Promising and Reversible Electrolyte with Thermal Switching Behavior for Safer Electrochemical Storage Devices

A major stumbling block in large-scale adoption of high-energy-density electrochemical devices has been safety issues. Methods to control thermal runaway are limited by providing a one-time thermal protection. Herein, we developed a simple and reversible thermoresponsive electrolyte system that is efficient to shutdown the current flow according to temperature changes. The thermal management is ascribed to the thermally activated sol–gel transition of methyl cellulose solution, associated with the concentration of ions that can move between isolated chains freely or be restricted by entangled molecular chains. We studied the effect of cellulose concentration, substituent types, and operating temperature on the electrochemical performance, demonstrating an obvious capacity loss up to 90% approximately of its initial value. Moreover, this is a cost-effective approach that has the potential for use in practical electrochemical storage devices

Nickel-Catalyzed Direct C (sp³)–H Arylation of Aliphatic Amides with Thiophenes

Nickel-catalyzed heteroarylation of the inactive methyl C­(sp³)–H bond of aliphatic amide with heteroarenes is described. The method takes advantage of chelation assistance by an 8-aminoquinolinyl moiety. The synthetic reaction has good tolerance toward functional groups, and it can be used in the construction of various kinds of alkyl-substituted heteroarenes

Nickel-Catalyzed Regioselective Cleavage of C_sp²–S Bonds: Method for the Synthesis of Tri- and Tetrasubstituted Alkenes

We describe here an efficient route for the synthesis of (<i>Z</i>)-vinylic sulfides <b>3</b> via the highly regio- and stereoselective coupling of (<i>Z</i>)-1,2-bis­(aryl­(alkyl)­thio)­alkenes and Grignard reagents over a Ni catalyst under mild conditions. (<i>Z</i>)-Vinylic sulfides <b>3</b> are important intermediates in the synthesis of tri- and tetrasubstituted alkenes that are important construction blocks for drugs and natural products. The directing organosulfur groups (SR) can be converted to diaryl­(alkyl) disulfides (RSSR) using H₂O₂ as oxidant, hence avoiding the waste of sulfur resources. The protocol provides a general method that is highly regio- and stereoselective for the synthesis of a diversity of tri- and tetrasubstituted alkenes

Sulfite as a Green Co-milling Agent for Mechanochemical Destruction of Polychlorinated Aromatics: Working Mechanism and Structural Dependence

Mechanochemical destruction of obsolete halogenated persistent organic chemicals (especially polychlorinated aromatics) has been documented as a safe non-combustion technology, but the smooth implementation of such a system still calls for an appropriate and sustainable co-milling agent. As an example, we show that Na2SO3 as a co-milling agent not only achieves faster degradation rate for hexachlorobenzene (HCB) than calcium oxide (1.4-fold) and reduced iron powders (2.9-fold) with equal mass but also enables high dechlorination ratio (97.4%) after 4 h of milling in a planetary mill. With the input of mechanical energy, the mechanistic study suggests that sulfite salts suffer partial melt to generate SO32– species on fresh surfaces, which attack HCB molecules via the one-electron-transfer mechanism. Detection on intermediates and characterization on milled samples demonstrate that HCB undergoes dechlorination, polymerization, and hydrogenation and finally converts to amorphous and graphitic carbons. Correlation analysis indicates that the degradation reactivity of a specific polychlorinated aromatic compound in such a system is strongly dependent on its molecular structure (e.g., substituent groups and degree of chlorination). This work provides a new insight for utilizing sulfite for green disposal of halogenated wastes

Removal of Antibiotic Florfenicol by Sulfide-Modified Nanoscale Zero-Valent Iron

Florfenicol (FF, C₁₂H₁₄Cl₂FNO₄S), an emerging halogenated organic contaminant of concern was effectively degraded in water by sulfidized nanoscale zerovalent iron (S-nZVI). Sulfidized nZVI (62.5 m² g^–1) that was prepared using a one-step method resulted in small Fe⁰/Fe-sulfide particles that were more stable against aggregation than unsulfidized nZVI (10.2 m² g^–1). No obvious removal of FF was observed by unsulfidized nZVI. S-nZVI degraded FF, having a surface area normalized reaction rate constant of 3.1 × 10^–4 L m^–2 min^–1. The effects of the S/Fe molar ratio, initial FF concentration, initial pH, temperature, and water composition on the removal of FF by S-nZVI, and on the formation of reaction products, were systematically investigated. Both dechlorination and defluorination were observed, resulting in four degradation products (C₁₂H₁₅ClFNO₄S, C₁₂H₁₆FNO₄S, C₁₂H₁₇NO₄S, and C₁₂H₁₇NO₅S). High removal efficiencies of FF by S-nZVI were achieved in groundwater, river water, seawater, and wastewater. The reactivity of S-nZVI was relatively unaffected by the presence of both dissolved ions and organic matter in the waters tested

Three-Dimensional Conductive Gel Network as an Effective Binder for High-Performance Si Electrodes in Lithium-Ion Batteries

Silicon (Si) has been widely investigated as a candidate for lithium-ion batteries (LIBs) due to its extremely high specific capacity. The binders play a key role in fabricating high-performance Si electrodes which usually suffer from the huge volume expansion associated with the alloying and dealloying processes. Here we develop a facile route to prepare a three-dimensional (3D) conductive interpenetrated gel network as a novel binder for high-performance Si anodes through chemically cross-linking of acrylic acid monomer followed by the in situ polymerization of aniline. The excellent electrical conductivity, strong mechanical adhesion and high electrolyte uptake render the conductive gel network a potential binder for high-performance Si anodes. The resultant Si anodes exhibit excellent cycling stability, high Coulombic efficiency and superior rate capability, revealing better electrochemical properties compared to the Si anodes with conventional binders. The 3D conductive gel binder could not only accommodate the volume expansion and maintain electric connectivity, but also assist in the formation of stable solid electrolyte interphase (SEI) films. Such a strategy sheds light on the design of polymer binders in LIBs, especially for high-capacity electrode materials with huge volume changes during long-term cycling

Nickel-Catalyzed Direct Thiolation of C(sp³)–H Bonds in Aliphatic Amides

Nickel-catalyzed thiolation of the inactivated methyl C­(sp³)–H bonds of aliphatic amides with disulfide is described. It is a novel strategy for the synthesis of thioethers with the ultimate goal of generating thioether carboxylic acids with various functional groups

Copper-Mediated Remote C–H Bond Chalcogenation of Quinolines on the C5 Position

An efficient and convenient method is developed for the remote C–H bond chalcogenation of 8-aminoquinoline scaffolds on the C5 position that is geometrically inaccessible. The protocol makes use of inexpensive CuBr₂ as mediator and shows good tolerance toward numerous disulfides/diselenides and aliphatic amides, giving the corresponding products in good to excellent yield

Synthesis, Characterization, and Photocatalytic Properties of SnO₂/Rutile TiO₂/Anatase TiO₂ Heterojunctions Modified by Pt

To improve the separation rate of photogenerated electrons and holes, a SnO₂/rutile TiO₂ (R-TiO₂)/anatase TiO₂ (A-TiO₂) photocatalyst modified by Pt nanoparticles with three pairs of heterojunctions was fabricated by a facile hydrothermal method. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) clearly illustrated the structure of the three pairs of heterojunctions connected to each other. Heteronanostructure photocatalysts with increased specific surface area could offer more active sites when contacting pollutants, resulting in improved photocatalytic activity. The red shift in UV–vis diffuse reflectance spectra (DRS) indicated the utilization of visible-light. Photoluminescence (PL) and photoelectrochemical (PEC) measurements suggested the enhancement of electron and hole separation, in accordance with the results obtained for the photocatalytic oxidation of decomposing toluene over 4 h. A catalyst containing 1 wt % Pt/10 at. % SnO₂/R-TiO₂/A-TiO₂ exhibited the best photocatalytic mineralization rates of toluene: 40.9% and 72.3% under visible-light and UV-light irradiation, respectively. A proposed mechanism was elaborated to reveal the effective photocatalytic progress of charge transfer along multiple pathways along the three pairs of heterojunctions doped with Pt

Identification of Active Hydrogen Species on Palladium Nanoparticles for an Enhanced Electrocatalytic Hydrodechlorination of 2,4-Dichlorophenol in Water

Clarifying hydrogen evolution and identifying the active hydrogen species are crucial to the understanding of the electrocatalytic hydrodechlorination (EHDC) mechanism. Here, monodisperse palladium nanoparticles (Pd NPs) are used as a model catalyst to demonstrate the potential-dependent evolutions of three hydrogen species, including adsorbed atomic hydrogen (H*_ads), absorbed atomic hydrogen (H*_abs), and molecular hydrogen (H₂) on Pd NPs, and then their effect on EHDC of 2,4-dichlorophenol (2,4-DCP). Our results show that H*_ads, H*_abs, and H₂ all emerge at −0.65 V (vs Ag/AgCl) and have increased amounts at more negative potentials, except for H*_ads that exhibits a reversed trend with the potential varying from −0.85 to −0.95 V. Overall, the concentrations of these three species evolve in an order of H*_abs < H*_ads < H₂ in the potential range of −0.65 to −0.85 V, H*_ads < H*_abs < H₂ in −0.85 to −1.00 V, and H*_ads < H₂ < H*_abs in −1.00 to −1.10 V. By correlating the evolution of each hydrogen species with 2,4-DCP EHDC kinetics and efficiency, we find that H*_ads is the active species, H*_abs is inert, while H₂ bubbles are detrimental to the EHDC reaction. Accordingly, for an efficient EHDC reaction, a moderate potential is desired to yield sufficient H*_ads and limit H₂ negative effect. Our work presents a systematic investigation on the reaction mechanism of EHDC on Pd catalysts, which should advance the application of EHDC technology in practical environmental remediation