structural arrangement built from Y-O short chains and B5O10 groups. It is significantly different from the known structure of chemical analogues Rb3REB6O12 (RE = Nd, Eu) not only in the halved unit cell parameter but also in the Y-O connection manner. The NLO response of RYBO is about 0.8KDP, 8-fold larger than that of KB5O8·4H2O with the same B5O10 groups because of the coexistence of two NLO-active units of the distorted YO6 octahedra and B5O10 anions. Thanks to the short ultraviolet (UV) cutoff, RYBO may have potential NLO applications in the UV and even deep-UV spectral regions.
RESUMO
Graphitic carbon nitride (CN) is considered as a promising photocatalyst for solar energy conversion. However, low specific surface area and fast electrons and holes recombination restrict the photocatalytic applications of CN material. Herein, a nitrogen defect-rich and highly porous CN nanostructure (CN-LT) was prepared by combining two strategies, i.e., LiOH treatment and heat etching. The as-prepared nitrogen defect-rich porous CN-LT not only has a larger specific surface area, as compared with pristine CN, but also the photogenerated electron-hole separation was boosted remarkably. Using Pt as a co-catalyst and lactic acid aqueous solutions as sacrificial reagent under visible light irradiation (λ > 400 nm), the hydrogen evolution reaction (HER) rate for CN-LT (1.54 mmol h-1 g-1) was 19.25 times higher than that for pristine CN (0.08 mmol h-1 g-1). While subjecting pristine CN to heat etching under the same experimental conditions, excepting the use of LiOH (CN-T), an increase in HER rate of 7.5 times was obtained. Our current study may shed more light on the enhancement of the photocatalytic activity of bulk CN materials by altering their microstructure.
