JP6424640B2 - Electrode and electrochemical device using the same - Google Patents

Description

  The present invention relates to an electrode and an electrochemical device using the same.

According to the United Nations Intergovernmental Panel on Climate Change (IPCC), global warming due to the increase of atmospheric CO ₂ concentration is an important environmental issue. The hydrogen society is proposed as the measure. The burning of fossil fuel produces CO ₂ , but the burning of hydrogen produces water, so it does not raise the concentration of CO _{2 in} the atmosphere. A fuel cell is a device that generates electricity by reacting a reaction gas such as hydrogen with oxygen, and is produced as a major environmentally-friendly application because water is generated and CO ₂ is not generated. Also, because hydrogen is explosive, it is expected that many hydrogen sensors that detect hydrogen leakage will be required for safety measures.

  The electrochemical device includes a fuel cell and a hydrogen sensor, and includes an anode that is an electrode that emits electrons, a cathode that receives electrons, and an electrolyte between which ion conduction is performed. The fuel cell is composed of two gas diffusion electrodes, an anode and a cathode, and a solid electrolyte. A reactive gas such as hydrogen, methane or alcohol is supplied to the anode, and an oxygen gas is supplied to the cathode. Since a catalyst is supported on the surface of the gas diffusion electrode, it promotes the oxidation of hydrogen and the reduction of oxygen. The protons generated by the oxidation of hydrogen and the oxygen ions generated by the reduction of oxygen react through the solid electrolyte to form water. On the other hand, also in the hydrogen sensor, hydrogen gas is oxidized to protons by the catalyst on the anode, and the hydrogen gas concentration is measured by the resulting current.

  These electrochemical devices require efficient conversion of the reaction gas to protons by the catalyst.

  In the gas diffusion electrode, hydrogen gas is oxidized to protons on the catalyst surface and moves to the on-conductive solid electrolyte contained in the gas diffusion electrode. On the other hand, in the gas diffusion electrode of the counter electrode, the oxygen gas is reduced to oxygen ions, which move to the solid electrolyte. The protons move in the ion conductive solid electrolyte and react with oxygen ions to form water. Thus, in the electrochemical device, a circuit is formed by electrons and ions. However, if the distance between the catalyst surface and the ion conductive solid electrolyte is long enough that protons generated on the catalyst surface can not move to the ion conductive solid electrolyte, the circuit is cut off between the catalyst surface and the solid electrolyte. Can not function as Thus, the design of the three-phase interface of the catalyst, the ion conducting solid electrolyte, and the gas at the electrode is important for the performance of the electrochemical device.

  In Patent Document 1, in order to provide a method for producing an electrolyte membrane-electrode assembly having excellent power generation performance in a fuel cell, reaggregation of the electrolyte is suppressed and a sufficient and uniform contact state between the catalyst and the polymer electrolyte is maintained. It has been described that. In the example, an electrode catalyst in which platinum is supported on carbon black is added to a polymer electrolyte dispersion, mixed and dispersed, and a catalyst ink prepared by adding a degassing operation is spray-coated on a solid polymer electrolyte membrane. A method of manufacturing an electrolyte membrane-electrode assembly is described.

Patent No. 5458503 gazette

  In the technology described in Patent Document 1, a catalyst ink composed of a catalyst, carbon and a polymer electrolyte is manufactured by simply mixing. Here, the polymer electrolyte is an ion conductive solid electrolyte. In this manufacturing method, a three-phase interface consisting of a catalyst, carbon, and a polymer electrolyte, which is a reaction site of gas, is created by accident. That is, since a solid electrolyte is not necessarily present in the vicinity of protons generated on the catalyst surface, the distance between the catalyst surface and the polymer electrolyte is the distance that protons generated on the catalyst surface can move to the polymer electrolyte. The frequency at which such a three-phase interface is created is not necessarily high. Therefore, the technology described in Patent Document 1 has a problem that the conversion efficiency of the reaction gas into ions is low, and to increase the conversion efficiency, it is necessary to increase the usage amount of a scarce resource and expensive catalyst.

  The present invention has been made in view of such problems, and provides an electrode having a high conversion efficiency of reaction gas to ions even if the amount of catalyst metal is small, and an electrochemical device using the electrode. The purpose is to

  The electrode of the present invention includes a conductive porous body having an electron conductor and an ion conductive solid electrolyte, and metal nanoparticles held by the conductive porous body, and the electron is formed on the surface of the conductive porous body. It is characterized in that the amount of the metal nanoparticles in contact with the conductor and the ion conductive solid electrolyte is larger than the amount of the metal nanoparticles contained in the inside of the conductive porous body.

  The metal nanoparticles function as a catalyst in contact with the electron conductor. In addition, the metal nanoparticles are in contact with the ion conductive solid electrolyte, whereby ions generated on the surface of the metal nanoparticle (catalyst) can be smoothly transferred to the ion conductive solid electrolyte. Therefore, in such an electrode, many metal nanoparticles in contact with the electron conductor and the ion conductive solid electrolyte are unevenly distributed on the surface of the conductive porous body in contact with a large flow rate of reaction gas, so metal nano that functions as a catalyst A three-phase interface composed of particles, ion conductive solid electrolyte and reaction gas is present at high frequency, and the conversion amount of reaction gas to ions relative to the amount of metal nanoparticles (the amount of catalyst metal) is improved.

  The surface of the conductive porous body in the present invention is a surface in which the conductive porous body is in contact with a gas, and includes the surface of the through hole in the conductive porous body. Moreover, the inside of the conductive porous body in the present invention is a portion of the conductive porous body not in contact with the gas.

  The ion conductive solid electrolyte in the present invention is a solid that exhibits electrical conductivity by the movement of ions. Here, solid includes gel. A gel is a substance containing a liquid in the interstices of a crosslinked polymer, and has high viscosity, so it loses fluidity and is solid as a whole.

  In the electrode of the present invention, preferably, the metal nanoparticles are held on the exposed surface of the electron conductor on the surface of the conductive porous body. Since metal nanoparticles need to be in contact with an electron conductor in order to function as a catalyst, such a configuration allows metal nanoparticles to function efficiently as a catalyst, and the amount of metal nanoparticles Can be reduced. In addition, such a configuration can be easily produced by electrodeposition of metal nanoparticles on the surface of the electron conductor.

  In the electrode of the present invention, it is preferable that the ion conductive solid electrolyte be formed by solidifying or polymerizing an ionic liquid. Since the ionic liquid does not evaporate, maintenance such as water replenishment is unnecessary, the reliability is high, and the operating temperature can be 100 ° C. or higher.

  The electrochemical device of the present invention uses an ion conductive solid electrolyte and the above electrode. Thereby, even if the amount of metal nanoparticles (the amount of catalyst metal) is small, it is possible to provide an electrochemical device with a high conversion efficiency of the reaction gas into ions.

  According to the present invention, it is possible to provide an electrode having a high conversion efficiency of reaction gas to protons, and an electrochemical device using the electrode, even with a small amount of catalyst.

FIG. 1 is a schematic view of a fuel cell according to an embodiment of the present invention. FIG. 2 is a schematic view of a hydrogen sensor according to an embodiment of the present invention. FIG. 3 is a conceptual view of an electrode according to an embodiment of the present invention. FIG. 4 is a conceptual view of a conventional electrode. FIG. 5 is an enlarged view of a portion of an electrode of an embodiment of the present invention. FIG. 6 is a partially enlarged view of a conventional electrode.

  Preferred embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those which can be easily conceived by those skilled in the art, substantially the same components, and equivalents. Furthermore, the components described below can be combined as appropriate. In addition, various omissions, replacements or modifications of the components can be made without departing from the scope of the present invention.

  FIG. 1 shows a schematic view of a fuel cell 1 as an example of the electrochemical device of the present invention. As shown in FIG. 1, the fuel cell 1 is provided in the metal nanoparticle attached electrode 3, the gas diffusion electrode 4, the separator 6, and the separator 6 on both sides (anode side and cathode side) of the ion conductive solid electrolyte membrane 2. The gas flow path 5 is provided.

  Here, hydrogen gas and oxygen gas will be described as an example of the reaction gas. On the anode side, hydrogen gas is introduced into the gas flow channel 5, and the hydrogen gas diffuses and moves in the gap of the gas diffusion electrode 4, diffuses into the metal nanoparticle-attached electrode 3 and is oxidized to protons. The protons move through the ion conductive solid electrolyte membrane 2 and reach the cathode side. At the cathode side, oxygen gas is introduced into the gas flow channel 5, and oxygen gas diffuses and moves in the gap of the gas diffusion electrode 4, diffuses in the metal nanoparticle attached electrode 3 and is reduced to oxygen ions. The oxygen ions move through the ion conductive solid electrolyte membrane 2 and react with the protons reaching the cathode side to form water, which is discharged. These series of reactions create a potential difference between the anode and the cathode. When an external load, such as a light bulb, is connected between the anode and the cathode, current flows through the light bulb to emit light. Here, as the gas diffusion electrode 4, it is preferable to use a stable porous conductive material such as carbon fiber which is not easily oxidized.

  Next, an example of a hydrogen sensor will be described as another example of the electrochemical device of the present invention.

  FIG. 2 shows a schematic view of the hydrogen sensor 7. The hydrogen sensor includes a current detection type and a voltage detection type. Here, the current detection type will be described as an example. The hydrogen sensor 7 is provided with a metal nanoparticle attached electrode 3 and a gas diffusion electrode 4 on both sides (anode side and cathode side) of the ion conductive solid electrolyte membrane 2, and further is provided with a reference electrode 8 and an external circuit 9.

  Here, a potentiostat is used for the external circuit 9. The potentiostat can control the working electrode to an arbitrary potential relative to the reference electrode 8 to measure the current flowing between the working electrode and the counter electrode. This current is proportional to the reaction rate of the electrochemical reaction, and the hydrogen gas concentration can be determined by measuring the current value at which hydrogen gas is oxidized to protons. The gas diffusion electrode 4 on the anode side is connected to the working electrode terminal W of the potentiostat, the reference electrode 8 of the hydrogen sensor to the reference electrode terminal R, and the gas diffusion electrode 4 on the cathode side to the counter electrode terminal C. Since the reference electrode 8 exhibits a constant potential, the gas diffusion electrode 4 on the anode side, which is the working electrode, and the metal nanoparticle attached electrode 3 as a working electrode are held at a potential at which hydrogen is oxidized to protons. Hydrogen gas diffuses and moves through the gap of the gas diffusion electrode 4 on the anode side, diffuses into the metal nanoparticle-attached electrode 3 and is oxidized to protons. The protons move in the ion conductive solid electrolyte membrane 2 and reach the cathode side. At the cathode side, air containing oxygen gas is introduced, oxygen gas diffuses and moves in the gap of the gas diffusion electrode 4, and is diffused into the metal nanoparticle attached electrode 3 to be reduced to oxygen ions, and an ion conductive solid electrolyte membrane 2 move to react with the protons reaching the cathode side to form water, which is discharged. From the current value detected by the potentiostat which is the external circuit 9 from this series of electrochemical reactions, the hydrogen gas concentration is determined using a calibration curve prepared in advance. The calculation from the current value to the hydrogen gas may be performed by a computer using software.

  Next, the metal nanoparticle attached electrode 3 of the present embodiment, which is an example of the electrode of the present invention, will be described. The conceptual diagram of the metal nanoparticle provided electrode 3 of this embodiment is shown in FIG. On the other hand, in the prior art, a catalyst ink comprising a catalyst metal 13x, a carbon 10x constituting the conductive porous body 12x, and a polymer electrolyte which is the ion conductive solid electrolyte 11x in FIG. FIG. 6 shows a conceptual view of an electrode 3x of FIG.

  As shown in FIG. 3, the metal nanoparticle attached electrode 3 of the present embodiment includes a conductive porous body 12 having an electron conductor 10 and an ion conductive solid electrolyte 11, and a metal held by the conductive porous body 12. And nanoparticles 13. A part of metal nanoparticles 13 is held in contact with the electron conductor 10 and the ion conductive solid electrolyte 11 on the surface of the conductive porous body 12, and the electron conductor 10 and the ion conductive solid are on the surface of the conductive porous body 12 The amount of metal nanoparticles 13 in contact with the electrolyte 11 is larger than the amount of metal nanoparticles 13 contained in the inside of the conductive porous body 12. In the metal nanoparticle attached electrode 3 of the present embodiment, the metal nanoparticles 13 are held on the surface of the conductive porous body 12, and the metal nanoparticles 13 are not contained inside the conductive porous body 12. Further, on the surface of the conductive porous body 12, the metal nanoparticles 13 are held on the exposed surface of the electron conductor 10. In addition, the metal nanoparticles 13 have catalytic activity.

  On the other hand, as shown in FIG. 4, since the conventional electrode 3x is produced by mixing the electron conductor carbon 10x, the ion conductive solid electrolyte 11x and the catalyst metal 13x, the catalyst metal 14 is It exists uniformly not only on the surface of the conductive porous body 12x but also on the inside.

  The electron conductor 10 has a function of supplying electrons to the metal nanoparticles 13 as a catalyst. The metal nanoparticles 13 have catalytic activity and convert the reaction gas into ions. The ion conductive solid electrolyte 11 conducts ions converted from the reaction gas.

  The conductive porous body 12 is a porous body having a through hole as a hole, and reaction gas flows smoothly through the inside of the through hole. The surface of the conductive porous body 12 in the present embodiment is a surface in which the conductive porous body 12 is in contact with the reaction gas, and includes the surface of the through hole of the conductive porous body 12. Further, the inside of the conductive porous body 12 in the present embodiment is a portion of the conductive porous body 12 not in contact with the reaction gas.

  The electron conductor 10 may be a solid such as a metal, an inorganic compound, or carbon. Further, as the electron conductor 10, in order to resist chemical changes such as deterioration, corrosion, oxidation, hydrogen embrittlement, and physical destruction, those in which carbon particles are bound can be preferably used. The carbon particles are preferably acetylene black, ketjen black, mesophase pitch, graphite, soft graphitizable carbon and the like. In addition, carbon fibers, carbon nanotubes, carbon nanohorns and the like can also be used.

  The metal nanoparticles 13 may be any metal having catalytic activity. For example, transition metals such as platinum, gold, iridium, rhodium, osmium, palladium, silver, rhodium, ruthenium, nickel, copper, cobalt, iron, etc., metal mixtures selected from these groups, or alloys selected from these groups Can be mentioned. The size of the metal nanoparticles 13 is 1 to 1000 nm, preferably 3 to 100 nm, and more preferably 5 to 20 nm. Small particle sizes are difficult to analyze, and large particle sizes increase the total metal content with the same catalytic activity.

  The ion conductive solid electrolyte membrane 2 and the ion conductive solid electrolyte 11 are solids that exhibit electrical conductivity by the movement of ions such as protons. Here, the solid includes a gel. A gel is a substance containing a liquid in the interstices of a crosslinked polymer, and has high viscosity, so it loses fluidity and is solid as a whole. For example, sulfonic acid type perfluorocarbon polymer, perfluorocarbon polymer having phosphonic acid group or carboxylic acid group, sulfonated polyetheretherketone, sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polysulfone, SEBS (styrene-( Examples thereof include sulfonated products of ethylene-butylene) -styrene, sulfonated polyphenylene sulfide, sulfonated polyphenylene oxide, sulfonated polyetherimide, sulfonated polyimide, aromatic polyether ether ketone, solid of ionic liquid, and the like.

  The ion conductive solid electrolyte membrane 2 and the ion conductive solid electrolyte 11 are preferably particles obtained by forming a solid obtained by gelling or polymerizing an ionic liquid. Since the ionic liquid does not evaporate, maintenance such as water replenishment is unnecessary, the reliability is high, and the operating temperature can be 100 ° C. or higher. The gelation of the ionic liquid is carried out by adding a gelling agent to the ionic liquid. Examples of the gelling agent include monomers having two or more thermally polymerizable polymerizable groups per molecule, or oligomers, copolymerized oligomers, and the like. As the gelling component, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol which forms an acrylic polymer Difunctional acrylates such as diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate and pentaerythritol triacrylate 3 Functional acrylate, tetratrimethyl acrylate such as ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, etc. Rate, and, like the methacrylate monomers. Besides these, monomers such as urethane acrylate and urethane methacrylate, copolymer oligomers of these, and copolymer oligomers with acrylonitrile may be mentioned. Also usable are polymers which can be dissolved in a plasticizer and gelled, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, sulfonated polyimide and the like.

  The ionic liquid used for the ion conductive solid electrolyte membrane 2 and the ion conductive solid electrolyte 11 is preferably a proton conductive ionic liquid when hydrogen gas is used as a reaction gas. The proton conducting ionic liquid is synthesized by the neutralization reaction of a Bronsted acid and a Bronsted base. The proton conducting ionic liquid preferably has high activity N—H protons. The proton conducting ionic liquid includes, for example, salts of the following cations and anions. The cation may be 4,4'-trimethylenediamine, piperidine, benzimidazole, 1,2,4-triazole, morpholine, butylamine, dipropylamine, pyridine, imidazole, pyrazole, diethylmethylamine triethylammonium, diethylmethylammonium, Examples include dimethylethyl ammonium, ethyl ammonium, a-picolinium, pyridinium, 1,8-bis (dimethylamino) naphthalene, 2,6-di-tert-butylpyridine, guanidine, and their derivative cations. Anions such as phosphoric acid, borofluoric acid, sulfuric acid, nitric acid, acetic acid, trifluoromethanesulfonate, trifluoromethylsulfonylamide, trifluoromethanesulfonate, and fluorohydrogenate tetrachloroaluminic acid, bis (trifluoromethanesulfonyl) imide, methyl And sulfonates and derivatives thereof.

  The conductive porous body 12 is made of, for example, carbon particles as the electron conductor 10 and a gelled ionic liquid as the ion conductive solid electrolyte 11.

  In order to make the electrode of the present embodiment, for example, particles of the electron conductor 10 and particles of the ion conductive solid electrolyte 11 are mixed and formed into the conductive porous body 12, and then the conductive porous body 12 is used as the electrode The metal nanoparticles 13 may be electrodeposited on the surface of the conductive porous body 12 in an ionic liquid. Among the surfaces of the conductive porous body 12, the metal nanoparticles 13 are electrodeposited on the surface of the electron conductor 10 in contact with the ionic liquid. The surface of the electron conductor 10 which is in contact with the ion conductive solid electrolyte 11 can not be in contact with the ionic liquid, but the surface in contact with the ionic liquid, that is, the exposed surface which is later in contact with gas The metal nanoparticles 13 can be electrodeposited on the surface exposed from the conductive solid electrolyte 11). Thereby, the metal nanoparticles 13 are held on the exposed surface of the electron conductor 10.

  A part of the metal nanoparticles 13 electrodeposited on the surface of the electron conductor 10, that is, the metal nanoparticles 13 near the boundary between the electron conductor 10 and the ion conductive solid electrolyte 11, comprises the electron conductor 10 and the ion conductive solid It contacts both of the electrolytes 11. As a result, a three-phase interface of the metal nanoparticles 13, the ion conductive solid electrolyte 11 and the reaction gas can be efficiently produced on the surface of the conductive porous body 12. Moreover, it is possible to electrodeposit the metal nanoparticle 13 which is a catalyst from an ionic liquid. Some ionic liquids have strong inhibition with metals, which strongly adsorb to metals or coordinate to metal ions. Because of this action, the metal remains in nucleation and can not continue crystal growth, so the nanoparticles are electrodeposited. When a metal such as platinum having high catalytic activity is made into nanoparticles, due to the size of its specific surface area, a small catalytic amount can have high catalytic activity.

  Next, the operation of the electrode 3 of the present embodiment will be described. In the metal nanoparticle attached electrode 3 of the present embodiment, the amount of the metal nanoparticles 13 in contact with the electron conductor 10 and the ion conductive solid electrolyte 11 on the surface of the conductive porous body 12 is the inside of the conductive porous body 12 More than the amount of metal nanoparticles 13 contained therein. The metal nanoparticles 13 function as a catalyst by being in contact with the electron conductor 10. Further, since the metal nanoparticles 13 are in contact with the ion conductive solid electrolyte 11, ions generated on the surface of the metal nanoparticle 13 as a catalyst can smoothly move to the ion conductive solid electrolyte 11.

  Therefore, in such an electrode 3, many metal nanoparticles 13 in contact with the electron conductor 10 and the ion conductive solid electrolyte 11 are localized on the surface of the conductive porous body 12 in contact with the reaction gas with a large flow rate. A three-phase interface composed of metal nanoparticles 13 functioning as a catalyst, an ion conductive solid electrolyte 11 and a reaction gas is present at high frequency, and ions of reaction gas with respect to the amount of metal nanoparticles 13 (amount of catalyst metal) The amount of conversion of

On the other hand, the conventional electrode 3x is manufactured by simply mixing a catalyst metal 13x, carbon 10x which is an electron conductor, and an ion conductive solid electrolyte 11x. In this manufacturing method, a three-phase interface consisting of the catalyst metal 13x, the catalyst metal 13x, and the ion conductive solid electrolyte 11x, which is the reaction site of the gas, is created by accident. That is, since the ion conductive solid electrolyte 11x is not necessarily present in the vicinity of the proton generated on the surface of the catalyst metal 13x, the distance between the surface of the catalyst metal 13x and the ion conductive solid electrolyte 11x is the catalyst metal 13x. The frequency at which the three-phase interface is formed such that the protons generated on the surface of the surface can move to the ion conductive solid electrolyte 11x is not necessarily high.

  FIG. 5 is an enlarged view of a part of the electrode 3 of the present embodiment. FIG. 6 is a partially enlarged view of the conventional electrode 3x. In FIG. 5, the three-phase interface 16 comprised with the metal nanoparticle 13, the ion conductive solid electrolyte 11, and reaction gas is shown. FIG. 6 shows a three-phase interface 16 composed of a catalyst metal 13x, an ion conductive solid electrolyte 11x, and a reaction gas. It shows a three-phase interface 16x composed of the two catalysts, the ion conductive solid electrolyte, and the gas. As shown in FIG. 5, in the electrode 3 of the present embodiment, the three-phase interface 16 extends around the ion conductive solid electrolyte 11. However, as shown in FIG. 6, in the conventional electrode 3x, the three-phase interface 16x is accidentally formed, and the area is never large.

  In the metal nanoparticle attached electrode 3 of the present embodiment, the metal nanoparticles 13 are held on the exposed surface of the electron conductor 10 on the surface of the conductive porous body 12. Since the metal nanoparticles 13 need to be in contact with the electron conductor 10 in order to function as a catalyst, this configuration allows the metal nanoparticles 13 to function efficiently as a catalyst. The amount of particles 13 can be reduced. In addition, such a configuration can be easily produced by electrodeposition of the metal nanoparticles 13 on the surface of the electron conductor 10.

  In the present embodiment, an example in which the metal nanoparticles 13 are not contained inside the conductive porous body 12 has been described, but the metal nanoparticles 13 may be contained inside the conductive porous body 12. Even if the metal nanoparticles 13 are contained in the inside of the conductive porous body 12, the amount of the metal nanoparticles 13 in contact with the electron conductor 10 and the ion conductive solid electrolyte 11 on the surface of the conductive porous body 12 is If the amount is larger than the amount of the metal nanoparticles 13 contained in the inside of the conductive porous body 12, it is possible to provide an electrode having a high conversion efficiency of the reaction gas into ions even with a small amount of catalyst.

  In the present embodiment, the reaction gas has been described using hydrogen and oxygen as examples, but the reaction gas may be methane, propane, hydrocarbons such as ethylene, alcohols such as methanol, carbon dioxide, air and water quality, in addition to hydrogen and oxygen. Contaminated organic matter can be mentioned. Electrochemical devices to which they can be applied include fuel cells and electrochemical sensors equipped with hydrocarbon and methanol oxidation electrodes, artificial photosynthetic devices equipped with carbon dioxide reduction electrodes and carbon dioxide sensors, and oxidation and reduction of organic substances that pollute the air and water. Applications other than fuel cells and hydrogen sensors are also conceivable, such as contaminated organic matter removal devices that decompose.

  Although an example is shown below, the present invention is not limited to these.

Example 1
A sulfonated polyimide was dissolved in diethylmethylammonium trifluoromethanesulfonate to prepare an ionic liquid electrolyte membrane adjusted to a thickness of 25 μm.

  Polytetrafluoroethylene dispersion (manufactured by Daikin Industries, Ltd.) and acetylene black (manufactured by Electrochemical Corporation, particle size 40 to 50 nm) are mixed so that acetylene black: PTFE = 7: 3 (weight ratio), 10 g of the mixture was mixed with water (100 mL) and Triton (registered trademark) X-100 (manufactured by Aldrich chemical) (1 g), and further mixed with 5 g of an electrolyte in which sulfonated polyimide was dissolved in diethylmethylammonium trifluoromethanesulfonate. . The mixture was then stirred, mixed, dried and milled. Sodium chloride powder containing 80% by weight or more of sodium chloride with a particle diameter of 1 μm or more is mixed with this pulverized material at PTFE-supported carbon black: NaCl powder = 1: 4 (weight ratio), and naphtha is 6 mL per 1 g of PTFE-supported carbon Added and mixed. Then, the mixture was formed into a 0.3 mm thick sheet, dried at 250 ° C. for 1 hour, and sintered at 350 ° C. for 5 minutes. The sintered sheet was immersed in a sufficient amount of a mixed solvent of 80% by volume of ethyl alcohol / 20% by volume of distilled water to elute sodium chloride in the sheet and dried to obtain a conductive porous electrode.

  Tetraammineplatinum (II) chloride hydrate (2.3 mmol) and silver trifluoromethanesulfonate (4.6 mmol) were dissolved in 50 mL of water and stirred. The white precipitate of silver chloride was filtered off and the filtrate was dried by heating to 130 ° C. under reduced pressure for 24 hours to obtain platinum trifluoromethanesulfonate. After 0.01 M of this platinum trifluoromethanesulfonate was dissolved in diethylmethylammonium trifluoromethanesulfonate, this solution was uniformly applied to the conductive porous electrode. A conductive porous electrode, a carbon sheet as a counter electrode, and diethyl methyl ammonium trifluoromethane sulfonate as an electrolyte were used to constitute an electrolytic cell. Platinum nanoparticles were deposited on the surface of the conductive porous electrode by applying a voltage so that the conductive porous electrode had a negative potential with respect to the counter electrode. Thereafter, the electrolytic solution was removed to prepare a conductive porous electrode with metal nanoparticles. The amount of platinum nanoparticles deposited was 1.4 g as determined from the amount of electrodeposition electricity.

(Example 2)
A sulfonated polyimide was dissolved in 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide to prepare an ionic liquid electrolyte membrane adjusted to a thickness of 25 μm.

  A conductive porous electrode with metal nanoparticles was prepared in the same manner as in Example 1, except that 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide was used instead of diethylmethylammonium trifluoromethanesulfonate. Made. The deposition amount of platinum nanoparticles determined from the amount of electrodeposition was 1.3 g.

(Comparative example 1)
A 25 μm thick Nafion® was used for the electrolyte membrane.

  Polytetrafluoroethylene dispersion (manufactured by Daikin Industries, Ltd.) and acetylene black (manufactured by Electrochemical Corporation, particle size 40 to 50 nm) are mixed so that acetylene black: PTFE = 7: 3 (weight ratio), A mixture of 10 g of water (100 mL) and Triton (registered trademark) X-100 (manufactured by Aldrich Chemical Co., Ltd.) (1 g) is further mixed with Nafion (the electrolyte content is 10% by mass and the water content is 90% by mass) 5 g of a Dupont DE-1020 (trademark) dispersion and a platinum-supported electrocatalyst (platinum content: 46% by mass) were added and mixed. The mixture was then stirred, mixed, dried and milled. Sodium chloride powder containing 80% by weight or more of sodium chloride with a particle diameter of 1 μm or more is mixed with this pulverized material at PTFE-supported carbon black: NaCl powder = 1: 4 (weight ratio), and naphtha is 6 mL per 1 g of PTFE-supported carbon Added and mixed. Then, the mixture was formed into a 0.3 mm thick sheet, dried at 250 ° C. for 1 hour, and sintered at 350 ° C. for 5 minutes. The sintered sheet was immersed in a sufficient amount of a mixed solvent of 80% by volume of ethyl alcohol / 20% by volume of distilled water to elute sodium chloride in the sheet and dried to obtain a conductive porous electrode. The platinum content of this conductive porous electrode is 5 g × 0.46 = 2.3 g.

(Comparative example 2)
A sulfonated polyimide was dissolved in diethylmethylammonium trifluoromethanesulfonate to prepare an ionic liquid electrolyte membrane adjusted to a thickness of 25 μm.

  Polytetrafluoroethylene dispersion (manufactured by Daikin Industries, Ltd.) and acetylene black (manufactured by Electrochemical Corporation, particle size 40 to 50 nm) are mixed so that acetylene black: PTFE = 7: 3 (weight ratio), Mix 10 g of the mixture with water (100 mL) and Triton (registered trademark) X-100 (manufactured by Aldrich Chemical Co., Ltd.) (1 g), and further add 5 g of an electrolyte in which sulfonated polyimide is dissolved in diethylmethylammonium trifluoromethanesulfonate, platinum 5 g of the supported electrode catalyst (platinum content: 46% by mass) were mixed. The mixture was then stirred, mixed, dried and milled. Sodium chloride powder containing 80% by weight or more of sodium chloride with a particle diameter of 1 μm or more is mixed with this pulverized material at PTFE-supported carbon black: NaCl powder = 1: 4 (weight ratio), and naphtha is 6 mL per 1 g of PTFE-supported carbon Added and mixed. Then, the mixture was formed into a 0.3 mm thick sheet, dried at 250 ° C. for 1 hour, and sintered at 350 ° C. for 5 minutes. The sintered sheet was immersed in a sufficient amount of a mixed solvent of 80% by volume of ethyl alcohol / 20% by volume of distilled water to elute sodium chloride in the sheet and dried to prepare a conductive porous electrode. The platinum content of this conductive porous electrode is 5 g × 0.46 = 2.3 g.

  The electrodes and electrolyte membranes described in Examples 1 and 2 and Comparative Examples 1 and 2 were used in a fuel cell. The fuel cells of Examples 1 and 2 and Comparative Example 2 could generate power even at 120 ° C., but the fuel cells of Comparative Example 1 could not generate power.

The characteristics of the fuel cell using the electrode and the electrolyte membrane described in Examples 1 and 2 and Comparative Example 2 at 120 ° C. show that the current density at the cell voltage of 0.5 V is 131, 128 and 83 mA / cm in order It was ² .

  As described above, the fuel cell using the porous electrode with metal nanoparticles of the present invention is excellent in the conversion efficiency of the reaction gas into ions even if the amount of catalyst is smaller than that of the conventional porous electrode with catalyst, hydrogen The conversion efficiency to gas protons is good. Furthermore, a fuel cell using the metal nanoparticle-attached porous electrode of the present invention and an ionic liquid electrolyte membrane which is an ion conductive solid electrolyte has excellent characteristics even at an operating temperature of 100 ° C. or higher.

  Further, using the electrodes and the electrolyte membranes described in Examples 1 and 2 and Comparative Examples 1 and 2, an electrochemical hydrogen sensor was produced.

The current density detected by the electrochemical hydrogen sensor using the electrode and the electrolyte membrane described in Examples 1 and 2 and Comparative Examples 1 and 2 is 100 mL / min of air containing 500 ppm of hydrogen concentration at 25 ° C. and 70% RH. In the order, it was 0.06, 0.05, 0.01, and 0.02 μA / cm ² .

Detection was continued with the electrochemical hydrogen sensor using the electrode and the electrolyte membrane described in Examples 1 and 2 and Comparative Examples 1 and 2 against 100 mL / min ^{1 of} air containing 500 ppm of hydrogen concentration at 25 ° C. and 0% RH. By the way, although the sensor of Comparative Example 1 had a detection current density reduced to 0.00 μA / cm ² at 28 h from the detection start, the detection current density after 28 h from the detection start of the sensors of Example 1, 2 and Comparative Example 2 is In the order, it was 0.06, 0.05, and 0.02 μA / cm ² .

  As described above, the hydrogen sensor using the metal nanoparticle-attached porous electrode of the present invention is excellent in the conversion efficiency of the reaction gas into ions even if the amount of catalyst is smaller than that of the conventional catalyst-attached porous electrode. The detection sensitivity of is good. Furthermore, the hydrogen sensor using the metal nanoparticle-attached porous electrode of the present invention and the ionic liquid electrolyte membrane which is an ion conductive solid electrolyte has excellent characteristics even when operated continuously for a long time.

  Table 1 summarizes the fuel cell and the hydrogen sensor using the electrode and the electrolyte membrane described in Examples and Comparative Examples, and Examples and Comparative Examples.

1: Fuel cell 2: Ion conductive solid electrolyte membrane 3: Electrode with metal nanoparticles 4: Gas diffusion electrode 5: Gas flow path 6: Separator 7: Hydrogen sensor 8: Reference electrode 9: External circuit 10: Electron conductor 11 : Ion conductive solid electrolyte
12: conductive porous body 13: metal nanoparticle 16: three-phase interface

Claims (4)

A conductive porous body having an electron conductor and an ion conductive solid electrolyte, and metal nanoparticles held by the conductive porous body,
The amount of the metal nanoparticles in contact with the electron conductor and the ion conductive solid electrolyte on the surface of the conductive porous body is larger than the amount of the metal nanoparticles contained in the inside of the conductive porous body An electrode characterized by   The electrode according to claim 1, wherein the metal nanoparticles are held on the exposed surface of the electron conductor on the surface of the conductive porous body.   The electrode according to claim 1, wherein the ion conductive solid electrolyte is obtained by solidifying or polymerizing an ionic liquid.   An electrochemical device using an ion conductive solid electrolyte and the electrode according to any one of claims 1 to 3.

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