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1.
J Am Chem Soc ; 146(26): 17898-17907, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38912929

RESUMO

The interfaces of weakly hydrated mineral substrates have been shown to serve as catalytic sites for chemical reactions that may not be accessible in the gas phase or under bulk conditions. Currently known mechanisms for the formation of reactive oxygen species (ROS) from nitrogen dioxide (NO2) involve NO2 dimerization. Here, we report the formation of the ROS HONO via a mechanism involving simple adsorption of a single NO2 molecule on a weakly hydrated calcite substrate. First-principles molecular dynamics simulations coupled with enhanced sampling techniques show how an adsorbed water sublayer can enhance NO2 adsorption on calcite compared to adsorption on a bare dry substrate. On the weakly hydrated calcite surface, an interfacial electric field facilitates proton extraction from water, thus allowing HONO formation from a single adsorbed NO2, i.e., without the need for the formation of a NO2 dimer precomplex. HONO formation on calcite is kinetically more favorable than that in the gas phase, with a reaction barrier of 14 kcal/mol on the weakly hydrated calcite surface compared to 27 kcal/mol in the gas phase. Further photocatalysed HONO production by visible light and HONO dissociation are hampered on calcite, unlike the process on silica. NO2 is a significant anthropogenic pollutant, and understanding its chemistry is crucial for explaining the high ROS levels and haze formation in polluted areas or prebiotic ROS generation. These findings emphasize how mineral substrates under water-restricted hydration conditions can trigger chemical pathways that are unexpected in the gas phase or under bulk conditions.

2.
J Chem Phys ; 159(23)2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38108483

RESUMO

We report state-of-the-art first-principles molecular dynamics results on the heterogeneous chemical uptake of NO2, a major anthropogenic pollutant, on the dry and wet hydroxylated surface of α-quartz, which is a significant component of silica-based catalysts and atmospheric dust aerosols. Our investigation spotlights an unexpected chemical pathway by which NO2 (i) can be adsorbed as HONO by deprotonation of interfacial silanols (i.e., -Si-OH group) on silica, (ii) can be barrierless converted to nitric acid, and (iii) can finally dissociated to surface bounded NO and hydroxyl gas phase radicals. This chemical pathway does not invoke any previously experimentally postulated NO2 dimerization, dimerization that is less likely to occur at low NO2 concentrations. Moreover, water significantly catalyzes the HONO formation and the dissociation of nitric acid into surface-bounded NO and OH radicals, while visible light adsorption can further promote these chemical transformations. This work highlights how water-restricted solvation regimes on common mineral substrates are likely to be a source of reactive oxygen species, and it offers a theoretical framework for further and desirable experimental efforts, aiming to better constrain trace gases/mineral interactions at different relative humidity conditions.

3.
Nanotechnology ; 33(25)2022 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-35272274

RESUMO

We report on the optoelectronic characteristics ofp-NiO/n-Si heterojunction photodiode for broadband photodetection, fabricated by depositing ap-type NiO thin film onto a commercialn-type silicon substrate using pulsed laser deposition (PLD) technique. The structural properties of the PLD-grownp-NiO material were analysed by means of x-ray diffraction and x-ray photoelectron spectroscopy, confirming its crystalline nature and revealing the presence of Ni vacancies, respectively. Hall measurements confirmed thep-type semiconducting nature of the NiO thin film having a carrier concentration of 8.4 × 1016cm-3. The current-voltage (I-V) characteristics of thep-NiO/n-Si heterojunction photodevice were investigated under different wavelengths ranging from UV to NIR. The self-bias properties under different illuminations of light were also explored systematically. Under self-bias condition, the photodiode exhibits excellent responsivities of 12.5 mA W-1, 24.6 mA W-1and 30.8 mA W-1with illumination under 365 nm, 485 nm, and 850 nm light, respectively. In addition, the time dependency of the photoresponse of the fabricated photodevice has also been investigated and discussed thoroughly.

4.
Molecules ; 27(13)2022 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-35807425

RESUMO

A gold nanoparticles transparent electrode was realized by chemical reduction. This work aims to compare the transparent gold nanoparticles electrode with a more commonly utilized gold-film-coated electrode in order to investigate its potential use as counter-electrode (CE) in dye-sensitized solar cells (DSSCs). A series of DSSC devices, utilizing I-/I3- and Co(III)/(II) polypyridine redox mediators [Co(dtb)3]3+/2+; dtb = 4,4'ditert-butyl-2,2'-bipyridine)], were evaluated. The investigation focused firstly on the structural characterization of the deposited gold layers and then on the electrochemical study. The novelty of the work is the realization of a gold nanoparticles CE that reached 80% of average visible transmittance. We finally examined the performance of the transparent gold nanoparticles CE in DSSC devices. A maximum power conversion efficiency (PCE) of 4.56% was obtained with a commercial I-/I3--based electrolyte, while a maximum 3.1% of PCE was obtained with the homemade Co-based electrolyte.

5.
Phys Chem Chem Phys ; 24(1): 172-179, 2021 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-34878450

RESUMO

We present a first-principles molecular dynamics study on the uptake and hydration of sulfur dioxide on the dry and wet fully hydroxylated surfaces of (0001) α-quartz, which are a proxy for suspended silica dust in the atmosphere. The average adsorption energy for SO2 is about -10 kcal mol-1 on both dry and wet surfaces. The adsorption is driven by hydrogen bond formation between SO2 and the interfacial hydroxyl groups (on dry silica), or with water molecules (in the wet case). In the dry system, we report an additional electrostatic interaction between the interfacial hydroxyl oxygen and the sulfur atom, which further stabilizes the adsorbate. On dry silica, the interfacial hydroxyl group coordinates to SO2 yielding a surface bound bisulfite (Si-SO3H) complex. On the wet surface, SO2 reacts with water forming bisulfite (HSO3-), and the latter remains solvated inside the adsorbed water layer. The hydration barrier for sulfur dioxide is 1 kcal mol-1 and 3 kcal mol-1 on dry and wet silica, respectively, while for the backward reaction (i.e., bisulfite to SO2) the barrier is 6 kcal mol-1 on both surfaces. The modest backward barrier rationalizes earlier experimental findings showing no SO2 uptake on silica. These results underline the importance of the surface hydroxylation and/or adsorbed water layers for the SO2 uptake and its hydration on silica. Moreover, the hydration to bisulfite may prevent direct SO2 photochemistry and be an additional source of sulfate; this is especially relevant in atmospheres subject to a high level of suspended mineral dust, intense solar radiation and atmospheric oxidizers.

6.
Inorg Chem ; 56(16): 9903-9912, 2017 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-28763219

RESUMO

A series of six homoleptic bis-cyclometalated ruthenium complexes, Ru(N^N^C)2, is reported where N^N^C is a 6-(2,4-difluoro-3-R3-phenyl)-4-R2-4'-R1-2,2'-bipyridine with R3 = -H or -CF3 and R2 and R1 = -COOEt or -CF3. An effective synthesis of the ligands and the complexes is described. The UV-visible absorption studies demonstrate that these complexes are panchromatic dyes absorbing up to 900 nm. Importantly, the onset of absorption depends only on the substitution on the metalated phenyl, whereas the intensity of absorption throughout the spectra is a function of substituents on both the phenyl and the bipyridine moieties. The same trend is observed in electrochemistry as the redox gap depends only on the substitution on the metalated phenyl, whereas the oxidation and reduction potentials are a function of substituents on both the phenyl and the bipyridine moieties. Preliminary tests as sensitizer for dye-sensitized solar cells demonstrate that the number of anchoring groups on the dye has a major influence on the device efficiency.

7.
Chembiochem ; 17(16): 1541-9, 2016 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-27252026

RESUMO

The inhibition of amyloid formation is a promising therapeutic approach for the treatment of neurodegenerative diseases. Peptide-based inhibitors, which have been widely investigated, are generally derived from original amyloid sequences. Most interestingly, trehalose, a nonreducing disaccharide of α-glucose, is effective in preventing the aggregation of numerous proteins. We have determined that the development of hybrid compounds could provide new molecules with improved properties that might synergically increase the potency of their single moieties. In this work, the ability of Ac-LPFFD-Th, a C-terminally trehalose-conjugated derivative, to slow down the Aß aggregation process was investigated by means of different biophysical techniques, including thioflavin T fluorescence, dynamic light scattering, ESI-MS, and NMR spectroscopy. Moreover, we demonstrate that Ac-LPFFD-Th modifies the aggregation features of Aß and protects neurons from Aß oligomers' toxic insult.


Assuntos
Peptídeos beta-Amiloides/antagonistas & inibidores , Peptidomiméticos/farmacologia , Trealose/farmacologia , Peptídeos beta-Amiloides/química , Animais , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Estrutura Molecular , Neurônios/citologia , Neurônios/efeitos dos fármacos , Peptidomiméticos/química , Ratos , Trealose/química
8.
J Mol Recognit ; 28(8): 480-91, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25763559

RESUMO

The present work introduces a surface plasmon resonance-based method for the discrimination of direct competition and allosteric effects that occur in ternary systems comprising a receptor protein and two small-molecular-weight ligands that bind to it. Fatty acid binding protein 4, fructose-1,6-bisphosphatase and human serum albumin were used as model receptor molecules to demonstrate the performance of the method. For each of the receptor molecules, pairs of ligand molecules were selected for which either direct competition or an allosteric effect had already been determined by other methods. The method of discrimination introduced here is based on the surface plasmon resonance responses observed at equilibrium when an immobilized receptor protein is brought into contact with binary mixtures of interacting ligands. These experimentally determined responses are compared with the responses calculated using a theoretical model that considers both direct competition and allosteric ligand interaction modes. This study demonstrates that the allosteric ternary complex model, which enables calculation of the fractional occupancy of the protein by each ligand in such ternary systems, is well suited for the theoretical calculation of these types of responses. For all of the ternary systems considered in this work, the experimental and calculated responses in the chosen concentration ratio range were identical within a five-σ confidence interval when the calculations considered the correct interaction mode of the ligands (direct competition or different types of allosteric regulation), and in case of allosteric modulation, also the correct strength of this effect. This study also demonstrates that the allosteric ternary complex model-based calculations are well suited to predict the ideal concentration ratio range or even single concentration ratios that can serve as hot spots for discrimination, and such hot spots can drastically reduce the numbers of measurements needed for discrimination between direct competition and distinct modulation modes (neutral, positive or negative allostery).


Assuntos
Ligantes , Ressonância de Plasmônio de Superfície/métodos , Albuminas/química , Regulação Alostérica , Sítios de Ligação , Proteínas de Ligação a Ácido Graxo/química , Frutose-Bifosfatase/química , Humanos , Modelos Moleculares , Ligação Proteica
9.
Chemistry ; 20(27): 8467-76, 2014 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-24889966

RESUMO

We report the unprecedented observation and unequivocal crystallographic characterization of the meta-stable ligand loss intermediate solvento complex trans-[Ru(bpy)(κ(2) -btz)(κ(1) -btz)(NCMe)](2+) (1 a) that contains a monodentate chelate ligand. This and analogous complexes can be observed during the photolysis reactions of a family of complexes of the form [Ru({NN})(btz)(2)](2+) (1 a-d: btz=1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl; {NN}=a) 2,2'-bipyridyl (bpy), b) 4,4'-dimethyl-2,2'-bipyridyl (dmbpy), c) 4,4'-dimethoxy-2,2'-bipyridyl (dmeobpy), d) 1,10-phenanthroline (phen)). In acetonitrile solutions, 1 a-d eventually convert to the bis-solvento complexes trans-[Ru({NN})(btz)(NCMe)(2)](2+) (3 a-d) along with one equivalent of free btz, in a process in which the remaining coordinated bidentate ligands undergo a new rearrangement such that they become coplanar. X-ray crystal structure of 3 a and 3 d confirmed the co-planar arrangement of the {NN} and btz ligands and the trans coordination of two solvent molecules. These conversions proceed via the observed intermediate complexes 2 a-d, which are formed quantitatively from 1 a-d in a matter of minutes and to which they slowly revert back on being left to stand in the dark over several days. The remarkably long lifetime of the intermediate complexes (>12 h at 40 °C) allowed the isolation of 2 a in the solid state, and the complex to be crystallographically characterized. Similarly to the structures adopted by complexes 3 a and d, the bpy and κ(2) -btz ligands in 2 a coordinate in a square-planar fashion with the second monodentate btz ligand coordinated trans to an acetonitrile ligand.

10.
Photochem Photobiol Sci ; 13(5): 735-8, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24676362

RESUMO

Complexes of the form [Ru(diimine)2(btz)](2+) (btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl) are observed to undergo photochemical ejection of the btz ligand in the absence of any promotion through steric congestion to generate cis-bis(solvent) complexes [Ru(diimine)2(solvent)2](2+).


Assuntos
Compostos Organometálicos/química , Rutênio/química , Ligantes , Estrutura Molecular , Processos Fotoquímicos
11.
ACS Omega ; 9(1): 771-780, 2024 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-38222595

RESUMO

Hydration of carbon dioxide in water solution is the rate limiting step for the CO2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

12.
RSC Adv ; 14(7): 4788-4803, 2024 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-38318606

RESUMO

Dry reforming of methane (DRM) has recently received wide attention owing to its outstanding performance in the reduction and conversion of CH4 and CO2 to syngas (H2 and CO). From an industrial perspective, nickel (Ni)-supported catalysts have been deemed among the most suitable catalysts for DRM owing to their low cost and high activity compared to noble metals. However, a downside of nickel catalysts is their high susceptibility to deactivation due to coke formation and sintering at high temperatures. Using appropriate supports and preparation methods plays a major role in improving the activity and stability of Ni-supported catalysts. Halloysite nanotubes (HNTs) are largely utilized in catalysis as a support for Ni owing to their abundance, low cost, and ease of preparation. The treatment of HNTs (chemical or physical) prior to doping with Ni is considered a suitable method for increasing the overall performance of the catalyst. In this study, the surface of HNTs was activated with acids (HNO3 and H2SO4) and alkalis (NaOH and Na2CO3 + NaNO3) prior to Ni doping to assess the effects of support treatment on the stability, activity, and longevity of the catalyst. Nickel catalysts on raw HNT, acid-treated HNT, and alkali-treated HNT supports were prepared via wet impregnation. A detailed characterization of the catalysts was conducted using X-ray diffraction (XRD), BET surface area analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (ssNMR), H2-temperature programmed reduction, (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), and Ni-dispersion via H2-pulse chemisorption. Our results reveal a clear alteration in the structure of HNTs after treatment, while elemental mapping shows a uniform distribution of Ni throughout all the different supports. Moreover, the supports treated with a molten salt method resulted in the overall highest CO2 and CH4 conversion among the studied catalysts and exhibited high stability over 24 hours testing.

13.
Photochem Photobiol Sci ; 12(5): 883-94, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23467482

RESUMO

Seven flavylium salt dyes were employed for the first time as sensitizers for dye-sensitized solar cells (DSSCs). The theoretical and experimental wavelengths of the maximum absorbances, the HOMO and LUMO energy levels, the coefficients, the oscillator strengths and the dipole moments are calculated for these synthetic dyes. The introduction of a donor group in the flavylium molecular structure was investigated. Photophysical and photoelectrochemical measurements showed that some of these synthetic analogues of anthocyanins are very promising for DSSC applications. The best performance was obtained by a DSSC based on the novel compound 7-(N,N-diethylamino)-3',4'-dihydroxyflavylium which produced a 2.15% solar energy-to-electricity conversion efficiency, under AM 1.5 irradiation (100 mW cm(-2)) with a short-circuit current density (J(sc)) of 12.0 mA cm(-2), a fill factor of 0.5 and an open-circuit voltage (V(oc)) of 0.355 V; its incident photocurrent efficiency of 51% at the peak of the visible absorption band of the dye is remarkable. Our results demonstrated that the substitution of a hydroxylic group with a diethylamine unit in position 7 of ring A of the flavylium backbone expanded the π-conjugation in the dye and thus resulted in a higher absorption in the visible region and is advantageous for effective electron injection from the dye into the conduction band of TiO2.

14.
J Exp Med ; 220(12)2023 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-37773046

RESUMO

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE), or chimeric antigen receptor (CAR) cells is very effective for hematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various hematological malignancies, including acute myeloid leukemia (AML). However, shared CD123 expression on healthy hematopoietic stem and progenitor cells (HSPCs) bears the risk for myelotoxicity. We demonstrate that epitope-engineered HSPCs were shielded from CD123-targeted immunotherapy but remained functional, while CD123-deficient HSPCs displayed a competitive disadvantage. Transplantation of genome-edited HSPCs could enable tumor-selective targeted immunotherapy while rebuilding a fully functional hematopoietic system. We envision that this approach is broadly applicable to other targets and cells, could render hitherto undruggable targets accessible to immunotherapy, and will allow continued posttransplant therapy, for instance, to treat minimal residual disease (MRD).


Assuntos
Subunidade alfa de Receptor de Interleucina-3 , Leucemia Mieloide Aguda , Humanos , Subunidade alfa de Receptor de Interleucina-3/metabolismo , Epitopos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/terapia , Imunoterapia , Células-Tronco Hematopoéticas/metabolismo , Imunoterapia Adotiva
16.
J Phys Chem B ; 125(18): 4890-4897, 2021 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-33885318

RESUMO

The need to chemically convert CO2 at the interface of aqueous amine solutions has become particularly relevant for the development and the broad distribution of cost-effective and near-future devices for direct air capture working at low (e.g., ambient) partial pressure. Here, we have determined the stability of a CO2-monoethanolamine zwitterion and its chemical conversion into carbamate at the vapor/liquid water interface by first-principles molecular dynamics simulations coupled with a recently introduced enhanced sampling technique. Contrary to the bulk water case, our results show that both the zwitterion and carbamate ions are poorly stable at the vapor/amine aqueous interface, further stating the differences between the homogeneous and heterogeneous CO2 chemical conversion. The design of novel and cost-effective capture systems, such as those offered by amine-based scrubbing solutions, working at low (e.g., ambient) CO2 partial pressure should explore the use of novel solvents, different from aqueous mixtures, to overcome the limits of the current absorbents.

17.
ACS Omega ; 6(49): 33325-33338, 2021 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-34926884

RESUMO

Due to their broad applications in various industrial activities, and their well-known negative impacts on the aquatic environment, organic dyes have been continuously identified as serious threat to the quality of ecosystems. The photocatalytic degradation process in aqueous solutions has emerged as an efficient and reliable approach for the removal of organic dyes. MXenes, a new class of two-dimensional (2D) nanomaterials, possess unique chemical composition, surface functionalities, and physicochemical properties. Such characteristics enable MXenes to act as efficient catalysts or cocatalysts to photodegrade organic molecules. This work explores the application of Ti3C2T x MXene decorated with silver and palladium nanoparticles, using a simple hydrothermal treatment method, for the photocatalytic degradation of methylene blue (MB) and rhodamine B (RhB). The chemical composition of these photocatalysts, as well as their structural properties and morphology, was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The photocatalytic degradation abilities of the pristine MXene and the synthesized MXene composites were investigated under ultraviolet and solar light irradiation. A significant improvement in the photocatalytic performances was observed for all oxidized MXene composites when compared to pristine MXene, with a superior degradation efficiency achieved for AgNPs/TiO2/Ti3C2T x . This work broadens the application range of oxidized MXene composites, providing an alternative material for degrading organics dyes and wastewater treatment applications.

18.
Materials (Basel) ; 14(12)2021 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-34204769

RESUMO

Introducing redox-active moieties into an ionic liquid (IL) structure is an exciting and attractive approach that has received increasing interest over recent years for a various range of energy applications. The so-called redox-active ionic liquids (RAILs) provide a highly versatile platform to potentially create multifunctional electroactive materials. Ionic liquids are molten salts consisting of ionic species, often having a melting point lower than 100 °C. Such liquids are obtained by combining a bulky asymmetric organic cation and a small anion. Here, we report on the synthesis of a novel RAIL, namely 1-butyl-3-methylimidazolium hydroquinone sulfonate ((BMIM)(HQS)). (BMIM)(HQS) was synthesized in a two-step procedure, starting by the quaternization of methylimidazole using butylchloride to produce 1-butyl-3-methylimidazolium chloride ((BMIM)(Cl)), and followed by the anion exchange reaction, where the chloride anion is exchanged with hydroquinone sulfonate. The resulting product was characterized by 1H NMR, 13C NMR, FT-IR spectroscopy, themogravimetric analysis, and differential scanning calorimetry, and shows a high stability up to 340 °C. Its electrochemical behavior was investigated using cyclic voltammetry at different temperatures and its viscosity analysis was also performed at variable temperatures. The electrochemical response of the presented RAIL was found to be temperature dependent and diffusion controlled. Overall, our results demonstrated that (BMIM)(mix of HQS and HSQ) is redox active and possesses high stability and low volatility, leading to the employment of this RAIL without any additional supporting electrolyte or additives.

19.
ACS Appl Mater Interfaces ; 13(38): 45935-45943, 2021 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-34533936

RESUMO

The deployment of alkaline anion exchange membranes (AEMs) in flow battery applications has the advantage of a low cationic species crossover rate. However, the alkaline stability conjugated to the low conductivity of hydroxide ions of anion exchange membranes (AEMs) still represents a major drawback for the large deployment of such technology. In this study, three types of tetraarylpolyphosphonium (pTAP)-based copolymers (namely, CP1, CP2, and CP3) are synthesized and blended with chitosan and polyvinylidene fluoride (PVDF) for the fabrication of AEMs. Chitosan, a green biopolymer, was employed as a blend to enhance the water uptake of the base ionomer matrix. It is proposed that the abundancy of hydroxyl groups in chitosan improves considerably the ionic conductivity, water transport, and ion selectivity of the membrane, together with facilitating the dispersion of the chitosan in the pTAP copolymer matrix. The purpose of blending PVDF is instead to provide stable mechanical strength to the composite blend. The chemical, mechanical, and thermal stabilities of the three fabricated composite-blend membranes (i.e., CM1, CM2, and CM3) were characterized. All the membranes exhibited a high water retaining capacity of up to 36.26% (recorded for CM2) along with a hydroxyl ion conductivity of 17.39 mS cm-1. Due to the strong interactions between pTAP copolymers, chitosan, and PVDF polymers (confirmed also by Fourier transform infrared spectroscopy), the studied anion exchange membranes are able to retain up to 97% of the original OH conductivity after 1 M KOH treatment at room temperature for 100 h. The three membranes, namely, CM1, CM2, and CM3, have vanadium ion permeabilities measured at 20 °C of 1.775 × 10-8, 1.718 × 10-8, and 1.648 × 10-8 cm2/s, respectively, which are lower than that for the commercially available Nafion. The good stability and remarkable cell performance of the composite-blend membranes reported here make them definitely excellent candidates for the future generation of vanadium redox flow batteries.

20.
Sci Rep ; 11(1): 13841, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34226644

RESUMO

Anion exchange membranes (AEMs) are becoming increasingly common in electrochemical energy conversion and storage systems around the world (EES). Proton-/cation-exchange membranes (which conduct positive charged ions such as H+ or Na+) have historically been used in many devices such as fuel cells, electrolysers, and redox flow batteries. High capital costs and the use of noble metal catalysts are two of the current major disadvantages of polymer electrolyte membrane (PEM)-based systems. AEMs may be able to overcome the limitations of conventional PEMs. As a result, polymers with anion exchange properties have recently attracted a lot of attention due to their significant benefits in terms of transitioning from a highly acidic to an alkaline environment, high kinetics for oxygen reduction and fuel oxidation in an alkaline environment, and lower cost due to the use of non-precious metals. The aim of this research was to learn more about the development of a new AEM based on poly tetraarylphosphonium ionomers (pTAP), which has high ionic conductivity, alkaline stability, thermal stability, and good mechanical properties, making it a more cost-effective and stable alternative to conventional and commercial AEMs. A simple solution casting method was used to build novel anion exchange composite membranes with controlled thicknesses using the synthesized pTAP with polysulfone (PS). To ensure their suitability for use as an electrolyte in alkaline electrochemical systems, the composite membranes were characterized using FTIR, XRD, water uptake, ionic conductivity, and alkaline stability. At 40 °C, the PS/pTAP 40/60 percent membrane had a maximum ionic conductivity of 4.2 mS/cm. The thermal and mechanical stability of the composite membranes were also examined, with no substantial weight loss observed up to 150 °C. These findings pave the way for these membranes to be used in a wide variety of electrochemical applications.

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