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WO1996035004A1 - Cellule electrochimique a repartiteur de courant resistant au developpement oxydique - Google Patents

Cellule electrochimique a repartiteur de courant resistant au developpement oxydique Download PDF

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Publication number
WO1996035004A1
WO1996035004A1 PCT/US1995/016033 US9516033W WO9635004A1 WO 1996035004 A1 WO1996035004 A1 WO 1996035004A1 US 9516033 W US9516033 W US 9516033W WO 9635004 A1 WO9635004 A1 WO 9635004A1
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WIPO (PCT)
Prior art keywords
metal
current
cathode
anode
electrochemical cell
Prior art date
Application number
PCT/US1995/016033
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English (en)
Inventor
David Lee Reichert
Charles Collmar Seastrom
Vinci Martinez Felix
Clarence Garlan Law, Jr.
James Arthur Trainham, Iii
John Scott Newman
Douglas John Eames
Original Assignee
E.I. Du Pont De Nemours And Company
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Application filed by E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Priority to AU44201/96A priority Critical patent/AU4420196A/en
Publication of WO1996035004A1 publication Critical patent/WO1996035004A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • 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
    • 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
    • C25B1/14—Alkali metal compounds
    • C25B1/16—Hydroxides
    • 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
    • C25B1/22—Inorganic acids
    • 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
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • 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
    • 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
    • C25B9/60—Constructional parts of cells
    • C25B9/65—Means for supplying current; Electrode connections; Electric inter-cell connections
    • 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
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0206—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
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0213—Gas-impermeable carbon-containing materials
    • 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
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2465—Details of groupings of fuel cells
    • H01M8/247—Arrangements for tightening a stack, for accommodation of a stack in a tank or for assembling different tanks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0206—Metals or alloys
    • H01M8/0208—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
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0223—Composites
    • H01M8/0228—Composites in the form of layered or coated products
    • 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 present invention relates to an electro ⁇ chemical cell having a conductive, dimensionally stable, oxide growth resistant current distributor.
  • the current distributor of the present invention is useful in a process for converting anhydrous hydrogen halide to a halogen gas or in an aqueous electrochemical process.
  • the oxide growth resistant current distributor of the present invention is particularly useful in the very aggressive environment associated with the oxidation of HCl to Cl 2 , whether in an anhydrous or an aqueous process.
  • Hydrogen chloride (HCl) or hydrochloric acid is a reaction by-product of many manufacturing processes which use chlorine.
  • chlorine is used to manufacture polyvinyl chloride, isocyanates, and chlorinated hydrocarbons/fluorinated hydrocarbons, with hydrogen chloride as a by-product of these processes.
  • supply so exceeds demand hydrogen chloride or the acid produced often cannot be sold or used, even after careful purification. Shipment over long distances is not economically feasible.
  • Discharge of the acid or chloride ions into waste water streams is environmentally unsound. Recovery and feedback of the chlorine to the manufacturing process is the most desirable route for handling the HCl by-product.
  • a number of commercial processes have been developed to convert HCl into usable chlorine gas. See, e.g., F. R.
  • the current electrochemical commercial process is known as the Uhde process.
  • aqueous HCl solution of approximately 22% is fed at 65° to 80° C to both compartments of an electrochemical cell, where exposure to a direct current in the cell results in an electrochemical reaction and a decrease in HCl concentration to 17% with the production of chlorine gas and hydrogen gas.
  • a polymeric separator divides the two compartments.
  • the process requires recycling of dilute (17%) HCl solution produced during the electrolysis step and regenerating an HCl solution of 22% for feed to the electrochemical cell.
  • the overall reaction of the Uhde process is expressed by the equation:
  • the chlorine gas produced by the Uhde process is wet, usually containing about 1% to 2% water. This wet chlorine gas must then be further processed to produce a dry, usable gas. If the concentration of HCl in the water becomes too low, it is possible for oxygen to be generated from the water present in the Uhde process. This possible side reaction of the Uhde process due to the presence of water, is expressed by the equation:
  • the presence of water in the Uhde system limits the current densities at which the cells can perform to less than 500 amps./ft. 2 , because of this side reaction.
  • the side reaction results in reduced electrical efficiency and corrosion of the cell components.
  • Balko employs an electrolytic cell having a solid polymer electrolyte membrane.
  • Hydrogen chloride in the form of hydrogen ions and chloride ions in aqueous solution, is introduced into an electrolytic cell.
  • the solid polymer electrolyte membrane is bonded to the anode to permit transport from the anode surface into the membrane.
  • controlling and minimizing the oxygen evolution side reaction is an important consideration. Evolution of oxygen decreases cell efficiency and leads to rapid corrosion of components of the cell.
  • the design and configuration of the anode pore size and electrode thickness employed by Balko maximizes transport of the chloride ions. This, results in effective chlorine evolution while minimizing the evolution of oxygen, since oxygen evolution tends to increase under conditions of chloride ion depletion near the anode surface. In Balko, although oxygen evolution may be minimized, it is not eliminated.
  • Balko As can be seen from Figs. 3 to 5 of Balko, as the overall current density is increased, the rate of oxygen evolution increases, as evidenced by the increase in the concentration of oxygen found in the chlorine produced. Balko can run at higher current densities, but is limited by the deleterious effects of oxygen evolution. If the Balko cell were to be run at high current densities, the anode would be destroyed.
  • U.S. Patent No. 4,294,671 discloses another configuration for an electrochemical cell for processing aqueous HCl.
  • niobium current distributing screen elements are positioned between an anode deposited on a membrane and an anode current collector.
  • Metals such as niobium, tantalum, titanium, etc. and alloys thereof are known to have good corrosion resistance and conductivity. However, they are costly.
  • valve metals also have a tendency to passivate by the formation of protective surface oxide layers which are very poor conductors. Hence it is necessary to coat the valve metal with a non-oxide forming material such as a film of one of the platinum group metals, which further adds to the cost.
  • Patent No. 4,214,969 to Lawrence has been found that graphite can be oxidized, due to the side reaction of oxygen generated from water, as expressed in equation (3) above. Moreover, graphite and the best case of graphite-polyvinylidene fluoride have resistivities of 10"3 ohm-cm and 3 x 10 ⁇ 3 ohm*cm, respectively, which make them relatively poor conductors.
  • Oda et al. in U.S. Patent Nos. 4,909,912, 4,666,574 and 4,655,887, recognize the corrosion- resistant properties of a porous layer made of the oxides, hydroxides, nitrides or carbides of certain metals in electrolyzing an aqueous solution of an alkali metal chloride.
  • the porous layer is disposed between a membrane and an anode, which in turn is disposed in contact with the alkali metal chloride.
  • the porous layer does not act as a corrosion barrier to the alkali metal chloride.
  • the present invention solves the problems of the prior art by providing an electrochemical cell for directly producing essentially dry halogen gas from essentially anhydrous hydrogen halide where the cell has a conductive current distributor which acts as a corrosion-resistant barrier to the essentially dry halogen gas and the essentially anhydrous hydrogen halide.
  • This process allows for direct processing of anhydrous hydrogen halide which is a by-product of manufacturing processes, without first dissolving the hydrogen halide in water.
  • This direct production of essentially dry halogen gas when done, for example, for chlorine gas, is less capital intensive than processes of the prior art, which require separation of water from the chlorine gas.
  • the current distributor of an electrochemical cell from a metal which is nitrided, borided or carbided, or from the nitrided, borided or carbided alloys of such metals results in a current distributor which is dimensionally stable and which resists oxide growth formation. Accordingly, the current distributor of the present invention has a longer life and is thus less costly than known metal current distributors. These advantages make the process of the present invention even more practicable and economically attractive.
  • an electrochemical cell comprising an electrode; a membrane disposed in contact with one side of the electrode; and current distributing means disposed on the other side of the electrode for distributing current to the electrode by electronic conduction and for allowing current to flow away from the electrode, wherein the current distributing means comprises a metal selected from the group consisting of a nitrided metal, a carbided metal, a borided metal, the nitrided alloys of a metal, the borided alloys of a metal and the carbided alloys of a metal.
  • an electrochemical cell for the direct production of essentially dry halogen gas from essentially anhydrous hydrogen halide.
  • the electrochemical cell comprises means for oxidizing molecules of essentially anhydrous hydrogen halide to produce essentially dry halogen gas and protons, cation-transporting means for transporting the protons therethrough, wherein one side of the oxidizing means is disposed in contact with one side of the cation- transporting means; reducing means for reducing the transported protons, wherein the reducing means is disposed in contact with the other side of.
  • the current distributing means may alternatively be described as means disposed on one side of the oxidizing means for distributing current to the oxidizing means by electronic conduction and for allowing current to flow away from the oxidizing means.
  • the current distributing means comprises a metal selected from the group consisting of a nitrided metal, a carbided metal, a borided metal, the nitrided alloys of a metal, the borided alloys of a metal and the carbided alloys of a metal.
  • FIG. 1 is an exploded cross-sectional view of an electrochemical cell for producing halogen gas from anhydrous hydrogen halide according to a first and a second embodiment of the present invention.
  • Fig. 1A is a cut-away, top cross-sectional view of the anode and cathode mass flow fields as shown in Fig. 1.
  • Fig. 2 is a perspective view of an electrochemical cell for producing, for example, halogen gas from aqueous hydrogen halide according to a third embodiment of the present invention.
  • an electrochemical cell for the direct production of essentially dry halogen gas from anhydrous hydrogen halide Such a cell is shown generally at 10 in Fig. 1.
  • the cell of the present invention will be described with respect to a preferred embodiment of the present invention, which directly produces essentially dry chlorine gas from anhydrous hydrogen chloride.
  • This cell may alternatively be used to produce other halogen gases, such as bromine, fluorine and iodine from a respective anhydrous hydrogen halide, such as hydrogen bromide, hydrogen fluoride and hydrogen iodide.
  • hydrogen fluoride may be particularly corrosive when used with the present invention.
  • the term "direct" means that the electrochemical cell obviates the need to remove water from the halogen gas produced or the need to convert essentially anhydrous hydrogen halide to aqueous hydrogen halide before electrochemical treatment.
  • chlorine gas, as well as hydrogen is produced in this cell.
  • water, as well as chlorine gas is produced by this cell, as will be explained more fully below.
  • the electrochemical cell of the first and second embodiments comprises an electrode.
  • the electrochemical cell of the first and second embodiments may be described as comprising means for oxidizing molecules of essentially anhydrous hydrogen halide to produce essentially dry halogen gas and protons.
  • the oxidizing means is an electrode, or more specifically, an anode 12 as shown in Fig. 1.
  • electrochemical cell 10 On the " anode side, electrochemical cell 10 has an anode-side inlet 14 and an anode-side outlet 16.
  • TEFLON ® PFA perfluoropolymer sold as TEFLON ® PFA (hereinafter referred to as "TEFLON ® PFA") by E. I. du Pont de Nemours and Company of Wilmington, Delaware (hereinafter referred to as "DuPont”) .
  • the electrochemical cell of the first and second embodiments also comprises a membrane.
  • the electrochemical cell of the first and second embodiments may be described as comprising cation- transporting means for transporting the protons therethrough, where one side of the oxidizing means is disposed in contact with one side of the cation- transporting means.
  • the cation- transporting means is a cation-transporting membrane 18 as shown in Fig. 1. More specifically, membrane 18 may be a proton-conducting membrane.
  • Membrane 18 may be a commercial cationic membrane made of a fluoro- or perfluoropolymer, preferably a copolymer of two or more fluoro or perfluoromonomers, at least one of which has pendant sulfonic acid groups.
  • carboxylic groups is not desirable, because those groups tend to decrease the conductivity of the membrane when they are protonated.
  • suitable resin materials are available commercially or can be made according to patent literature. They include fluorinated polymers with side chains of the type -CF 2 CFRS0 3 H and -OCF 2 CF 2 CF 2 S0 3 H, where R is a F, Cl, CF 2 C1, or a C x to C 10 perfluoroalkyl radical.
  • the sulfonyl fluoride groups can be hydrolyzed with potassium hydroxide to -S0 3 K groups, which then are exchanged with an acid to -S0 3 H groups.
  • Suitable cationic membranes which are made of hydrated, copolymers of polytetrafluoroethylene and poly-sulfonyl fluoride vinyl ether-containing pendant sulfonic acid groups, are offered by DuPont under the trademark "NAFION” (hereinafter referred to as NAFION ® ) .
  • NAFION ® membranes containing pendant sulfonic acid groups include NAFION ® 117, NAFION ® 324 and NAFION ® 417.
  • the first type of NAFION ® is unsupported and has an equivalent weight of 1100 g., equivalent weight being defined as the amount of resin required to neutralize one liter of a 1M sodium hydroxide solution.
  • NAFION ® 324 has a two-layer structure, a 125 ⁇ m-thick membrane having an equivalent weight of 1100 g., and a
  • NAFION ® 117F grade is a precursor membrane having pendant -S0 2 F groups that can be converted to sulfonic acid groups.
  • NAFION ® 117F grade is a precursor membrane having pendant -S0 2 F groups that can be converted to sulfonic acid groups.
  • the present invention describes the use of a solid polymer electrolyte membrane, it is well within the scope of ,the invention to use other cation- transporting membranes which are not polymeric.
  • proton-conducting ceramics such as beta- alumina may be used.
  • Beta-alumina is a class of nonstoichiometric crystalline compounds having the general structure Na 2 O x ⁇ l 0 3 , in which x ranges from 5 ( ⁇ "-alumina) to 11 ( ⁇ -alumina) .
  • the electrochemical cell of the first and second embodiments also comprises an electrode, or a cathode 20.
  • the electrochemical cell of the first and second embodiments may be described as comprising means for reducing the transported protons, where the reducing means is disposed in contact with the other side of the cation-transporting means.
  • the reducing means comprises a cathode 20, where cathode 20 is disposed in contact with the other side (as opposed to the side which is in contact with the anode) of membrane 18 as illustrated in Fig. 1.
  • Cathode 20 has a cathode-side inlet 24 and a cathode-side outlet 26 as shown in Fig. 1. Since in the preferred embodiment, anhydrous HCl is processed, and since some chlorides pass through the membrane and consequently, HCl is present on the cathode-side of the cell, the cathode inlet and the outlet may be lined with TEFLON ® PFA.
  • Fig. 1 The protons, H + , are transported through the membrane and reduced at the cathode. This is explained in more detail below.
  • the anode and the.cathode may comprise porous, gas-diffusion electrodes. Such electrodes provide the advantage of high ' specific surface area, as known to one skilled in the art.
  • the anode and the cathode comprise an electrochemically active material disposed adjacent, meaning at or under, the surface of the cation-transporting membrane. A thin film of the electrochemically active material may be applied directly to the membrane. Alternatively, the electrochemically active material may be hot-pressed to the membrane, as shown in A. J. Appleby and E. B. Yeager, Energy, Vol. 11, 137 (1986). Alternatively, the electrochemically active material may be deposited into the membrane, as shown in U.S. Patent No. 4,959,132 to Fedkiw.
  • the electrochemically active material may comprise any type of catalytic or metallic material or metallic oxide, as long as the material can support charge transfer.
  • the electro ⁇ chemically active material may comprise a catalyst material such as platinum, ruthenium, osmium, rhenium, rhodium, iridium, palladium, gold, titanium or zirconium and the oxides, alloys or mixtures thereof.
  • the oxides of these materials are not used for the cathode.
  • Other catalyst materials suitable for use with the present invention may include, but are not limited to, transition metal macro cycles in monomeric and polymeric forms and transition metal oxides, including perovskites and pyrochores.
  • the electrochemically active material may comprise a catalyst material on a support material.
  • the support material may comprise particles of carbon and particles of polytetrafluoro ⁇ ethylene, which is sold under the trademark "TEFLON” (hereinafter referred to as TEFLON ® ) by DuPont.
  • the electrochemically active material may be bonded by virtue of the TEFLON ® to a support structure of carbon paper or graphite cloth and hot-pressed to the cation- transporting membrane.
  • the hydrophobic nature of TEFLON ® does not allow a film of water to form at the anode. A water barrier in the electrode would hamper the diffusion of HCl to the reaction sites.
  • the electrodes are preferably hot-pressed into the membrane in order to have good contact between the catalyst and the membrane.
  • the loadings of electrochemically. active material may vary based on the method of application to the membrane.
  • Hot-pressed, gas-diffusion electrodes typically have loadings of 0.10 to 0.50 mg/cm 2 . Lower loadings are possible with other available methods of deposition, such as distributing ' them as thin films from inks onto the membranes, as described in Wilson and Gottesfeld, "High Performance Catalyzed Membranes of Ultra-low Pt Loadings for Polymer Electrolyte Fuel Cells", Los Alamos National Laboratory, J. Electrochem. Soc, Vol. 139, No.
  • the electrochemical cell of the first and second embodiments further comprises an anode flow field 28 disposed in contact with the anode and a cathode flow field 30 disposed in contact with the cathode.
  • the flow fields are electrically conductive, and act as both mass and current flow fields. More specifically, the mass flow fields may include a plurality of anode flow channels 29 and a plurality of cathode flow channels 31 as shown in Fig. 1A, which is a cut-away, top cross-sectional view showing only the flow fields of Fig. 1.
  • the purpose of the anode flow field and flow channels 29 formed therein is to get reactants, such as anhydrous HCl in the first and second embodiments, to the anode and products, such as essentially dry chlorine gas from the anode.
  • the purpose of the cathode flow field and flow channels 31 formed therein is to get catholyte, such as liquid water in the first embodiment, or oxygen gas in the second embodiment, to the cathode and products, such as hydrogen gas in the first embodiment, or water vapor (H 0(g)) in the second embodiment, from the cathode. Water vapor may be needed to keep the membrane hydrated. However, water vapor may not be necessary in this embodiment because of the water produced by the electrochemical reaction of the oxygen (0 2 ) added as discussed below.
  • the flow .fields and the flow channels may have a variety of configurations.
  • the flow fields may be made in any manner known to one skilled in the art.
  • the anode and the cathode flow fields comprise porous graphite paper.
  • the flow fields may also be made of a porous carbon in the form of a foam, cloth or matte.
  • the electrochemical cell of the first and second embodiments may also comprise an anode mass flow manifold 32 and a cathode mass flow field manifold 34 as shown in Fig. 1.
  • the purpose of such manifolds is to bring anolyte to and products from the anode, and catholyte to and products from the cathode.
  • the manifolds form a frame around the anode mass flow field and the anode, and the cathode mass flow field and the cathode, respectively.
  • These manifolds are preferably made of a corrosion resistant material, such as TEFLON ® PFA.
  • a gasket 36, 38 also contributes to forming a frame around the respective anode and cathode mass flow fields.
  • These gaskets are preferably also made of a corrosion resistant material, such as polytetrafluoroethylene, sold under the trademark TEFLON ® PTFE by DuPont.
  • the electrochemical cell of the first and second embodiments also* comprises an anode current bus 46 and a cathode current bus 48 as shown in Fig. 1.
  • the current buses conduct current to and from a voltage source (not shown) .
  • anode current bus 46 is connected to the positive terminal of a voltage source
  • cathode current bus 48 is connected to the negative terminal of the voltage source, so that when voltage is supplied to the cell, current flows through all of the cell components to the right of current bus 46 as shown in Fig. 1, including current bus 48, from which it returns to the voltage source.
  • the current buses are made of a conductor material, such as copper.
  • the electrochemical cell of the first and second embodiments further comprises anode current distributing means disposed on one side of the electrode, or the oxidizing means, for distributing current to the electrode, or the oxidizing means, by electronic conduction, or the oxidizing means and for allowing the current to flow away from the electrode, or oxidizing means.
  • the current distributing means may be described as means disposed on one side of the electrode, or the oxidizing means, for providing a barrier between the current bus and the electrode, or the oxidizing means, and the hydrogen halide, such as hydrogen chloride and the halogen gas, such as chlorine gas.
  • the anode current distributing means comprises an anode current distributor 40 as shown in Fig. 1.
  • the current distributor comprises a non-porous layer.
  • the anode flow field which is disposed next to the anode current distributor as shown in Fig. 1, brings anolyte, such as anhydrous hydrogen halide in the first and second embodiments, to the anode, and takes products, such as essentially dry chlorine gas in the first and second embodiments, away from the anode.
  • Certain hydrogen halides, such as HCl are particularly corrosive. Therefore, in accordance with the present invention, the current distributor is treated in order to protect the current bus, which must consistently conduct current and therefore must be able to withstand attack, from such corrosive environments.
  • the anode current distributor comprises a metal which has been either nitrided, borided or carbided, or the nitrided, carbided or borided alloys of a metal, meaning the nitrided alloys of a metal, the borided alloys of a metal or the carbided alloys of a metal.
  • the alloy is made first and then the alloy is nitrided, borided or carbided. It should be noted that nitrides, carbides and borides can be co-formed.
  • the metal of the anode current distributor may be a Group IVB or Group VB metal - i.e., titanium, zirconium, hafnium, vanadium, niobium, tantalum, or the nitrided, carbided or borided alloys thereof, meaning the nitrided, carbided or borided alloys of titanium, zirconium, hafnium, vanadium, niobium or tantalum.
  • the metal may be tungsten, or the nitrided, borided or carbided alloys thereof.
  • the metal be tantalum that has been nitrided to form Ta 2 N, although other nitride stoichiometries may be acceptable in less aggressive conditions.
  • Nitriding at one atmosphere of nitrogen at 871° C for one hour gives the preferential Ta 2 N, although the length of time for nitriding depends on the heat-up and cool down rate of the nitrided metal.
  • Nitrided tantalum which has a resistivity of 2 x 10 ⁇ 4 ohm•cm, provides a material for the current distributor of the present invention which has a lower resistivity than known current collectors.
  • graphite and graphite-polyvinylidene fluoride have resistivities of 10 ⁇ 3 ohm-cm and 3 x 10 ⁇ 3 ohm-cm, respectively. This provides better conduction in the cell of the present invention as compared to cells of the prior art.
  • the nitrogen penetrates the surface of the metal and forms a metal- nitrogen compound.
  • metal nitride for instance, nitrided
  • the nitrogen penetrates the surface of the metal and forms a metal- nitrogen compound.
  • the metal is treated in accordance with the present invention, for instance, nitrided
  • the nitrogen penetrates the surface of the metal and forms a metal- nitrogen compound.
  • the nitriding may be done by known techniques. Standard nitriding techniques which are suitable for use with the present invention include chemical vapor deposition (CVD) , gas phase reaction or ion plasma reaction.
  • CVD chemical vapor deposition
  • the same techniques may be used for carbiding and boriding, it is preferable to use the gas phase reaction technique for carbiding, and the CVD technique for boriding.
  • the electrochemical cell of the present invention may further comprise cathode current distributing means disposed on one side of the reducing means, or electrode, or more specifically the cathode, for collecting current from the cathode and for distributing current to the cathode bus by electronic conduction.
  • the cathode current distributing means may be described as means disposed on one side of the reducing means, or cathode, for providing a barrier between the cathode current bus and the cathode and the hydrogen halide. This is desirable because there is some migration of hydrogen halide through the membrane.
  • the cathode current distributing means comprises a cathode current distributor 42 as shown in Fig. 1.
  • the cathode current distributor may comprise a metal.
  • the metal for the cathode current distributor need not necessarily be a nitrided, borided or carbided metal or a nitrided, borided or carbided alloy thereof.
  • the metal may be a nickel-based alloy, such as UNS10665, sold under the trademark Hastelloy ® B-2 by Haynes International. This is because in the first embodiment, in the long run when nitrided, borided or carbided Group IV or VB metals are used, there is hydrogen embrittlement, and an alternative is needed.
  • nitrided, borided and carbided metals, including Group IV or VB metals and tungsten can be used, as hydrogen embrittlement is not a problem.
  • the current distributors of the present invention may be corrugated and nitrided, borided or carbided.
  • grooves may be machined in the current bus, and the current distributor may be matched to the grooves in the current bus. This configuration obviates the need for the flow fields, thus providing lower contact resistance.
  • the electrochemical cell also comprises a conductive structural support 44 disposed in contact with anode current distributor 40.
  • the support on the anode side is preferably made of UNS31603 (316L stainless steel) .
  • a seal 45 preferably in the form of an O-ring made from a perfluoroelastomer, sold under the trademark KALREZ ® by DuPont, is disposed between structural support 44 on the anode side and anode current distributor 40.
  • structural support 44 is shown in front of anode current bus 46 in Fig. 1, it is within the scope of the present invention for the structural support to be placed behind the anode current bus (i.e., to the left of bus 46 as shown in Fig. 1) and still achieve the same results.
  • the cathode current distributor acts as a corrosion-resistant structural backer on the cathode side. This piece can be drilled and tapped to accept the TEFLON ® PFA fitting, which is used for the inlet and outlet.
  • a bipolar arrangement as familiar to one skilled in the art, is preferred.
  • the electrochemical cell of the present invention may be used in a bipolar stack.
  • current distributors 40 and 42 and all the elements disposed in between as shown in Fig. 1 are repeated along the length of the cell, and current buses are placed on the outside of the stack.
  • the anhydrous hydrogen halide may comprise hydrogen chloride, hydrogen bromide, hydrogen fluoride or hydrogen iodide.
  • hydrogen fluoride may be particularly corrosive when used with the present invention.
  • the production of bromine gas and iodine gas can be accomplished when the electrochemical cell is run at elevated temperatures (i.e., about 60° C and above for bromine and about 190° C and above for iodine) .
  • a membrane made of a material other than NAFION ® should be used.
  • anhydrous hydrogen halide is hydrogen chloride.
  • current flows to the anode bus and anode current distributor 40 collects current from the anode bus and distributes it to the anode by electronic conduction.
  • Molecules of essentially anhydrous hydrogen chloride gas are fed to anode-side inlet 14 and through flow channels 29 in the anode mass flow field 28 and are transported to the surface of anode 12.
  • the molecules are oxidized at the anode under the potential created by the voltage source to produce essentially dry chlorine gas (Cl 2 (g) ) at the anode, and protons (H + ) .
  • This reaction is given by the equation:
  • the protons (H + ) are transported through the membrane, which acts as an electrolyte.
  • the transported protons are reduced at the cathode.
  • Water is delivered to the cathode through cathode-side inlet 24 and through the grooves in cathode flow field 30 to hydrate the membrane and thereby increase the efficiency of proton transport through the membrane.
  • the hydrogen which is evolved at the interface between the electrode and the membrane exits via cathode-side outlet 26 as shown in Fig. 1, The hydrogen bubbles through the water and is not affected by the TEFLON ® in the electrode.
  • Cathode current distributor 42 collects current from cathode 20 and distributes it to cathode bus 48.
  • anode current distributor 40 collects current from the anode bus and distributes it to the anode by electronic conduction.
  • Molecules of essentially anhydrous hydrogen chloride are fed to anode-side inlet 14 and are transported through grooves of anode mass flow field 28 to the surface of anode 12.
  • An oxygen- containing gas such as oxygen (0 2 (g) ) , air or oxygen- enriched air (i.e., greater than 21 mol% oxygen in nitrogen) is introduced through cathode-side inlet 24 and through the grooves formed in cathode mass flow field 30.
  • This cathode feed gas may be humidified to aid in the control of moisture in the membrane.
  • Molecules of the hydrogen chloride (HCl(g)) are oxidized under the potential created by the voltage source to produce essentially dry chlorine gas at the anode, and protons (H + ) , as expressed in equation (4) above.
  • the chlorine gas (Cl 2 ) exits through anode-side outlet 16 as shown in Fig. 1.
  • the protons (H + ) are transported through the membrane, which acts as an electrolyte. Oxygen and the transported protons are reduced at the cathode to water, which is expressed by the equation: .0 2 (g) + 2e ⁇ + 2H+ H 2 0(g) (6)
  • the water formed exits via cathode-side outlet 26 as shown in Fig. 1, along with any nitrogen and unreacted oxygen.
  • the water also helps to maintain hydration of the membrane, as will be further explained below.
  • Cathode current distributor 42 collects current from cathode 20 and distributes it to cathode bus 46.
  • the cathode reaction is the formation of water. This cathode reaction has the advantage of more favorable thermodynamics relative to H2 production at the cathode as in the first embodiment. This is because the overall reaction in this embodiment, which is expressed by the following equation:
  • the amount of voltage or energy required as input to the cell is reduced in this second embodiment.
  • the membrane of both the first and the second embodiments in the anhydrous case must be hydrated in order to have efficient proton transport.
  • the cathode-side of the membrane must be kept hydrated in order to increase the efficiency of proton transport through the membrane.
  • the hydration of the membrane is obtained by keeping liquid water in contact with the cathode. The liquid water passes through the gas-diffusion electrode and contacts the membrane.
  • the membrane hydration is accomplished by the production of water as expressed by equation (6) above and by the water introduced in a humidified oxygen-feed or air-feed stream. This keeps the conductivity of the membrane high.
  • the electrochemical cell can be operated over a wide range of temperatures.
  • Room temperature operation is an advantage, due to the ease of use of the cell.
  • operation at elevated temperatures provides the advantages of improved kinetics and increased electrolyte conductivity. Higher temperatures result in lower cell voltages.
  • limits on temperature occur because of the properties of the materials used for elements of the cell.
  • the properties of a NAFION ® membrane change when the cell is operated above 120° C.
  • the properties of a polymer electrolyte membrane make it difficult to operate a cell at temperatures above 150° C.
  • With a membrane made of other materials, such as a ceramic material like beta- alumina it is possible to operate a cell at temperatures above 200° C.
  • one is not restricted to operate the electrochemical cell of either the fi-rst or the second embodiment at atmospheric pressure.
  • the cell could be run at differential pressure gradients, which change the transport characteristics of water or other components in the cell, including the membrane.
  • Fig. 2 illustrates a third embodiment of the present invention.
  • elements corresponding to the elements of the embodiment of Fig. 1 will be shown with the same reference numeral as in Fig. 1, but will be designated with a prime (')•
  • An electrochemical cell of the third embodiment is shown generally at 10" in Fig. 2.
  • the electrochemical cell of the third embodiment will be described with respect to a preferred embodiment, where halogens, such as chlorine, are generated by the electrolysis of an aqueous solution of a hydrogen halide, such as hydrochloric acid.
  • halogens such as chlorine
  • hydrochloric acid such as sodium halide
  • the electrochemical cell of the third embodiment comprises an electrode, or more specifically, an anode 12' or a cathode 20'.
  • the electrochemical cell of the third embodiment also comprises a membrane disposed in contact with one side of the electrode.
  • a membrane 18' is shown in Fig. 2 having one side disposed in contact with one side of anode 12' .
  • the membrane need not necessarily be a cation-transporting membrane.
  • Cathode 20' is disposed in contact with the other side (as opposed to the side which is in contact with the anode) of membrane as illustrated in Fig. 2.
  • the electrochemical cell of the third embodiment further comprises a mass flow field disposed in contact with the electrode.
  • the mass flow field may be an anode mass flow field 28' disposed in contact with the anode, or a cathode mass flow field 30' disposed in contact with the cathode.
  • the mass flow fields act as both mass and current flow fields.
  • the purpose of the anode flow field is to get anolyte, such as aqueous HCl in the third embodiment to the anode and products, such as wet chlorine gas, from the anode.
  • the purpose of the cathode flow field is to get catholyte to and product, such as hydrogen gas, from the cathode.
  • the electrochemical cell of the third embodiment also comprises a current bus for conducting current to the electrode, where the current bus is disposed on the other side of the electrode.
  • An anode current bus 46' and a cathode current bus 48' are shown in Fig. 2.
  • the current buses conduct current from a voltage source (not shown) .
  • anode current bus 46' is connected to the positive terminal of a voltage source
  • cathode current bus 48' is connected to the negative terminal of the voltage source, so that when voltage is supplied to the cell, current flows from the voltage source through all of the elements to the right of current bus 46' as shown in Fig. 2, including current bus 48' from which it returns to the voltage source.
  • the current buses of the third embodiment are made of a conductor material, such as copper.
  • the electrochemical cell of the third embodiment further comprises a current distributor disposed on the other side of the electrode (as opposed to the side which is in contact with the membrane) .
  • An anode current distributor 40' is disposed on one side of anode 12*
  • a cathode current distributor 42' is disposed on one side of cathode 20'.
  • the anode current distributor distributes current to the anode by electronic conduction and allows current to flow away from the anode.
  • the cathode current distributor distributes current to the cathode by electronic conduction and allows current to flow to the cathode.
  • the anode and the cathode current distributors preferably each comprise a non-porous layer.
  • the anode current distributor provides a barrier between the anode current bus and the reactant, such as aqueous hydrogen chloride and the product, such as wet gaseous chlorine.
  • the cathode current distributor provides a barrier between the cathode current bus and the catholyte.
  • the current distributors of the third embodiment are made of the same materials as described above for the first embodiment.
  • the anode and the cathode current distributor may comprise a metal which has been either nitrided, borided or carbided, or the nitrided, carbided or borided alloys of a metal, meaning the nitrided alloys of a metal, the borided alloys of a metal, or the carbided alloys of a metal. In the latter case, the alloy is made first and then the alloy is nitrided, borided or carbided.
  • the cathode current distributor may comprise a metal which is not necessarily nitrided, borided or carbided, such as a nickel-based alloy.
  • Example 1 shows the use of a nitrided current distributor in an aqueous environment, such as that described in the third embodiment above.
  • Examples 4-7, 9 and 10 show that the anodic activity (i.e., the oxidation of reactants) on a current distributor does riot degrade cell performance. During start-up of either an anhydrous or an aqueous electro- chemical cell, the current distributor will act like an anode. These Examples also show that a metal treated in accordance with the present invention (i.e., nitrided, borided or carbided) does not oxidize when exposed to HCl solution and oxidizing potentials. Moreover, these Examples show that it is within the scope of the present invention that the anode may comprise a nitrided, borided or carbided metal, or the nitrided, borided or carbided alloys thereof.
  • a metal treated in accordance with the present invention i.e., nitrided, borided or carbided
  • the anode may comprise a nitrided, borided or carbided metal
  • Electrodes as described in U.S. Patent No. 4,210,501 may also be used with the present invention. It is also within the scope of the present invention to use other known metallization techniques in making electrodes for use with the present invention.
  • the technique used in U.S. Patent No. 4,959,132 to Fedkiw, frequently referred to as Impregnation-Reduction is an appropriate method to use with the present invention.
  • the metallization technique may be used, as described in Japanese Publication No. 38934, published in 1980 and J. Hydrogen Energy, 5, 397 (1982) .
  • EXAMPLE 1 In this Example, essentially anhydrous HCl was fed to a 50 cm 2 cell at 1 standard liter per minute (SLPM) .
  • the cell design was that shown in Fig. 1, where a nitrided tantalum current distributor was used on the anode side (for current distributor 40 as shown in Fig. 1) .
  • a current density of 8000 A/m 2 was obtained when a potential of4.4 V was applied across the copper buses..
  • the anode outlet was briefly directed to a potassium iodide bath to confirm the generation of chlorine from the HCl.
  • the cell was operated for a total of 7.5 hours at current densities ranging from 1000 A/m 2 to 10,000 A/m 2 .
  • the cell was disassembled, and the nitrided tantalum current distributor showed no signs of oxidation in the active cell area.
  • nitrided tantalum Ti
  • the anode was Pt and the cathode was UNS N10665 nickel-based alloy.
  • the cell was operated at a constant potential of 2V.
  • the Pt anode was directly connected to the anode bus, the average current density over a 24 hour period was 390 mA/cm 2 .
  • the nitrided tantalum current distributor was inserted between the anode bus and the Pt anode, the average current density over a 24 hour period was 390 mA/cm 2 .
  • the thin gage and the nitriding combined to create a low resistivity current distributor.
  • the Ohmic (IR) loss from the nitrided Ta current distributor was approximately 1 ⁇ V.
  • EXAMPLE 3 In this control example, an electrochemical cell and 37% HCl at 60°C was used to study current distributor materials.
  • the anode was tantalum (Ta) and the cathode was platinum (Pt) .
  • a potential of 2V was applied between the anode and cathode for 62 hours and the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through potassium iodide (KI) . The KI was then titrated to determine the amount of Cl 2 generated.
  • KI potassium iodide
  • the average current density was 2 ⁇ A/cm 2 for 62 hours at 2V. There was a rapid decay in the current at the start of the test followed by a very slow decay. There was very little Cl 2 generated during the 62 hour test. A visual examination of the Ta anode showed an oxide film formed during the test.
  • the oxide thickness was 10 nm.
  • the Ta 2 0 5 oxide penetrated to a depth of 120 nm.
  • the oxygen level decayed from stoichiometri ⁇ Ta 2 0 5 at 120 nm to nearly zero at a depth of 200 nm.
  • EXAMPLE 4 In this Example, an electrochemical cell and 37% HCl at 60°C was used to study current distributor materials.
  • the anode was TaN CVD deposited on Ta, and the cathode was Pt.
  • a potential of 2V was applied for 4 hours and 3V was applied for 60 hours.
  • the potential was measured between the anode and cathode, and the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through KI.
  • the average current density was 14.5 ⁇ A/cm 2 at 2V and 16 ⁇ A/cm 2 at 3V.
  • a microscopic examination of the anode showed a pale brown tint to the surface.
  • the KI turned yellow, indicating a small amount of Cl 2 was 5 generated.
  • TaN While not a very active catalyst surface, TaN has a resistivity of 200 ⁇ Ohm-cm, making it a suitable current distributor.
  • EXAMPLE 5 In this Example, an electrochemical cell and 37% 0 HCl at 60°C was used to study current distributor materials.
  • the anode was 60% tantalum, 40% niobium (nitrided Ta40Nb) . It had a 10 nm surface layer of TaN/NbN, (tantalum nitride/niobium nitride) a 300 nm transition zone from the 1:1 to the 2:1 metal to 5 nitrogen ratio and a Ta 2 N/Nb 2 N (tantalum nitride/niobium nitride) layer approximately 1500 nm thick.
  • the cathode was Pt.
  • a potential of 2V was applied for 4 hours, 3V was applied for 60 hours, and the current was measured versus time.
  • the cell was 0 swept with nitrogen and the off gas purged through KI.
  • the average current density as 0.13 ⁇ A/cm 2 at 2V and 0.1 ⁇ A/cm 2 at 3V.
  • a microscopic examination of the anode showed no visible changes to the surface.
  • a surface analysis showed a minor 10 atomic % oxygen 5 spike to a depth of 15 nm (Ta 2 0 5 is 71 atomic % oxygen) .
  • the KI showed some color change indicating Cl 2 was produced.
  • the addition of Nb is done to reduce the cost of the current distributor versus pure Ta.
  • EXAMPLE 6 In this Example, an electrochemical cell and 37% HCl at 60°C was used to study current distributor materials.
  • the anode was gas phase nitrided Ta. It had a 10 nm thick surface layer of TaN, a 30 nm transition zone from TaN to Ta 2 N and a Ta 2 N layer 5 approximately 300 nm thick.
  • a cathode was Pt.
  • a potential of 2V was applied for 4 hours, 3V was applied for 60 hours and the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through KI.
  • the average current density was 0.008 ⁇ A/cm 2 for the 4 hours at 2V and 0.06 ⁇ A/cm 2 for the 60 hours at 3V.
  • EXAMPLE 7 In this Example, an electrochemical cell and 37% HCl at 60°C was used to study current distributor materials.
  • the anode was gas phase nitrided Ta. It had a TaN layer approximately 125 nm thick, a 450 nm transition zone from TaN to Ta N and a 1000 nm thick Ta 2 N zone.
  • the cathode was Pt. A potential of 2V was applied for 4 hours and 3V was applied for 60 hours and the current was measured versus time. The cell was swept with nitrogen and the off gas purged through KI. The average current density was 2.16 mA/cm 2 for the 4 hours at 2V and 22 ⁇ A/cm 2 for 60 hours at 3V.
  • an electrochemical cell and 37% HCl at 22°C was used to study current distributor materials.
  • the anode was graphite and the cathode was Pt.
  • the applied potential was either 2V or 3V and was applied between the anode and cathode.
  • the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through KI to detect Cl formation.
  • Graphite is not an ideal current distributor due to its being attacked during cell operation. Despite this shortcoming, it has been used in aqueous HCl to Cl 2 electrolysis.
  • the resistivity of graphite is 1.4 x 10 -3 Ohm-cm at 0°C.
  • EXAMPLE 9 In this Example, an electrochemical cell and 37% HCl at 22°C was used to study current distributor materials.
  • the anode was titanium carbide and the cathode was Pt.
  • a potential of 2V was applied to the cell and the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through KI to detect 'Cl 2 formation.
  • the average current density was 0.8 mA/cm 2 for the 30 minute test.
  • the KI remained clear indicating no Cl 2 was detected. There was no visible attack of the surface, though it had the appearance of being somewhat smoother after the testing. While not a catalytically active surface, its low resistivity of only 60 ⁇ Ohm-cm makes it suitable as current distributor.
  • EXAMPLE 10 In this Example, an electrochemical cell and 37% HCl at 60°C was used to study current distributor materials.
  • the anode was TaB 2 CVD deposited on Ta and the cathode was Pt.
  • a potential of 2V was applied to the cell for 4 hours and 3V was applied for 60 hours.
  • the current was measured versus time.
  • the cell was swept with nitrogen and the off gas purged through KI to detect Cl 2 formation.
  • the average current density was 0.7 ⁇ A/cm 2 for the 4 hour test and 0.06 ⁇ A/cm 2 for the 60 hour test.
  • the KI turned golden brown indicating Cl 2 was generated. There was no visible attack of the surface, though it did appear to form a very slight tint. Surface analysis showed that the oxide film growth was limited to 15 nm.

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Abstract

L'invention porte sur une cellule électrochimique constituée d'une électrode, soit une anode soit une cathode, et d'une membrane placée contre un côté de l'électrode. Un courant de plaque est placé de l'autre côté de l'anode et un courant cathodique est placé de l'autre côté de la cathode. Un répartiteur de courant de plaque capte du courant à partir d'un bus de courant de plaque et le répartit à l'anode par conduction électronique, tandis qu'un répartiteur de courant cathodique capte du courant à partir de la cathode et le répartit au bus cathodique par conduction électronique. Le répartiteur de courant de plaque ou de courant cathodique est fait d'un métal traité par un de ces procédés: nitruration, boruration ou carburation, afin de le rendre résistant au développement oxydique. Dans un mode de réalisation alternatif, le répartiteur de courant côté cathode peut être fait d'un alliage à base de nickel. Le répartiteur de courant fait ainsi office de barrière entre le bus de courant et l'électrode, et l'anolyte, la catholyte et les produits de la cellule. Cela est d'autant plus important dans les milieux agressifs, tel que celui du chlorure d'hydrogène. Par conséquent, le répartiteur de courant de l'invention s'avère être d'utilité dans une cellule pour convertir directement de l'halogénure d'hydrogène anhydre en gaz halogène quasiment sec, telle que la transformation du chlorure d'hydrogène anhydre en gaz chloré, ou bien pour convertir du chlorure d'hydrogène aqueux en gaz chloré humide.
PCT/US1995/016033 1995-05-01 1995-12-13 Cellule electrochimique a repartiteur de courant resistant au developpement oxydique WO1996035004A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1060019A4 (fr) * 1998-02-23 2002-03-13 T J Technologies Inc Catalyseur
EP2258474A4 (fr) * 2008-02-20 2011-09-14 Showa Denko Kk Support de catalyseur, catalyseur et son procédé de fabrication

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5292600A (en) * 1992-08-13 1994-03-08 H-Power Corp. Hydrogen power cell

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5292600A (en) * 1992-08-13 1994-03-08 H-Power Corp. Hydrogen power cell

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 101, no. 16, 15 October 1984, Columbus, Ohio, US; abstract no. 134012, JALAN VINOD M.: "SUBSTITUTES FOR CARBON IN FURL CELL APPLICATIONS" page 194; XP002001384 *
PRO. ELECTROCHEMICAL. SOC., vol. 84, no. 5, 1984, pages 554 - 573 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1060019A4 (fr) * 1998-02-23 2002-03-13 T J Technologies Inc Catalyseur
EP2258474A4 (fr) * 2008-02-20 2011-09-14 Showa Denko Kk Support de catalyseur, catalyseur et son procédé de fabrication
US8541334B2 (en) 2008-02-20 2013-09-24 Showa Denko K.K. Catalyst carrier, catalyst and process for producing the same
US8785342B2 (en) 2008-02-20 2014-07-22 Showa Denko K.K. Catalyst carrier, catalyst and process for producing the same

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