Ion-selective Polymer Research Articles

Development of an Intranasal In Situ System for Ribavirin Delivery: In Vitro and In Vivo Evaluation.

Recently, ribavirin has demonstrated effectiveness in treating glioblastoma through intranasal administration utilizing the nose-to-brain delivery route. Enhancing ribavirin's bioavailability can be achieved by utilizing intranasal stimuli-responsive systems that create a gel on the nasal mucosa. The research examined thermosensitive, pH-sensitive, and ion-selective polymers in various combinations and concentrations, chosen in line with the current Quality by Design (QbD) approach in pharmaceutical development. Following a thorough assessment of key parameters, the optimal composition of gellan gum at 0.5%, Poloxamer 124 at 2%, and purified water with ribavirin concentration at 100 mg/mL was formulated and subjected to in vivo testing. Through experiments on male rats, the nose-to-brain penetration mechanism of the active pharmaceutical ingredient (API) was elucidated, showcasing drug accumulation in the olfactory bulbs and brain.

(Invited) Towards Rechargeable Zn/CuO Batteries for Grid-Scale Storage

Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with a Zn anode in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized 10% of a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Optimization studies performed for Bismuth content indicate that changes in Bi2O3 concentration can impact the charge-discharge behavior of the CuO cathodes resulting in the suppression of metal hydroxide-related redox peaks on charge. The absence of these peaks correlates with improved cyclability, suggesting that methods and materials approaches to further suppress these recharge pathways may lead to CuO high-capacity cathodes with improved cycle-life in the future.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can also affect the battery cycling mechanism and may have future roles of increasing performance.Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, polymer gel electrolytes and ion selective polymers in enabling reversible Cu-based cathodes. The general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be covered as will development towards a > 200 Wh/L industrially relevant Zn/CuO battery.This work was supported by the U.S. Department of Energy Office of Electricity. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. The views expressed in this article do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This article has been co-authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in their contribution to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

Moisture-driven energy generation by vertically structured polymer aerogel on water-collecting gel

In the realm of energy harvesting, free-standing, film-type, moisture-driven electricity generators (MEGs) based on polymer hydrogels with moisture-retaining capability are promising as a convenient and practical power source, making them potentially suitable for various self-powered, wearable, and patchable electronic devices. Their performance is, however, substantially degraded under low-humidity (<40%) conditions owing to the limited water supply to the device. This study presents a high-performance film-type MEG that functions at a low humidity of 20%. The MEG is based on an ion-selective polymer aerogel as an electricity-generating layer, constructed on a water-collecting gel as a water reservoir. The water-collecting gel in the bi-layered MEG absorbs moisture even under low-humidity conditions and efficiently delivers moisture to the electricity-generating aerogel layer. The energy-harvesting ability of the electricity-generating aerogel layer is further facilitated by its characteristic vertical microstructure, which comprises aerogel pores directionally grown on the frozen water-collecting gel during the freeze-drying process. The low humidity-tolerant MEG generated a stable open-circuit voltage of 1.1 V for more than 500 min even under dry conditions (20% relative humidity). Various self-powered electronic applications are demonstrated with the low-humidity-tolerant, bi-layered MEGs in dry environments. This study provides new insights for designing future MEGs for operation in low-humidity environments, further facilitating the development of green and sustainable power generation.

Towards Energy Dense Rechargeable Batteries Utilizing Zn and Cu

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.1 However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with Zn in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Alternatively, compensating for capacity loss with additional Cu metal provided for very high areal capacities (∼40 mA h/cm2) and energy densities (∼260 W h/L), despite only 65% active material cathode loadings and ∼10% Zn anode utilization; however, preliminary tests indicated these batteries were prone to shorting.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where ~ 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can affect the battery cycling mechanism and may have future roles increasing performance.Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, and ion selective polymers in enabling reversible Zn/Cu based batteries. In addition, the general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be discussed.A near-term goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While the laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.N. Schorr et al. ACS Applied Energy Mater. 2021, 4, 7, 7073–7082. https://doi.org/10.1021/acsaem.1c01133.D. J. Arnot et al. J. Power Sources 2022, 529, 231168. https://doi.org/10.1016/j.jpowsour.2022.231168.

Progress Towards the Development and Understanding of Energy Dense Rechargeable Batteries Utilizing Zn and Cu

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with Zn in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Alternatively, compensating for capacity loss with additional Cu metal provided for very high areal capacities (∼40 mA h/cm2) and energy densities (∼260 W h/L), despite only 65% active material cathode loadings and ∼10% Zn anode utilization; preliminary tests indicated these batteries were prone to shorting.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where ~ 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can affect the battery cycling mechanism and may have future roles increasing performance. Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, and ion selective polymers in enabling reversible Zn/Cu based batteries. In addition, the general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be discussed.The goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While the laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.N. B. Schorr et al. Rechargeable Alkaline Zinc/Copper Oxide Batteries. ACS Applied Energy Mater. 2021, 4, 7, 7073–7082. https://doi.org/10.1021/acsaem.1c01133.D. J. Arnot et al. Rechargeable Alkaline Zn-Cu Batteries Enabled by Carbon Coated Cu/Bi Particles. J. Power Sources 2022, 529, 231168. https://doi.org/10.1016/j.jpowsour.2022.231168.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Sulfonated polymer coating enhances selective removal of calcium in membrane capacitive deionization

There is a need for membranes and processes that can selectively separate target ions from other similar ionic species. Recent studies have shown that electrified processes for ion removal such as membrane capacitive deionization (MCDI) and electrodialysis (ED) are selective towards specific ionic species, but selectivities are generally limited. Here, we demonstrate that an ion-selective polymer coating can significantly enhance ion selectivities for MCDI processes. We focused on the preferential removal of Ca2+ over Na+ and used the conductive and sulfonated polymer poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a model selective ion-exchange coating. We first measured the permeability of Ca2+ and Na+ in freestanding PEDOT:PSS membranes of varying crosslink density and found that the permeability of Ca2+ was six times greater than that for Na+ in optimized membranes. Next, we used PEDOT:PSS in an MCDI process by depositing thin PEDOT:PSS coatings on top of composite electrodes. We found that the PEDOT:PSS coatings significantly enhanced the preferential permeability of Ca2+ over Na + relative to unmodified electrodes and produced a preferential removal as high as 8:1 on a molar basis. This work demonstrates a new approach to enhance selective ion removal in MCDI and other electro-driven ion separation processes.

High-Performance Alkaline Water Electrolysis Using Anion-Exchange Membrane-Electrode Assembly with Catalyst Coated Membrane and Platinum Free Catalysts

Possibility of operation a water electrolysis technology using cost-effective components for current collectors or porous transport layers and non-platinum group metal catalysts with fast response to intermittent loads from renewable energy sources makes membrane alkaline water electrolysis (MAWE) an attractive technology for producing low cost “green” hydrogen. MAWE represents a technology combining the advantages of the already established electrolyser technologies, i.e. proton exchange membrane water electrolysis (PEMWE) and alkaline water electrolysis (AWE). It combines the relatively low-cost materials of AWE with utilisation of the ion-selective polymer electrolyte as separator of the electrode compartments which is commonly used in PEMWE. In the case of the utilisation of the ion-selective polymer electrolyte the electrodes can be pressed directly to its surface thus creating the membrane-electrode assembly (MEA). Reduction of the gap between the electrodes and separator to zero lowers the ohmic drop on the cell. This positively affects the efficiency of the water electrolysis. In MAWE the anion-selective materials are still facing some limitations in terms of poorer chemical stability in high pH environments and at elevated temperatures due to degradation of the anion exchange groups either by Hoffman elimination or nucleophilic attack by OH- ions, or lower ionic conductivity.Primarily two different MEA fabrication methods are recognized in literature [1]: catalyst-coated substrate (CCS) and catalyst-coated membrane (CCM). In the CCS method, catalyst ink, consisting of a binder/ionomer, catalyst particles and solvent, is applied to one side of the porous transport layer whereas in CCM method the catalyst ink is applied to the ion-selective membrane. The CCM approach is established in the PEMWE technology, but in MAWE the above-mentioned problem with stability of anion-selective materials limits the research.From PEMWE we know that CCM approach provides several advantages, including close contact between the catalyst layer and membrane resulting in better utilization of the catalyst compared to CCS. This advantage allows the MEA to maintain the overall performance with lower catalyst loading. Also, the catalyst layer thickness is reduced, which lowers ohmic losses on the MEA. However, the CCM method can also cause poor electrical contact between the MEA and current collector or within the catalyst layer itself.In this work, we first compare the CCS and CCM approaches and study the possibility of catalyst loading reduction. Then, with CCM we further optimize the composition of the catalyst layer, study the effect of method of preparation and compare two different membranes – non-commercial with 2 different thicknesses and commercial oneAs anion-selective material we use chloromethylated block copolymer polystyrene-ethylene-butylene-styrene (PSEBS-CM) functionalized with 1,4-diazabicyclo[2.2.2]octane (DABCO) groups. The solution of PSEBS-CM is used also as a binder of the catalyst layer. This material showed good ionic conductivity, ion exchange capacity and stability at elevated temperature. For comparison reason, Fumapem® FAA-3-50 membrane is tested. NiCo2O4 and NiFe2O4 are used as anode and cathode catalysts, respectively. Air-brush or computer controlled ultrasonic dispersion of catalyst ink are used to prepare MEA. As many operating conditions have been reported to significantly affect MAWE performance, including membrane thickness, electrolyte type, and operating temperature we decided to test the performance of the prepared CCSs and CCMs by mean of the load curves in in the range 1.5 – 2.0 V in different concentrations of KOH (1 – 15 wt.%) at 50 °C. To identify the influence of membrane thickness, we use membrane with thickness of 250 or 60 µm. To have deeper insight on the system, electrochemical impedance spectroscopy is used under the MAWE conditions at voltage of 0, 1.5 and 1.8 V in frequency range 100 kHz – 0.1 Hz with amplitude of 10 mV. Scanning electron microscopy is used to observe the morphology of the layers. The chosen CCMs undergo the stability test measured at 50 °C in 10 wt.% KOH at current density of 250 mA cm-2 for 160 hours.The obtained results show the possibility of: 1) replacing the CCS with CCM, 2) reduction of the catalyst load by 75%, 3) improvement of performance with optimized catalyst/binder ratio and 4) improvement of performance with reduction of the membranes thickness.Acknowledgments:This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 875118. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe research. Financial support by the Technology agency of the Czech Republic within the framework of the project No. TK 02030001 is gratefully acknowledged. Huah, L.B., et al., Chinese Journal of Chemical Engineering, 2020.

Recycling the cathode materials of spent Li-ion batteries in a H-Shaped neutral water electrolysis cell

• A large pH gradient is generated in a neutral water electrolysis cell. • The pH gradient allows concurrent LiCoO 2 leaching and Co(OH) 2 precipitation. • The use of external acid and base is avoided. • The Co(OH) 2 and Li 2 CO 3 recovered were calcined to resynthesize new LiCoO 2 . • The treatment of LiMn 2 O 4 and NCM with this process was also investigated. The recycling of Li-ion batteries is becoming increasingly urgent due to the rapid accumulation of spent Li-ion batteries from aging portable electronics and electric vehicles. The lack of environmentally and economically feasible recycling technologies will not only cause material losses and environmental contamination, but also poses a serious limit for the penetration of more Li-ion batteries in electric vehicles and grid-scale energy storage applications. Here, we present a proof-of-concept demonstration of an innovative process for recycling cathode materials of Li-ion batteries in a neutral water electrolysis cell. During electrolysis, an electrochemical pH gradient was generated, which enables the leaching of waste LiCoO 2 at low pH in the anode chamber and the precipitation of solid Co(OH) 2 at high pH in the cathode chamber. The Co(OH) 2 precipitates can be readily filtered and separated from the electrolysis cell. In addition, the Li + is recovered in the form of Li 2 CO 3 . Unlike conventional hydrometallurgical processes and other aqueous electrochemical processes, this work harnesses the in-situ electrochemical pH gradient generated by neutral water electrolysis. This allows concurrent LiCoO 2 leaching and Co(OH) 2 precipitation at separate chambers and avoids the use of external acid and base, extractant or ion-selective polymer electrolyte membrane. This method is also extended to recycling waste LiMn 2 O 4 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 . Therefore, this new process represents a green advance for recycling the waste cathode materials of the Li-ion batteries.

Single-ion conducting polymer electrolytes as a key jigsaw piece for next-generation battery applications.

As lithium-ion batteries have been the state-of-the-art electrochemical energy storage technology, the overwhelming demand for energy storage on a larger scale has triggered the development of next-generation battery technologies possessing high energy density, longer cycle lives, and enhanced safety. However, commercial liquid electrolytes have been plagued by safety issues due to their flammability and instability in contact with electrodes. Efforts have focused on developing such electrolytes by covalently immobilizing anionic groups onto a polymer backbone, which only allows Li+ cations to be mobile through the polymer matrix. Such ion-selective polymers provide many advantages over binary ionic conductors in battery operation, such as minimization of cell polarization and dendrite growth. In this review, the design, synthesis, fabrication, and class are reviewed to give insight into the physicochemical properties of single-ion conducting polymer electrolytes. The standard characterization method and remarkable electrochemical properties are further highlighted, and perspectives on current challenges and future directions are also discussed.

Porous polybenzimidazole membranes with high ion selectivity for the vanadium redox flow battery

Development of high ion-selective polymer membranes is of great importance for vanadium redox flow batteries (VRFBs). In this work, porous polybenzimidazole (PBI) membranes are successfully prepared for improved efficiencies and stability in VRFB applications. The porous structure is constructed via a hard templating method using monodispersed SiO2 solid spheres and 3 M NaOH as template and etching solution, respectively. The influence of the adding content of SiO2 on the microstructure of the membrane is illustrated. The properties of porous membranes, including acid doping, swellings, area resistance, mechanical properties, vanadium ion permeation, and single cell and cycling performance, are investigated systematically. Results show that asymmetric porous PBI membranes exhibit increased sulfuric acid (SA) uptake (>35 wt%), remarkably low area resistance (<0.58 Ω cm2), ultralow vanadium ion permeability (<10-9 cm2 min-1) and superior mechanical strength (>20 MPa) simultaneously. At high current densities (80–200 mA cm-2), the cell with the porous PBI-40%SiO2 membrane possesses superior coulombic efficiencies (CE: 99.5–100%) and energy efficiencies (EE: 87.9–71.5%), together with excellent cycling stability at 120 mA cm-2 in the vanadium flow battery. Accordingly, this work not only provides a kind of advanced membranes for the VRFB, but also offers a facile and effective method to design, optimize and fabricate membranes incorporating the features according to needs.

Sulfonated Microporous Polymer Membranes with Fast and Selective Ion Transport for Electrochemical Energy Conversion and Storage

Membranes with fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton-exchange membrane (PEM) fuel cells and redox flow batteries. Here we report a new approach to designing solution-processable ion-selective polymer membranes with both intrinsic microporosity and ion-conductive functionality. This was achieved by synthesizing polymers with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively-charged subnanometer-sized confined ionic channels. The facilitated transport of protons and cations through these membranes, as well as high selectivity towards nanometer-sized redox-active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell. This membrane design strategy paves the way for producing a new-generation of ion-exchange membranes for electrochemical energy conversion and storage applications.

Selective metal ion transport through polymer inclusion membrane containing surfactin as carrier reagents

AbstractMetal ion selective polymer inclusion membrane (PIM) was prepared by using cellulose triacetate as matrix, surfactin (SF) as ion carrier, and 2‐nitrophenyl n‐octyl ether as plasticizer. The structure and morphology of the prepared PIM were characterized by means of thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The effects of plasticizer and the amount of SF to ionic membrane flux were investigated, and the optimized component was obtained thereof. The selectivity of the membrane toward metal cation was studied and the order of Ni(II) &gt; Ca(II) &gt; Co(II) &gt; Pb(II) &gt; Cu(II) &gt; Mg(II) was followed. In addition, the durability of the PIM was studied by successive reuse of the membrane, and the ionic flux slightly decreased after five cycles of reuse, indicating the excellent durability of the PIM.

Ion-selective Polymer Electrolyte Membrane Based on Sulfonated Silica and Sulfonated Poly(Phenylene Oxide) for Redox Flow Battery

Polymer electrolyte membrane (PEM) based on sulfonated poly (phenylene oxide) (sPPO) and sulfonated silica (sSiO2) is synthesized for the application of redox flow battery (RFB). Synthesis of PEM based on sPPO and sSiO2 is confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Proton conductivity (0.077 S cm-1) of PEM based on sPPO and sSiO2 is comparable to Nafion (0.078 S cm-1). This is due to the incorporation of sSiO2 having –SO3H functional group. Increased –SO3H functional groups in sPPO and sSiO2 can increase the ion exchange capacity (IEC) of the membrane. It can lead to high proton conductivity because of the well-organized cluster network structure. In addition, sSiO2 can play a role of barrier for the suppression of vanadium cross-over through the membrane. Therefore, the permeability of PEM (4.76 x 10-9 cm2 min-1) based on sPPO and sSiO2 is much lower than that of Nafion membrane (2.22 x 10-7cm2 min-1). It means that the selectivity of PEM based on sPPO and sSiO2 is much better than that of Nafion membrane. As a result of our study, it is found that our ion-selective PEM based on sPPO and sSiO2 can be a promising candidate for energy device and water treatment system.

(Invited) Mechanistic Details of Protonic Solar Cells Formed Via Covalent Modification of Passive Ion-Exchange Membranes with Photoacid Dye Molecules

Many electrochemical technologies require ion-conducting polymer electrolytes. These polymers are passive in that electric bias across them drives ion migration in the thermodynamically favored direction.1 Recently, my group engineered two important features into ion-selective polymer membranes to introduce the active function of photovoltaic action and demonstration of an ionic solar cell. These features were covalent bonding of photoacid dyes to the polymers such that absorption of visible light liberated protons, and polymers with charge-selective contacts to facilitate separation and collection of H+ and OH–.2,3 The most effective designs join a monopolar cation-selective polymer to a monopolar anion-selective polymer to form a bipolar membrane whose electrostatics and thermodynamics mimic those of a rectifying semiconductor pn-junction diode. Illumination from either side of a photoacid-modified bipolar membrane resulted in photoinduced deprotonation of photoacids followed by charge separation in a direction dictated by the built-in electrostatic asymmetry in the polymers. Performance optimization is underway to increase the state-of-the-art voltage to beyond 120 mV and state-of-the-art current to beyond 100 μA/cm2. The aim of these efforts is to gain a strong fundamental understanding of dye and material function using a variety of techniques. These include electrochemical impedance spectroscopy to quantify properties of capacitive space-charge regions; pulsed-laser spectroscopy to elucidate light-driven mechanisms of ion transfer and transport; finite-element numerical modeling to understand photoacid dye kinetics and drift–diffusion generation–recombination membrane physics; and optical, electron, and ion microscopies to elucidate materials morphology and function. Collectively, these photo-responsive polymers represent a new class of materials that use light to trigger changes in local pH and/or electrostatic potential. These local changes can be used to affect macroscopic processes such as direct solar desalination of salt water or triggering redox chemistry or chemical catalysis. Acknowledgment: This work is supported by a Moore Inventor Fellowship from the Gordon & Betty Moore Foundation, under Grant #5641.

Synergetic Effects of Multifunctional Composites with More Efficient Polysulfide Immobilization and Ultrahigh Sulfur Content in Lithium-Sulfur Batteries.

A high sulfur loading cathode is the most crucial component for lithium-sulfur batteries (LSBs) to obtain considerable energy density for commercialization applications. The major challenges associated with high sulfur loading electrodes are poor material utilization caused via the nonconductivity of the charged product (S) and the discharged product (Li2S), poor stability arisen from dissolution of lithium polysulfides (LiPSs) into most organic electrolytes and pulverization, and structural damage of the electrode caused by large volumetric expansion. A multifunctional synergistic composite enables ultrahigh sulfur content for advanced LSBs, which comprises the sulfur particle encapsulated with an ion-selective polymer with conductive carbon nanotubes and dispersed around Magnéli phase Ti4O7 (MS-3) by the bottom-up method. The ion-selective polymer provides a physical shield and electrostatic repulsion against the shuttling of polysulfides with negative charge, whereas it can permit the transmission of lithium ion (Li+) through the polymer membrane, and the carbon nanotubes twined around the sulfur promote electronic conductivity and sulfur utilization as well as strong chemical adsorption of LiPSs by means of Ti4O7. Because of this hierarchical construction, the cathode possesses a lofty final sulfur loading of 72% and large sulfur areal mass loading of 3.56 mg cm-2, which displays the large areal specific capacity of 4.22 mA h cm-2. In the same time, it can provide excellent cyclic performance with the corresponding capacity attenuation ratio of 0.08% per cycle at 0.5 C after 300 cycles. Especially, while sulfur areal mass loading is sharply enhanced to 5.11 mg cm-2, the MS-3 composite exhibits a large initial areal capacity of 5.04 mA h cm-2 and still keeps a high reversible capacity of 696 mA h g-1 at 300th cycle even at a 1.0 C. The design of high sulfur content cathodes is a viable approach for boosting practical commercialized application of LSBs.

Potentiometric Graphite Coated Electrode Based on Ditertbutyl-cyclohexano18crown6 for Detection of Strontium (II) Ions

In this work, a highly sensitive strontium ion selective polymer membrane coated on a graphite electrode based on ditertbutylcyclohexano18crown6 as ionophore is described. The sensor responds to strontium ions in a linear concentration range of 10-5 - 10-1 M with a Nernstian slope of 29.1 ± 0.3 mV/decade and a detection limit of 4.0×10-6 M in the pH range of 3.0 - 10.6. It has a fast response time of less than 10 s and can be used for at least 5 months without any considerable divergence in its potentials. The proposed sensor revealed good selectivity for strontium ions with respect to other cations and was used as an indicator electrode in the potentiometric titration of strontium ions with EDTA and also in the determination of strontium ions in binary mixtures and different real samples.

The Effect of Hydrogen Bonding in Enhancing the Ionic Affinities of Immobilized Monoprotic Phosphate Ligands.

Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl ester phosphate ligands developed in this report operate from acidic solutions. They have been prepared on polystyrene-bound ethylene glycol, glycerol, and pentaerythritol, and it is found that intra-ligand hydrogen bonding affects their metal ion affinities. The affinity for a set of trivalent (Fe(III), Al(III), La(III), and Lu(III)) and divalent (Pb(II), Cd(II), Cu(II), and Zn(II)) ions is greater than that of corresponding neutral diethyl esters and phosphonic acid. In an earlier study, hydrogen bonding was found important in determining the metal ion affinities of immobilized phosphorylated polyol diethyl ester coordinating ligands; their Fourier transform infrared (FTIR) band shifts indicated that the basicity of the phosphoryl oxygen increased by hydrogen bonding to auxiliary –OH groups on the neighboring polyol. The same mechanism is operative with the monoprotic resins along with hydrogen bonding to the P–OH acid site. This is reflected in the FTIR spectra: the neutral phosphate diethyl ester resins have the P=O band at 1265 cm−1 while the monoethyl ester resins have the band shifted to 1230 cm−1; hydrogen bonding is further indicated by the broadness of this region down to 900 cm−1. The monoprotic pentaerythritol has the highest metal ion affinities of the polymers studied.

Electrochemical Mechanism of Room Temperature Sodium/Sulfur Battery with Tegdme Electrolyte

The high temperature Na/S battery working above 300°C has been highlighted as a promising candidate for large scale energy storage systems. It carries many advantages such as low-cost raw materials, high energy density (760 Wh kg-1), high coulombic efficiency, and a long cycle life. However, it suffers from critical problems of the safety issue, etc. For example, sulfur and sodium polysulfides are in the liquid state and react with sodium vigorously. In the case of a failure of solid electrolyte separator (β"-Al2O3), a fire or an explosion can take place. The room temperature Na/S battery with tetraethylene glycol dimethyl ether (TEGDME) electrolyte (hereafter referred to as the Na/S battery) can overcome these drawbacks. Furthermore, assuming Na2S as the final discharge product, sulfur cathode has a high theoretical specific capacity of 1672 mAh g- 1 and the Na/S battery has a high theoretical energy density of 1230 Wh kg-1. Sulfur in the Na/S cell has been reported to involve complicated transition processes during charge/discharge. It evolves from S8 to Na2S through various sodium polysulfides such as Na2S6, Na2S5, Na2S4, Na2S3 and Na2S2 during the discharge and does reversely during charge. Especially, the high-order polysulfides (Na2Sn, 4 ≤ n ≤ 8) are generally believed to dissolve into the TEGDME electrolyte, bringing a number of drawbacks such as low discharge capacity, fast capacity decay during cycling and deterioration of the sodium anode due to the shuttle effect. Thus, some strategies such as a solid electrolyte separator (β"-Al2O3), ion selective polymer membranes, and interlayers have been applied to suppress the shuttle effect of the high-order polysulfides (Na2Sn, 4 ≤ n ≤ 8). Inversely, there have also been several studies such as catholyte system to use their soluble properties. The low-order ones (Na2Sn, 1 ≤ n ≤ 3) are considered to generally be in the solid state and contribute to the low discharge capacity and high polarization due to the low electronic and ionic conductivities. These mean that understanding the evolution of sulfur in the cathode to sodium polysulfides (Na2Sn, 1 ≤ n ≤ 8), based on solubility, is critical for understanding and developing the Na/S battery. However, previous studies have focused only on identifying the chemical species of sodium polysulfides (Na2Sn, 1 ≤ n ≤ 8), which were even partially identified, and there has been no study on the Na/S battery in viewpoint of the solubilities of sodium polysulfides (Na2Sn, 1 ≤ n ≤ 8). In the present study, we aim to investigate the formation and variation of sodium polysulfides during charge/discharge. Sulfur cathode and sodium anode are examined at different points of the charge/discharge by separating both electrodes with the beta alumina solid electrolyte separator (β"-Al2O3). The solubilities of sodium polysulfides of Na2Sn (1 ≤ n ≤ 8) are measured and compared to the sulfur cathode visually.

Performance Enhancement of Capacitive Deionization By Using Ionomer-Combined Carbon Electrodes and Pore-Filled Ionomer Membranes

Ion selective polymers (ionomers) are currently widely used in water treatment applications such as the diffusion dialysis, electrodialysis, and capacitive deionization for the desalination of brackish water, production of table salt, recovery of valuable metals from the effluents of metal-plating industry, and recoveries of acid and base from the spent leaching solutions. The functional ionomers are also utilized in various energy devices such as polymer electrolyte membrane fuel cells, redox flow batteries and so on. Especially, capacitive deionization (CDI) is thought to be one of the attractive environmentally-friendly desalination processes. It consumes relatively small energy for operation compared with other competing processes such as reverse osmosis. In addition, it does not produce any secondary regeneration wastes for a re-use. Comparing to the conventional CDI, membrane-CDI (MCDI) and ionomer coated-CDI have gained great interests due to the higher ion selectivity and removal efficiency. In this work, therefore, we have synthesized and characterized functional ionomers for the successful CDI application. The anion-exchange polymer was made from poly(2,6-dimethyl-1,4-phenylene oxide) through the bromination and consecutive amination processes. Meanwhile, the cation-exchange polymer was prepared via the sulfonation of polyetheretherketon. The functionalized ionomers exhibited excellent electrochemical properties of both the low electrical resistance and high ion selectivity. As a result, the functionalized ionomers which were coated on porous carbon electrodes largely improved the current and salt removal efficiencies of the CDI process. We have also developed a pore-filled IEMs (PFIEMs) for the applications to cost and energy efficient CDI processes. The PFIEMs composed of a highly inert and tough porous substrate and a polymer with functional groups that fills the pores can provide both high ion conductivity and excellent mechanical properties. In addition, the PFIEMs could be produced in a cheaper way by a roll-to-roll continuous process. The PFIEMs with a film thickness below 50 μm have been successfully prepared and characterized via various electrochemical analyses. As a result, they were shown to possess excellent electrochemical and mechanical properties. Their electrochemical characteristics have also been optimized for the successful applications to MCDI processes. (This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2015H1C1A1034436) and also by the Technology Innovation Program funded by the Ministry of Trade, industry & Energy (MOTIE) (No. 10047796).)

Surface-modified spherical activated carbon for high carbon loading and its desalting performance in flow-electrode capacitive deionization

We fabricated surface modified activated carbons covered with ion-selective polymer. These materials can be used as powerful dispersants and flow electrodes, and improved desalting efficiency by high carbon loading via electrostatic repulsion.