Water electrolytic cell stack diagnostic method and water electrolytic cell stack diagnostic system

Abstract

To easily diagnose deterioration of a water electrolytic cell stack.SOLUTION: A water electrolytic cell stack diagnostic method comprises: preparing, in advance, deterioration determination data having information on a relationship between a current density and a voltage increase rate corresponding to deterioration at the time of first voltage application for a proton exchange membrane-type water electrolytic cell stack; supplying a sweep voltage to the proton exchange membrane-type water electrolytic cell stack to be diagnosed and detecting, as a determination current density, a current density at the first voltage; and determining a degree of deterioration of the proton exchange membrane-type water electrolytic cell stack to be diagnosed based on the voltage increase rate in the deterioration determination data corresponding to the detected determination current density.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis cell stack diagnostic method and a water electrolysis cell stack diagnostic system for a water electrolysis cell stack that electrolyzes water to generate hydrogen and oxygen. [Background technology]

[0002] Conventionally, water splitting systems have been proposed that electrolyze water into hydrogen and oxygen using a water electrolysis cell stack that uses a solid polymer electrolyte membrane. Diagnosing the deterioration state of such a water splitting cell stack requires disassembly of the water electrolysis cell stack and analysis of each cell and component, which requires time and effort.

[0003] Patent Document 1 proposes a method for operating a fuel cell during long-term storage, in which a fuel cell stack generates electricity at a small partial load, monitors the increase in cell voltage due to generated water, increases the load when a predetermined voltage is reached, and restores the humid state while monitoring the slope of the change in cell voltage.The technology described in Patent Document 1 determines the humid state of the fuel cell stack, but cannot diagnose the degree of deterioration of the anode catalyst in the water electrolysis cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2010-086692 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a water electrolysis cell stack diagnostic method and a water electrolysis cell stack diagnostic system that can easily diagnose deterioration of a water electrolysis cell stack. [Means for solving the problem]

[0006] A first aspect of the water electrolysis cell stack diagnosis method includes: preparing deterioration determination data in advance, the deterioration determination data having relationship information between a current density and a voltage increase rate corresponding to deterioration when a first voltage is applied to a proton exchange membrane water electrolysis cell stack; supplying a sweep voltage to the proton exchange membrane water electrolysis cell stack to be diagnosed, and detecting the current density at the first voltage as a determination current density; and determining the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed based on the voltage increase rate of the deterioration determination data corresponding to the detected determination current density.

[0007] In a proton exchange membrane water electrolysis cell stack, the voltage increase rate relative to the current density increases as the cell stack deteriorates. Therefore, in a first aspect of the water electrolysis cell stack diagnosis method, relationship information between the current density and the voltage increase rate when a first voltage is applied, depending on the state of deterioration, is prepared in advance as deterioration determination data. Next, a sweep voltage is supplied to the proton exchange membrane water electrolysis cell stack to be diagnosed, and the current density at the first voltage is detected as a determination current density. Then, the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed is determined based on the voltage increase rate of the deterioration determination data corresponding to the detected determination current density.

[0008] In this way, the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed can be easily diagnosed without dismantling it or analyzing each cell or component.

[0009] A second aspect of the water electrolysis cell diagnosis method includes: preparing second deterioration determination data in advance, the second deterioration determination data having relationship information between a current density and a voltage increase rate corresponding to deterioration when a second voltage different from the first voltage is applied to the proton exchange membrane water electrolysis cell stack; supplying a sweep voltage to the proton exchange membrane water electrolysis cell stack to be diagnosed, and detecting the current density at the second voltage as a second determination current density; and determining the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed, taking into account the voltage increase rate of the second deterioration determination data corresponding to the detected second determination current density.

[0010] In a second aspect of the water electrolysis cell stack diagnosis method, second deterioration determination data having information on the relationship between the current density and the voltage increase rate corresponding to deterioration when a second voltage different from the first voltage is applied to the proton exchange membrane water electrolysis cell stack to be diagnosed is prepared in advance. Next, a sweep voltage is supplied to the proton exchange membrane water electrolysis cell stack to be diagnosed, and the current density at the second voltage is detected as a second determination current density. Then, the voltage increase rate of the second deterioration determination data corresponding to the detected second determination current density is taken into account to determine the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed.

[0011] In this way, by using the second deterioration determination data and the second determination current density, the degree of deterioration of the proton exchange membrane water electrolysis cell to be diagnosed can be determined with high accuracy.

[0012] A third aspect of the water electrolysis cell diagnostic method is the water electrolysis cell stack diagnostic method of the first or second aspect, wherein the first voltage is set to a voltage at a portion where a difference in current density depending on the degradation state is equal to or greater than a predetermined amount when a sweep voltage is supplied.

[0013] By setting the first voltage in this manner, the difference in current density increases depending on the degree of deterioration of the proton exchange membrane water electrolysis cell to be diagnosed, making it easier to determine the degree of deterioration.

[0014] A fourth aspect of the water electrolysis cell stack diagnostic method is the water electrolysis cell stack diagnostic method of any one of the first to third aspects, wherein the proton exchange membrane water electrolysis cell stack includes a catalyst layer-equipped electrolyte membrane in which an anode catalyst layer is formed on one surface of the electrolyte membrane and a cathode catalyst layer is formed on the other surface of the electrolyte membrane.

[0015] According to the water electrolysis cell stack diagnosis method of the fourth aspect, the degree of deterioration of a proton exchange membrane water electrolysis cell stack caused by deterioration of a catalyst layer of an electrolyte membrane with a catalyst layer can be easily determined.

[0016] In a fifth aspect of the water electrolysis cell stack diagnostic method, the anode catalyst contained in the anode catalyst layer contains iridium oxide.

[0017] According to the water electrolysis cell stack diagnosis method of the fifth aspect, it is possible to easily determine the degree of deterioration of a proton exchange membrane water electrolysis cell stack caused by deterioration of iridium oxide as an anode catalyst contained in an anode catalyst layer.

[0018] A water electrolysis cell stack diagnostic system according to a sixth aspect includes: a storage unit that pre-stores deterioration determination data having relationship information between a current density and a voltage increase rate corresponding to deterioration when a first voltage is applied to a proton exchange membrane water electrolysis cell stack; a detection unit that supplies a sweep voltage to the proton exchange membrane water electrolysis cell stack to be diagnosed and detects the current density at the first voltage as a determination current density; and a determination unit that determines a degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed, based on the voltage increase rate of the deterioration determination data that corresponds to the detected determination current density.

[0019] In a proton exchange membrane water electrolysis cell stack, the rate of voltage increase relative to the current density increases as the cell stack deteriorates. Therefore, in a sixth aspect of the water electrolysis cell stack diagnostic system, relationship information between the current density and the voltage increase rate when a first voltage is applied is stored in advance in a storage unit as deterioration determination data according to the deterioration state. Next, a sweep voltage is applied to the proton exchange membrane water electrolysis cell stack to be diagnosed, and the current density at the first voltage is detected by a detection unit as a determination current density. Then, the determination unit determines the degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed based on the voltage increase rate of the deterioration determination data corresponding to the detected determination current density.

[0020] In this way, the degree of deterioration of the proton exchange membrane water electrolysis cell to be diagnosed can be easily determined without dismantling the water electrolysis cell stack or analyzing each cell or component. [Effects of the Invention]

[0021] The water electrolysis system according to the present disclosure can provide a water electrolysis cell stack diagnostic method and a water electrolysis cell stack diagnostic system that can easily diagnose deterioration of a water electrolysis cell stack. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram illustrating the configuration of a proton exchange membrane water electrolysis cell stack that is the subject of a water electrolysis cell stack diagnostic method according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a proton exchange membrane water electrolysis cell. [Figure 3] 10 is a graph showing an example of the relationship between the degree of deterioration and the rate of voltage increase. [Figure 4] (A) is a graph showing the relationship between voltage and current density when a sweep voltage is applied according to the degree of deterioration, (B) is an enlargement of part (1) in (A), and (C) is an enlargement of part (2) in (A). [Figure 5] 10 is a graph showing the relationship between current density and voltage increase rate, illustrating an example of first deterioration determination data. [Figure 6] 10 is a graph showing the relationship between current density and voltage increase rate, illustrating an example of second deterioration determination data. [Figure 7] FIG. 2 is a block diagram of a control unit of the water electrolysis cell stack diagnostic system according to the present embodiment. [Figure 8] 10 is a flowchart of a degradation diagnosis process. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] 1 shows a schematic configuration of a proton exchange membrane water electrolysis cell stack 10 that is the subject of diagnosis by a water electrolysis cell stack diagnosis method according to an embodiment of the present disclosure. The proton exchange membrane water electrolysis cell stack 10 is configured by stacking a plurality of proton exchange membrane water electrolysis cells 20.

[0025] 2, each proton exchange membrane water electrolysis cell 20 includes an electrolyte membrane 21, and on one side of the electrolyte membrane 21, an anode catalyst layer 22, an anode gas diffusion layer 24, and a separator 28. On the other side of the electrolyte membrane 21, a cathode catalyst layer 32, a cathode gas diffusion layer 34, and a separator 38 are provided.

[0026] A carbon-fluorine based polymer membrane or the like can be used as the electrolyte membrane 21. An anode catalyst layer 22 is laminated on one surface of the electrolyte membrane 21. An Ir based catalyst, such as iridium oxide, can be used as the anode catalyst layer 22. A cathode catalyst layer 32 is laminated on the other surface of the electrolyte membrane 21. A Pt / carbon based catalyst or the like can be used as the cathode catalyst layer 32.

[0027] The anode gas diffusion layer 24 and the cathode gas diffusion layer 34 can be made of a material that allows fluid to flow through the layer, such as a porous material, a sintered powder compact, a sintered fiber compact, a metal mesh, or felt. A separator 28 is laminated on the anode gas diffusion layer 24 on the side opposite the electrolyte membrane 21. A separator 38 is laminated on the cathode gas diffusion layer 34 on the side opposite the electrolyte membrane 21. The separators 28 and 38 are made of a conductive material, and a voltage is applied to them. The separators 28 and 38 can be made of titanium, stainless steel, carbon, or the like.

[0028] The separator 28 has flow path through-holes 28A and 28B. Water is supplied to the anode gas diffusion layer 24 through the flow path through-hole 28A, and oxygen and unreacted water are sent out of the proton exchange membrane water electrolysis cell 20 through the flow path through-hole 28B. The separator 38 has a flow path through-hole 38A. Hydrogen is sent out of the proton exchange membrane water electrolysis cell 20 through the flow path through-hole 38A. A voltage is applied between the separators 28 and 38 by a voltage application means 42.

[0029] When water is supplied to the anode gas diffusion layer 24 through the flow path through-holes 28A and a voltage is applied between the separators 28 and 38, the following reaction (1) occurs on the surface of the anode catalyst layer 22. H2O → 2H + + 0.5O2+ 2e - (1)

[0030] Oxygen O2 is diffused in the anode gas diffusion layer 24 and is sent out from the flow path through-hole 28B together with unreacted water (H2O).

[0031] Hydrogen proton H + moves to the cathode side through the electrolyte membrane 21 and converts electrons e supplied by external wiring - (reaction (2)) to become hydrogen H2, which is then sent out from the flow path through-hole 38A. 2H + + 2e - → H2(2)

[0032] In this manner, in the proton exchange membrane water electrolysis cell 20, water is electrolyzed into hydrogen and oxygen.

[0033] Next, a method for diagnosing the proton exchange membrane water electrolysis cell stack 10 will be described.

[0034] <Data for determining deterioration> In this embodiment, the deterioration is diagnosed using deterioration determination data, which contains information on the relationship between the current density and the voltage increase rate according to the degree of deterioration for proton exchange membrane water electrolysis cell stacks 10 of the same configuration.

[0035] The voltage increase rate here refers to the rate of increase in voltage when a constant current is passed through the proton exchange membrane water electrolysis cell stack 10, with the voltage of a reference proton exchange membrane water electrolysis cell stack 10 without degradation as a reference. The voltage increase rate corresponding to the degree of degradation of the proton exchange membrane water electrolysis cell stack 10 is obtained in advance. As an example, as shown in FIG. 3, the voltage increase rate can be associated with a degree of degradation of 0 to 10. Note that the degree of degradation of 0 represents a reference state with no degradation, and the degree of degradation increases as the number from 1 increases. Information on the degree of degradation corresponding to the voltage increase rate is referred to as a "degradation rating D." In FIG. 3, the degree of degradation of 0-10, which is also associated with a voltage increase rate Z described below, is the degradation rating D.

[0036] Furthermore, a sweep voltage is applied to the proton exchange membrane water electrolysis cell stack 10 to obtain the relationship between voltage and current density according to the degree of deterioration. As an example, the voltage is swept at 100 mV / s for a reference stack S0 (unused), a first stack S1 (used for 50 cycles), a second stack S2 (used for 70,000 cycles), and a third stack S3 (used for 300,000 cycles) and folded back at 1.3 V, resulting in the relationship shown in FIG. 4(A). FIG. 4(B) is an enlargement of portion (1) in FIG. 4(A), and FIG. 4(C) is an enlargement of portion (2) in FIG. 4(A).

[0037] Here, the first voltage E1 and second voltage E2, which will be described later, are set as voltages at which the difference in current density depending on the degradation state becomes equal to or greater than a predetermined amount A0 when a sweep voltage is supplied. The predetermined amount A0 is set in consideration of the portion where the difference in current density depending on the degradation state becomes relatively large from the relationship profile between voltage and current density during the sweep. It is also preferable to set the first voltage E1 and second voltage E2 so that the voltage difference becomes as large as possible. In FIG. 4(A), the difference in current density depending on the degradation state becomes large at 0.46 V and 1.23 V. When the predetermined amount A0 is set to 20 mA / cm 2 Then, since it is larger than A0, the first voltage E1 can be set to 0.46V and the second voltage E2 can be set to 1.23V.

[0038] Next, the relationship between the voltage increase rate at the first voltage E1 and the current density is obtained according to the degree of deterioration. As an example, when the voltage increase rate at the first voltage E1 and the current density are plotted for multiple proton exchange membrane water electrolysis cell stacks 10 having the same configuration but different degrees of deterioration, including the aforementioned reference stack S0 (unused), the first stack S1 (used for 50 cycles), the second stack S2 (used for 70,000 cycles), and the third stack S3 (used for 300,000 cycles), the relationship shown in FIG. 5 is obtained. For the plot in FIG. 5, straight lines A1, A2, and A3 can be set as approximation lines. The relationship between the voltage increase rate at the first voltage E1 and the current density is referred to as first deterioration determination data J1. The first deterioration determination data J1 is stored in advance.

[0039] Similarly, when the relationship between the voltage increase rate and the current density for the second voltage E2 is plotted, the relationship shown in FIG. 6 is obtained. For the plot in FIG. 6, straight lines B1 and B2 can be set as approximate lines. The relationship between the voltage increase rate and the current density at the second voltage E2 is referred to as second deterioration determination data J2. The second deterioration determination data J2 is stored in advance.

[0040] <Determination of the degree of deterioration> A sweep voltage is applied to the proton exchange membrane water electrolysis cell stack 10 to be diagnosed, and the current density at a first voltage E1 is detected as a determination current density I1. A sweep voltage is also applied, and the current density at a second voltage E2 is detected as a determination current density I2. Voltage increase rates Z1 and Z2 corresponding to the detected determination current densities I1 and I2 are obtained by referring to the first deterioration determination data J1 and the second deterioration determination data J2.

[0041] Based on the voltage increase rates Z1 and Z2, a judgment voltage increase rate Z of the proton exchange membrane water electrolysis cell stack 10 is obtained. For example, when the judgment current density I1 is 13.5 mA / cm 2 In this case, referring to the first deterioration determination data J1 in Fig. 5, two values ​​of 3.8% and 1.2% are obtained as the voltage increase rate Z1. On the other hand, when the determination current density I2 is 50.0 mA / cm 2In this case, a value of 2.8% to 4.2% is obtained as the voltage increase rate Z2. Therefore, 3.8%, which satisfies both the voltage increase rates Z1 and Z2, is obtained as the judged voltage increase rate Z.

[0042] The degradation state of the proton exchange membrane water electrolysis cell stack 10 is then determined based on the determination voltage increase rate Z. The degradation evaluation D shown in Fig. 3 is then used. For example, when the voltage increase rate is 3.8%, the degradation level is determined to be 8, as shown in Fig. 3.

[0043] According to the water electrolysis cell stack diagnosis method of this embodiment, the degree of deterioration of the proton exchange membrane water electrolysis cell stack 10 to be diagnosed can be easily diagnosed without dismantling the proton exchange membrane water electrolysis cell stack 10 to be diagnosed or analyzing each cell or component.

[0044] In this embodiment, the voltage increase rate Z is calculated using both the first deterioration determination data J1 and the second deterioration determination data J2, but the voltage increase rate Z may be calculated based on only one of them. By calculating the voltage increase rate Z using both the first deterioration determination data J1 and the second deterioration determination data J2 as in this embodiment, the degree of deterioration of the proton exchange membrane water electrolysis cell to be diagnosed can be determined with high accuracy.

[0045] In addition, in this embodiment, the first voltage E1 and the second voltage E2 are set to a voltage at which the difference in current density depending on the deterioration state becomes equal to or greater than a predetermined amount A0 when a sweep voltage is supplied. Therefore, the difference in current density becomes larger depending on the degree of deterioration, making it easier to determine the deterioration.

[0046] <Water electrolysis cell stack diagnostic system> The water electrolysis cell stack diagnostic method of this embodiment can be performed using a water electrolysis cell stack diagnostic system 50. As shown in Fig. 7, the water electrolysis cell stack diagnostic system 50 includes a control unit 52. The control unit 52 is connected to a voltage application means 42, a display unit 43, and an input unit 44.

[0047] As shown in FIG. 7, the control unit 52 includes a CPU (Central Processing Unit) 53, a ROM (Read Only Memory) 54, a RAM (Random Access Memory) 55, an input / output interface (I / O) 56, and a storage unit 57.

[0048] The CPU 53, ROM 54, RAM 55, and I / O 56 are connected to each other via a bus 58. The I / O 56 is connected to various functional units including a storage unit 57. These functional units can communicate with the CPU 53 via the I / O 56.

[0049] The storage unit 57 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), or a flash memory. The storage unit 57 stores a control program for controlling the water electrolysis cell stack diagnostic system 50 and various data (first deterioration determination data J1, second deterioration determination data J2, first voltage E1, second voltage E2, deterioration evaluation D, etc.). The control program and various data may be stored in the ROM 54.

[0050] The deterioration diagnosis of the proton exchange membrane water electrolysis cell stack 10 to be diagnosed is performed in the following procedure.

[0051] When an instruction to start a degradation diagnosis is input from the input unit 44, the control unit 52 executes the degradation diagnosis process shown in FIG. 8. For the proton exchange membrane water electrolysis cell stack 10 to be diagnosed, in step S10, a sweep voltage is applied and the current density at a first voltage E1 is detected as a determination current density I1. In step S12, a sweep voltage is applied and the current density at a second voltage E2 is detected as a determination current density I2. In step S14, first degradation determination data J1 is read out, and in step S16, a voltage increase rate Z1 corresponding to the determination current density I1 is obtained by referring to the first degradation determination data J1. In step S18, second degradation determination data J2 is read out, and in step S20, a voltage increase rate Z2 corresponding to the determination current density I2 is obtained by referring to the second degradation determination data J2. In step S22, a determination voltage increase rate Z for the proton exchange membrane water electrolysis cell stack 10 is determined based on the voltage increase rates Z1 and Z2. Then, in step S24, the deterioration state is acquired by referring to the deterioration evaluation D, and in step S26, the deterioration state is displayed on the display unit 43, and the process ends.

[0052] The water electrolysis cell stack diagnostic system 50 of this embodiment can also be used to easily diagnose the degree of deterioration of the proton exchange membrane water electrolysis cell stack 10 to be diagnosed, without dismantling it or analyzing each cell or component. [Explanation of symbols]

[0053] 10. Proton exchange membrane water electrolysis cell stack 20 Proton exchange membrane water electrolysis cell J1 First deterioration judgment data (deterioration judgment data) J2 Second deterioration judgment data (Second deterioration judgment data) I1 Current density for judgment I2 Current density for judgment (current density for second judgment) Z Judgment voltage increase rate (voltage increase rate) Z1, Z2, voltage increase rate

Claims

1. preparing deterioration determination data in advance, the deterioration determination data including information on the relationship between the current density and the voltage increase rate corresponding to deterioration when the first voltage is applied to the proton exchange membrane water electrolysis cell stack; applying a sweep voltage to a proton exchange membrane water electrolysis cell stack to be diagnosed and detecting a current density at the first voltage as a current density for determination; determining a degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed based on a voltage increase rate of the deterioration determination data corresponding to the detected determination current density; Water electrolysis cell stack diagnostic method.

2. preparing in advance second deterioration determination data having information on the relationship between a current density and a voltage increase rate corresponding to deterioration when a second voltage different from the first voltage is applied to the proton exchange membrane water electrolysis cell stack; supplying a sweep voltage to the proton exchange membrane water electrolysis cell stack to be diagnosed and detecting a current density at the second voltage as a second current density for determination; determining a degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed, taking into consideration a voltage increase rate of the second deterioration determination data corresponding to the detected second determination current density; The water electrolysis cell stack diagnostic method according to claim 1 .

3. the first voltage is set to a voltage at a portion where a difference in current density depending on a deterioration state becomes equal to or greater than a predetermined amount when a sweep voltage is supplied; The water electrolysis cell stack diagnostic method according to claim 1 .

4. the proton exchange membrane water electrolysis cell stack includes a catalyst layer-equipped electrolyte membrane in which an anode catalyst layer is formed on one surface of the electrolyte membrane and a cathode catalyst layer is formed on the other surface of the electrolyte membrane; The method for diagnosing a water electrolysis cell stack according to any one of claims 1 to 3.

5. the anode catalyst contained in the anode catalyst layer contains iridium oxide; The water electrolysis cell stack diagnostic method according to claim 4.

6. a storage unit that stores in advance degradation determination data having information on the relationship between a current density and a voltage increase rate corresponding to degradation when a first voltage is applied to the proton exchange membrane water electrolysis cell stack; a detection unit that applies a sweep voltage to a proton exchange membrane water electrolysis cell stack to be diagnosed and detects a current density at the first voltage as a current density for determination; a determination unit that determines a degree of deterioration of the proton exchange membrane water electrolysis cell stack to be diagnosed based on a voltage increase rate of the deterioration determination data corresponding to the detected determination current density; A water electrolysis cell stack diagnostic system equipped with the above.

Images