JP2024023781A - Hydrogen production cell and hydrogen production method using hydrogen production cell - Google Patents

Abstract

To provide a hydrogen production cell of which a thickness per cell is reduced as compared with a conventional one.SOLUTION: A hydrogen side current collector 12 and an oxygen side current collector 13 are arranged on both sides of an electrolyte membrane 11. A separator 14 with a flat surface is arranged outside the hydrogen side current collector 12. A flow passage forming plate 15 and a separator 16 are arranged outside the oxygen side current collector 13. Since a flow passage dedicated for collecting water and a hydrogen gas generated when electrolysis is performed is not formed between the hydrogen side current collector 12 and the separator 16, the thickness of the cell itself can be reduced. These reaction fluids generated during the electrolysis are discharged from the inside of the hydrogen side current collector 12.SELECTED DRAWING: Figure 3

Description

The present invention relates to a hydrogen production cell and a hydrogen production method using the hydrogen production cell.

Conventionally, an oxygen side current collector and a hydrogen side current collector are disposed on both sides of a solid polymer electrolyte with an electrode catalyst layer formed on both sides, and a A sheet-like separator, called a separator, is arranged outside each of the current collectors and partitions adjacent cells, and has a configuration in which the oxygen side current collector and the hydrogen side current collector are sandwiched between the hydrogen side current collectors. A manufacturing cell has been proposed (Patent Document 1).

In such a case, between the separator, the oxygen side current collector, and the hydrogen side current collector, in order to form a dedicated flow path for the reaction fluid generated by electrolysis, a flow path having irregularities on the surface is formed. A board is provided. Moreover, without separately providing this flow path forming plate, irregularities for forming dedicated flow paths for the reaction fluid are formed on the surface of the separator on the side of each of the current collectors.

Japanese Patent Application Publication No. 2012-117140

However, as described above, if a flow path forming plate having unevenness for forming a flow path for the reaction fluid is provided between the oxygen side current collector, the hydrogen side current collector, and the separator, the hydrogen production cell increases in thickness. The same applies when the surface of the separator is formed with unevenness that forms a flow path for the reaction fluid.

This type of hydrogen production cell is used in the form of a cell stack in which dozens or more of these cells are laminated, and the above-mentioned hydrogen production cell has an uneven flow path forming plate that forms a flow path for the reaction fluid, and has an uneven surface. If there is a separator, even if it is only about 1 mm thick, if it is a cell stack made up of dozens or more cells, it will occupy a space of several centimeters to several tens of centimeters in the thickness direction. Put it away. Therefore, it is desired to make the hydrogen production cell itself more compact.

The present invention has been made in view of this point, and aims to solve the above-mentioned problems by realizing a structure of a hydrogen production cell that can reduce the thickness per cell compared to the conventional one.

In order to achieve the above object, the present invention provides an oxygen side current collector and a hydrogen side current collector disposed on both sides of a solid polymer electrolyte having an electrode catalyst layer formed on both sides, and a hydrogen side current collector and a hydrogen side current collector. A hydrogen production cell for producing hydrogen by water electrolysis, having a configuration in which the oxygen side current collector and the hydrogen side current collector are sandwiched between separators disposed on the outside of each side current collector,
The hydrogen side current collector side surface of the separator disposed outside the hydrogen side current collector is flat, and the separator disposed outside the hydrogen side current collector and the hydrogen side current collector are flat. A special feature is that there is no dedicated channel for collecting the reaction fluid generated during electrolysis between them.

According to the inventor, the hydrogen-side current collector used in this type of hydrogen production cell has a large number of organically connected voids inside. Therefore, without forming a special flow path exclusively for the reaction fluid on the outside as in the past, by ensuring an appropriate porosity of the hydrogen side current collector, hydrogen gas and water generated during electrolysis can be removed. It has been newly found that it is possible to discharge and recover the hydrogen-side current collector through the void inside the hydrogen-side current collector. Therefore, there is no need to provide a conventional flow path forming plate or a separator having irregularities for forming flow paths on the outside of the hydrogen side current collector. Therefore, the thickness per cell can be reduced accordingly.

The hydrogen side current collector preferably has a porosity of 50% to 99%. Since the reaction fluid is discharged and recovered through the pores inside the hydrogen side current collector, it is preferable to use a hydrogen side current collector having a porosity within this range.

The hydrogen gas and water recovery portions generated from the hydrogen side current collector may be formed on a pair of opposing sides of the hydrogen side current collector. In this case, it is preferable that a plurality of the collecting parts are formed on each of the opposing sides. By forming a plurality of them, collection efficiency can be increased.

It is preferable that the hydrogen side current collector has a shape having a long side and a short side, and the recovery parts are formed on each of the opposing long sides. This reduces the pressure resistance when moving inside the hydrogen-side current collector, allowing prompt recovery.

According to another aspect, there is a hydrogen production method using the hydrogen production cell described above, in which a voltage is applied between the oxygen side current collector and the hydrogen side current collector, and the hydrogen side current collector is It is also possible to propose an invention characterized by generating hydrogen gas from.

According to the present invention, the thickness per cell can be reduced compared to the prior art. Furthermore, the number of parts constituting the cell can be reduced, and costs can also be kept low. Furthermore, as will be described later, it is possible to improve the performance of the cell itself and extend the life of the cell compared to the conventional method.

FIG. 1 is an explanatory diagram schematically showing a system of a hydrogen production device incorporating a hydrogen production cell according to an embodiment. FIG. 1 is an exploded perspective view of a hydrogen production cell according to an embodiment. FIG. 2 is a partially enlarged horizontal sectional view of the hydrogen production cell according to the embodiment. FIG. 1 is an explanatory diagram schematically showing the internal structure of a hydrogen production cell according to an embodiment. It is an explanatory view showing the flow of reaction fluid in a hydrogen side current collector. FIG. 3 is an explanatory diagram showing the flow of a reaction fluid in a flow path forming plate. FIG. 2 is an explanatory diagram of a hydrogen-side current collector having a plurality of reaction fluid recovery sections.

Embodiments will be described below. FIG. 1 schematically shows a system of a hydrogen production device 1 incorporating a hydrogen production cell according to an embodiment, and this hydrogen production device 1 is constructed using a solid polymer type hydrogen production system shown in FIGS. 2 to 4, which will be described later. It is constructed by connecting and stacking several tens to hundreds of hydrogen production cells in series in the horizontal direction while holding the hydrogen production cell 10 upright in the vertical direction, and sandwiching the hydrogen production cell 10 between end plates 2 and 3 from both sides. It has a hydrogen production cell stack 4.

For example, pure water, which serves as raw water, is supplied to the pure water inlet port P1 of the hydrogen production cell stack 4. Specifically, raw water (pure water) is supplied from a tank 21 having a gas-liquid separation function on the oxygen side to the pure water inlet port P1, which is the raw water inlet of the hydrogen production cell stack 4, and water electrolysis is performed. operation (hydrogen production operation).

More specifically, a pipe 22 is connected between the bottom of the tank 21 and the pure water inlet port P1 of the hydrogen production cell stack 4. A pump 23 provided in the pipe 22 supplies pure water as raw water from the tank 21 to the pure water inlet port P1 of the hydrogen production cell stack 4. The piping 22 is provided with a check valve 24 on the downstream side of the pump 23, and further downstream thereof is provided with a pressure gauge 25 for measuring the pressure inside the piping 22. The pure water inlet port P1 communicates with a communication port (details will be described later) in each of the hydrogen production cells 10.

A return pipe 26 for returning part of the water flowing through the pipe 22 to the tank 21 is connected to the pipe 22 on the downstream side of the pump 23 . This return pipe 26 is provided with a flow rate adjustment valve V1, a heat exchanger 27, an ion exchange resin column 28, and a filter 29, and by processing the return water through these devices, the water in the tank 21 is reduced. Water quality is maintained. Note that a liquid level sensor 21a is provided in the tank 21 to detect the water level in the tank. Further, the tank 21 is appropriately replenished with pure water, which serves as raw water, from an external pure water supply source (not shown) through a pipe 30 based on a signal from the liquid level sensor 21a. Further, the oxygen gas remaining in the gas layer within the tank 21 is released outside the system through the piping 33 or transferred to an external customer.

The raw water supplied to the hydrogen production cell stack 4 from the pure water inlet port P1 through the piping 22 is electrolyzed in the hydrogen production cell stack 4, and oxygen and undecomposed water are converted into pure water that becomes the outlet on the oxygen side. The gas is returned to the tank 21 from the outlet port P2 through the piping 31, and is separated into gas and liquid within the tank 21. The piping 31 is provided with a pressure gauge 32 that measures the pressure inside the piping 31 and a solenoid valve V2. Note that the check valve 24, pump 23, pressure gauge 32, and solenoid valve V2 may be omitted. The pure water outlet port P2 communicates with a communication port (not shown) in the hydrogen production cell 10.

A pipe 41 is connected to hydrogen outlet ports P3 and P4, which serve as hydrogen side exits of the hydrogen production cell stack 4, and this pipe 41 communicates with a tank 42 having a gas-liquid separation function on the hydrogen side. The hydrogen outlet ports P3 and P4 communicate with a communication port (not shown) in the hydrogen production cell 10.

There is a space between the tank 42 and the air layer part of the tank 21 (the part above the level of the water stored in the tank, and the part where the liquid level does not reach even if the level of the stored water rises). , and piping 43 are connected. The piping 43 is provided with a solenoid valve V3 and a valve V4. A liquid level sensor 42a is provided within the tank 42 to detect the level of water within the tank.

Hydrogen generated by water electrolysis is sent to a tank 42 through a pipe 41 along with associated water, and is separated into gas and liquid within the tank 42. The hydrogen gas after being separated into gas and liquid in the tank 42 is sent to the demand side or a hydrogen storage tank (high pressure container, not shown) through a pipe 44, for example. A back pressure valve V5 is provided in the pipe 44, a discharge pipe 45 is connected to the upstream side of the back pressure valve V5 in the pipe 44, and a solenoid valve V6 is provided in the discharge pipe 45.

A DC power supply 5 is connected to the hydrogen production cell stack 4, and pure water for electrolysis supplied from the pure water inlet port P1 is electrolyzed into hydrogen ions and oxygen ions according to its output. Of these, the oxygen ions become oxygen molecules on the catalyst in the hydrogen production cell 10, and as described above, are discharged from the cell from the pure water outlet port P2 together with the pure water.On the other hand, the hydrogen ions generated by electrolysis release the accompanying water. Accordingly, the hydrogen moves to the hydrogen side in the hydrogen production cell 10, becomes hydrogen molecules on the hydrogen side catalyst, and is discharged from the hydrogen outlet ports P3 and P4 to the outside of the cell.

Next, the hydrogen production cell 10 according to the embodiment will be explained. As shown in FIGS. 2 to 4, this hydrogen production cell 10 has a structure in which an electrolyte membrane 11, which is a solid polymer electrolyte, is sandwiched between a hydrogen side current collector 12 and an oxygen side current collector 13. There is. The electrolyte membrane 11 has catalysts 11b and 11c on both surfaces of a solid polymer membrane 11a.

A separator 14, which is a separator, is arranged outside the hydrogen side current collector 12. For example, carbon paper, carbon nonwoven fabric, or the like is used as the material for the hydrogen side current collector 12, and a large number of organically connected voids are formed inside the hydrogen side current collector 12. In this example, a hydrogen side current collector 12 with a porosity of 50% or more is used. The surface of the hydrogen side current collector 12 in the separator 14 is formed flat. Flatness here does not necessarily mean completely flat. Grooves and minute irregularities may be formed between the hydrogen side current collector 12 and the separator 14 to such an extent that a dedicated flow path for the reaction fluid is not formed. However, the closer the flatness is, the more the effect of the present invention can be obtained due to uniform pressure contact by the entire surface of the electrode, as will be described later.

The material of the oxygen side current collector 13 is, for example, a titanium porous body having a predetermined rigidity, such as titanium fiber sintered nonwoven fabric or titanium sintered metal. A flow path forming plate 15 is arranged outside the oxygen side current collector 13. A separator 16, which is a separating body, is arranged on the outside of the flow path forming plate 15. The flow path forming plate 15 is made of a material such as an embossed plate, mesh, punched metal, etc., which has many irregularities 15a formed on its surface. As a result, a dedicated flow path 15b for the reaction fluid is formed between the oxygen side current collector 13 and the flow path forming plate 15, and the fluid can flow in both the vertical and horizontal directions. Ru. Note that the flow path forming plate 15 and the separator 16 may be integrally formed. That is, instead of using the flow path forming plate 15, a conventionally known separator having irregularities for forming reaction flow paths formed on the entire surface of one side may be used.

As shown in FIG. 2, the electrolyte membrane 11, hydrogen side current collector 12, oxygen side current collector 13, separator 14, flow path forming plate 15, and separator 16 that constitute the hydrogen production cell 10 all have a horizontally long rectangular shape. have. Each component constituting the hydrogen production cell 10, that is, the electrolyte membrane 11, the hydrogen side current collector 12, the oxygen side current collector 13, the separator 14, the flow path forming plate 15, and the separator 16, are all described below. A communication port is formed.

That is, the electrolyte membrane 11 has communication ports 11d to 11g formed at four corners. The hydrogen side current collector 12 has communication ports 12d and 12g formed at the upper left corner and the lower right corner, respectively. Communication ports 13e and 13f are formed in the oxygen side current collector 13 at the lower left corner and the upper right corner, respectively. The separator 14 has communication ports 14d to 14g formed at four corners. Communication ports 15e and 15f are formed in the flow path forming plate 15 at the lower left corner and the upper right corner, respectively. The separator 16 has communication ports 14d to 14g formed at four corners, respectively.

The communication ports of the constituent members constituting the hydrogen production cell 10 described above are not connected to each other and are independent. Moreover, there is no interference between each component. For example, each configuration in the hydrogen production cell 10 may be provided with a sealing material around each communication port, or an appropriate sealing material may be provided on the surface of each component facing the electrode, that is, the area corresponding to the electrolyte membrane 11. The reaction fluid is prevented from leaking from the end face of the member. The communication ports 11d and 11g of the electrolyte membrane 11 communicate with the communication ports 12d and 12g of the hydrogen side current collector 12, the communication ports 14d and 14g of the separator 14, and the communication ports 16d and 16g of the separator 16, as described above. It communicates with hydrogen outlet ports P3 and P4 of the hydrogen production cell stack 4. The communication ports 12d and 12g of the hydrogen side current collector 12 constitute a recovery section.

Similarly, the communication port 11e of the electrolyte membrane 11 communicates with the communication port 14e of the separator 14, the communication port 13e of the oxygen side current collector 13, the communication port 15e of the flow path forming plate 15, and the communication port 16e of the separator 16. It communicates with the pure water inlet port P1 of the hydrogen production cell stack 4. Further, the communication port 11f of the electrolyte membrane 11 communicates with the communication port 14f of the separator 14, the communication port 13f of the oxygen side current collector 13, the communication port 15f of the flow path forming plate 15, and the communication port 16f of the separator 16 to produce hydrogen. It communicates with the pure water outlet port P2 of the cell stack 4.

The hydrogen production cell 10 according to the embodiment has the above configuration. Next, its effects will be explained. Pure water, which is raw water, is supplied to each hydrogen production cell 10 in the hydrogen production cell stack 4 from the pure water inlet port P1 of the hydrogen production cell stack 4. When a voltage is applied from the DC power source 5 to each hydrogen production cell 10, the pure water is electrolyzed as shown in FIG. Gas is generated. Further, the outer surface of the hydrogen-side current collector 12 is not formed with a flow path exclusively for the reaction fluid, and furthermore, the hydrogen-side current collector 12 has a void inside thereof (in practice). (the porosity is 50% to 90%), this water and the hydrogen gas containing water pass through the inside of the hydrogen side current collector 12, and as shown in FIG. Head to 12d and 12g. Water and hydrogen gas containing moisture are then discharged from the communication ports 12d and 12g to the hydrogen outlet ports P3 and P4 of the hydrogen production cell stack 4.

On the other hand, in the oxygen side current collector 13 of the hydrogen production cell 10, the pure water that was supplied from the communication port 13e and which was not electrolyzed and the generated oxygen gas exit the oxygen side current collector 13 and pass through the flow path forming plate. It flows out to the 15 side. As shown in FIGS. 3 and 4, due to the presence of the channel forming plate 15 having the unevenness 15a, a channel 15b exclusively for the reaction fluid is formed between the oxygen side current collector 13 and the channel forming plate 15. Therefore, the undecomposed pure water and the generated oxygen gas head to the communication port 15f and are discharged to the pure water outlet port P2 of the hydrogen production cell stack 4, as shown in FIG. .

As described above, according to the hydrogen production cell 10 according to this embodiment, it is necessary to provide a conventional flow path forming plate or a separator of a separator having flow paths on the outer surface of the hydrogen side current collector 12. Therefore, the thickness per cell can be reduced compared to the conventional method. Further, it is possible to reduce the number of parts and simplify the structure.

Furthermore, since a flat separator with no irregularities on the surface is located on the outer surface of the hydrogen side current collector 12, the hydrogen side current collector 12, which has extremely low rigidity, is placed against the electrolyte membrane 11. Can be brought into full contact. Therefore, the adhesion between the electrolyte membrane 11 serving as an electrode and the hydrogen side current collector 12 is improved. In the case of a conventional separator having unevenness for forming a flow path forming plate or flow path on the outer surface of the hydrogen side current collector 12, line contact or point contact with the peaks or convex portions of the grooves is required. However, compared to that, the contact area increases and the contact resistance decreases. Therefore, the performance itself as a hydrogen production cell is improved.

Moreover, since the electrolyte membrane 11 and the hydrogen-side current collector 12 are in pressure contact with each other over the entire surface, the reaction proceeds over the entire electrode surface. As a result, the deterioration itself progresses almost uniformly over the entire surface, and the actual current density can also be kept low.
On the other hand, conventionally, as described above, the reaction proceeds only at contact areas such as peaks and convexities. As a result, the contact portion deteriorates faster than other portions and reaches the end of its life without making effective use of the entire surface of the electrode. In addition, the surface pressure in the contact area is higher than in other areas, and the thinning of the film is accelerated due to mechanical and chemical factors, so there is a risk of short-circuiting where the two electrodes come into contact with each other.
In this regard, in the embodiment described above, since the electrolyte membrane 11 and the hydrogen side current collector 12 are in pressure contact with each other over the entire surface, such a risk can be greatly suppressed.

Furthermore, in the hydrogen production cell 10 according to the embodiment described above, the amount of hydrogen existing in the cell during reaction can be extremely reduced, so even if hydrogen and oxygen mix due to membrane breakage or the like, the hydrogen used as fuel will not be absorbed. Since the amount is small, the possibility of combustion is extremely low.

By the way, when the electrode size is large, it is necessary to provide a plurality of communication ports 12d and 12g which function as manifolds for draining and exhausting water, that is, collecting and discharging moisture and hydrogen gas. This is because these reaction fluids flow inside the hydrogen side current collector 12, and the flow path resistance at that time is high. Furthermore, if the distance from the point where water or hydrogen is generated to the communication port is too long, force will be applied locally to the membrane, potentially causing deformation or damage to the membrane.

In order to suppress this, for example, as in the hydrogen side current collector 51 shown in FIG. With this shape, the distance from the location where hydrogen is generated to the communication ports 51d and 51g can be shortened. That is, the shortest distance from the location where hydrogen is generated to the closest communication ports 51d and 51g can be shortened. 1/2 of the distance L shown in FIG. 7 is the shortest distance. Incidentally, the length of the distance L suitable for the present invention is preferably 200 mm or less, for example, although it depends on the size of the entire electrode. In this case, the pressure loss is large on the raw water inlet side on the oxygen side and on the outlet side of the reaction fluid on the oxygen side, so as shown in FIG. 7, the oxygen side communication ports 51h and 51i are connected to the hydrogen side communication ports 51d and It is set larger than 51g.

Of course, if the electrode area is small, for example around 30 cm ² , the hydrogen side current collector 12 used in the hydrogen production cell 10 according to the previous embodiment shown in FIG. Two communication ports 12d and 12g located on the diagonal line of 12 are also sufficient.

Further, the hydrogen side current collector used in the present invention is preferably made of a material that easily absorbs generated water and hydrogen. This is because if the absorbency is poor, water and hydrogen will remain between the electrolyte membrane and the hydrogen side current collector, causing membrane deformation. Therefore, examples of materials suitable for the hydrogen side current collector used in the present invention include carbon paper and carbon nonwoven fabric.
Further, as the electrolyte membrane used in the present invention, a membrane whose size does not change as much as possible in a dry state and a wet state is suitable. This is to suppress the application of force locally. Therefore, from this point of view, examples of materials suitable for the electrolyte membrane of the present invention include fluorine-based electrolyte membranes, alkaline-based electrolyte membranes, hydrocarbon-based electrolyte membranes, and the like.

Furthermore, regarding the thickness of the hydrogen side current collector, the thicker it is, the lower the flow path resistance is, and the easier it is to absorb generated water and hydrogen. The thickness suitable for the present invention depends on the material constituting the hydrogen side current collector and the porosity, but for example, a thickness of about 0.2 mm to 2.0 mm is preferable.

Furthermore, the following inventions can also be proposed.
(1) An oxygen-side current collector and a hydrogen-side current collector are arranged on both sides of a solid polymer electrolyte with an electrode catalyst layer formed on both sides, and each outside of the oxygen-side current collector and hydrogen-side current collector A hydrogen production cell for producing hydrogen by water electrolysis, the hydrogen production cell having a configuration in which the oxygen side current collector and the hydrogen side current collector are sandwiched between arranged separators,
The hydrogen-side current collector has a large number of organically connected voids therein, and the surface of the separator disposed outside the hydrogen-side current collector on the hydrogen-side current collector side is flat. ,
It is confirmed that a dedicated flow path for recovering the reaction fluid generated during electrolysis is not formed between the separator disposed outside the hydrogen side current collector and the hydrogen side current collector. Features: Hydrogen production cell.
(2) The hydrogen production cell according to (1) above, wherein the hydrogen side current collector has a porosity of 50% to 99%.
(3) The hydrogen gas and water recovery portions generated from the hydrogen-side current collector are formed on a pair of opposing sides of the hydrogen-side current collector, as described in (1) above. Or the hydrogen production cell according to any one of (2).
(4) The hydrogen production cell according to (3) above, wherein a plurality of the recovery sections are formed on each of the opposing sides.
(5) The hydrogen-side current collector has a shape having a long side and a short side, and the recovery section is formed on each of the opposing long sides. ) or (4).
(6) A hydrogen production method using the hydrogen production cell according to any one of (1) to (5) above,
A method for producing hydrogen, comprising applying a voltage between the oxygen side current collector and the hydrogen side current collector to generate hydrogen gas from the hydrogen side current collector.

INDUSTRIAL APPLICATION This invention is useful for the hydrogen production cell which provides raw material water and generates hydrogen by electrolyzing the said raw material water.

1 Hydrogen production device 2, 3 End plate 4 Hydrogen production cell stack 5 DC power supply 10 Hydrogen production cell 11 Electrolyte membrane 11a Solid polymer membrane 11d to 11g Communication port 12 Hydrogen side current collector 12d, 12g Communication port 13 Oxygen side current collector Body 13e, 13f Communication port 14 Separator 14d to 14g Communication port 15 Channel forming plate 15b Channel 16 Separator 16d to 16g Communication port P1 Pure water inlet port P2 Pure water outlet port P3, P4 Hydrogen outlet port

Claims (1)

An oxygen-side current collector and a hydrogen-side current collector are arranged on both sides of a solid polymer electrolyte with an electrode catalyst layer formed on both sides, and separation is performed on the outside of each of the oxygen-side current collector and hydrogen-side current collector. A hydrogen production cell configured to sandwich the oxygen-side current collector and hydrogen-side current collector between the body and to produce hydrogen by water electrolysis,
The surface of the separator disposed outside the hydrogen side current collector on the hydrogen side current collector side is flat;
It is confirmed that a dedicated flow path for recovering the reaction fluid generated during electrolysis is not formed between the separator disposed outside the hydrogen side current collector and the hydrogen side current collector. Features: Hydrogen production cell.

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