WO2023193836A1 - Flow-through electrode assembly having a multilayered structure and use thereof - Google Patents

Flow-through electrode assembly having a multilayered structure and use thereof Download PDF

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Publication number
WO2023193836A1
WO2023193836A1 PCT/CZ2022/050036 CZ2022050036W WO2023193836A1 WO 2023193836 A1 WO2023193836 A1 WO 2023193836A1 CZ 2022050036 W CZ2022050036 W CZ 2022050036W WO 2023193836 A1 WO2023193836 A1 WO 2023193836A1
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Prior art keywords
membrane
flow
chamber
electrode
electrically
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PCT/CZ2022/050036
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French (fr)
Inventor
Petr MAZUR
Zdenek Slouka
Stepan HALADA
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Vysoka Skola Chemicko-Technologicka V Praze
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Priority to PCT/CZ2022/050036 priority Critical patent/WO2023193836A1/en
Publication of WO2023193836A1 publication Critical patent/WO2023193836A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184—Regeneration by electrochemical means
    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/46—Apparatus therefor
    • B01D61/461—Apparatus therefor comprising only a single cell, only one anion or cation exchange membrane or one pair of anion and cation membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/46—Apparatus therefor
    • B01D61/463—Apparatus therefor comprising the membrane sequence AC or CA, where C is a cation exchange membrane
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/52—Accessories; Auxiliary operation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4691—Capacitive deionisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/78—Cases; Housings; Encapsulations; Mountings
    • H01G11/82—Fixing or assembling a capacitive element in a housing, e.g. mounting electrodes, current collectors or terminals in containers or encapsulations
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/34—Energy carriers
    • B01D2313/345—Electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46133—Electrodes characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/46—Apparatus for electrochemical processes
    • C02F2201/461—Electrolysis apparatus
    • C02F2201/46105—Details relating to the electrolytic devices
    • C02F2201/46115—Electrolytic cell with membranes or diaphragms
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/08—Nanoparticles or nanotubes

Definitions

  • Flow-through electrode assembly having a multilayered structure and use thereof
  • the present invention relates to a flow-through electrode assembly containing electrically-conductive nanomaterial and having a multilayered structure suitable for electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems (such as electrodialysis, electrodeionization, electrophoresis), capacitive deionization, and/or as electrochemical sensors.
  • Multiple flow-through electrode assemblies may be serially connected using a bipolar configuration to form a set to enhance its performance.
  • Nanotechnologies have enabled the synthesis of novel nanostructured materials. Such nanomaterials characterized by one of the linear dimensions smaller than 1 micrometer often exhibit physical or chemical properties surpassing those of bulk materials.
  • the field of electrochemistry is not an exception. Many, especially carbon-based materials, are synthesized with various levels of modification to improve their electrocatalytic properties. Nanostructured materials, intrinsically endowed with large surface area, and short transport distances if arranged properly in space, thus, offer properties tunable for a given electrochemical application.
  • One of the overarching problems in using these materials is the difficulty in their integration into electrochemical systems.
  • the nanostructured conductive materials are primarily available in the form of fine powders or diluted suspensions.
  • nanomaterials onto solid electrode collectors.
  • this is done either by their passive adsorption onto the electrode or by using a binder that provides mechanical support for the nanomaterial and allows easy deposition on the electrode (Zhang, J., et al., Improved hydrophilicity, permeability, antifouling and mechanical performance of PVDF composite ultrafiltration membranes tailored by oxidized low -dimensional carbon nanomaterials. 2013. 1(9): p. 3101-3111).
  • the passive sorption is characterized by the low stability of the nanostructured material on the electrode.
  • the stability is worsened in flow- through systems in which the passively adsorbed layer is exposed to shear forces of the invoked flow.
  • the use of a binder intrinsically means that most of the nanomaterial is encapsulated in the binder with no access to the surrounding environment.
  • the encapsulated nanomaterial cannot fulfill its (electrocatalytic) role in the electrochemical system.
  • the binder (usually nonconductive) also increases the resistance of the system.
  • the use of ionomeric binders can alleviate the problem only partially (Pyo, J.-B., J.H. Kim, and T.-S. J.
  • the integrated nanomaterial creates a 3D electrode.
  • a 3D electrode is materialized as a nanomaterial fixed bed localized in a channel (i) either actively flowed through by an electrolyte solution or (ii) exposed to a stagnant solution.
  • the bed of the nanostructured materials (3D electrode) is in direct contact with a current collector connected to a power supply to allow the polarization of the 3D electrodes and control the electrochemical processes occurring on them.
  • the electrodes of nanostructured materials are characterized by (i) large surface areas available for charge storage and proceeding faradaic electrochemical reactions and (ii) very short transport distances for the electroactive or ionic species.
  • Cyclic voltammetry measured on a system with and without a nanomaterial fixed bed in the presence of the vanadium solution in sulfuric acid used as a background electrolyte is a system documenting these features.
  • the electric current densities for the system with a nanomaterial bed reach values two orders of magnitude higher than those without a nanomaterial bed.
  • Electrochemical reactors redox flow batteries, capacitor batteries, electro(membrane) separation systems (electrodialysis, electrodeionization, electrophoresis), systems for capacitive deionization, or electrochemical sensors are examples of such systems.
  • the object of the present invention is a flow-through electrode assembly having a multilayered structure, comprising in the following order:
  • the first and second electrode plates contain a layer from an electrically non-conductive material, comprising a chamber for electrically-conductive nanomaterial; an inlet channel for conducting an electrolyte solution from the stock of electrolyte solution to the chamber; an outlet channel for conducting the electrolyte solution from the chamber to the stock of electrolyte solution; and electrically-conductive nanomaterial localized in the chamber and adapted for being exposed to the electrolyte solution; wherein the electrically-conductive nanomaterial localized in the chamber is in direct contact with the first or second current collector and with the membrane layer (i.e.
  • the electrically-conductive nanomaterial localized in the chamber of the first electrode plate is in direct contact with the first current collector and with the membrane layer; the electrically-conductive nanomaterial localized in the chamber of the second electrode plate is in direct contact with the second current collector and with the membrane layer); and wherein the membrane layer comprises a membrane selected from the group comprising a cationexchange membrane (CEM), anion-exchange membrane, dialysis membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.
  • CEM cationexchange membrane
  • the cation-exchange membrane is selected from the group comprising heterogeneous and homogeneous membranes with strong-acid functional groups such as sulfones.
  • Electrolytes suitable for this membrane type are typically water solutions of inorganic salts, such as salts of strong inorganic acids H3PO4, HC1) with cations of alkaline metals, alkaline earth metals, vanadium (V 3+ , V 4+ ).
  • the alkaline metal ions are monovalent ions of metals of the IA group of the periodic table which include Li + , Na + , K + , Rb + , Cs + .
  • the alkaline earth metal ions are divalent ions of metals of the IIA group of the periodic table which include preferably Mg 2+ , Ca 2+ .
  • the anion-exchange membrane is selected from the group comprising heterogeneous and homogeneous membranes with strong-base functional groups such as quaternary ammonium groups.
  • Electrolytes suitable for this type of membrane are typically water solutions of inorganic salts as in the case of cation-exchange membrane electrolytes.
  • the dialysis membrane is selected from the group comprising cellulose membranes.
  • Electrolytes suitable for this type of membrane are typically water solutions containing small and large organic and inorganic molecules (up to 60 kDa), such as urea, glucose, small proteins (cytokines), hormones, creatinine, etc.
  • small and large organic and inorganic molecules up to 60 kDa
  • the ultrafiltration membrane is selected from the group comprising polysulfone, polyvinylidene fluoride, polyacrylonitrile, polypropylene, cellulose acetate, polylactic acid membranes.
  • Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 1 micrometer, such as bacteria, viruses, solid particles, toxins, etc.
  • the nanofiltration membrane is selected from the group comprising polyamide, cellulose triacetate, aromatic polyamide, cellulose acetate membranes.
  • Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 10 nanometers, such as solutions containing divalent ions (Ca 2+ , Mg 2+ , ... ), and larger ionic molecules, most of the organic molecules, etc.
  • the reverse osmosis membrane is a membrane from a material selected from the group comprising polyamide, microporous polysulfone, and polyester. Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 2 nanometers (ions), such as monovalent ions (K + , Na + , Cl’,... ).
  • the current collector is preferably a planar current collector, which may be, for example, made from a metal foil (the metal is preferably selected from the group comprising Al, Cu).
  • the thickness of the current collector layer defined above is in the range of from 1 mm to 2 cm.
  • An electrically non-conductive material is defined as a material having the electrical resistivity at 20 °C greater than 10 3 m.
  • a nanomaterial is defined as a material of which a single particle has in at least one dimension a size in the range of from 1 to 100 nm.
  • a single particle of the nanomaterial has in any of its dimensions a size not exceeding 100 nm.
  • An electrically-conductive nanomaterial is defined as a nanomaterial, which allows a flow of electric current, thus having the electrical resistivity at 20 °C in the range from 10 3 to 10' 8 Q m.
  • the electrical resistivity is measured using the four-point van der Pauw method.
  • the particle size of a nanomaterial is determined using transmission electron microscopy (TEM).
  • the thickness of the membrane layer defined above is in the range of from 0.3 mm to 8 mm.
  • the layer from the electrically non-conductive material of the electrode plate has a thickness in the range of from 1 to 30 mm.
  • the electrically non-conductive material may be, for example, selected from the group comprising elastomers and thermoplastics such as polyethylene, polypropylene, plexiglass, polycarbonate, polyvinyl chloride, teflon, and other perfluorinated polymers, polydimethylsiloxane, silicone, light-curable flexible resins, etc.
  • the electrically-conductive nanomaterial is selected from the group comprising nanostructured carbon-based materials, such as carbon nanotubes, carboxylic acid functionalized carbon nanotubes, octadecylamine functionalized carbon nanotubes, poly(ethylene glycol) functionalized carbon nanotubes, amide functionalized carbon nanotubes, polyaminobenzene sulfonic acid functionalized carbon nanotubes or graphene oxide, ammonia functionalized graphene oxide, reduced graphene oxide or polypyrrole of preferably from 40 to 60 monomeric units, polyethylene- carbon filled.
  • nanostructured carbon-based materials such as carbon nanotubes, carboxylic acid functionalized carbon nanotubes, octadecylamine functionalized carbon nanotubes, poly(ethylene glycol) functionalized carbon nanotubes, amide functionalized carbon nanotubes, polyaminobenzene sulfonic acid functionalized carbon nanotubes or graphene oxide, ammonia functionalized graphene oxide, reduced graphene oxide or polypyrrole of
  • the flow-through electrode assembly comprises the same electrically-conductive nanomaterial in the first and second electrode plates.
  • the electrically-conductive nanomaterial contained in the first electrode plate of the flow-through electrode assembly is different from the electrically-conductive nanomaterial contained in the second electrode plate.
  • Most preferred are the combinations of membranes, electrically- conductive materials and electrolytes as summarized in Table below:
  • the flow-through electrode assembly further comprises a filter located at the entrance of the inlet and the outlet channels of the chamber.
  • the filter may be, e.g., a filtration fabric.
  • the filter is selected from the group of materials comprising polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), graphite felt (GF).
  • PET polyethylene terephthalate
  • PE polyethylene
  • PP polypropylene
  • GF graphite felt
  • the chamber may have a volume in the range of from 1 pl to 100 ml.
  • the dimensions of the chamber are typically in the range of from hundreds of micrometers to tens of centimeters, with volumes from a few microliters up to several milliliters.
  • the dimensions of the chamber are in the range of from 100 pm to 30 cm, with volumes in the range of from 1 pl to 10 ml.
  • Contact areas between the current collector and the nanostructured bed can be as large as 50 cm 2 if an internal supporting division is included.
  • the contact area between the current collector and the nanostructured bed is in the range of from 0.5 cm 2 to 30 cm 2 , more preferably from 1 cm 2 to 15 cm 2 , even more preferably from 2 cm 2 to 10 cm 2 .
  • the internal supporting division is provided within the chamber for contact areas greater than 30 cm 2 .
  • the internal supporting division may be provided by a grid, made of a non-conductive material such as those listed above, located within the chamber. The volume of the chamber defines the amount of nanostructured materials needed.
  • the electrode plate is made from polymethylmethacrylate (PMMA) of a thickness in the range of from 1 mm to 3 cm.
  • the chamber has a volume in the range of from 1 cm 3 to 100 cm 3 .
  • the chamber is filled with carbon nanotubes as the electrically-conductive nanomaterial.
  • Filtration fabrics preferably 100 % polyethylene terephthalate (PET) filtration fabrics, is placed at the entrance of the inlet and outlet channels into the chamber.
  • the inlet channel is preferably connected to a peristaltic pump for delivering the electrolyte from the stock solution to the chamber.
  • the flow-through electrode assembly further comprises a sealing layer located between the first current collector and the first electrode plate and/or between the second current collector and the second electrode plate.
  • the sealing layers have their thickness from tens of micrometers to hundreds of micrometers, more preferably in the range of from 10 pm to 500 pm.
  • the sealing layers are made from an electrically nonconductive elastomeric material, more preferably selected from the group comprising silicone, siloxanes, Teflon, polyethylene, polypropylene, or elastomeric polyolefin, such as polyisobutylene (PIB) or ethylene propylene rubber (EPR).
  • the sealing layers are provided with an aperture enabling direct contact between the electrically-conductive nanomaterial localized in the chamber with the respective current collector.
  • Elastomeric material can be defined as a polymer that displays rubber-like elasticity.
  • another sealing layer may be provided between the first electrode plate and the membrane layer; and/or between the second electrode plate and the membrane layer.
  • the sealing layer is provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber with the membrane layer.
  • the sealing layers prevent leakage of electrolytes from the device.
  • the material and thickness of the sealing layers is as defined above.
  • the flow-through electrode assembly may further comprise a peristaltic pump for enabling the flow of the electrolyte solution from the stock of electrolyte solution to the respective chambers. Any kind of peristaltic pump may be used, which is known to the skilled person and suitable for intended volumes and flow rates of the electrolyte.
  • a system with a pair of membranes separating the main channel from the electrodes can be used, e.g., for capacitive electrodialysis.
  • Capacitive electrodialysis removes ions from the processed solution by their storage on a polarized solid electrode surface.
  • the membrane layer of the flow-through electrode assembly contains in the following order a first selective membrane, a middle plate, and a second selective membrane.
  • the first selective membrane is in direct contact with the electrically-conductive nanomaterial localized in the first electrode plate
  • the second selective membrane is in direct contact with the electrically- conductive nanomaterial localized in the second electrode plate
  • the middle plate between the two membranes contains an inlet for a solution to be processed, an outlet for the processed solution, and a cutout (aperture) for enabling direct contact of the solution to be processed with the first and second selective membranes.
  • the fixed bed of nanostructured material in the electrode plates is used for this purpose, i.e., these 3D electrodes temporarily store ionic species when the system is polarized in the DC electric field.
  • the processed solution is separated from the electrode plates with the membranes discussed above, displaying selectivity towards the (ionic) components of the processed electrolyte.
  • these membranes are ion-exchange membranes, e.g., cation- and anion-exchange membranes.
  • any solid membrane can be used based on the required selectivity towards the desired electrochemical process applied to the processed solution. Examples of such membranes are the following: dialysis membranes, ultrafiltration, nanofiltration membranes, or reverse osmosis membranes, as discussed above.
  • the material of the middle plate is plastic, more preferably polycarbonate (PC).
  • PC polycarbonate
  • the ionic components of the solution to be processed migrate from the processed solution through the corresponding selective membranes to the electrode plates containing nanostructured material, on which they create an electric double layer.
  • This process can be likened to battery charging.
  • the nanomaterial chambers of the electrode plates are preferably connected to a pump enabling rinsing of the nanomaterial after its use.
  • the thickness of the first selective membrane is in the range of from 100 gm to 1000 gm.
  • the thickness of the second selective membrane is in the range of from 100 gm to 1000 gm.
  • the thickness of the middle plate is in the range of from 0.3 mm to 1.5 mm.
  • the overall thickness of the membrane layer is as defined above.
  • the flow-through electrode assembly further comprises two sealing layers located between the first electrode plate and the first selective membrane; and/or between the second electrode plate and the second selective membrane.
  • the sealing layers are provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber with the respective selective membrane.
  • the sealing layers prevent leakage of electrolytes from the device.
  • the material and thickness of the sealing layers is as defined above.
  • the flow-through electrode assembly further comprises another two sealing layers located within the membrane layer; one sealing layer located between the first selective membrane and the middle plate; and the second sealing layer located between the second selective membrane and the middle plate; wherein the sealing layers are provided with an aperture for contacting the solution to be processed with the respective selective membrane.
  • the material and thickness of the sealing layers is as defined above.
  • the flow-through electrode assembly further comprises a peristaltic pump for enabling the flow of the solution to be processed via the inlet through the cutout to the outlet of the middle plate of the membrane layer.
  • a peristaltic pump for enabling the flow of the solution to be processed via the inlet through the cutout to the outlet of the middle plate of the membrane layer.
  • Any kind of peristaltic pump may be used, which is known to the skilled person and suitable for intended volumes and flow rates of the solution to be processed.
  • a further object of the present invention is a set of at least two flow-through electrode assemblies as described above, wherein the flow-through electrode assemblies are serially connected using a bipolar configuration.
  • the serial connection of the electrode assemblies in a bipolar configuration enables to configure the system for its performance or throughput in a given application.
  • the number of the assemblies modifies the voltage generated on flow batteries or the throughput of the feed processed by capacitive deionization.
  • Serial connection using a bipolar configuration is defined as a repetition of flow-through electrode assemblies as described above with two adjacent flow- through electrode assemblies sharing a single current collector.
  • the second current collector of the first electrode assembly forms the first current collector of the second electrode assembly in such a serial connection. This electrode collector becomes a bipolar electrode.
  • Another object of the present invention is the use of the flow-through electrode assembly having a multilayered structure or of their set according to the present invention in electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems, capacitive deionization, and/or as electrochemical sensors.
  • Figure 7 Cyclic voltammograms for a flat current collector (black curve) and a 3D electrode made of nanostructured material created on the same current collector (gray curve) measured in a 1.6 mol • dm -3 of vanadium (equimolar mixture of vanadium in oxidation states III and IV), 2 mol dm -3 of H2SO4 and 0.3% of H3PO4.
  • FIG. 2 Schematics of a system in which two 3D electrodes are connected to flow-through channels: al and a2 denote the first and second current collectors; bl and b2 the sealing layers with cutouts for electrically-conductive nanomaterial and fluidic fittings; cl and c2 the electrode plates with chambers (cl.3 and c2.3) (cutouts) for the electrically-conductive nanomaterials, inlet (cl.1 and c2.1) and outlet (cl.2 and c2.2) channels, and space for the filtration fabric (cl.4.a, cl.4.b, c2.4.a, c2.4.b); dl and d2 denote the sealing layers with a cutout; and el is the membrane layer separating the cathode and anode compartment.
  • FIG. 3 A detailed view of an electrode plate: cl.l and cl.2 are the inlet and outlet channels, cl.4.a and cl.4.b are the pieces of filtration fabrics, and cl.3 is the chamber filled with an electrically- conductive nanomaterial.
  • FIG. 4 Polarization curves measured for a vanadium redox flow battery with the electrodes made of nanostructured carbon-based materials, state of charge (SOC) 50 %, temperature 25 °C.
  • Figure 5 Schematic of a system with a pair of membranes separating the processed solution from the 3D electrodes: al and a2 denote the current collectors; bl and b2 the sealing layers with cutouts for contacting electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) with the respective current collector (al; a2).; cl and c2 the electrode plates with chambers (cl.3 and c2.3) for the electrically-conductive nanomaterials, inlet (cl.l and c2.1) and outlet (cl.2 and c2.2) channels, and space for the filtration fabric (cl.4.a, cl.4.b, c2.4.a, c2.4.b); dl and d2 the sealing layers with a cutout; el.l
  • Figure 6 Capacitive desalination as a function of the applied current for a system with electrodes made of nanostructured carbon-based materials: experimental data -points, theoretical prediction - dots in line.
  • Figure 3 depicts an electrode plate (cl) made of polymethylmethacrylate (PMMA) (electrically non- conductive material) of a thickness of 1 cm.
  • a chamber (cl.3) in a shape of a parallelogram with a volume of 2.25 cm 3 is located within the plate (cl), which is suitable for placing therein the electrically-conductive nanomaterial of 5 grams weight.
  • the inlet (cl.l) and outlet (cl.2) channels connect the chamber (cl.3) with the stock of electrolyte solution.
  • Example 2 A two-electrode system with a single membrane separating the catholyte and anolyte
  • Figure 2 depicts the schematic of the developed electrochemical system (a multilayered flow-through electrode assembly) in which multiwall carbon nanotubes were used as a 3D electrode in the form of a fixed layer.
  • the system is multilayered and comprises (i) two planar current collectors (al; a2) made from aluminium and of a thickness of 1.5 mm, (ii) two electrode plates (cl; c2) made of non- conductive polymethylmethacrylate (PMMA)) with cutouts defining the geometry of the fixed bed chamber (cl.3; c2.3) and the inlet (cl.
  • Example 1 a set of elastomeric polyolefin or silicone sealing layers (bl;b2) and (dl;d2) located from each side of the electrode plate (cl; c2), the sealing layers being provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber (cl .3 ; c2.3) with the respective current collectors (al ; a2) and with the membrane layer (el ), wherein the membrane layer (el) is a functional membrane.
  • the functional membrane was a cation-exchange membrane.
  • the electrode plates (cl; c2) for inserting the nanostructured materials are as described in Example 1.
  • the cutouts in electrode plates are called nanomaterial chambers (cl.3; c2.3) and are be designed to have characteristic volumes from a few microliters up to several milliliters. Even larger volumes up to tens of milliliters are possible if an internal supporting division is included.
  • the internal division can be realized as a grid made of porous material, enabling the flow of the electrolyte. Their volume defines the amount of nanostructured materials needed. In this specific embodiment, the volume of the nanomaterial chambers (cl.3; c2.3) was 2.25 cm 3 .
  • the inlet (cl.l; c2.1) and outlet (cl.2; c2.2) channels are directly connected to these nanomaterial chambers (cl.3; c2.3). Their entrance and exit are provided with a specifically designed space for placing a filter (cl.4. a; c2.4.a; cl.4.b; c2.4.b), such as filtration fabric.
  • the space tightly accommodates the filter and renders it mechanically immovable.
  • the filtration fabric employed for this purpose was 100 % polyethylene terephthalate (PET) with the brand name FINET PES 3 obtained from MITOP.
  • the filters anchor the electrically-conductive nanomaterial in the nanomaterial chamber (cl.3; c2.3) and prevent it from being washed out when an electrolyte flow through the nanomaterial chambers (cl.3; c2.3) is applied.
  • the thickness of the sealing layers (bl; dl; b2; d2) was 0.5 mm, and the thickness of the membrane layer (el) was 0.3 mm.
  • the assembly of such an electrochemical system proceeds in the following way.
  • the current collectors (al; a2) are provided with a sealing layer (bl; b2) that contains cutouts for contacting the fixed bed of electrically-conductive nanomaterial in the chambers (cl.3; c2.3).
  • the electrode plates (cl; c2) are placed on these sealing layers (bl ; b2), and the filters (cl ,4.a; c2.4.a; cl ,4.b; c2.4.b), such as filtration fabric of a specific size, are inserted into the respective spots at the entrance of the inlet and outlet channels (cl. l; c2.1; cl.2; c2.2) into the chamber (cl.3; c2.3).
  • the nanomaterial chambers (cl.3; c2.3) are then filled with the electrically-conductive nanomaterial, preferably selected from the group comprising carbon nanotubes, tubes of conductive polymers, etc. as defined above.
  • the chambers (cl.3; c2.3) were filled with multiwall carbon nanotubes.
  • another sealing material layer (dl; d2) was placed on top of the electrode plates (cl; c2).
  • the contact of the electrically-conductive nanomaterial and the current collectors (al; a2), which is crucial for the flawless operation of the system, is provided by the compressive force applied to the nanostructured bed when assembling the system.
  • the compressive force applied to the nanostructured bed when assembling the system is provided by the compressive force applied to the nanostructured bed when assembling the system.
  • the volume of the used electrically-conductive nanomaterial is larger by approximately 10 % than the volume of the chamber (cl.3; c2.3)
  • a thin layer of a porous and compressible material such as felt
  • the electrode plates (cl; c2) are made of a compressible material, for example, Engineering LCD Series Flex 63A Resin Clear.
  • any compressible electrically non-conductive material in which the required structures can be made can be used.
  • a functional membrane layer (el) separating a catholyte from an anolyte is placed between the two prepared electrode plate sandwiches, and the whole system is pressed together in a vice.
  • Such a system can be primed with the working solution by using a peristaltic pump.
  • An example of a filled nanomaterial chamber is depicted in Figure 3.
  • the developed flow-through electrode assembly having a multilayered structure with 3D electrodes made of nanostructured materials was tested as a vanadium redox flow battery.
  • the testing experiment proceeded in the following way. 20 mg of multiwall carbon nanotubes were weighted out and moistured for 24 hours in the working electrolyte vanadium solution containing 1.6 M vanadium (an equimolar mixture of vanadium in oxidation states III and IV), 2M sulfuric acid, and 0.3% H3PO4.
  • the current collectors (al; a2), sealing layers (bl; b2), and electrode plates (cl; c2) were stacked, and a filtration fabric MITOP FINET PES 3 was placed at the designated positions of filters (cl .4.
  • a; c2.4.a; cl ,4.b; c2.4.b located at the entrance of the inlet (cl .1 ; c2.1) and outlet (c2.1 ; c2.2) channels into the chamber (cl.3; c2.3) of each electrode plate (cl; c2).
  • the moist multiwall carbon nanotubes were then transferee! into the nanomaterial chambers (cl.3; c2.3).
  • the electrodes plates (cl; c2) were provided with a sealing layer (dl; d2) made from an elastomeric polyolefin, and a cation-exchange membrane was placed between these sealings. The whole system was firmly stacked together in a vice.
  • the inlet channels (el.l; c2.1) were connected to a peristaltic pump, and the current collectors (al; a2) were connected with leads to a potentiostat.
  • a peristaltic pump provided the flow of catholyte and anolyte electrolytes stored in a flask under a nitrogen atmosphere. The electrolyte was charged to 50 % of its theoretical capacity under an applied current of 100 mA. The charging of 5 ml of the vanadium solution took 7719 s.
  • Discharging and charging load characteristics were measured at the electrolyte volumetric flow rates of 100, 300, and 500 pl/min with the applied discharging and charging current densities ranging from 15 to 95 mA/cm 2 . These volumetric flow rates correspond to the linear velocities of 0.2, 0.6, and 1 cm/min.
  • the results of the conducted study are plotted in Figure 4 in the form of polarization curves.
  • Example 3 A two-electrode system with a pair of membranes separating the electrodes from the main channel
  • a schematic of the multilayered flow-through electrode assembly with a pair of membranes separating the main channel from the electrodes was used (see Figure 5) for capacitive electrodialysis.
  • the fixed bed of electrically-conductive nanomaterial was used for this purpose, i.e., these 3D electrodes temporarily stored ionic species when the system was polarized in the DC electric field.
  • the processed solution was separated from the electrode plates (cl; c2) with a pair of selective (ion-exchange) membranes (el.l; el.2) of thickness of 0.3 mm, displaying the selectivity towards the (ionic) components of the processed electrolyte solution.
  • the membranes were separated by a middle plate (gl), made from polycarbonate (PC) and having thickness of 1 mm, and containing an inlet (gl.l) for a solution to be processed, an outlet (gl.2) for the processed solution, and a cutout (gl.3) for enabling direct contact of the solution to be processed with the first and second selective membranes (el.l; el.2).
  • the ionic components migrate from the processed solution through the corresponding first and second membranes (el.l; el.2) to the electrodes made of nanostructured material, on which they create an electric double layer.
  • This process can be likened to battery charging.
  • the chambers (cl.3; c2.3) with the fixed bed of the nanomaterial were filled with the electrolyte solution before starting the experiment. This solution was stagnant in the nanomaterial chambers (cl.3; c2.3) during the experiment.
  • the remaining features of the assembly were as described in Examples 1 and 2.
  • the flow-through electrode assembly thus comprises (i) two current collectors (al; a2); (ii) two electrode plates (cl; c2) having the chambers (cl.3; c2.3) for placing the nanostructured material with auxiliary fluidic input (el.l; c2.1) and output (cl.2; c2.2) channels, and a set of sealing layers on the top and bottom (bl; b2 and dl; d2); (iii) two membranes, e.g., cation- and anion-exchange membrane (el.l; el.2); and (iv) a middle plate (gl) with an inlet (gl.l) and an outlet (gl.2) to conduct the processed solution through the system.
  • the assembly of the system follows the same protocol as described in Example 2.
  • the testing experiment for this system proceeded in the following way.
  • the chambers were filled with moist multiwall carbon nanotubes in the amount of 5 grams given by the dimensions of the nanomaterial chamber with a bottom area of 4.5 cm 2 and a height of 0.5 cm.
  • the inlet (cl.4. a; c2.4.a) and outlet (cl.4.b; c2.4.b) channels of the electrode plates (cl; c2) were equipped with the filtration fabric MITOP FINET PES 3.
  • the electrode plates were aligned with sealing layers (dl; d2) made of elastomeric copolymer, followed by an anion- and cation-exchange membrane (el.l; el.2) on either electrode.
  • the middle plate (gl) having the channels for the processed solution was placed between the ion-exchange membranes covered by sealing layers (fl ; f2) made from an elastomeric copolymer.
  • the nanomaterial chambers (cl.3; c2.3) were primed with deionized water, and the current collectors (al; a2) were connected with leads to a potentiostat.
  • the model electrolyte solution mimicking partially desalted seawater was sodium chloride at a concentration of 0.01 M. Its volumetric flow rate was set to 100 pl/min, and its desalination occurred at constant electric current loads ranging from 0.15 to 1.5 mA.
  • Figure 6 depicts experimentally determined desalination as a function of the applied electric currents (dots) and its comparison to theoretical predictions (line with dots). The theoretical predictions are based on the assumption that Na + and CF ions exclusively carry the electric current.

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Abstract

The present invention relates to a flow-through electrode assembly having a multilayered structure, comprising, in the following order, a first current collector (a1) suitable for being connected to a power supply; a first electrode plate (c1); a membrane layer (e1) for separating electrode plates; a second electrode plate (c2); and a second current collector (a2) suitable for being connected to a power supply; wherein the first and second electrode plates (c1; c2) contain a layer from an electrically non-conductive material, comprising a chamber (c1.3; c2.3) for electrically-conductive nanomaterial; an inlet channel (c1.1; c2.1) for conducting an electrolyte solution from the stock of electrolyte solution to the chamber (c1.3; c2.3); an outlet channel (c1.2; c2.2) for conducting the electrolyte solution from the chamber (c1.3; c2.3) to the stock of electrolyte solution; and electrically-conductive nanomaterial localized in the chamber (c1.3; c2.3) adapted for being exposed to the electrolyte solution; wherein the electrically-conductive nanomaterial localized in the chamber (c1.3; c2.3) is in direct contact with the first or second current collector (a1; a2) and with the membrane layer (e1); and wherein the membrane layer (e1) comprises a membrane selected from the group comprising an ion-exchange membrane, ultrafiltration membrane, reverse osmosis membrane, nanofiltration membrane. The present invention further relates to a set of at least two serially connected flow-through electrode assemblies, and to the use thereof in electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems, capacitive deionization and/or as electrochemical sensors.

Description

Flow-through electrode assembly having a multilayered structure and use thereof
State of Art
The present invention relates to a flow-through electrode assembly containing electrically-conductive nanomaterial and having a multilayered structure suitable for electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems (such as electrodialysis, electrodeionization, electrophoresis), capacitive deionization, and/or as electrochemical sensors. Multiple flow-through electrode assemblies may be serially connected using a bipolar configuration to form a set to enhance its performance.
Background Art
The advent of nanotechnologies has enabled the synthesis of novel nanostructured materials. Such nanomaterials characterized by one of the linear dimensions smaller than 1 micrometer often exhibit physical or chemical properties surpassing those of bulk materials. The field of electrochemistry is not an exception. Many, especially carbon-based materials, are synthesized with various levels of modification to improve their electrocatalytic properties. Nanostructured materials, intrinsically endowed with large surface area, and short transport distances if arranged properly in space, thus, offer properties tunable for a given electrochemical application. One of the overarching problems in using these materials is the difficulty in their integration into electrochemical systems. The nanostructured conductive materials are primarily available in the form of fine powders or diluted suspensions. To exploit them as functional components of electrochemical systems (such as electrodes), one has to deposit nanomaterials onto solid electrode collectors. Today, this is done either by their passive adsorption onto the electrode or by using a binder that provides mechanical support for the nanomaterial and allows easy deposition on the electrode (Zhang, J., et al., Improved hydrophilicity, permeability, antifouling and mechanical performance of PVDF composite ultrafiltration membranes tailored by oxidized low -dimensional carbon nanomaterials. 2013. 1(9): p. 3101-3111).
These two methods, however, suffer from several drawbacks. The passive sorption is characterized by the low stability of the nanostructured material on the electrode. The stability is worsened in flow- through systems in which the passively adsorbed layer is exposed to shear forces of the invoked flow. The use of a binder intrinsically means that most of the nanomaterial is encapsulated in the binder with no access to the surrounding environment. The encapsulated nanomaterial cannot fulfill its (electrocatalytic) role in the electrochemical system. The binder (usually nonconductive) also increases the resistance of the system. The use of ionomeric binders can alleviate the problem only partially (Pyo, J.-B., J.H. Kim, and T.-S. J. J.o.M C.A. Kim, Highly robust nanostructured carbon films by thermal reconfiguration of ionomer binding. 2020. 8(46): p. 24763-24773; Sorsa, O., et al., Optimization and aging of Pt nanowires supported on single-walled carbon nanotubes as a cathode catalyst in polymer electrolyte membrane water electrolyser. 2020. 45(38): p. 19121-19132). In both cases, the nanomaterials preserve the planar arrangement of the electrode to/from which the electroactive component has to diffuse. This arrangement limits the exploitation of the nanomaterial surface area to its full potential.
Disclosure of Invention
We have developed a new method for integrating the conductive nanostructured material in flow- through electrochemical systems. In these systems, represented, e.g., by vanadium redox flow batteries or systems for capacitive deionization, the integrated nanomaterial creates a 3D electrode. Such a 3D electrode is materialized as a nanomaterial fixed bed localized in a channel (i) either actively flowed through by an electrolyte solution or (ii) exposed to a stagnant solution. The bed of the nanostructured materials (3D electrode) is in direct contact with a current collector connected to a power supply to allow the polarization of the 3D electrodes and control the electrochemical processes occurring on them. The electrodes of nanostructured materials are characterized by (i) large surface areas available for charge storage and proceeding faradaic electrochemical reactions and (ii) very short transport distances for the electroactive or ionic species. Cyclic voltammetry measured on a system with and without a nanomaterial fixed bed in the presence of the vanadium solution in sulfuric acid used as a background electrolyte is a system documenting these features. The electric current densities for the system with a nanomaterial bed reach values two orders of magnitude higher than those without a nanomaterial bed.
The developed format of the 3D electrodes can be used virtually in any system requiring an electrode in contact with an electrolyte. Electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems (electrodialysis, electrodeionization, electrophoresis), systems for capacitive deionization, or electrochemical sensors are examples of such systems.
The object of the present invention is a flow-through electrode assembly having a multilayered structure, comprising in the following order:
- a first current collector suitable for being connected to a power supply;
- a first electrode plate;
- a membrane layer for separating electrode plates;
- a second electrode plate;
- a second current collector suitable for being connected to a power supply; wherein the first and second electrode plates contain a layer from an electrically non-conductive material, comprising a chamber for electrically-conductive nanomaterial; an inlet channel for conducting an electrolyte solution from the stock of electrolyte solution to the chamber; an outlet channel for conducting the electrolyte solution from the chamber to the stock of electrolyte solution; and electrically-conductive nanomaterial localized in the chamber and adapted for being exposed to the electrolyte solution; wherein the electrically-conductive nanomaterial localized in the chamber is in direct contact with the first or second current collector and with the membrane layer (i.e. the electrically-conductive nanomaterial localized in the chamber of the first electrode plate is in direct contact with the first current collector and with the membrane layer; the electrically-conductive nanomaterial localized in the chamber of the second electrode plate is in direct contact with the second current collector and with the membrane layer); and wherein the membrane layer comprises a membrane selected from the group comprising a cationexchange membrane (CEM), anion-exchange membrane, dialysis membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.
Typically, the cation-exchange membrane is selected from the group comprising heterogeneous and homogeneous membranes with strong-acid functional groups such as sulfones. Electrolytes suitable for this membrane type are typically water solutions of inorganic salts, such as salts of strong inorganic acids H3PO4, HC1) with cations of alkaline metals, alkaline earth metals, vanadium
Figure imgf000004_0001
(V3+, V4+). The alkaline metal ions are monovalent ions of metals of the IA group of the periodic table which include Li+, Na+, K+, Rb+, Cs+. The alkaline earth metal ions are divalent ions of metals of the IIA group of the periodic table which include preferably Mg2+, Ca2+.
Typically, the anion-exchange membrane is selected from the group comprising heterogeneous and homogeneous membranes with strong-base functional groups such as quaternary ammonium groups. Electrolytes suitable for this type of membrane are typically water solutions of inorganic salts as in the case of cation-exchange membrane electrolytes.
Typically, the dialysis membrane is selected from the group comprising cellulose membranes.
Electrolytes suitable for this type of membrane are typically water solutions containing small and large organic and inorganic molecules (up to 60 kDa), such as urea, glucose, small proteins (cytokines), hormones, creatinine, etc.
Typically, the ultrafiltration membrane is selected from the group comprising polysulfone, polyvinylidene fluoride, polyacrylonitrile, polypropylene, cellulose acetate, polylactic acid membranes. Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 1 micrometer, such as bacteria, viruses, solid particles, toxins, etc.
Typically, the nanofiltration membrane is selected from the group comprising polyamide, cellulose triacetate, aromatic polyamide, cellulose acetate membranes. Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 10 nanometers, such as solutions containing divalent ions (Ca2+, Mg2+, ... ), and larger ionic molecules, most of the organic molecules, etc.
Typically, the reverse osmosis membrane is a membrane from a material selected from the group comprising polyamide, microporous polysulfone, and polyester. Electrolytes suitable for this type of membrane are typically water solutions containing entities with a size below 2 nanometers (ions), such as monovalent ions (K+, Na+, Cl’,... ).
The current collector is preferably a planar current collector, which may be, for example, made from a metal foil (the metal is preferably selected from the group comprising Al, Cu).
Preferably, the thickness of the current collector layer defined above is in the range of from 1 mm to 2 cm. An electrically non-conductive material is defined as a material having the electrical resistivity at 20 °C greater than 103 m.
A nanomaterial is defined as a material of which a single particle has in at least one dimension a size in the range of from 1 to 100 nm. Preferably, a single particle of the nanomaterial has in any of its dimensions a size not exceeding 100 nm.
An electrically-conductive nanomaterial is defined as a nanomaterial, which allows a flow of electric current, thus having the electrical resistivity at 20 °C in the range from 103 to 10'8 Q m.
The electrical resistivity is measured using the four-point van der Pauw method.
The particle size of a nanomaterial is determined using transmission electron microscopy (TEM).
Preferably, the thickness of the membrane layer defined above is in the range of from 0.3 mm to 8 mm.
Preferably, the layer from the electrically non-conductive material of the electrode plate has a thickness in the range of from 1 to 30 mm. The electrically non-conductive material may be, for example, selected from the group comprising elastomers and thermoplastics such as polyethylene, polypropylene, plexiglass, polycarbonate, polyvinyl chloride, teflon, and other perfluorinated polymers, polydimethylsiloxane, silicone, light-curable flexible resins, etc.
In one preferred embodiment, the electrically-conductive nanomaterial is selected from the group comprising nanostructured carbon-based materials, such as carbon nanotubes, carboxylic acid functionalized carbon nanotubes, octadecylamine functionalized carbon nanotubes, poly(ethylene glycol) functionalized carbon nanotubes, amide functionalized carbon nanotubes, polyaminobenzene sulfonic acid functionalized carbon nanotubes or graphene oxide, ammonia functionalized graphene oxide, reduced graphene oxide or polypyrrole of preferably from 40 to 60 monomeric units, polyethylene- carbon filled.
In one embodiment, the flow-through electrode assembly comprises the same electrically-conductive nanomaterial in the first and second electrode plates.
In another embodiment, the electrically-conductive nanomaterial contained in the first electrode plate of the flow-through electrode assembly is different from the electrically-conductive nanomaterial contained in the second electrode plate. Most preferred are the combinations of membranes, electrically- conductive materials and electrolytes as summarized in Table below:
Figure imgf000007_0001
In one embodiment, the flow-through electrode assembly further comprises a filter located at the entrance of the inlet and the outlet channels of the chamber. The filter may be, e.g., a filtration fabric.
Preferably the filter is selected from the group of materials comprising polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), graphite felt (GF). The presence of the filter enables to anchor the nanostructured material in the nanomaterial chamber and prevents it from being washed out by the electrolyte flow.
The chamber may have a volume in the range of from 1 pl to 100 ml. In one embodiment, the dimensions of the chamber are typically in the range of from hundreds of micrometers to tens of centimeters, with volumes from a few microliters up to several milliliters. Preferably, the dimensions of the chamber are in the range of from 100 pm to 30 cm, with volumes in the range of from 1 pl to 10 ml. Contact areas between the current collector and the nanostructured bed can be as large as 50 cm2 if an internal supporting division is included. Preferably, the contact area between the current collector and the nanostructured bed is in the range of from 0.5 cm2 to 30 cm2, more preferably from 1 cm2 to 15 cm2, even more preferably from 2 cm2 to 10 cm2. Preferably, the internal supporting division is provided within the chamber for contact areas greater than 30 cm2. The internal supporting division may be provided by a grid, made of a non-conductive material such as those listed above, located within the chamber. The volume of the chamber defines the amount of nanostructured materials needed.
In a specific embodiment, the electrode plate is made from polymethylmethacrylate (PMMA) of a thickness in the range of from 1 mm to 3 cm. The chamber has a volume in the range of from 1 cm3 to 100 cm3. The chamber is filled with carbon nanotubes as the electrically-conductive nanomaterial. Filtration fabrics, preferably 100 % polyethylene terephthalate (PET) filtration fabrics, is placed at the entrance of the inlet and outlet channels into the chamber. The inlet channel is preferably connected to a peristaltic pump for delivering the electrolyte from the stock solution to the chamber.
In one preferred embodiment, the flow-through electrode assembly further comprises a sealing layer located between the first current collector and the first electrode plate and/or between the second current collector and the second electrode plate. Preferably, the sealing layers have their thickness from tens of micrometers to hundreds of micrometers, more preferably in the range of from 10 pm to 500 pm. More preferably, the sealing layers are made from an electrically nonconductive elastomeric material, more preferably selected from the group comprising silicone, siloxanes, Teflon, polyethylene, polypropylene, or elastomeric polyolefin, such as polyisobutylene (PIB) or ethylene propylene rubber (EPR). The sealing layers are provided with an aperture enabling direct contact between the electrically-conductive nanomaterial localized in the chamber with the respective current collector.
Elastomeric material can be defined as a polymer that displays rubber-like elasticity.
In one embodiment, another sealing layer may be provided between the first electrode plate and the membrane layer; and/or between the second electrode plate and the membrane layer. Similarly, as above, the sealing layer is provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber with the membrane layer. The sealing layers prevent leakage of electrolytes from the device. The material and thickness of the sealing layers is as defined above. In one embodiment, the flow-through electrode assembly may further comprise a peristaltic pump for enabling the flow of the electrolyte solution from the stock of electrolyte solution to the respective chambers. Any kind of peristaltic pump may be used, which is known to the skilled person and suitable for intended volumes and flow rates of the electrolyte.
In one embodiment, a system with a pair of membranes separating the main channel from the electrodes can be used, e.g., for capacitive electrodialysis. Capacitive electrodialysis removes ions from the processed solution by their storage on a polarized solid electrode surface.
In this embodiment, the membrane layer of the flow-through electrode assembly contains in the following order a first selective membrane, a middle plate, and a second selective membrane. The first selective membrane is in direct contact with the electrically-conductive nanomaterial localized in the first electrode plate, the second selective membrane is in direct contact with the electrically- conductive nanomaterial localized in the second electrode plate, and the middle plate between the two membranes contains an inlet for a solution to be processed, an outlet for the processed solution, and a cutout (aperture) for enabling direct contact of the solution to be processed with the first and second selective membranes.
The fixed bed of nanostructured material in the electrode plates is used for this purpose, i.e., these 3D electrodes temporarily store ionic species when the system is polarized in the DC electric field. The processed solution is separated from the electrode plates with the membranes discussed above, displaying selectivity towards the (ionic) components of the processed electrolyte.
Most preferably, these membranes are ion-exchange membranes, e.g., cation- and anion-exchange membranes. However, any solid membrane can be used based on the required selectivity towards the desired electrochemical process applied to the processed solution. Examples of such membranes are the following: dialysis membranes, ultrafiltration, nanofiltration membranes, or reverse osmosis membranes, as discussed above.
Preferably, the material of the middle plate is plastic, more preferably polycarbonate (PC).
Upon applying the electrical current to the current collectors, the ionic components of the solution to be processed migrate from the processed solution through the corresponding selective membranes to the electrode plates containing nanostructured material, on which they create an electric double layer. This process can be likened to battery charging. The nanomaterial chambers of the electrode plates are preferably connected to a pump enabling rinsing of the nanomaterial after its use. Preferably, the thickness of the first selective membrane is in the range of from 100 gm to 1000 gm. Preferably, the thickness of the second selective membrane is in the range of from 100 gm to 1000 gm.
Preferably, the thickness of the middle plate is in the range of from 0.3 mm to 1.5 mm.
In total, the overall thickness of the membrane layer is as defined above.
In a more preferred embodiment, the flow-through electrode assembly further comprises two sealing layers located between the first electrode plate and the first selective membrane; and/or between the second electrode plate and the second selective membrane. The sealing layers are provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber with the respective selective membrane. The sealing layers prevent leakage of electrolytes from the device. The material and thickness of the sealing layers is as defined above.
In an even more preferred embodiment, the flow-through electrode assembly further comprises another two sealing layers located within the membrane layer; one sealing layer located between the first selective membrane and the middle plate; and the second sealing layer located between the second selective membrane and the middle plate; wherein the sealing layers are provided with an aperture for contacting the solution to be processed with the respective selective membrane. The material and thickness of the sealing layers is as defined above.
In one further embodiment, the flow-through electrode assembly further comprises a peristaltic pump for enabling the flow of the solution to be processed via the inlet through the cutout to the outlet of the middle plate of the membrane layer. Any kind of peristaltic pump may be used, which is known to the skilled person and suitable for intended volumes and flow rates of the solution to be processed.
A further object of the present invention is a set of at least two flow-through electrode assemblies as described above, wherein the flow-through electrode assemblies are serially connected using a bipolar configuration. The serial connection of the electrode assemblies in a bipolar configuration enables to configure the system for its performance or throughput in a given application. For example, the number of the assemblies modifies the voltage generated on flow batteries or the throughput of the feed processed by capacitive deionization. Serial connection using a bipolar configuration is defined as a repetition of flow-through electrode assemblies as described above with two adjacent flow- through electrode assemblies sharing a single current collector. For example, the second current collector of the first electrode assembly forms the first current collector of the second electrode assembly in such a serial connection. This electrode collector becomes a bipolar electrode.
Another object of the present invention is the use of the flow-through electrode assembly having a multilayered structure or of their set according to the present invention in electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems, capacitive deionization, and/or as electrochemical sensors.
Brief Description of Drawings
Figure 7: Cyclic voltammograms for a flat current collector (black curve) and a 3D electrode made of nanostructured material created on the same current collector (gray curve) measured in a 1.6 mol • dm-3 of vanadium (equimolar mixture of vanadium in oxidation states III and IV), 2 mol dm-3 of H2SO4 and 0.3% of H3PO4.
Figure 2 Schematics of a system in which two 3D electrodes are connected to flow-through channels: al and a2 denote the first and second current collectors; bl and b2 the sealing layers with cutouts for electrically-conductive nanomaterial and fluidic fittings; cl and c2 the electrode plates with chambers (cl.3 and c2.3) (cutouts) for the electrically-conductive nanomaterials, inlet (cl.1 and c2.1) and outlet (cl.2 and c2.2) channels, and space for the filtration fabric (cl.4.a, cl.4.b, c2.4.a, c2.4.b); dl and d2 denote the sealing layers with a cutout; and el is the membrane layer separating the cathode and anode compartment.
Figure 3: A detailed view of an electrode plate: cl.l and cl.2 are the inlet and outlet channels, cl.4.a and cl.4.b are the pieces of filtration fabrics, and cl.3 is the chamber filled with an electrically- conductive nanomaterial.
Figure 4 Polarization curves measured for a vanadium redox flow battery with the electrodes made of nanostructured carbon-based materials, state of charge (SOC) 50 %, temperature 25 °C. Figure 5 Schematic of a system with a pair of membranes separating the processed solution from the 3D electrodes: al and a2 denote the current collectors; bl and b2 the sealing layers with cutouts for contacting electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) with the respective current collector (al; a2).; cl and c2 the electrode plates with chambers (cl.3 and c2.3) for the electrically-conductive nanomaterials, inlet (cl.l and c2.1) and outlet (cl.2 and c2.2) channels, and space for the filtration fabric (cl.4.a, cl.4.b, c2.4.a, c2.4.b); dl and d2 the sealing layers with a cutout; el.l and el.2 are the first and second selective membranes separating the cathode and anode compartment; fl and f2 the sealing layers separating the selective membranes el.l and el.2 from the middle plate gl; and gl is the middle plate with the main channel for the solution to be processed, containing an inlet (gl.l), a cutout (gl.3) and an outlet (gl.2) for the processed solution.
Figure 6: Capacitive desalination as a function of the applied current for a system with electrodes made of nanostructured carbon-based materials: experimental data -points, theoretical prediction - dots in line.
Examples
Example 1 : Construction of the electrode plate
Figure 3 depicts an electrode plate (cl) made of polymethylmethacrylate (PMMA) (electrically non- conductive material) of a thickness of 1 cm. A chamber (cl.3) in a shape of a parallelogram with a volume of 2.25 cm3 is located within the plate (cl), which is suitable for placing therein the electrically-conductive nanomaterial of 5 grams weight. The inlet (cl.l) and outlet (cl.2) channels connect the chamber (cl.3) with the stock of electrolyte solution. To prevent the electrically- conductive nanomaterial from being washed out when electrolyte flow through the nanomaterial chamber (cl.3) is applied, two pieces of filtration fabrics (cl.4.a, cl.4.b) are placed at the entrance of the inlet and outlet channels into the chamber (cl.3). As the filtration fabrics, MITOP FINET PES 3 was used (100 % polyethylene terephthalate (PET) fabrics). The electrically-conductive nanomaterial (multiwall carbon nanotubes) was localized in the entire volume of the chamber (cl.3).
Example 2: A two-electrode system with a single membrane separating the catholyte and anolyte Figure 2 depicts the schematic of the developed electrochemical system (a multilayered flow-through electrode assembly) in which multiwall carbon nanotubes were used as a 3D electrode in the form of a fixed layer. The system is multilayered and comprises (i) two planar current collectors (al; a2) made from aluminium and of a thickness of 1.5 mm, (ii) two electrode plates (cl; c2) made of non- conductive polymethylmethacrylate (PMMA)) with cutouts defining the geometry of the fixed bed chamber (cl.3; c2.3) and the inlet (cl. l; c2.1) and outlet (cl.2; c2.2) channels for the electrolyte solution as described in Example 1, (iii) a set of elastomeric polyolefin or silicone sealing layers (bl;b2) and (dl;d2) located from each side of the electrode plate (cl; c2), the sealing layers being provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber (cl .3 ; c2.3) with the respective current collectors (al ; a2) and with the membrane layer (el ), wherein the membrane layer (el) is a functional membrane. In this embodiment, the functional membrane was a cation-exchange membrane. The electrode plates (cl; c2) for inserting the nanostructured materials are as described in Example 1. The cutouts in electrode plates are called nanomaterial chambers (cl.3; c2.3) and are be designed to have characteristic volumes from a few microliters up to several milliliters. Even larger volumes up to tens of milliliters are possible if an internal supporting division is included. The internal division can be realized as a grid made of porous material, enabling the flow of the electrolyte. Their volume defines the amount of nanostructured materials needed. In this specific embodiment, the volume of the nanomaterial chambers (cl.3; c2.3) was 2.25 cm3. The inlet (cl.l; c2.1) and outlet (cl.2; c2.2) channels are directly connected to these nanomaterial chambers (cl.3; c2.3). Their entrance and exit are provided with a specifically designed space for placing a filter (cl.4. a; c2.4.a; cl.4.b; c2.4.b), such as filtration fabric. The space tightly accommodates the filter and renders it mechanically immovable. The filtration fabric employed for this purpose was 100 % polyethylene terephthalate (PET) with the brand name FINET PES 3 obtained from MITOP. The filters anchor the electrically-conductive nanomaterial in the nanomaterial chamber (cl.3; c2.3) and prevent it from being washed out when an electrolyte flow through the nanomaterial chambers (cl.3; c2.3) is applied. The thickness of the sealing layers (bl; dl; b2; d2) was 0.5 mm, and the thickness of the membrane layer (el) was 0.3 mm.
The assembly of such an electrochemical system proceeds in the following way. The current collectors (al; a2) are provided with a sealing layer (bl; b2) that contains cutouts for contacting the fixed bed of electrically-conductive nanomaterial in the chambers (cl.3; c2.3). The electrode plates (cl; c2) are placed on these sealing layers (bl ; b2), and the filters (cl ,4.a; c2.4.a; cl ,4.b; c2.4.b), such as filtration fabric of a specific size, are inserted into the respective spots at the entrance of the inlet and outlet channels (cl. l; c2.1; cl.2; c2.2) into the chamber (cl.3; c2.3). The nanomaterial chambers (cl.3; c2.3) are then filled with the electrically-conductive nanomaterial, preferably selected from the group comprising carbon nanotubes, tubes of conductive polymers, etc. as defined above. In this specific embodiment, the chambers (cl.3; c2.3) were filled with multiwall carbon nanotubes. Before inserting the nanostructured material in the designated chambers (cl.3; c2.3), we preferably soak the nanomaterial in a working electrolyte solution for at least 24 hours. Soaking the material in the working solution ensures its good wettability, and it allows one to work with the material as with clay after removing the solution excess. Next, another sealing material layer (dl; d2) was placed on top of the electrode plates (cl; c2). The contact of the electrically-conductive nanomaterial and the current collectors (al; a2), which is crucial for the flawless operation of the system, is provided by the compressive force applied to the nanostructured bed when assembling the system. To develop a sufficient compressive force, we follow one of the three strategies: (i) the volume of the used electrically-conductive nanomaterial is larger by approximately 10 % than the volume of the chamber (cl.3; c2.3), (ii) a thin layer of a porous and compressible material (such as felt) is placed on the top of the bed before the system assembly, or (iii) the electrode plates (cl; c2) are made of a compressible material, for example, Engineering LCD Series Flex 63A Resin Clear. Any compressible electrically non-conductive material in which the required structures can be made can be used. A functional membrane layer (el) separating a catholyte from an anolyte is placed between the two prepared electrode plate sandwiches, and the whole system is pressed together in a vice. Such a system can be primed with the working solution by using a peristaltic pump. An example of a filled nanomaterial chamber is depicted in Figure 3.
The developed flow-through electrode assembly having a multilayered structure with 3D electrodes made of nanostructured materials was tested as a vanadium redox flow battery. The testing experiment proceeded in the following way. 20 mg of multiwall carbon nanotubes were weighted out and moistured for 24 hours in the working electrolyte vanadium solution containing 1.6 M vanadium (an equimolar mixture of vanadium in oxidation states III and IV), 2M sulfuric acid, and 0.3% H3PO4. The current collectors (al; a2), sealing layers (bl; b2), and electrode plates (cl; c2) were stacked, and a filtration fabric MITOP FINET PES 3 was placed at the designated positions of filters (cl .4. a; c2.4.a; cl ,4.b; c2.4.b) located at the entrance of the inlet (cl .1 ; c2.1) and outlet (c2.1 ; c2.2) channels into the chamber (cl.3; c2.3) of each electrode plate (cl; c2). The moist multiwall carbon nanotubes were then transferee! into the nanomaterial chambers (cl.3; c2.3). The electrodes plates (cl; c2) were provided with a sealing layer (dl; d2) made from an elastomeric polyolefin, and a cation-exchange membrane was placed between these sealings. The whole system was firmly stacked together in a vice. The inlet channels (el.l; c2.1) were connected to a peristaltic pump, and the current collectors (al; a2) were connected with leads to a potentiostat. A peristaltic pump provided the flow of catholyte and anolyte electrolytes stored in a flask under a nitrogen atmosphere. The electrolyte was charged to 50 % of its theoretical capacity under an applied current of 100 mA. The charging of 5 ml of the vanadium solution took 7719 s. Discharging and charging load characteristics were measured at the electrolyte volumetric flow rates of 100, 300, and 500 pl/min with the applied discharging and charging current densities ranging from 15 to 95 mA/cm2. These volumetric flow rates correspond to the linear velocities of 0.2, 0.6, and 1 cm/min. The results of the conducted study are plotted in Figure 4 in the form of polarization curves.
Example 3 : A two-electrode system with a pair of membranes separating the electrodes from the main channel
A schematic of the multilayered flow-through electrode assembly with a pair of membranes separating the main channel from the electrodes was used (see Figure 5) for capacitive electrodialysis. The fixed bed of electrically-conductive nanomaterial was used for this purpose, i.e., these 3D electrodes temporarily stored ionic species when the system was polarized in the DC electric field. The processed solution was separated from the electrode plates (cl; c2) with a pair of selective (ion-exchange) membranes (el.l; el.2) of thickness of 0.3 mm, displaying the selectivity towards the (ionic) components of the processed electrolyte solution. The membranes (el.l; el.2) were separated by a middle plate (gl), made from polycarbonate (PC) and having thickness of 1 mm, and containing an inlet (gl.l) for a solution to be processed, an outlet (gl.2) for the processed solution, and a cutout (gl.3) for enabling direct contact of the solution to be processed with the first and second selective membranes (el.l; el.2).
The ionic components migrate from the processed solution through the corresponding first and second membranes (el.l; el.2) to the electrodes made of nanostructured material, on which they create an electric double layer. This process can be likened to battery charging. The chambers (cl.3; c2.3) with the fixed bed of the nanomaterial were filled with the electrolyte solution before starting the experiment. This solution was stagnant in the nanomaterial chambers (cl.3; c2.3) during the experiment. The remaining features of the assembly were as described in Examples 1 and 2.
The flow-through electrode assembly thus comprises (i) two current collectors (al; a2); (ii) two electrode plates (cl; c2) having the chambers (cl.3; c2.3) for placing the nanostructured material with auxiliary fluidic input (el.l; c2.1) and output (cl.2; c2.2) channels, and a set of sealing layers on the top and bottom (bl; b2 and dl; d2); (iii) two membranes, e.g., cation- and anion-exchange membrane (el.l; el.2); and (iv) a middle plate (gl) with an inlet (gl.l) and an outlet (gl.2) to conduct the processed solution through the system. The assembly of the system follows the same protocol as described in Example 2.
The testing experiment for this system proceeded in the following way. The chambers were filled with moist multiwall carbon nanotubes in the amount of 5 grams given by the dimensions of the nanomaterial chamber with a bottom area of 4.5 cm2 and a height of 0.5 cm. The inlet (cl.4. a; c2.4.a) and outlet (cl.4.b; c2.4.b) channels of the electrode plates (cl; c2) were equipped with the filtration fabric MITOP FINET PES 3. The electrode plates were aligned with sealing layers (dl; d2) made of elastomeric copolymer, followed by an anion- and cation-exchange membrane (el.l; el.2) on either electrode. The middle plate (gl) having the channels for the processed solution was placed between the ion-exchange membranes covered by sealing layers (fl ; f2) made from an elastomeric copolymer. The nanomaterial chambers (cl.3; c2.3) were primed with deionized water, and the current collectors (al; a2) were connected with leads to a potentiostat. The model electrolyte solution mimicking partially desalted seawater was sodium chloride at a concentration of 0.01 M. Its volumetric flow rate was set to 100 pl/min, and its desalination occurred at constant electric current loads ranging from 0.15 to 1.5 mA. At the highest current, the desalination reached almost 100 % as evaluated from measuring the solution electrolytic conductivities at the system inlet (gl. l) and outlet (gl.2). Figure 6 depicts experimentally determined desalination as a function of the applied electric currents (dots) and its comparison to theoretical predictions (line with dots). The theoretical predictions are based on the assumption that Na+ and CF ions exclusively carry the electric current.

Claims

1. A flow-through electrode assembly having a multilayered structure, comprising in the following order:
- a first current collector (al) suitable for being connected to a power supply;
- a first electrode plate (cl);
- a membrane layer (el) for separating electrode plates;
- a second electrode plate (c2);
- a second current collector (a2) suitable for being connected to a power supply; wherein the first and second electrode plates (cl; c2) contain a layer from an electrically non-conductive material, comprising a chamber (cl.3; c2.3) for electrically-conductive nanomaterial; an inlet channel (cl .1 ; c2.1 ) for conducting an electrolyte solution from the stock of electrolyte solution to the chamber (cl.3; c2.3); an outlet channel (cl.2; c2.2) for conducting the electrolyte solution from the chamber (cl.3; c2.3) to the stock of electrolyte solution; and electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) adapted for being exposed to the electrolyte solution; wherein the electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) is in direct contact with the first or second current collector (al;a2) and with the membrane layer (el); and wherein the membrane layer (el) comprises a membrane selected from the group comprising an ion-exchange membrane, dialysis membrane, ultrafiltration membrane, reverse osmosis membrane, nanofiltration membrane.
2. The flow- through electrode assembly, according to claim 1, characterized in that the electrically- conductive nanomaterial is selected from the group comprising nanostructured carbon-based materials, such as carbon nanotubes, carboxylic acid functionalized carbon nanotubes, octadecylamine functionalized carbon nanotubes, poly(ethylene glycol) functionalized carbon nanotubes, amide functionalized carbon nanotubes, polyaminobenzene sulfonic acid functionalized carbon nanotubes or graphene oxide, ammonia functionalized graphene oxide, reduced graphene oxide or polypyrrole of preferably from 40 to 60 monomeric units, polyethylene- carbon filled.
3. The flow- through electrode assembly, according to claim 1 or 2, characterized in that it further comprises a filter (cl.4.a; cl.4.b; c2.4.a; c2.4.b) located at the entrance of the inlet (cl.l; c2.1) and outlet (cl.2; c2.2) channels into the chamber (cl.3; c2.3), preferably the filter is selected from the group comprising polyethylene terephthalate, polyethylene, polypropylene, graphite felt.
4. The flow-through electrode assembly, according to any one of the preceding claims 1 to 3, characterized in that the volume of the chamber (cl.3; c2.3) is in the range of from 1 pl to 100 ml.
5. The flow- through electrode assembly, according to any one of the preceding claims 1 to 4, characterized in that it further comprises a sealing layer (bl, b2) located between the first current collector (al) and the first electrode plate (cl) and/or between the second current collector (a2) and the second electrode plate (c2), respectively; wherein the sealing layer (bl; b2) is provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) with the respective current collector (al; a2).
6. The flow-through electrode assembly according to any one of the preceding claims 1 to 5, characterized in that it further comprises a sealing layer (dl ; d2) located between the first electrode plate (cl) and the membrane layer (el); and/or between the second electrode plate (c2) and the membrane layer (el); wherein the sealing layer (dl; d2) is provided with an aperture for contacting electrically-conductive nanomaterial localized in the chamber (cl.3; c2.3) with the membrane layer (el).
7. The flow-through electrode assembly, according to any one of the preceding claims 1 to 6, characterized in that it further comprises a peristaltic pump for enabling the flow of the electrolyte solution from the stock of electrolyte solution to the chamber (cl.3; c2.3).
8. The flow- through electrode assembly, according to any one of the preceding claims 1 to 7, characterized in that the membrane layer (el) for separating electrode plates contains in the following order a first selective membrane (el.l), a middle plate (gl) and a second selective membrane (el.2), wherein - the first selective membrane (el .1) is in direct contact with the electrically-conductive nanomaterial localized in the first electrode plate (cl);
- the second selective membrane (el.2) is in direct contact with the electrically-conductive nanomaterial localized in the second electrode plate (c2);
- the middle plate (gl) contains an inlet (gl.l) for a solution to be processed, an outlet (gl.2) for the processed solution, and a cutout (gl .3) for enabling direct contact of the solution to be processed with the first and second selective membranes (el.1; el.2).
9. The flow-through electrode assembly, according to claim 8, characterized in that the selective membranes (el.l; el.2) are ion-exchange membranes.
10. The flow-through electrode assembly, according to claims 8 or 9, characterized in that it comprises two sealing layers (fl; f2) located within the membrane layer (el); one sealing layer (fl) located between the first selective membrane (el.l) and the middle plate (gl); and the second sealing layer (f2) located between the second selective membrane (cl.2) and the middle plate (gl); wherein the sealing layers (fl ; f2) are provided with an aperture for contacting the solution to be processed with the respective selective membrane (el.l; el.2).
11. The flow-through electrode assembly, according to claims 8, 9, or 10, characterized in that it further comprises a peristaltic pump for enabling the flow of the solution to be processed via the inlet (gl.l) through the cutout (g 1.3) to the outlet (gl.2).
12. A set of at least two flow-through electrode assemblies according to any one of the preceding claims 1 to 11, wherein the flow- through electrode assemblies are serially connected using a bipolar configuration.
13. Use of the flow-through electrode assembly having a multilayered structure according to any one of the preceding claims 1 to 11 or of the set according to claim 12 in electrochemical reactors, redox flow batteries, capacitor batteries, electro(membrane) separation systems, capacitive deionization and/or as electrochemical sensors.
PCT/CZ2022/050036 2022-04-04 2022-04-04 Flow-through electrode assembly having a multilayered structure and use thereof WO2023193836A1 (en)

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