WO2023105204A1 - Couche de catalyseur - Google Patents

Couche de catalyseur Download PDF

Info

Publication number
WO2023105204A1
WO2023105204A1 PCT/GB2022/053094 GB2022053094W WO2023105204A1 WO 2023105204 A1 WO2023105204 A1 WO 2023105204A1 GB 2022053094 W GB2022053094 W GB 2022053094W WO 2023105204 A1 WO2023105204 A1 WO 2023105204A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst layer
platinum group
electrocatalyst
group metal
range
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.)
Ceased
Application number
PCT/GB2022/053094
Other languages
English (en)
Inventor
Adam Hodgkinson
Wayne Turner
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.)
Johnson Matthey Hydrogen Technologies Ltd
Original Assignee
Johnson Matthey Hydrogen Technologies Ltd
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 Johnson Matthey Hydrogen Technologies Ltd filed Critical Johnson Matthey Hydrogen Technologies Ltd
Priority to GB2405555.0A priority Critical patent/GB2626873A/en
Publication of WO2023105204A1 publication Critical patent/WO2023105204A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
    • H01M4/8673—Electrically conductive fillers
    • 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
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • 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
    • C25B11/054—Electrodes comprising electrocatalysts supported on a carrier
    • 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
    • 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
    • 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
    • H01M4/88—Processes of manufacture
    • H01M4/8825—Methods for deposition of the catalytic active composition
    • H01M4/8828—Coating with slurry or ink
    • 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
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • 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
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
    • C25B11/065—Carbon
    • 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
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • This invention relates to a catalyst layer for an electrode of a fuel cell.
  • This invention also relates to an associated cathode, catalyst-coated ion-conducting membrane, membrane electrode assembly, and fuel cell comprising the catalyst layer; and to associated methods of producing the catalyst layer.
  • a fuel cell is an electrochemical cell comprising two electrodes separated by an electrolyte.
  • a fuel e.g. hydrogen, an alcohol such as methanol or ethanol, or formic acid
  • an oxidant e.g. oxygen or air
  • Electrochemical reactions occur at the electrodes, and the chemical energy of the fuel and the oxidant is converted to electrical energy and heat.
  • Electrocatalysts are used to promote the electrochemical oxidation of the fuel at the anode and the electrochemical reduction of oxygen at the cathode.
  • Fuel cells are usually classified according to the nature of the electrolyte employed. Often the electrolyte is a solid polymeric membrane, in which the membrane is electronically insulating but ionically conducting. In the proton exchange membrane fuel cell (PEMFC) the ion-conducting membrane is proton conducting, and protons, produced at the anode, are transported across the ion-conducting membrane to the cathode, where they combine with oxygen to form water.
  • PEMFC proton exchange membrane fuel cell
  • a principal component of the PEMFC is the membrane electrode assembly, which is essentially composed of five layers.
  • the central layer is the polymer ion-conducting membrane.
  • On either face of the ion-conducting membrane there is an electrocatalyst layer, containing an electrocatalyst designed for the specific electrolytic reaction.
  • an electrocatalyst layer containing an electrocatalyst designed for the specific electrolytic reaction.
  • a gas diffusion layer adjacent to each electrocatalyst layer there is a gas diffusion layer.
  • the gas diffusion layer must allow the reactants to reach the electrocatalyst layer and must conduct the electric current that is generated by the electrochemical reactions. Therefore, the gas diffusion layer must be porous and electrically conducting.
  • the electrocatalyst layers also generally comprise a proton conducting material, such as a proton conducting polymer, to aid transfer of protons from the anode electrocatalyst to the ion-conducting membrane and/or from the ion-conducting membrane to the cathode electrocatalyst.
  • a proton conducting material such as a proton conducting polymer
  • the membrane electrode assembly can be constructed by a number of methods. Typically, the methods involve the application of one or both of the electrocatalyst layers to an ion-conducting membrane to form a catalyst coated ion-conducting membrane. Subsequently, a gas diffusion layer is applied to the electrocatalyst layer.
  • an electrocatalyst layer is applied to a gas diffusion layer to form a gas diffusion electrode, which is then combined with the ion-conducting membrane.
  • a membrane electrode assembly can be prepared by a combination of these methods e.g. one electrocatalyst layer is applied to the ion-conducting membrane to form a catalyst coated ion-conducting membrane, and the other electrocatalyst layer is applied as a gas diffusion electrode.
  • the electrocatalyst layers are applied using an electrocatalyst ink which conventionally comprises an electrocatalyst material, an ion-conducting polymer, solvents and/or diluents, and any agents desired to be included in the electrocatalyst layer.
  • the electrocatalyst layers generally comprise an electrocatalyst material comprising a metal or metal alloy suitable for the fuel oxidation or oxygen reduction reaction, depending on whether the layer is to be used at the anode or cathode.
  • Electrocatalysts for fuel oxidation and oxygen reduction are typically based on platinum or platinum alloyed with one or more other metals.
  • the platinum or platinum alloy electrocatalyst can be in the form of unsupported nanometre sized particles (for example metal blacks) or can be deposited as discrete nanoparticles onto a support material (a supported electrocatalyst).
  • Electrocatalysts can also be in the form of coatings or extended films deposited onto a support material.
  • PEMFCs have a number of applications, including automotive.
  • PEMFCs can be beneficial for use in heavy-duty, long life automotive application such as trucks.
  • there is a desire to reduce cost of ownership over the long life required of the PEMFC which, in some circumstances, is more desirable than lowering upfront cost.
  • the object of the present invention is to provide a catalyst layer which can be used to prepare fuel cells which are cost effective over a long life in real-world automotive use.
  • the present invention provides a catalyst layer comprising: an ion-conducting polymer; and an electrocatalyst, the electrocatalyst comprising: an electrically conductive support; and metal particles supported on the electrically conductive support; wherein the metal particles are a platinum group metal, and have a mean average crystallite size in the range of 3.5 to 8.0 nm when measured by powder X-ray diffraction (PXRD); wherein the electrocatalyst comprises the metal particles in an amount in the range of and including 60 to 75 wt.% based on the total weight of the electrocatalyst; and wherein the catalyst layer has a platinum group metal loading in the range of and including 0.6 to 1.0 mg of platinum group metal per cm 2 of the geometric area of the catalyst layer.
  • PXRD powder X-ray diffraction
  • a catalyst-coated ion-conducting membrane comprising a catalyst layer according to the invention and an ion-conducting membrane.
  • gas diffusion electrode comprising a catalyst layer according to the invention and a gas diffusion layer.
  • a catalysed decal transfer substrate comprising a catalyst layer according to the invention and a decal transfer substrate.
  • a membrane electrode assembly comprising a catalyst layer according to the invention, the catalyst-coated ion-conducting membrane, or the gas diffusion electrode.
  • a fuel cell comprising the catalyst layer according to invention, the catalyst-coated ion-conducting membrane, the gas diffusion electrode, or the membrane electrode assembly.
  • a water electrolysis cell comprising the catalyst layer according to the invention, the catalyst-coated ion-conducting membrane, the gas diffusion electrode, or the membrane electrode assembly.
  • the present invention also provides a method of producing the catalyst layer according to the first aspect of the invention, the method comprising the steps of: preparing an ink dispersion comprising an electrocatalyst and an ion-conducting polymer; and applying the ink dispersion onto a substrate; and drying or curing the ink dispersion to form the catalyst layer; wherein the electrocatalyst comprises: an electrically conductive support, and metal particles supported on the electrically conductive support, wherein the metal particles are a platinum group metal, and have a mean average crystallite size in the range of and including 3.5 to 8.0 nm, when measured by powder X-ray diffraction (PXRD); wherein the electrocatalyst comprises the platinum group metal in an amount in the range of and including 60 to 75 wt.% based on the total weight of the electrocatalyst, and wherein the catalyst layer has a platinum group metal loading in the range of and including 0.6 to 1 .0 mg of platinum group metal per cm 2 of the
  • FIG. 1 is graph showing cathode effective platinum surface area (EPSA) as a function of cycle number
  • Figure 2 is a graph showing fraction of cathode EPSA lost as a function of cycle number
  • Figure 3 is a graph showing cell voltage as a function of cycle number at a current density of 1.6 A/cm 2 ;
  • Figure 4 is a graph showing cell voltage as a function of cycle number at a current density of 1.0 A/cm 2 ;
  • Figure 5 is a graph showing cell voltage as a function of cycle number at a current density of 0.5 A/cm 2 .
  • the catalyst layer of the invention is suitably a fuel cell catalyst layer, preferably a proton exchange membrane (PEM) fuel cell catalyst layer.
  • the catalyst layer may be an anode or a cathode catalyst layer, preferably a cathode catalyst layer. Accordingly, most preferably the catalyst layer is a PEM fuel cell cathode catalyst layer.
  • the catalyst layer has a thickness in the range of and including 10 to 20 pm, preferably 10 to 15 pm. The thickness of the catalyst layer can be directly measured by scanning electron microscopy or by optical microscopy.
  • the ion-conducting polymer can have a loading in the catalyst layer in the range of and including 60 wt.% to 150 wt.% based on the weight of the electrically conductive support of the electrocatalyst.
  • the ion-conducting polymer is suitably a proton-conducting polymer.
  • Preferred ionconducting polymers are partially- or fully-fluorinated sulphonic acid polymers e.g. perfluorinated sulphonic acid polymers.
  • the ion-conducting polymer may be based on a perfluorinated sulphonic acid material such as National® (Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion® (Asahi Glass Group) and Aciplex® (Asahi Kasei Chemicals Corp.).
  • the ion-conducting materials may be based on a sulphonated hydrocarbon polymer, such as those available from FuMA-Tech GmbH as the fumapem® P, E or K series of products, JSR Corporation, Toyobo Corporation, and others.
  • a sulphonated hydrocarbon polymer such as those available from FuMA-Tech GmbH as the fumapem® P, E or K series of products, JSR Corporation, Toyobo Corporation, and others.
  • the electrocatalyst comprises an electrically conductive support and metal particles supported on the electrically conductive support.
  • the electrocatalyst consists essentially of, and preferably consists of, the electrically conductive support and metal particles supported on the electrically conductive support.
  • the term “supported” will be readily understood by a skilled person. For example, it will be understood that the term “supported” includes the electrocatalyst being dispersed on the support material and bound or fixed to the support material by physical or chemical bonds. For instance, the electrocatalyst may be bound or fixed to the support material by way of ionic or covalent bonds, or non-specific interactions such as van der Waals forces.
  • the metal particles are selected from a platinum group metal. That is, the metal particles are selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium and osmium. Preferably, the metal particles are platinum particles.
  • the electrically conductive support may be an electrically conductive carbon support material.
  • the electrically conductive carbon support material is a carbon powder which may be, for example, a carbon black or graphitised carbon black for example a commercially available carbon black (such as from Cabot Corp. (Vulcan® XC72R) or Akzo Nobel (the Ketjen® black series)).
  • Another suitable carbon support material is an acetylene black (e.g. those available from Chevron Phillips (Shawinigan Black®) or Denka).
  • the electrically conductive support material is an electrically conductive carbon support material which has a specific surface area (BET) of 100 to 600 m 2 /g, suitably 250 to 500 m 2 /g and a micropore area of 10 to 90 m 2 /g, suitably 25 to 80 m 2 /g.
  • BET specific surface area
  • Such an electrically conductive carbon support can be prepared by the method disclosed in WO2013/045894.
  • the determination of the specific surface area by the BET method is carried out by the following process: after degassing to form a clean, solid surface, a nitrogen adsorption isotherm is obtained, whereby the quantity of gas adsorbed is measured as a function of gas pressure, at a constant temperature (usually that of liquid nitrogen at its boiling point at one atmosphere pressure).
  • a plot of 1/[V a ((Po/P)-1)] vs P/Po is then constructed for P/Po values in the range
  • V a is the quantity of gas adsorbed at pressure
  • P, and P o is the saturation pressure of the gas.
  • a straight line is fitted to the plot to yield the monolayer volume (V m ), from the intercept 1/V m C and slope (C-1)/V m C, where C is a constant.
  • the surface area of the sample can be determined from the monolayer volume by correcting for the area occupied by a single adsorbate molecule. More details can be found in ‘Analytical Methods in Fine Particle Technology’, by Paul A. Webb and Clyde Orr, Micromeritics Instruments Corporation 1997.
  • the micropore area refers to the surface area associated with the micropores, where a micropore is defined as a pore of internal width less than 2 nm.
  • the micropore area is determined by use of a t-plot, generated from the nitrogen adsorption isotherm as described above.
  • the t-plot has the volume of gas adsorbed plotted as a function of the standard multilayer thickness, t, where the t values are calculated using the pressure values from the adsorption isotherm in a thickness equation; in this case the Harkins-Jura equation.
  • the slope of the linear portion of the t-plot at thickness values between 0.35 and 0.5 nm is used to calculate the external surface area, that is, the surface area associated with all pores except the micropores.
  • the micropore surface area is then calculated by subtraction of the external surface area from the BET surface area. More details can be found in ‘Analytical Methods in Fine Particle Technology’, by Paul A. Webb and Clyde Orr, Micromeritics Instruments Corporation 1997.
  • the electrically conductive support can comprise particles or aggregates having a mean average particle size in the range of 30 nm to 200 nm.
  • the mean average particle size of the particles or aggregates of the electrically conductive support can be measured by laser light scattering, for example using a Mastersizer 3000TM commercially available from Malvern Panalytical Limited.
  • the metal particles have a crystallite size in the range of and including 3.5 to 8.0 nm, preferably 4.0 to 7.0 nm, preferably 4.5 to 6.5 nm, and most preferably 4.5 to 6.0 nm when measured by powder X-ray diffraction.
  • the electrocatalyst can have a CO metal area (COMA) in the range of and including 25 to 50 m 2 /g of the platinum group metal, preferably 30 to 45 m 2 /g of the platinum group metal, and more preferably 35 to 40 m 2 /g of the platinum group metal.
  • the COMA was determined using gas phase adsorption of carbon monoxide (CO).
  • the gas phase COMA is determined by reducing the catalyst, in its as-made form prior to incorporation into a catalyst layer, in hydrogen, then titrating aliquots of carbon monoxide gas until the active metal surface is saturated with a chemisorbed CO monolayer, and there is no more uptake. The moles of CO chemisorbed is measured.
  • the measurement is normalised for standard temperature (T s «) and standard pressure (p s «) by multiplying by (— x -) where p and T are the pressure and -Pstd T J temperature of the measurement respectively.
  • the moles of CO chemisorbed can then be converted into a metal surface area by assuming the number of atoms/m 2 of metal (e.g. 1 .25 x io 19 atoms/m 2 for Pt) as defined in ‘Catalysis - Science and Technology, Vol. 6, p. 257, Eds J. R. Anderson and M. Boudart.
  • the loading of platinum group metal can be determined using inductively coupled plasma mass spectrometry (ICPMS).
  • ICPMS inductively coupled plasma mass spectrometry
  • the electrocatalyst comprises the metal particles in an amount in the range of and including 60 to 75 wt.% based on the total weight of the electrocatalyst.
  • the electrocatalyst comprises the metal particles in an amount in the range of and including 65 to 70 wt.% based on the total weight of the electrocatalyst.
  • the loading of platinum group metal in the catalyst layer can also be determined using gravimetric analysis and/or using X-ray fluorescence (XRF) spectroscopy.
  • the catalyst layer has a platinum group metal loading in the range of and including 0.60 to 1 .00 mg of platinum group metal per cm 2 of the geometric area of the catalyst layer.
  • the catalyst layer preferably has a platinum group metal loading in the range of and including 0.70 to 0.95 mg of platinum group metal per cm 2 of the geometric area of the catalyst layer, preferably 0.75 to 0.90 mg of platinum group metal per cm 2 of the geometric area of the catalyst layer, and more preferably 0.80 to 0.85 mg of platinum group metal per cm 2 of the geometric area of the catalyst layer.
  • the loading density of platinum group metal in the catalyst layer can be determined using the following formula:
  • the catalyst layer can have a loading density of platinum group metal of at least 400 mg of platinum group metal per cm 3 of the geometric volume of the catalyst layer, preferably 450 mg of PGM per cm 3 , more preferably at least 500 mg of PGM per cm 3 , more preferably at least 550 mg of PGM per cm 3 , and more preferably at least 600 mg of PGM per cm 3 .
  • the catalyst layer can have a loading density of platinum group metal of 1000 mg of platinum group metal per cm 3 of the geometric volume of the catalyst layer or less, preferably 900 mg of PGM per cm 3 or less, and more preferably 800 mg of PGM per cm 3 or less.
  • the loading density of platinum group metal in the catalyst layer can be within a range defined by any combination of the aforementioned limits.
  • the catalyst layer may have an electrochemically active surface area (ECSA) in the range of and including 25 to 50 m 2 /g of the platinum group metal, preferably 30 to 45 m 2 /g of the platinum group metal, and more preferably about 35 m 2 /g of the platinum group metal.
  • ECSA is measured using a cyclic voltammetry protocol with carbon monoxide (CO) stripping. The measurement is made with the MEA in the fuel cell. Further details are available in J. Power Sources, 242 (2013), 244-255.
  • the catalyst layer may comprise further components including but not limited to, an oxygen evolution reaction catalyst; a hydrogen peroxide decomposition catalyst; a hydrophobic additive (e.g. a polymer such as polytetrafluoroethylene (PTFE) or an inorganic solid with or without surface treatment) or a hydrophilic additive (e.g. a polymer of an inorganic solid, such as an oxide) to control reactant and water transport characteristics.
  • a hydrophobic additive e.g. a polymer such as polytetrafluoroethylene (PTFE) or an inorganic solid with or without surface treatment
  • a hydrophilic additive e.g. a polymer of an inorganic solid, such as an oxide
  • the ink dispersion is prepared by dispersing the electrocatalyst, the ion-conducting polymer, and any further components, in an aqueous and/or organic solvent. If required, particle break-up may be carried out by methods known in the art, such as high shear mixing, milling, ball milling, passing through a microfluidiser etc. or a combination thereof, to achieve a suitable particle size distribution.
  • the ink is applied onto a substrate (e.g. a decal transfer substrate, a gas diffusion layer, or an ion-conducting membrane) to form the catalyst layer.
  • a substrate e.g. a decal transfer substrate, a gas diffusion layer, or an ion-conducting membrane
  • the ink may be deposited by any suitable technique known to those in the art, including but not limited to gravure coating, slot die (slot, extrusion) coating, screen printing, rotary screen printing, inkjet printing, spraying, painting, bar coating, pad coating, gap coating techniques such as knife or doctor blade over roll, and metering rod application. Drying or curing is typically carried out at a temperature of 70 to 120°C but will depend on the nature of the dispersant and could be up to, or over, 200°C.
  • the catalyst layer may be annealed, in addition to being dried, to alter and strengthen the crystalline structure of the ionconducting polymer. Any annealing step would employ elevated temperatures compared to the drying step, for example up to 200°C.
  • the gas diffusion layer typically comprises a gas diffusion substrate and, preferably, a microporous layer.
  • Typical gas diffusion substrates include non-woven papers or webs comprising a network of carbon fibres and a thermoset resin binder (e.g. the TGP-H series of carbon fibre paper available from Toray Industries Inc., Japan or the H2315 series available from Freudenberg FCCT KG, Germany, or the Sigracet® series available from SGL Technologies GmbH, Germany or AvCarb® series from Ballard Power Systems Inc.), or woven carbon cloths.
  • the carbon paper, web or cloth may be provided with a pre-treatment prior to fabrication of the electrode and being incorporated into a membrane electrode assembly either to make it more wettable (hydrophilic) or more wet-proofed (hydrophobic).
  • the nature of any treatments will depend on the type of fuel cell and the operating conditions that will be used.
  • the substrate can be made more wettable by incorporation of materials such as amorphous carbon blacks via impregnation from liquid suspensions, or can be made more hydrophobic by impregnating the pore structure of the substrate with a colloidal suspension of a polymer such as PTFE or polyfluoroethylenepropylene (FEP), followed by drying and heating above the melting or flow point of the polymer.
  • Typical microporous layers comprise a mixture of a carbon black and a polymer such as polytetrafluoroethylene (PTFE).
  • the decal transfer substrate may be formed from any suitable material from which the electrocatalyst layer can be removed without damage.
  • suitable materials include a fluoropolymer, such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymer (PFA), fluorinated ethylene propylene (FEP - a copolymer of hexafluoropropylene and tetrafluoroethylene) and polyolefins.
  • a catalyst layer of the invention can be applied to one or both faces of the ion-conducting membrane.
  • the catalyst layer is applied to one face, which corresponds with the cathode side.
  • the ionconducting membrane may be any membrane suitable for use in a proton exchange membrane fuel cell, for example the membrane may be based on a perfluorinated sulphonic acid material such as NationalTM (Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion® (Asahi Glass Group) and AciplexTM (Asahi Kasei Chemicals Corp.).
  • the membrane may be based on a sulphonated hydrocarbon membrane such as those available from FuMA-Tech GmbH as the fumapem® P, E or K series of products, JSR Corporation, Toyobo Corporation, and others.
  • the membrane may be based on polybenzimidazole doped with phosphoric acid which will operate in the range 120 °C to 180 °C.
  • the ion-conducting membrane component may comprise one or more materials that confer mechanical strength to the ion-conducting membrane component.
  • the ion-conducting membrane component may contain a porous reinforcing material, such as an expanded PTFE material or a nanofibre network, such as an electro-spun fibre network.
  • the ion-conducting membrane may comprise one or more hydrogen peroxide decomposition catalysts either as a layer on one or both faces of the membrane, or embedded within the membrane, either uniformly dispersed throughout or in a layer.
  • the hydrogen peroxide decomposition catalyst suitable for use are known to those skilled in the art and include metal oxides, such as cerium oxides, manganese oxides, titanium oxides, beryllium oxides, bismuth oxides, tantalum oxides, niobium oxides, hafnium oxides, vanadium oxides and lanthanum oxides; suitably cerium oxides, manganese oxides or titanium oxides; preferably cerium dioxide (ceria) or a mixed ceria-zirconia oxide.
  • the ion-conducting membrane component may optionally comprise a recombination catalyst, in particular a catalyst for the recombination of unreacted H2 and O2, that can diffuse into the membrane from the anode and cathode respectively, to produce water.
  • a recombination catalyst in particular a catalyst for the recombination of unreacted H2 and O2, that can diffuse into the membrane from the anode and cathode respectively, to produce water.
  • Suitable recombination catalysts comprise a metal (such as platinum or palladium) on a high surface area oxide support material (such as silica, titania, zirconia) or carbon support. More examples of recombination catalysts are disclosed in EP0631337 and WO00/24074.
  • the membrane electrode assembly disclosed herein may be made up in a number of ways including, but not limited to:
  • an ion-conducting membrane may be sandwiched between two gas diffusion electrodes (one anode and one cathode), one or both of which may comprise a catalyst layer of the invention;
  • a catalyst coated ion-conducting membrane having a catalyst layer of the invention on one side may be sandwiched between a gas diffusion layer and a gas diffusion electrode, which may comprise a catalyst layer of the invention, the gas diffusion layer contacting the side of the catalyst coated ion-conducting membrane having the catalyst layer or;
  • the fuel cell disclosed herein is preferably a PEM fuel cell.
  • Pt/C electrocatalysts (E1 , E2 and E3) were prepared using methods similar to the general method for preparing carbon-supported platinum catalysts described in WO2013/045894.
  • the method included a step of growing the platinum crystallite size.
  • Electrocatalyst E1 had a mean average platinum crystallite size of 4.7 nm, and a Pt loading of 65 % by weight of the total weight of the electrocatalyst.
  • the CO metal area (COMA) of the electrocatalyst was 35 m 2 /g of Pt.
  • Electrocatalyst E2 had a mean average platinum crystallite size of 2.7 nm, and a Pt loading of 50 % by weight of the total weight of the electrocatalyst.
  • the CO metal area of the electrocatalyst was 50 m 2 /g of Pt.
  • Electrocatalyst E3 had a mean average platinum crystallite size of 2.7 nm, and a Pt loading of 50 % by weight of the total weight of the electrocatalyst.
  • the CO metal area of the electrocatalyst was 48 m 2 /g of Pt.
  • Platinum crystallite size was measured by powder X-ray diffraction (PXRD).
  • Rietveld refinements were performed using Topas [1] with reflection profiles modelled using a fundamental parameters approach [2] with reference data collected from NIST660 LaBe. In each instance the data were fitted over the 30 ⁇ 20 ⁇ 130° range using a full structural model with crystallite sizes calculated for each sample using the volume weighted column height LVol-IB method. [3]
  • the CO metal area was determined using gas phase adsorption of carbon monoxide (CO).
  • the gas phase COMA is determined by reducing the catalyst, in its as-made form prior to incorporation into a catalyst layer, in hydrogen, then titrating aliquots of carbon monoxide gas until the active metal surface is saturated with a chemisorbed CO monolayer, and there is no more uptake.
  • the moles of CO chemisorbed can then be converted into a metal surface area, by assuming 1.25 x 10 19 atoms/m 2 for Pt as defined in ‘Catalysis - Science and Technology, Vol. 6, p. 257, Eds J. R. Anderson and M. Boudart.
  • ionomer dispersion containing a perfluorinated sulphonic acid (PFSA) ionomer ( ⁇ 20 wt.%, 800 EW) in an alcohol/water solvent mix was prepared. 126 g of the ionomer mix was then further diluted with alcohol/water solvent mix. 90 g of electrocatalyst (E1) was mixed with the resulting ionomer dispersion. This mixture was mechanically agitated using an overhead stirrer until all of the catalyst material had been wetted and dispersed in the solvent to form an ink. The ink was then processed using a bead mill to form a well-dispersed ink containing electrocatalyst E1.
  • PFSA perfluorinated sulphonic acid
  • ionomer dispersion containing a perfluorinated sulphonic acid (PFSA) ionomer ( ⁇ 20 wt.%, 800 EW) in an alcohol/water solvent mix was prepared. 200 g of the ionomer mix was then further diluted with alcohol/water solvent mix. 100 g of an electrocatalyst (E2 or E3) was mixed with the resulting ionomer dispersion. This mixture was mechanically agitated using an overhead stirrer until all of the catalyst material had been wetted and dispersed in the solvent to form an ink. The ink was then processed using a bead mill to form a well-dispersed ink containing electrocatalyst E2 or E3.
  • PFSA perfluorinated sulphonic acid
  • the ink for the cathode catalyst layer was then coated onto a skived PTFE sheet using a slot die coating process where the metal loading (in mgPGM/cm 2 of the geometric area of the catalyst layer) was controlled. The coating was dried to remove the solvent and form a cathode catalyst layer.
  • Anode catalyst layers were prepared by first forming inks containing a PFSA ionomer dispersed in an alcohol/water solvent mixture, and HiSPEC® 3000 electrocatalyst material (commercially available from Johnson Matthey Fuel Cells Ltd.). This mixture was mechanically agitated using an overhead stirrer until all of the catalyst had been wetted and dispersed in the liquid. The ink was then processed through a bead mill to form a well dispersed ink.
  • the ink for the anode catalyst layer was then coated onto a PTFE sheet using a slot die coating process with a platinum loading of 0.08 mgPt/cm 2 of the geometric area of the catalyst layer. The coating was dried to remove the solvent and form an anode catalyst layer.
  • Catalyst-coated ion-conducting membranes (with an active area of 50 cm 2 ) were prepared by transferring the cathode and anode catalyst layers from their respective PTFE sheets to either side of an ion-conducting membrane (thickness of 15 pm) respectively using a decal transfer process.
  • a gas diffusion layer (Sigracet 22 BB, commercially available from SGL Carbon) was applied to each face of each catalyst coated ion-conducting membrane to form the complete membrane electrode assemblies MEA1 , MEA2, MEA 3.
  • the gas diffusion layer used was a carbon fibre paper with a hydrophobic microporous layer containing carbon and PTFE applied to the face in contact with the catalyst coated ion-conducting membrane.
  • MEA 1 contained a cathode catalyst layer of the invention containing electrocatalyst E1 , with a platinum loading in the cathode catalyst layer of 0.8 mg platinum/cm 2 the geometric area of the catalyst layer.
  • the cathode catalyst layer of MEA 1 had a thickness of 15 pm.
  • the cathode catalyst layer of MEA1 had a platinum layer density of 533 mg/cm 3 .
  • MEA 2 contains a comparative cathode catalyst layer containing electrocatalyst E2.
  • the platinum loading in the cathode catalyst layer was 0.4 mg of Pt per cm 2 of geometric area.
  • the cathode catalyst layer of MEA 2 had a thickness of 11 pm.
  • the cathode catalyst layer of MEA1 had a platinum layer density of 364 mg/cm 3 .
  • MEA 3 contains a comparative cathode catalyst layer containing electrocatalyst E3.
  • the platinum loading in the cathode catalyst layer was 0.6 mg of Pt per cm 2 of geometric area.
  • the cathode catalyst layer of MEA 3 had a thickness of 18 pm.
  • the cathode catalyst layer of MEA1 had a platinum layer density of 333 mg/cm 3 .
  • Polarisation curves were performed at 80 °C, 40 %RH, and 50 kPag. Polarisation curves were collected in both air and undiluted oxygen at stoichiometries of 1.8 and 9 respectively.
  • the electrochemically active surface area was determined by CO stripping cyclic voltammetry.
  • the CO stripping cyclic voltammetry was performed at 80 °C, 100%RH and 100 kPag, and the potential was cycled between +0.125 V and +0.8 V (with respect to the anode potential) at a scan rate of 25 mV/s.
  • the cell performance was measured as follows. The cell was initially held at 80 °C, 100 %RH and an atmospheric pressure outlet condition with a flow of H2 gas on the anode and N2 gas on the cathode. The cathode potential was cycled using a triangular wave between +0.6 V and +1.0 V (with respect to the anode potential) at a scan rate of 50 mV/s for 1000 cycles. The cell was then reconditioned at 80 °C, 40%RH and 50kPag for 4 hours. Polarisation curves and cyclic voltammetry were performed as previous described. This process was repeated for cumulative cycles of 5,000, 10,000, and 30,000 cycles.
  • Figure 1 shows the effective platinum surface area (EPSA) of the cathode as a function of the number of cycles for MEA1 , MEA2 and MEA3.
  • Figure 2 shows the fraction EPSA loss as a function of the number of cycles for MEA1 , MEA2 and MEA3.
  • EPSA of MEA3 at start of life was higher than for MEA1 , the EPSA of MEA3 degraded more rapidly than MEA1.
  • MEA1 exhibited lower fractional EPSA loss as a result of cell cycling compared with MEA2 and MEA3. This is indicative of the catalyst layer of MEA1 having improved durability compared with MEA2 and MEA3.
  • Figures 3 to 5 show the cell voltage as a function of the number of cycles at current densities of 1.6 A/cm 2 , 1.0 A/cm 2 and 0.5 A/cm 2 respectively.
  • MEA1 and MEA3 achieved similar start of life cell voltages at all current densities. However, MEA1 maintained a more consistent cell voltage over 30,000 cycles compared with MEA 3.
  • MEA1 gave the best end of life cell performance.
  • MEA1 exhibited improved durability compared with MEA2 and MEA3, which is indicative of a more stable catalyst layer.
  • the improved durability in cell performance provides an improved usable lifetime of membrane electrode assemblies (and electrochemical devices) containing the catalyst layers of the present invention. This can reduce fuel consumption over the lifetime of the electrochemical device (e.g. fuel cell stack). Consequently, the overall cost of ownership of associated electrochemical cells can be reduced, which is particularly beneficial when used in heavy-duty, long-life automotive applications, such as trucks.
  • Topas V5.0 General Profile and Structure Analysis Software for Powder Diffraction Data, Bruker AXS, Düsseldorf, Germany, (2003-2015).

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Catalysts (AREA)

Abstract

La présente invention concerne une couche de catalyseur comprenant : un polymère conducteur d'ions ; et un électrocatalyseur. L'électrocatalyseur comprend un support électroconducteur, et des particules métalliques supportées sur le support électroconducteur. Les particules métalliques sont un métal du groupe du platine, et ont une taille moyenne de cristallite moyenne dans la plage de et comprenant de 3,5 à 8,0 nm, lorsqu'elles sont mesurées par diffraction des rayons X sur poudre (PXRD). L'électrocatalyseur comprend les particules métalliques en une quantité dans la plage de et comprenant de 60 à 75 % en poids sur la base du poids total de l'électrocatalyseur. La couche de catalyseur a une charge de métal du groupe du platine dans la plage de et comprenant de 0,6 à 1,0 mg de métal du groupe du platine par cm2 de la zone géométrique de la couche de catalyseur.
PCT/GB2022/053094 2021-12-06 2022-12-06 Couche de catalyseur Ceased WO2023105204A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB2405555.0A GB2626873A (en) 2021-12-06 2022-12-06 Catalyst layer

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB2117596.3A GB202117596D0 (en) 2021-12-06 2021-12-06 Catalyst layer
GB2117596.3 2021-12-06

Publications (1)

Publication Number Publication Date
WO2023105204A1 true WO2023105204A1 (fr) 2023-06-15

Family

ID=79269599

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2022/053094 Ceased WO2023105204A1 (fr) 2021-12-06 2022-12-06 Couche de catalyseur

Country Status (2)

Country Link
GB (2) GB202117596D0 (fr)
WO (1) WO2023105204A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025017297A1 (fr) * 2023-07-18 2025-01-23 Johnson Matthey Hydrogen Technologies Limited Procédé de préparation d'une couche de membrane conductrice d'ions
WO2025017296A1 (fr) * 2023-07-18 2025-01-23 Johnson Matthey Hydrogen Technologies Limited Procédé de préparation d'une couche de catalyseur
US12586796B2 (en) * 2022-04-28 2026-03-24 Toyota Jidosha Kabushiki Kaisha Catalyst for fuel cell

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0631337A2 (fr) 1993-06-18 1994-12-28 Tanaka Kikinzoku Kogyo K.K. Composition d'électrolyte solide à base de polymères
WO2000024074A1 (fr) 1998-10-16 2000-04-27 Johnson Matthey Public Limited Company Procede d'obtention d'une membrane electrolyte de polymere solide
US6936370B1 (en) * 1999-08-23 2005-08-30 Ballard Power Systems Inc. Solid polymer fuel cell with improved voltage reversal tolerance
US20090208780A1 (en) * 2008-02-19 2009-08-20 Cabot Corporation High surface area graphitized carbon and processes for making same
WO2013045894A1 (fr) 2011-09-28 2013-04-04 Johnson Matthey Fuel Cells Limited Catalyseur à support de charbon

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0631337A2 (fr) 1993-06-18 1994-12-28 Tanaka Kikinzoku Kogyo K.K. Composition d'électrolyte solide à base de polymères
WO2000024074A1 (fr) 1998-10-16 2000-04-27 Johnson Matthey Public Limited Company Procede d'obtention d'une membrane electrolyte de polymere solide
US6936370B1 (en) * 1999-08-23 2005-08-30 Ballard Power Systems Inc. Solid polymer fuel cell with improved voltage reversal tolerance
US20090208780A1 (en) * 2008-02-19 2009-08-20 Cabot Corporation High surface area graphitized carbon and processes for making same
WO2013045894A1 (fr) 2011-09-28 2013-04-04 Johnson Matthey Fuel Cells Limited Catalyseur à support de charbon

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
F. BERTAUTP. BLUM, C.R. ACAD. SCI. PARIS, vol. 229, 1949, pages 666
J. POWER SOURCES, vol. 242, 2013, pages 244 - 255
LAGARTEIRA TIAGO ET AL: "The role of Pt loading on reduced graphene oxide support in the polyol synthesis of catalysts for oxygen reduction reaction", INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, ELSEVIER, AMSTERDAM, NL, vol. 45, no. 40, 27 February 2020 (2020-02-27), pages 20594 - 20604, XP086235478, ISSN: 0360-3199, [retrieved on 20200227], DOI: 10.1016/J.IJHYDENE.2020.02.022 *
R.W. CHEARYA. COELHO, J. APPL. CRYST., vol. 25, 1992, pages 109 - 121
TOPAS V5.0: GENERAL PROFILE AND STRUCTURE ANALYSIS SOFTWARE FOR POWDER DIFFRACTION DATA, BRUKER AXS, vol. 6, 2003, pages 257

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12586796B2 (en) * 2022-04-28 2026-03-24 Toyota Jidosha Kabushiki Kaisha Catalyst for fuel cell
WO2025017297A1 (fr) * 2023-07-18 2025-01-23 Johnson Matthey Hydrogen Technologies Limited Procédé de préparation d'une couche de membrane conductrice d'ions
WO2025017296A1 (fr) * 2023-07-18 2025-01-23 Johnson Matthey Hydrogen Technologies Limited Procédé de préparation d'une couche de catalyseur

Also Published As

Publication number Publication date
GB2626873A8 (en) 2024-09-18
GB2626873A (en) 2024-08-07
GB202405555D0 (en) 2024-06-05
GB202117596D0 (en) 2022-01-19

Similar Documents

Publication Publication Date Title
EP3465806B1 (fr) Catalysateur
CN108475791B (zh) 催化剂
KR102225982B1 (ko) 촉매
EP4374435B1 (fr) Catalysateur de réaction de dégagement d'oxygène
WO2023105204A1 (fr) Couche de catalyseur
KR20210114052A (ko) 연료 전지용 척매
US12308445B2 (en) Methods of preparing catalyst materials
KR102765489B1 (ko) 촉매화된 막
EP4374436B1 (fr) Catalyseur de réaction de dégagement d'oxygène
EP4179584B1 (fr) Préparation d'un catalyseur
WO2025104436A1 (fr) Membrane conductrice d'ions revêtue de catalyseur
GB2643863A (en) Fuel cell catalyst layer
WO2026022491A1 (fr) Couche de catalyseur de pile à combustible

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22822633

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 202405555

Country of ref document: GB

Kind code of ref document: A

Free format text: PCT FILING DATE = 20221206

WWE Wipo information: entry into national phase

Ref document number: 2405555.0

Country of ref document: GB

NENP Non-entry into the national phase

Ref country code: DE

WWP Wipo information: published in national office

Ref document number: 2405555.0

Country of ref document: GB

122 Ep: pct application non-entry in european phase

Ref document number: 22822633

Country of ref document: EP

Kind code of ref document: A1