EP4055211A1 - Systèmes catalyseur-ionomère et procédés d'électrolyse en phase gazeuse - Google Patents

Systèmes catalyseur-ionomère et procédés d'électrolyse en phase gazeuse

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Publication number
EP4055211A1
EP4055211A1 EP20800640.3A EP20800640A EP4055211A1 EP 4055211 A1 EP4055211 A1 EP 4055211A1 EP 20800640 A EP20800640 A EP 20800640A EP 4055211 A1 EP4055211 A1 EP 4055211A1
Authority
EP
European Patent Office
Prior art keywords
ion
catalyst
conducting polymer
gas
catalyst system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20800640.3A
Other languages
German (de)
English (en)
Inventor
Francisco Pelayo GARCÍA DE ARQUER
Cao-Thang DINH
Adnan OZDEN
Joshua WICKS
David Sinton
Edward Sargent
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Toronto
TotalEnergies Onetech SAS
Original Assignee
University of Toronto
TotalEnergies Onetech SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Toronto, TotalEnergies Onetech SAS filed Critical University of Toronto
Publication of EP4055211A1 publication Critical patent/EP4055211A1/fr
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • C25B11/089—Alloys
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/23—Carbon monoxide or syngas
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C25B11/032—Gas diffusion electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material
    • C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded

Definitions

  • the technical field generally relates to catalytic methods for gas-phase electrolysis, for example in order to upgrade greenhouse gases such as CO 2 to valuable fuels and feedstocks.
  • the technical field more particularly relates to catalyst-ionomer systems for enhancing such electrolysis processes.
  • Gas-phase electrolysis offers an attractive route to upgrade greenhouse gases such as CO 2 to valuable fuels and feedstocks.
  • greenhouse gases such as CO 2
  • today it is curtailed at least in part by the limits of gas diffusion through the liquid electrolyte to the surface of the catalyst. This can tend to shrink the volume over which coexists the desired combination of gas reactants, catalyst active sites, and electrolyte ions.
  • Operating CO 2 electrolysis processes at elevated current densities has also been challenging.
  • the present disclosure provides a catalyst system for gas-phase electrolysis of a reactant gas to form a product in an aqueous medium, the catalyst system being remarkable in that it comprises a catalytic material being or comprising a catalytic metal and/or carbon; and one or more ion-conducting polymer layers provided on the catalytic material and comprising an ion-conducting polymer that includes hydrophilic and hydrophobic groups, and in that the one or more ion-conducting polymer layers have a thickness of about 2 nm to about 50 nm measured by transmission-electron microscopy.
  • the one or more ion-conducting polymer layers have a thickness of at least about 3 nm measured by transmission-electron microscopy, preferably of at least about 5 nm, more preferably of at least about 7 nm; even more preferably of at least about 9 nm; and most preferably of at least about 10 nm.
  • the one or more ion-conducting polymer layers have a thickness of at most about 48 nm measured by transmission-electron microscopy, preferably of at most about 45 nm, more preferably of at most about 40 nm; even more preferably of at most about 35 nm; and most preferably of at most about 30 nm.
  • the one or more ion-conducting polymer layers have a thickness of about 5 nm to about 45 nm measured by transmission-electron microscopy, preferably of about 5 nm to about 40 nm; more preferably of about 7 nm to about 40 nm, even more preferably of about 10 nm to about 30 nm.
  • the one or more ion-conducting polymer layers have a morphology with separate hydrophilic and hydrophobic domains that form differentiated gas and ion transport routes.
  • the catalytic material is or comprises a catalytic metal.
  • the catalytic metal comprises one or more selected from Cu, Ag, Pd, Pt, Pd doped with Ag or Pt doped with Ag.
  • the catalytic metal comprises Cu.
  • the catalytic metal comprises Ag.
  • the catalytic metal comprises Pd; with preference, the catalytic metal comprises Pd and is doped with Ag.
  • the catalytic metal comprises Pt; with preference, the catalytic metal comprises Pt and is doped with Ag.
  • the catalytic material comprises C.
  • the catalytic material comprises Bi, Al, Sn, Pb, Au, Cf, Ru, Rh, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Zn, Cd, Hg, Ge, Si or any combination thereof.
  • the catalytic material is doped with a dopant comprising an oxide, a halide, a telluride, a chalcogenide, a hydroxide, an oxyhydroxide, a nitrate, or a silicide, or a combination thereof.
  • a dopant comprising an oxide, a halide, a telluride, a chalcogenide, a hydroxide, an oxyhydroxide, a nitrate, or a silicide, or a combination thereof.
  • the catalytic material is provided as a deposited layer on a gas- diffusion membrane, or the catalytic material is or is comprised in a layer deposited on a gas-diffusion membrane.
  • the gas-diffusion membrane is a gas-diffusion electrode (GDE) or an ion-transport membrane or a micro-structured metal or a nano-structured metal.
  • the gas-diffusion membrane is a hydrophobic porous support -
  • the gas-diffusion membrane is electrically conductive.
  • the gas-diffusion membrane is composed of porous carbon and/or polytetrafluoroethylene (PTFE).
  • porous carbon is selected among carbon fibers and/or carbon cloth.
  • the catalytic material is provided in the form of particles and corresponding ion-conducting polymer layers are provided around respective particles, thereby providing a plurality of catalyst-polymer particles.
  • the catalyst- polymer particles are nanoparticles and/or the catalyst-polymer particles are nanoparticles with an average diameter ranging from 2 nm to 200 nm as measured by transmission electron microscopy, more preferably from 5 nm to 150 nm, even more preferably from 7 nm to 100 nm, most preferably from 10 nm to 50 nm.
  • the catalytic material is provided as a porous metal layer, preferably disposed on a gas-diffusion membrane, and the one or more ion-conducting polymer layers are disposed thereon to form a catalyst-ionomer planar heterojunction (CIPH).
  • CIPH catalyst-ionomer planar heterojunction
  • the CIPH has a thickness ranging from 12 to 550 nm measured by scanning electron microscopy, preferably ranging from 15 nm to 400 nm, more preferably from 20 nm to 300 nm.
  • the catalytic material is provided as a porous metal layer, preferably disposed on a gas-diffusion membrane, and the one or more ion-conducting polymer layers are disposed thereon to form a catalyst-ionomer planar heterojunction (CIPH) and the porous metal layer has a thickness ranging from 10 to 500 nm measured by scanning electron microscopy, preferably ranging from 15 nm to 400 nm .preferably ranging from 20 nm to 300 nm.
  • CIPH catalyst-ionomer planar heterojunction
  • the catalytic material is provided as a porous metal layer, preferably disposed on a gas-diffusion membrane, and the one or more ion-conducting polymer layers are disposed thereon to form a catalyst-ionomer planar heterojunction (CIPH) and the one or more ion conducting polymer layers have a thickness ranging from 2 to 50 nm measured by scanning electron microscopy, preferably ranging from 5 nm to 40 nm .preferably ranging from 10 nm to 20 nm..
  • CIPH catalyst-ionomer planar heterojunction
  • One or more of the following features can be advantageously used to further define the one or more ion-conducting polymer layers: - The one or more ion-conducting polymer layers are homogeneous over the catalyst material.
  • the one or more ion-conducting polymer layers are conformal over the catalyst material.
  • the one or more ion-conducting polymer layers have a thickness that is between 2 and 4 repeat units, the units being the distance between hydrophilic and hydrophobic domains.
  • the one or more ion-conducting polymer layers have a thickness that is above 2 nm and up to a diffusion length of the reactant gas.
  • the one or more ion-conducting polymer layers comprise a ion-conducting polymer, and a residual polar solvent from application thereof onto the catalyst material.
  • the ion-conducting polymer comprises an ionomer or a combination of different ionomers.
  • the ionomer comprises a backbone that comprises the hydrophobic groups and side chains that comprise the hydrophilic groups; and/or the ionomer comprises a perfluorinated sulfonic acid ionomer.
  • said perfluorinated sulfonic acid ionomer comprises sulfonated tetrafluoroethylene based fluoropolymer-copolymer (such as Nafion® or 1 ,1 ,2,2- Tetrafluoroethene;1 ,1 ,2,2-tetrafluoro-2-[1 ,1 ,1 ,2,3,3-hexafluoro-3-(1 ,2,2- trifluoroethenoxy)propan-2-yl]oxyethanesulfonic acid) , SSC, Aciplex, Flemion, 3M- perfluorinated sulfonic acid ionomer, Aquivion, an ionene, or a combination thereof.
  • sulfonated tetrafluoroethylene based fluoropolymer-copolymer such as Nafion® or 1 ,1 ,2,2- Tetrafluoroethene;1 ,1 ,
  • the ion-conducting polymer is spray-coated directly onto an outer surface of the catalytic material to form the one or more ion-conducting polymer layers.
  • the catalyst system comprises a catalyst-ionomer bulk heterojunction (CIBH) that comprises a plurality of catalyst-ionomer particles; with preference, one or more of the following features can preferably define said catalyst-ionomer bulk heterojunction:
  • the catalyst-ionomer bulk heterojunction (CIBH) is disposed on a gas-diffusion membrane; with preference, the catalyst-ionomer bulk heterojunction is spray-coated on a gas-diffusion membrane.
  • the catalyst-ionomer bulk heterojunction (CIBH) is disposed on a catalyst material layer.
  • the catalyst-ionomer bulk heterojunction (CIBH) is disposed on a catalyst-ionomer layer or on a catalyst-ionomer planar heterojunction (CIPH).
  • the catalyst-ionomer bulk heterojunction has a CIBH thickness ranging between 50.0 nm to 25.0 ⁇ m as determined by scanning electron microscopy; preferably between 60.0 nm and 24.0 ⁇ m, more preferably between 70.0 nm and 23.0 ⁇ m, more preferably between 100.0 nm and 20.0 ⁇ m.
  • the catalyst-ionomer bulk heterojunction has a CIBH thickness of at least 50.0 nm as determined by scanning electron microscopy, preferably of at least 70.0 nm, more preferably of at least 100.0 nm, even more preferably of at least 500.0 nm, most preferably of at least 1.0 ⁇ m.
  • the catalyst-ionomer bulk heterojunction has a CIBH thickness of at most 25.0 ⁇ m as determined by scanning electron microscopy, preferably at most 20.0 ⁇ m, more preferably at most 15.0 ⁇ m, even more preferably at most 10.0 ⁇ m, most preferably at most 6.0 ⁇ m.
  • the catalyst-ionomer bulk heterojunction has a ratio of catalyst material to ion-conducting polymer ranging from 0.1 to 10.0, preferentially ranging from 0.2 to 9.0, more preferentially ranging from 0.3 to 8.0, even more preferentially ranging from 0.4 to 7.0, most preferentially ranging from 0.5 to 5.0 or ranging from 0.5: to 2.0, even most preferentially ranging from 0.6 to 2.0 or from 1.0 to 1.6.
  • the catalyst-ionomer bulk heterojunction is applied onto a substrate that include a gas- diffusion membrane and a planar heterojunction that includes catalyst material and a planar layer of the ion-conducting polymer.
  • the hydrophobic groups comprise halogenated groups.
  • said halogenated groups comprise fluorinated groups, more preferably said fluorinated groups comprise CF 2 groups.
  • the hydrophilic groups comprise sulfonic acid groups.
  • the one or more ion-conducting polymer layers are one or more spray-coated layers or one or more coated layers formed by the ion-conducting polymer directly onto an outer surface of the catalytic material.
  • the catalytic material is a CO 2 reduction reaction catalyst or a CO reduction reaction catalyst.
  • the catalytic material is in the form of a plurality of particles and at least one on-conducting polymer layer is provided around the catalytic material particles, thereby providing a plurality of catalyst-polymer particles; with preference the plurality of catalyst-polymer particles forms a catalyst-ionomer bulk heterojunction (CIBH).
  • the catalyst-polymer particles are electrically conductive.
  • the catalyst system comprises a catalyst-ionomer bulk heterojunction (CIBH) and the CIBH is disposed on a gas-diffusion membrane.
  • CIBH catalyst-ionomer bulk heterojunction
  • a part of said catalytic material is in the form of a layer and said catalyst system comprises a catalyst-ionomer bulk heterojunction (CIBH) disposed on the catalytic material layer; with preference the catalytic material layer is disposed on a gas- diffusion membrane.
  • CIBH catalyst-ionomer bulk heterojunction
  • the catalyst system comprises at least two ion-conducting polymer layers wherein at least one ion-conducting polymer layer is comprised in the catalyst- ionomer bulk heterojunction (CIBH) and in that the CIBH is disposed on an ion-conducting polymer layer; with preference the ion-conducting polymer layer on which the CIBH is disposed is itself disposed on a gas-diffusion membrane.
  • CIBH catalyst- ionomer bulk heterojunction
  • a part of said catalytic material is in the form of a layer
  • the catalyst system comprises at least two ion-conducting polymer layers wherein at least one conducting polymer layer is comprised in the catalyst-ionomer bulk heterojunction (CIBH) and an ion-conducting polymer layer is disposed between a catalyst-ionomer bulk heterojunction (CIBH) and the catalytic material layer; with preference, the catalytic material layer is disposed on a gas-diffusion membrane.
  • the catalyst system comprises a catalyst-ionomer bulk heterojunction (CIBH) and the ion-conducting polymer comprises a perfluorinated sulfonic acid ionomer.
  • the present disclosure provides a method of manufacturing a catalyst system for gas-phase electrolysis of reactant gas to produce a product in an aqueous medium preferably according to the first aspect, the method being remarkable in that it comprises the following steps: a) providing a catalytic material being or comprising a catalytic metal and/or carbon; and b) disposing an ion-conducting polymer onto an outer surface of the catalytic material to form one or more ion-conducting polymer layers thereon, wherein the ion-conducting polymer comprises hydrophobic and hydrophilic domains and wherein the one or more ion-conducting polymer layers have a thickness of about 2 nm to about 50 nm measured by transmission-electron
  • one ion-conducting polymer layer is an ion-conducting polymer layer provided on the catalytic material and comprising an ion-conducting polymer that includes hydrophilic and hydrophobic groups, wherein the ion-conducting polymer layer has a morphology with separate hydrophilic and hydrophobic domains that form differentiated gas and ion transport routes.
  • the one or more ion-conducting polymer layers have a thickness of about 5 nm to about 45 nm measured by transmission-electron microscopy, preferably of about 7 nm to about 40 nm, more preferably of about 10 nm to about 30 nm.
  • the ion-conducting polymer comprises hydrophobic and hydrophilic domains and assembles to provide a morphology with separate hydrophilic and hydrophobic domains that provide differentiated gas and ion transport routes.
  • disposing an ion-conducting polymer onto an outer surface of the catalytic material comprises spray-coating.
  • the step of disposing an ion-conducting polymer onto an outer surface of the catalytic material further comprises providing an ion-conducting polymer liquid comprising the ion-conducting polymer and a solvent, and disposing the ion-conducting polymer liquid onto the catalytic material, and optionally drying to evaporate the solvent and form the one or more ion-conducting polymer layers.
  • the step of drying is performed at ambient temperature and vacuum conditions or for at least 12 hours, preferably for at least 15 hours.
  • the solvent is a polar solvent.
  • the polar solvent is or comprises an alcohol or the polar solvent is or comprises methanol and/or isopropyl alcohol.
  • the present disclosure provides a method of manufacturing a catalyst system for gas-phase electrolysis of reactant gas to produce a product in an aqueous medium, the method is remarkable in that it comprises the following steps: providing a catalytic material being or comprising a catalytic metal and/or carbon; wherein at least a part of the catalytic material is in the form of a plurality of particles; and providing an ion-conducting polymer, wherein the ion-conducting polymer comprises hydrophobic and hydrophilic domains; contacting the plurality of catalytic material particles with the ion-conducting polymer, and at least one solvent; to dispose the ion-conducting polymer around the plurality of catalytic material particles, and to form a mixture comprising a plurality of catalyst-polymer particles; preferably the solvent is a polar solvent; and disposing the mixture onto a substrate to form thereon a catalyst-ionomer bulk heterojunction (CIBH)
  • CIBH catalyst-ionomer
  • the catalyst-polymer particles are nanoparticles or the catalyst-polymer particles are nanoparticles with an average diameter ranging between 2 and 200 nm as measured by transmission electron microscopy, more preferably between 5 nm and 150 nm, even more preferably between 7 nm and 100 nm, most preferably between 10 nm and 50 nm.
  • the substrate is one selected from a gas diffusion membrane; a layer of catalytic material; a layer of ion-conducting polymer; or a layer of ion-conducting polymer disposed on a layer of catalytic material.
  • the present disclosure provides a process for electrochemical production of a product from a reactant gas, said process being remarkable in that it comprises the following steps: contacting reactant gas and an electrolyte with an electrode comprising the catalyst system as defined in accordance with the first aspect or as made by the method as defined in accordance with the second aspect, such that the reactant gas contacts the catalyst material of the catalyst system; applying a voltage to provide a current density to cause the reactant gas contacting the catalyst material to be electrochemically converted into the product; and recovering the product.
  • the electrolyte comprises an alkaline compound.
  • said alkaline compound comprises a potassium compound which is advantageously KOH.
  • the current density is at least 0.5 A ⁇ cm -2 as measured by electrochemical potentiostat stations, preferably at least 0.6 A ⁇ cm -2 , more preferably at least 0.7 A ⁇ cm -2 , even more preferably at least 0.8 A ⁇ cm -2 , most preferably at least 0.9 A ⁇ cm -2 , even most preferably at least 1.0 A cm -2 .
  • the reactant gas is one or more selected of CO, CO 2 , O 2 , N 2 , C 2 H 4 , NOx, CH 4 , or H 2 .
  • the reactant gas is CO 2 and/or CO; and the product is at least one multi-carbon product produced by electroreduction.
  • the reactant gas is CO and/or CO 2 ; and the catalytic material is a C02RR catalyst or a CORR catalyst for electroreduction of the reactant gas to produce multi-carbon compounds.
  • the present disclosure provides a use of the catalyst system as defined in accordance with the first aspect or as made by the method as defined in accordance with the second aspect, in the electrochemical production of at least one multi-carbon compound from a carbon-containing gas or of at least one product from a reactant gas.
  • the present disclosure provides a system for electroreduction to produce a product from a reactant gas, comprising: an electrolytic cell configured to receive a liquid electrolyte and reactant gas; an anode; and a cathode comprising a catalyst system as defined in accordance with the first aspect or as made by the method as defined in accordance with the second aspect.
  • a catalyst system for gas- phase electrolysis of a reactant gas to form a product in an aqueous medium.
  • the catalyst system comprises a catalytic material; an ion-conducting polymer layer provided on the catalytic material and comprising an ion-conducting polymer that includes hydrophilic and hydrophobic groups, wherein the ion-conducting polymer layer has a morphology with separate hydrophilic and hydrophobic domains that form differentiated gas and ion transport routes.
  • the catalytic material is a catalytic metal.
  • the catalytic metal comprises Cu.
  • the catalytic metal comprises Ag.
  • the catalytic metal comprises Pd.
  • the catalytic metal comprises Pt.
  • the catalyst metal is doped with Ag.
  • the catalyst material comprises C.
  • the catalyst material comprises Bi, Al, Sn, Pb, Au, Cf, Ru, Rh, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Zn, Cd, Hg, C, Ge, or Si or their combinations.
  • the catalyst material is doped with a dopant.
  • the dopant comprises an oxide, a halide, a telluride, a chalcogenide, a hydroxide, an oxyhydroxide, a nitrate, or a silicide, or a combination thereof.
  • the ion-conducting polymer layer is homogeneous over the catalyst material.
  • the ion-conducting polymer layer is conformal over the catalyst material.
  • the ion-conducting polymer comprises an ionomer.
  • the ionomer comprises a backbone that comprises the hydrophobic groups and side chains that comprise the hydrophilic groups.
  • the hydrophobic groups comprise halogenated groups.
  • the halogenated groups comprise fluorinated groups.
  • the fluorinated groups comprise CF 2 groups.
  • the hydrophilic groups comprise sulfonic acid groups.
  • the ion-conducting polymer comprises a perfluorinated sulfonic acid ionomer.
  • the perfluorinated sulfonic acid ionomer comprises Nafion (commercial name of perfluoro(2-(2-sulfonylethoxy)propyl vinyl ether)- tetrafluoroethylene copolymer).
  • the perfluorinated sulfonic acid ionomer comprises SSC.
  • the perfluorinated sulfonic acid ionomer comprises Aciplex, Flemion, 3M-perfluorinated sulfonic acid ionomer, Aquivion, Nafion, SSC, or a combination thereof.
  • the ion-conducting polymer comprises an ionene.
  • the ion-conducting polymer layer has a thickness of about 2 nm to about 50 nm measured by transmission-electron microscopy.
  • the ion-conducting polymer layer has a thickness of about 5 nm to about 40 nm measured by transmission-electron microscopy.
  • the ion-conducting polymer layer has a thickness of about 10 nm to about 30 nm measured by transmission-electron microscopy.
  • the ion-conducting polymer layer has a thickness that is between 2 and 4 repeat units, the units being the distance between hydrophilic and hydrophobic domains.
  • the ion-conducting polymer layer has a thickness that is between 2 and 3 repeat units.
  • the ion-conducting polymer layer has a thickness that is above 2 nm and up to a diffusion length of the reactant gas.
  • the catalytic material is provided as a deposited layer on a gas-diffusion membrane.
  • the gas-diffusion membrane is composed of porous carbon or polytetrafluoroethylene (PTFE).
  • the ion-conducting polymer is spray-coated directly onto an outer surface of the catalytic material to form the ion-conducting polymer layer.
  • the catalytic material is provided in the form of particles and corresponding ion-conducting polymer layers are provided around respective particles, thereby providing a plurality of catalyst-polymer particles.
  • the particles are nanoparticles.
  • the nanoparticles have an average diameter of 5-200 nm or 10-50 nm measured by transmission-electron microscopy and/or scanning electron microscopy.
  • the system comprises a catalyst-ionomer bulk heterojunction (CIBH) that comprises the plurality of catalyst-ionomer particles.
  • CIBH catalyst-ionomer bulk heterojunction
  • the CIBH is disposed on a gas-diffusion membrane or on a catalyst material layer or on a catalyst-ionomer layer.
  • the CIBH is spray-coated onto the gas-diffusion membrane.
  • the CIBH has a CIBH thickness of 50 nm to 25 microns.
  • the CIBH thickness is above 100 nm, above 500 nm or above 1 micron; and wherein the CIBH thickness is below 20 microns, 15, microns, 10 microns or 6 microns.
  • the CIBH has a ratio of catalyst material to ion- conducting polymer of 0.1 :1 to 1:0.1 , or of 1 :2 to 2:1 , or of 1 :1 to 5:3.
  • the catalytic material is provided as a porous metal layer and the ion-conducting polymer layer is disposed thereon to form a catalyst-ionomer planar heterojunction (CIPH).
  • CIPH catalyst-ionomer planar heterojunction
  • the CIPH has a thickness of about 5 to 50 nm.
  • the porous metal layer is disposed on a gas-diffusion membrane.
  • the ion-conducting polymer layer consists of the ion- conducting polymer, and optionally residual polar solvent from application thereof onto the catalyst material.
  • the reactant gas comprises CO 2 , CO, O 2 , ethylene, methane, or hydrogen, or combinations thereof.
  • the reactant gas is CO or CO 2 and the catalytic material is a CO 2 RR catalyst or a CORR catalyst for electroreduction of the reactant gas to produce multi-carbon compounds.
  • a method of manufacturing a catalyst system for gas-phase electrolysis of reactant gas to produce a product in an aqueous medium comprises providing a catalytic material; and disposing an ion-conducting polymer onto an outer surface of the catalytic material to form an ion- conducting polymer layer thereon, wherein the ion-conducting polymer comprises hydrophobic and hydrophilic domains and assembles to provide a morphology with separate hydrophilic and hydrophobic domains that provide differentiated gas and ion transport routes.
  • disposing the ion-conducting polymer onto the catalytic material comprises spray-coating.
  • the method further comprises providing an ion- conducting polymer liquid comprising the ion-conducting polymer and a solvent, and disposing the ion-conducting polymer liquid onto the catalytic material.
  • the solvent is a polar solvent.
  • the method further comprises drying to evaporate the solvent and form the ion-conducting polymer layer.
  • the drying is performed at ambient temperature and vacuum conditions.
  • the drying is performed for at least 12 hours.
  • the polar solvent comprises an alcohol
  • the polar solvent comprises methanol.
  • the polar solvent comprises isopropyl alcohol.
  • the method comprises forming a mixture of particles composed of the catalytic material, the ion-conducting polymer, and at least one solvent; and disposing the mixture onto a substrate to form thereon a bulk heterojunction that comprises the catalyst system.
  • the particles are nanoparticles.
  • the nanoparticles have an average diameter of 5-200 nm or 10-50 nm measured by transmission-electron microscopy.
  • the bulk heterojunction has a CIBH thickness of 50 nm to 25 microns.
  • the thickness of the bulk heterojunction is above 100 nm, above 500 nm or above 1 micron; and wherein the thickness of the bulk heterojunction is below 20 microns, 15 microns, 10 microns or 6 microns.
  • the CIBH thickness of the bulk heterojunction is measured by scanning electron microscopy.
  • the CIBH thickness of the bulk heterojunction is measured by a profilometer.
  • the bulk heterojunction has a ratio of catalyst material to ion-conducting polymer of 0.1 :1 to 1 :0.1, or of 1:2 to 2:1, or of 1:1 to 5:3.
  • the bulk heterojunction is applied onto a substrate that include a gas-diffusion membrane and a planar heterojunction that includes catalyst material and a planar layer of the ion-conducting polymer.
  • the catalyst system comprises one or more features as defined herein.
  • a process for electrochemical production of a product from a reactant gas comprises contacting reactant gas and an electrolyte with an electrode comprising the catalyst system as defined herein or as made by the method as defined herein, such that the reactant gas contacts the catalyst material of the catalyst system; applying a voltage to provide a current density to cause the reactant gas contacting the catalyst material to be electrochemically converted into the product; and recovering the product.
  • the current density is at least 0.5 A ⁇ cm -2 , at least 0.6 A ⁇ cm -2 , at least 0.7 A ⁇ cm -2 , at least 0.8 A ⁇ cm -2 , at least 0.9 A ⁇ cm -2 or at least 1 A ⁇ cm -2 .
  • the current density is measured by electrochemical potentiostat stations.
  • the reactant gas is CO 2 and the product is at least one multi-carbon product produced by electroreduction.
  • the reactant gas is CO and the product is at least one multi-carbon product produced by electroreduction.
  • the reactant gas is O 2 .
  • the reactant gas is N 2 , C 2 H 4 , NOx, CH 4 , or H 2 .
  • the electrolyte comprises an alkaline compound.
  • the alkaline compound comprises a potassium compound.
  • the electrolyte comprises KOH.
  • a system for electroreduction to produce a product from a reactant gas comprises an electrolytic cell configured to receive a liquid electrolyte and reactant gas; an anode; and a cathode comprising a catalyst system as defined herein or as made by the method as defined herein.
  • Fig 1 Techno-economic analysis (TEA) exploring the high-current (1 A/cm 2 ) regime. Dotted line indicates an ethylene production cost of $1000/ton.
  • TAA Techno-economic analysis
  • A Contour plot of the plant-gate levelized cost of ethylene production as a function of current density and electrolyzer energy conversion.
  • B Contour plot of the plant-gate levelized cost of ethylene production as a function of current density and electricity cost. Current densities in excess of 1 A/cm 2 are desired to achieve levelized ethylene costs below $1000/ton
  • Fig. Limiting current in gas-phase electrocatalysis and ionomer gas/liquid decoupled transport channels.
  • A When gas and electrolyte (water and ion source) transport is decoupled, the three-phase reaction interface can be extended so all electrons participate in the desired electrochemical reaction.
  • B Modelled G availability along catalyst’s surface for standard (left) and decoupled (right) gas transport into a 5 M KOH electrolyte assuming an in-plane laminar gas diffusivity of D
  • /D KOH 1000 for the latter. Depending on the gas diffusivity within the gas transport channel, gas availability dramatically increases.
  • C Modelled maximum available current density for CO 2 reduction. D/D KOH manipulation enables entering into the > 1 A ⁇ cm -2 regime for CO 2 R. See methods for details on gas transport and reaction simulations.
  • Fig 3. The catalyst: ionomer planar heterojunction (CIPH).
  • CIPH ionomer planar heterojunction
  • A Schematic of metal catalyst deposited onto a polytetrafluoroethylene (PTFE) hydrophobic fiber support. A flat ionomer layer conformally coats the metal.
  • B Perfluorinated ionomers such as Nafion® exhibit asymmetric hydrophilic and hydrophobic characteristics endowed by SO 3 ' and CF 3 functionalities, respectively. Depending on its assembly, hydrophobic domains could facilitate gas transport, while water/ion can be provided via hydrated hydrophilic surfaces. Laminar Nafion® arrangements have been reported depending on its thickness and substrate (see studies of Burdyny T., et al., ACS Sustain.
  • Fig 4. Increased limiting current and responsible mechanisms for CIPH catalysts for different reactions and materials.
  • ORR Oxygen-reduction-reaction
  • J lim limiting current
  • B For CO 2 RR, standard Ag catalysts yield a J lim ⁇ 54 mA/cm 2 (remaining current employed for hydrogen evolution). This is in stark contrast with CIPH samples, which retain a Faradaic efficiency (FE) above 85% for CO 2 reduction to CO up to ⁇ 500 mA/cm 2 .
  • FE Faradaic efficiency
  • Fig 5. 3D catalyst-ionomer bulk-heterojunction (CIBH) for efficient gas-phase electrochemistry beyond 1 A/cm 2 .
  • A Schematic representation of metal-ionomer bulk- heterojunction catalysts on top of a PTFE support.
  • B Cross-sectional SEM of the BHJ catalyst
  • C TEM of a cryo-microtomed BHJ and
  • D elemental mapping of Cu and C revealing BHJ nanomorphology.
  • E Partial current density for total CO 2 RR reactions, C 2+ and C 2 H 4 at maximum cathodic energy efficiency. The total CO 2 R current saturates at 1.3 A/cm 2 for CIBH thickness beyond 6 ⁇ m.
  • CIBH samples achieve more than a 6-fold increase in partial current density at cathodic energy efficiencies in the > 40% range.
  • F Performance statistics of the highest partial current configuration for 8 different samples.
  • G Performance of best catalyst in an ultraslim flow-cell. A full-cell energy efficiency of 20% for C 2+ products is estimated at 1.1 A/cm 2 operating current.
  • Fig 6. is a Knudsen diffusion schematic of gas interaction with hard cylindrical pore, where d is the pore diameter, and / is the free path.
  • Fig 8. Reacting gas concentration within the ionomer layer for different diffusion coefficients (D) for (A) O 2 and (B) CO 2 .
  • A PTFE/Ag reference and CIPH Ag samples showing the distinctive presence of sulfonate and -CF 2 groups for CIPH.
  • B Raman spectra of hydrated samples. Samples were excited at 738 nm and the signal was collected through air or an immersion 63x objective lens.
  • Fig 10 In situ Raman spectra of Cu CIPH catalysts.
  • the Raman spectrum of CIPH Cu samples shows the distinctive presence of sulfonate and -CF 2 groups, as well as a significant amount of adsorbed CO at 280 and 350 cm -1 - and hence extended CO coverage - in the case of CIPH samples.
  • Samples were operated in a 5 M KOH electrolyte in a custom-made flow cell at -1.6 and -2 V vs Ag/AgCI for reference and CIPH samples respectively. Beyond -1.6 V vs Ag/AgCI, reference samples led to substantial H 2 generation. Samples were excited was 738 nm and the signal collected through immersion 63x objective.
  • Fig 13 Current-voltage characteristics of Ag/PTFE reference and CIPH samples under (A) ORR and (B) HER operation in 5 M KOH electrolyte. N 2 was purged during HER operation. Reference and Ag CIPH samples exhibit a similar HER performance, revealing that the PFSA ionomer layer does not modify water or ion transport. CIPH samples show enhanced ORR current due to increased O 2 availability.
  • Fig 14 Current-voltage characteristics of Ag/PTFE reference and CIPH samples under (A) ORR and (B) HER operation in 1 M KHCO 3 electrolyte. N 2 was purged during HER operation. Reference and Ag CIPH samples exhibit a similar HER performance, revealing that the PFSA ionomer layer does not modify water or ion transport. CIPH samples show enhanced ORR current due to increased O 2 availability.
  • Fig 15. Current-voltage characteristics of Ag/PTFE reference and CIPH samples under (A) ORR and (B) HER operation in 0.5 M H 2 SO 4 electrolyte. N 2 was purged during HER operation. Reference and Ag CIPH samples exhibit a similar HER performance, revealing that the PFSA ionomer layer does not modify water or ion transport. CIPH samples show enhanced ORR current due to increased O 2 availability.
  • Fig 16 Current-voltage characteristics of Ag/PTFE reference and CIPH samples under (A) ORR and (B) HER operation in 0.7 M K 2 SO 4 electrolyte. N 2 was purged during HER operation. Reference and Ag CIPH samples exhibit a similar HER performance, revealing that the PFSA ionomer layer does not modify water or ion transport. CIPH samples show enhanced ORR current due to increased O 2 availability.
  • Fig 17. Product distribution of (A) Ag/PTFE reference and (B) Ag CIPH samples under CO 2 reduction operation at 5 M KOH electrolyte as a function of current density. CIPH samples sustain efficient C 1+ production at much higher productivities.
  • A Faradaic efficiency vs. current density and
  • B current density vs. potential for Ag control samples.
  • C Faradaic efficiency vs. current density and
  • D current density vs. potential for Ag+ionomer (CIPH) samples.
  • Reference samples show a CO 2 to CO limiting current of 110 mA/cm 2 . No limiting current is observed for CIPH samples in this range.
  • A Faradaic efficiency vs. current density and
  • B current density vs. potential for Ag control samples.
  • C Faradaic efficiency vs. current density and
  • D current density vs. potential for Ag+ionomer (CIPH) samples.
  • CIPH samples evidence improved CO 2 mass transport, with J co partial current density increasing from 50 mA/cm 2 to 110 mA/cm 2 .
  • Fig 20 Product distribution of (A) Cu/PTFE reference and (B) Cu CIPH samples under CO 2 reduction operation at 5 M KOH electrolyte as a function of current density. CIPH samples sustain efficient C 2+ production at much higher productivities.
  • Fig 21 (A-D) Scanning electron micrographs of Cu CIPH samples after CO 2 reduction reaction at different magnification. The samples were operated under 5 M KOH at -3 V vs Ag/AgCI for 50 min. The PFSA layer is evident at all magnifications. Cu surface has experience surface reconstruction leading to the formation of smaller grains.
  • Fig 22 Product distribution of (A) Cu/PTFE reference and (B) Cu CIPH samples under CO reduction operation at 5 M KOH electrolyte as a function of current density. CIPH samples sustain efficient C 2+ production at much higher productivities.
  • Fig 23 Characterization of Ag reference and CIPH samples in an h-cell configuration (0.5 M H 2 S0 4 ). Ambient air is bubbled in the catholyte. In this configuration, the ORR limiting current is determined by the gas solubility in the electrolyte. Both samples exhibit a similar ORR limiting current, suggesting that the ionomer does not significantly modify local gas reactant solubility.
  • Fig 24 Characterization of Ag reference and CIPH samples in an h-cell configuration (1 M KHCO 3 ). CO 2 gas is bubbled in the catholyte. In this configuration, the CO 2 R limiting current is determined by the gas solubility in the electrolyte. Current density for (A) Ag reference and (B) Ag CIPH. Both samples exhibit a similar CO 2 limiting current, suggesting that the ionomer does not significantly modify local gas reactant solubility.
  • Fig 25 Partial currents as a function of CO 2
  • Fig 26 C 2+ current density vs EE 1/2 . Partial current density towards C 2 products versus cathodic energy efficiency. Dashed lines represent isosurfaces with constant current ⁇ energy efficiency. CIBH samples achieve more than a 6-fold increase in partial current density at cathodic energy efficiencies in the > 40% range compared to best stable (> 1 h) reported catalyst.
  • Fig 27 Stability of CIBH samples integrated into a membrane-electrode-assembly (MEA) configuration. Current (top) and Faradaic Efficiency towards C 2 H 4 (bottom) and of CIBH samples operated continuously in a 0.1 M KHCO 3 electrolyte at -3.9 V full cell potential.
  • MEA membrane-electrode-assembly
  • Fig 28 CIPH catalyst operation at higher temperature operation.
  • A FE towards ethylene for flat reference and CIPH samples show a shift towards lower voltage for a given selectivity as temperature increases from room temperature (RT) to 60°C. An opposite trend is observed for reference samples.
  • B The corresponding partial current density also increases at similar potential, yielding a better C 2 H 4 productivity at similar energy efficiency. Reference samples show a moderate increase in partial current.
  • Fig 29 CIBH catalyst operation at higher temperature operation.
  • A Potential vs. applied current for CIBH samples at RT and 60°C. Improvements, up to 0.9 V are observed at large currents.
  • Fig. 31 This scheme summarizes three possible arrangements of the catalyst system of the present disclosure.
  • Panel A shows that a catalyst-ionomer bulk heterojunction (CIBH) is disposed on a gas-diffusion membrane which is a gas-diffusion electrode (GDE).
  • B shows that a catalyst-ionomer bulk heterojunction (CIBH) is disposed on a catalyst material layer, itself disposed on a gas-diffusion membrane which is a gas- diffusion electrode (GDE).
  • C shows that a catalyst-ionomer bulk heterojunction (CIBH) is disposed on a catalyst-ionomer planar heterojunction (CIPH), itself disposed on a gas- diffusion membrane which is a gas-diffusion electrode (GDE).
  • Fig 32 This scheme details the arrangement C of the figure 31. A plurality of catalyst-polymer particles is represented. Electron percolation paths are thus created.
  • the catalyst materials include a catalytic metal (e.g., Cu or Ag other others) and an ionomer.
  • the ionomer can be disposed as an ionomer layer provided on the catalytic metal.
  • the present description also relates to systems and methods that use such catalyst materials, also to methods of manufacturing such catalyst materials.
  • the catalyst material includes what can be called a catalyst-ionomer bulk heterojunction (CIBH) that decouples gas, ion and electron transport, and enables thereby CO 2 electrolysis at relatively elevated current densities, e.g., current densities well above 1 A/cm 2 .
  • the CIBH comprises a catalytic metal and a superfine ionomer layer with asymmetric hydrophobic and hydrophilic functionalities that extend gas and ion transport from its range in aqueous solution, which is tens of nanometers, to the micrometer scale. The CIBH simultaneously facilitates that this range overlaps with the location of catalytically active sites.
  • the catalyst system can include a metal catalyst and a polymer or oligomer as in Formula A below, where R is an ion-conductive group leading to ion/water transport domains.
  • the polymer or oligomer can be an ionomer or an ionene, for example.
  • an ionomer is used and can be a perfluorinated sulfonic acid (PFSA) type ionomer.
  • PFSA perfluorinated sulfonic acid
  • the ion-conducting polymers e.g., ionomers
  • the ion-conducting polymers can have one or more properties of the particular ion- conducting polymers mentioned herein, e.g., they can have “m”, “n” or “p” values within ranges that are similar to the above species (e.g., 4.5 to 6.8); they can have “x” and “y” values within the ranges mentioned above; and/or can have one or more other properties of such compounds to form the differentiated gas and ion transport routes that are at least partly defined by hydrophilic and hydrophobic domains in the one or more ion-conducting polymer layers.
  • the side chains of ionomers that can be used may have different lengths, with shorter lengths being potentially preferred in some circumstances.
  • Nafion® i.e. Perfluoro(2-(2- sulfonylethoxy)propyl vinyl ether)-tetrafluoroethylene copolymer
  • SSC ionomers were assessed, and it was demonstrated that performance was enhanced.
  • Other molecules in the PFSA ionomer family are expected to work similarly, and various ion-conducting polymers and oligomers could also be used or adapted depending on the particular catalyst metal, reaction, and operating conditions of interest for a particular application such as electrolyte, pH, and temperature.
  • Other ionomers, such as Fumion or the like, are expected to show similar transport enhancement mechanisms.
  • catalytic materials that were tested and demonstrated include Cu, Ag, Pd and Pt doped Ag, as well as carbon.
  • catalysts for which the demonstrated mechanism can also be applied include Bi, Al, Sn, Pb, Au, Cf, Ru, Rh, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Zn, Cd, Hg, C, Ge, Si, and their combinations, as well as additional dopant species (e.g., oxides, halides, tellurides, chalcogenides, hydroxides, oxyhydroxides, nitrates, silicides).
  • the reactions over which the enhancement was demonstrated include CO 2 reduction reaction (CO 2 RR), CORR, and Oxygen reduction reaction (ORR). It is noted that other reactions for which enhancement is expected include all gas-phase electrolysis reactions, such as Nitrogen reduction reaction (NRR), methane oxidation, ethylene oxidation, hydrogen oxidation and combinations thereof.
  • the reactions can be provided such that a single gas reactant is converted, or such that a mixture of multiple gas reactants is present and multiple gases are converted into products.
  • a gas-diffusion membrane can be used to fabricate the catalyst system of the present disclosure.
  • the gas-diffusion membrane is a gas-diffusion electrode (GDE) or an ion-transport membrane or a micro- structured metal or a nano-structured metal.
  • the gas-diffusion membrane is a hydrophobic porous support and/or is electrically conductive.
  • the gas- diffusion membrane is composed of porous carbon and/or polytetrafluoroethylene (PTFE). With preference, porous carbon is selected among carbon fibers and/or carbon cloth.
  • the study refers to ⁇ L/cm 2 (where ⁇ L refers to the initial Nafion® solution dispersed in the alcohol - not the final volume sprayed).
  • the ranges explored span 1 ⁇ L/cm 2 to 200 ⁇ L/cm 2 and it is noted that higher loadings are possible (e.g., up to 1 mL).
  • the optimum loading can depend on local humidity conditions (higher humidity can require higher loadings), and for the experiments was found to typically be in the range of 10-50 ⁇ I/cm 2 .
  • the loadings and other conditions can be modified depending on different ionomers, metals and reaction applications that may be used.
  • ionomer-coated metal nanoparticles can be prepared and then applied onto the 2D configuration, onto a naked gas-diffusion membrane, or onto a gas-diffusion membrane with a metal catalyst layer.
  • the tested catalyst mass loadings were within a range of 0 mg/cm 2 - 10 mg/cm 2 . These loadings could be extended to higher loadings depending on the 3D morphology and tortuosity, which in turn can depend on certain factors.
  • the morphology and tortuosity of the 3D configuration can be controlled by changing the ratio of metal nanoparticles and ionomer.
  • the size of the metal nanoparticles could go from 1 nm to about 200 nm, for example, or 1-100 nm. Although it is noted that various other sizes could also be used.
  • the metal nanoparticles used can be distinct composition, and include Cu nanoparticles and Ag nanoparticles, for instance.
  • the morphology of the final 3D architecture of the CIBH could be engineered by adjusting the solvents of the nanoparticles and the ionomer, in a similar way that bulk heterojunctions can be tuned by the choice of solvent in organic photovoltaics.
  • the 3D configurations could be sprayed, spin coated, blade coated, drop casted, etc. Heating can also be applied during ink drying both for 2D and 3D configurations to control sample morphology.
  • catalyst layers are deposited onto hydrophobic gas- diffusion electrodes so that gas reactants need only diffuse short distances to reach electroactive sites on the catalyst surface.
  • Gas reactant diffusion in the catalyst layer becomes the mass-transport-limiting step in the cathode, as observed in fuel cell oxygen reduction reactions (ORR).
  • ORR fuel cell oxygen reduction reactions
  • electrolyzer in this context refers to water electrolyzers that typically operated at high current densities and are operated at higher temperatures at large scale. With the newly developed catalyst materials as described herein, which separate gas transport, one can operate at higher temperature while keeping good efficiency and performance.
  • Fig 1A uses a constant electricity cost of 2 ⁇ /kWh
  • Fig 1 B uses a constant energy efficiency of 60%.
  • This analysis considers a CO 2 conversion of 1 ton/day and a CO 2 price of $30/ton. Both models assume a 100% utilization of CO 2 and a capacity factor of 0.8.
  • the current density is inversely proportional to the electrolyser cost, referenced according to a 1 A/cm 2 electrolyser valued at $1000/kW.
  • High-temperature solid oxide electrolysis offers a strategy to achieve CO 2 reduction with a high current density: CO 2 diffuses directly to the surface of the catalyst, in the absence of liquid electrolyte, thus overcoming the gas diffusion limitations of low temperature systems.
  • CO 2 and CO are two main potential gas reactants, but various other gases could be used (e.g. O 2 reduction reaction which has applications, for fuel cells for instance, among others).
  • O 2 reduction reaction which has applications, for fuel cells for instance, among others.
  • Decoupled gas transport in the new metal:ionomer hybrid catalyst overcomes prior limitations in high-temperature water-based CO 2 electrolysis - curtailed by the reduced CO 2 diffusion in alkaline media - and enables reporting a further 50% relative productivity improvement as operating temperature increases.
  • PFSA perfluorinated sulfonic acid
  • Fig. 3A The approach was designed to be compatible with ion transport, and simultaneously to allow long-range gas transport through hydrophobic channels. It is noted that the assembly of the ionomer can be controlled or promoted by selecting the structure and properties of the ionomer as well as the solvent, loading, thickness, and other factors.
  • the present study assessed and determined some example variables that can be used, and one can adapt the methods for determining procedures and ingredients for making various types of catalyst systems for various reactions.
  • given catalyst systems may have particular structures in terms of how the assembled ionomer is arranged to enable the hydrophilic and hydrophobic domains for molecular transport.
  • the precise morphology of given systems may be unknown or difficult to measure, but certain features such as hydrophilic groups being exposed to the catalyst and the electrolyte have been deduced in the present study.
  • PFSA ionomers such as Nafion® exhibit SO 3 - (hydrophilic) and CF 2 (hydrophobic) differentiated groups.
  • Nafion® a widely used material in fuel cells as a catalyst binder and membrane material, exhibits strong structure-function dependent properties.
  • TEM images reveal the presence of a 5 - 10 nm continuous and conformal ionomer layer (Fig 3F-H), establishing a catalyst-ionomer planar heterojunction (CIPH).
  • CIPH catalyst-ionomer planar heterojunction
  • Hydrated samples retain characteristic -CF 2 , C-C and -SO 3 - spectral features, but a notably increased relative contribution of sulfonate groups (1009 cm -1 and 1131 cm -1 ) compared to perfluoronate (730 cm -1 ). This trend is maintained during operation in 1 M KOH electrolyte at reducing potentials and with the use of other catalyst metals such as Cu, suggesting that hydrated -SO 3 - groups tend to face the electrocatalyst surface.
  • CIPH catalysts exhibit a significantly enlarged current density peaking at 250 mA/cm 2 under the same conditions (Fig. 4A), where no H 2 production was observed.
  • Fig. 4A current density peaking at 250 mA/cm 2 under the same conditions
  • Fig. 4A in situ Raman measurements, which show a notable increase in the presence of O 2 near catalyst surface at operating conditions (fig. 12).
  • the observed enhancement can be explained due to ⁇ 600x increased diffusion of O 2 relative to bulk electrolyte based on Knudsen diffusion of the reacting gas via CIPH hydrophobic domains (see methods below).
  • Cu-Cu coordination number (CN) obtained by EXAFS analysis started to increase after CO 2 R (2 min), which was maintained during a 30 min initial study.
  • the study sought to develop an additional new catalyst design that took advantage of the gas/electrolyte segregated transport beyond two dimensions. Ideally, such a catalyst would maximize the triple-phase reaction interface across an extended 3D morphology, enabling efficient operation in higher current regimes.
  • the study implemented a 3D catalyst:ionomer bulk heterojunction (CIBH) including Cu nanoparticles and Nafion® ionomer blended and spray cast on a PTFE/Cu/ionomer (CIPH) gas diffusion layer support, forming a 3D morphology with metal and ionomer percolation paths (Fig. 5A).
  • Cross-sectional SEM images reveal the different layers in the CIBH catalyst (Fig. 5B).
  • This work demonstrates metal:ionomer hybrid catalysts that exhibit phase- selective gas/electrolyte/electron transport.
  • the new catalysts decouple gas/ion/electron transport phenomena which limited the available reaction area and subsequent activity, thus enabling gas-phase electrochemistry beyond 1 A/cm 2 at cathodic energy efficiencies in the 40-50% range.
  • the study first looked at the use of ionomers with asymmetric hydrophilic and hydrophobic functionalities and designed an ionomer coating that enables differentiated gas transport channels (through hydrophobic domains) and water uptake and cation transport via hydrophilic domains, which the study characterized with a suite of in situ and ex situ Raman and wide-angle-X-ray scattering spectroscopies and microscopies.
  • the study showed the universal character of this approach in metal-ionomer catalysts for different electrochemical reactions of strong relevance such as oxygen, CO 2 and CO reductions and for different metal catalysts and target products.
  • the study presents a new catalyst-ionomer bulk- heterojunction design that enhances the gas-phase reaction interface across an extended 3D volume, thereby enabling efficient operation at higher reaction current regimes.
  • the study achieves, for the first time, CO 2 RR currents above 1.5 A/cm 2 (a sixfold increase over previous-best reported catalysts), with minimized H 2 byproduct generation and a total C 2+ partial current exceeding 1 .3 A/cm 2 .
  • the study reports a full-cell energy efficiency of 20% to C 2 products at 1.1 A/cm 2 without IR correction.
  • CIBH catalysts offer qualities for high-efficiency operation at electrolyzer-relevant temperatures.
  • the quantity of dissolved CO 2 in solution is determined by the temperature, pressure, and solution salinity. Assuming CO 2 acts as an ideal gas, the dissolved amount is given by Henry's Law: where, where T is the temperature of the solution in K. The solubility is further diminished due to high concentration of ions in solutions according to the Sechenov Equation (3): where,
  • CO 2 , CO 3 2- , HCO 3 -, OH-, H + , and H 2 O are all in equilibrium in solution as given by: where the rate constants are a function of temperature and salinity.
  • reaction term R i can be broken into carbonate equilibria (Equations 13-18): and into CO 2 reduction and OH- evolution according to the reactions ( See studies of Raciti D. et a!., Nanotechnology , 2018, 29, 044001 , entitled “Mass transport modelling for the electroreduction of CO 2 on Cu nanowires" and of Sacco A. et al., J.
  • a porous domain with Bosanquet effective diffusivity was employed for the Nafion® layer, which diminishes the effective gas diffusivity due to Knudsen diffusivity (i.e. , frequent collisions with the Nafion® pore walls shown in Figure 6).
  • the effective diffusivity is: where D g is the bulk gas diffusivity, R is the gas constant, T is the temperature, M is the molecular mass of CO 2 , d p is the mean pore diameter (2 nm for Nafion® (see studies of Mauritz K.A. etal., Chem. Rev., 2004, 104, 4535-4586, entitled “State of understanding of Nafion” and of Divisek J. etal., J. Electrochem.
  • the CO 2 penetration depth into the Nafion® is further enhanced due to the partition coefficient (given by Henry’s Law above) between the gas in Nafion® and the gas dissolved in electrolyte, thereby increasing the total available CO 2 for the Nafion® case relative to the bare electrode case.
  • the O 2 , CO 2 and CO electroreduction characteristics of the cathode electrodes were investigated using a potentiostat (Autolab PGSTAT302N), a custom-made flow cell with a fixed 1 cm 2 electrode geometric area, a digital mass flow controller (Sierra, SmartTrack 100), a current booster (Metrohm Autolab, 10 A), and two peristaltic pumps with silicone tubing.
  • a potentiostat Autolab PGSTAT302N
  • a custom-made flow cell with a fixed 1 cm 2 electrode geometric area a digital mass flow controller (Sierra, SmartTrack 100), a current booster (Metrohm Autolab, 10 A), and two peristaltic pumps with silicone tubing.
  • Cathodic catalyst materials were deposited onto polytetrafluoroethylene (PTFE) gas diffusion layers with a 450 nm mean pore size. Approximately ⁇ 300 nm nominal thick Ag and Cu films were sputtered onto the PTFE substrate using Ag and Cu targets (99.99%) at a sputtering rate ⁇ 0.2 nm ⁇ min -1 in an Angstrom Nexdep sputtering tool at a base pressure of ⁇ 10 -6 Torr.
  • PTFE polytetrafluoroethylene
  • Catalyst:ionomer planar heterojunctions (CIPH): The reference PTFE/metal electrodes were modified by spray-coating an ionomer layer from a solution of 700 mg ionomer (Nafion® perfluorinated resin solution, product #527084-25 mL purchased from Sigma Aldrich®) and 25 ml. methanol (99.8%, anhydrous, Sigma Aldrich®) until the desired ionomer loading was achieved. Samples were dried for at least 24 h at room temperature in a vacuum chamber before operation. A single sample is typically 2 cm x 2 cm in size.
  • CIBH ionomer bulk heterojunctions
  • the flow cell is comprised of three chambers: anolyte, catholyte and gas.
  • the anolyte chamber (dimensions: 12 mm x 12 mm; 9 mm depth) contains the counter electrode (nickel foam; 1.6 mm thickness).
  • the catholyte chamber (dimensions: 12 mm x 12 mm; 9 mm depth, square through hole) contains the Ag/AgCI reference electrode (CH Instruments; filled with 3M KCI solution) via a port drilled through the housing such that the frit of the reference electrode is in the center of the chamber.
  • the anolyte and catholyte chambers are separated by the anion exchange membrane (Fumasep FAB-PK-130).
  • the gas chamber (dimensions: 12 mm x 12 mm; 9 mm depth) is used to supply the reactant gas.
  • the gas and catholyte chambers are separated by the cathode.
  • the catalyst side of the cathode faces into the catholyte chamber, while the PTFE gas diffusion layer faces the gas chamber.
  • Silicone gaskets with a 1 cm 2 window are placed between each layer to achieve sufficient sealing.
  • Each chamber has an inlet and outlet connection (1/8" OD; 1/16" ID) to flow either electrolyte or gas.
  • IR compensation losses between the reference and working electrodes were determined via electrochemical impedance spectroscopy (EIS) analyses.
  • EIS electrochemical impedance spectroscopy
  • the electrode potentials upon IR compensation were scaled to the reversible hydrogen electrode (RHE) using the following expression:
  • E RHE E Ag/Agcl + 0.197 V + 0.059 ⁇ pH (26)
  • E RHE the potential of the reversible hydrogen electrode (RHE)
  • E Ag/Agcl is the applied potential
  • pH is the basicity of the catholyte. pH is calculated via a reaction- diffusion model (see study of Dinh C.-T. et al, Science, 2018, 360, 783-787, entitled "CO 2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface").
  • Cell resistance was measured in the 1x1 cm 2 flow cell at different pH conditions (table 8). Cell resistances for reference and CIPH samples were measured to be within 10% at these configurations.
  • gas products from reduction reactions were collected in 1 mL volumes using gas-tight syringes (Hamilton chromatography syringes) at least three times with the time intervals of 200 s.
  • This volume was injected into a gas chromatograph (PerkinElmer Clarus 680), equipped with a thermal conductivity detector (TCD), flame ionization detector (FID), and packed columns (Molecular Sieve 5A and Carboxen-1000).
  • TCD thermal conductivity detector
  • FID flame ionization detector
  • Argon Lide, 99.999%) was employed as the carrier gas in the gas chromatograph.
  • FEs Faradaic Efficiencies
  • Liquid product analysis liquid products were analyzed via nuclear magnetic resonance spectroscopy (NMR) from respective catholyte solutions. A new cathode, catholyte, and anolyte was used for the collection of a single liquid product distribution at a given applied potential. A constant volume of 25 mL was recirculated through anode and cathode compartments using peristaltic pumps. The flow cell was operated at the desired applied potential for at least 800 s. Cathode electrolyte was collected from the flow cell and tubing, sealed and stored in a fridge until NMR sample preparation.
  • NMR nuclear magnetic resonance spectroscopy
  • NMR sample preparation stored solutions were diluted 20 times in Dl water and mixed with an internal standard, dimethyl sulfoxide (DMSO), in NMR tubes.
  • 1 HNMR spectra were collected on an Agilent DD2 500 spectrometer in D 2 O in water suppression mode, and liquid product distributions were obtained by analyzing the resulting spectra in MestReNova.
  • the relaxation time between the peaks was selected as 16 s to ensure complete proton relaxation.
  • ECSA Methods Cyclic Voltammetry (CV) scans were recorded at five scan rates with a minimum of 3 cycles in the non-Faradaic region, specifically between -0.7 V vs. Ag/AgCI and -1.1 V vs. Ag/AgCI. Scan rates of 20 mV/s, 40 mV/s, 60 mV/s, 80 mV/s, 100 mV/s, and 200 mV/s were used. The currents at a given potential, -0.8 V vs. Ag/AgCI, were recorded from the forward and reverse scans of the third cycle. The difference between these currents was plotted against the scan rate to obtain a straight line.
  • CV Cyclic Voltammetry
  • the slope of this line corresponds to the capacitance of the catalyst’s electric double layer in Farads.
  • the roughness factor (RF) is obtained by dividing this slope by the specific capacitance of electropolished copper. Measurements were conducted under constant CO 2 flow and the recirculation of 5M KOH electrolyte.
  • Partial pressure studies were carried out using the same configuration. The relative flows of CO 2 /N 2 and CO/N 2 gas mixtures were controlled using two mass-flow controllers (Sierra), and the total flow maintained at ⁇ 50 cm 3 /min.
  • H-cell experiments Experiments in the h-cell were performed by using PTFE/metal samples as working electrodes fully immersed in electrolyte solution. The area was masked using Kapton tape to be ⁇ 1 cm 2 . An anion exchange membrane was used together with a Pt foil counter electrode at the anode.
  • WAXS measurements were carried out in transmission geometry at the CMS beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) office of the Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory. Samples were measured with an imaging detector at a distance of 0.153 m using an X-ray wavelength of 0.729 ⁇ . Nika software package was used to sector average the 2D WAXS images. Data plotting was done in Igor Pro (Wavemetrics, Inc., Lake Oswego, OR, USA). For grazing-incidence WAXS (GIWAXS), ionomer samples were deposited by spray coating on cleaned Si substrates using a similar protocol to standard samples.
  • DOE U.S. Department of Energy
  • Contact angle measurements were performed using the sessile drop method on a video-based contact angle measuring system (OCA 15EC). Briefly, a single water droplet was placed on the sample and approximately 15 seconds was given before the contact angles were measured by the computer software.
  • Raman measurements In situ and ex situ Raman spectra were recorded with a Renishaw Raman spectrometer using a 785 nm excitation laser and 1200 mm -1 grating. Spectra were collected in the range of 200 - 3000 cm -1 over 10 acquisitions with an exposure time of 10 seconds for each acquisition. These were averaged together and analyzed using WiRE 4.4 software. The laser power was 200 ⁇ W and a 63x magnification immersion objective was used with a custom PTFE flow cell.
  • the in situ flow cell had a liquid electrolyte reservoir in which the immersion objective was dipped and a gas diffusion electrode separated the electrolyte reservoir and the gas channel that continuously delivered CO 2 gas to the catalyst at a flow rate of 50 cm 3 /min.
  • ORR air was fed using peristaltic pumps.
  • the area of the electrode in this configuration was 1 cm 2 .
  • the counter electrode, a Pt wire, and the reference electrode, Ag/AgCI, were dipped in the electrolyte reservoir ⁇ 1 cm from the cathode.
  • XAS measurements in situ XAS measurements was carried out at 9BM beamline of the Advanced Photon Source (APS) in Argonne National Laboratory (Lemont, Illinois). Operando XAS experiment for CO 2 RR proceeded by using in situ XAS flow cell (Applied potential: -2.0 V vs. Ag/AgCI (chronoamperometry), electrolyte: 5 M KOH, CO 2 flow).

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Abstract

La divulgation présente, sous un premier aspect, un système catalyseur pour l'électrolyse en phase gazeuse d'un gaz réactif pour former un produit dans un milieu aqueux, le système catalyseur comprenant un matériau catalytique; une couche polymère conductrice d'ions disposée sur le matériau catalytique et comprenant un polymère conducteur d'ions qui comprend des groupes hydrophiles et hydrophobes. Ledit système catalyseur est remarquable en ce que la couche polymère conductrice d'ions présente une épaisseur de 2 nm à 50 nm mesurée par microscopie électronique à transmission. Sous son deuxième aspect, la divulgation présente un procédé de fabrication d'un système catalyseur pour l'électrolyse en phase gazeuse d'un gaz réactif pour produire un produit dans un milieu aqueux, de préférence selon le premier aspect. Est également divulguée l'utilisation du système catalyseur selon le premier aspect dans la production électrochimique d'au moins un composé multi-carbone à partir d'un gaz contenant du carbone ou d'au moins un produit à partir d'un gaz réactif.
EP20800640.3A 2019-11-04 2020-11-03 Systèmes catalyseur-ionomère et procédés d'électrolyse en phase gazeuse Pending EP4055211A1 (fr)

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