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
• • 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
• • 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
  • H01M4/8828—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
  • H01M4/88—Processes of manufacture
  • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
  • H01M4/8882—Heat treatment, e.g. drying, baking
• • 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
  • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
  • H01M4/8882—Heat treatment, e.g. drying, baking
  • H01M4/8885—Sintering or firing
• • 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
  • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
  • H01M4/8896—Pressing, rolling, calendering
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0232—Metals or alloys
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0234—Carbonaceous material
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0241—Composites
  • H01M8/0245—Composites in the form of layered or coated products
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
  • H01M8/026—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant characterised by grooves, e.g. their pitch or depth
• • 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 dimensionally stable gas diffusion electrode consisting of at least one electrically conductive catalyst support material for receiving the coating material containing catalyst material and an electrical connection, and a method for producing the electrode.
• the catalyst support material is a woven fabric, fleece, sintered metal, foam or felt made of electrically conductive material, an expanded metal plate or a metal plate provided with a plurality of openings, on which the catalyst material contains
• Coating composition is applied, and which is mechanically and electrically conductively connected to a gas-permeable metallic base plate, in particular made of nickel or a nickel / silver alloy or an alkali-resistant metal alloy. If the catalyst support material has sufficient inherent rigidity, the use of a base plate can be dispensed with and the catalyst support material provided with coating material containing catalyst material can be installed directly in an electrochemical reaction apparatus.
• Gas diffusion electrodes are used in different arrangements for electrochemical processes.
• the gas diffusion electrodes as hydrogen consumption anode and oxygen consumption cathode (SVK) are placed directly on the membrane.
• SVK oxygen consumption cathode
• HC1 electrolysis with an oxygen consumable cathode this also lies directly on the membrane.
• Electrode is free with a usual gas pocket height of 15 - 35 cm between caustic soda and oxygen. Since a limited, but still present, height-dependent differential pressure is applied via the SVK, which is relatively elastic, similar to a membrane, it must be supported with spacers against bulging in the direction of the membrane or on the other side in the direction of the gas pocket. Uncontrolled bulging of the SVK in the direction of the membrane causes a reduction in the catholyte gap up to the contact between the SVK and the membrane. This results in a disturbance in the flow of lye, combined with an uneven concentration distribution and possible damage to the membrane. Possibly through the SVK passing oxygen gas bubbles can not withdraw unhindered and collect in places with a greatly reduced
• the effects described result in an increased k-factor, i.e. an excessive increase in the operating voltage depending on the increase in the current density and thus an excessive specific energy consumption.
• the spacer between the electrode and membrane in particular has repeatedly led to problems. Local contact points combined with structural movements in the electrolysis cell occasionally lead to chafing points on the membrane, which can lead to leakage over a long period of operation. Accordingly, the SVK was also burdened with pressure points, which could certainly lead to damage if it were to operate for years. In addition, the spacers shield both electrode and membrane surfaces, which also leads to high current densities and thus to high voltages and high specific energy consumption. A solution was therefore sought to be able to dispense with such spacers.
• the object of the invention is to provide a stable gas diffusion electrode and a method for its production which does not have the disadvantages mentioned.
• the solution is to apply the coating material containing catalyst material according to the basically known wet or dry calendering process to a metallic, single or multi-layer scrap structure with the structure described below.
• the invention relates to a dimensionally stable gas diffusion electrode consisting of at least one electrically conductive catalyst support material for receiving a coating material containing catalyst material, in particular mixtures of finely divided silver or finely divided silver oxide or mixtures of silver and silver oxide and Teflon powder or of mixtures of finely divided Silver or silver oxide or mixtures of silver and silver oxide, carbon and Teflon powder, and an electrical connection, characterized in that the catalyst support material is a fabric, fleece, sintered metal, foam or felt made of electrically conductive material, an expanded metal plate or is provided with a plurality of openings metal plate on which the coating material containing the catalyst material is applied, and which has a sufficient flexural strength, so that an additional stiffening by using an additional base plate can be dispensed with, or with a gas-permeable rigid metallic base plate or a rigid fabric or expanded metal, in particular made of nickel or its alloys or alkali-resistant
• Metal alloys, mechanically and electrically conductive is firmly connected.
• the open structure serving as catalyst support material consists in particular of a fine wire mesh or a corresponding fine expanded metal, filter screen, felt, foam or sintered material, into which the coating material containing the catalyst material is clamped during rolling.
• This open structure is in In one embodiment, before the coating material containing catalyst material is pressed in or rolled in, it is already connected to the entirely open, but more compact and rigid substructure in a metallic manner, for example by sintering.
• this substructure is that of an abutment when the coating material containing the catalyst material is pressed in, which in this case can also spread into structure-related gaps between the two layers and thus clamp together even better.
• the metal for the base plate is preferably selected from the series nickel or an alkali-resistant nickel alloy, in particular nickel with silver, or nickel, which is coated with silver, or from an alkali-resistant metal alloy.
• a rigid foam or a rigid sintered structure or a perforated or slotted plate made of a material can be used as the base plate
• Nickel, alkali-resistant nickel alloy or alkali-resistant metal alloy in particular nickel with silver, or nickel, which is coated with silver, can be used.
• the coating material which has been rolled out into a fur and contains catalyst material is rolled directly into the basic structure, which at the same time has the function of a catalyst support material. An additional catalyst support material is therefore not used.
• the catalyst support material preferably consists of carbon, metal, in particular nickel or nickel alloys or an alkali-resistant metal alloy.
• the base plate preferably has a plurality of openings, in particular slots or bores, for improved passage of reaction gas.
• the openings are preferably at most 2 mm, in particular at most 1.5 mm wide.
• the slots can have a length of up to 30 mm.
• the pores When using a foam or a porous sintered structure, the pores have an average diameter of preferably at most 2 mm.
• the structure is characterized by high rigidity and bending strength.
• a foam or sintered metal body is used as the catalyst support material, an edge provided for connecting the electrode to an electrochemical reaction apparatus being pressed together in order to achieve the required gas / liquid tightness.
• a preferred variant of the gas diffusion electrode is characterized in that the base plate has an opening-free peripheral edge of at least 5 mm, which is used to attach the electrode, in particular by welding or soldering, or with screws or rivets or clamps or by using electrically conductive adhesive to the Edge of the one to be connected to the electrode
• a selected form of the gas diffusion electrode is characterized in that the catalyst support material and the coating material containing the catalyst material are connected to one another by dry calendering.
• a preferred variant of the gas diffusion electrode is designed in such a way that the catalyst support material and the coating material containing the catalyst material are applied to the catalyst support material by pouring or wet rolling the coating material containing water and possibly organic solvents (for example alcohol) and are connected by subsequent drying, sintering and possibly compacting is.
• the coating material containing water and possibly organic solvents for example alcohol
• an additional electrically conductive gas distributor fabric in particular made of carbon, is provided between the base plate and the catalyst support material or metal, in particular nickel, or an alkali-resistant nickel alloy, in particular with silver or made of nickel, which is coated with silver, or an alkali-resistant metal alloy.
• Base plate on a flat recess for receiving the gas distribution fabric.
• gas diffusion electrode has proven to be particularly suitable in which the layer of catalyst support material and coating material containing catalyst material in the edge region of the electrode is connected to the edge of the base plate in a gas-tight manner all around.
• the gas-tight connection can be made, for example, by sealing or, if necessary, ultrasonically supported, rolling down.
• a peripheral edge zone is strongly pressed in order to obtain a gas-tight edge area.
• the gas diffusion electrode preferably has an edge without openings or an edge sealed by pressing a porous structure and is gas-tight and electrically conductive at this opening-free edge with an electrochemical reaction apparatus, for example by means of welding, soldering, screwing, riveting, clamping or using alkali-resistant, electrical conductive adhesive bonded.
• the opening-free edge is preferably silver-free. If, however, the gas diffusion electrode is connected to the electrochemical reaction apparatus by means of screws, rivets, clamps or the use of electrically conductive adhesive, the opening-free edge is preferably silver-containing.
• Another object of the invention is a method for producing the gas diffusion electrode according to the invention, by sintering the catalyst support material with a base plate which is provided with a multiplicity of openings, applying the powdery or fibrous coating composition which may contain rolled catalyst material in a previous work step
• the invention also relates to an alternative method for producing a gas diffusion electrode by applying a thin to dough-like mixture of catalyst with water and possibly an organic solvent, for example alcohol, with a solvent content between 0 to 100% and a solids content between 5 to 95% with rolling or spatulas or pouring the mixture, drying and sintering at a higher temperature, in particular at least 100 ° C. and at most 400 ° C., under protective gas, in particular nitrogen, carbon dioxide, noble gas or a reducing medium, particularly preferably argon, neon, krypton, Butane and possibly further rolling the sintered composite at a pressure of at least 3-10 ⁇ Pascal.
• an organic solvent for example alcohol
• the surface of the catalyst support material is preferably provided with a silver layer, in particular by electrodeposition or electroless plating.
• a gas distributor fabric is applied to the base plate and sintered to the base plate before the catalyst support material is applied.
• a particularly preferred method is characterized in that the catalyst carrier material, gas distributor and base plate are sintered simultaneously.
• the opening division of the two layers should be suitably matched to one another. Adequate drainage of condensate or caustic soda must also be ensured to prevent the gas transport channels from being blinded.
• this structure supplies the catalytically active layer with oxygen through its openings and forms the rigid substructure which makes this gas diffusion electrode dimensionally and deformably stable.
• the slightly protruding edge of the base structure which is preferably deeper than the catalyst support material structure and during rolling, can be used.
• the catalyst material contains tendency coating composition can be protected in a suitable manner from the fluoropolymers, are used. It is particularly advantageous if this part is left open during the stamping of the openings in the form of holes, slots, etc., ie remains massive and lateral escape of the oxygen can thus be prevented. An escape of oxygen from the boundary between the two
• Layers can be avoided by suitably rolling down a narrow, catalyst-filled edge strip of the top layer onto the substructure, which should no longer be slotted here or should otherwise be covered with metal and sealed.
• edge strip for example, the use of an ultrasonically excited, rotating roller head has proven successful.
• the porous structure is strongly compressed in a peripheral edge area to prevent the escape of oxygen in the edge area.
• the strong compacting causes the formation of a gas-tight structure.
• the type of catalyst applied in particular after the dry calendering process, but also after the wet calendering process and the spatula process, allows used catalyst layers to be removed by vigorous blowing or spraying, so that the metallic support structure can be coated again.
• Another object of the invention is an electrochemical gas diffusion cell having a gas diffusion electrode according to the invention as described above.
• the electrochemical gas diffusion cell can be designed with permanently installed but also with removable gas pockets.
• Fig. 1 is a diagram of the structure of a gas diffusion electrode according to the invention
• Fig. 2 shows the cross section through the electrode of FIG. 1 along line A-A
• FIG. 3 shows a diagram of a variant of the electrode according to FIG. 1 with an additional gas distribution fabric 10
• Fig. 4 shows the cross section through the electrode of Fig. 3 along line B-B
• the base plate (1) consists of 1.5 mm thick nickel sheet with openings (slots) (2) 1.5 mm wide and 15 mm long (from Fiedler / D).
• the distribution of the slots is chosen so that their distance from each other is 5 mm in the longitudinal direction and 2 mm in the transverse direction.
• the adjacent longitudinal rows of the slots are shifted against each other by half a period, so that the slot is adjacent to the distance.
• This basic structure has an unslit edge (3).
• a nickel wire mesh (4) with a wire diameter of 0.14 mm and a mesh size of 0.5 mm acts as a support structure for the activation.
• the wire mesh is flush with the edge zone. This arrangement is sintered at temperatures between 800-1200 ° C; you get a coherent structure.
• the side carrying the wire is silver-plated.
• the unslit edge zone (3) is covered with a suitable material such as wax, lacquer, adhesive tape or the like.
• the complete electrode structure is then coated with a coating material (5) which has previously been rolled into a film (“fur”) and consists of 85% carbon black (Vulcan XC-72, 10% Ag), 15% HOSTAFLON TF 2053 (PTFE) in a coating thickness of 500 g / m 2 , which is connected to the wire mesh (4) by rolling, pressing or the like.
• the edge area (6) is used to achieve a sufficient level
• the integration into the electrochemical reaction apparatus takes place, for example, by welding, soldering, screwing, clamping, riveting or using electrically conductive adhesive or the like in the solid edge zone (3).
• Example 2 Production of a two-layer dimensionally stable gas diffusion electrode: The structure is similar to that of Example 1 except for the use of a different application method for the coating material containing catalyst material and the application of an additional uncatalyzed gas diffusion layer:
• the side carrying the wire is silvered without current.
• the unslit edge zone is covered on both sides by means of a suitable material such as wax, lacquer, adhesive tape or the like.
• the electrode structure is then coated on the non-wire-bearing side with a gas diffusion layer previously rolled out to form a fur, consisting of 70% carbon black (Vulcan XC-72, uncatalyzed), 30% HOSTAFLON TF 2053 (PTFE) in a coating thickness of 750 g / m 2 , which is connected to the slotted sheet structure by rolling, pressing or the like.
• the wire-bearing side of the electrode structure is mixed with a mixture of 70% carbon black (Vulcan XC-72, 10% Ag / PTFE mixture (85% / 15%)) and 30% previously mixed to a pasty mass.
• spatula Spread isopropanol
• a tempering step at 250 ° C / lh follows to solidify the electrode.
• the electrode is integrated into the electrochemical reaction apparatus as in Example 1.
• Example 2 Production of a two-layer dimensionally stable gas diffusion electrode: The structure is similar to that of Example 1 except for the use of a different support material for the catalyst: a fine expanded metal of the type 5-M-5-050 Pulled (thickness of the starting material: 0.127 mm, web width: 0.127 mm, LWD: 1.27 mm, from DELKER / USA).
• a fine expanded metal of the type 5-M-5-050 Pulled thickness of the starting material: 0.127 mm, web width: 0.127 mm, LWD: 1.27 mm, from DELKER / USA.
• the use of expanded metal results in particularly strong interlocking between the coating material containing catalyst material and catalyst support material.
• the base plate of the electrode consists of a 2 mm thick slotted plate (7) with openings (slits) (8) 1.5 mm wide and 25 mm long (from Fiedler / D).
• the distribution of the slots is selected so that their distance from each other is 5 mm in the longitudinal direction and 2 mm in the transverse direction.
• the adjacent longitudinal rows of the slots are shifted against each other by half a period, so that the slot is adjacent to the distance.
• This basic structure has an unslit edge (9) which does not have to be at the same height as the slotted contact surface - the use of a higher edge has proven to be advantageous for the sealing.
• An inserted wire mesh (10) with a 0.5 mm wire diameter and 0.8 mm mesh size acts as a gas distributor.
• a fine nickel wire mesh with 0.14 mm wire diameter and 0.5 mm mesh size is placed on this structure (Fa. Haver and Boecker / D) (11), which is flush with the edge zone in the case outlined in FIG. 3.
• This arrangement is sintered at temperatures between 800-1200 ° C; you get a coherent structure.
• the side carrying the wire is silvered without current.
• the higher, unslit edge zone (9) is made using a suitable material such as e.g. Wax, varnish, adhesive tape etc. covered.
• a suitable material such as e.g. Wax, varnish, adhesive tape etc. covered.
• the complete electrode structure is then coated with a coating material which has previously been rolled out to form a film (“fur”)
• Ni-5-050 Pulled (thickness of the starting material: 0.127 mm, web width: 0.127 mm, LWD: 1.27 mm, from DELKER / USA).
• the use of expanded metal results in a particularly intensive interlocking between the catalyst support material and the coating material containing catalyst material.
• Opening diameter of 0.3 mm and a triangular division of 0.6 mm related (from Fiedler / D).
• the structure is similar to that of Example 4 except for the use of a different catalyst support material and application method for the coating material containing the catalyst material: it becomes an opaque, sintered nickel felt with a thickness of 0.3 mm (from Nitech / F) used as catalyst support material.
• This absorbent structure is coated with a pourable mixture of 36% carbon black (Vulcan XC-72, 10% Ag), 64% HOSTAFLON TF 5033 suspension (10% PTFE) in a coating thickness of 250 g / m 2 , at 95 ° C dried and compacted by rolling to achieve sufficient gas tightness.
• a tempering step at 250 ° C / lh follows to solidify the electrode.
• the integration of the electrode in the electrochemical reaction apparatus takes place as described in Ex. 4.
• the base plate consists of 5 mm thick nickel foam (Dunlop / USA). The average pore diameter is 1 mm, the gap volume is 80%.
• This basic structure has a non-porous edge before the coating process is completed; a support structure is not used.
• the side intended for a later coating is silver-plated.
• the edge zone is covered with a suitable material such as e.g. Wax, varnish, adhesive tape etc. covered.
• the complete electrode structure is then coated with a coating material which has previously been rolled out to form a film (“fur”) and consists of 85% carbon black (Vulcan XC-72, 10% Ag), 15% HOSTAFLON TF 2053 (PTFE) in a coating thickness of 500 g / m occupied, which by rolling, pressing or the like is connected to the foam structure. After removing those covering the edge area
• the edge area is pressed together to achieve a sufficient gas tightness to a thickness of 1 mm - the electrode is now ready for installation.
• the integration into the electrochemical reaction apparatus takes place, for example, by welding, soldering, screwing, clamping, riveting or using electrically conductive adhesive or the like. in the massive edge zone.
• the base plate consists of 1.5 mm thick nickel sheet with slots 1.5 mm wide and 15 mm long (from Fiedler / D).
• the distribution of the slots is chosen so that their distance from each other is 5 mm in the longitudinal direction and 2 mm in the transverse direction.
• the adjacent longitudinal rows of the slots are shifted against each other by half a period, so that the slot is adjacent to the distance.
• This basic structure has an unslit edge; a support structure is not used.
• the side intended for a later coating is silver-plated.
• the unprotected edge zone is covered with a suitable material such as wax, lacquer, adhesive tape or the like.
• the complete electrode structure is then coated with a coating composition which has previously been rolled out to form a catalyst material and consists of 85% carbon black (Vulcan XC-72, 10% Ag), 15% HOSTAFLON TF 2053 (PTFE) in a coating thickness of 500 g / m 2 , which is connected to the slotted plate by rolling, pressing or the like.
• PTFE HOSTAFLON TF 2053
• the side intended for the subsequent coating is silvered without current.
• the unslit edge zone is covered on both sides by means of a suitable material such as wax, lacquer, adhesive tape or the like.
• the Eleldroden structure is then coated on the non-silvered side with a gas diffusion layer previously rolled out to form a fur, consisting of 70% carbon black (Vulcan XC-72, uncatalyzed), 30% HOSTAFLON TF 2053 (PTFE) in a coating thickness of 750 g / m 2 , which by
• Example 9 The application of the coating material containing the catalyst material and integration of the electrode into the electrochemical reaction apparatus is carried out as in Example 9.
• Example 1 The gas diffusion electrode described in Example 1 was installed in an electrolysis cell (see FIG. 5) which has a conventional anode half-cell (18) with a membrane (14).
• the design of the cathode half-cell differs significantly from the structure used in conventional cells - it consists of
• Catholyte gap (15), oxygen consumption cathode (SVK) (16) and gas space (17).
• the catholyte gap (15) has a conventional function; the, opposite the
• the SVK (16) has a size of 18 cm x 18 cm and was operated over a period of 100 days at a stable cell voltage of 1.98 volts; the maximum deflection measured under operating conditions was 0.5 mm.

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