WO2022210578A1 - 水素ガスの製造方法、水素ガスを製造する装置の運転停止方法及び水素ガス製造装置 - Google Patents

水素ガスの製造方法、水素ガスを製造する装置の運転停止方法及び水素ガス製造装置 Download PDF

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WO2022210578A1
WO2022210578A1 PCT/JP2022/015119 JP2022015119W WO2022210578A1 WO 2022210578 A1 WO2022210578 A1 WO 2022210578A1 JP 2022015119 W JP2022015119 W JP 2022015119W WO 2022210578 A1 WO2022210578 A1 WO 2022210578A1
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electrolysis
current density
hydrogen gas
hydrogen
gas
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English (en)
French (fr)
Japanese (ja)
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浩司 谷口
彦睦 渡邉
拓哉 北畠
祐之輔 中原
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Mitsui Kinzoku Co Ltd
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Mitsui Mining and Smelting Co Ltd
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Priority to JP2023511288A priority Critical patent/JPWO2022210578A1/ja
Priority to EP22780789.8A priority patent/EP4317056A1/en
Priority to US18/278,798 priority patent/US20240141508A1/en
Publication of WO2022210578A1 publication Critical patent/WO2022210578A1/ja
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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
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/02—Preparation of oxygen
    • C01B13/0203—Preparation of oxygen from inorganic compounds
    • C01B13/0207—Water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/054—Electrodes comprising electrocatalysts supported on a carrier
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
    • C25B11/067—Inorganic compound e.g. ITO, silica or titania
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material
    • C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
    • 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
    • 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
    • C25B15/023—Measuring, analysing or testing during electrolytic production
    • 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
    • C25B9/21—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms two or more diaphragms
    • 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
    • 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

  • the present invention relates to a method for producing hydrogen gas and a method for shutting down an apparatus for producing hydrogen gas.
  • the present invention also relates to a hydrogen gas production device.
  • an object of the present invention is to provide a method for producing hydrogen gas, a method for stopping operation of a hydrogen gas production apparatus, and a hydrogen gas production apparatus that can suppress reverse current that occurs when operation is stopped.
  • the present invention is a method for producing hydrogen gas by electrolysis of water, comprising: Prior to stopping the electrolysis, the current density is reduced to a range of more than 0 A/cm 2 and less than the current density in the electrolysis step, as long as the electrolysis does not stop; Maintaining the current density for 1 second or more while introducing gas into at least the hydrogen generating electrode, A method for producing hydrogen gas is provided in which the electrolysis is stopped by lowering the current density to a value at which the electrolysis does not occur.
  • the present invention also provides a method for stopping operation of an apparatus for producing hydrogen gas by electrolysis of water, Prior to stopping the electrolysis, the current density is reduced to a range of more than 0 A/cm 2 and less than the current density in the electrolysis step, as long as the electrolysis does not stop; Maintaining the current density for 1 second or more while introducing gas into at least the hydrogen generating electrode, A shutdown method is provided in which the electrolysis is stopped by reducing the current density to a value at which the electrolysis does not occur.
  • the present invention provides a hydrogen gas production apparatus comprising a storage section storing the procedure of the operation stop method, and a control section for stopping electrolysis of water based on the procedure stored in the storage section. It is a thing.
  • FIG. 1 is a schematic diagram showing a hydrogen gas production apparatus suitable for use in the method for producing hydrogen gas of the present invention.
  • 2(a) and 2(b) are graphs showing current density control methods in the method for producing hydrogen gas according to the present invention.
  • FIG. 3 is a graph showing changes over time in the voltage of the water electrolysis cell in the production of hydrogen gas performed in Examples and Comparative Examples.
  • FIG. 1 schematically shows a hydrogen gas production apparatus suitable for use in the hydrogen production method of the present invention.
  • the water electrolysis apparatus of this embodiment is used to produce hydrogen gas by electrolyzing water to generate hydrogen gas at the cathode and oxygen gas at the anode.
  • the hydrogen gas production apparatus 10 shown in FIG. 1 includes a gas-liquid separation tank 11.
  • the hydrogen gas production apparatus 10 also includes a water electrolysis stack 13 .
  • the gas-liquid separation tank 11 and the water electrolysis stack 13 are connected via a pipeline 11a to allow the electrolyte to flow.
  • the hydrogen gas production device 10 includes a liquid transfer pump 14 .
  • the liquid-sending pump 14 is connected to the water electrolysis stack 13 via a conduit 14 a , so that the electrolyte can be supplied from the liquid-sending pump 14 to the water electrolysis stack 13 .
  • the liquid-sending pump 14 is also connected to the gas-liquid separation tank 11 via the return line 11b. Thereby, the electrolytic solution can be circulated from the gas-liquid separation tank 11 toward the liquid transfer pump 14 .
  • the liquid feed pump 14 is connected to the water replenishment tank 15 via an electrolyte replenishment line 15a.
  • the water replenishment tank 15 is used to replenish the electrolyte consumed by electrolysis.
  • the hydrogen gas production device 10 includes a power supply section 16 .
  • a power supply 16 is used to supply power to the water electrolysis stack 13 .
  • the power supply to the water electrolysis stack 13 by the power supply section 16 is controlled by the control unit 17 .
  • the control unit 17 includes a storage unit 18 that stores procedures for operating and stopping the hydrogen gas production apparatus 10 and a control unit 19 that stops electrolysis of water based on the procedures stored in the storage unit 18. I have.
  • the control unit 17 is connected to the power supply section 16 via a signal line 17a. A command issued from the control unit 17 is transmitted to the power supply section 16 via the signal line 17a.
  • the hydrogen gas production device 10 has a purge gas supply source 20 .
  • a purge gas supply source 20 is connected to the water electrolysis stack 13 via a gas line 20a.
  • An on-off valve 21 is installed in the middle of the gas pipeline 20a. The supply of purge gas from the purge gas supply source 20 to the water electrolysis stack 13 is controlled by opening and closing the on-off valve 21 . Opening and closing of the on-off valve 21 is performed by the control unit 17 through a signal line 17b that electrically connects the on-off valve 21 and the control unit 17 .
  • a command issued from the control unit 17 is transmitted to the on-off valve 21 via the signal line 17b, and the on-off valve 21 opens and closes based on the command.
  • the water electrolysis stack 13 in the hydrogen gas production apparatus 10 can comprise a plurality of water electrolysis cells (not shown). Each water electrolysis cell can be connected in series. Each water electrolysis cell can comprise a hydrogen evolution electrode, an oxygen evolution electrode and a diaphragm separating the electrodes.
  • an appropriate material is used according to the specific mode of water electrolysis.
  • a proton conductive electrolyte membrane for example, can be used as the diaphragm.
  • a membrane include a solid polymer containing a fluoropolymer having a sulfonic acid group, an electrolyte membrane made of a solid polymer containing an aromatic hydrocarbon, and the like.
  • a composite material composed of resins such as polysulfone, polyphenylene sulfide, polyphenylene ether ether ketone ( PEEK), and PTFE, and inorganic hydrophilic particles such as ZrO2 is electrolyzed as a diaphragm.
  • resins such as polysulfone, polyphenylene sulfide, polyphenylene ether ether ketone ( PEEK), and PTFE
  • inorganic hydrophilic particles such as ZrO2
  • each electrode is formed by applying a paste containing a catalyst-carrying carrier in which a catalyst is carried on the surface of conductive carrier particles to each surface of the solid polymer electrolyte membrane. It is preferred to use an electrode catalyst layer.
  • the electrode catalyst layer may contain an ionomer for the purpose of increasing the proton conductivity and increasing the adhesiveness between the catalyst-carrying carrier and the solid polymer electrolyte membrane.
  • a structure in which an electrode catalyst layer is formed on each surface of a solid polymer electrolyte membrane is generally called a CCM (Catalyst Coated Membrane).
  • Bipolar plates functioning as current collectors can also be placed on each side of the CCM. Additionally, gas diffusion layers can be placed between each side of the CCM and the bipolar plate.
  • the hydrogen-evolving electrode and the oxygen-evolving electrode are used for the purpose of increasing the surface area used for electrolysis and efficiently removing hydrogen gas and oxygen gas generated by electrolysis from the surface of the electrode. And it is preferably a porous body.
  • the hydrogen and oxygen evolution poles can comprise various porous materials such as plain woven mesh, perforated metal, expanded metal and metal foam.
  • Niobium, tantalum, titanium, zirconium, tungsten, tin, nickel, cobalt, iron, platinum group elements, and the like can be used as the raw material for the oxygen generating electrode in PEM water electrolysis.
  • the elements used in the hydrogen generating electrode include, for example, molybdenum. In order to achieve the desired catalytic activity and durability, these elements are used in the form of single metals, compounds such as oxides, composite oxides or alloys containing multiple metal elements, or mixtures thereof. can be used.
  • raw material elements for the hydrogen-evolving electrode and the oxygen-evolving electrode include, for example, silver, vanadium, chromium, manganese, yttrium, etc., in addition to the elements used in PEM water electrolysis. These elements can be used in the form of single metals, compounds such as oxides, composite oxides, alloys, or mixtures, as in the case of PEM water electrolysis.
  • the element used in the oxygen generating electrode contains a platinum group element from the viewpoint of smooth water electrolysis, and it is more preferable to use iridium. When iridium is used, it is preferable to use it in the form of an alloy or mixture containing a plurality of metal elements, or an oxide thereof, from the viewpoint of catalytic activity and durability of the catalyst.
  • hafnium oxide, zirconium oxide, fluorine-containing tin oxide, antimony-containing tin oxide, indium-containing tin oxide, carbon, and the like can be used as raw materials.
  • the carbon include a group of carbonaceous materials called carbon black.
  • Fluorine-containing tin oxide or the like can be used as the raw material for the oxygen-evolving electrode.
  • Lanthanoid oxides, transition metal oxides, composite oxides, and the like can be used as raw materials for the hydrogen-evolving electrode and the oxygen-evolving electrode in alkaline water electrolysis.
  • the oxygen generating electrode in each water electrolysis cell is configured so that the electrolyte circulates. Circulation of the electrolytic solution is performed by the above-described liquid-sending pump 14 .
  • the gas-liquid separation tank 11 in the hydrogen gas production device 10 is connected to an electrolysis chamber (not shown) on the oxygen generating electrode side in the water electrolysis stack 13 .
  • a gas-liquid separation tank 11 connected to the electrolytic chamber on the oxygen generating electrode side is used to separate the oxygen gas generated at the oxygen generating electrode from the electrolyte.
  • oxygen gas is generated at the oxygen generating electrode, and the generated oxygen gas flows into the gas-liquid separation tank 11 together with the electrolyte.
  • the oxygen gas moves to the gas phase in the upper layer of the tank, and the electrolytic solution remains in the liquid phase in the lower layer of the tank.
  • the oxygen gas that has moved to the upper layer of the tank is recovered by a gas recovery section (not shown).
  • hydrogen gas is generated at the hydrogen generating electrode, and the generated hydrogen gas flows through the gas recovery pipe 12 to a gas recovery unit (not shown) installed outside the apparatus, and is recovered by the gas recovery unit.
  • the same tank as known in the technical field can be used without particular limitation.
  • the water to be replenished it is convenient to use city water, but it is preferable to use ion-exchanged water, reverse osmosis water, ultrapure water, or the like in consideration of long-term operation stability.
  • a method for producing hydrogen gas by electrolysis of water using the hydrogen gas producing apparatus 10 having the above configuration will be described.
  • the method for producing hydrogen gas according to the present invention is roughly divided into an energization electrolysis step, a step before de-energization, and a de-energization step. Each step will be described below.
  • the liquid-sending pump is activated to distribute and circulate the electrolytic solution to each part of the hydrogen gas production apparatus 10 .
  • a command is sent from the control unit 17 to the power supply unit 16 to supply power to the water electrolysis stack 13 to start energization.
  • a voltage is applied between both electrodes so that the oxygen generating electrode has a relatively positive potential and the hydrogen generating electrode has a relatively negative potential.
  • an oxidation reaction occurs at the oxygen generating electrode to generate oxygen gas
  • a reduction reaction occurs at the hydrogen generating electrode to generate hydrogen gas.
  • An aqueous solution having an alkaline pH in which an alkali salt is dissolved can also be used.
  • an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or the like can be used.
  • concentration of the water-soluble alkali salt in the aqueous solution having a pH in the alkaline range can be set, for example, from 20% by mass to 50% by mass, and particularly from 25% by mass to 40% by mass.
  • the current electrolysis step can be performed at room temperature (15° C.-25° C.) without heating, or when the electrolyte is water, the electrolyte is less likely to cause corrosion, so the electrolyte can be heated. can.
  • the electrolytic solution can be heated to, for example, about 150°C.
  • the current density IA in the current electrolysis step is generally preferably more than 0.1 A/cm 2 and 10 A/cm 2 or less from the viewpoint of stability of water electrolysis and efficient generation of hydrogen gas. From this viewpoint, the current density IA of water electrolysis is more preferably 0.5 A /cm 2 or more and 7 A/cm 2 or less, and more preferably 1 A/cm 2 or more and 4 A/cm 2 or less.
  • the current density IA in the current electrolysis step may be kept constant within the aforementioned range, or may vary within the aforementioned range. For example, the current density IA may be increased or decreased, gradually decreased, or gradually increased.
  • the current density in the present invention means the density of the current flowing between the oxygen generating electrode and the hydrogen generating electrode, that is, between the electrodes.
  • the method for producing hydrogen gas according to the present invention has one of the characteristics in the step before de-energization, in other words, the method for stopping the operation of the hydrogen gas production apparatus 10 .
  • the current density is lowered to a current density I B that is lower than the current density I A in the electrolysis step, prior to stopping the electrolysis of water that has been performed in the electrolysis step.
  • the current density I B is not lowered to values where electrolysis of water does not occur.
  • a current is applied within a range in which the electrolysis does not stop, and the water is electrolyzed, although the degree is low. Whether or not the electrolysis has stopped can be judged from the value of the current density. Specifically, when the current density exceeds 0 A/cm 2 , it can be determined that electrolysis has occurred.
  • the current density IB in the step before energization is stopped is set to a value less than the current density IA in the energization electrolysis step, if the current density IA in the energization electrolysis step fluctuates, the current density I B is set lower than the lowest value among the current densities IA in the current electrolysis step.
  • the current density I B in the step before stopping the energization is lower than the current density I A in the energization electrolysis step, regardless of the scale of the water electrolysis stack 13 and the area of the electrodes. It has been found that setting the current to 1 A/cm 2 or less is advantageous from the viewpoint of effectively suppressing the reverse current that occurs when water electrolysis is stopped. That is, the current density IB in the step before stopping the energization is preferably set to more than 0 A /cm 2 and not more than 1 A/cm 2 on the condition that it is lower than IA and water electrolysis occurs.
  • the current density I B it is more preferable to set the current density I B to 0.005 A/cm 2 or more and 0.5 A/cm 2 or less, and more preferably 0.008 A/cm 2 or more and 0.1 A/cm 2 or more. It is more preferable to set it to cm 2 or less.
  • the current density I B in the step before energization is stopped should be set so that the value of I B / IA is preferably 0.0005 or more and 0.5 or less in relation to the current density I A in the energization electrolysis step.
  • the value of I B / IA it is advantageous from the viewpoint of effectively suppressing the reverse current that occurs when water electrolysis is stopped. From the viewpoint of making this advantage more remarkable, it is more preferable to set the value of I B / IA to 0.001 or more and 0.3 or less, and more preferably 0.001 or more and 0.15 or less. preferable.
  • the current density IB may be kept constant within the range described above, or may vary within the range described above.
  • the current density IB may be increased, decreased, or gradually decreased.
  • the current density IB during the continuation of the pre - stopping step should not be greater than or equal to the current density IA in the electrolysis step. From the viewpoint of effectively suppressing the reverse current that occurs when the operation of water electrolysis is stopped, it is preferable that the current density IB is kept as constant as possible during the continuation of the step before stopping the energization.
  • the current density can be decreased stepwise from IA to IB as shown in FIG. 2(a). That is, the transition time ⁇ t for the current density to decrease from I A to I B can be zero (or a time infinitely close to zero). Alternatively, the current density may be tapered from IA to IB, as shown in FIG. 2( b ). In the latter case, the transition time ⁇ t for the current density to decrease from I A to I B is preferably 1 second or more and 300 seconds or less from the viewpoint of suppressing the generation of reverse current due to the potential change between the electrodes. From this point of view, the transition time ⁇ t is more preferably 120 seconds or less, and even more preferably 60 seconds or less. When comparing the current density reduction method shown in FIG. 2(a) with the current density reduction method shown in FIG. This is preferable from the viewpoint of more effectively suppressing the reverse current.
  • the current density IB is preferably maintained for 30 seconds or longer, still more preferably for 40 seconds or longer, and even more preferably for 50 seconds or longer.
  • the upper limit of the holding time of the current density I B in the step before stopping the energization is not particularly limited, but from the viewpoint of the balance between the suppression of the reverse current and the efficient production of hydrogen gas, it is preferably 30000 seconds or less. It is preferably 12000 seconds or less, more preferably 1000 seconds or less, and even more preferably 100 seconds or less.
  • both electrodes are maintained so that the potential of the oxygen generating electrode is always higher than the overvoltage of the water electrolysis reaction and is higher than that of the hydrogen generating electrode until the electrolysis of water is stopped. is preferably controlled by the controller 19 .
  • the potential difference ⁇ V between the oxygen generating electrode and the hydrogen generating electrode is preferably 0.1 mV or more, more preferably 0.3 mV or more, provided that it is equal to or higher than the overvoltage of the water electrolysis reaction.
  • it is more preferably 0.5 mV or more.
  • the value of the overvoltage often depends on the type of device, as an example, it is preferably 1500 mV or more in this embodiment.
  • the upper limit of the potential difference is preferably controlled so as not to excessively exceed the overvoltage of the electrolysis reaction of water.
  • the potential difference is preferably 2500 mV or less, more preferably 2000 mV or less.
  • a purge gas into at least the hydrogen generating electrode together with the operation of reducing the current density.
  • the purge gas By introducing the purge gas, hydrogen gas remaining in the hydrogen generating electrode can be forced out of the system. That is, the hydrogen gas, which is the raw material for the reaction of the fuel cell, which is the reverse reaction of water electrolysis, can be removed from the system, and the reverse current generated when the operation of water electrolysis is stopped can be effectively suppressed. From this point of view, blowing the purge gas toward the hydrogen generating electrode is advantageous from the viewpoint of forced discharge of the hydrogen gas remaining in the hydrogen generating electrode.
  • the purge gas is used for the purpose of suppressing reverse current, in other words, for the purpose of suppressing the occurrence of fuel cell reactions.
  • the purge gas is preferably electrochemically inert to fuel cell reactions. From this point of view, it is preferable to use at least one selected from the group consisting of nitrogen and rare gases as the purge gas, and a mixed gas consisting of gases selected from these groups can also be used.
  • the rare gas for example, argon, helium, neon, or the like can be used.
  • the introduction of the purge gas to the hydrogen - evolving electrode may be performed at the same time as the current density is lowered to IB , or after the current density has been lowered to IB. Since the reverse current occurs when water electrolysis is stopped, the generation of the reverse current can be suppressed by introducing the purge gas at an arbitrary timing while the step before stopping the energization is continued. However, from the viewpoint of more effectively suppressing the generation of the reverse current, it is preferable to introduce the purge gas at the same time as the current density is lowered to IB .
  • the purge gas may be introduced into the hydrogen-producing electrode continuously or intermittently as long as the hydrogen gas remaining in the hydrogen-producing electrode can be forcibly discharged.
  • the amount of purge gas introduced may be constant or may vary over time.
  • the introduction period may be constant or irregular.
  • the amount of the purge gas introduced into the hydrogen generating electrode is not particularly limited as long as the hydrogen gas remaining in the hydrogen generating electrode can be forcibly discharged.
  • the value of L/S which is the ratio of the introduction amount L (Nm 3 /min) of the purge gas to the apparent area S (m 2 ) of the hydrogen generating electrode, is 0.1 or more and 20 or less. It has been found that introducing a purge gas in such a manner yields satisfactory results.
  • the purge gas may be similarly introduced to the oxygen generating electrode.
  • the introduction of the purge gas to the oxygen generating electrode can be performed under the same conditions as the introduction of the purge gas to the hydrogen generating electrode.
  • the electrolysis reaction of water is stopped by lowering the current density to a value at which the electrolysis reaction does not occur. Whether or not the electrolysis reaction has stopped occurring can be judged from the value of the current density. When the current density value is 0 A/cm 2 or less, it can be determined that the electrolysis reaction has stopped.
  • the current density range is preferably 0 A/cm 2 or less, more preferably 0 A/cm 2 . In conventional water electrolysis, since the above-mentioned step before stopping the energization is not performed, a reverse current is generated due to the stop of the electrolysis reaction.
  • the degree is extremely low, so serious deterioration of the electrode catalyst is unlikely to occur.
  • the voltage of each water electrolysis cell in the water electrolysis stack 13 becomes 0 V, which is the OCV.
  • the introduction of the purge gas may be stopped when the current density is lowered to the range where the electrolysis reaction does not occur.
  • the present invention even if the water electrolysis reaction is stopped, reverse current is less likely to occur, so deterioration of the electrode catalyst is effectively suppressed. Therefore, there is an advantage that the electrode catalyst is less likely to be damaged even if an intermittent operation for restarting water electrolysis is performed after water electrolysis is stopped in the de-energization step.
  • the hydrogen gas production apparatus 10 shown in FIG. 1 is merely an example of an apparatus used in the hydrogen gas production method of the present invention. can be implemented.
  • the electrolyte is supplied to the oxygen generating electrode by the liquid feed pump 14, but in addition, the electrolyte may be supplied to the hydrogen generating electrode. .
  • Such an electrolytic solution supply mode is advantageous when alkaline water electrolysis is performed as water electrolysis.
  • the electrolyte is also supplied to the hydrogen generating electrode, it is preferable to install a gas-liquid separation tank also on the hydrogen generating electrode.
  • a film of Nafion (registered trademark) 117 manufactured by DuPont was used as the solid polymer electrolyte, and the above catalyst layer was superimposed on each surface of this film and heat-pressed. After that, the CCM was obtained by peeling off the Teflon (registered trademark) sheet. The amount of iridium in the oxygen evolution electrode was 0.05 mg/cm 2 .
  • the electrolysis reaction of water continued, albeit to a lesser degree.
  • a certain amount of nitrogen gas was continuously introduced into the hydrogen generating electrode as the current density decreased.
  • the ratio L/S of the introduction amount L (Nm 3 /min) of nitrogen gas to the apparent area S (m 2 ) of the hydrogen generating electrode was set to 1.
  • Stopping the current The current density was stepwise lowered to 0 A/cm 2 , the open-circuit voltage of the water electrolysis cell was set to 0 V, and this state was maintained for 60 seconds.
  • the electrolysis reaction of water stopped completely.
  • the introduction of nitrogen gas was stopped when the current density was lowered to 0 A/cm 2 .
  • step (i) in each cycle of (5) above the cell voltage at which the current density was 3 A/cm 2 was measured, and changes in cell voltage with an increase in the number of cycles were evaluated. The results are shown in FIG.
  • Example 1 the hydrogen gas production apparatus produced in Example 1 was used, and the following (i')-(iii') operation protocol was set as one cycle, and this cycle was repeated 1000 times to intermittently supply hydrogen gas. purposely manufactured.
  • Electric electrolysis step Same as (i) in Example 1.
  • Process before de-energization This process is not performed.
  • Stopping the current The current density was stepwise lowered to 0 A/cm 2 , the open-circuit voltage of the water electrolysis cell was set to 0 V, and this state was maintained for 60 seconds.
  • step (i′) in each cycle the cell voltage at which the current density was 3 A/cm 2 was measured to evaluate changes in cell voltage as the number of cycles increased. The results are shown in FIG.
  • Example 1 even when the number of cycles increased, no increase in cell voltage was observed, but rather the cell voltage decreased. This means that even if the hydrogen gas production apparatus is operated intermittently, deterioration of the electrode catalyst is unlikely to occur. On the other hand, in Comparative Example 1, the cell voltage increases as the number of cycles increases. This means that the intermittent operation of the hydrogen gas production apparatus causes deterioration of the electrode catalyst.
  • the reverse current generated when the hydrogen gas production device is stopped is suppressed, thereby suppressing deterioration of the electrode catalyst.

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PCT/JP2022/015119 2021-03-30 2022-03-28 水素ガスの製造方法、水素ガスを製造する装置の運転停止方法及び水素ガス製造装置 Ceased WO2022210578A1 (ja)

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JP7657883B1 (ja) 2023-10-13 2025-04-07 三菱重工業株式会社 水素生成システム及びその制御方法
DE102024201686A1 (de) 2024-02-23 2025-08-28 Robert Bosch Gesellschaft mit beschränkter Haftung Vorrichtung und Verfahren zum Inertisieren eines Elektrolysesystems

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JPS5524971A (en) * 1978-08-14 1980-02-22 Tokuyama Soda Co Ltd Current feeding to alkali metal salt electrolytic bath
JPS6213589A (ja) * 1985-07-11 1987-01-22 Mitsubishi Heavy Ind Ltd 電解槽における逆電流の防止方法および装置
JP2014091838A (ja) * 2012-10-31 2014-05-19 Chlorine Engineers Corp Ltd イオン交換膜電解槽の逆電流防止方法
JP2014095128A (ja) * 2012-11-09 2014-05-22 Asahi Kasei Chemicals Corp 電解システム及び電解システムの電気絶縁方法
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JP2025067514A (ja) * 2023-10-13 2025-04-24 三菱重工業株式会社 水素生成システム及びその制御方法
DE102024201686A1 (de) 2024-02-23 2025-08-28 Robert Bosch Gesellschaft mit beschränkter Haftung Vorrichtung und Verfahren zum Inertisieren eines Elektrolysesystems

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