JP2012052202A - Member for electrolysis cell and hydrogen production device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for an electrolysis cell capable of improving hydrogen production efficiency when used in a device producing hydrogen by electrolysis of organic compounds, and a hydrogen production device using the member for an electrolysis cell.SOLUTION: The member for an electrolysis cell in the device producing hydrogen by electrolysis of organic compounds includes porous current collection members 1 and 2 using porous bodies consisting of electrically-conductive metallic powder. The member for an electrolysis cell of the device producing hydrogen by electrolysis of organic compounds is constructed by combining the porous current collection members 1 and 2 using the porous power bodies consisting of the electrically-conductive metallic powder and a plate-shaped base material together. The hydrogen production device using the member for an electrolysis cell is also provided.

Description

  The present invention relates to an electrolytic cell member of an apparatus for producing hydrogen from electrolysis of an organic compound containing alcohols such as methanol, and a hydrogen production apparatus using the same.

  In recent years, as represented by fuel cells and the like, hydrogen is very important as a future clean energy source. For example, hydrogen production using electrolytic decomposition of organic compounds such as alcohols conventionally requires a high temperature environment. Compared to the reforming method, etc., hydrogen can be produced with less energy. Hydrogen production using electrolysis of organic compounds such as alcohols is known to use, for example, a hydrogen ion conductive solid polymer electrolyte membrane and operate at a temperature of 100 ° C. or lower or at a low temperature such as room temperature. .

  Moreover, the method of obtaining hydrogen from the electrolysis of organic compounds such as methanol (theoretical decomposition voltage 0.016 V), formic acid (theoretical decomposition voltage -0.251 V), formaldehyde (theoretical decomposition voltage -0.142 V) is the theoretical decomposition voltage. Therefore, hydrogen can be obtained with energy smaller than the electrolysis of water (theoretical decomposition voltage 1.23 V).

  For example, as disclosed in Japanese Patent Application Laid-Open No. 11-229167 (Patent Document 1), in a method for producing hydrogen from electrolysis of methanol, silver is applied to a titanium expanded mesh as a current collecting member in the embodiment. The thing using what surface-treated, such as plating, is disclosed. However, this method is based on a method different from the method using a porous body made of spherical metal powder.

In addition, as disclosed in Japanese Patent Application Laid-Open No. 2005-23412 (Patent Document 2), as a method for producing hydrogen from the electrolysis of methanol, a cation exchange resin is filled in the voids of an organic porous thin film. A fuel reformer is disclosed in which an electrolyte membrane is formed, and a reaction device is formed by forming an electrode catalyst layer of an anode and a cathode on both surfaces of the electrolyte membrane. However, this also does not touch the current collecting member, and is different from the method using a porous body made of spherical metal powder.
Japanese Patent Laid-Open No. 11-229167 JP-A-2005-23412

  As described above, hydrogen such as fuel cells is very important as a future clean energy source. For example, hydrogen production using electrolytic decomposition of organic compounds such as alcohols requires a high temperature environment. Compared to the conventional reforming method and the like, hydrogen can be produced with less energy. However, there are problems in the contact resistance in the electrolytic cell, the supply characteristics of alcohols such as methanol, the discharge characteristics of the generated gas and the generated hydrogen, and there is a demand for improving the efficiency of hydrogen production through these improvements.

In hydrogen production by electrolysis of organic compounds containing alcohols such as methanol, the electrons required for the reaction of the hydrogen generating electrode in the electrolytic cell are obtained through an external circuit from the decomposition reaction of the organic compound such as methanol at the counter electrode. Therefore, in order to improve the efficiency of hydrogen production, it is increasingly important to reduce the contact resistance between the current collecting member in the electrolysis cell and the catalyst electrode layer or the diffusion layer, and to increase the mobility of electrons. Further, excellent supply characteristics such as aqueous methanol solution and excellent discharge characteristics of generated CO ₂ and generated H ₂ are important for improving the efficiency of hydrogen production.

  In order to solve the problems as described above, the inventors have made extensive developments. As a result, in an apparatus for producing hydrogen from electrolysis of organic compounds containing alcohols such as methanol, the current collectors in the electrolytic cell The present invention also provides an electrolytic cell member capable of improving the efficiency of hydrogen production by using a porous body made of conductive spherical metal powder and a hydrogen production apparatus using the same.

The gist of the invention is that
(1) An electrolytic cell member for an electrolytic cell of an apparatus for producing hydrogen from electrolysis of an organic compound, comprising a porous current collecting member using a porous body made of conductive metal powder.
(2) In a member for an electrolytic cell of an apparatus for producing hydrogen from electrolysis of an organic compound, a porous current collecting member using a porous body made of conductive metal powder and a plate-like base material are combined. Electrolytic cell member characterized by the above.

(3) The electrolytic cell member described in (1) or (2) above, wherein metal powders are metal-bonded to each other.
(4) The electrolytic cell member described in (2) or (3) above, wherein the metal powder and the plate-like substrate are metal-bonded.
(5) The electrolytic cell member described in any one of (1) to (4) above, wherein the metal powder has a spherical shape.
(6) A hydrogen production apparatus using the electrolytic cell member described in any one of (1) to (4).

  As described above, since the current collecting member of the electrolytic cell according to the present invention is composed of a porous body in which spherical metal powders are three-dimensionally bonded, the catalyst electrode layer or diffusion layer having porosity or elasticity can be used. Excellent contact adhesion and large effective contact area enable contact resistance to be reduced, improving the efficiency of hydrogen production by increasing the mobility of electrons required for hydrogen production and increasing reaction efficiency And Therefore, surface treatment such as gold plating, silver plating, and carbon coating performed on the current collecting member for the purpose of reducing contact resistance can be made unnecessary.

  In addition, regarding the supply function of organic compounds such as methanol and the discharge function of products, in the present invention, a porous structure in which spherical metal powders are joined mainly by point contact is obtained, and a catalyst electrode layer and a diffusion layer are obtained. Since the porosity at the contact interface with the surface is large, for example, 80% or more, etc., and the connecting pores inside the porous body surrounded by the spheres can be sufficiently secured, supply characteristics of organic compounds such as methanol, generated gas In addition, it has excellent discharge characteristics of generated hydrogen, and exhibits extremely excellent effects such as improving the efficiency of hydrogen production.

Hereinafter, the present invention will be described in detail.
Examples of the organic compound according to the present invention include methanol, ethanol, formaldehyde, formic acid and the like. In addition, it is desirable to use a spherical powder for the conductive metal powder. However, the spherical shape of the spherical metal powder does not mean a perfect sphere, and it naturally occurs by the action of surface tension and the like when solidifying from a molten state. The resulting sphere. Further, if a similar spherical shape is obtained by machining or the like, it is also applicable.

  In addition, when powder molding is performed from a molten state, it includes those in which fine metal powder or flat micro metal powder is bonded to the main spherical metal powder, depending on the intended use. It also has an effect of improving the adhesion between the structure and other members.

  The above atomizing method is suitable for the production of the spherical metal powder. Especially when the spherical metal powder produced by the gas atomizing method is used, the metal powder has a structure in which the metal powders are mainly in point contact with each other. Can be secured, and excellent mass transfer of liquid and gas flowing through the pores can be maintained. Further, the adhesion is improved at the time of contact with other members, and the contact resistance can be reduced. Although the gas atomizing method has been described, the present invention is not necessarily limited to the gas atomizing method, and the present invention is not limited to this as long as the method can obtain a spherical shape or a similar shape to a sphere. Depending on the application, it is also possible to apply a conductive coating such as corrosion resistant coating, gold plating, carbon coating, water repellent treatment, hydrophobic treatment, new aqueous treatment, and the like.

  When forming a porous body made of metal powder, and when joining metal powder to a plate-shaped substrate, vacuum heat treatment, pressure sintering, current sintering, discharge plasma sintering, cold spray method, pressure welding, electrical conductivity Although a method using an adhesive is conceivable, it may be sufficient to satisfy necessary electrical conductivity, corrosion resistance, strength, and the like. The plate-like base material to be joined to the metal powder may be a graphite base material having conductivity or a metal base material, but is not particularly limited thereto.

  For metal powders and between metal powders and plate-like base materials, metal bonding is desirable for the purpose of reducing electrical resistance and ensuring the strength of the structure, but if the properties required for each application are satisfied, This is not the case. In addition, the plate-like base material is not limited to a flat plate, and a plate-like base material that is bent or pressed using a flat plate, a plate-like base material wound in a spiral shape, and a near It includes a substrate made of a powder molded product or the like formed into a net shape.

  When the porosity of the porous body portion obtained in the present invention is less than 20%, it may be difficult to obtain sufficient mass mobility of gas or liquid. On the other hand, if the porosity exceeds 70%, the strength of the structure may be insufficient. Therefore, the porosity is preferably about 20% to 70%, but this is not the case when the substance mobility and strength actually required for each application can be sufficiently satisfied. Note that the porosity in this case refers to the average volume ratio occupied by the pores in a certain volume of the porous body portion, calculation using microscopic observation of the cross section, measurement by mercury intrusion method, gas Measurement by an adsorption method or the like is possible.

  The size of each hole can be controlled by the particle size of the spherical metal powder to be used. Depending on the application, the size of the hole may be different depending on the position in the porous structure. Specifically, there are those in which the size of the holes is divided into two stages depending on the position, or those in which the pores are distributed in order. The powder particle size to be used can be properly selected depending on the required properties. For example, for metal powders manufactured with gas atomized powder, a size of 1 μm to 1000 μm can be considered, but depending on the application, for example, several μm to 20 μm. , 20 μm to 70 μm, 100 μm to 200 μm, 200 to 300 μm, 300 to 500 μm, etc., and a powder particle size suitable for each application is applied.

  Various chemical components of the metal powder can be selected according to required corrosion resistance, oxidation resistance, thermal expansion characteristics, thermal conductivity, electrical conductivity, and the like. For example, stainless steel, Ni-base corrosion-resistant superalloy, Ni—Cu-based corrosion-resistant alloy, oxidation-resistant alloy, or the like is applied. Moreover, in order to control the thickness of a powder porous body part, press processing, rolling processing, grinding processing, polishing processing, etc. are applied.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view of a member for an electrolysis cell of an apparatus for producing hydrogen from electrolysis of methanol. As shown in this figure, between the porous current collector 1 on the hydrogen generation side made of a sintered porous body of spherical metal powder and the porous current collector 2 on the methanol aqueous solution supply side made of the sintered porous body of spherical metal powder. The solid polymer electrolyte membrane 3 is disposed on the left and right sides of the porous current collector 1 on the left and right hydrogen generating side and the porous current collector 2 on the methanol aqueous solution supply side, and the catalyst electrode layer 4 on the methanol aqueous solution supply side, hydrogen generation An electrolysis cell in which the catalyst electrode layer 5 on the side is arranged is formed.

  In this configuration, between the porous collector 1 on the hydrogen generation side and the catalyst electrode layer 5 on the hydrogen generation side, or between the porous current collector 2 on the methanol aqueous solution supply side and the catalyst electrode layer 4 on the methanol aqueous solution supply side. It is also possible to add a carbon diffusion layer (GDL). When the catalyst is directly supported on the porous body made of metal powder of the porous current collector 1 on the hydrogen production side and the porous current collector 2 on the methanol aqueous solution supply side, the catalyst electrode layer 4 on the methanol aqueous solution supply side and the hydrogen It is also possible to omit the catalyst electrode layer of the production-side catalyst electrode layer 5.

  Furthermore, when the porous body itself composed of the metal powder of the porous current collector 1 on the hydrogen generation side and the porous current collector 2 on the methanol aqueous solution supply side has a catalytic function depending on its chemical components, It is also possible to omit the catalyst electrode layers 4 and the catalyst electrode layers 5 on the hydrogen production side. FIG. 2 shows a plate-like substrate 6 made of metal or graphite disposed outside the porous current collector 1 on the hydrogen generation side and the porous current collector 2 on the methanol aqueous solution supply side shown in FIG. The member for electrolysis cells at the time of maintaining the function of the separator which isolate | separates methanol aqueous solution and produced | generated hydrogen by this is shown.

  Spherical metal powder of the porous current collector 1 on the hydrogen production side was produced by gas atomization method in mass%, and Fe-17Cr-12Ni-2Mo, Fe-25Cr-20Ni, Fe-25Cr-35Ni, Fe- 26Cr-1Mo, Ni-22Cr-9Mo-4Nb, Ni-16Cr-16Mo-5Fe-4W, Ni-30Cu, Fe-20Cr-1Al-1Si, Ti, or the like is used. Moreover, the powder particle diameter of the metal powder to be used is classified into, for example, 1 μm to 20 μm, 20 μm to 70 μm, 100 μm to 300 μm, 350 to 500 μm, and the like, and a powder particle size suitable for each application is applied.

  Spherical metal powder of the porous current collector 2 on the methanol aqueous solution supply side is produced by gas atomization method in mass%, and Fe-17Cr-12Ni-2Mo, Fe-25Cr-20Ni, Fe-25Cr-35Ni, Fe -26Cr-1Mo, Ni-22Cr-9Mo-4Nb, Ni-16Cr-16Mo-5Fe-4W, Ni-30Cu, Fe-20Cr-1Al-1Si, Ti or the like is used. Moreover, the powder particle diameter of the metal powder to be used is classified into, for example, 1 μm to 20 μm, 20 μm to 70 μm, 100 μm to 300 μm, 350 to 500 μm, and the like, and a powder particle size suitable for each application is applied.

  FIG. 3 is a diagram showing a relationship between current-voltage characteristics in the evaluation of hydrogen productivity. The electrolytic cell member having the porous current collector according to the present invention is prepared by subjecting a spherical SUS316L metal powder having a powder particle size of 350 to 500 μm produced by a gas atomization method to a vacuum heat treatment at 1200 ° C. for 90 minutes. A sintered porous body having a rate of 50% was obtained, and the obtained porous body was integrated with a plate-like base material made of SUS316L by vacuum sintering and used for evaluation.

In addition, the electrolytic cell member used in the comparative example has a current collecting function, and the flow path used for supplying methanol and discharging generated hydrogen has a groove shape, and the same SUS316L. The member for electrolytic cells made from was used. (The flow path portion and the current collecting portion have a groove shape that is also applied to power generation cells such as fuel cells, and are different from the members formed from the porous powder body of the present invention.

Hereinafter, the present invention will be specifically described with reference to examples.
In the electrolytic cell configuration of FIG. 2 described above, the test conditions are as follows: reaction area is 25 cm ² , electrolyte membrane is Nafion 117, methanol supply side catalyst is 1 mg / cm ² with Pt—Ru, and hydrogen generation side catalyst is 1 mg with Pt. / Cm ² , hydrogen production by measuring the current density obtained when the voltage is gradually increased at an electrolytic cell temperature of 25 ° C., a methanol aqueous solution concentration supply of 2 M, and a methanol aqueous solution supply amount of 10 cc / min. The efficiency of the system was examined. As a result, as shown in FIG. 3, in the case of the electrolytic cell using the metal powder porous body having both the current collecting function and the supply / discharge function of the present invention, compared with the groove-type member of the comparative example, the same potential condition is used. It can be seen that a large current value is obtained, and the effect of increasing the reaction efficiency of hydrogen generation is recognized. The factors are considered to be firstly reduction of contact resistance due to the characteristics of the spherical powder porous body, secondly improvement of supply characteristics of the methanol aqueous solution, and third improvement of discharge characteristics of hydrogen produced.

  As described above, since the current collecting member of the electrolysis cell according to the present invention is composed of a porous body in which spherical metal powders are three-dimensionally bonded, contact with the catalyst electrode layer or the diffusion layer having porosity or elasticity is possible. In addition to its excellent adhesion, the effective contact area also increases, so the contact resistance can be reduced, and the efficiency of hydrogen production can be improved by increasing the mobility of electrons required for hydrogen production and increasing the reaction efficiency. can do. In addition, since a porous structure in which spherical metal powders are joined mainly by point contact is obtained, the porosity at the contact interface with the catalyst electrode layer or the diffusion layer is large, and the connected pores surrounded by the spheres Therefore, it can be seen that there are excellent effects such as excellent supply characteristics of organic compounds such as methanol, discharge characteristics of generated gas and generated hydrogen, and improvement of hydrogen production efficiency.

It is the schematic of the member for electrolytic cells of the apparatus which manufactures hydrogen from the electrolysis of methanol. It is the schematic of the member for electrolytic cells (when a plate-shaped base material is also included) of the apparatus which manufactures hydrogen from the electrolysis of methanol. It is a figure which shows the relationship of the electric current-voltage characteristic in the evaluation test of hydrogen productivity.

DESCRIPTION OF SYMBOLS 1 Porous collector on the hydrogen production side 2 Porous current collector on the methanol aqueous solution supply side 3 Solid polymer electrolyte membrane 4 Catalyst electrode layer on the methanol aqueous solution supply side 5 Catalyst electrode layer on the hydrogen production side 6 Plate-like substrate


Patent applicant Sanyo Special Steel Co., Ltd. and 1 other
Attorney: Attorney Shiina

Claims (6)

An electrolytic cell member of an apparatus for producing hydrogen from electrolysis of an organic compound, comprising a porous current collecting member using a porous body made of conductive metal powder. A member for an electrolytic cell of an apparatus for producing hydrogen from electrolysis of an organic compound, comprising a porous current collecting member using a porous body made of conductive metal powder and a plate-like base material. Electrolytic cell member. 3. The electrolytic cell member according to claim 1, wherein the metal powders are metal-bonded to each other. 4. The electrolytic cell member according to claim 2, wherein the metal powder and the plate-like base material are metal-bonded. 5. The electrolytic cell member according to claim 1, wherein the metal powder has a spherical shape. The hydrogen production apparatus using the member for electrolytic cells described in any one of Claims 1-5.

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