ChemSusChem最新文献

Covalent organic frameworks (COFs) are becoming increasingly attractive in photocatalytic transformations because of the designable structures grounded on the building blocks and the linkage. Herein, benzo[1,2-b:4,5-b']dithiophene, essential for various organic optoelectronic materials, is adopted as the building block for COFs. Hence, a fully conjugated COF BDTT-sp2c-COF and imine-linked COF BDTT-COF are constructed of 5',5''''-(benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis([1,1':3',1''-terphenyl]-4,4''-dicarbaldehyde) with p-phenyldiacetonitrile and p-phenylenediamine, respectively. Thorough characterizations and theoretical calculations disclose that BDTT-sp2c-COF is superior to BDTT-COF in terms of specific surface area, photocarrier separation, and electron transfer. As such, BDTT-sp2c-COF enables more efficient photocatalytic sulfoxidation with oxygen than BDTT-COF. The fully conjugated structure guarantees the recyclability of BDTT-sp2c-COF. The blue light-driven sulfoxidation is generally applicable and proceeds selectively via energy and electron transfers over BDTT-sp2c-COF. The fully conjugated COFs are promising to enable photocatalytic reactions.

Metal sulfides represent a broad class of materials with considerable potential for applications in photovoltaic devices and energy technologies. However, the low-temperature synthesis of high-quality metal sulfide thin films remains a formidable challenge. Hydrothermal deposition, known for its versatility and cost-efficiency, has been successfully employed to synthesize a variety of materials, yet its application in the preparation of metal sulfide thin films has not been extensively explored. In this study, we develop a hydrothermal deposition method to synthesize five distinct types of metal sulfide thin films, each with well-defined phases and compositions. As a case study, CdS/Bi₂S₃ thin film was selected and evaluated as photoanode for photoelectrochemical water splitting. Through O-doping and the modification of an ultrathin MoO₃ overlayer, the photocurrent density was significantly enhanced from 1.52 mA cm^-2 (CdS/Bi₂S₃) to 2.27 mA cm^-2 (CdS/O-Bi₂S₃), and further to 2.84 mA cm^-2 (CdS/O-Bi₂S₃/MoO₃) at 1.23 V vs. reversible hydrogen electrode under AM 1.5G illumination. This methodology is expected to advance both fundamental and applied research on metal sulfides.

Conventional low-concentration aqueous electrolytes (AqE) for Zn metal batteries face undesirable parasitic reactions, severely deteriorating thei.r sustainability. Although low-water-content electrolytes have shown promise in mitigating water splitting, their high viscosity and limited ion transport lead to sluggish reaction kinetics. In this work, we propose a water-content gradient electrolyte (GE) by constructing a sandwich-like structure, where two molecular crowding electrolyte (MCE) layers are applied on both electrode surfaces, while a conventional AqE occupies the space in between. The low-water-content MCE effectively suppresses electrode corrosion and dissolution, while the high-water-content AqE improves ionic conductivity. As a result, Zn/Zn symmetric cells utilizing the GE demonstrate exceptional long-term cycling for over 2000 hours at 2 mA cm^-2 to 4 mAh cm^-2 and over 300 hours at 7.5 mA cm^-2 to 15 mAh cm^-2. The Zn-vanadium and Zn-manganese full cells in GE also show remarkable longevity, with cycling lives exceeding several thousand cycles at 2 A g^-1, and excellent reaction kinetics across varying current densities. Overall, the GE successfully integrates the benefits of both AqE and MCE, leading to enhanced electrode protection without compromising ion transport, thereby offering a new avenue for developing long-lasting aqueous Zn metal batteries.

External fields in regulating catalyst structure and tailoring catalytic performance have garnered significant attention from researchers. In this study, an external magnetic field was introduced into biomass conversion and employed as an effective means to accelerate electrocatalytic oxidation. An ox-NiCoP electrocatalyst was fabricated as an electrocatalyst for the oxidation of 2,5-bis(hydroxymethyl)furan (BHMF) to 2,5-furandicarboxylic acid (FDCA). Upon application of a 0.48 T magnetic field, the conversion of BHMF and the yield of FDCA were increased by 27.8 % and 27.5 %, respectively. The reaction time was shortened by 3.8 h compared to the reaction without a magnetic field. Kinetic analysis revealed that the magnetic field significantly reduced the charge transfer resistance and accelerated the kinetics of the BHMF oxidation reaction (BHMFOR), achieving a maximum reaction rate constant (k) of 2.53 h^-1. The enhancement mechanism was attributed to the magnetic field-induced convection at the electrode surface via the Lorentz force, which improved BHMF diffusion between the catalytic interface and the electrolyte. This work highlights the promotive effect of an external magnetic field in the electrocatalytic conversion of organic molecules.

A series of MoS2/C composites are synthesized for SIB anode by changing sulfur sources using a facile hydrothermal and ball milling strategy. The carbon modification increases the conductivity and minimizes volume expansion of the material. The intercalation potential was find out for MoS2/C composites by several electrochemical and ex-situ XRD measurements. The MoS2-NS/C, MoS2-Tu/C, and MoS2-S/C electrodes deliver ~312, 304 and 293 mAh/g reversible capacities at 50 mA/g current densities between 0.3-2.5 V. The different reversible capacities of MoS2/C composites could be due to the different surface areas or morphologies of the composites. We also demonstrate the effect of succinic anhydride (SA) as electrolyte additive in cyclic stabilities, which shows an increment of (~60% to ~76%) capacity retention with SA addition. The ex-situ XPS and TEM analysis revealed that more Na2CO3 rich SEI was formed in presence of SA. The SA-derived SEI also prevents the NaPF6 degradation, thereby increases the cyclic performance. Furthermore, the full cells assembled with MoS2/C (anode) and Na3V2(PO4)3 (cathode) shows ~280 mAh/g specific capacity at 0.05 A/g based on active mass of anode. The improved Na+ storage performance is attributed to the fast Na+ intercalation, improved conductivity and stable SEI formation during charge/discharge.

Li_1+xFe_1-xPO₄ (Li-rich LFP) has been proposed as an alternative to address low ionic and electronic conductivity of stoichiometric LiFePO₄ (LFP). However, comprehensive studies investigating the impact of the carbon coating process on crystal structure and electrochemical performance during the synthesis of Li-rich LFP are still lacking. In particular, the characteristics of carbon precursor and calcination atmosphere significantly influence formation of crystal structure and electrochemical properties of the Li-rich LFP, underlining the necessity for further investigation. In this study, we compare two synthesis process: introducing carbon precursor before formation of LFP crystal structure (C/BLF) and adding it an additional calcination step after structure has formed (C/ALF). The C/ALF process sample has a larger unit cell volume and denser coating layer. As a result, the C/ALF sample exhibits a lower overpotential (0.54 V) and a higher discharge capacity (~134.13 mAhg^-1) than C/BLF sample. These findings elucidate the influence of carbon coating process sequence on crystal structure and electrochemical performance during the synthesis of Li-rich LFP.

Phase Change Materials (PCMs) with melting temperatures in the intermediate range (100-220 °C) have recently been in high demand for applications in solar and wind renewable energy storage. Such materials can help advance thermal battery technologies, such as Carnot batteries, that can reduce the amount of fossil fuels used to generate electricity, contributing to substantial savings in CO2 emissions. Recently, polyol esters have been recognized as robust PCMs with high stability and high energy storage density (up to 221 J g-1), additionally meeting sustainability and circularity criteria, being sources from inexpensive, biorenewable tartaric acid (TA), which provides H-bonding, boosting the esters' thermal properties. However, the melting points of TA esters, which are below 100 °C, limit their suitability for applications in the intermediate temperature range. In this study, we explored TA diamides as candidates for thermal energy storage with improved melting temperatures ranging from 156 to 201 °C and melting enthalpies up to 173 J g-1. With the aid of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and temperature-dependent Fourier-transform infrared spectroscopy (FT-IR), we investigated various perspectives and limitations of designing TA-derived PCMs for sustainable heat use above 100 °C.

Polyurethane (PU) is the 6th most produced plastic on a global basis, and thus one of the most important targets in the field of recycling of plastic waste. The glycolysis of PU is currently considered the most promising pathway toward industrial implementation. However, the energy consumption during the process, the cost of the excess glycol relative to PU, and the potentially reduced quality of polyol products resulting from glycol residues may still limit the speed of implementation of PU chemical recycling processes from lab to the pilot plant scale. Therefore, an alternative route for PU depolymerization is explored using mechanochemistry and catalysis. In this work, recovery of up to 86% of soluble polyol by mechanocatalytic methanolysis/hydrolysis of NaOH-impregnated commercial PU product (household sponge), with a Cu/MgAlO_x co-catalyst below 100 °C, is described. The recycled polyol can serve as new raw material and has been successfully used as feedstock for the resynthesis of PU. The low reaction temperature, reduced volume of solvent, and easy separation of products could make this novel chemical recycling methodology an attractive alternative to the conventional solvolysis pathways.

The photoreduction of CO2 to methanol and ethanol is a highly sought-after reaction due to the economic and environmental implications of these products. Both methanol and ethanol are versatile chemical feedstock and renewable fuels. The ionic hybrid compound [Zr6O4(OH)4(C6H5COO)8(H2O)8][SiW12O40] (Zr6W12) provides effective separation of the generated electron-hole pair during exposure to UV radiation through a Z-scheme disposition of the HOMO-LUMO levels of each discrete ionic entity. However, this compound does not promote the CO2 reduction. In contrast, the incorporation of selected inorganic cocatalysts, such as AgI, Bi2O3, CeO2, CuI, CuO, Cu2O, In2O3, PbO, Sb2O3, SnO, TiO2 or ZnO, to the photocatalytic system can enable the activation and reduction of CO2, leveraging their electronic properties and interactions with Zr6W12. Some of these heterogeneous photocatalytic systems perform well for the photoreduction of CO2 into methanol and/or ethanol in water and without the need of any sacrificial chemical reagent, achieving maximum production levels of 163 µg·g-1·h-1 and 144 µg·g-1·h-1 for methanol and ethanol, respectively, for the Zr6W12/CuI photocatalytic mixture. Theoretical calculations have been conducted to determine how the relative disposition of the HOMO/LUMO energy levels of Zr6W12 and the band structure of the inorganic cocatalysts impact on the CO2 photocatalytic reduction to alcohols.

The combustion of fossil fuels has led to a growing level of CO₂ in atmosphere. The study about relief CO₂ emission has received wide attention. Many researchers focus on converting CO₂ into liquid fuels by thermochemical hydrogenation route, since its broad application prospects. In this review, we systematically discussed four dominating catalytic systems for CO₂ to liquid fuels, including Fe-based, Fe-based/Zeolite, Co-based and Oxide/Zeolite catalysts. The catalytic performances and reaction conditions of different catalysts are compared. The reaction pathways and the roles of various active sites in different catalytic systems are discussed. At the same time, we propose possible research directions based on the current problems in these catalytic systems. We hope that this review could provide inspiration for the development of efficient catalysts, the exploration of reaction pathways and the construction of novel catalytic systems.