ChemPlusChem最新文献

The gradual capacity decrease of vanadium redox flow battery (VRFB) over long-term charge-discharge cycling is determined by electrolyte degradation. While it was initially believed that this degradation was solely caused by crossover, recent research suggests that oxidative imbalance induced by hydrogen evolution reaction (HER) also plays a significant role. In this work by using vanadium pentoxides with different impurities content, we prepared three grades of vanadium electrolyte. By measuring electrochemical properties on carbon felt electrode in three-electrode cell and VRFB membrane-electrode assembly we evaluate the influence of impurity content on battery polarization and rate of side reactions which is indicated by the increase of average oxidation state (AOS) during charge-discharge tests and varies from 0.061 to 0.027 day^-1 for electrolytes made from 99.1 and 99.9 wt % V₂O₅. We found that increase of AOS correlates with the increase of open-circuit voltage of VRFB in the discharged state ranging from 9.6 to 14.9 mV day^-1 for highest and lowest electrolyte purity levels, respectively. While AOS increase is significant, it does not solely determine capacity fade. It is demonstrated that the presence of vanadium crossover decreases capacity fade, i. e. levels the contribution of side reactions on capacity drop.

Diatoms are photosynthetic microalgae widely diffused around the globe and well adapted to thrive in diverse environments. Their success is closely related to the nanostructured biosilica shell (frustule) that serves as exoskeleton. Said structures have attracted great attention, thanks to their hierarchically ordered network of micro- and nanopores. Frustules display high specific surface, mechanical resistance and photonic properties, useful for the design of functional and complex materials, with applications including sensing, biomedicine, optoelectronics and energy storage and conversion. Current technology allows to alter the chemical composition of extracted frustules with a diverse array of elements, via chemical and biochemical strategies, without compromising their valuable morphology. We started our research on diatoms from the viewpoint of material scientists, envisaging the possibilities of these nanostructured silica shells as a general platform to obtain functional materials for several applications via chemical functionalization. Our first paper in the field was published in ChemPlusChem ten years ago. Ten years later, in this Perspective, we gather the most recent and relevant functional materials derived from diatom biosilica to show the growth and diversification that this field is currently experiencing, and the key role it will play in the near future.

Photochemically driven CO₂ release using metastable-state photoacids (mPAH) initiates with trans–cis photoisomerization, followed by subsequent structural changes and proton transfer to bicarbonate ions resulting from CO₂ capture. mPAHs reversibly regulate solution pH, providing a new avenue towards energy efficient on-demand CO₂ release and solvent regeneration under ambient conditions using abundant solar energy instead of heat. More details can be found in the Concept by Uvinduni I. Premadasa, Ying-Zhong Ma, and co-workers (DOI: 10.1002/cplu.202300713).

The cover feature image illustrates a phosphine-metal complex on a variety of porous polymers and its application in continuous-flow organic synthesis as an immobilized catalyst. The sophisticated designs of ligands, pores, and reactors are summarized in terms of their excellent catalytic performances. More details can be found in the Review by Masaya Sawamura, Yoshiko Miura, and co-workers (DOI: 10.1002/cplu.202400039).

Lithium-sulfur (Li-S) batteries display promise as redox-based batteries, where separators are an essential part of preventing short-circuiting of the positive and negative electrodes, while the shuttle effect is a critical issue of separators. Currently, commercial PP separators are weak in inhibiting the polysulfides shuttling, so modified separators are needed to inhibit it to improve the battery performance. This paper reports that CeVO₄/KB composites act as separator materials. CeVO₄/KB modified PP separators enhanced the adsorption of LiPSs, accelerated the rate of Li⁺ migration, and catalyzed the conversion of LiPSs. These bring about the effect that CeVO₄/KB/PP batteries reach 1200.9 mAh g^-1 in the first cycle with a capacity retention rate of 86.5 % after 100 cycles at 0.2 C and reach 882.7 mAh g^-1 of the initial cycle with a capacity decay rate of 0.063 % after 1000 cycles at 3 C. This work introduces rare earth metal vanadates to modify the separator, adding new ideas for designing separators for good-performance batteries.

Macrocycles' unique properties of interacting with guest molecules have been an intriguing scientific endeavor for many decades. They are potentially practically useful for engineering applications, especially in energy and environmental applications. These applications are usually demanding, involving a high temperature, pH, voltage, etc., thus, finding suitable substrates that can endure working environments and sustain macrocycles' properties is highly desirable. In that sense, covalent networks are ideal as they are chemically/electrochemically/thermally stable and can be porous by design. Emerging porous materials, especially covalent organic frameworks (COFs), could be suitable as their porous spaces allow macrocycles to interact with guest species. In the past seven years, we have seen the rise of mechanically interlocked macrocycles on covalent networks (MIMc-CNs) that translate macrocycles' properties into macroscale materials. In this conceptual review, we first describe the idea of integrating MIMcs into COFs or conventional amorphous polymers. Next, we review the reported representative MIMc-CNs used in energy and environmental applications. We also provide a brief outlook for the future directions for the MIMc-CNs research.

In this study, ultrafine linear nanostructured SiC with high wettability and large specific surface area were synthesized via the carbothermal reduction method. These nanowires were impregnated with Na₂SO₄ ⋅ 10H₂O, CaCl₂ ⋅ 6H₂O, MgCl₂ ⋅ 6H2O, and CaMg₂Cl₆ ⋅ 12H₂O to obtain composite phase change materials (CPCMs), which demonstrated improved phase separation and significantly reduced supercooling. In particular, the supercooling degree of CaCl₂ ⋅ 6H₂O was minimized to 0.1 °C. The SiC nanowires effectively prevented issues of dehydration and deliquescence in hydrated salts. The thermal storage capacities of the CPCMs exceeded 90 %, with Na₂SO₄ ⋅ 10H₂O and MgCl₂ ⋅ 6H₂O reaching 107.10 % and 103.35 %, respectively. Furthermore, the CPCMs exhibited greater sensitivity to changes in temperature compared with the pure hydrated salt phase change materials (PCMs). These results indicate that ultra-fine SiC nanowires can act as a versatile carrier for hydrated salt PCMs at low and intermediate temperatures.

Carbonatoperoxovanadates are considered as promising functional materials in optoelectronic devices due to their excellent optical properties, particularly strong second-harmonic generation (SHG) response. However, the relationship between their geometric structures and optical properties remains unclear. Herein, the structural, electronic, and optical properties of carbonatoperoxovanadates A₃VO(O₂)₂CO₃ (A=K, Rb, and Cs) were investigated using first-principles calculation. Results suggest that high-density and parallel arrangement of nonlinear optical active [VO(O₂)₂CO₃] units are conducive to generating large SHG response in A₃[V(O₂)₂O]CO₃. Optical anisotropy was observed. Birefringence values for A₃[V(O₂)₂O]CO₃ were comparable to those of commonly used infrared nonlinear optical materials. Specifically, results of tiny optical characteristics (local dipole moments, HUMO-LUMO gap, polarizability anisotropy, and hyperpolarizability) indicate that asymmetry [VO(O₂)₂CO₃] is an excellent nonlinear optical active functional unit, owing to the synergistic effect between its non-centrosymmetric nonlinear optical elements. This study elucidates the structure-property relationship of carbonatoperoxovanadates, offering valuable insights for designing novel high-performance SHG materials.

Au single atoms and clusters were stabilized on Mg-Al layered double hydroxide nanoparticles (LDH NPs), and the obtained Au@LDH NPs were supported on SiO₂ and CeO₂. After hydrogen reduction, Au single atoms were found together with Au clusters on LDH/SiO₂. In contrast to Au single-atom catalysts which are deposited in metal vacancies of oxide supports, the LDH NPs stabilize very small Au species despite the absence of metal vacancies. The obtained Au(0)@LDH/SiO₂ catalyzed aerobic oxidation of alcohols, and Au single atoms maintained after the reaction. Given that only Au NPs were observed on bulk LDH, the abundant surface OH group of LDH NPs would contribute to stabilize Au, resulting in higher activity than Au/LDH-bulk. After calcination to transform LDH to mixed metal oxide (MMO), the obtained Au(0)@MMO/SiO₂ also exhibited high catalytic activity. Moreover, Au(0)@LDH/CeO₂ exhibited higher activity and excellent selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene than conventional Au catalysts such as Au/CeO₂ and Au/TiO₂. We demonstrated that Au size can be minimized using LDH NPs, exhibiting high catalytic performance. The basic surface OH groups of LDH would be also beneficial for deprotonation of alcohols and heterolytic dissociation of H₂ in the catalytic reactions.

Organic compounds bearing one or more carbocycles in their molecular structure have a discernible presence in all major classes of organic products of industrial significance. However, sourcing carbocyclic compounds from exhaustible, anthropogenic carbon (e. g., petroleum) raises serious concerns about sustainability in the chemical industries. This review discusses recent advances in the renewable synthesis of carbocyclic compounds from biomass components following catalytic pathways. The mechanistic insights, process optimizations, green metrics, and alternative synthetic strategies of carbocyclic compounds have been detailed. Moreover, the renewable syntheses of carbocycles have been assessed against their existing synthetic routes from petroleum for better perspectives on their sustainability and technological preparedness. This work will assist the researchers in acquiring updated information on the sustainable synthesis of carbocyclic compounds from various biomass components, comprehending the research gaps, and developing superior synthetic processes for their commercial production.