Method of operating an electrolytic apparatus, method of operating an electrolytic system, and electrolytic system

Abstract

To provide a method of operating an electrolysis device of a long life.SOLUTION: A method of operating an electrolysis device using a membrane-electrode joint body comprising an anode including a porous catalyst layer including a noble metal porous body or sheet-shaped noble metal, a cathode, and an electrolyte membrane disposed between the anode and the cathode, carries out a first step of applying a low potential, to the anode, of 1.45 V or below with respect to the cathode, with the potential of the anode being set as a reference potential, and carries out a second step of applying a high potential, to the anode, of 2.0 V or above with respect to the cathode, with the potential of the anode being set as a reference potential.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a method for operating an electrolyzer, a method for operating an electrolysis system, and an electrolysis system.

Background Art

[0002] In recent years, electrochemical cells have been actively studied. Among electrochemical cells, for example, a polymer electrolyte membrane electrolysis cell (PEMEC) is expected to be used for hydrogen production in a large-scale energy storage system. In order to ensure sufficient durability and electrolysis characteristics, a noble metal catalyst such as a platinum (Pt) nanoparticle catalyst is generally used for the cathode of PEMEC, and a noble metal catalyst such as an iridium (Ir) nanoparticle catalyst is used for the anode. In addition, a method for obtaining hydrogen from ammonia has been studied.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=……]] The problem to be solved by the present invention is to provide a method for operating a long-life electrolyzer, a method for operating an electrolysis system, and an electrolysis system.

Means for Solving the Problems

[0005] The method for operating an electrolyzer according to the embodiment uses a membrane electrode assembly having an anode including a porous catalyst layer containing a noble metal porous body or a sheet-like noble metal, a cathode, and an electrolyte membrane provided between the anode and the cathode. Cathode with the potential of... as the reference potential 0.1V or higher The first step involves applying a low potential of 1.45V or less to the anode, Cathode Using the potential of as the reference potential 、2 0V or higher 3.0V or less The high potential 3 seconds or more and 60 seconds or less The second step involves applying a substance to the anode, The potential cycle, including this, is repeated 3 to 500 times. . [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic diagram of the electrolytic system according to the embodiment. [Figure 2] This is a micrograph of the catalyst unit of the embodiment. [Modes for carrying out the invention]

[0007] The embodiments will be described below with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0008] The physical properties described herein are those obtained at a temperature of 25°C and a pressure of 1 atom. The thickness of each component is the average value over the distance in the lamination direction.

[0009] (Embodiment) The operating method of the electrolytic apparatus of the embodiment uses a membrane electrode assembly having an anode containing a porous catalyst layer including a porous noble metal or a sheet-like noble metal, a cathode, and an electrolyte membrane provided between the anode and the cathode, and performs a first step of applying a low potential of 1.45V or less to the anode relative to the cathode, with the anode's potential as the reference potential, and a second step of applying a high potential of 2.0V or more to the anode relative to the cathode, with the anode's potential as the reference potential. The operating method of the electrolytic system of the embodiment comprises a membrane electrode assembly having an anode including a porous catalyst layer containing a porous noble metal or a sheet-like noble metal, a cathode, and an electrolyte membrane provided between the anode and the cathode, a power supply connected to the anode and the cathode, and a control circuit connected to the power supply, and performs a first step of applying a low potential of 1.45V or less to the anode using the power supply with respect to the cathode, with the anode's potential as the reference potential, and a second step of applying a high potential of 2.0V or more to the anode using the power supply with respect to the cathode, with the anode's potential as the reference potential. The electrolytic system of the embodiment includes a membrane electrode assembly having an anode including a plurality of first catalyst layers including at least one of a noble metal and an oxide of a noble metal and at least one of a non-noble metal and an oxide of a non-noble metal, a cathode, and an electrolyte membrane provided between the anode and the cathode, a power supply connected to the anode and the cathode, and a control circuit that controls the power supply to perform a first step of applying a low potential of 1.45V or less to the cathode with the potential of the anode as the reference potential, and a second step of applying a high potential of 2.0V or more to the cathode with the potential of the anode as the reference potential.

[0010] In the following embodiments, water electrolysis will be used as an example.

[0011] Furthermore, the operating method of the electrolytic apparatus in this embodiment can be used as an operating method for an ammonia electrolytic apparatus. The membrane electrode assembly 1 in this embodiment can be used as a membrane electrode assembly for an electrolytic apparatus for ammonia synthesis. The operating method of the electrolytic apparatus in this embodiment can be used as an operating method for an electrolytic apparatus used in electrolysis for ammonia synthesis, in which ultrapure water is supplied to the anode, the water is decomposed at the anode to produce protons and oxygen, the generated protons pass through the electrolyte membrane, and nitrogen supplied to the cathode combines with the protons and electrons to produce ammonia.

[0012] Furthermore, the operating method of the electrolytic apparatus in this embodiment can be used for operating an electrolytic apparatus that generates hydrogen by electrolyzing ammonia. The membrane electrode assembly 1 in this embodiment can be used for an apparatus that generates hydrogen by electrolyzing ammonia. The operating method of the electrolytic apparatus in this embodiment can be used for operating an electrolytic apparatus used for ammonia decomposition electrolysis, in which ammonia is supplied to the cathode, the ammonia is decomposed at the cathode to generate protons and nitrogen, the generated protons pass through the electrolyte membrane, and hydrogen is generated when the protons and electrons combine at the anode.

[0013] Figure 1 is a schematic diagram of an electrolytic system 100 according to an embodiment. The electrolytic system 100 comprises an electrolytic device 90 and a control circuit 3. The electrolytic device 90 includes a membrane electrode assembly 1, a power supply 2, a control circuit 3, a first supply device 4, and a second supply device 5.

[0014] The membrane electrode assembly 1 includes an anode 1A, a cathode 1B, and an electrolyte membrane 1C disposed between the anode 1A and the cathode 1B. Furthermore, the membrane electrode assembly 1 includes a first diffusion layer 1D as a diffusion layer for the anode 1A and a second diffusion layer 1E as a diffusion layer for the cathode 1B.

[0015] The anode 1A and the cathode 1B have a catalyst layer containing a noble metal element. The catalyst layer is provided on the first diffusion layer 1D or the second diffusion layer 1E. The catalyst layer of the anode is provided between the electrolyte membrane 1C and the first diffusion layer 1D. The catalyst layer of the cathode is provided between the electrolyte membrane 1C and the second diffusion layer 1E. The first diffusion layer 1D and the second diffusion layer 1E each also function as a substrate for the catalyst layer of the anode and the catalyst layer of the cathode.

[0016] The electrolyte membrane 1C is preferably an electrolyte membrane having proton conductivity. As the electrolyte membrane having proton conductivity, for example, a fluororesin having a sulfonic acid group (e.g., Nafion (manufactured by DuPont), Flemion (manufactured by Asahi Kasei), and Aciplex (manufactured by Asahi Glass), etc.), or an inorganic substance such as tungstic acid or phosphotungstic acid can be used.

[0017] For example, water is supplied to the anode 1A. In the anode 1A, protons, oxygen, and electrons are generated from water. In the cathode 1B, the protons and electrons generated in the anode 1A react to generate hydrogen. Either or both of the generated hydrogen and oxygen are utilized, for example, as fuel for a fuel cell.

[0018] As the first diffusion layer 1D, it is preferable to use a porous and highly conductive material. The first diffusion layer 1D is a porous member through which gas and liquid pass. The first diffusion layer 1D is, for example, carbon paper or a metal mesh. As the metal mesh, a porous substrate of valve metal is preferable. As the porous substrate of valve metal, a porous substrate containing one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony or a porous substrate of one metal selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony is preferable.

[0019] As the second diffusion layer 1E, it is preferable to use a porous and highly conductive material. The second diffusion layer 1E is a porous member through which gas and liquid pass. The second diffusion layer 1E is, for example, carbon paper or a metal mesh. As the metal mesh, a porous substrate of valve metal is preferable. As the porous substrate of valve metal, a porous substrate containing one or more metals selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony or a porous substrate of one metal selected from the group consisting of titanium, aluminum, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony is preferable.

[0020] From the viewpoint of high output, the catalyst layers included in the anode 1A and the cathode 1B are preferably catalyst layers containing a noble metal element. The catalyst layers included in the anode 1A and the cathode 1B preferably contain at least one metal from the group consisting of noble metal elements such as Pt, Ru, Rh, Os, Ir, Pd, and Au. More specifically, the catalyst layers included in the anode 1A and the cathode 1B preferably include a porous catalyst layer containing a noble metal porous body or sheet-like noble metal. Such a porous catalyst layer is a catalyst layer without a carrier, formed by a noble metal porous body or sheet-like noble metal, and having a structure. The porous catalyst layer is composed of units having a laminated structure in which a void layer exists between a porous structure or multilayer sheet-like noble metals. When using a noble metal catalyst, it is possible to maintain high characteristics and high durability of the membrane electrode assembly even with a small usage amount.

[0021] Figure 2(A) shows a scanning electron microscope (SEM) image of a porous catalyst layer containing a porous noble metal or sheet-like noble metal. Figures 2(B) and 2(C) show SEM images of the porous structure of the porous catalyst layer containing a porous noble metal or sheet-like noble metal. In the case of a laminated structure containing void layers, it is desirable for adjacent nanosheets to be partially integrated. Durability and robustness can be further improved by introducing a nanoceramic material layer into the laminated structure, or by placing a porous nanocarbon layer containing fibrous carbon between adjacent nanosheets or material layers. Such a porous catalyst layer containing a porous noble metal or sheet-like noble metal can be used as the catalyst layer contained in anode 1A and the catalyst layer contained in cathode 1B.

[0022] The porous catalyst layers included in the anode 1A and the cathode 1B contain, for example, any one of a metal, an alloy, and a metal oxide containing at least one metal selected from the group consisting of noble metal elements such as Pt, Ru, Rh, Os, Ir, Pd, and Au. It is preferable that this porous catalyst layer contains at least Pt, and more preferably contains at least one metal selected from the group consisting of noble metal elements such as Ru, Rh, Os, Ir, Pd, and Au and Pt. Such a catalyst material is excellent in catalytic activity, conductivity, and stability. The above-mentioned metals can also be used as oxides, and may be composite oxides or mixed oxides containing two or more metals. The optimal noble metal element can be appropriately selected according to the reaction in which the membrane electrode assembly is used. For example, when performing an oxygen reduction reaction as the cathode of a fuel cell, a catalyst having a composition represented by PtUM1-u is desirable. Here, u satisfies 0 < u ≦ 0.9, and the element M is at least one selected from the group consisting of Co, Ni, Fe, Mn, Ta, W, Hf, Si, Mo, Ti, Zr, Nb, V, Cr, Al, and Sn. This catalyst contains more than 0 atomic % and 90 atomic % or less of Pt, and 10 atomic % or more and less than 100 atomic % of the element M. When performing a hydrogen oxidation reaction as the anode of a fuel cell, a catalyst having a composition represented by PtvM1-v is desirable. Here, v satisfies 0 < v ≦ 0.6, and the element M is at least one selected from the group consisting of Co, Ni, Fe, Mn, Ta, W, Hf, Si, Mo, Ti, Zr, Nb, V, Cr, Al, and Sn. The element M may be one kind or a combination of two or more kinds of elements.

[0023] The power source ② is connected to the anode 1A and the cathode 1B. It is a means for applying a voltage having a potential cycle between both poles of the power source. The power source 2 has, for example, a configuration in which a battery (secondary battery) or a generator is combined with an inverter circuit or a converter circuit. The inverter circuit or the converter circuit converts the power from the battery or the generator into a waveform having a potential cycle. The voltage applied by the power source 2 to the anode 1A and the cathode 1B is controlled by the control circuit 3.

[0024] The control circuit 3 is connected to the power supply 2. The control circuit 3 controls the output of the power supply 2 by controlling, for example, an inverter circuit or a converter circuit of the power supply 2. The control circuit 3 is controlled, for example, by software or hardware. The control circuit 3 has an integrated circuit, for example, a microcontroller or a SoC (System on Chip). The control circuit 3 uses the integrated circuit within the control circuit 3 to control the output of the power supply 2. The control circuit 3 may also have a computer. In this case, the control circuit 3 uses the computer within the control circuit 3 to control the output of the power supply 2. The control circuit 3 may also be connected to a first supply device 4 and a second supply device 5. In this case, the control circuit 3 may also control the first supply device 4 and the second supply device 5.

[0025] The first supply device 4 is connected to the first diffusion layer 1D. For example, if the electrolysis system 100 is a water electrolysis system, the first supply device 4 supplies water to the anode 1A via the first diffusion layer 1D. The first supply device 4 includes, for example, a pump, a blower, and a valve. For example, the amount of water supplied to the anode 1A is controlled by the control circuit 3 controlling the pump, blower, and valve.

[0026] The second supply device 5 is a second diffusion layer 1E. The second supply device 5 supplies gas or liquid to the cathode 1B via the second diffusion layer 1E. The second supply device 5 includes, for example, a pump, a blower, and a valve. For example, the control circuit 3 controls the amount of gas or liquid supplied to the cathode 1B by controlling the pump, blower, and valve. Note that the second supply device 5 is not required to be provided.

[0027] Next, the operating method of the electrolytic apparatus of the embodiment will be described. The operating method of this electrolytic apparatus is an operating method that performs cleaning and aging (activation) treatment of the catalyst layer. The operating method includes an operating step of applying a voltage having a potential cycle using a power supply 2 connected to the anode 1A and cathode 1B.

[0028] The potential cycle includes a first step of applying a low potential to cathode 1B with anode 1A as the reference potential, and a second step of applying a high potential to cathode 1B with anode 1A as the reference potential, and repeating these steps. A voltage having a potential cycle is applied between anode 1A and cathode 1B with anode 1A as the reference potential. The potential cycle includes low potential and high potential, and preferably spans both low and high potential.

[0029] Impurities such as polymers may be adsorbed onto the catalyst layer during use of the electrolytic device. Furthermore, impurities may be introduced during the creation of the catalyst layer. If the catalyst surface becomes covered with these impurities, the catalytic activity decreases. The cleaning or aging (activation) treatment of the catalyst layer, as described in the operating method of the electrolytic device in this embodiment, removes the impurities from the catalyst layer. Therefore, the characteristics of the film electrode assembly 1 are restored or improved.

[0030] Furthermore, the catalyst layer contains materials that can function as co-catalysts, such as Ni. For example, consider using Ir and Ni in the catalyst layer of a water electrolysis device. If Ni forms an oxide with Ir, such Ni functions as a co-catalyst. However, if Ni does not form an oxide with Ir, such Ni inhibits the diffusion of fuel and other substances, leading to a deterioration of performance. Therefore, by applying the potential cycle of the embodiment, Ni that has not formed an oxide with Ir dissolves, and the effect of improving the diffusion of fuel and other substances can be obtained. In addition, by applying the potential cycle of the embodiment, Ir oxide dissolves and then re-deposits, which may cause the atoms on the catalyst surface to rearrange or result in a highly active surface. In that case, a good aging effect is expected to appear.

[0031] Furthermore, the processes that occur due to the cleaning and aging of the catalyst layer are not limited to those described above.

[0032] In the above potential cycle, the low potential is 1.45V or less, and the high potential is 2.0V or more. This potential cycle, which includes repeated low and high potentials, is used to clean or age the catalyst layer.

[0033] A low potential of 0.1V to 1.45V is preferable. If the low potential is higher than 1.45V, the potential is too high, resulting in insufficient cleaning effect and high performance recovery in the low potential state. Furthermore, below 0.1V, significant hydrogen generation occurs, posing a risk of hydrogen gas leakage from the electrode to the outside.

[0034] A high potential of 2.0V to 3.0V is preferable. Below 2.0V, the potential is too low, resulting in insufficient cleaning effect and high performance recovery in the high potential state. Above 3.0V, the dissolution of precious metals becomes significant, which may lead to a decrease in performance and is therefore undesirable.

[0035] The application time for high potential is preferably between 3 seconds and 60 seconds. Less than 3 seconds is too short, resulting in insufficient cleaning effect and high-performance recovery. Conversely, exceeding 60 seconds is undesirable as it can lead to significant dissolution of precious metals and a deterioration of performance.

[0036] It is preferable to repeat the potential cycle 3 to 500 times. 5 to 200 times is more preferable. Less than 3 cycles result in insufficient cleaning effect and high-performance recovery. 5 or more cycles provide sufficient cleaning effect and high-performance recovery. Exceeding 500 cycles is inefficient as a system operation method and has low practicality. From this perspective, 200 or more potential cycles are preferable.

[0037] Treating with either a high or low potential alone results in insufficient cleaning and high-performance recovery. When treated with either a high or low potential, the cleaning effect and high-performance recovery are reduced to less than 1 / 5 of what is achieved when treated with a potential cycle that alternates between high and low potentials. By repeatedly performing reduction and oxidation treatments, high cleaning effect and high-performance recovery become possible.

[0038] The waveform of the potential cycle is not particularly limited. For example, it is preferable to apply a triangular wave potential that changes between low and high potentials between anode 1A and cathode 1B. Alternatively, for example, it is preferable to apply a square wave or rectangular wave potential that changes between low and high potentials between anode 1A and cathode 1B. Alternatively, for example, it is preferable to apply a sine wave potential that changes between low and high potentials between anode 1A and cathode 1B.

[0039] Furthermore, when using the electrolytic apparatus operation method of the embodiment with respect to nanoparticle-sized precious metals, a large amount of precious metal leakage occurs. However, when the electrolytic apparatus operation method of the embodiment is applied to a porous precious metal or a porous catalyst layer containing a porous precious metal or sheet-like precious metal, the leakage of precious metal is significantly suppressed. The detailed mechanism for this is not yet fully understood. For example, it is presumed that the surface structure of the nanosheet-like precious metal catalyst and the structure of the precious metal catalyst layer composed of the porous precious metal or nanosheet-like precious metal significantly suppressed the leakage of precious metal. (Examples)

[0040] The following describes some examples.

[0041] Fabrication of Anode 1A A Ti nonwoven fabric substrate with dimensions of 25 cm x 25 cm and a thickness of 200 μm was prepared as the first diffusion layer 1D. Nickel and iridium were sputtered onto this first diffusion layer 1D to form a sheet layer. Subsequently, only nickel was sputtered to form a gap layer. This process of forming the sheet layer and gap layer was repeated 40 times until the Ir per area was 0.2 mg / cm². 2 A layered structure was obtained so that [the following structure was obtained]. Subsequently, a catalyst structure (porous catalyst layer of anode 1A) was obtained by washing with sulfuric acid to remove nickel. In this way, anode 1A was obtained.

[0042] Fabrication of Cathode 1B A carbon paper Toray060 (manufactured by Toray Industries, Inc.) with a carbon layer measuring 25 cm x 25 cm and a thickness of 190 μm was prepared as the second diffusion layer 1E. On this second diffusion layer 1E, a loading density of Pt (platinum) catalyst of 0.1 mg / cm³ was applied. 2 To achieve this, a catalyst layer having a layered structure including a void layer was formed by sputtering, and a catalyst structure having a porous catalyst layer (porous catalyst layer of cathode 1B) was obtained. In this way, cathode 1B was obtained.

[0043] A 30cm x 30cm Chemours Nafion 115 was used as the electrolyte membrane 20. A solution of tetraammineplatinum diluted to 11 wt% with water was sprayed onto the membrane. The Nafion 115 was masked with tape before spraying. After 10 minutes from spraying, it was rinsed with pure water, and finally boiled in 10 wt% nitric acid at 80°C for 1 hour to obtain an electrolyte membrane 1C impregnated with Pt particles.

[0044] Next, the anode 1A, cathode 1B, and electrolyte membrane 1C were placed in a hot press apparatus at 160°C and 20 kg / cm³. 2 A 3-minute press was performed at 25°C, 20 kg / cm³. Afterwards, the material was heated to 25°C and 20 kg / cm³. 2 Press cooling was performed for 3 minutes. This resulted in obtaining the film electrode assembly 1.

[0045] The obtained membrane electrode assembly 1 was incorporated into the electrolysis system 100. Next, water was supplied to the anode at a temperature of 80°C, and the system was operated at a current density of 0.8 A / cm² for 2 hours to 1 day for conditioning. The voltage during this conditioning was recorded as V0. Subsequently, the system was operated at a current density of 0.8 A / cm². The voltage after 20 hours of power generation was recorded as V1. After performing various potential cycle operations as shown in Table 1, the system was operated again at a current density of 0.8 A / cm², and the voltage after 20 hours of operation was recorded as V2. The value of (V2-V1) / (V0-V1) was calculated and recorded as the characteristic recovery rate. The above test was repeated 5 times. The average characteristic recovery rates are summarized in Table 1.

[0046] [Table 1]

[0047] As shown in Table 1 above, good recovery rates were obtained in Examples 1 to 10. On the other hand, in Comparative Example 1, the low potential was too high, resulting in insufficient cleaning effect and high-performance recovery. Similarly, in Comparative Example 2, the high potential was too low, resulting in insufficient cleaning effect and high-performance recovery.

[0048] In particular, good results were obtained in Examples 1 to 6, where the low potential was 0.1V to 1.45V, the high potential was 2.0V to 3.0V, and the application time of the high potential was 3 seconds to 60 seconds.

[0049] According to the embodiments described above, it is possible to provide a method for operating an electrolytic device with a long lifespan, a method for operating an electrolytic system, and an electrolytic system.

[0050] While several embodiments and examples of the present invention have been described, these embodiments and examples are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0051] Furthermore, the above embodiments can be summarized in the following technical proposal. Technical proposal 1 an anode comprising a porous catalyst layer containing a porous noble metal or a sheet-like noble metal, Cathode and, An electrolyte membrane is provided between the anode and the cathode, Using a membrane electrode assembly having, A first step involves applying a low potential of 1.45V or less to the anode relative to the cathode, using the anode's potential as the reference potential. A second step involves applying a high potential of 2.0V or more to the anode relative to the cathode, using the anode's potential as the reference potential. A method for operating an electrolytic device. Technical proposal 2 The aforementioned low potential is 0.1V or higher. Operating method of the electrolytic apparatus described in Technical Proposal 1. Technical proposal 3 The aforementioned high potential is 3.0V or less. A method for operating an electrolytic apparatus as described in Technical Proposal 1 or Technical Proposal 2. Technical proposal 4 A triangular wave-shaped potential that varies between the low potential and the high potential is applied between the anode and the cathode. A method for operating an electrolytic apparatus as described in any one of Technical Proposals 1 to 3. Technical proposal 5 A square wave-shaped potential that varies between the low potential and the high potential is applied between the anode and the cathode. A method for operating an electrolytic apparatus as described in any one of Technical Proposals 1 to 3. Technical plan 6 The cathode includes a porous catalyst layer containing a porous noble metal or a sheet-like noble metal. A method for operating an electrolytic apparatus as described in any one of Technical Proposals 1 to 5. Technical proposal 7 The low potential and the high potential are applied using the power supply connected to the anode and the cathode. An operating method for an electrolytic apparatus described in any one of Technical Proposals 1 to 6. Technical proposal 8 Apply the aforementioned high potential for 3 seconds to 60 seconds. A method for operating an electrolytic apparatus as described in any one of Technical Proposals 1 to 7. Technical proposal 9 An electrolytic apparatus described in any one of Technical Proposals 1 to 8, A power supply connected to the anode and the cathode, A control circuit connected to the power supply, A method for operating an electrolytic system equipped with the following features. Technical proposal 10 an anode comprising a plurality of first catalyst layers, each containing at least one of a precious metal and a precious metal oxide, and at least one of a non-precious metal and a non-precious metal oxide, Cathode and, An electrolyte membrane is provided between the anode and the cathode, A membrane electrode assembly having, The anode and the power supply connected to the cathode, A control circuit controls the power supply to perform a first step of applying a low potential of 1.45V or less to the cathode, using the potential of the anode as the reference potential, and a second step of applying a high potential of 2.0V or more to the cathode, using the potential of the anode as the reference potential. An electrolytic system equipped with the following features. [Explanation of symbols]

[0052] 1: Membrane electrode assembly 1A: Anode 1B: Cathode 1C: Electrolyte membrane 1D: First diffusion layer 1E: Second diffusion layer 2: Power supply 3: Control circuit 4: 1st supply device 5:Second supply device 20: Electrolyte membrane 80 :Temperature 90: Electrolyzer 100: Electrolytic System 200: Thickness M: Element Toray060: Carbon Paper

Claims

1. an anode comprising a porous catalyst layer containing a porous noble metal or a sheet-like noble metal, Cathode and, An electrolyte membrane is provided between the anode and the cathode, Using a membrane electrode assembly having, The first step involves applying a low potential of 0.1V to 1.45V to the anode, using the cathode potential as the reference potential. A second step involves applying a high potential of 2.0 V to 3.0 V for 3 seconds to 60 seconds, using the cathode potential as the reference potential. The potential cycle including this is repeated 3 to 500 times. Operating procedure for an electrolytic device.

2. A triangular wave-shaped potential that varies between the low potential and the high potential is applied between the anode and the cathode. A method for operating an electrolytic apparatus according to claim 1.

3. A square wave-shaped potential that varies between the low potential and the high potential is applied between the anode and the cathode. A method for operating an electrolytic apparatus according to claim 1.

4. The cathode includes a porous catalyst layer containing a porous noble metal or a sheet-like noble metal. A method for operating an electrolytic apparatus according to claim 1.

5. The low potential and the high potential are applied using the power supply connected to the anode and the cathode. A method for operating an electrolytic apparatus according to claim 1.

6. an anode comprising a porous catalyst layer containing a porous noble metal or a sheet-like noble metal, Cathode and, An electrolyte membrane is provided between the anode and the cathode, A membrane electrode assembly having, A power supply connected to the anode and the cathode, A control circuit connected to the power supply, Equipped with, A first step involves applying a low potential of 0.1V to 1.45V to the anode, using the cathode potential as the reference potential. A second step involves applying a high potential of 2.0 V to 3.0 V to the anode for 3 seconds to 60 seconds, using the cathode potential as the reference potential. The potential cycle including this is repeated 3 to 500 times. Operating procedure for an electrolysis system.

7. an anode comprising a plurality of first catalyst layers, each containing at least one of a precious metal and an oxide of a precious metal, and at least one of a non-precious metal and an oxide of a non-precious metal, Cathode and, An electrolyte membrane is provided between the anode and the cathode, A membrane electrode assembly having, The anode and the power supply connected to the cathode, A control circuit controls the power supply to repeat a potential cycle, which includes a first step of applying a low potential of 0.1V to 1.45V to the anode with the cathode potential as the reference potential, and a second step of applying a high potential of 2.0V to 3.0V to the anode for 3 seconds to 60 seconds, with the cathode potential as the reference potential, three to 500 times. An electrolytic system equipped with the following features.

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