A series of ion-exchange membranes for vanadium redox flow batteries (VRBs) are prepared by filling the pores of a poly(tetrafluoroethylene) (PTFE) substrate with sulfonated poly(ether ether ketone) ...(SPEEK) and microporous Engelhard titanosilicate-10 (ETS-10). The effects of ETS-10 incorporation and PTFE reinforcement on membrane properties and VRB single-cell performance are investigated using various characterization tools. The results show that these composite membranes exhibit improved mechanical properties and reduced vanadium-ion permeabilities owing to the interactions between ETS-10 and SPEEK, the suppressed swelling of PTFE, and the unique ETS-10 framework. The composite membrane with 3 wt% ETS-10 (referred to as “SE3/P”) exhibits the best membrane properties and highest ion selectivity. The VRB system with the SE3/P membrane exhibits higher cell capacity, higher cell efficiency, and lower capacity decay than that with a Nafion membrane. These results indicate that this composite membrane has potential as an alternative to Nafion in VRB systems.
•Pores of PTFE membrane were filled with SPEEK and ETS-10.•The composite membranes showed enhanced membrane stability.•ETS-10 acted as a permselective barrier to reduce vanadium permeability.•The composite membranes exhibited better VRB cell performance than Nafion.
Among the various separation membranes, the thin-film nanocomposites (TFN) membranes have been widely applied for gas separation. In the present study, TFN hollow fiber membranes using polydopamine ...(PD)-encapsulated ETS-4 (Engelhard titanosilicate-4), PD-ETS-TFN, with a pore size of 3–4 Å were prepared for gas separation applications. The proposed TFN hollow fiber membranes were prepared by condensation-based interfacial polymerization (IP) between poly(ethylenimine) as an aqueous monomer and 1,3,5-benzenetricarbonyl trichloride as an organic monomer on a porous PES poly(ether sulfone) substrate. The dopamine-encapsulated ETS-4 was incorporated inside the polyamide layer to maximize the hydrophilicity of the membrane. Various methods were employed to analyze the structures and characteristics of the ETS-4 and TFN membranes, and tests were conducted to evaluate the permeance of H2, CO2, N2, and CH4 through PD-ETS-TFN. The results revealed a facilitated transport property toward CO2. Due to the molecular sieving effect of the ETS-4, the proposed membranes achieved a permeance as high as 60.4 GPU toward H2 and H2/CO2 selectivity of 14.3.
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•Engelhard titanosilicate-4 was prepared for mixed matrix membranes.•Polyethersulfone hollow fiber membrane was used as a substrate.•Polydopamine-encapsulated ETS-4 thin-film composite hollow fiber membrane was prepared.•Prepared MMMs showed high potential for gas separation.
Sulfonated poly(ether ether ketone) (SPEEK) is a potential polymer for replacing Nafion in vanadium redox flow batteries (VRBs). However, at a high degree of sulfonation, SPEEK displays high ...swelling, poor mechanical stability, and high vanadium crossover. In this study, to improve membrane performance, composite membranes of SPEEK and finely ground microporous AMH-3 (G-AMH-3) are prepared with various G-AMH-3 contents and investigated. The physicochemical and mechanical properties, vanadium permeability, and VRB single cell performance of these SPEEK/G-AMH-3 composite membranes are evaluated using various characterization techniques. Interactions between SPEEK and G-AMH-3, and the permselective property of G-AMH-3, result in the composite membranes exhibiting good mechanical properties and low vanadium crossover. Optimal composite membranes gave a VRB that produced a higher charge–discharge capacity, higher cell efficiency, and better capacity retention than that using Nafion. These results indicate that SPEEK-based composite membranes with improved membrane performance, lower vanadium crossover, and good single cell performance were successfully prepared by incorporating G-AMH-3.
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•The Pt nanoparticles were loaded on outer surface of the MOF-5 by solvent polarity.•CB/Pt/MOF-5 exhibited increased hydrogen storage capacity at room temperature.•CB/Pt/MOF-5 ...exhibited excellent hydrostability under ambient condition.
Metal–organic frameworks (MOFs) have generated considerable interest as a potential candidate for hydrogen storage, owing to their extremely high surface-to-volume ratio and low density. However, practical applications have been limited because of low hydrogen storage capacity at room temperature, and of moisture sensitivity of MOFs. To improve hydrogen storage capacity at room temperature and hydrostability under ambient conditions, platinum (Pt) nanoparticles were introduced on the outer surface of MOF-5, Zn4O(1,4-benzenedicarboxylate)3 that was then coated with hydrophobic microporous carbon black (CB) to generate a CB/Pt/MOF-5 composite. To study the chemical composition, morphology, crystallinity, and properties of the synthesized material, various techniques were employed including wide-angle X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma emission spectrometry, high-resolution transmission electron microscopy, and N2 adsorption–desorption analysis. The characterization analyses confirmed the formation of a novel composite designated as CB/Pt/MOF-5 with a highly crystalline structure, and large specific surface area and pore volume. The hydrogen storage capacity (0.62wt.%) of CB/Pt/MOF-5 was superior to that of pristine MOF-5 (0.44wt.%) by 41%; furthermore, CB/Pt/MOF-5 displayed excellent hydrostability under ambient conditions. Overall, these findings indicate that MOF-5 with improved hydrogen storage capacity and hydrostability was successfully synthesized by introducing Pt nanoparticles and a carbon black layer.
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•Rapid thermal swing adsorption process with multi-fixed beds was proposed for CO2 capture.•Internal heat integration was made by recovering sensible heat from the cooling ...process.•CO2 cyclic capacity of hollow fiber sorbents was improved via multiple adsorption processes.•The energy performance of proposed RTSA process was evaluated by experiments and modeling.
A rapid thermal swing adsorption (RTSA) process with heat integration is considered to be an energy-efficient method for large-scale CO2 capture. Herein, we propose a new heat-integrated RTSA process for post-combustion CO2 capture as a proof-of-concept based on rationally designed multi-fixed beds by incorporating the internal heat integration concept of the moving bed adsorption process. Our proposed RTSA process consists of multiple beds, each of which undergoes four sequential processes, including adsorption, heating, desorption, and cooling in a continuous cyclic mode. Also, the switching time of adsorption/desorption process is determined by CO2 adsorption/desorption kinetics while that of the heating/cooling process is determined by the heat transfer rate. Our unique RTSA design enables internal heat integration by recovering sensible heat from the cooling process. Furthermore, it can enhance the CO2 cyclic capacity of hollow fiber sorbents with high CO2 recovery by performing multiple adsorption processes simultaneously. Most importantly, our economic analysis based on experiments and rigorous mathematical modeling revealed that the energy demand of the optimized RTSA process is estimated to be approximately 272 kWh/t-CO2 with 58% sensible heat recovery. Such low energy penalty is comparable to that of the most mature amine-based absorption process (271 kWh/t-CO2) due to a combination of internal heat integration and enhanced CO2 cyclic capacity, supporting the feasibility of a RTSA process for post-combustion CO2 capture.
•In-situ cyclic voltammetry and impedance analysis were performed under various SOCs.•Polybromide complex accumulated on the Br-side electrode surface.•It showed a positive effect on the adsorption ...of bromide ions.•Charge transfer resistance for bromine oxidation decreased with increasing SOC.
During the charging of a Zn/Br redox flow battery, cyclic voltammetry and electrochemical impedance spectroscopy measurements were carried out in-situ. As the state of charge (SOC) increased, some polybromide complex accumulated on the Br-side electrode surface and showed a positive effect on the adsorption of bromide ion as well as bromine. The deposition of polybromide complex onto the electrode surface was identified by SEM, EDS, and Raman spectroscopy. As a result, the charge transfer resistance for bromine oxidation decreased from 2.13 ohm to 1.27 ohm as the SOC increased from 0.0% to 80.0%. This may be due to the amphiphilic characteristics of the polybromide complex. While the solution resistance for catholyte was independent of the SOC, that for anolyte sharply decreased with increasing SOC. This could be explained by the increase in zinc ion mobility and the anolyte thickness reduction by growth of zinc metal dendrites.
Herein, we report on highly H2O-selective derivatives of UiO-66-NH2 (UiO) metal-organic frameworks (MOFs) by enhancing the hydrophilic diffusion channels via a combination of hydrophilic modification ...and defect engineering. The parent framework, hydrophilic (carboxylated or sulfonated) derivatives, a defective derivative, and a defective and carboxylated derivative were prepared to investigate their structure-transport properties. Both experiments and dynamic functional theory simulations demonstrated that the carboxylation of UiO-66-NH2 is more desirable for H2O/N2 separation than sulfonation due to the enhanced hydrophilicity and less reduced surface area. A defect was induced by an acetic acid modulator, which decreased the hydrophilicity of the parent framework due to the methyl end groups; however, it increased the surface area by 38%, possibly enhancing the diffusion channels. In addition, thin-film nanocomposite (TFN) hollow fiber membranes, derived from the incorporation of carboxylated derivatives during interfacial polymerization, exhibited striped Turing structures on their surfaces, providing more efficient water transport channels. A subsequent TFN membrane containing defective and carboxylated derivatives showed the best H2O/N2 separation performance (H2O permeance of 2370 GPU and H2O/N2 selectivity of 769), suggesting a synergistic effect of hydrophilicity and defect-induced surface area. Our current work provides useful insights into fine-tuning the structural and textural properties of both MOFs and the associated composite membranes for air dehumidification.
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•Carboxylation is more efficient for enhanced hydrophilicity of UiO-66-NH2 than sulfonation.•Acetic acid-induced defect engineering decreased hydrophilicity but enhanced H2O diffusion channels.•DFT simulations evaluated both hydrophilicity and diffusion channels of UiO-66-NH2 derivatives.•Carboxylated UiO-66-NH2 induced striped Turing structure on TFN surface, enhancing diffusion channels.•A synergistic effect of hydrophilic and defect modifications was demonstrated.
Layered silicate AMH-3 forms a 3D ordered microporous structure and is potentially useful as a permselective barrier. Nafion-based composite membrane containing delaminated AMH-3 (D-AMH-3) layer was ...prepared by solution casting and hot pressing. The membrane structure was analyzed by FE-SEM and EDS, revealing a sandwich-type structure that included double Nafion outer layers and a central D-AMH-3 layer. The Nafion/D-AMH-3 membrane was employed as an ion exchange membrane for VRB application, and the vanadium permeability and single cell performance were evaluated. The Nafion/D-AMH-3 membrane exhibited a lower VO2+ permeability compared to N117, resulting in higher Coulombic efficiency and lower capacity loss per cycle. The results indicated that D-AMH-3 layer is potentially suitable as a permselective barrier for reducing vanadium crossover and improving cell performance.
•Nafion/D-AMH-3 membrane had a sandwich structure.•D-AMH-3 layer acted as a permselective barrier to reduce vanadium crossover.•Nafion/D-AMH-3 membrane improved the Coulombic efficiency and capacity retention.
Urban networks aim at facilitating users for better experience and services through smart platforms such as the Intelligent Transportation System (ITS). ITS focuses on information acquisition, ...sensing, contrivance control, data processing and forwarding to ground devices via user-specific application-interfaces. The utility of ITS is further improved via the Internet of Things (IoT), which supports “Connectivity to All”. One of the key applications of IoT-ITS is urban surveillance. Current surveillance in IoT-ITS is performed via fixed infrastructure-based sensing applications which consume an excessive amount of energy leading to several overheads and failures in the network. Such issues can be overcome by the utilization of on-demand nodes, such as drones, etc. However, drones-assisted surveillance requires efficient communication setup as drones are battery operated and any extemporaneous maneuver during monitoring may result in loss of drone or complete failure of the network. The novelty in terms of network layout can be procured by the utilization of drones with LoRaWAN, which is the protocol designated for Low-Power Wide Area Networks (LPWAN). However, even this architectural novelty alone cannot ascertain the formation of fail-safe, highly resilient, low-overhead, and non-redundant network, which is additionally the problem considered in this paper. To resolve such problem, this paper uses drones as LoRaWAN gateway and proposes a communication strategy based on the area stress, resilient factor, and energy consumption that avail in the efficient localization, improved coverage and energy-efficient surveillance with lower overheads, lower redundancy, and almost zero-isolations. The proposed approach is numerically simulated and the results show that the proposed approach can conserve a maximum of 39.2% and a minimum of 12.6% of the total network energy along with an improvement in the area stress between 89.7% and 53.0% for varying number of drones over a fixed area.
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•Amorphous metal organic framework (MOF) was prepared by hydrothermally.•Fabrication of thin film nanocomposite membranes using NH2-MIL-125(Ti) nanoparticles.•The MOF nanoparticles ...loading increase the surface hydrophilicity and roughness.•MOF particles play very vital role for water vapor transport through the TFN membranes.
First time it is proposed that metal organic framework (MOF) incorporated thin film nanocomposite (TFN) membrane drastically enhances the water vapor transport performance from the mixture gas. The incorporation of MOF nanoparticles in a polymer matrix has afforded a new approach for the preparation of membranes with enhanced water vapor permeance, and selectivity. In this work we have synthesized the MOF material and incorporated it in monomer solution to make TFN membrane via interfacial polymerization method. Polysulfone (PSf) hollow fiber membranes have been used as substrate material for the coating of thin nanocomposite layer. The m-phenylene diamine (MPD) and trimesoyl chloride (TMC) were used as the monomer solutions for interfacial polymerization (IP) reaction. The small quantity loading of MOF particles plays a vital role for water vapor transport through the TFN membranes. Synthesized MOF material and prepared membranes were well characterized using different physicochemical analysis techniques including Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR), atomic force microscopy (AFM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and water contact angle (WCA). The water vapor permeance was increased from 785 GPU, for thin film composite (TFC) membrane, to 2244 GPU (MOF@TFN3) with the selectivity being enhanced from 116 to 542 when the NH2-MIL-125(Ti) MOF (amine-functionalized titanium metal organic framework) nanoparticles content was 0.1 w/w% with respect to monomer solution.
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