JP7530626B2 - Electrochemical Single Cell - Google Patents

Description

The present invention relates to an electrochemical unit cell suitable for use in evaluating the performance of materials such as catalysts for alkaline water electrolysis, solid polymer water electrolysis, and solid polymer fuel cells through electrochemical testing.

Conventionally, there are known solid polymer water electrolysis cells having a structure capable of applying independent tightening forces to multiple parts of a cell stack in which multiple plate-like members are stacked, such as a tightening structure (see Patent Document 1) in which both end plates are evenly pressed with a predetermined pressure to tighten them (see Patent Document 2). For example, the solid polymer water electrolysis cell of Patent Document 2 includes a cell using a solid polymer electrolyte membrane, end plates stacked on the cell, a first flange and a second flange portion for sandwiching the stack including the cell and the end plate and applying a tightening force to the stack, a support member, and multiple tightening force adjustment members provided on the support member and capable of applying a pressing force to multiple parts of the center of the first flange portion under independent control.

Japanese Patent Application Publication No. 11-97054 JP 2002-302785 A

A single cell, which is the basic structure of conventional alkaline water electrolysis, solid polymer water electrolysis, and solid polymer fuel cells, is constructed by stacking cells consisting of an electrolyte membrane and anode and cathode electrodes arranged on both sides of the membrane, and end plates. In order to suppress the increase in internal resistance due to stacking, at least one end plate is tightened to the other end plate or intermediate plate at a specified pressure using an adjustment bolt or adjustment spring to improve contact and keep contact resistance low.

For example, in a polymer electrolyte fuel cell, increasing the pressure applied to the electrode and current collector surfaces reduces the contact resistance, thereby improving performance. However, at the same time, the pressure applied to the diffusion layer reduces the porosity, resulting in reduced diffusion and thus reduced performance.
In addition, the laminate on the inner side of the two end plates has a region facing the gasket in the laminate surface (hereinafter also referred to as the "gasket surface region") and a region having a membrane such as a diaphragm or electrolyte membrane, an electrode, a diffusion layer, a current collector, etc. (hereinafter also referred to as the "electrode surface region"). A design that increases the pressure on the electrode surface region, i.e., reducing the gasket thickness or changing the gasket material to a material that is easily elastically deformed, reduces the contact resistance in the surfaces of the membrane, electrode, diffusion layer, and current collector, but at the same time, there is a risk of causing liquid leakage from the gasket. Conversely, increasing the gasket thickness or changing the gasket material to a material that is less elastically deformable prevents liquid leakage from the gasket, but the pressure on the electrode surface region is reduced, which increases the contact resistance in the surfaces of the membrane, electrode, diffusion layer, and current collector, which may cause a decrease in performance. For this reason, in order to optimize performance in cell design, it is necessary to appropriately adjust the pressure applied to the electrode surface region while preventing liquid leakage from the gasket and accurately grasp the pressure in that region.

However, in conventional structures where the end plate is tightened with a predetermined tightening force using an adjustment bolt or adjustment spring to apply pressure to the internal laminate, the tightening force of the end plate simultaneously pressurizes two areas, the gasket surface area and the electrode surface area, making it difficult to accurately grasp the pressure applied to the electrode surface area.

Similarly, in alkaline water electrolysis and solid polymer water electrolysis, the pressure applied to the electrodes must be accurately understood in order to optimize performance in cell design, but with conventional structures, it was difficult to accurately grasp the pressure applied to the electrodes.

The present invention has been made in consideration of the above-mentioned problems, and aims to provide an electrochemical unit cell that can accurately measure and adjust the pressure applied to the electrodes in alkaline water electrolysis, solid polymer water electrolysis, and solid polymer fuel cells. By realizing such an electrochemical unit cell, it is possible to easily optimize the pressure applied to the electrochemical unit cell, improve the reliability of the evaluation results in performance comparisons, and further make it possible to evaluate membranes and electrodes using standardized test equipment and test conditions.

In order to achieve the above object, the electrochemical unit cell of the present invention is an electrochemical unit cell in which one of a cathode and an anode is arranged on one side of a membrane, and the other of the cathode and anode is arranged on the other side of the membrane, a gasket having an opening for one electrode, an electrode flow path plate, and an end plate for the one electrode are arranged in that order on the one electrode side of a membrane-electrode assembly, and a gasket having an opening for the other electrode and an end plate for the other electrode are arranged in that order on the other electrode side of the membrane-electrode assembly, and the membrane sandwiched between the end plate for the one electrode and the end plate for the other electrode are fastened and fixed together with the gasket on the one electrode side and the gasket on the other electrode side by a fastening member,
The end plate for the other electrode has an opening at a position facing the other electrode, an electrode flow path block that can be pressed toward the other electrode within the opening is arranged so as to be movable in a direction toward the other electrode independently of the end plate for the other electrode, and a pressure adjustment mechanism and a pressure measurement mechanism are arranged for the electrode flow path block.

In the electrochemical single cell of the present invention, the pressure adjustment mechanism can have a pressure adjustment spring and a spring compression adjustment screw, and the pressure measurement mechanism can have a graduated bar for reading the amount of spring compression of the pressure adjustment spring. By adjusting the amount of expansion and contraction of the pressure adjustment spring by rotating the spring compression adjustment screw and applying the elastic force of the pressure adjustment spring to the electrode through the electrode flow path block, it is possible to precisely and easily adjust the pressure applied to the membrane/electrode assembly without disassembling the cell.
Furthermore, in the electrochemical single cell of the present invention, by making the electrode flow path plate and the electrode flow path block replaceable parts, it is possible to change at least one of the flow path pattern of the cathode and the flow path pattern of the anode, and it is also possible to change at least one of the flow path size of the cathode and the flow path size of the anode.
The electrode size of the membrane-electrode assembly is set within a range of, for example, 0.5 cm×0.5 cm to 4 cm×4 cm, which allows evaluation of a small amount of catalyst.
The electrode flow path plate and the end plate for the other electrode can be provided with a reference electrode, which makes it possible to measure the cathode potential and the anode potential by electrically contacting, via the electrolyte, an area of the membrane surface different from the area in contact with the electrode.
In addition, by using a carbon material for the electrode flow path plate, a titanium material for the other electrode end plate, and a platinum-plated titanium material for the electrode flow path block, it is possible to measure both alkaline water electrolysis and solid polymer water electrolysis.

According to the present invention, the pressure on the electrodes can be accurately measured and adjusted. Therefore, when the membrane, electrode, or diffusion layer in the electrochemical cell is changed, or the material, structure, or shape of the current collector is changed, the pressure on the membrane, electrode, diffusion layer, and current collector can be easily and precisely changed. As a result, when evaluating the performance of the membrane, electrode, diffusion layer, or current collector due to changes in the material, structure, or shape, it is possible to easily optimize the pressure when comparing performance without preparing separate gaskets for each, and the reliability of the evaluation results can be improved.

FIG. 1 is an overall perspective view showing an electrochemical unit cell of Example 1. FIG. 1 is an exploded perspective view showing an electrochemical unit cell of Example 1. 3A and 3B are a side view and a front view showing an example of a cathode flow channel plate, which is a cathode-side part and a replaceable part in the electrochemical unit cell of Example 1. FIG. 4A and 4B are a side view and a front view showing another example of a cathode flow channel plate, which is an anode-side part and a replaceable part in the electrochemical unit cell of Example 1. FIG. 3A and 3B are a side view and a front view showing an example of a cathode end plate, which is a cathode-side part and a common part in the electrochemical unit cell of Example 1. FIG. 3A and 3B are a side view and a front view, respectively, showing an anode end plate, which is an anode-side part and a common part in the electrochemical unit cell of Example 1. 3A and 3B are a side view and a front view, respectively, showing an anode flow path block, which is an example of an anode-side part and a replaceable part in the electrochemical unit cell of Example 1. FIG. 3A and 3B are a side view and a front view, respectively, showing an anode flow path block, which is an example of an anode-side part and a replaceable part in the electrochemical unit cell of Example 1. FIG. 4A and 4B are a side view and a front view, respectively, showing a bus bar, which is a pressure adjusting part and a common part in the electrochemical unit cell of Example 1.

Below, an embodiment of the electrochemical single cell of the present invention will be described with reference to the drawings.

Example 1
The electrochemical unit cell of Example 1 is an electrochemical unit cell having a structure that allows pressure to be easily applied to the electrodes independently of pressure to the gaskets. By using the electrochemical unit cell of Example 1, the performance of catalysts for alkaline water electrolysis and solid polymer water electrolysis, and the material performance of solid polymer fuel cells can be evaluated by electrochemical tests. To this end, the electrochemical single cell of Example 1 is an electrochemical single cell in which one of a cathode and an anode is arranged on one side of a membrane, and the other of the cathode and anode is arranged on the other side of the membrane, a gasket having an opening for one electrode, an electrode flow path plate, and an end plate for the one electrode are arranged in that order on the one electrode side of the membrane-electrode assembly, and a gasket having an opening for the other electrode and an end plate for the other electrode are arranged in that order on the other electrode side of the membrane-electrode assembly, and the membrane sandwiched between the end plate for one electrode and the end plate for the other electrode are fastened and fixed together with the gasket on the one electrode side and the gasket on the other electrode side by a fastening member, in which the end plate for the other electrode has an opening at a position facing the other electrode, an electrode flow path block that can be pressed toward the other electrode is arranged within the opening so as to be movable in a direction toward the other electrode independently of the end plate for the other electrode, and a pressure adjustment mechanism and a pressure measurement mechanism for the electrode flow path block are also arranged.
Regarding the electrochemical unit cell A of Example 1, hereinafter, a specific example will be described in which the above-mentioned "one of the cathode and the anode" is the "cathode", the above-mentioned "the other of the cathode and the anode" is the "anode", the above-mentioned "electrode flow path plate" is the "cathode flow path plate", the above-mentioned "end plate for one electrode" is the "cathode end plate", the above-mentioned "end plate for the other electrode" is the "anode end plate", and the above-mentioned "electrode flow path block" is the "anode flow path block".
The configuration of the electrochemical unit cell A of Example 1 will be described below by dividing it into "overall configuration,""cathode side component configuration,""anode side component configuration," and "pressure regulating components."

[Overall configuration]
Fig. 1 is an overall perspective view showing an electrochemical unit cell A of Example 1, and Fig. 2 is an exploded perspective view showing the electrochemical unit cell A of Example 1. In the electrochemical unit cell A shown in Figs. 1 and 2, a pressure adjustment mechanism and a pressure measurement mechanism are disposed on the anode side of the membrane electrode assembly 1.

As shown in Figures 1 and 2, the electrochemical single cell A includes a membrane/electrode assembly 1, a gasket 2, a cathode flow path plate 3, a cathode end plate 4, an anode end plate 5, an anode flow path block 6, a bus bar 7, a bore-through joint 8, a pressure adjustment spring 9, a graduated bar 10, a fixing plate 11, a spring compression adjustment screw 12, a rotating rod 13, a cell fixing bolt 14, a cell fixing spacer 15, and a fixing plate fixing bolt 16.

As shown in FIG. 2, the cathode 1b side of the electrode of the membrane electrode assembly 1 is provided with a gasket 2, a cathode flow path plate 3, and a cathode end plate 4 arranged in this order. The anode 1c side of the membrane electrode assembly 1 is provided with a gasket 2 and an anode end plate 5 arranged in this order in the region (gasket surface region) facing the membrane of the membrane electrode assembly 1, and an anode flow path block 6, a bus bar 7, a pressure adjustment spring 9, a graduated bar 10, and a spring compression adjustment screw 12 arranged in this order in the region (electrode surface region) facing the anode of the membrane electrode assembly 1. The anode flow path block 6 is arranged inside the opening formed in the anode end plate 5 so as to be movable toward the anode. The bus bar 7 is screwed to the outer end of the anode flow path block 6. The bus bar 7 penetrates the anode end plate 5 through a bore-through joint 8. The bore-through joint 8 is fixed to the anode end plate 5. The bus bar 7 is movable in the axial direction when the bore-through joint 8 is not fastened, and is fixed by the bore-through joint 8 after fastening.
A cell fixing bolt 14 is disposed penetrating the cathode end plate 4, the cathode flow path plate 3, the gasket 2, the membrane electrode assembly 1, the gasket 2, and the anode end plate 5. The tip of the cell fixing bolt 14 is screwed into a rod-shaped cell fixing spacer 15. Both ends of the cell fixing spacer 15 are internally threaded, and one end of the cell fixing spacer 15 is screwed into the cell fixing bolt 14 to fasten the membrane electrode assembly 1, the gasket 2, the cathode flow path plate 3, the cathode end plate 4, and the anode end plate 5. A fixing plate 11 is disposed penetrating the cell fixing spacer 15 near the other end, and the fixing plate 11 is fixed by screwing the internal thread of the cell fixing spacer 15 into the fixing plate fixing bolt 16. A screw hole 11a is formed in the fixing plate 11 in the axial direction of the bus bar 7. A spring compression adjustment screw 12 is screwed into this screw hole 11a, and the spring compression adjustment screw 12 can move in the axial direction by rotating the spring compression adjustment screw 12. A rotating rod 13 for rotating the spring compression adjustment screw 12 forward or backward is attached near the base end of the spring compression adjustment screw 12. However, the means for rotating the spring compression adjustment screw 12 is not limited to the rotating rod shown in the figure. For example, a gear may be attached to the spring compression adjustment screw 12, and the gear may be driven by a motor to rotate the spring compression adjustment screw 12. The tip of the spring compression adjustment screw 12 abuts against one end of the graduated bar 10. The graduated bar 10 is capable of pressing the pressure adjustment spring 9 stored in the spring storage hole 7b formed at one end of the bus bar 7. The elastic force of the pressure adjusting spring 9 makes it possible to independently apply pressure to the anode 1c of the membrane electrode assembly 1 via the bus bar 7 and the anode flow path block.

In the first embodiment, the membrane-electrode assembly 1 shows an example of a single cell structure having the membrane-electrode assembly 1 for alkaline water electrolysis, solid polymer water electrolysis, or solid polymer fuel cell. In the illustrated example, a cathode 1b and an anode 1c, which are electrodes, are installed or joined to both end faces of an ion exchange membrane 1a having a rectangular planar shape. The membrane-electrode assembly 1 may have an ion-conductive membrane in which an electrolyte is impregnated in a porous membrane, instead of the ion exchange membrane 1a. The membrane-electrode assembly 1 may be one generally called a membrane-electrode assembly or MEA, but is not limited to one in which a membrane and an electrode are joined, and may also include one in which the two are in contact without being joined. In addition, the membrane-electrode assembly 1 may have a diffusion layer or a current collector installed on the outside of both electrodes.
The electrode sizes, which are determined by the vertical and horizontal lengths of the cathode 1b and anode 1c, vary, and those used in experiments and research include, for example, small sizes for evaluating the performance of a small amount of samples and large sizes for evaluating the performance of actual cells for mass production. Note that the ion exchange membrane 1a has a positioning hole 1d through which the cell fixing bolt 14 is inserted, as shown in Figure 2.

A pair of gaskets 2 with the same configuration are prepared. The gasket 2 has an electrode opening 2a in the center, and is a sealing member that exhibits a gas or liquid sealing function when the membrane/electrode body 1 is clamped and fixed by the cathode flow path plate 3 or the anode flow path block 6. The gasket 2 is made of an electrically insulating material such as a fluororubber sheet. In addition, the gasket 2 has a positioning hole 2b and an opening 2c for the reference electrode, as shown in Figure 2.

The positioning holes 1d, 2b, 3i, 4b, and 5h of the membrane/electrode assembly 1, gasket 2, cathode flow path plate 3, cathode end plate 4, and anode end plate 5 are drilled in exactly the same positions, and when assembling the electrochemical single cell A, the cell fixing bolt 14 with an insulating tube is inserted through it. Furthermore, the positioning hole 11b of the fixing plate 11 is used to insert the fixing plate fixing bolt. This makes it possible to position the membrane/electrode assembly 1, gasket 2, cathode flow path plate 3, cathode end plate 4, anode end plate 5, and fixing plate 11 in an appropriate positional relationship while suppressing misalignment between them.

A spring washer, washer, and insulating washer are provided between the cell fixing bolt 14 and the cathode end plate 4, between the cell fixing bolt 14 and the anode end plate 5, and between the fixing plate fixing bolt 16 and the fixing plate 11. The insulating washer is made of a chemical-resistant, insulating material such as polyether ether ketone.

[Cathode side component configuration]
FIGS. 3 and 4 show one example ( FIG. 3 ) and another example ( FIG. 4 ) of the cathode flow channel plate 3, which is a cathode-side part in the electrochemical unit cell of Example 1 and is prepared in a plurality of variations so as to be mutually interchangeable. FIG. 5 shows the cathode end plate 4, which is a cathode-side part and a common part in the electrochemical unit cell of Example 1.

The cathode flow path plate 3 has a cathode liquid flow path 3a formed opposite the cathode 1b of the membrane electrode assembly 1, and has a function of sending a reactant required for an electrochemical reaction (electrolyte in the case of alkaline water electrolysis, water in the case of solid polymer water electrolysis, and humidified hydrogen as a fuel electrode in the case of a solid polymer electrolyte fuel cell) to the cathode 1b of the membrane electrode assembly 1. In addition, a liquid-filled tube 3b is embedded in the cathode flow path plate 3. The liquid-filled tube 3b has a reference electrode opening 3c opposite the ion exchange membrane 1a, and has a structure in which the reference electrode 17 is electrically contacted with the ion exchange membrane 1a at the reference electrode opening 3c through the electrolyte liquid filled in the liquid-filled tube 3b. In order to electrically insulate the electrolyte from the surrounding members up to the reference electrode opening 3c, a chemical-resistant and insulating material such as a polyether ether ketone material is used for the liquid-filled tube 3b. In addition, the cathode flow path plate 3 can be provided with a thermocouple hole 3d for cell temperature management and measurement, and a terminal attachment hole 3e for applying current and voltage and measurement. The material of this cathode flow path plate 3, excluding the liquid filling tube 3b, the reference electrode 17, the bore-through joint 3f for the reference electrode 17, the inlet joint 3g, and the outlet joint 3h, is, for example, a thermally conductive material such as titanium or carbon.
As another example of the cathode flow passage plate 3, a cathode flow passage plate 3 shown in Fig. 4 can be prepared which has the same outer dimensions (length, width, and height) and material (e.g., a conductive member such as a carbon material) but has a different flow passage pattern. Note that the cathode flow passage plate 3 has positioning holes 3i through which the cell fixing bolts 14 are inserted, as shown in Fig. 3.

The cathode end plate 4 is a heat-conducting member having heater holes 4a. The cathode end plate 4 is made of, for example, stainless steel. As shown in FIG. 5, the cathode end plate 4 has positioning holes 4b through which the cell fixing bolts 14 are inserted.

[Anode side component configuration]
FIG. 6 shows the anode end plate 5, which is an anode-side part and a common part in the electrochemical unit cell of Example 1, and FIGS. 7 and 8 show one example ( FIG. 7 ) and another example ( FIG. 8 ) of the anode flow channel block 6, which is an anode-side part in the electrochemical unit cell of Example 1 and is prepared in a plurality of variations so as to be mutually interchangeable.

The anode end plate 5 has an opening 5a formed opposite the anode 1c of the membrane-electrode assembly 1, and contains the anode flow path block 6 inside this opening 5a. It has the function of sending the reaction substrate required for electrolysis (electrolyte in the case of alkaline water electrolysis, water in the case of solid polymer water electrolysis, and humidified air as an oxygen electrode in the case of a solid polymer fuel cell) to the anode 1c of the membrane-electrode assembly 1. In addition, a liquid-filled tube 5b is embedded in the anode end plate 5. The liquid charging tube 5b has a reference electrode opening 5c opposite the ion exchange membrane 1a, and has a structure in which the reference electrode 17 electrically contacts the ion exchange membrane at the reference electrode opening 5c through the electrolyte filled in the liquid charging tube 5b. The liquid-filled tube 5b is made of a chemical-resistant, insulating material such as polyether ether ketone material to electrically insulate the electrolyte from the surrounding components up to the reference electrode opening 5c. The anode end plate 5 can also be provided with a heater hole 5d for heating the cell. The material of this anode end plate 5, excluding the liquid filling tube 5b, the reference electrode 17, the bore-through joint 5e for the reference electrode 17, the inlet joint 5f, and the outlet joint 5g, is, for example, a thermally conductive material such as titanium material or carbon. As shown in FIG. 6, the anode end plate 5 has a positioning hole 5h through which the cell fixing bolt 14 is inserted, and a female thread 5i for screwing in the bore-through joint 8 through which the bus bar 7 is movably inserted.

The anode flow path block 6 forms an anolyte flow path 6a facing the anode 1c of the membrane electrode assembly 1, and also has an internal thread 6b for screwing one end of a bus bar 7. It has the function of transmitting pressure transmitted from the bus bar 7 connected to the internal thread 6b to the electrode surface area of the membrane electrode assembly 1. The anode flow path block 6 is movable only in the direction toward and away from the anode 1c of the membrane electrode assembly 1 while housed in the opening 5a of the anode end plate 5.
Another example of the anode flow passage block 6 is shown in Fig. 8. The anode flow passage block 6 in Fig. 8 has the same external dimensions (length, width, and height) and material (e.g., an electrically conductive, thermally conductive, and corrosion-resistant material such as platinum-plated titanium) as the anode flow passage block 6 in Fig. 7, and can be prepared with, for example, a changed flow passage pattern.

[Pressure adjustment parts]
FIG. 9 shows the bus bar 7, which is a pressure adjusting part and a common part in the electrochemical unit cell of Example 1.

The rod-shaped busbar 7 has a male thread 7a formed at one end that connects with a female thread 6b of the anode flow path block 6, and a spring storage hole 7b formed at the other end, in which a pressure adjustment spring 9 is stored. Inside the spring storage hole 7b, the pressure adjustment spring 9 is compressed via a graduated bar 10 by the axial movement of a spring compression adjustment screw 12, and transmits pressure obtained from the elastic force to the anode flow path block 6. It also has the function of conducting electricity between the terminal installed in the terminal hole 7c of the busbar 7 and the anode flow path block 6. The material of this busbar 7 is, for example, an electrically conductive material such as titanium.

Next, the effects of the electrochemical single cell of the present invention will be explained using electrochemical single cell A of Example 1 as a specific example. The electrochemical single cell of the present invention is suitable for use in alkaline water electrolysis, solid polymer water electrolysis, and evaluation of material performance of solid polymer fuel cells.

Traditionally, the material performance of alkaline water electrolysis, solid polymer water electrolysis, and solid polymer fuel cells has generally been evaluated by testing catalysts using the rotating disk electrode method, and other materials, including catalysts, by electrolysis testing using a single cell.

Catalyst evaluation using a three-electrode test with the rotating disk electrode method is different from catalyst evaluation for fuel cells based on actual equipment in that it is a gas generation reaction, and because of the structure of the rotating disk electrode cell, gas remains on the catalyst, so it is generally difficult to perform highly accurate measurements.

On the other hand, even if evaluation is carried out by electrolytic testing using a single cell, it is difficult for material developers to design and manufacture a single cell and carry out the evaluation. For this reason, several single cells for testing and research purposes are sold and used.

However, conventional single cells for testing and research required skill to assemble and perform electrolytic evaluation. In addition, differences in cell assembly technology can lead to differences in performance, and when evaluating materials using conventional single cells, the performance of the same material often differs depending on the evaluator, making it difficult to compare performance between different material developers. This makes it difficult to properly evaluate materials.

In conventional single cells, one of the major factors that caused the measured absolute performance to differ from test to test or from evaluator to evaluator was the difficulty in controlling the pressure applied to the membrane, electrodes, diffusion layer, current collector, etc. This is because the pressure applied when fastening the end plates of the single cell with bolts and nuts is applied to both the electrodes and gaskets that are sandwiched between the separators, making it difficult to accurately know the pressure applied to the electrodes. In addition, pressure adjustment was performed by managing and adjusting the fastening torque that fastens the end plates with bolts and nuts, making it difficult to adjust precisely.

In addition, controlling the pressure on the electrodes and optimizing performance is necessary in material development, but the pressure on the electrodes is affected by the thickness, elasticity, and area of the gasket, as well as the thickness, elasticity, and area of the membrane, electrode, diffusion layer, current collector, etc. Furthermore, since it is necessary to ensure the sealing properties of the gasket, it has been difficult to precisely control the pressure on the electrodes.

On the other hand, with new prototype catalysts, the amount of sample that can be produced is very small, so it may be possible to produce only a small catalyst layer of, for example, about 1 cm square. In this case, taking into account the handling of the cell, the cell body needs to be a certain size (for example, about 5 to 10 cm square). With this design, the ratio of the gasket area to the electrode area is inevitably large, and most of the pressure applied by the bolts and nuts is applied to the gasket. For this reason, the difficulty of controlling the pressure on the electrode surface increases even more when the electrode area is reduced.

In contrast, in the electrochemical single cell of the present invention, as in electrochemical single cell A described with reference to the drawings, the member in contact with the electrode surface area on the anode side is the anode flow path block 6, and the member in contact with the gasket surface area is the anode end plate 5, each of which is an independent separate part. A structure is adopted in which the pressure applied to the membrane, electrode, diffusion layer, current collector, etc. can be precisely controlled by applying pressure to the anode flow path block 6 from outside the cell via the bus bar 7 using the elasticity of the pressure adjustment spring 9.

The electrochemical unit cell A having the above structure provides the following effects.
The pressure applied to the membrane/electrode body 1, diffusion layer, current collector, etc. can be precisely controlled without being affected by the thickness, elasticity, and area of the gasket 2, or the thickness, elasticity, and area of the membrane/electrode body 1, diffusion layer, current collector, etc., or the fastening pressure of the electrochemical cell due to the screwing of the cell fixing bolts 14 and the cell fixing spacer 15. Therefore, the time required to control the pressure applied to the electrodes can be significantly reduced by selecting the gasket material and shape and adjusting the cell fastening pressure.
In evaluation tests in which the pressure on the electrode surface is gradually changed to optimize electrolysis performance, the pressure can be easily and precisely changed during the experiment without disassembling the electrochemical cell.
When fastening the electrochemical single cell A using the cell fixing bolts 14 and the cell fixing spacer 15, care must be taken only to prevent liquid leakage from the gasket 2, so there is no need for strict fastening torque management when fastening the cell, as was required with conventional electrochemical cells.
- Because performance differences due to differences in cell assembly technology between evaluators are kept extremely low, material developers can compare material performance using a unified standard.

As an example of a method for using the electrochemical unit cell of the present invention, an electrochemical test for evaluating the performance of materials such as catalysts will be described below, including a method for assembling the electrochemical unit cell.
Electrochemical tests are carried out to evaluate the performance of the membrane/electrode body 1, the diffusion layer, the current collector, etc. In this electrochemical test, when the amount of sample is very small for a new prototype catalyst, etc., an electrolytic cell with a small electrode size (for example, 1 cm square) is used. Even when the amount of sample is large, the electrode size is standardized to, for example, 1 cm square to unify it with the electrode size when the amount of sample is very small, so that a standardized test can be carried out and performance comparison between each sample can be easily performed. The electrode size is not limited to 1 cm square, and can be, for example, in the range of 0.5 cm x 0.5 cm to 4 cm x 4 cm. The planar shape of the electrode is not limited to a square, and can be a rectangle with one side in the range of 0.5 to 4.0 cm.

The optimal gasket 2, cathode flow path plate 3, anode end plate 5, anode flow path block 6, and pressure adjustment spring 9 according to the test conditions are selected according to the size of the membrane/electrode body 1. Then, the electrochemical single cell A is constructed by combining the common parts, cathode end plate 4, bus bar 7, bore-through joint 8, graduated bar 10, fixing plate 11, spring compression adjustment screw 12, rotating rod 13, cell fixing bolt 14, cell fixing spacer 15, fixing plate fixing bolt 16, and reference electrode 17, with the prepared membrane/electrode body 1, diffusion layer, current collector, etc., and the selected gasket 2, cathode flow path plate 3, anode end plate 5, anode flow path block 6, and pressure adjustment spring 9.

The bore-through joint 8, spring compression adjustment screw 12, cell fixing bolt 14, cell fixing spacer 15, fixing plate fixing bolt 16, and reference electrode 17 can be commercially available standard products. In addition, the bore-through joint 3f, inlet joint 3g, and outlet joint 3h, which are components of the cathode flow path plate 3, and the bore-through joint 5e, inlet joint 5f, and outlet joint 5g, which are components of the anode end plate 5, can also be commercially available standard products.

The predetermined membrane electrode assembly 1, gasket 2, cathode flow path plate 3, cathode end plate 4, and anode flow path block 6 are arranged side by side, and the male thread 7a of the bus bar 7 is screwed into the female thread 6b of the anode flow path block 6, and the anode flow path block 6 is inserted into the opening 5a of the anode end plate 5. The cell is fastened by screwing the cell fixing bolt 14 and the cell fixing spacer 15 into the positioning holes 1d, 2b, 3i, 4b, and 5h of the membrane electrode assembly 1, gasket 2, cathode flow path plate 3, cathode end plate 4, and anode end plate 5, respectively. At this time, an insulating tube is attached to the threaded portion of the cell fixing bolt 14, and insulating bushes are attached to both ends to prevent short-circuiting of the cell. The fastening torque of the cell fixing bolt 14 and the cell fixing spacer 15 does not need to be strictly optimized, and may be an appropriate value that ensures the sealing properties of the gasket 2.

The female thread 5i of the anode end plate 5 is fastened to the bore-through joint 8, and the bus bar 7 and the bore-through joint 8 are initially left untightened so that the bus bar 7 can move axially within the bore-through joint 8. The pressure adjustment spring 9 and the scaled bar 10 are placed in this order in the spring storage hole 7b of the bus bar 7. The cell fixing spacer 15 and the fixing plate fixing bolt 16 are fastened by screwing them through the positioning hole 11ba of the fixing plate 11. The spring compression adjustment screw 12 is attached to the threaded hole 11a of the fixing plate 11, and the rotating rod 13 is attached to the rotating rod hole 12a of the spring compression adjustment screw 12.

The scaled bar 10 is moved by rotating the spring compression adjustment screw 12 in the forward direction using the rotating rod 13, and the pressure adjustment spring 9 is compressed. The scaled bar 10 is moved by rotating the spring compression adjustment screw 12 in the reverse direction, and the pressure adjustment spring 9 is expanded. The elastic force of this pressure adjustment spring 9 is applied to the cathode 1b and anode 1c of the membrane electrode body 1 and the electrode surface area of the ion exchange membrane 1a, the diffusion layer, the current collector, etc. through the bus bar 7 and the anode flow path block 6. The scaled bar 10 is graduated, and the contracted length of the pressure adjustment spring 9 is obtained from the position of the scaled bar 10 when the pressure adjustment spring 9 is at its natural length and when it is contracted. The pressure can be easily obtained from this length and the elastic coefficient of the pressure adjustment spring 9, and the pressure can be precisely controlled by rotating the spring compression adjustment screw 12 to move the scaled bar 10 slightly.

After setting the specified pressure, the busbar 7 and bore-through joint 8 are fastened.

In the assembled state of the electrochemical single cell A shown in Figure 1, electrochemical testing is performed by sending reactive substrates required for electrolysis to the cathode 1b and anode 1c of the membrane/electrode body 1 at a specified cell temperature.

The cell temperature is heated by rod heaters installed in heater hole 4a in cathode end plate 4 and heater hole 5d in anode end plate 5, and the temperature is measured and controlled by a thermocouple installed in thermocouple hole 3d in cathode flow path plate 3. The tip of the thermocouple is installed near the center of the cathode liquid flow path 3a in cathode flow path plate 3, so it is possible to measure values close to the temperatures of the cathode 1b and anode 1c, diffusion layer, current collector, etc. of the membrane/electrode body 1. This has the effect of minimizing the discrepancy between the actual temperature of the evaluation material and the set cell temperature, improving the accuracy of the experiment.

On the cathode side, in the cathode flow path plate 3 in FIG. 3, the supplied liquid flows through the inlet joint 3g → inlet tube 3j → inlet manifold 3k into the cathode liquid flow path 3a and the cathode 1b of the membrane-electrode body 1. Then, hydrogen gas and liquid are discharged through the outlet manifold 3l → outlet tube 3m → outlet joint 3h. Meanwhile, the reference electrode 17 fixed by the bore-through joint 3f is in contact with the electrolyte liquid filled in the liquid filling tube 3b. The electrolyte liquid is filled up to the reference electrode opening 2c of the gasket 2 through the reference electrode opening 3c, and is in electrical contact with the ion exchange membrane, so the cathode potential can be measured between the reference electrode 17 and the terminal connected to the terminal mounting hole 3e.

On the anode side, the anode flow path block 6 in FIG. 7 is inserted into the opening 5a of the anode end plate 5 in FIG. 6, and the supplied liquid flows through the inlet joint 5f → inlet tube 5j → inlet manifold 5k into the anode liquid flow path 6a and the anode 1c of the membrane electrode body 1 shown in FIG. 7. Then, oxygen gas and liquid are discharged through the outlet manifold 5l → outlet tube 5m → outlet joint 5g. On the other hand, the reference electrode 17 fixed by the bore-through joint 5e is in contact with the electrolyte liquid filled in the liquid filling tube 5b. The electrolyte liquid is filled up to the reference electrode opening 2c of the gasket 2 through the reference electrode opening 5c, and is in electrical contact with the ion exchange membrane, so the anode potential can be measured between the reference electrode 17 and the terminal connected to the terminal hole 7c of the bus bar 7.

The performance of the entire cell is measured between the terminal attached to the terminal attachment hole 3e of the cathode flow path plate 3 and the terminal attached to the terminal hole 7c of the bus bar 7. During measurement, the pressure applied to the membrane/electrode body 1, diffusion layer, current collector, etc. can be precisely and easily controlled by rotating the spring compression adjustment screw 12 and the rotating rod 13 without disassembling the cell.

The electrochemical single cell of the present invention has been described above based on Example 1. However, the specific configuration is not limited to Example 1, and design changes and additions are permitted as long as they do not deviate from the gist of the present invention.

For example, in the first embodiment, two types of flow path patterns are prepared for the cathode flow path plate 3 and the anode flow path block 6: a parallel flow path (see Figs. 3 and 7) and no flow path (see Figs. 4 and 8). However, the flow paths of the cathode flow path plate 3 and the anode flow path block 6 are not limited to these two types, and serpentine flow paths, comb-shaped flow paths, etc. may be prepared depending on the purpose.

In Example 1, an example of an electrochemical single cell A was shown, in which the material performance of alkaline water electrolysis, solid polymer water electrolysis, catalysts for solid polymer fuel cells, etc. was evaluated by electrochemical testing. However, the configuration of the electrochemical single cell disclosed in the present invention may be used as the configuration or technical concept of an electrochemical single cell in an actual device.

In the first embodiment, the pressure adjustment mechanism includes the pressure adjustment spring 9 and the spring compression adjustment screw 12, but the pressure adjustment mechanism is not limited to including the pressure adjustment spring 9 and the spring compression adjustment screw 12. Any means capable of linearly moving the anode flow path block 6 and the bus bar 7 may be used, and for example, a linear actuator or the like may be used for the pressure adjustment mechanism. However, the pressure adjustment mechanism shown in the first embodiment has a simple mechanical structure and can realize pressure adjustment that is inexpensive and has few malfunctions.
Furthermore, the pressure measurement mechanism includes the graduated bar 10 combined with the pressure adjustment spring 9, but is not limited to including this graduated bar 10. For example, it may be a sensor capable of measuring the amount of displacement (amount of compression) of the pressure adjustment spring 9. It may also be a load cell attached to the bus bar 7. However, the pressure measurement mechanism shown in the first embodiment has a simple mechanical structure and can realize pressure measurement and adjustment that is inexpensive and has few malfunctions.

In addition, in the above-described Example 1, an example was shown in which the electrochemical single cell A has a pressure adjustment mechanism and a pressure measurement mechanism arranged on the anode side of the membrane/electrode body 1, but the pressure adjustment mechanism and the pressure measurement mechanism may also be arranged on the cathode side of the membrane/electrode body 1. The electrochemical unit cell in this case is configured as follows: an anode among the electrodes is arranged on one side of a membrane, and a cathode among the electrodes is arranged on the other side of the membrane; a gasket having an opening for the anode, an anode flow path plate, and an anode end plate are arranged in that order on the anode side of a membrane-electrode assembly; a gasket having an opening for the cathode and a cathode end plate are arranged in that order on the cathode side of the membrane-electrode assembly; the membrane sandwiched between the anode end plate and the cathode end plate are fastened and fixed together with the anode-side gasket and the cathode-side gasket by fastening members; the cathode end plate has an opening at a position facing the cathode, and a cathode flow path block that can be pressed toward the cathode is arranged within the opening so as to be movable in a direction toward the cathode independently of the cathode end plate; and a pressure adjustment mechanism and a pressure measurement mechanism are also arranged for the cathode flow path block. That is, in the electrochemical single cell of the present invention, as a specific example, the "one of the cathode and anode" can be the "anode", the "other of the cathode and anode" can be the "cathode", the "electrode flow path plate" can be the "anode flow path plate", the "one electrode end plate" can be the "anode end plate", the "other electrode end plate" can be the "cathode end plate", and the "electrode flow path block" can be the "cathode flow path block". This configuration also has the same effect as the configuration described above with reference to Figures 1 and 2.

A Electrochemical single cell 1 Membrane/electrode body 1a Ion exchange membrane (porous membrane)
1b Cathode 1c Anode 1d Positioning hole 2 Gasket 2a Electrode opening 2b Positioning hole 2c Reference electrode opening 3 Cathode flow path plate 3a Cathode liquid flow path 3b Liquid filling tube 3c Reference electrode opening 3d Thermocouple hole 3e Terminal mounting hole 3f Bored-through joint 3g Inlet joint 3h Outlet joint 3i Positioning hole 3j Inlet tube 3k Inlet manifold 3l Outlet manifold 3m Outlet tube 4 Cathode end plate 4a Heater hole 4b Positioning hole 5 Anode end plate 5a Opening 5b Liquid filling tube 5c Reference electrode opening 5d Heater hole 5e Bored-through joint 5f Inlet joint 5g Outlet joint 5h Positioning hole 5i Female thread 5j Inlet tube 5k Inlet manifold 5l Outlet manifold 5m Outlet tube 6 Anode flow path block 6a Anode liquid flow path 6b Female thread 7, bus bar 7a, male thread 7b, spring storage hole 7c, terminal hole 8, bore-through joint 9, pressure adjustment spring 10, scaled bar 11, fixing plate 11a, screw hole 11b, positioning hole 12, spring compression adjustment screw 12a, rotating rod hole 13, rotating rod 14, cell fixing bolt 15, cell fixing spacer 16, fixing plate fixing bolt 17, reference electrode

Claims (8)

An electrochemical unit cell used in performance evaluation or in an actual machine for alkaline water electrolysis, solid polymer water electrolysis, or solid polymer fuel cell, the electrochemical unit cell comprising: a membrane-electrode assembly having one of a cathode and an anode disposed on one side of a membrane, and the other of the cathode and anode disposed on the other side of the membrane; a gasket having an opening for the one electrode, an electrode flow path plate, and an end plate for the one electrode disposed in that order on the one electrode side of the membrane-electrode assembly; a gasket having an opening for the other electrode and an end plate for the other electrode disposed in that order on the other electrode side of the membrane-electrode assembly; and the membrane sandwiched between the end plate for the one electrode and the end plate for the other electrode are fastened and fixed together with the gasket on the one electrode side and the gasket on the other electrode side by fastening members,
an electrode flow path block that can be pressed toward the other electrode within the opening and is disposed so as to be movable in a direction toward the other electrode independently of the end plate for the other electrode; and a pressure adjustment mechanism and a pressure measurement mechanism are disposed for the electrode flow path block. An electrochemical single cell according to claim 1, characterized in that the pressure adjustment mechanism has a pressure adjustment spring and a spring compression adjustment screw, and the pressure measurement mechanism has a graduated bar for reading the amount of spring compression of the pressure adjustment spring. An electrochemical single cell according to claim 2, characterized in that the amount of expansion and contraction of the pressure adjustment spring is adjusted by rotating the spring compression adjustment screw, and the elastic force of the pressure adjustment spring is applied to the electrode through the electrode flow path block, making it possible to precisely and easily adjust the pressure applied to the membrane/electrode assembly without disassembling the cell. An electrochemical single cell according to any one of claims 1 to 3, characterized in that the electrode flow path plate and the electrode flow path block are each replaceable parts, making it possible to change at least one of the flow path pattern of the cathode and the flow path pattern of the anode. An electrochemical single cell according to any one of claims 1 to 4, characterized in that the electrode flow path plate and the electrode flow path block are each replaceable parts, making it possible to change at least one of the flow path size of the cathode and the flow path size of the anode. An electrochemical single cell according to any one of claims 1 to 5, characterized in that the electrode size of the membrane/electrode assembly is set to a range of 0.5 cm x 0.5 cm to 4 cm x 4 cm, making it possible to evaluate a small amount of catalyst. An electrochemical single cell according to any one of claims 1 to 6, characterized in that a reference electrode is provided on the electrode flow path plate and the other electrode end plate, and the cathode potential and the anode potential can be measured by electrically contacting, via an electrolyte, an area of the membrane surface that is different from the area in contact with the electrode. 8. The electrochemical single cell according to claim 1, wherein a carbon material is used for the electrode flow path plate, a titanium material is used for the other electrode end plate, and a platinum-plated titanium material is used for the electrode flow path block, thereby making it possible to use the electrochemical single cell for measuring either alkaline water electrolysis or solid polymer water electrolysis.

Images