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
  • H01M4/88—Processes of manufacture
  • H01M4/8803—Supports for the deposition of the catalytic active composition
  • H01M4/8807—Gas diffusion layers
• • 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
• • 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
• • 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
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/8605—Porous electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/88—Processes of manufacture
  • H01M4/8825—Methods for deposition of the catalytic active composition
  • H01M4/886—Powder spraying, e.g. wet or dry powder spraying, plasma spraying
• • 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
• • 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
  • H01M4/921—Alloys or mixtures with metallic elements
• • 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
  • H01M4/923—Compounds thereof with non-metallic elements
• • 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

• the invention relates to a method for producing a gas diffusion electrode, in particular for the electrolysis of an aqueous solution of hydrogen chloride.
• a gas diffusion electrode for the electrolysis of aqueous solutions of hydrogen chloride generally has the following structure:
• An electrically conductive support for example a carbon or metal mesh, is provided with a gas diffusion layer, consisting, for example, of an acetylene black-polytetrafluoroethylene mixture, Mistake.
• a catalyst layer consisting of a catalyst-polytetrafluoroethylene mixture is applied to this support provided with a gas diffusion layer.
• the catalyst is usually sorbed on soot (eg Nulcan ® XC72). If the gas diffusion electrode operated in direct contact with an ion exchange membrane, so it is often additionally conducting with a layer of ionomer protons, for example Nation ®, provided, in order to achieve a better connection to the ion exchange membrane.
• Methods are known for applying the gas diffusion layer and the catalyst layer to a support, in which thickened liquids or pasty masses are applied by hand, for example by spatula, or by machine, for example by rolling, and then sintered at temperatures of approx. to stabilize the Teflon structure and thus the pore structure of the layers.
• a Nafion ® layer can only be applied after sintering.
• a disadvantage of the known processes is that they are relatively expensive, since the layers have to be applied individually and with high uniformity, with comparatively large amounts of catalyst being used.
• sintering is time-consuming because it takes several hours and also has the disadvantage that microcracks form on the surface of the catalyst layer.
• hydrochloric acid (HCl) electrolysis relatively high levels of corrosion can be observed with all noble metal-containing catalysts. The corrosion is caused by the chlorine formed in the electrolysis operation, which diffuses through the ion exchange membrane from the anode half cell into the cathode half cell.
• the gas diffusion electrodes produced with the aid of methods according to the prior art show comparatively high corrosion, which is why the gas diffusion electrodes have to be replaced comparatively frequently. As a result, the cost of materials and the effort for removing and installing the gas diffusion electrodes is undesirably high.
• the object of the present invention is to provide a method for producing a gas diffusion electrode which does not have the disadvantages mentioned.
• the procedure should be as simple as possible, i.e. in as few steps as possible, and the amount of catalyst used should be as low as possible.
• the electrochemical activity of the gas diffusion electrodes during operation of the electrolytic cell should be at least as good as gas diffusion electrodes manufactured by known methods, i.e. the operating voltage should be as low as possible and long-term stability as high as possible.
• the invention relates to a method for producing a gas diffusion electrode, in particular for the electrolysis of an aqueous solution of hydrogen chloride, characterized by
• An advantage of the process according to the invention is that spraying on a dispersion of the catalyst is easier compared to the processes known from the prior art. It is not necessary to sinter the sprayed dispersion. In addition, the amount of catalyst used when spraying on a dispersion of the catalytically active component is up to a factor of 4 less.
• the noble metal-containing catalyst is preferably a compound of the general formula MeI x MeII (6 - x) E 8 , where Mel is molybdenum, Mell is ruthenium, platinum, rhenium, rhodium or palladium and E is sulfur, selenium or chlorine , X is from 0 to 6 and can be integer or non-integer.
• the compound is particularly preferably a Chevrel phase, ie ternary molybdenum chalcogenides.
• the catalyst is more preferably a platinum-ruthenium alloy.
• other binary, ternary or quaternary platinum alloys with metals of VI. and VIII. Subgroup are used.
• the noble metal-containing catalyst can be used as such, i.e. in substance.
• the catalyst is preferably applied to an electrically conductive, chemically inert support material with a high specific surface area, preferably carbon black.
• the catalyst is preferably applied to the support material by sorption.
• the sorbed catalyst is also referred to below as
• the electrically conductive carrier is preferably a fabric, braid, net or fleece made of carbon, metal or sintered metal.
• the metal or sintered metal must be resistant to hydrochloric acid. These include, for example, titanium, hafnium, zirconium, niobium, tantalum and some Hastelloy alloys.
• the electrically conductive carrier is optionally provided with a coating composition which contains an acetyl egg rass-polytetrafluoroethylene mixture.
• Coating material can be applied to the electrically conductive carrier, for example, by filling and then sintered at temperatures of approx. 340 ° C.
• This coating mass serves as a gas diffusion layer.
• the gas diffusion layer is significantly more hydrophobic and controls the mass transfer: on the one hand, gas becomes non-wettable
• Pores directed to the catalyst layer on the other hand water of reaction is transported from the catalyst layer into the rear space via wettable pores.
• the gas diffusion layer can be applied over the entire surface of the electrically conductive carrier. It can also be completely or partially embedded in the open-pore structure of the carrier, a fabric, braid, mesh or the like.
• the electrically conductive carrier provided with a gas diffusion layer is also referred to below as the substrate.
• Such an electrically conductive carrier made of a carbon fleece, which is provided with a gas diffusion layer made of an acetylene black-polytetrafluoroethylene mixture, is commercially available, for example from SGL Carbon Group, type GDL 10 AC.
• a dispersion of the catalyst and a proton-conducting ionomer in an organic solvent is sprayed onto the electrically conductive carrier or onto the substrate, ie the electrically conductive carrier provided with the coating material.
• the organic solvent is then removed in a second step b). This is done for example by drying, preferably at a temperature of 0 to 115 ° C, particularly preferably at a temperature of 10 to 20 ° C.
• the dispersion according to step a) is sprayed over the entire surface.
• the application of the dispersion must be uniform in relation to the area loading. A mechanical bond between the dispersion and the gas diffusion layer must also be ensured.
• the layer thickness is preferably at most 10 ⁇ m, particularly preferably 5 to 8 ⁇ m.
• Suitable proton-conducting ionomer is, for example, National R , a polytetrafluoroethylene modified with sulfonic acid groups, which is commercially available, for example as a dispersion in alcohol, preferably isopropanol.
• Organic solvents with a boiling point of preferably 50 to 115 ° C. are suitable for the dispersion of the catalyst and the proton-conducting ionomer.
• Isopropanol is preferably used.
• the dispersion is prepared by stirring the catalyst in the organic solvent. It is crucial to wet the catalyst as completely as possible. A stirrer with high shear force is therefore preferably used as the dispersing device.
• the proton-conducting ionomer in particular Nation® , can be added simultaneously with the catalyst or subsequently. The ratio of the mass of the catalyst to the mass of the proton-conducting ionomer in the
• Dispersion is preferably from 1: 1 to 15: 1, particularly preferably from 3: 1 to 6: 1.
• the volume of the organic solvent in relation to the mass of the catalyst can be such that the solvent is just sufficient to obtain a sprayable dispersion.
• the organic solvent can also be used in excess, the dispersion then being left to stand after the stirring in order to settle. The clear supernatant is then decanted and discarded.
• a dispersion of a proton-conducting ionomer is dissolved in an organic solution. sprayed on medium.
• the organic solvent is then removed in a step d). This is preferably done by drying at a temperature of 0 to 115 ° C, particularly preferably from 10 to 20 ° C.
• the organic solvent for the dispersion used in step c) is isopropanol. Alternatively, other organic solvents can also be used. Spraying takes place over the entire surface and uniformly.
• the dispersion according to a) and / or the dispersion of the proton-conducting ionomer according to c) is sprayed on several times, in particular 2 to 5 times, with the organic solvent according to b) and / after each spraying first or d) is removed.
• the number of spraying operations depends on the desired loading of the carrier and the spray characteristics of the spraying device.
• Drying takes place at temperatures from 0 to 115 ° C.
• the gas diffusion electrodes showed no differences in the cell voltage depending on the temperature and the duration of the drying process during operation of the electrolysis cell.
• drying is crucial in order to increase the stability of the catalyst layer and the service life of the gas diffusion electrodes.
• Such a simple drying process is advantageous over sintering because it is less time-consuming and the materials used are less stressed. In particular, there is no microcracking on the drying
• Gas diffusion electrodes are preferably produced which have a loading with the noble metal of the catalyst of 0.5 g / m 2 to 10 g / m 2 . If the catalyst is applied to a carrier material, especially carbon black, the optimal catalyst loading is based on the noble metal concentration on the carbon black dependent. The optimum loading for a catalyst containing 30% by weight of noble metal is 1.5 to 4 g / m 2 noble metal.
• gas diffusion electrodes produced by the method according to the invention are their lower corrosion.
• the corrosion in the gas diffusion electrodes produced by the method according to the invention is lower by a factor of 3 to 5 compared to the gas diffusion electrodes manufactured according to the prior art. This applies in particular to the start-up phases of the electrolysis, while the free chlorine which diffuses from the anode half cell through the ion exchange membrane into the cathode half cell can be detected in the area of the gas diffusion electrodes.
• Molybdenum to ruthenium to selenium corresponded to the amounts used, so that there was no volatilization of the carbonyls used.
• the catalyst sorbed on Vulcan ® XC72 was separated from the xylene used as the solvent for the preparation. There was no further treatment of the catalyst. 2 g of the sorbed on Vulcan XC72 ® catalyst were dispersed in 100 ml of isopropanol, and, in a commercial solution of Dupont, treated with 0.5 g Nafion ®. The dispersion was stirred vigorously and left to stand overnight. An Ultraturrax C25 from IKA Labortechnik (Germany) was used as the stirring tool. The clear supernatant was then decanted and discarded. The remaining dispersion was sprayed onto a substrate (step a)).
• the substrate consisted of a carbon fabric which was provided on one side with a gas diffusion layer made of 50% by weight of acetylene black and 50% by weight of Teflon with a load of 40 g / m 2 .
• a gas diffusion layer made of 50% by weight of acetylene black and 50% by weight of Teflon with a load of 40 g / m 2 .
• the substrate was loaded with a total of 12 g / m 2 catalyst mass, corresponding to 1.0 g / m 2 Ru. After each spraying process, drying was carried out at a temperature of 50 ° C. for 30 minutes (step b)).
• Step c) was then forwarded in three passes Nafion ® with a loading of a total of 7.4 g / m 2 sprayed. After each spraying, the mixture was dried at 50 ° C.
• step d sintering was carried out at 115 ° C. for one hour.
• the gas diffusion electrode produced in this way was used in an electrolysis cell for the electrolysis of a 14% by volume technical hydrochloric acid at 60 ° C.
• the anode gap, ie the distance between the anode and the ion exchange membrane was 3 mm.
• Nafion ® 324 was used as the ion exchange membrane. Pure oxygen was used to operate the gas diffusion electrode.
• the gas diffusion electrode showed an operating voltage of 1.38 volts at a current density of 5 kA / m 2, an operating voltage of 1.02 volts at 2 kA / m 2 and a voltage of 1.71 volts at 8 kA / m 2 .
• Hydrochloric acid showed, e.g. with gas diffusion electrodes with platinum as a catalyst.
• Example 2 g of a commercially available on Vulcan XC72 ® sorbed catalyst comprising 20 wt.% Of a platinum-ruthenium alloy contained with an atomic ratio of 50:50 was dispersed in analogy to Example 1, in isopropanol. As described in Example 1, the dispersion was sprayed onto the substrate in three layers, the organic layer being sprayed on after each layer
• Example 2 Solvent as described in Example 1 was removed. A substrate analogous to Example 1 was used. The loading of the substrate with the catalyst applied to Vulcan ® XC72 was 13.2 g / m 2 . Nafion® was sprayed onto this coating with the catalyst in two layers, the total load being 8.3 g / m 2 . After spraying the first Nafion®
• the gas diffusion electrode showed an operating voltage of 1.36 V when the electrolysis cell was operating at a current density of 5 kA / m 2, an operating voltage of 1.0 V at a current density of 2 kA / m 2 and at Current density of 8 kA / m 2 a voltage of 1.66 V.
• the gas diffusion electrode surprisingly proved to be inert to a period of 22 days

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• Manufacturing & Machinery (AREA)
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• Organic Chemistry (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Catalysts (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)

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• 2003
  • 2003-09-13 AU AU2003266386A patent/AU2003266386A1/en not_active Abandoned
  • 2003-09-13 PL PL03375012A patent/PL375012A1/xx not_active Application Discontinuation
  • 2003-09-13 BR BR0314724-0A patent/BR0314724A/pt not_active IP Right Cessation
  • 2003-09-13 WO PCT/EP2003/010207 patent/WO2004032263A2/de not_active Application Discontinuation
  • 2003-09-13 JP JP2004540618A patent/JP2006500475A/ja active Pending
  • 2003-09-13 CN CNA038229285A patent/CN1685545A/zh active Pending
  • 2003-09-13 EP EP03798905A patent/EP1547175A2/de not_active Withdrawn
  • 2003-09-13 KR KR1020057005157A patent/KR20050051670A/ko not_active Application Discontinuation
  • 2003-09-17 US US10/663,835 patent/US20040124079A1/en not_active Abandoned
• 2006
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