Unraveling the Mechanism of Covalent Organic Frameworks-Based Functional Separators in High-Energy Batteries.

Covalent organic frameworks (COFs) are promising porous materials due to their high specific surface area, adjustable structure, highly ordered nanochannels, and abundant functional groups, which brings about wide applications in the field of gas adsorption, hydrogen storage, optics, and so forth. In recent years, COFs have attracted considerable attention in electrochemical energy storage and conversion. Specifically, COF-based functional separators are ideal candidates for addressing the ionic transport-related issues in high-energy batteries, such as dendritic formation and shuttle effect. Therefore, it is necessary to make a comprehensive understanding of the mechanism of COFs in functional separators. In this review, the advantages, applications as well as synthesis of COFs are firstly presented. Then, the mechanism of COFs in functional separators for high-energy batteries is summarized in detail, including pore channels regulating ionic transport, functional groups regulating ionic transport, adsorption effect, and catalytic effect. Finally, the application prospect of COFs-based separators in high-energy batteries is proposed. This review may provide new insights into the design of functional separators for advanced electrochemical energy storage and conversion systems.

Furnishing Continuous Efficient Bidirectional Polysulfide Conversion for Long-Life and High-Loading Lithium-Sulfur Batteries via the Built-In Electric Field.

Most catalysts cannot accelerate uninterrupted conversion of polysulfides, resulting in poor long-cycle and high-loading performance of lithium-sulfur (Li-S) batteries. Herein, rich p-n junction CoS2 /ZnS heterostructures embedded on N-doped carbon nanosheets are fabricated by ion-etching and vulcanization as a continuous and efficient bidirectional catalyst. The p-n junction built-in electric field in the CoS2 /ZnS heterostructure not only accelerates the transformation of lithium polysulfides (LiPSs), but also promotes the diffusion and decomposition for Li2 S the from CoS2 to ZnS avoiding the aggregation of lithium sulfide (Li2 S). Meanwhile, the heterostructure possesses a strong chemisorption ability to anchor LiPSs and superior affinity to induce homogeneous Li deposition. The assembled cell with a CoS2 /ZnS@PP separator delivers a cycling stability with a capacity decay of 0.058% per cycle at 1.0 C after 1000 cycles, and a decent areal capacity of 8.97 mA h cm-2 at an ultrahigh sulfur mass loading of 6 mg cm-2 . This work reveals that the catalyst continuously and efficiently converts polysulfides via abundant built-in electric fields to promote Li-S chemistry.

Comparison of nutritional value, bioactivity, and volatile compounds of soybean meal-corn bran mixed substrates fermented by different microorganisms.

To evaluate the impact of fermentation with different microorganisms on the nutritional quality and bioactivity of soybean meal-corn bran mixed substrates (MS), five lactic acid bacteria (LAB) strains, two Bacillus, and two yeast strains with excellent probiotics were selected for solid-state fermentation of soybean meal and corn bran MS. The fermented mixed substrate (FMS) inoculated with Lacticaseibacillus casei, Lactobacillus fermentum, Lactiplantibacillus plantarum, and Lactobacillus acidophilus presents lower risk of infection with pathogenic bacteria, probably due to their low pH and high lactate content. Compared to the FMS with LAB and yeast, Bacillus subtilis and B. pumilus showed significant improvements in nutritional quality and bioactivity, including TCA-SP, small peptide, free amino acids, total phenol, and protein digestibility. More than 300 volatile compounds were identified in FMS, including alcohols, ketones, aldehydes, esters, acids, ethers, furans, pyrazines, benzene, phenols, amines, alkanes, and others. FMS with Bacillus was characterized as containing a greater number of compounds such as ketones, aldehydes, and pyrazines. This study showed that microbial fermented feeds differed with various microorganism, and fermentation was an effective way to improve the quality of soybean meal-corn bran mixed feeds. This study might be the basis for excellent strains screening for multi-microbial combined fermentation in the future.

Dynamics of bacterial community, metabolites profile and physicochemical characteristics during solid-state fermentation of soybean meal and corn mixed substrates inoculated with Bacillus pumilus and Limosilactobacillus fermentum.

BACKGROUND: Solid-state fermentation (SSF) is a general approach for preparing food and feed, which not only improves nutrition but also provides prebiotics and metabolites. Although many studies have been conducted on the effects of fermentation on feed substrate, the dynamics of microbiota and metabolites in SSF remain unclear. Here, high-throughput sequencing combined with gas chromatography-quadrupole time-of-flight mass spectrometry was used to evaluate the dynamic changes of solid fermented soybean meal and corn mixed matrix inoculated with Bacillus pumilus and Limosilactobacillus fermentum. RESULTS: Generally, inoculated bacteria rapidly proliferated, accompanied by the degradation of macromolecular proteins and an increase in the content of small peptides, trichloroacetic acid-soluble protein, free amino acids and organic acids. Bacillus, Lactobacillus and Enterococcus dominated the whole fermentation process. 389 non-volatile metabolites and 182 volatile metabolites were identified, including amino acids, organic acids, ketones, aldehydes, furans and pyrazine. Typical non-volatile metabolites such as lactic acid, 4-aminobutanoic acid, l-glutamic acid, d-arabinose and volatile metabolites such as 4-ethyl-2-methoxyphenol, 4-penten-2-ol, 2-pentanone, 2-ethylfuran, 2-methylhexanoic acid and butanoic acid-ethyl ester were significantly increased in two-stage solid fermentation. However, some adverse metabolites were also produced, such as oxalic acid, acetic acid, tyramine and n-butylamine, which may affect the quality of fermented feed. Sixteen genera were significantly correlated with differential non-volatile metabolites, while 11 genera were significantly correlated with differential volatile metabolites. CONCLUSION: These results characterized the dynamic changes in the process of two-stage solid-state fermentation with Bacillus pumilus and Limosilactobacillus fermentum and provided a potential reference for additional intervention on improving the effectiveness and efficiency of solid-state fermentation of feed in the future. © 2023 Society of Chemical Industry.

Synthetic method, growth mechanism and electrochemical properties of PbSnS2 nanosheets for supercapacitors.

Facile hydrothermally synthesized PbSnS2 nanosheets with various morphologies were developed to obtain high performance electrode materials for supercapacitors. A precipitation-dissolution mechanism was proposed to demonstrate the growth process of PbSnS2. The as-prepared nanosheets exhibited superior capacitance (678.8 F g-1 at 50 mV s-1) and a long cycle life (95.5% capacitance retention after 100 000 cycles at 5 A g-1).

Influence of Long-Term Storage on Shape Memory Performance and Mechanical Behavior of Pre-stretched Commercial Poly(methyl methacrylate) (PMMA).

In this paper, we experimentally investigate the influence of storage at 40 °C on the shape memory performance and mechanical behavior of a pre-stretched commercial poly(methyl methacrylate) (PMMA). This is to simulate the scenario in many applications. Although this is a very important topic in engineering practice, it has rarely been touched upon so far. The shape memory performance is characterized in terms of the shape fixity ratio (after up to one year of storage) and shape recovery ratio (upon heating to previous programming temperature). Programming in the mode of uniaxial tension is carried out at a temperature within the glass transition range to one of four prescribed programming strains (namely 10%, 20%, 40% and 80%). Also investigated is the residual strain after heating for shape recovery. The characterization of the mechanical behavior of programmed samples after storage for up to three months is via cyclic uniaxial tensile test. It is concluded that from an engineering application point view, for this particular PMMA, programming should be done at higher temperatures (i.e., above its Tg of 110 °C) in order to not only achieve reliable and better shape memory performance, but also minimize the influence of storage on the shape memory performance and mechanical behavior of the programmed material. This finding provides a useful guide for engineering applications of shape memory polymers, in particular based on the multiple-shape memory effect, temperature memory effect, and/or low temperature programming.

Binocular contrast-gain control for natural scenes: Image structure and phase alignment.

In the context of natural scenes, we applied the pattern-masking paradigm to investigate how image structure and phase alignment affect contrast-gain control in binocular vision. We measured the discrimination thresholds of bandpass-filtered natural-scene images (targets) under various types of pedestals. Our first experiment had four pedestal types: bandpass-filtered pedestals, unfiltered pedestals, notch-filtered pedestals (which enabled removal of the spatial frequency), and misaligned pedestals (which involved rotation of unfiltered pedestals). Our second experiment featured six types of pedestals: bandpass-filtered, unfiltered, and notch-filtered pedestals, and the corresponding phase-scrambled pedestals. The thresholds were compared for monocular, binocular, and dichoptic viewing configurations. The bandpass-filtered pedestal and unfiltered pedestals showed classic dipper shapes; the dipper shapes of the notch-filtered, misaligned, and phase-scrambled pedestals were weak. We adopted a two-stage binocular contrast-gain control model to describe our results. We deduced that the phase-alignment information influenced the contrast-gain control mechanism before the binocular summation stage and that the phase-alignment information and structural misalignment information caused relatively strong divisive inhibition in the monocular and interocular suppression stages. When the pedestals were phase-scrambled, the elimination of the interocular suppression processing was the most convincing explanation of the results. Thus, our results indicated that both phase-alignment information and similar image structures cause strong interocular suppression.

Direct Growth of CuO Nanorods on Graphitic Carbon Nitride with Synergistic Effect on Thermal Decomposition of Ammonium Perchlorate.

Novel graphitic carbon nitride/CuO (g-C3N4/CuO) nanocomposite was synthesized through a facile precipitation method. Due to the strong ion-dipole interaction between copper ions and nitrogen atoms of g-C3N4, CuO nanorods (length 200-300 nm, diameter 5-10 nm) were directly grown on g-C3N4, forming a g-C3N4/CuO nanocomposite, which was confirmed via X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Finally, thermal decomposition of ammonium perchlorate (AP) in the absence and presence of the prepared g-C3N4/CuO nanocomposite was examined by differential thermal analysis (DTA), and thermal gravimetric analysis (TGA). The g-C3N4/CuO nanocomposite showed promising catalytic effects for the thermal decomposition of AP. Upon addition of 2 wt % nanocomposite with the best catalytic performance (g-C3N4/20 wt % CuO), the decomposition temperature of AP was decreased by up to 105.5 °C and only one decomposition step was found instead of the two steps commonly reported in other examples, demonstrating the synergistic catalytic activity of the as-synthesized nanocomposite. This study demonstrated a successful example regarding the direct growth of metal oxide on g-C3N4 by ion-dipole interaction between metallic ions, and the lone pair electrons on nitrogen atoms, which could provide a novel strategy for the preparation of g-C3N4-based nanocomposite.

Scalable Synthesis of Ag Networks with Optimized Sub-monolayer Au-Pd Nanoparticle Covering for Highly Enhanced SERS Detection and Catalysis.

Highly porous tri-metallic AgxAuyPdz networks with a sub-monolayer bimetallic Au-Pd nanoparticle coating were synthesized via a designed galvanic replacement reaction of Ag nanosponges suspended in mixed solutions of HAuCl4 and K2PdCl4. The resulting networks' ligaments have a rough surface with bimetallic nanoparticles and nanopores due to removal of Ag. The surface morphology and composition are adjustable by the temperature and mixed solutions' concentration. Very low combined Au and Pd atomic percentage (1-x) where x is atomic percentage of Ag leads to sub-monolayer nanoparticle coverings allowing a large number of active boundaries, nanopores, and metal-metal interfaces to be accessible. Optimization of the Au/Pd atomic ratio y/z obtains large surface-enhanced Raman scattering detection sensitivity (at y/z = 5.06) and a higher catalytic activity (at y/z = 3.55) toward reduction reactions as benchmarked with 4-nitrophenol than for most bimetallic catalysts. Subsequent optimization of x (at fixed y/z) further increases the catalytic activity to obtain a superior tri-metallic catalyst, which is mainly attributed to the synergy of several aspects including the large porosity, increased surface roughness, accessible interfaces, and hydrogen absorption capacity of nanosized Pd. This work provides a new concept for scalable synthesis and performance optimization of tri-metallic nanostructures.

Hierarchically porous MnO2 microspheres doped with homogeneously distributed Fe3O4 nanoparticles for supercapacitors.

Hierarchically porous yet densely packed MnO2 microspheres doped with Fe3O4 nanoparticles are synthesized via a one-step and low-cost ultrasound assisted method. The scalable synthesis is based on Fe(2+) and ultrasound assisted nucleation and growth at a constant temperature in a range of 25-70 °C. Single-crystalline Fe3O4 particles of 3-5 nm in diameter are homogeneously distributed throughout the spheres and none are on the surface. A systematic optimization of reaction parameters results in isolated, porous, and uniform Fe3O4-MnO2 composite spheres. The spheres' average diameter is dependent on the temperature, and thus is controllable in a range of 0.7-1.28 µm. The involved growth mechanism is discussed. The specific capacitance is optimized at an Fe/Mn atomic ratio of r = 0.075 to be 448 F/g at a scan rate of 5 mV/s, which is nearly 1.5 times that of the extremely high reported value for MnO2 nanostructures (309 F/g). Especially, such a structure allows significantly improved stability at high charging rates. The composite has a capacitance of 367.4 F/g at a high scan rate of 100 mV/s, which is 82% of that at 5 mV/s. Also, it has an excellent cycling performance with a capacitance retention of 76% after 5000 charge/discharge cycles at 5 A/g.