JP2013049888A - Electrode and water electrolysis apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water electrolysis apparatus that suppresses a transient response in a water electrolysis reaction, and that is also capable of dealing with a fluctuating electrical power input by exercising simple control.SOLUTION: In the water electrolysis apparatus 101, a cathode 103 for a double-layer capacitor and a hydrogen generating pole 104 for water electrolysis are each installed opposite to one anode 102 to be connected in parallel, and thereby the water electrolysis and the double-layer capacitor are integrated. The one anode 102 is used as an oxygen generating pole in the water electrolysis reaction in common with an anode for the double-layer capacitor. Accordingly, the apparatus suppresses the transient response in the water electrolysis reaction and can deal with the fluctuating electrical power input by exercising the simple control. As a result, the deterioration is suppressed and the cost is reduced, in the water electrolysis apparatus.

Description

  The present invention relates to a water electrolysis apparatus including a double layer capacitor.

  Hydrogen is attracting attention as an energy source for the next generation in place of fossil fuels, in the face of concerns about the negative impact on the environment and the depletion of energy sources due to the massive consumption of fossil fuels. Since hydrogen only discharges water after use, it is considered to be a new energy source that has little environmental impact and is clean and free of resource problems that can be produced anywhere by electrolysis of water.

  Regarding the production of hydrogen, there are many methods such as steam reforming of hydrocarbons, photocatalytic decomposition of water, microbial reaction, and electrolysis of water. In particular, water electrolysis is attracting attention as a truly clean energy production method because it uses carbon derived from renewable energy such as solar power generation and wind power generation to reduce carbon dioxide emissions during production to an extremely low level. Yes.

  Since the power output from renewable energy fluctuates, if it is directly connected to a water electrolyzer that has been generally used at a constant power, such as grid power, it is a partition wall due to electrode breakage or pressure increase due to current concentration It is expected that various problems such as cell destruction will occur. For example, it is possible to make electric power constant by installing a power storage facility between a renewable energy generator and a water electrolyzer as in Patent Document 1 or the like. However, problems such as increased equipment costs and complicated control methods remain. Therefore, there is a need for a device that can be used for renewable power plants independently for use with variable power.

JP 2003-257443 A

  In general, the electrolysis reaction of water is a reaction accompanied by substance diffusion such as diffusion of water molecules and diffusion of generated gas bubbles, and it is difficult to cope with electric power that varies in milliseconds. In particular, when an abrupt increase in power occurs, the oxygen generation reaction on the oxygen generation electrode side cannot follow, and the voltage rises more than expected, and problems such as dissolution and destruction on the oxygen generation electrode side are expected.

  In addition, since the oxygen generation electrode in the water electrolysis apparatus is formed of a metal oxide having a large double layer capacity, it is necessary to charge the double layer capacity of the oxygen generation electrode before the water electrolysis reaction proceeds. If there is a difference between the transient response due to this charging and the fluctuation characteristics of the input power, a load is applied to the control device, the generator, and the electrolyzer, causing a failure.

  In order to level the power fluctuation, when a double layer capacitor or a Li storage battery having excellent responsiveness is separately installed, the installation cost increases. Moreover, since it is necessary to control a water electrolysis apparatus and a storage battery separately, a control method becomes difficult.

  In view of the above problems, an object of the present invention is to provide a water electrolysis apparatus that can suppress transient responsiveness in a water electrolysis reaction and can respond to input of variable power by simple control.

  The present invention relates to a water electrolysis apparatus for electrolyzing water to obtain hydrogen and oxygen, a hydrogen generating electrode for generating hydrogen by electrolyzing water, an oxygen generating electrode for generating oxygen by electrolyzing water, A cathode for a double layer capacitor installed corresponding to the generation electrode, the hydrogen generation electrode, the oxygen generation electrode, the cathode for the double layer capacitor, and an electrolytic cell containing an electrolytic solution, the oxygen generation A double-layer capacitor is formed by using the electrode as an anode for a double-layer capacitor, the oxygen-generating electrode and the cathode for the double-layer capacitor, and the water electrolysis cell including the hydrogen-generating electrode and the oxygen-generating electrode; It is characterized by a water electrolysis apparatus having a configuration in which multi-layer capacitors are electrically connected in parallel.

  Double-layer capacitor cathode and water electrolysis hydrogen generation electrode are placed facing each other on a single anode and connected in parallel to integrate a fast-response double-layer capacitor. A water electrolysis apparatus can be provided. At this time, the anode functions as an oxygen generating electrode for water electrolysis and an anode for a double layer capacitor.

  According to the present invention, it is possible to reduce the installation cost and the electrode cost by integrating the double layer capacitor and the water electrolysis apparatus. Also, by sharing the anode, the transient response in the water electrolysis reaction is suppressed, and it becomes possible to respond to the input of variable power by simple control, so that the deterioration of the water electrolysis apparatus can be suppressed and the cost can be reduced.

The electrode installation block diagram and the connection schematic diagram of the water electrolysis apparatus of this invention. The structure cross-sectional schematic diagram of the electrode which carry | supported the metal oxide of this invention. The figure which shows the optical microscope image of the electrode surface which carry | supported the amorphous body oxide of Mn and Ir in this invention. The figure which shows the XRD measurement result of the electrode surface which carry | supported the amorphous body oxide of Mn and Ir in this invention.

  The present invention is a water electrolysis apparatus, in which a cathode for a double layer capacitor and a hydrogen generation electrode for water electrolysis are respectively installed facing each other with respect to a single anode and connected in parallel, A double layer capacitor is integrated.

  The water electrolysis apparatus of the present invention includes a hydrogen generating electrode, an oxygen generating electrode, a cathode for a double layer capacitor installed corresponding to the oxygen generating electrode, the hydrogen generating electrode, the oxygen generating electrode, and the double layer capacitor. A cathode for use, and an electrolytic cell containing an electrolytic solution, using the oxygen generation electrode as an anode for a double layer capacitor, forming a double layer capacitor with the oxygen generation electrode and the cathode for the double layer capacitor, A water electrolysis cell composed of the hydrogen generation electrode and the oxygen generation electrode and the double layer capacitor are electrically connected in parallel.

  It is preferable to use a metal oxide for the oxygen generating electrode and the electrode of the double layer capacitor anode. A double layer capacitor using electrodes made of metal oxide has a quick response and a large capacity, and is suitable for cooperation with a renewable energy generator such as a wind power generator whose output power fluctuates rapidly in a short time. .

  In general, in a circuit in which a water electrolyzer and a double layer capacitor are connected in parallel, a total of four electrodes, each of an anode and a cathode, are originally required. On the other hand, a metal oxide is used at the anode of the water electrolysis reaction, that is, the oxygen generating electrode. In addition to the double layer capacity in which charges are stored at the interface with the electrolyte, metal oxides have a pseudo capacity due to a change in valence, such as a change to hydroxide, and can store a large capacity charge. Therefore, it is possible to use a metal oxide as an electrode for a capacitor. Therefore, in the present invention, the oxygen generation electrode of the water electrolysis reaction and the anode of the double layer capacitor are made the same electrode, thereby realizing the water electrolysis reaction and the double layer capacitor with three electrodes, and further, in the same tank It was possible to integrate it into

  Further, in a general water electrolysis reaction, when a voltage is applied to an oxygen generation electrode having a capacitor capacity, oxygen generation does not occur until charge charge is completed. In the present invention, since the oxygen generation electrode is used as the anode of the double layer capacitor, charge can be charged even in a voltage region where no water electrolysis reaction occurs, so that the water electrolysis reaction starts smoothly and rapidly. Responsiveness to voltage fluctuation can be improved.

  Furthermore, in the water electrolysis apparatus integrated with the double layer capacitor according to the present invention, when the electrolytic cells are connected in series, the double layer capacitor absorbs the voltage difference between the cells, so that the electrode for water electrolysis is excessive. The effect which suppresses deterioration is anticipated without a heavy load. In a general water electrolyzer, when the electrolytic cells are connected in series, if the electrode performance of each cell is slightly different, a high voltage is applied to the electrolytic cell having the poorest performance and the electrodes are deteriorated. Therefore, according to the present invention, there is an effect that it is easy to construct a large-sized apparatus in which electrolytic cells are connected.

  In the present invention, the electrode for water electrolysis and the electrode of the double layer capacitor integrated in the same bathtub are connected in a parallel circuit. As a result, instantaneous power fluctuations flow through the responsive double layer capacitor electrode, so that it is possible to connect to a power generator whose output fluctuates frequently in a short time like a wind power generator.

  The connection between the electrode for water electrolysis and the electrode for the double layer capacitor may be switched mechanically with a switch or the like, but can also be switched automatically by utilizing the characteristics of the electrode material. The present invention is characterized in that the hydrogen generation overvoltage of the electrode used for the cathode of the double layer capacitor is 50 mV to 500 mV higher than the hydrogen generation overvoltage of the hydrogen generation electrode in water electrolysis. As a result, the charge / discharge reaction of the double layer capacitor proceeds in a voltage range lower than 1.48 V where the water electrolysis reaction does not proceed. However, when the voltage rises, the hydrogen generation reaction mainly occurs at the hydrogen generation electrode with a low overvoltage, and automatically The reaction switches to a water electrolysis reaction. If the hydrogen generation reaction proceeds at the cathode of the double layer capacitor installed on the oxygen cell side, the oxygen generation reaction will be adversely affected, so the higher the hydrogen generation overvoltage at the cathode of the double layer capacitor, the better. In order to proceed with priority, it is sufficient if there is a difference in overvoltage, a difference in overvoltage of about 50 mV to 500 mV is sufficient, and a difference in the range of 100 mV to 300 mV is even better.

  The oxygen generating electrode and the cathode for the double layer capacitor have a structure in which a metal oxide is supported on the substrate surface. Examples of the metal oxide to be supported include metals such as Ni, Ru, Ir, Ti, Sn, Mo, Ta, Nb, V, Fe, and Mn, or oxides of alloys made of any of these metals. As the oxygen generation electrode used for the oxygen generation reaction, it is preferable to use Ni, Ru, Ir, Fe, or Mn having high catalytic activity. Further, Ru, Ir, Sn, Mo, V, and Mn having a large pseudo capacitance are preferable as electrodes used for the double layer capacitor. Since the anode installed opposite to the hydrogen generation electrode performs the oxygen generation reaction and the double layer capacitor charge / discharge reaction on the same electrode, it is preferable to use Ru, Ir, or Mn suitable for both reactions. However, since the precious metals Ru and Ir are expensive, it is preferable to add Ru and Ir mainly with Mn. Any of Ru, Ir, Sn, Mo, V, and Mn may be used as the cathode for the double layer capacitor used only for the charge / discharge reaction of the double layer capacitor.

  The form of the metal oxide to be supported is not particularly limited, but is preferably amorphous. Since the crystal structure has problems such as different reactivity and different solubility depending on a specific crystal plane, the metal oxide is preferably amorphous in order to form a uniform and corrosion-resistant electrode.

  The substrate of the electrodes constituting the oxygen generating electrode and the cathode for the double layer capacitor may be any material having conductivity, but it is preferable to use Ti having excellent corrosion resistance. In order to enhance the electrode performance, Ti preferably has a high specific surface area. For this reason, it is good to use a porous body of Ti, a net | network, a nonwoven fabric, a punching metal, an expanded metal etc. as a board | substrate. In particular, for the electrode used for the oxygen generation reaction, it is preferable to use a net, a punching metal, or an expanded metal, from which generated bubbles can be easily detached.

  The electrode manufacturing method is not particularly limited as long as the above configuration can be realized. For example, it can be supported by wet methods such as cathode deposition and anode deposition in an aqueous solution containing Mn, Ir, and Ru salts, and also by a dry method in which Mn, Ir, and Ru salts are dissolved in a solution and coated and fired. It can be supported.

  The hydrogen generation electrode has a role of promoting a reaction of reducing water to generate hydrogen. The hydrogen generation electrode preferably has a high specific surface area, more preferably a porous body, a net-like shape, or a non-woven fabric. Further, a nanostructure or the like is preferably formed on the surface. The hydrogen generation electrode preferably has a hydrogen generation overvoltage lower by 50 mV to 500 mV than the cathode of the capacitor electrode. As such an electrode material, it is preferable to use a platinum group such as Pt, Rh, and Ir, which has a smaller hydrogen generation overvoltage than the oxides of Ir, Mn, and Ru. In addition, since the platinum group is expensive, less expensive Ni may be used, or an alloy with the platinum group may be used.

  In the water electrolysis apparatus of the present invention, members other than the electrodes are not particularly defined, but the electrolyte solution preferably has low resistance and low corrosivity. An aqueous solution of sodium hydroxide or potassium hydroxide used in a general alkaline water electrolysis apparatus may be used. The material of the partition provided between the electrodes is not particularly defined, but a highly stable resin that does not dissolve in an aqueous solution is preferable. Examples include polyimide and polyethylene. In the case of a resin, it needs to be porous and sponge-like so that ions can move inside. Moreover, you may utilize the ion conductive resin which has the characteristic of an electrolyte and a partition. In particular, when a proton conductive resin is used, the oxygen generation electrode side does not require an aqueous solution and the hydrogen generation electrode side does not require water, and only pure hydrogen is used, so that gas-liquid separation is not required, and power generation is facilitated. In the water electrolysis apparatus of the present invention, a partition wall is provided between the electrodes for the hydrogen generation electrode and the oxygen generation electrode and also between the electrodes for the capacitor, and the same material can be used.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to specific examples.

  Example 1 is an example of the electrode of the present invention.

  FIG. 1 is an example of an electrode installation configuration diagram and a connection schematic diagram of a water electrolysis apparatus of the present invention.

  The water electrolysis apparatus 101 includes an oxygen generation electrode for water electrolysis and an anode 102 for double layer capacitor, a cathode 103 for double layer capacitor, a hydrogen generation electrode 104 for water electrolysis, an electrolytic solution 105, a partition wall 106, an electrolytic cell 109, and a wiring connection portion. 110. The oxygen generation electrode for water electrolysis and the anode 102 for double layer capacitor, the cathode 103 for double layer capacitor, and the hydrogen generation electrode 104 for water electrolysis are placed facing each other, and the cathode 103 for double layer capacitor and hydrogen for water electrolysis Between the generation electrode 104, the oxygen generation electrode for water electrolysis and the anode 102 for a double layer capacitor are located. The electrode for water electrolysis and the electrode for the double layer capacitor are connected in parallel, the positive electrode of the external power source 111 is the oxygen generation electrode for double electrolysis and the anode 102 for the double layer capacitor, and the negative electrode is for the double layer capacitor. The cathode 103 and the hydrogen electrolysis hydrogen generation electrode 104 are connected to each other. When a voltage necessary for the electrolysis of water is applied from the external power source 111, the hydrogen gas 107 is supplied from the hydrogen electrolysis hydrogen generation electrode 104, and the oxygen gas 108 is supplied from the water electrolysis oxygen generation electrode / double layer capacitor anode 102. Will occur.

  The oxygen generating electrode for water electrolysis and the anode 102 for double layer capacitor and the cathode 103 for double layer capacitor are electrodes having a metal oxide supported on a substrate. FIG. 2 shows a schematic cross-sectional view of the structure of an electrode having a metal oxide supported on a substrate. The electrode 201 includes a metal oxide 202 and a substrate 203. The metal oxide 202 exists on the entire surface of the substrate 203, and the shape may be any of fine particles, thin films, porous bodies, rods, and disks. The metal oxide is an amorphous material. The substrate 203 has a through-hole 204 that serves as a passage for gas generated in the water electrolysis reaction.

  As an example of the electrode 201, FIG. 3 shows an optical microscope image of the surface of the actually produced electrode. The Ti substrate was fabricated by etching in a 10 wt% oxalic acid aqueous solution at 90 ° C. for 10 minutes. Next, after immersing the Ti substrate in a butanol solution containing Mn, firing it at 500 ° C. to support the oxide of Mn, and further immersing and firing it in a butanol solution containing Ir to produce the electrode shown in FIG. did. A mixed oxide of Mn and Ir deposited in a rod shape can be confirmed on the surface. FIG. 4 shows the XRD measurement result of the electrode surface shown in FIG. In addition to metal Ti and Ti oxide, a halo pattern derived from an amorphous material and a broad peak can be confirmed, indicating that the mixed oxide of Mn and Ir supported on the surface forms an amorphous material. Yes.

  In Example 1, an amorphous body of a mixed oxide of Mn and Ir was selected as the electrode on the oxygen cell side. The ratio of Mn to Ir was 8: 1. An expanded metal of 0.2 mm thickness of Ti was used for the substrate. A Ni wire mesh was used on the hydrogen generation electrode side. The electrolyte used was a 30 wt% potassium hydroxide aqueous solution, and a polyethylene nonwoven fabric having a thickness of 0.5 mm was used for the partition walls.

The charge / discharge capacity of the double-layer capacitor on the oxygen cell side was 824 mC per 1 cm ² of electrode. The water electrolysis ability was measured by the voltage when 1 A was energized. In the configuration of Example 1, the electrolytic voltage was 1.8V.

In Example 2, a 0.15 mm diameter Ti wire mesh was used for the substrate. Other conditions were the same as in Example 1. At this time, the charge / discharge capacity of the double layer capacitor was 780 mC per 1 cm ² of electrode. The electrolysis voltage in water electrolysis was 1.8V.

In Example 3, an amorphous body of a mixed oxide of Mn and Ru was selected as the electrode on the oxygen cell side. The ratio of Mn to Ru was 6: 1. Other conditions were the same as in Example 1. At this time, the charge / discharge capacity of the double layer capacitor was 920 mC per 1 cm ² of electrode. The electrolysis voltage in water electrolysis was 1.7V.

In Example 4, an electrode carrying Mn and Ir oxides was used as an electrode on the oxygen cell side. The oxide has a crystal structure, and was mainly formed from Mn ₃ O ₄ and IrO ₂ . Other conditions were the same as in Example 1. At this time, the charge / discharge capacity of the double layer capacitor was 620 mC per 1 cm ² of electrode. The electrolysis voltage in water electrolysis was 2.4V.

In Example 5, an electrode carrying an Ir oxide was used as the electrode on the oxygen cell side. The oxide has a crystal structure, it has been formed predominantly from IrO _2. Other conditions were the same as in Example 1. At this time, the charge / discharge capacity of the double layer capacitor was 480 mC per 1 cm ² of electrode. The electrolysis voltage in water electrolysis was 2.2V.

In Example 6, a Ni wire mesh equivalent to the hydrogen generation electrode side was used as the electrode on the oxygen cell side. Other conditions were the same as in Example 1. At this time, the charge / discharge capacity of the double layer capacitor was 90 mC per 1 cm ² of electrode. The electrolysis voltage in water electrolysis was 2.0V.

DESCRIPTION OF SYMBOLS 101 Water electrolysis apparatus 102 by this invention Oxygen generating electrode for water electrolysis and anode for double layer capacitor 103 Cathode for double layer capacitor 104 Hydrogen generating electrode for water electrolysis 105 Electrolytic solution 106 Partition 107 Hydrogen gas 108 Oxygen gas 109 Electrolysis tank 110 Wiring connection portion 111 External power source 201 Electrode 202 Metal oxide 203 Substrate 204 Through hole

Claims (9)

In water electrolysis equipment that electrolyzes water to obtain hydrogen and oxygen,
A hydrogen generating electrode that generates hydrogen by electrolysis of water;
An oxygen generating electrode that generates oxygen by electrolysis of water;
A cathode for a double layer capacitor installed corresponding to the oxygen generating electrode;
The hydrogen generating electrode, the oxygen generating electrode, the cathode for the double layer capacitor, and an electrolytic cell containing an electrolytic solution,
Using the oxygen generating electrode as a double layer capacitor anode, the oxygen generating electrode and the double layer capacitor cathode constitute a double layer capacitor,
A water electrolysis apparatus comprising a structure in which a water electrolysis cell composed of the hydrogen generation electrode and the oxygen generation electrode and the double layer capacitor are electrically connected in parallel.   2. The water electrolysis apparatus according to claim 1, wherein the oxygen generating electrode and the double layer capacitor cathode have a structure in which a metal oxide is supported on a surface of a substrate.   The water electrolysis apparatus according to claim 2, wherein the metal oxide is amorphous.   2. The hydroelectric system according to claim 1, further comprising a partition wall between the hydrogen generation electrode and the oxygen generation electrode and between the oxygen generation electrode and the cathode for the double layer capacitor to prevent a short circuit between the electrodes. Disassembly equipment.   2. The water electrolysis apparatus according to claim 1, wherein the hydrogen generation overvoltage of the double layer capacitor cathode is 50 to 500 mV higher than the hydrogen generation overvoltage of the hydrogen generation electrode.   3. The water electrolysis apparatus according to claim 2, wherein the substrate is Ti, and the metal oxide is a combination of oxides of Mn, Ru, and Ir.   3. The water electrolysis apparatus according to claim 2, wherein the substrate constituting the oxygen generating electrode is Ti, and the metal oxide is an amorphous oxide of Mn and Ir.   3. The water electrolysis apparatus according to claim 2, wherein the substrate is Ti, and the shape of the substrate is any one of a net, a punch metal, an expanded metal, and a porous body.   The hydrogen generation electrode according to claim 1, the oxygen generation electrode, the cathode for the double layer capacitor, and a plurality of electrolytic cells for storing an electrolytic solution, which are electrically connected in series. Water electrolyzer.