VSe_(2)/V_(2)C heterocatalyst with built-in electric field for efficient lithium-sulfur batteries:Remedies polysulfide shuttle and conversion kinetics

Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(Li PSs)undergo notorious shuttle effect,which seriously hinders the commercialization of Li-S batteries.Herein,a unique VSe_(2)/V_(2)C heterostructure with local built-in electric field was rationally engineered from V_(2)C parent via a facile thermal selenization process.It exquisitely synergizes the strong affinity of V_(2)C with the effective electrocatalytic activity of VSe_(2).More importantly,the local built-in electric field at the heterointerface can sufficiently promote the electron/ion transport ability and eventually boost the conversion kinetics of sulfur species.The Li-S battery equipped with VSe_(2)/V_(2)C-CNTs-PP separator achieved an outstanding initial specific capacity of 1439.1 m A h g^(-1)with a high capacity retention of 73%after 100 cycles at0.1 C.More impressively,a wonderful capacity of 571.6 mA h g^(-1)was effectively maintained after 600cycles at 2 C with a capacity decay rate of 0.07%.Even under a sulfur loading of 4.8 mg cm^(-2),areal capacity still can be up to 5.6 m A h cm^(-2).In-situ Raman tests explicitly illustrate the effectiveness of VSe_(2)/V_(2)C-CNTs modifier in restricting Li PSs shuttle.Combined with density functional theory calculations,the underlying mechanism of VSe_(2)/V_(2)C heterostructure for remedying Li PSs shuttling and conversion kinetics was deciphered.The strategy of constructing VSe_(2)/V_(2)C heterocatalyst in this work proposes a universal protocol to design metal selenide-based separator modifier for Li-S battery.Besides,it opens an efficient avenue for the separator engineering of Li-S batteries.

High-performance vertical GaN field-effect transistor with an integrated self-adapted channel diode for reverse conduction

A vertical GaN field-effect transistor with an integrated self-adapted channel diode(CD-FET)is proposed to improve the reverse conduction performance.It features a channel diode(CD)formed between a trench source on the insulator and a P-type barrier layer(PBL),together with a P-shield layer under the trench gate.At forward conduction,the CD is pinched off due to depletion effects caused by both the PBL and the metal-insulator-semiconductor structure from the trench source,without influencing the on-state characteristic of the CD-FET.At reverse conduction,the depletion region narrows and thus the CD turns on to achieve a very low turn-on voltage(V_(F)),preventing the inherent body diode from turning on.Meanwhile,the PBL and P-shield layer can modulate the electric field distribution to improve the off-state breakdown voltage(BV).Moreover,the P-shield not only shields the gate from a high electric field but also transforms part of C_(GD)to CGS so as to significantly reduce the gate charge(Q_(GD)),leading to a low switching loss(E_(switch)).Consequently,the proposed CD-FET achieves a low V_(F)of 1.65 V and a high BV of 1446 V,and V_(F),Q_(GD)and E_(switch)of the CD-FET are decreased by 49%,55%and 80%,respectively,compared with those of a conventional metal-oxide-semiconductor field-effect transistor(MOSFET).

Catalytic properties of Cu-Co catalysts supported on HNO_3-pretreated CNTs for higher-alcohol synthesis

HNO 3 -pretreated CNTs were employed as supports, and a special ultrasound-assisted impregnation method was designed to prepare supported Cu-Co catalysts for higher-alcohol synthesis from syngas. The catalysts used in this work were characterized by N 2 adsorption-desorption, TEM, XRD, H 2 -TPR, CO-TPD techniques. It was found that the pre-treatment procedure of CNTs remarkably promoted the catalytic properties of the Cu-Co/CNTs catalysts. For the Cu-Co catalyst supported on CNTs pre-treated by 68 wt% HNO 3 , some active components were introduced into the CNTs channels, their dispersions and the amount of strongly adsorbed CO-species were improved. The CO conversion and alcohol yield on the HNO 3 -pretreated Cu-Co/CNTs catalyst were increased by ～21% and ～69%, respectively, compared with those on the normal Cu-Co/CNTs catalyst.

A novel ferroelectric based on quinuclidine derivatives

The compound[(CH3)2 CH-C3 H17 N][CoBr4](1)based on quinuclidine derivatives was achieved by the solution synthetic method and characterized by elemental analysis,infrared spectroscopy,single-crystal X-ray structural analysis and dielectric measurement,respectively.Variable-temperature single-crystal X-ray diffraction suggested that the compound unde rwent the phase transition from the space group C2/c to Cc.The polarization curve was measured using the Sawyer-Tower circuit.The structural phase transitions of 1 was ascribed to the distortion of a[(CH3)2 CH-C3 H17N]2+cation from this inorganicorganic hybrid material[(CH3)2 CH-C3 H17N][CoBr4].The strong change in dielectric anomalies makes compound 1 a suitable candidate for promising switchable dielectric materials.This work represents a feasible strategy thought for the targeted harvesting of low temperature ferroelectrics.

A highly stable, luminescent and layered zinc(Ⅱ)-MOF:Iron(Ⅲ)/copper(Ⅱ) dual sensing and guest-assisted exfoliation

A highly stable and luminescent metal-organic framework(LMOF) with layered structure,namely,C6H4N5OZn(1) has been successfully achieved and fully characterized by single crystal X-ray diffraction,powder X-ray diffractions,fluorescence titration and thermogravimetry.This blue-light emitting compound 1 exhibit outstanding stability and can detect Fe3+ and Cu2+ in water specifically,presenting potential application in the field of fluorescent probe technology.Fluorescence titration experiments indicate that the detection of Fe3+ ions by 1 is more significant than that of Cu2+ ions in terms of Ksv value.Furthermore,guest-assisted exfoliation of layered MOF 1 is efficiently carried out through ether O—H hydrogen bond or π…π interactions between the layered host structure and intercalated guest molecules(4,4’-oxybisbenzoic acid and triphenylamine).Tyndal scattering was observed in the suspensions of obtained MOF nanosheets.This study shows that the compound 1 with unique metal ion sensing properties can be applied as a probe material in water pollution treatment field,but also opens up the opportunity for synthesizing luminescent MONs through the "bottom-up" guest intercalation methodology.