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The necessity for effective wastewater treatment and purification has grown as a result of the increasing pollution issues brought on by industrial and municipal wastewater. Membrane bioreactor (MBR) technology stands out when compared to other treatment methods because of its high efficiency, environmental friendliness, small footprint, and ease of maintenance. However, the development and application of membrane bioreactors has been severely constrained by the higher cost and shorter service life of these devices brought on by membrane biofouling issues resulting from contaminants and bacteria in the water. The nanoscale size of the electrospinning products provides unique microstructure, and the technology facilitates the production of structurally different membranes, or the modification and functionalization of membranes, which makes it possible to solve the membrane fouling problem. Therefore, many current studies have attempted to use electrospinning in MBRs to address membrane fouling and ultimately improve treatment efficacy. Meanwhile, in addition to solving the problem of membrane fouling, the fabrication technology of electrospinning also shows great advantages in constructing thin porous fiber membrane materials with controllable surface wettability and layered structure, which is helpful for the performance enhancement of MBR and expanding innovation. This paper systematically reviews the application and research progress of electrospinning in MBRs. Firstly, the current status of the application of electrospinning technology in various MBRs is introduced, and the relevant measures to solve the membrane fouling based on electrospinning technology are analyzed. Subsequently, some new types of MBRs and new application areas developed with the help of electrospinning technology are introduced. Finally, the limitations and challenges of merging the two technologies are presented, and pertinent recommendations are provided for future research on the use of electrospinning technology in membrane bioreactors.
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Lithium-sulfur batteries (LSBs) have the advantages of high theoretical specific capacity, excellent energy density, abundant elemental sulfur reserves. However, the LSBs is mainly limited by shuttling of lithium polysulfides (LiPSs), slow reaction kinetics of sulfur cathode. For solving the above problems, by developing high-performance battery separators, the reversible capacity, Coulombic efficiency (CE) and cycle life of LSBs can be effectively enhanced. Carbon-free based metal compounds are expected to be highly efficient separator modifiers for a new generation of high-performance LSBs by virtue of superior chemical adsorption capacity, strong catalytic properties and excellent lithophilicity to a certain extent. They can give play to the synergistic effect of their "adsorption-catalysis" sites to accelerate the redox kinetics of LiPSs, and their good lithophilicity can accelerate the Li+ transport kinetics, thus showing more remarkable electrochemical performances. However, a comprehensive summary of carbon-free metal compounds-modified separators for LSBs is still lacking. Here, this review systematically summarizes the researching progresses and performance characteristics of carbon-free-based metal compounds modified materials for separators of LSBs, and summarizes the corresponding mechanisms of using carbon-based separators to enhance the performance of LSBs. Finally, the review also looks forward to the prospects of LSBs using carbon-free metal compounds separators.
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Solid-state lithium metal batteries (SSLMBs) have gained significant attention in energy storage research due to their high energy density and significantly improved safety. But there are still certain problems with lithium dendrite growth, interface stability, and room-temperature practicality. Nature continually inspires human development and intricate design strategies to achieve optimal structural applications. Innovative solid-state electrolytes (SSEs), inspired by diverse natural species, have demonstrated exceptional physical, chemical, and mechanical properties. This review provides an overview of typical bionic-structured materials in SSEs, particularly those mimicking plant and animal structures, with a focus on their latest advancements in applications of solid-state lithium metal batteries. Commencing from plant structures encompassing roots, trunks, leaves, flowers, fruits, and cellular levels, the detailed influence of biomimetic strategies on SSE design and electrochemical performance are presented in this review. Subsequently, the recent progress of animal-inspired nanostructures in SSEs is summarized, including layered structures, surface morphologies, and interface compatibility in both two-dimensional (2D) and three-dimensional (3D) aspects. Finally, we also evaluate the current challenges and provide a concise outlook on future research directions. We anticipate that the review will provide useful information for future reference regarding the design of bionic-structured materials in SSEs.
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Compounding of suitable fillers with PEO-based polymers is the key to forming high-performance electrolytes with robust network structures and homogeneous Li+-transport channels. In this work, we innovatively and efficiently prepared Al2O3 nanofibers and deposited an aqueous dispersion of Al2O3 into a membrane via vacuum filtration to construct a nanofiber membrane with a three-dimensional (3D) network structure as the backbone of a PEO-based solid-state electrolyte. The supporting effect of the nanofiber network structure improved the mechanical properties of the reinforced composite solid-state electrolyte and its ability to inhibit the growth of Li dendrites. Meanwhile, interconnected nanofibers in the PEO-based electrolyte and the strong Lewis acid-base interactions between the chemical groups on the surface of the inorganic filler and the ionic species in the PEO matrix provided facilitated pathways for Li+ transport and regulated the uniform deposition of Li+. Moreover, the interaction between Al2O3 and lithium salts as well as the PEO polymer increased free Li+ concentration and maintained its stable electrochemical properties. Hence, assembled Li/Li symmetric cells achieved a cycle life of more than 2000 h. LFP/Li and NMC811/Li cells provided high discharge specific capacities of up to 146.9 mA h g-1 (0.5C and 50 °C) and 166.9 mA h g-1 (0.25C and 50 °C), respectively. The prepared flexible self-supporting 3D nanofiber network structure construction can provide a simple and efficient new strategy for the exploitation of high-performance solid-state electrolytes.
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Iodide perovskites have demonstrated their unprecedented high efficiency and commercialization potential, and their superior optoelectronic properties, such as high absorption coefficient, high carrier mobility, and narrow direct bandgap, have attracted much attention, especially in solar cells, photodetectors, and light-emitting diodes (LEDs). However, whether it is organic iodide perovskite, organic-inorganic hybrid iodide perovskite or all-inorganic iodide perovskite the stability of these iodide perovskites is still poor and the contamination is high. In recent years, scholars have studied more iodide perovskites to improve their stability as well as optoelectronic properties from various angles. This paper systematically reviews the strategies (component engineering, additive engineering, dimensionality reduction engineering, and phase mixing engineering) used to improve the stability of iodide perovskites and their applications in recent years.
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The unsatisfactory lithium-ion conductivity (σ) and limited mechanical strength of polymer solid electrolytes hinder their wide applications in solid-state lithium metal batteries (SSLMBs). Here, a thin piezoelectric polymer solid electrolyte integrating electromechanical coupling and ferroelectric polarization effects has been designed and prepared to achieve long-term stable cycling of SSLMBs. The ferroelectric Bi4Ti3O12 nanoparticle (BIT NPs) loaded poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric nanofibers (B-P NFs) membranes are introduced into the poly(ethylene oxide) (PEO) matrix, endowing the composite electrolyte with unique polarization and piezoelectric effects. The piezoelectric nanofiber membrane with a 3D network structure not only promotes the dissociation of lithium (Li) salts through the polarization effect but also cleverly utilizes the coupling effect of a mechanical stress-local electric field to achieve dynamic regulation of the Li electroplating process. Through the corresponding experimental tests and density functional theory calculations, the intrinsic mechanism of piezoelectric electrolytes improving σ and suppressing Li dendrites is fully revealed. The obtained piezoelectric electrolyte has achieved stable cycling of LiFePO4 batteries over 2000 cycles and has also shown good practical application potential in flexible pouch batteries.
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Converting CO2 into valuable chemicals can provide a new path to mitigate the greenhouse effect, achieving the aim of "carbon neutrality" and "carbon peaking". Among numerous electrocatalysts, Zn-based materials are widely distributed and cheap, making them one of the most promising electrocatalyst materials to replace noble metal catalysts. Moreover, the Zn metal itself has a certain selectivity for CO. After appropriate modification, such as oxide derivatization, structural reorganization, reconstruction of the surfaces, heteroatom doping, and so on, the Zn-based electrocatalysts can expose more active sites and adjust the d-band center or electronic structure, and the FE and stability of them can be effectively improved, and they can even convert CO2 to multi-carbon products. This review aims to systematically describe the latest progresses of modified Zn-based electrocatalyst materials (including organic and inorganic materials) in the electrocatalytic carbon dioxide reduction reaction (eCO2RR). The applications of modified Zn-based catalysts in improving product selectivity, increasing current density and reducing the overpotential of the eCO2RR are reviewed. Moreover, this review describes the reasonable selection and good structural design of Zn-based catalysts, presents the characteristics of various modified zinc-based catalysts, and reveals the related catalytic mechanisms for the first time. Finally, the current status and development prospects of modified Zn-based catalysts in eCO2RR are summarized and discussed.
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Despite the impressive merits of gel electrolytes for aqueous Zn-ion batteries, it remains a significant challenge to design and develop the gel electrolyte with high ionic conductivity, excellent dimensional stability, and long cycle life. Herein, a composite electrolyte (PTP) with thermolastic polyurethane -poly(m-phenylene isophthalamide) nanofiber-reinforced polyvinyl alcohol gel strategy is proposed for highly reversible Zn plating/stripping. Mechanically robust and ultrathin PTP contains functional groups for building ion migration channels and immobilizing water molecules, which accelerates Zn2+ migration and mitigates water-related side reactions. Thus, the Zn anodes exhibit excellent electrochemical performance involving high cycling stability (6500 h at 5 mA cm-2 , 5 mA h cm-2 ) and achieving an exceptional cumulative capacity of more than 16 000 mA h cm-2 . This enhancement is well maintained when combined with MnO2 cathode. This work provides a reasonable solution for stabilizing Zn anodes and also provides new ideas for the modification of nanofiber-reinforced gel electrolytes.
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Developing highly efficient bi-functional noble-metal-free oxygen electrocatalysts with low-cost and scalable synthesis approach is challenging for zinc-air batteries (ZABs). Due to the flexible valence state of manganese, MnF2 is expected to provide efficient OER. However, its insulating properties may inhibit its OER process to a certain degree. Herein, during the process of converting the manganese source in the precursor of porous carbon nanofibers (PCNFs) to manganese fluoride, the manganese source is changed to manganese acetate, which allows PCNFs to grow a large number of hollow carbon nanorods (HCNRs). Meanwhile, manganese fluoride will transform from the aggregation state into uniformly dispersed MnF2 nanodots, thereby achieving highly efficient OER catalytic activity. Furthermore, the intrinsic ORR catalytic activity of the HCNRs/MnF2 @PCNFs can be enhanced due to the charge modulation effect of MnF2 nanodots inside HCNR. In addition, the HCNRs stretched toward the liquid electrolyte can increase the capture capacity of dissolved oxygen and protect the inner MnF2 , thereby enhancing the stability of HCNRs/MnF2 @PCNFs for the oxygen electrocatalytic process. MnF2 surface-modulated HCNRs can strongly enhance ORR activity, and the uniformly dispersed MnF2 can also provide higher OER activity. Thus, the prepared HCNRs/MnF2 @PCNFs obtain efficient bifunctional oxygen catalytic ability and high-performance rechargeable ZABs.
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The development of highly safe and low-cost solid polymer electrolytes for all-solid-state lithium batteries (ASSLBs) has been hindered by low ionic conductivity, poor stability under high-voltage conditions, and severe lithium-dendrite-induced short circuits. In this study, Li-doped MgO nanofibers bearing reactive surface defects of scaled-up production are introduced to the poly(ethylene oxide) (PEO)/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) system. The characterizations and density functional theory calculations reveal that TFSI- is strongly adsorbed on the nanofibers based on the electrostatic interactions of surface oxygen vacancies and the formation of Li-N and Li-O bonds derived from the exposed Li. Additionally, the introduced Li exposed near oxygen vacancies may be liberated from the lattice and engage in the formation of Li-rich domains. Therefore, a high ionic conductivity of 1.48 × 10-4 S cm-1 for the solid electrolyte at 30 °C and excellent cycling stability for the assembled battery, with a discharge capacity retention of 85.2% after 1500 cycles at 2C, can be achieved. Furthermore, the increased coordination of EO chains in the Li-rich region and chemical interactions with nanofibers substantially improve the antioxidant stability of the solid electrolyte, endowing the LiNi0.8Co0.1Mn0.1O2/Li battery with a long lifespan of more than 700 cycles. The results of this study suggest that the surface defects of 1D oxide nanostructures can substantially improve the Li+ diffusion kinetics. This study provides insight into the construction of Li-rich regions for high-voltage ASSLBs.
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Recently, the multi-level interwoven structured micro/nano fiber membranes with coarse and fine overlaps have attracted lots of attention due to their advantages of high surface roughness, high porosity, good mechanical strength, etc., but their simple and direct preparation methods still need to be developed. Herein, the multi-level structured micro/nano fiber membranes were prepared novelly and directly by a one-step electrospinning technique based on the principle of micro-phase separation caused by polymer incompatibility using polystyrene (PS) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as raw materials. It was found that different spinning fluid parameters and various spinning process parameters will have a significant impact on its morphology and structures. Under certain conditions (the concentration of spinning solution is 18 wt%, the mass ratio of PS to PVDF-HFP is 1:7, the spinning voltage is 30 kV, and the spinning receiving distance is 18 cm), the PS/PVDF-HFP membrane with optimal multi-level structured micro/nano fiber membranes could be obtained, which present an average pore size of 4.38 ± 0.10 µm, a porosity of 78.9 ± 3.5%, and a water contact angle of 145.84 ± 1.70°. The formation mechanism of micro/nano fiber interwoven structures was proposed through conductivity and viscosity tests. In addition, it was initially used as a separation membrane material in membrane distillation, and its performance was preliminarily explored. This paper provides a theoretical and experimental basis for the research and development of an efficient and feasible method for the preparation of multi-level micro/nano fiber membranes.
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Elemental doping is one of the most essential techniques for material modification. It is well known that fluorine is considered to be a highly efficient and inexpensive dopant in the field of materials. Fluorine is one of the most reactive elements with the highest electronegativity (χ = 3.98). Compared to cationic doping, anionic doping is another valuable method for improving the properties of materials. Many materials have physicochemical limitations that affect their practical application in the field of catalysis and rechargeable ion batteries. Many researchers have demonstrated that F-doping can significantly improve the performance of materials for practical applications. This paper reviews the applications of various F-doped materials in photocatalysis, electrocatalysis, lithium-ion batteries, and sodium-ion batteries, as well as briefly introducing their preparation methods and mechanisms to provide researchers with more ideas and options for material modification.
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Porous carbon-based electrocatalysts for cathodes in zinc-air batteries (ZABs) are limited by their low catalytic activity and poor electronic conductivity, making it difficult for them to be quickly commercialized. To solve these problems of ZABs, copper nanodot-embedded N, F co-doped porous carbon nanofibers (CuNDs@NFPCNFs) are prepared to enhance the electronic conductivity and catalytic activity in this study. The CuNDs@NFPCNFs exhibit excellent oxygen reduction reaction (ORR) performance based on experimental and density functional theory (DFT) simulation results. The copper nanodots (CuNDs) and N, F co-doped carbon nanofibers (NFPCNFs) synergistically enhance the electrocatalytic activity. The CuNDs in the NFPCNFs also enhance the electronic conductivity to facilitate electron transfer during the ORR. The open porous structure of the NFPCNFs promotes the fast diffusion of dissolved oxygen and the formation of abundant gas-liquid-solid interfaces, leading to enhanced ORR activity. Finally, the CuNDs@NFPCNFs show excellent ORR performance, maintaining 92.5% of the catalytic activity after a long-term ORR test of 20000 s. The CuNDs@NFPCNFs also demonstrate super stable charge-discharge cycling for over 400 h, a high specific capacity of 771.3 mAh g-1 and an excellent power density of 204.9 mW cm-2 as a cathode electrode in ZABs. This work is expected to provide reference and guidance for research on the mechanism of action of metal nanodot-enhanced carbon materials for ORR electrocatalyst design.
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Oily particles pollution poses a tremendous threat to people's health, so it is urgent to develop air filtration materials with the ability of removing fine oily particles effectively. In this study, a nylon 6 multi-stage structured nanofiber membrane (PA6 MSNM) for effective air filtration of fine oily particles was designed and fabricated by adding a certain amount of tetrabutylammonium hexafluorophosphate (TBAHP) via one-step electrospinning. The PA6 MSNMs were composed of coarse trunk fibres and fine branching fibres. Benefiting from the properties of small pore size and high porosity, the resulting PA6 MSNMs exhibited high average filtration efficiency of 99.80% for oily aerosol particles of 0.20-4.59 µm, a low pressure drop of 251â Pa, and the high quality factor of 0.0248â Pa-1. More importantly, its filtration efficiencies for oily aerosol particles of 0.25 and 0.30 µm were up to 99.99% and 100.00%, respectively. It is expected that the multi-stage electrospun nanofiber membranes would have wide application prospects in air filtration, particularly for filtering oily particles.
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A 3D crimped sulfonated polyethersulfone-polyethylene oxide(C-SPES/PEO) nanofiber membrane and long-range lanthanum cobaltate(LaCoO3 ) nanowires are collectively doped into a PEO matrix to acquire a composite solid electrolyte (C-SPES-PEO-LaCoO3 ) for all-solid-state lithium metal batteries(ASSLMBs). The 3D crimped structure enables the fiber membrane to have a large porosity of 90%. Therefore, under the premise of strongly guaranteeing the mechanical properties of C-SPES-PEO-LaCoO3 , the ceramic nanowires conveniently penetrated into the 3D crimped SPES nanofiber without being blocked, which can facilitate fast ionic conductivity by forming 3D continuous organic-inorganic ion transport pathways. The as-prepared electrolyte delivers an excellent ionic conductivity of 2.5 × 10-4 S cm-1 at 30 °C. Density functional theory calculations indicate that the LaCoO3 nanowires and 3D crimped C-SPES/PEO fibers contribute to Li+ movement. Particularly, the LiFePO4 /C-SPES-PEO-LaCoO3 /Li and NMC811/C-SPES-PEO-LaCoO3 /Li pouch cell have a high initial discharge specific capacity of 156.8 mAh g-1 and a maximum value of 176.7 mAh g-1 , respectively. In addition, the universality of the penetration of C-SPES/PEO nanofibers to functional ceramic nanowires is also reflected by the stable cycling performance of ASSLMBs based on the electrolytes, in which the LaCoO3 nanowires are replaced with Gd-doped CeO2 nanowires. The work will provide a novel approach to high performance solid-state electrolytes.
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In this study, the yttrium trifluoride-doped polyacrylonitrile(PAN) based carbon nanofibers (YF3-PAN-CNFs) are successfully designed and prepared through the electro-blow spinning and carbonization strategies. And the YF3-PAN-CNFs acted as main materials of functional layer for modifying separator of lithium metal batteries are systematically studied and analyzed. The prepared CNFs have long-range ordered structures and high conductivity, which can extremely improve the transport of lithium ions and electrons during charge-discharge processes. The lithiophilic YF3 nanoparticles formed in the carbonization process can endow enough active sites to produce alloying reaction with Li, which makes the plating/stripping of Li more uniform. For the assembled Li||lithium iron phosphate (LiFePO4) battery, it still maintains a high specific discharge capacity of 137.1 mAh g-1 after 500 cycles at 0.5 C, which there is almost no specific discharge capacity degradation after long cycle. The modified separator for the Li||Li symmetric battery can effectively suppress the growth of lithium dendrites and improve cycle stability. Meanwhile, based on the strong chemical bonding between YF3 and lithium polysulfide combining the effectively physical confinement of the YF3-PAN-CNFs coating layer, the "shuttle effect" of lithium polysulfide also can be greatly suppressed. Thus the assembled Li||S battery using the separator has excellent electrochemical performance. Therefore, the YF3-PAN-CNFs modified separator will have a promising application prospect in lithium metal batteries even other high performance secondary batteries.
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The surface charge density enhancement by incorporating conductive paths into organic/inorganic piezoelectric composites is considered to be an effective way to achieve high-performance piezoelectric nanogenerators (PENGs). However, it is challenging to boost the charge density of aligned piezoelectric nanofibers due to the difficulty in efficiently building well-distributed conductive paths in their dense structure. In this work, a charge boosting strategy was proposed for enhancing the surface charge density of aligned piezoelectric nanofibers, that is, synchronously preparing piezoelectric/conductive hybrid nanofibers to realize the effective conductive paths for transferring the underlying charges to the surface of the PDMS/BaTiO3 composites. To this end, antimony-doped tin oxide (ATO) conductive nanofibers and barium titanate (BaTiO3) piezoelectric nanofibers with the same preparation conditions were selected and synchronously prepared by the polymer template electrospinning technology, followed by the calcination process. Benefiting from the well-distributed conductive paths for transferring the charges, the open-circuit voltage and short-circuit current of a PENG with 12 wt% ATO in hybrid nanofibers reached 46 V and 14.5 µA (30 kPa pressure), respectively, which were much higher than the pristine BaTiO3-based PENG. The high piezoelectric performance of the developed PENGs guaranteed their great potential applications in powering wearable microelectronics and monitoring human activity. This charge boosting strategy via the piezoelectric/conductive hybrid nanofibers may inspire the further development of high-performance energy harvesting technology.
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In this paper, a novel, nonbinary (NB) LDPC-coded probabilistic shaping (PS) scheme for a Rayleigh fading channel is proposed. For the NB LDPC-coded PS scheme in Rayleigh fading channel, the rotation angle of 16 quadrature amplitude modulation (QAM) constellations, 64QAM constellations and 256QAM constellations are optimized by the exhaustive search. The simulation results verify the information-theoretical analysis. Compared with the binary LDPC-coded PS scheme for Rayleigh fading channel, the proposed NB LDPC-coded PS scheme can improve error performance. In summary, the proposed NB LDPC-coded PS scheme for Rayleigh fading channel is reliable and thus suitable for future communication systems.
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Gas sensors play an irreplaceable role in industry and life. Different types of gas sensors, including metal-oxide sensors, are developed for different scenarios. Titanium dioxide is widely used in dyes, photocatalysis, and other fields by virtue of its nontoxic and nonhazardous properties, and excellent performance. Additionally, researchers are continuously exploring applications in other fields, such as gas sensors and batteries. The preparation methods include deposition, magnetron sputtering, and electrostatic spinning. As researchers continue to study sensors with the help of modern computers, microcosm simulations have been implemented, opening up new possibilities for research. The combination of simulation and calculation will help us to better grasp the reaction mechanisms, improve the design of gas sensor materials, and better respond to different gas environments. In this paper, the experimental and computational aspects of TiO2 are reviewed, and the future research directions are described.
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In this study, a novel fluorine-containing emulsion and 3, 4-ethylene dioxyethiophene (EDOT) co-doped poly-m-phenyleneisophthalamide (PMIA) nanofiber membrane (EDOT/F-PMIA), as the separator of lithium-sulfur battery, was tactfully prepared via electrospinning. The multi-scale EDOT/F-PMIA nanofiber membrane can be served as the matrix to fabricate gel polymer electrolyte (GPE). Furthermore, under the influence of fluorine-containing emulsion and EDOT, the PMIA-based GPE possessed excellent thermostability, eminent mechanical property and well-distributed lithium-ions flux. Especially, the pore size of the nanofiber membrane decreased after adding the fluorine-containing emulsion and EDOT. And the element S and O in EDOT with lone pair electrons were capable of binding with the lithium polysulfides, which was conducive to inhibiting the "shuttle effect" of lithium polysulfides by combining the physical confinement and chemical binding. Therefore, the lithium-sulfur battery assembled with the EDOT/F-PMIA separator exhibited excellent electrochemical performance, which delivered a high initial capacity of 851.9â mAh g-1 and maintained a discharge capacity of 641.1â mAh g-1 after 200 cycles with a capacity retention rate of 75.2% at 0.5â C.