Classifications

• • 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
  • C25B15/02—Process control or regulation
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
  • C25B1/04—Hydrogen or oxygen by electrolysis of water
• • 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
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
• • 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
  • C25B9/70—Assemblies comprising two or more cells
  • C25B9/73—Assemblies comprising two or more cells of the filter-press type
• • 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
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
  • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• • 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
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04276—Arrangements for managing the electrolyte stream, e.g. heat exchange
• • 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
  • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
  • H01M8/0693—Treatment of the electrolyte residue, e.g. reconcentrating
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
  • H01M8/1023—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/1041—Polymer electrolyte composites, mixtures or blends
  • H01M8/1046—Mixtures of at least one polymer and at least one additive
  • H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
• • 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
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• This invention relates to a method of performing an electrochemical reaction.
• Electrochemical cells exist in which the electrodes are separated by an ion-exchange membrane, for example a solid polymer electrolyte.
• WO-A-03/23890 teaches that ion-exchange materials can be produced based on hydrophilic polymers, i.e. polymers which are inherently able to absorb and transmit water throughout their molecular structure.
• the materials are particularly relevant to hydrogen-oxygen fuel cells, since product water can be redistributed, thereby avoiding local flooding or drying-out of the membrane.
• hydrophilic material can be rendered ionically conducting.
• the first way is to form ionically active sites by co-polymerisation from a solution of ionically active monomers; this methodology is described in WO-A-03/23890.
• a strongly anionic or cationic moiety is formed in the resulting polymer, allowing it to function as a anionic-exchange (AE) or cationic-exchange (CE) material respectively.
• the second way is to incorporate ionically active sites in the material by grafting ionically active monomers.
• ionically active sites in the material by grafting ionically active monomers.
• An example of such a material is Nafion, which becomes ionically conducting when the ionic sites are activated by hydration in demineralised water.
• the third way is by hydration of the hydrophilic material in an acidic or alkaline liquid.
• Hydrophilic materials such as HEMA (2-hydroxyethyl methacrylate) and MMA-VP (methyl methacrylate-vinylpyrrolidone) possess no intrinsic electrical properties and, if hydrated in deionised distilled (DD) water, are good electrical resistors. If, however, these materials are hydrated in an acidic or alkaline solution, they become good conductors.
• a limitation of this approach is that conductivity declines as the electrolyte solution washes out, the material eventually becoming electrically inactive. Such washing out is particularly problematic in electrolysers, where reactant water is normally present in large quantities, and in hydrogen-oxygen fuel cells, where water is produced.
• the present invention addresses the limitations of the third approach and is based on a realisation that, provided the concentration of the electrolyte in the membrane can be maintained, a electrically inactive membrane hydrated with an electrolyte is a viable alternative to other hydrophilic systems.
• the conductivity of a weakly ionic hydrophilic membrane can be augmented by hydrating the membrane in an acidic or alkaline solution.
• the concentration of the electrolyte can be maintained by controlling, for example, the extent of hydration of the membrane.
• a method of performing an electrochemical reaction in an electrochemical cell comprising electrodes separated by a hydrophilic ion-exchange membrane, comprises conducting the reaction in the presence of an aqueous solution of an electrolyte of which the concentration is controlled.
• the cell may be in the form of a fuel cell or an electrolyser.
• a fuel cell running on hydrogen and oxygen
• water is produced in the cell reaction. It follows that sufficient quantities of water must be removed from the membrane, in order to maintain the concentration of the electrolyte. In cases such as this, i.e. where water needs to be removed from the system, removal is preferably accomplished by evaporation. Evaporation can be achieved by using a Peltier cooled “cold spot” located away from the membrane, at which moisture from the warm cell condenses and is removed.
• the extent of hydration can be controlled by limiting the amount of water introduced into the cell. The extent of hydration can be assessed, for example, by monitoring the pH of the membrane during use.
• the hydrophilic material may be ionically inactive, i.e. it possesses no intrinsic electrical properties. In this case, ionic activity is conferred to the material by the electrolyte solution.
• the hydrophilic material may be ionically active, comprising anionic or cationic sites within its structure.
• the aqueous electrolyte augments the ionic activity of the hydrophilic material.
• the invention has particular applicability to weakly active materials. Weakly active materials are those which, when hydrated in DD water, exhibit ionic conductivities which are less than 60%, typically 50%, of that of an industry standard material such as Nafion 117.
• the hydrophilic, material may be obtained using any suitable method known in the art.
• an ionically active material may formed by according to the techniques described in WO-A-03/23890, the contents of which are incorporated in by reference.
• the material is preferably a hydrophilic polymer, obtainable by the (co)polymerisation of monomers such as methyl methacrylate, N-vinyl-2-pyrrolidone or acrylonitrile, and is preferably cross-linked.
• the electrolyte solution may be acidic or alkaline.
• suitable electrolytes include toluenesulphonic acid (TSA), vinylsulphonic acid, acrylamido-(2-methyl)propanesulphonic acid (AMPSA), sodium hydroxide or potassium hydroxide.
• the electrochemical cell is preferably in the form of a membrane-electrode assembly (MEA) or stack of MEAs.
• MEAs and methods for manufacture are well known in the art.
• WO-A-03/23890 describes a “one-step” method for the production of MEAs, which involves forming the membrane by polymerisation in situ.
• a crosslinked hydrophilic polymer was formed by irradiating a mixture containing 35% acrylonitrile, 35% N-vinyl-2-pyrrolidone, 5% allyl methacrylate and 25% deionised distilled water with a dose of 2 megarads in a cobalt 60 source.
• the resulting solid polymer was divided into two samples. The first sample was hydrated in water and its electrical conductivity measured using an AC bridge method. The second sample was hydrated in a solution of 10% by weight TSA in water, after which its electrical conductivity was measured in the same test cell as used for the first sample.
• the conductivity of the second sample was shown to be greater than that of first sample, in the ratio of 5.7:0.07, i.e. 81.4.
• the conductivity of the second sample was also found to be 36% greater than that of a Nafion 117 membrane.
• the second sample was then immersed in an excess of DD water for a period of 14 days, after which its electrical conductivity was measured.
• the “residual” conductivity was found to be only 15% of its initial conductivity, demonstrating that substantial loss of TSA had occurred.
• Subsequent measurements demonstrated a continuing decline in conductivity with time of washing in DD water. Conductivity was recovered by the addition of further TSA to the membrane, so that the original pH was restored.
• a crosslinked hydrophilic polymer was formed by irradiating a mixture containing 24% methyl methacrylate, 72% N-vinyl-2-pyrrolidone and 4% allylmethacrylate with a dose of 2 megarads in a cobalt 60 source.
• the resulting solid polymer was divided into two samples. The first sample was hydrated in water and its electrical conductivity measured using an AC bridge method. The second sample was hydrated in a solution of 10% by weight TSA in water, after which its electrical conductivity was measured in the same test cell as used for the first sample.
• the conductivity of the second sample was shown to be greater than that of first sample, in the ratio of 47.6:0.05, i.e. 952.
• the conductivity of the second sample was also found to be 13% greater than that of a Nafion 117 membrane.
• the second sample was then immersed in an excess of DD water for a period of 14 days and after which its electrical conductivity was measured.
• the “residual” conductivity was found to be only 12% of its initial conductivity, demonstrating that substantial loss of TSA had occurred.
• Subsequent measurements demonstrated a continuing decline in conductivity with time of washing in DD water.
• Conductivity was recovered by the addition of further TSA to the membrane, so that the original pH was restored.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• General Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Automation & Control Theory (AREA)
• Crystallography & Structural Chemistry (AREA)
• Composite Materials (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Fuel Cell (AREA)
• Hybrid Cells (AREA)

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• 2003
  • 2003-12-19 GB GBGB0329459.2A patent/GB0329459D0/en not_active Ceased
• 2004
  • 2004-12-20 CN CNA200480037791XA patent/CN1894817A/zh active Pending
  • 2004-12-20 EA EA200601188A patent/EA010580B1/ru not_active IP Right Cessation
  • 2004-12-20 KR KR1020067011740A patent/KR20060134002A/ko not_active Application Discontinuation
  • 2004-12-20 AU AU2004300328A patent/AU2004300328B2/en not_active Ceased
  • 2004-12-20 NZ NZ547328A patent/NZ547328A/en not_active IP Right Cessation
  • 2004-12-20 US US10/579,658 patent/US20070207350A1/en not_active Abandoned
  • 2004-12-20 CA CA2547797A patent/CA2547797C/en not_active Expired - Fee Related
  • 2004-12-20 JP JP2006543632A patent/JP2007516357A/ja active Pending
  • 2004-12-20 WO PCT/GB2004/005347 patent/WO2005060018A2/en active Application Filing
  • 2004-12-20 EP EP04806148A patent/EP1695400A2/en not_active Withdrawn
• 2006
  • 2006-05-29 ZA ZA2006/04357A patent/ZA200604357B/en unknown
• 2010
  • 2010-09-24 US US12/890,204 patent/US8460832B2/en not_active Expired - Fee Related

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