Strong Chemical Interaction Research Articles

Biochar supported CuFe layered double hydroxide composite as a sustainable adsorbent for efficient removal of anionic azo dye from water

This study reports the synthesis of date palm waste-derived biochar (B) supported CuFe layered double hydroxides (CuFe LDH) composite by facile co-precipitation method. The adsorption performance of B-CuFe composite was evaluated for the removal of Eriochrome black T (EBT), as a model anionic azo dye, from the aqueous phase. The B-CuFe composites were characterized by FTIR, XRD, TGA, SEM-EDX and BET techniques. Characterization results revealed the synergistic effect of biochar and CuFe LDH has resulted in substantial improvement in physicochemical characteristics (i.e. surface functionality, surface area and surface morphology) of B-CuFe composite, which promotes rapid and improved adsorption of (EBT) from the solution. The B-CuFe composite with 2.5 g loading of biochar onto CuFe LDH - showed better adsorption performance than that of other B-CuFe composites. The adsorption process of EBT onto B-CuFe composite was well described by the RSM models (with R 2 = 0 . 964 – 0 . 999 ). Acidic pH (2–5) and higher temperature favored the adsorption of EBT onto B-CuFe composite, and almost (70–85%) of EBT was removed from the water within the first 15 min. The highest adsorption capacity, 565.32 mg/g of EBT onto B-CuFe composite, was obtained at pH 2.5 and 45 °C. The adsorption mechanism associated with the strong electrostatic and chemical interactions of EBT sulfonated anions (SO 3 − ) with protonated hydroxyl surface groups ( OH 2 + ) of B-CuFe composite. The B-CuFe composite exhibited better EBT removal in the presence of co-existing anions and demonstrated excellent reusability performance (11% reduction) after five successive cycles. The results demonstrated that the B-CuFe composite has a great potential to be employed as a sustainable and cost-effective adsorbent for the purification of dye contaminated water bodies. • Sustainable biochar-CuFe composite was fabricated by the coprecipitation method. • B-CuFe exhibited improved physicochemical properties than pure biochar and CuFe. • B-CuFe removed 85% of Eriochrome black T dye from the water in 15 min. • The maximum adsorption capacity of B-CuFe was 565.32 mg/g at 45 °C. • B-CuFe composite exhibited excellent reusability performance.

Eco-friendly carboxymethyl cellulose hydrogels filled with nanocellulose or nanoclays for agriculture applications as soil conditioning and nutrient carrier and their impact on cucumber growing

In this work, carboxymethyl cellulose (CMC) hydrogels were produced via chemical crosslink with citric acid and filled with nanocellulose (NC), montmorillonite, or vermiculite, in different contents. The FTIR results indicated a strong chemical interaction between NC or vermiculite and the CMC, increasing the hydrogen bond energies by the fillers' participation in the crosslinking, reflecting in the water absorption (WA). Higher filler contents interacted more with the matrix, resulting in a denser hydrogel with lower WA capacity. The montmorillonite did not alter the hydrogels' structure due to its low compatibility with the CMC, doubling the WA values at low contents. The hydrogels' thermal stability was maintained after the fillers' addition. NPK fertilizer was added to selected formulations, and results indicated success in NPK encapsulation. Fertilizer release in water and soil indicated a slow-release, and the rate was dependent on the filler; all fillers showed a low rate than the CMC pristine hydrogel. The Korsmeyer-Peppas model indicated that vermiculite is not adequate for agriculture applications due to the diffusion mechanism, while nanocellulose and montmorillonite showed crucial results for the field. The in vivo tests demonstrate hydrogels' efficiency filled with 3% NC or 1% montmorillonite in the nutrients-controlled release.

Large-scale synthesis of Fe9S10/Fe3O4@C heterostructure as integrated trapping-catalyzing interlayer for highly efficient lithium-sulfur batteries

• A large-scale synthetic route to obtain core-shell Fe 9 S 10 /Fe 3 O 4 @C heterostructures. • Fe 9 S 10 /Fe 3 O 4 @C can effectively trap LiPS and promote the conversion kinetics. • The Fe 9 S 10 /Fe 3 O 4 heterointerface offers a moderate chemical bonding with LiPS. • The cell with Fe 9 S 10 /Fe 3 O 4 @C interlayer exhibits enhanced rate and cycling capability. The shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish electrocatalysis of polysulfides conversion lead to severe capacity decay and poor rate capability, which is a determining factor for limiting the practical applications of lithium-sulfur (Li-S) batteries. To address such issues, a novel core-shell Fe 9 S 10 /Fe 3 O 4 @C architecture with well-defined heterointerfaces as a multifunctional polysulfides barrier for Li-S batteries is reported here. The spherical Fe 9 S 10 /Fe 3 O 4 @C heterostructure can be prepared by spray-drying technology on a large-scale and followed by a one-pot in-situ carbothermal reaction. With both physical entrapments by carbon shells and strong chemical interaction with Fe 9 S 10 /Fe 3 O 4 heterostructure cores, this constructed dense-packing architecture alleviates the shuttle effect. The mechanisms involved in the Fe 9 S 10 /Fe 3 O 4 @C trapping interlayer are confirmed by both experimental results and density functional theory (DFT) calculations. Moreover, due to its high conductivity and intrinsic catalytic activity, the Fe 9 S 10 /Fe 3 O 4 @C facilitates fast electron/ion transport and greatly improves the conversion of LiPSs. Benefit from the integrated trapping-catalyzing effect, the Li-S cell constructed with a Fe 9 S 10 /Fe 3 O 4 @C interlayer exhibits enhanced cycling stability (a low capacity fading rate of 0.08% per cycle for 500 cycles at 1 C) and outstanding rate performance (660 mAh g −1 at 5 C). Even under a high areal sulfur loading of 3 mg cm −2 , the high discharge capacity and capacity retention ratio can also be obtained. This work offers an insight into the construction of multi-functional heterostructures for high-performance Li-S batteries.

Embedding Fe3C and Fe3N on a Nitrogen-Doped Carbon Nanotube as a Catalytic and Anchoring Center for a High-Areal-Capacity Li-S Battery.

The biggest obstacles of putting lithium-sulfur batteries into practice are the sluggish redox kinetics of polysulfides and serious "shuttle effect" under high sulfur mass loading and lean-electrolyte conditions. Herein, Fe3C/Fe3N@nitrogen-doped carbon nanotubes (NCNTs) as multifunctional sulfur hosts are designed to realize high-areal-capacity Li-S batteries. The Fe3N and Fe3C particles attached to NCNT can promote the conversion of polysulfides. Besides, NCNT can not only enhance the chemisorption of polysulfides but also increase the special surface area and electrical conductivity by constructing a three-dimensional skeleton network. Integrating the merits of high electrical conductivity, high catalytic activity, and strong chemical binding interaction with lithium polysulfides (LiPSs) to achieve in situ anchoring conversion, the Fe3C/Fe3N@NCNT multifunctional hosts realize high sulfur mass loading and accelerate redox kinetics. The novel Fe3C/Fe3N@NCNT/S composite cathode exhibits steady cycle ability and a high areal capacity of 9.10 mAh cm-2 with a sulfur loading of 13.12 mg cm-2 at 2.20 mA cm-2 after 50 cycles.

Recycling valuable cobalt from spent lithium ion batteries for controllably designing a novel sea-urchin-like cobalt nitride-graphene hybrid catalyst: Towards efficient overall water splitting

Along with the continuous consumption in lithium-ion batteries (LIBs), the price of cobalt is inevitably going up in recent years. Therefore, recycling valuable Co element from spent devices, and boosting its service efficiency are becoming two indispensable approaches to promote the utilization of Co in various energy conversion/storage devices. Herein, we realize the recovery of Co from spent LIBs and synthesize a three–dimensional (3D) sea-urchin-like cobalt nitride composite material (labeled as CoN-Gr-2), which is used as a bi-functional catalyst for water splitting. Benefiting from the intrinsic high conductivity, larger surface area and unique 3D sea–urchin–like architecture, CoN-Gr-2 shows an excellent electron transfer efficiency, highly exposed active sites as well as the superior mass transport capacity. The CoN-Gr-2 catalyst exhibits low overpotentials of 128.9 mV and 280 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which are comparable to the commercial 20 wt% Pt/C and RuO2 catalysts. Moreover, when adopting CoN-Gr-2 as both anode and cathode materials for overall water splitting (in 1.0 M KOH electrolyte), the assembled cell achieves a current density of 10 mA cm−2 at 1.61 V, which almost close to that of Pt/C||RuO2 benchmark (1.60 V), demonstrating its superior water-splitting efficiency. Meanwhile, the CoN catalysts exhibit strong chemical interaction with the Gr support, suppressing the aggregation of CoN catalysts and maintains their high activity during HER and OER reactions. So, the cell exhibits a high current retention of 97.3% after 40 h. This work successfully develops an industrial chain from recycling Co wastes in spent energy devices to controllably designing 3D sea-urchin-like CoN-Gr with high water splitting efficiency. Therefore, it could further promote the efficient utilization of valuable Co element in various energy devices.

Converting Ag3PO4/CdS/Fe doped C3N4 based dual Z-scheme photocatalyst into photo- Fenton system for efficient photocatalytic phenol removal

In this work, a dual Z-scheme Ag3PO4/CdS/Fe-g-C3N4 (AP/CdS/FeCN) photocatalyst was prepared by precipitation- deposition method. AP/CdS/FeCN photocatalyst was converted into the heterogenous photo-Fenton system with the addition of H2O2. The synergistic coupling between AP/CdS/FeCN and H2O2 resulted in enhanced for phenol degradation, with a rate constant of constant 6.2×10−4s-1, which is 1.31 and 1.61 times than that of AP/CdS/FeCN and Fe2O3/H2O2. The enhancement in photodegradation was attributed to (i) more regeneration of Fe2+ ions, (ii) enhanced visible light absorption, (iii) elevated redox potential due to more hydroxyl radical’s formation, and (iv) low Fe leaching in the reaction solution. As indicated by EIS, PL, and trapping experiments, photoinduced CB electrons of g-C3N4 and CdS were transferred entirely to Fe3+ to regenerate Fe2+ ions to accelerate the Fenton cycle. In comparison to the conventional Fe2O3/H2O2 Fenton process, Fe ion leaching in AP/CdS/FeCN/H2O2 catalytic system was almost negligible. It confirmed strong chemical interaction of Fe3+ with g-C3N4. AP/CdS/FeCN/H2O2 displayed significant catalytic efficacy and firmness for five successive catalytic cycles. Moreover, the AP/CdS/FeCN/H2O2 nanocomposite exhibited substantial mineralization perfomance for other phenolic pollutants. The results demonstrate that AP/CdS/FeCN/H2O2 catalytic system has the potential for water purification.

Layered Double Hydroxide Quantum Dots for Use in a Bifunctional Separator of Lithium-Sulfur Batteries.

Functional separators, which are chemically modified and coated with nanostructured materials, are considered an effective and economical approach to suppressing the shuttle effect of lithium polysulfide (LiPS) and promoting the conversion kinetics of sulfur cathodes. Herein, we report cobalt-aluminum-layered double hydroxide quantum dots (LDH-QDs) deposited with nitrogen-doped graphene (NG) as a bifunctional separator for lithium-sulfur batteries (LSBs). The mesoporous LDH-QDs/NG hybrids possess abundant active sites of Co2+ and hydroxide groups, which result in capturing LiPSs through strong chemical interactions and accelerating the redox kinetics of the conversion reaction, as confirmed through X-ray photoelectron spectroscopy, adsorption tests, Li2S nucleation tests, and electrokinetic analyses of the LiPS conversion. The resulting LDH-QDs/NG hybrid-coated polypropylene (LDH-QDs/NG/PP) separator, with an average thickness of ∼17 μm, has a high ionic conductivity of 2.67 mS cm-1. Consequently, the LSB cells with the LDH-QDs/NG/PP separator can deliver a high discharge capacity of 1227.48 mAh g-1 at 0.1C along with a low capacity decay rate of 0.041% per cycle over 1200 cycles at 1.0C.

In situ growth of Co nanoparticles in Ketjen Black for enhanced electrochemical performances of lithium-sulfur battery cathode

Lithium–sulfur (Li−S) batteries have the advantages of ultra-high theoretical energy density, low cost, and being environmentally friendly. However, the low S loading “shuttling” effect of intermediate lithium polysulfides in redox reactions and short cycle life limit their commercial applications. In this study, a facile, low-cost high-temperature reduction method was used to synthesize nano metallic Co particles in situ in Ketjen Black (KB) pores with excellent physical properties for nano Co/KB composites formation. In these composites, the particle size of Co is 5–30 nm, which is helpful to promote the transfer of electronic and ionic charges. Moreover, the catalytic effect of nano Co/KB composites and the strong chemical interactions of the Co–S bond were demonstrated, which significantly prohibits soluble polysulfides from migrating out of the KB skeleton because of the strong adsorption, enhancing the electrochemical performances of Li−S batteries. With a high S areal loading of 3 mg cm−2, the initial discharge specific capacity of the Co/KB/S cathode reached 1249.0 mAh g−1 at 0.05 C, while at 0.5 C the initial specific capacity of 785.5 mAh g−1 was achieved, and after 500 cycles the specific capacity maintained at 352.3 mAh g−1 with a fade rate of only 0.09% per cycle.

Chemical Functionalization of Carbon Nanotubes with Polymers: A Brief Overview

Carbon nanotubes (CNTs), the one-dimensional allotropes of carbon, have attracted noteworthy research interest since their discovery in 1991 owing to their large aspect ratio, low mass density, and unique chemical, physical, and electronic properties that provide exciting possibilities for nanoscale applications. Nonetheless, two major issues should be considered when working with this sort of nanomaterial: their strong agglomerating tendency, since they are typically present as bundles or ropes of nanotubes, and the metallic impurities and carbonaceous fragments that go along with the CNTs. The successful utilization of CNTs in a wide variety of applications—in particular, in the field of polymer composites—depends on their uniform dispersion and the development of a strong chemical interaction with the polymeric matrix. To achieve these aims, chemical functionalization of their sidewalls and tips is required. In this article, a brief overview of the different approaches for CNT modification using polymers is provided, focusing on the covalent functionalization via “grafting to” or “grafting from” strategies. The characteristics and advantages of each approach are thoroughly discussed, including a few typical and recent examples. Moreover, applications of polymer-grafted CNTs as biosensors, membranes, energy storage substances, and EMI shielding are briefly described. Finally, future viewpoints in this vibrant research area are proposed.

Synthesis of an efficient, and recyclable mesoporous BiVO4/TiO2 direct Z-scheme heterojunction by sonochemical route for photocatalytic hydrogen production and photodegradation of rhodamine B dye in the visible region

Sonicated mesoporous BiVO 4 /TiO 2 heterojunctions were recorded for highly efficient photodegradation of rhodamine B dye and production of hydrogen gas. The heterojunction structures were characterized by XRD, DRS, FTIR, BET, FESEM, HRTEM and PL. The efficiency of the radiation power of ultrasound waves [50–300 Watt/cm 2 ] on dye degradation and efficiency of hydrogen production was established. BiVO 4 shifts the photocatalytic response of titania toward visible region. The photocatalytic efficiency of RhB removal on the nanocomposites surface containing 10 wt% BiVO 4 is 0.021 min −1 tenfold higher than that of bare TiO 2 (0.0023 min −1 ). The optimum concentration of BiVO 4 was found to be 10 wt% that generate hydrogen gas with rate equal to 14.3 mmolg −1 h −1 . Ultrasound radiation is a prime key in reducing the population of particle aggregates and reflects a strong interaction between BiVO 4 and TiO 2 nanoparticles that results in lowering the electron-hole pairs recombination rate and increase the concentration of active sites and amount hydrogen evolved. The production of hydroxyl and superoxide radicals suggest a direct Z-scheme mechanism for explaining the high photocatalytic reactivity of sample. • Novel BiVO 4 /TiO 2 nanocomposites were synthesized by sonochemical route. • A strong chemical interaction between BiVO 4 and TiO 2 nanoparticles. • Z-electron transfer scheme is purposed. • A stable photocatalyst for five consecutive cycles.

Enhancement of Catalytic Activity and Durability of Pt Nanoparticle through Strong Chemical Interaction with Electrically Conductive Support of Magnéli Phase Titanium Oxide.

In this study, we address the catalytic performance of variously sized Pt nanoparticles (NPs) (from 1.7 to 2.9 nm) supported on magnéli phase titanium oxide (MPTO, Ti4O7) along with commercial solid type carbon (VXC-72R) for oxygen reduction reaction (ORR). Key idea is to utilize a robust and electrically conductive MPTO as a support material so that we employed it to improve the catalytic activity and durability through the strong metal-support interaction (SMSI). Furthermore, we increase the specific surface area of MPTO up to 61.6 m2 g−1 to enhance the SMSI effect between Pt NP and MPTO. After the deposition of a range of Pt NPs on the support materials, we investigate the ORR activity and durability using a rotating disk electrode (RDE) technique in acid media. As a result of accelerated stress test (AST) for 30k cycles, regardless of the Pt particle size, we confirmed that Pt/MPTO samples show a lower electrochemical surface area (ECSA) loss (<20%) than that of Pt/C (~40%). That is explained by the increased dissolution potential and binding energy of Pt on MPTO against to carbon, which is supported by the density functional theory (DFT) calculations. Based on these results, we found that conductive metal oxides could be an alternative as a support material for the long-term fuel cell operation.

Reasonably Introduced ZnIn2S4@C to Mediate Polysulfide Redox for Long-Life Lithium-Sulfur Batteries.

In consideration of the inferior rate performance and low sulfur utilization of lithium-sulfur batteries (LSBs), an effective strategy via combining polar materials with the conductive carbon sulfur host is widely applied. Herein, metal organic framework-derived in situ-developed ZnIn2S4@C is innovatively synthesized to mediate lithium polysulfide (LPS) conversion based on high electron conductivity and strong chemical interactions for advanced LSBs. Polar ZnIn2S4 possesses strong chemisorption in keeping with the DFT calculation results and catalytic for LPSs, ensuring a high sulfur utilization. Meanwhile, the hollow non-polar carbon frame possessing hierarchical pores not only provides internal space to contain active species but also accommodates efficient electronic transferring and diffusion of lithium ions in the process of cycling. The above advantages make the electrode possess promising stability and good rate performances, achieving long-term and high-rate cycling. Thus, under a sulfur loading of 1.5 mg cm-2, after 500 cycles, at 2 and 5 C, the as-prepared ZnIn2S4@C@S delivers reversible capacities of 734 mA h g-1 (75.7% of the initial capacity with a dropping rate of 0.015% per cycle) and 504 mA h g-1 (68.5% of the primal capacity with a dropping rate of 0.029% per cycle), respectively. Even at a high sulfur loading of 5.0 mg cm-2, at 5 C, 65.6% of the initial capacity can be maintained with a low fading rate of 0.430% per cycle after 500 loops with a high Coulombic efficiency of around 99.8%.

Entropy-Driven Ultratough Blends from Brittle Polymers.

Polymer blends with synergetic performance play an integral part in modern society. The discovery of compatible polymer systems often relies on strong chemical interactions. By contrast, the role of entropy in polymers is often neglected. In this work, we show that entropy effect could control the phase structure and mechanical behaviors of polymer blends. For weakly interacting polymer pairs, the seemingly small mixing entropy favors the formation of nanoscale cocontinuous structures. The abundant nanointerfaces could initiate large plastic deformations by crazing or shear, thus, transforming brittle polymers (elongation < 9%) into superductile materials (elongation ∼ 146%). The resultant polymer blends display high transparency, strength (∼70 MPa), and toughness (∼60 MJ/m3) beyond most engineering plastics. The principle of entropy-driven blends may also be applied in other polymer systems, offering a strategy to develop mechanically robust bulk polymeric materials for emerging applications such as biomedicine and electronics.

Development of highly active, chemically stable and recyclable magnetic nanophotocatalyst based on plasmonic silver nanoparticles and photosensitive trans‐3‐(trans‐4‐imidazolyl) acrylic acid molecules

This study relates to the preparation of a novel nanophotocatalyst comprising of plasmonic silver nanoparticle, photosensitive trans‐3‐(trans‐4‐imidazolyl) acrylic acid (T3TTIA) and superparamagnetic iron oxide nanoparticles (SPION). This heterogeneous nano‐photocatalyst has been synthesized via hydrothermal route where T3TTIA works as a capping agent and linker for SPION and plasmonic Ag NPs, respectively. Structural, morphological, thermal, magnetic, optical, and catalytic properties have been analyzed in detailed. The spinel cubic type structure of nanocrystals of SPION and silver has been confirmed by XRD analysis. XPS analysis has confirmed the presence of Ag0, Fe3O4, and integral functional group. The strong chemical interaction of localized surface plasmonic Ag nanoparticles and SPION with photosensitive T3TIAA molecule has been revealed by both the IR and XPS analysis. The shape of the final products has been observed as spherical with average particle size of 12 ±0.8 nm (with low degree of agglomeration) as analyzed by scanning electron microscope (SEM) and high resolution transmission electron microscope (HR‐TEM). The superparamagnetic nature and high thermal stability of the products have been revealed by vibrating sample magnetometry (VSM) and thermogravimetric (TG) analysis, respectively. UV‐visible spectrophotometry analysis has confirmed the maximum absorbance peak at ~420 nm, indicates as the characteristic peak of surface plasmon resonance (SPR) for silver nanoparticles with a band gap value of 1.43 eV. Furthermore, Brunauer−Emmett−Teller (BET) analysis has demonstrated mesoporous characteristic of the product which follows type IV isotherms with the average surface area and pore size as 250.492 m2/g and 6.1442 nm, respectively. The potential catalytic applications of the as‐prepared nanocatalysts have been explored for the decolorization of methyl orange (MO), methylene blue (MB), and photo‐reduction of 4‐nitrophenol (4‐NP) under both Visible and UV light irradiations. The catalytic activity of the as‐prepared nanocatalyst has been compared with the recent reported magnetic nano‐catalysts. The SPION@T3TIAA‐Ag nanocatalyst has shown excellent catalytic behavior toward the treatment of the selected industrial dyes and organic pollutant with recovery and reusability capacity up to seven cycles without losing significant catalytic efficiency.

Inversion in usual excitation intensities from solid state phosphor and improved fluorescence of Eu3+ ion in type (IV) deep eutectic solvent

To resolve the issue of aggregation induced quenching (AIQ), poor adhesion/dispersion on film and fiber, limited dispersability/solubility and non biocompatibility issue; phosphor powder particles are generally casted into solution form. It was found in most cases that lanthanide luminescence and lifetime reduced substantially in aqueous medium and ionic liquid. Deep eutectic solvent (DES) has been found to be an alternate and more efficient solvent for lanthanide luminescence. With similar intention we have synthesized europium type (IV) DES (EuDES) via mechanochemical synthesis employing europium nitrate and urea. Fourier transformed infrared spectroscopy (FTIR) studies confirms that in DES, the Eu3+ ion is surrounded by bidentate nitrate ions and urea is coordinated to europium centre by CO group. There is no water molecule in primary coordination sphere of Eu3+ ion. Interestingly with rigid H-bonding and strong chemical interaction offered by DES; Eu3+ CTB is quenched whereas very high intensity of Eu3+ intra f-f transition appears which was reversal from usual trend. Moreover asymmetry ratio was found to be more than 3 with predominantly high intensity of electric dipole transition (EDT) suggesting very asymmetric environment around Eu3+ in DES. But the distribution of europium was found to be very homogenous with luminescence lifetime of ~3.7 ms and point group symmetry ~ C6v. Judd-Ofelt analysis suggested very low non-radiative channels present in DES resulting in extremely high quantum yield ~76% and very high color purity of 94.72% which was also assisted by absence of any water molecule as suggested by FTIR measurement.

Application of ZnO Nanocrystals as a Surface-Enhancer FTIR for Glyphosate Detection

Glyphosate detection and quantification is still a challenge. After an extensive review of the literature, we observed that Fourier transform infrared spectroscopy (FTIR) had practically not yet been used for detection or quantification. The interaction between zinc oxide (ZnO), silver oxide (Ag2O), and Ag-doped ZnO nanocrystals (NCs), as well as that between nanocomposite (Ag-doped ZnO/AgO) and glyphosate was analyzed with FTIR to determine whether nanomaterials could be used as signal enhancers for glyphosates. The results were further supported with the use of atomic force microscopy (AFM) imaging. The glyphosate commercial solutions were intensified 10,000 times when incorporated the ZnO NCs. However, strong chemical interactions between Ag and glyphosate may suppress signaling, making FTIR identification difficult. In short, we have shown for the first time that ZnO NCs are exciting tools with the potential to be used as signal amplifiers of glyphosate, the use of which may be explored in terms of the detection of other molecules based on nanocrystal affinity.

Strong Chemical Interaction between Lithium Polysulfides and Flame‐Retardant Polyphosphazene for Lithium–Sulfur Batteries with Enhanced Safety and Electrochemical Performance

The shuttle effect of lithium polysulfides (LiPS) and potential safety hazard caused by the burning of flammable organic electrolytes, sulfur cathode, and lithium anode seriously limit the practical application of lithium-sulfur (Li-S) batteries. Here, a flame-retardant polyphosphazene (PPZ) covalently modified holey graphene/carbonized cellulose paper is reported as a multifunctional interlayer in Li-S batteries. During the discharge/charge process, once the LiPS are generated, the as-obtained flame-retardant interlayer traps them immediately through the nucleophilic substitution reaction between PPZ and LiPS, effectively inhibiting the shuttling effect of LiPS to enhance the cycle stability of Li-S batteries. Meanwhile, this strong chemical interaction increases the diffusion coefficient for lithium ions, accelerating the lithiation reaction with complete inversion. Moreover, the as-obtained interlayer can be used as a fresh 3D current collector to establish a flame-retardant "vice-electrode," which can trap dissolved sulfur and absorb a large amount of electrolyte, prominently bringing down the flammability of the sulfur cathode and electrolyte to improve the safety of Li-S batteries. This work provides a viable strategy for using PPZ-based materials as strong chemical scavengers for LiPS and a flame-retardant interlayer toward next-generation Li-S batteries with enhanced safety and electrochemical performance.

In-situ constructing uniform polymer network for iron oxide microspheres: A novel approach to improve the cycling stability of the conversion electrodes through chemical interaction

Electrochemical conversion reaction provides potential high-capacity anode materials for Li-ion and Na-ion batteries. However, the inferior cyclability is seriously hindering their applications. Herein, a novel strategy is introduced to improve the performance of conversion-type Fe2O3-AHP composite by using an organic amino-hyperbranched polymer additive. The amino groups of polymers could coordinate with Fe3+ through chemical interaction, and make Fe2O3 particles self-assemble into unique microspheres in solvothermal process. Moreover, the polymer additive in-situ constructs 3D uniform elastic frame work on molecular level in Fe2O3-AHP composite, which could accommodate the volume change and stabilize the Fe2O3 structure during lithiation/delithiation or sodiation/desodiation processes. Therefore, compared with Fe2O3-AHP-500 in which AHP was removed by heat treatment, the Fe2O3-AHP microspheres exhibit excellent long-term Li-storage (98.3% capacity retention rate after 1000 cycles at 2.0 A g−1) and Na-storage cyclabilities and maintain the integrity of microsphere structure after cycling. Furthermore, the polymer additive makes the Fe2O3-AHP microsphere have plenty of nanopores, which facilitate electrolyte infiltration and ion diffusion and thus enhance the kinetic performance. The present study highlights a novel strategy of in-situ construction of stable network on molecular level using polymer additive via strong chemical interaction, which delivers inspiration optimizing the long-term cyclability of conversion-type materials.

First-principles calculation of interfacial stability, energy, electronic properties, ideal tensile strength and fracture toughness of SiC/BN interface

The interfacial properties and electronic structure of $$\beta$$ -SiC (111)/ $$h$$ -BN (0001), including work of adhesion (Wad), interface energy, bonding nature, ideal tensile strength and fracture toughness, were investigated using first-principles calculations. Eight interface models, with two different terminations and four stacking sites, were investigated. The $$\beta$$ -SiC (111) slab, with 10 atomic layers, and the $$h$$ -BN (0001) slab, with two atomic layers, exhibited bulk-like interior features, respectively. The Case II interface, in which the Si atom was located at the center of the B-N bond, had the largest work of adhesion (2.749 J/m2), the smallest interfacial distance (2.02 A), the minimum interface energy (0.473 J/m2) and, thus, the best stability. The valence electron density and partial density of states indicated that there was a strong chemical and electrical interaction between the two sides of the Case II interface. The electronic structure analysis suggested that the interfacial bonding was mainly attributed to the Si-N ionic interaction and the valence electronic hybridization between Si-sp and B-sp. The ideal tensile strength and fracture toughness of the Case II interface were predicted as 13.26 GPa and 0.68–1.887 MPa•m1/2, respectively.

Rational cooperativity of nanospace confinement and rapid catalysis via hollow carbon nanospheres@Nb-based inorganics for high-rate Li-S batteries

The sluggish redox kinetics and shuttling behaviors of intermediate polysulfides are dominant obstacles that hamper the practical applications of Li-S battery. In this work, two types of niobium (Nb)-based inorganics, semiconductive Nb2O5 and conductive NbC, are implanted into hollow carbon nanospheres (HCN) hosts, which can realize the cooperativity of nanospace confinement and high-efficiency catalytic Nb-based inorganics for high-rate Li-S batteries. The initial HCN have adequate hollow space achieving high sulfur loading, interpenetrated mesoporous channels for rapid ion transfer, and developed microporous carbon framework blocking the polysulfides shuttling. While Nb-based inorganics are uniformly located in the mesoporous channels, they can accelerate the conversion kinetics of the polysulfides by strong chemical interaction and high catalytic effect. Furthermore, we demonstrate that the conductive NbC performs much better catalytic activity than the Nb2O5, with significantly improved redox kinetic and cycling performance. The optimized HCN@NbC/S cathode delivers a preeminent reversible capacity of 500 mAh g−1 with a low capacity decay of 0.05% per cycle over 800 cycles at 3 C and a high rate capacity of 752 mAh g−1 under a high current density of 5 C. This work provides a novel strategy to construct desirable multifunctional host favoring cooperative polysulfides interactions via rational integration of physical confinement and high-effective catalytic inorganics for long-cycling stable sulfur cathode.