Latest ArticlesGaining an understanding of the growth mechanism from single atoms to clusters and bulk materials continues to present a challenge. Thus, it is important to explore the evolving trends of clusters in the structure and properties during the size evolution. In this work, we report the synthesis and characterization of two medium-sized chain-like polyarsenic anions. [As21]3– represents a trimeric example of polyarsenic anion assembled through oxidative coupling of As73– anions. The anion As184– included in [As18Mo2(CO)8]4– is regarded as formed by two realgar-type As8 subunits connected by a dinuclear As-As dumbbell. The As18 cluster was previously predicted by theory, and this is the first time successfully synthesized using wet chemistry method. Besides, small-sized polyarsenides As22– and As102– were found in compound [K(18-crown-6)]3[As10]0.5[As4{Mo(CO)3}2]0.5·2en. Among these, the former exhibits coordination with metal atoms. Single-crystal X-ray diffraction combined with quantum chemical calculations revealed the formation of double bonded As22– stabilized by metal carbonyl groups. This work demonstrates a novel synthetic approach for the preparation of new polyarsenides and highlights their intriguing bonding characteristics, laying the foundation for the synthesis of such compounds and paving the way for their potential applications.
Na+ batteries (SIBs) have been emerging as the most promising candidate for the next generation of secondary batteries. However, the development of high-performance and cost-effective anode materials is urgently needed for the large-scale applications of SIBs. In this study, carbon dots confined bimetallic sulfide (NiCo2S4) architecture (NiCo2S4@CDs) was proposed and synthesized from assembling nanosheets into cross-stacked superstructure and the subsequent confinement of carbon dots. This novel decussated structure assembly from nanosheets is greatly beneficial to the structure stability of electrode material during the successive charge/discharge processes. Besides, the CDs based carbon conductive network can enhance the electrical conductivity for facilitating the easy transport of electron/Na+. Benefitting from these advantages, NiCo2S4@CDs exhibits high-rate performance and an ultralong cycling life in SIBs. Specifically, the specific capacity of NiCo2S4@CDs can reach the discharge specific capacity as high as 568.9 mAh/g at 0.5 A/g, which can also maintain 302.7 mAh/g after 750 cycles at 5.0 A/g. Additionally, ex-situ characterization techniques such as ex-situ XRD and ex-situ XPS were employed to further explore the sodium storage mechanism of the NiCo2S4@CDs anode.
Three-dimentional (3D) transition metal selenides with sufficient channels could produce significant superiority on enhancing reaction kinetics for sodium-ion batteries. However, the thorough exploration of 3D architecture with a facile strategy is still challenging. Here we report that a polycrystalline Cu2-xSe film was epitaxial grown on (220) facets-exposed Cu by direct selenization of a nanoporous Cu skeleton, which is obtained by dealloying rolled CuMn@Cu alloy foil. Density functional theory calculation result shows strong adsorption energy for Se atoms on Cu (220) planes during selenization reaction, rendering a low energy consumption. By virtue of this core-shell 3D nanoporous architecture to offer abundant active sites and endow fast electron/ion transportation, the nanoporous Cu2-xSe@Cu-0.15 composite electrode exhibits remarkable sodium-ion storage properties with high reversible capacity of 950.6 µAh/cm2 at 50 µA/cm2, suprior rate capability of 457.6 µAh/cm2 at 500 µA/cm2, as well as an ultra-long stability at a high current density. Mechanism investigation reveals that the electrochemical reaction is a typical conversion-type reaction with different intermediates. This novel electrode synthetic strategy provides useful instructions to design the high-performance anode material for sodium-ion batteries.
The preparation of Pd-based catalysts with rich electrons and a high atom dispersion rate is of great significance for improving the reactivity of cross-coupling reactions, which is a powerful tool for pharmaceutical and fine chemical synthesis. Here, we report a PdNi single-atom alloy (SAA) catalyst in which isolated Pd single atoms are anchored onto the surface of Ni nanoparticles (NPs) applied for Suzuki coupling reactions and Heck coupling reactions. The 0.1% PdNi SAA exhibits extraordinary catalytic activity (reaction rate: 17,032.25 mmol h−1 gPd−1) toward the Suzuki cross-coupling reaction between 4-bromoanisole and phenylboronic acid at 80℃ for 1 h. The excellent activity is supposed to attribute to the 100 percent utilization rate of Pd atoms and the highly stable surface zero-valance Pd atoms, which provides abundant sites and electrons for the adsorption and fracture of the C-X (X = Cl, Br, I) bond. Moreover, our work demonstrates the excellent application prospect of SAAs for cross-coupling reactions.
Recently electrochemical synthesis of H2O2 through oxygen reduction reaction (ORR) via 2e− pathway is considered as a green and on-site route. However, it still remains a big challenge for fabricating novel metal-free catalysts under acidic solutions, since it suffers from high overpotential due to the intrinsically week *OOH adsorption. Herein, a co-doped carbon nanosheet (O/NC) catalyst toward regulating O and N content was synthesized for improving the selectivity and activity of H2O2 electrosynthesis process. The O/NC exhibits outstanding 2e− ORR performance with low onset potential of 0.4 V (vs. RHE) and a selectivity of 92.4% in 0.1 mol/L HClO4 solutions. The in situ electrochemical impedance spectroscopy (EIS) tests reveals that the N incorporation contributes to the fast ORR kinetics. The density functional theory (DFT) calculations demonstrate that the binding strength of *OOH was optimized by the co-doping of oxygen and nitrogen at certain content, and the O/NCCOOH site exhibits a lower theoretical overpotential for H2O2 formation than OCCOOH site. Furthermore, the promoted kinetics for typical organic dye degradation in simultaneous electron-Fenton process on O/NC catalyst was demonstrated particularly for broadening its environmental application.
Rationally designed novel cost-effective hydrogen evolution reaction (HER) electrocatalysts with controlled surface composition and advanced structural superiority is extremely critical to optimize the HER performance. Polyoxometalates (POMs) with structural diversity and adjustable element compositions represent a promising precursor for rational design and preparation of HER electrocatalysts. Herein, a series of transition metal-doped MoS2 materials with different surface engineered structures (Fe, Cr, V doping and S vacancies) (M-MoS2/CC, M = Fe, Cr and V) were fabricated by a simple hydrothermal-vulcanization strategy using Keplerate polyoxomolybdate nanoball ({Mo72Fe30}, {Mo72Cr30}, {Mo72V30}, {Mo132}) as precursors. The enlarged interlayer spacing as well as the integration of homogeneous transition metal doping and abundant sulfur vacancies endows prepared M-MoS2/CC with superior HER electrocatalytic performance and excellent long-term working stability in both acidic and alkaline media. The optimized Fe-MoS2/CC afford current densities of 10 and 50 mA/cm2 at overpotentials of 188/272 mV and 194/394 mV in 0.5 mol/L H2SO4 and 1.0 mol/L KOH aqueous solution, respectively, outperforming most of reported typical transition metal sulfide-based catalysts. This work represents an important breakthrough for POMs-mediated highly efficient transition metal sulfide-based HER electrocatalysts with wide range pH activity and may provide new options for the rational design of promising HER electrocatalysts and beyond.
The severe interfacial charge recombination as well as the stability issues brought by the Li-TFSI still hinder the commercialization of high-performance perovskite solar cells (PSCs). Here, a polyoxometalates (POMs)-based complex, POM@ ionic liquid (IL), is synthesized and applied as an effective additive that simultaneously enhances the performance and stability of PSCs. The interactions between POM@IL complex and Li-TFSI inhibit the aggregation of Li-TFSI. The synergistic oxidation of POM@IL complex and Li-TFSI towards 2, 2′, 7, 7′-tetrakis[N, N-di(4-methoxyphenyl)amino]-9, 9'-spirobifluorene (Spiro-OMeTAD) effectively enhances the electrical properties of hole transport layer film and the photovoltaic performances of PSCs. The champion device modified with the POM@IL complex yields an excellent power conversion efficiency (PCE) of 22.73%. Moreover, the incorporation of POM@IL improves the humidity stability of PSCs. After storing under high humidity conditions (25 ℃, 60% RH) for 1200 h, the POM@IL modified device retained a remarkable 81.2% of its initial PCE. This work provides new insight into constructing POMs-based materials for high-performance photovoltaic devices.
Four new cyclohexapeptides, pyridapeptides F–I (1–4), were isolated from the fermentation broth of marine sponge-derived Streptomyces sp. OUCMDZ-4539. The pyridapeptides F–H (1–3) are composed of β-hydroxyleucine, alanine, O-methylthreonine, hexahydropyridazine-3-carboxylic acid, 5-hydroxytetrahydropyridazine-3-carboxylic acid, and (2S,3R,4E,6E)-2-amino-3–hydroxy-4,6-dienoic acid residues. Pyridapeptide Ⅰ (4) contains (2S,3R,4E,6E)-2-amino-3–hydroxy-8-methylnona-4,6-dienoic acid residue and a very rare glycose residue, aculose. Their structures were determined based on spectroscopic analysis and chemical methods. Pyridapeptides G–I (2–4) have the 2,3,6-trideoxyhexose units glycosylated at the γ-OH-TPDA residue, displayed significant antiproliferative activity against four (PC9, MKN45, HepG2, K562) or two (PC9, MKN45) human cancer cell lines.
The rapid development of high-power and pulsed-power techniques inspires extensive investigates on high-performance ceramic-based capacitors. However, the low recoverable energy density (Wrec) hampers their wider applications. Herein, the non-stoichiometric Bi0.5Na0.5TiO3-based ceramics were designed and studied. The proper introduction of oxygen vacancies facilitated activating defect dipole, giving rise to reduced remanent polarization. Consequently, the optimal composition exhibited an exceptional high Wrec of 8.3 J/cm3, a high efficiency of 85%, and excellent anti-fatigue and thermal reliability. This work provides an efficient approach to explore ceramic capacitors with high capacitive energy storage performances.
Zero thermal expansion materials are important for the practical applications due to their shape stability as changing temperature. The reported concept of average atomic volume is an available method to hunt new zero thermal expansion materials. Here, according to this concept, a tetragonal tungstate Cs2W3O10 with zero expansion has been found. There is no structure phase transition as increasing temperature from 150 K to 573 K. The coefficient of thermal expansion of axes and volume are αa = 0.0074 × 10−6 K−1, αc = 1.63 × 10−6 K−1, and αV = 1.60 × 10−6 K−1, respectively, in the temperature range of 150 ~ 573 K. The temperature- and pressure-dependent Raman spectra reveal that the vibrations of WO6 octahedra libration modes with positive total anharmonicity and W-O-W bending mode with negative Grüneisen parameter are possibly the origin of zero thermal expansion in Cs2W3O10.
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