JP2022108751A - electrochemical hydrogen pump - Google Patents

Abstract

To provide an electrochemical hydrogen pump capable of improving efficiency of hydrogen compression operation when the user starts the first use.SOLUTION: An electrochemical hydrogen pump 100 is provided with an electrolyte membrane 22 having a pair of main surfaces, a cathode catalyst layer 24 provided on one main surface of the electrolyte membrane, an anode catalyst layer 23 provided on the other main surface of the electrolyte membrane, and a voltage applicator 21 for applying a voltage between the cathode catalyst layer and the anode catalyst layer. By applying the voltage by the voltage applicator, hydrogen in a hydrogen-containing gas supplied on the anode catalyst layer is moved onto the cathode catalyst layer and the pressure is boosted. Before the user starts the first use, irregularity 200, 201 of the cross-sectional shape is larger in the anode catalyst layer than in the cathode catalyst layer.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to electrochemical hydrogen pumps.

In recent years, from the viewpoint of improving fuel efficiency and using carbon-free fuel, fuel cell vehicles that run by driving motors using electric power generated by fuel cells have attracted attention and have been put on the market. However, in order to popularize fuel cell vehicles, the challenge is how to prepare the infrastructure for supplying hydrogen, which is the fuel, and how many hydrogen stations can be installed throughout the country. Hydrogen stations have so far been used to purify and compress hydrogen using the pressure swing adsorption method (PSA), but the size of the equipment and the enormous installation costs are obstacles to the nationwide deployment of hydrogen stations. It has become.

In the coming hydrogen society, in addition to the production of hydrogen, there is a demand for technological development that can store hydrogen at high density and transport or use it in a small volume at low cost. In particular, it is necessary to improve the fuel supply infrastructure to promote the spread of fuel cells, which serve as a distributed energy source. In addition, various proposals have been made to purify and pressurize high-purity hydrogen in order to stably supply hydrogen to fuel supply infrastructure.

For example, Patent Literature 1 describes a hydrogen refining and boosting system that purifies and boosts hydrogen by applying a voltage between an anode and a cathode sandwiching an electrolyte membrane. Specifically, when an electric current flows between the anode and the cathode, the hydrogen at the anode becomes protons, and the protons move across the electrolyte membrane from the anode to the cathode, entraining water molecules. A laminated structure of an anode, an electrolyte membrane, and a cathode is referred to as a membrane electrode assembly (hereinafter referred to as MEA).

In addition, by applying a voltage between the anode and cathode of the MEA having a solid polymer electrolyte membrane and electrolyzing water supplied to the anode side, oxygen is produced on the anode side and hydrogen is produced on the cathode side. A hydrogen production apparatus has been proposed (see Patent Document 2, for example). This high-pressure hydrogen production apparatus is provided with a disc spring or a coil spring for bringing the cathode power feeder into close contact with the electrolyte membrane against deformation of the electrolyte membrane and the anode power feeder.

JP 2015-117139 A Japanese Patent Application Laid-Open No. 2006-70322

An object of the present disclosure is to provide, as an example, an electrochemical hydrogen pump that can improve the efficiency of the hydrogen compression operation more than before when a user starts using it for the first time.

An electrochemical hydrogen pump according to one aspect of the present disclosure includes an electrolyte membrane having a pair of main surfaces, a cathode catalyst layer provided on one main surface of the electrolyte membrane, and the other main surface of the electrolyte membrane. and a voltage applicator that applies a voltage between the cathode catalyst layer and the anode catalyst layer, and the voltage applicator applies the voltage to cause the anode catalyst layer to An electrochemical hydrogen pump that moves hydrogen in the hydrogen-containing gas supplied to the cathode catalyst layer and pressurizes it above the cathode catalyst layer before a user starts using it for the first time The anode catalyst layer has larger irregularities in cross-sectional shape.

The electrochemical hydrogen pump of one aspect of the present disclosure can produce an effect that the efficiency of the hydrogen compression operation can be improved more than before when the user starts using it for the first time.

FIG. 1 is a diagram showing an example of chemical potential of water in relation to relative humidity. FIG. 2 is a diagram showing an example of performance test results of a cell accompanying repeated hydrogen compression tests. FIG. 3A is a diagram showing an example of a cross section of a cell by electron microscope observation. FIG. 3B is a diagram showing an example of a cross section of a cell observed by an electron microscope. FIG. 3C is a diagram showing an example of a cross section of a cell obtained by electron microscope observation. FIG. 3D is a diagram showing an example of the surface of the catalyst layer observed with an electron microscope. FIG. 4 is a diagram showing an example of the electrochemical hydrogen pump of the first embodiment. FIG. 5 is a diagram showing an example of the electrochemical hydrogen pump of the example of the first embodiment. FIG. 6 is a diagram showing an example of the electrochemical hydrogen pump of the second embodiment.

From the viewpoint of reducing the dry-up of the electrolyte membrane and the flooding at the anode of the electrochemical hydrogen pump, a study was conducted to improve the efficiency of the hydrogen compression operation, and the following findings were obtained.

In the conventional example, from the viewpoint of improving the electrical contact between the catalyst layer of the electrochemical hydrogen pump and the power feeder, it has been studied to improve the efficiency of the hydrogen compression operation. It has not been considered to improve the efficiency of the hydrogen compression operation from the viewpoint of reducing the

When the electrochemical hydrogen pump is equipped with a solid polymer electrolyte membrane, pump performance ( Efficiency performance indexed by overvoltage) is affected.

Specifically, for example, when the electrolyte membrane of the electrochemical hydrogen pump lacks moisture, the proton conductivity of the electrolyte membrane decreases. As a result, the electric energy required for the hydrogen compression operation of the electrochemical hydrogen pump increases, and the efficiency of the hydrogen compression operation of the electrochemical hydrogen pump decreases.

Conversely, for example, if there is excess moisture in the anode of an electrochemical hydrogen pump, water vapor in the anode gas can condense, causing the condensed water to block (flood) the gas flow path of the electrochemical hydrogen pump. have a nature. As a result, the diffusivity of hydrogen in the anode may be hindered. In this case, the efficiency of the hydrogen compression operation of the electrochemical hydrogen pump is reduced due to the increased power required to operate the pump to ensure the desired proton transfer.

Here, during the hydrogen compression operation of the electrochemical hydrogen pump, the water that moves from the anode to the cathode accompanied by protons (electroosmosis) moves from the cathode to the anode due to the differential pressure generated by the electrochemical hydrogen pump (reverse osmosis). do. This often causes the above-mentioned flooding at the anode.

The former, water electroosmosis, occurs with proton conduction in the electrolyte membrane. The latter, water reverse osmosis, is caused by the difference in water chemical potential between the anode and cathode, which is dependent (eg proportional) on the differential pressure generated in the electrochemical hydrogen pump.

By the way, the chemical potential of water vapor under high pressure has not been reported to the present inventors' knowledge. For this reason, for example, the chemical potential of water (U _{liq — 338} ) at 65° C. and 20 MPaG is combined with the known chemical potential of water (U ⁰ _{liq —} 338 ) at 65° C. and normal pressure, according to Job G. et. al., Eur. J. Phys., 27 353 (2006)”, and from such water chemical potential (U _{liq_338} ), the water vapor potential at 65° C. and 20 MPaG based on known techniques. A chemical potential was calculated.
U _{liq_338} = U ⁰ _{liq_338} + δ × [P(z) - P _STD ]
In the above formula, δ is "1.990 J mol ⁻¹ atm ⁻¹ ", P(z) is the pressure applied to water, and P _STD is atmospheric pressure.

Then, taking the relative humidity (%) of water vapor as the horizontal axis and comparing the chemical potential of water vapor at 65°C and 20 MPaG with the chemical potential of water vapor at 65°C and normal pressure, these chemical potential diagrams (Fig. 1) are obtained. was taken.

In other words, the amount of water movement in the electrolyte membrane of the electrochemical hydrogen pump is determined by the electroosmotic water flux (j _EOD ) generated with the proton conduction of the electrolyte membrane in FIG. It is determined by the balance between the reverse osmosis water flux (j _P ) generated by the potential difference. In this case, even if the hydrogen-containing gas is supplied to the anode in a fully humidified (relative humidity: 100%) state, if the cathode is at a high pressure, until the chemical potential of water between the anode and the cathode becomes equal, The reverse osmosis driving force of water acts on the electrolyte membrane in the direction in which the relative humidity of the hydrogen-containing gas decreases. For example, in the example shown in FIG. 1, the reverse osmosis driving force of water acts on the electrolyte membrane until the relative humidity at the cathode of 20 MPaG reaches H. It increases with increasing pressure.

Here, it is assumed that the electroosmotic water flux (j _EOD ) generated by proton conduction in the electrolyte membrane does not depend on the differential pressure generated by the electrochemical hydrogen pump. Then, when the flux of electroosmotic water (j _EOD ) and the flux of reverse osmosis water (j _P ) are in conflict, for example, in the hydrogen compression operation of an electrochemical hydrogen pump, when the cathode pressure is low, The amount of water present at the cathode (hereinafter referred to as cathode water amount) is greater than the amount of water present at the anode (hereinafter referred to as anode water amount) (cathode water amount>anode water amount), and at high pressures, the cathode water amount is greater than the anode water amount. may also decrease (cathode water content < anode water content).

In general, the electroosmotic water flux (j _EOD ) does not depend on the thickness of the electrolyte membrane, but the reverse osmosis water flux (j _P ) increases as the electrolyte membrane thickness decreases. The pressure at which the above reversal phenomenon occurs between the water amount and the anode water amount decreases as the thickness of the electrolyte membrane becomes thinner.

It is considered that the above-described reversal phenomenon can be one of the causes of dry-up of the electrolyte membrane on the cathode side, for example. It is also believed that, for example, it can be a factor in flooding at the anode.

Therefore, in order to confirm the above problem of the electrochemical hydrogen pump, the present inventors conducted a performance test of the hydrogen compression operation of the electrochemical hydrogen pump using the following test equipment, and from the test results, the following phenomenon I found

<Test equipment>
The test device comprises an electrolyte membrane, a catalyst layer, a microporous layer and a gas diffusion layer laminated on each side of the electrolyte membrane, and a voltage applicator. The laminate of the electrolyte membrane, catalyst layer, microporous layer and gas diffusion layer corresponds to the cell of the electrochemical hydrogen pump. Also, the high voltage side region of the cell corresponds to the cathode, and the low voltage side region of the cell corresponds to the anode.

As the electrolyte membrane, a commercially available fluorine-based polymer electrolyte membrane having a thickness of about 50 μm was used.

Both the cathode and the anode used catalyst layers having the same cross-sectional shape, and 0.3 mg/cm ² of platinum was used as the catalyst metal for these catalyst layers.

Water-repellent carbon felt was used as the gas diffusion layer of the cathode.

A water-repellent sintered titanium powder was used as the gas diffusion layer of the anode.

The voltage applicator is a device that applies a voltage between the anode and cathode of the cell. Also, the microporous layer is a water-repellent layer containing a water-repellent material (eg, PTFE) and carbon black. For convenience, the microporous layer on the anode side will be referred to as the first microporous layer, and the microporous layer on the cathode side will be referred to as the second microporous layer.

<Test procedure>
First, the temperature of the cell was set to about 65° C., and a fully humidified hydrogen-containing gas with a relative humidity of about 100% was supplied to the anode. Then, with the cathode open (at normal pressure), the voltage applicator was controlled so that a constant current of 1 A/cm ² in terms of current density flows between the anode and the cathode, and the electrolyte membrane was fully expanded overnight. Humidified.

Next, the temperature of the cell was set to 50°C and a hydrogen-containing gas with a dew point of 55°C was supplied to the anode. Then, by controlling the voltage applicator so that a constant current of 1 A/cm ² in terms of current density flows between the anode and the cathode, about 70% of the hydrogen in the hydrogen-containing gas supplied to the anode is transferred to the cathode. Under moving conditions, the cathode was switched from an open state to a sealed state, and a hydrogen compression operation of the cell (hereinafter referred to as a hydrogen compression test) was performed until the cathode gas pressure reached 40 MPa. Such hydrogen compression tests were repeated multiple times with reopening and resealing of the cathode, resulting in the test results of FIG.

When the cell overvoltage reached a predetermined threshold (here, 0.5 V), the continuation of the hydrogen compression operation was stopped, and then the next hydrogen compression test was performed.

<Test results>
FIG. 2 is a diagram showing an example of the performance test results of the cell accompanying repetition of the hydrogen compression test. The vertical axis on the right side of FIG. 2 indicates the resistance (mΩ) of the cell, and the vertical axis on the left side indicates the overvoltage (V) of the cell. The horizontal axis of FIG. 2 represents the number of hydrogen compression tests.

FIG. 2 shows the cell resistance (dotted line) in the cathode high pressure state (40 MPaG) after the fourth hydrogen compression test, and the cell overvoltage (white rhombus) for each number of hydrogen compression tests in the same state is plotted. It is As a comparative example, the cell resistance (solid line) with the cathode open (at normal pressure) is shown, and the cell overvoltage (black diamonds) for each number of hydrogen compression tests in the same state is plotted.

As shown in FIG. 2, until the third hydrogen compression test, the cell resistance and overvoltage were not measured when the cathode was in a high pressure state (40 MPaG). This is because the cell overvoltage reached the threshold (0.5 V) before the cathode gas pressure reached 40 MPaG. Specifically, for the first and second hydrogen compression tests, the cell resistance and overvoltage were 6.6 mΩ and 0.5 V, respectively, at a cathode gas pressure of 38 MPaG. When the hydrogen compression test was performed for the third time, the cell resistance and overvoltage were 4.9 mΩ and 0.5 V, respectively, at a cathode gas pressure of 34 MPaG.

However, after the fourth hydrogen compression test, even when the cathode gas pressure reached 40 MPaG, the overvoltage of the cell fell below the predetermined threshold value (0.5 V). Specifically, for example, in the case of the fourth hydrogen compression test, as shown in FIG. 2, the cell resistance and overvoltage were 4.0 mΩ and 0.35 V at a cathode gas pressure of 40 MPaG, respectively. After that, as the number of hydrogen compression tests increased up to eight times, the cell resistance and overvoltage tended to decrease.

On the other hand, the resistance of the cell with the cathode open (at normal pressure) remained at a low value of about 2.1 mΩ from the 1st to 8th hydrogen compression tests, and the cathode was open (normal pressure). The overvoltage of the cell at normal pressure showed a slight upward trend from 0.119 V in the first hydrogen compression test as the number of hydrogen compression tests increased.

From the above test results, the present inventors have found that the decrease in the overvoltage of the cell in increasing the cathode pressure accompanying the increase in the number of hydrogen compression tests between the 4th and 8th times (hereinafter, the increase in the number of hydrogen compression tests) is Since the decrease in resistance also occurred, it was surmised that dry-up of the electrolyte membrane was suppressed as the hydrogen compression test was repeated between the 4th and 8th times. In other words, the resistance of the electrolyte membrane, which is directly linked to the cell resistance, correlates with the wet state of the electrolyte membrane, and the decrease in cell resistance is thought to be due to the improvement in the wet state of the electrolyte membrane. For this reason, even though the electrolyte membrane was sufficiently humidified before the hydrogen compression test, the cell resistance decreased when the hydrogen compression test was performed. It was surmised that this was because the electrolyte membrane dried up. However, assuming such a conjecture, it is necessary to further investigate why the dry-up of the electrolyte membrane is suppressed as the hydrogen compression test is repeated between the 4th and 8th times. .

It should be noted that the slight increase in the overvoltage of the cell at normal cathode pressure is not accompanied by a change in the cell resistance, so it is considered that, for example, deterioration of the microporous layer is a factor.

<Electron microscope observation of cell cross section>
Therefore, in order to investigate the cause of the decrease in the cell overvoltage due to the increase in the number of hydrogen compression tests, another cell with the same structure was used to conduct four hydrogen compression tests in the same manner as described above. and the surface of the catalyst layer were observed with an electron microscope.

FIGS. 3A, 3B, and 3C are diagrams replicating an example of a cell cross section observed by an electron microscope. FIG. 3A shows a cross-sectional representation of both the anode catalyst layer and the cathode catalyst layer of the cell by electron microscopy, the magnification of the electron microscopy in FIG. It can be understood from FIGS. 3B and 3C respectively show cross-sections of the cathode catalyst layer and anode catalyst layer of the cell observed by electron microscopy, and the magnifications of the electron microscopy observations in FIGS. It can be understood from the fact that the dimension L is approximately 15 μm.

Although the cross-sectional shapes of the cathode catalyst layer and the anode catalyst layer were similar before the hydrogen compression test, when the hydrogen compression test was performed, the cross-sectional shape of the cathode catalyst layer in FIGS. and the cross-sectional shape of the anode catalyst layer are clearly different. This is also verified by the surface roughness measurement of the cathode catalyst layer and the anode catalyst layer.

Specifically, for example, at a magnification of 2000 times, the surface of the cathode catalyst layer in contact with the second microporous layer and the surface of the cathode catalyst layer in contact with the electrolyte membrane are observed over 120 μm, respectively. When the surface roughness (Rz) was determined, the surface roughness of the former was 2.9 μm and the surface roughness of the latter was 1.2 μm.

On the other hand, for example, at a magnification of 1000 times, the surface of the anode catalyst layer in contact with the first microporous layer and the surface of the anode catalyst layer in contact with the electrolyte membrane are each observed over 240 μm. When the surface roughness (Rz) of the former was determined, the surface roughness of the former was 10.0 µm and the surface roughness of the latter was 11.3 µm.

It is considered that the unevenness provided on the cathode catalyst layer and the anode catalyst layer is caused by the differential pressure (high pressure) generated in the cell being applied to the anode catalyst layer via the electrolyte membrane. Such a phenomenon may be one of the factors that reduce the overvoltage of the cell when the cathode voltage is increased as the number of hydrogen compression tests increases. In other words, the present inventors have found that the unevenness of the cross-sectional shape of the anode catalyst layer, which is larger than the unevenness of the cross-sectional shape of the cathode catalyst layer, exerts an advantageous effect in, for example, suppressing dry-up of the electrolyte membrane. It is speculated that

That is, the electrochemical hydrogen pump of the first aspect of the present disclosure includes an electrolyte membrane including a pair of main surfaces, a cathode catalyst layer provided on one main surface of the electrolyte membrane, and a cathode catalyst layer provided on the other main surface of the electrolyte membrane. and a voltage applicator that applies a voltage between the cathode catalyst layer and the anode catalyst layer, and the voltage applicator applies the above voltage to cause the hydrogen supplied onto the anode catalyst layer A device for moving hydrogen in a contained gas onto a cathode catalyst layer and pressurizing it, wherein the cross-sectional shape of the anode catalyst layer is greater than that of the cathode catalyst layer before the user starts using it for the first time. Unevenness is large.

According to such a configuration, the electrochemical hydrogen pump of this aspect can improve the efficiency of the hydrogen compression operation more than before when the user starts using it for the first time.

For example, when the electrochemical hydrogen pump is operated to compress hydrogen before the user starts using it for the first time, the differential pressure (high pressure) generated by the electrochemical hydrogen pump changes the unevenness of the cross-sectional shape of the anode catalyst layer to that of the cathode catalyst. It can be larger than the unevenness of the cross-sectional shape of the layer. Then, for example, it is inferred that the anode catalyst layer is more susceptible to cracking than the cathode catalyst layer. Here, when a hydrogen-containing gas in a highly humidified state is supplied to the anode catalyst layer, due to the presence of cracks in the anode catalyst layer, the cracks in the anode catalyst layer are more likely to occur than when the anode catalyst layer is flat and has few cracks. As a result, moisture in the hydrogen-containing gas is easily supplied to the electrolyte membrane. As a result, by performing the hydrogen compression operation of the electrochemical hydrogen pump before the user starts using it for the first time, the electrolyte membrane of the electrochemical hydrogen pump can be dried up when the user starts using it for the first time. It is thought that it becomes possible to suppress it.

As shown in FIG. 3C, since the main surface of the first microporous layer (water-repellent layer) and the main surface of the anode catalyst layer are in close contact, the main surface of the first microporous layer on the anode catalyst layer side has , unevenness is formed along the cross-sectional unevenness of the anode catalyst layer.

In addition, as shown in FIG. 3B, since the main surface of the second microporous layer (water-repellent layer) and the main surface of the cathode catalyst layer are in close contact, the main surface of the second microporous layer on the cathode catalyst layer side is formed with unevenness along the cross-sectional unevenness of the cathode catalyst layer.

Since the unevenness of the cross-sectional shape of the anode catalyst layer is larger than the unevenness of the cross-sectional shape of the cathode catalyst layer, the unevenness of the main surface of the first microporous layer on the anode catalyst layer side is the same as that of the cathode catalyst layer of the second microporous layer. larger than the unevenness of the main surface of the side. This is also verified by surface roughness measurements of these microporous layers.

Specifically, for example, the surface roughness (Rz) of the second microporous layer on the cathode catalyst layer side was observed over 120 μm at a magnification of 2000, and the surface roughness (Rz) was determined. was 2.9 μm.

On the other hand, for example, the surface roughness (Rz) of the first microporous layer on the anode catalyst layer side was observed over 240 μm at a magnification of 1000 times to obtain the surface roughness (Rz). was 10.0 μm.

It is considered that the unevenness provided on the main surface of the first microporous layer is caused by the differential pressure (high pressure) generated in the cell being applied to the anode catalyst layer via the electrolyte membrane. Such a phenomenon may be one of the factors that reduce the overvoltage of the cell when the cathode voltage is increased as the number of hydrogen compression tests increases. In other words, the present inventors have found that providing unevenness along the unevenness of the anode catalyst layer on the main surface of the first microporous layer on the anode catalyst layer side is advantageous, for example, in suppressing dry-up of the electrolyte membrane. It is speculated that it is exerting its action and effect. Further, by making the unevenness of the main surface of the first microporous layer on the anode catalyst layer side larger than the unevenness of the main surface of the second microporous layer on the cathode catalyst layer side, for example, dry-up of the electrolyte membrane can be suppressed. It is surmised that it exerts an advantageous effect on

That is, the electrochemical hydrogen pump of the second aspect of the present disclosure is the electrochemical hydrogen pump of the first aspect, including a first water-repellent layer containing a water-repellent material provided on the anode catalyst layer; The main surface of the water layer on the anode catalyst layer side may have unevenness along the unevenness of the anode catalyst layer. Further, the electrochemical hydrogen pump of the third aspect of the present disclosure is the electrochemical hydrogen pump of the second aspect, further comprising a second water-repellent layer containing a water-repellent material provided on the cathode catalyst layer, the first repellent The major surface of the water layer on the anode catalyst layer side may be more uneven than the major surface of the second water-repellent layer on the cathode catalyst layer side.

According to such a configuration, the electrochemical hydrogen pump of this aspect can improve the efficiency of the hydrogen compression operation more than before when the user starts using it for the first time.

For example, when the electrochemical hydrogen pump performs a hydrogen compression operation before the user starts using it for the first time, the differential pressure (high pressure) generated by the electrochemical hydrogen pump causes the first water-repellent layer to move toward the anode catalyst layer. The main surface of is provided with irregularities along the irregularities of the anode catalyst layer. In this case, it is presumed that cracks are more likely to occur in the first water-repellent layer than in the second water-repellent layer due to the size relationship between the unevenness of the first water-repellent layer and the second water-repellent layer. Then, in the first water-repellent layer, inflow and outflow of water between both main surfaces of the first water-repellent layer in the anode is facilitated through cracks in the first water-repellent layer more easily than in the second water-repellent layer. As a result, by performing the hydrogen compression operation of the electrochemical hydrogen pump before the user starts using it for the first time, the electrolyte membrane of the electrochemical hydrogen pump can be dried up when the user starts using it for the first time. It is thought that it becomes possible to suppress it.

It should be noted that the higher the differential pressure generated by the electrochemical hydrogen pump, the greater the reverse osmosis water flux (j _P ) that moves from the cathode to the anode. Therefore, as the hydrogen compression operation of the electrochemical hydrogen pump progresses, the amount of moisture present at the anode may become greater than that present at the cathode. Then, flooding of the anode is likely to occur due to reverse osmosis water to the anode. If the diffusibility of hydrogen is hindered at the anode due to the occurrence of such flooding, the diffusion resistance of the electrochemical hydrogen pump may increase, so the efficiency of the hydrogen compression operation of the electrochemical hydrogen pump is likely to decline.

Therefore, in the electrochemical hydrogen pump of this aspect, the occurrence of flooding at the anode is suppressed by providing the first water-repellent layer on the anode catalyst layer. Specifically, for example, in the first water-repellent layer, water existing in the anode tends to move out of the anode together with the hydrogen-containing gas due to the flow of the hydrogen-containing gas in the anode.

Conversely, the lower the differential pressure generated by the electrochemical hydrogen pump, the smaller the reverse osmosis water flux (j _P ) that moves from the cathode to the anode. The amount of moisture present in the anode can be large compared to the moisture present in the anode. As a result, condensed water tends to be generated from the hydrogen-containing gas at the cathode, and this condensed water moves from the cathode to the anode via the electrolyte membrane.

Therefore, in the electrochemical hydrogen pump of this aspect, by providing the second water-repellent layer on the cathode catalyst layer, even if the differential pressure generated by the electrochemical hydrogen pump increases, the water-repellent layer exists outside the second water-repellent layer. It is thought that the movement of the condensed water to the electrolyte membrane can be appropriately suppressed. The outside of the second water-repellent layer corresponds to the opposite side when the cathode catalyst layer side is the inside of the second water-repellent layer with respect to the second water-repellent layer.

As described above, the electrochemical hydrogen pump of this aspect can improve the state in which excess water stays in the anode, and can appropriately suppress the occurrence of flooding in the anode.

By the way, before the hydrogen compression test was performed, the thickness of the cathode catalyst layer and the anode catalyst layer were about the same (both thicknesses are between about 7 μm and 10 μm), but the hydrogen compression test was performed. 3B and 3C, the thickness of the cathode catalyst layer and the thickness of the anode catalyst layer are clearly different. This has also been verified by measuring the thickness of the cathode catalyst layer and the anode catalyst layer.

Specifically, the thickness of the cathode catalyst layer was 7.0 μm in the thin film portion and 9.9 μm in the thick film portion.

On the other hand, the thickness of the anode catalyst layer was 4.5 μm in the thin film portion and 6.7 μm in the thick film portion.

In addition, although the porosities of the cathode catalyst layer and the anode catalyst layer were about the same before the hydrogen compression test, when the hydrogen compression test was performed, the surface of the cathode catalyst layer was observed with an electron microscope (Fig. 3D (a)) and the electron microscope observation of the surface of the anode catalyst layer (see FIG. 3D (b)), there is a clear difference between the porosity of the anode catalyst layer and the cathode catalyst layer. Note that the magnification of the electron microscope observation in FIG. 3D can be grasped from the fact that the dimension L in the figure is about 600 nm.

The above has also been verified in porosity measurements of the cathode catalyst layer and the anode catalyst layer.

Specifically, for example, by observing the surface of the cathode catalyst layer at a magnification of 100,000 times, the porosity of the cathode catalyst layer composed of pores of several to several hundred nanometers (here, with an electron microscope The ratio of the cross section of the void portion obtained from the photograph of the cross section;

On the other hand, when the porosity of the anode catalyst layer was determined by observing the surface of the anode catalyst layer at a magnification of 100,000 times, the porosity was about 14%.

The difference between the porosity of the anode catalyst layer and the porosity of the cathode catalyst layer is that the differential pressure (high pressure) generated in the cell is applied to the anode catalyst layer through the electrolyte membrane. It is thought that it is generated in the process of thinning. In other words, it is thought that when the thickness of the anode catalyst layer is reduced, the voids in the anode catalyst layer are crushed and the porosity of the anode catalyst layer is reduced. Such a phenomenon may be one of the factors that reduce the overvoltage of the cell when the cathode voltage is increased as the number of hydrogen compression tests increases. In other words, the present inventors believe that making the porosity of the anode catalyst layer smaller than the porosity of the cathode catalyst layer exhibits an advantageous effect, for example, in suppressing dry-up of the electrolyte membrane. I'm guessing not.

That is, in the electrochemical hydrogen pump of the fourth aspect of the present disclosure, the anode catalyst layer may be thinner than the cathode catalyst layer in any one of the first to third aspects of the electrochemical hydrogen pump. Further, in the electrochemical hydrogen pump of the fifth aspect of the present disclosure, in the electrochemical hydrogen pump of any one of the first to fourth aspects, the anode catalyst layer may have a lower porosity than the cathode catalyst layer.

For example, when the electrochemical hydrogen pump is operated to compress hydrogen before the user starts using it for the first time, the differential pressure (high pressure) generated by the electrochemical hydrogen pump reduces the thickness of the anode catalyst layer to the thickness of the cathode catalyst layer. can be thinner than Then, it is considered that the voids of the anode catalyst layer are crushed in the process of decreasing the thickness of the anode catalyst layer, and the porosity of the anode catalyst layer becomes smaller. The smaller the porosity of the anode catalyst layer, the smaller the water content in the anode catalyst layer, but the smaller the diameter of the pores that form the pores of the anode catalyst layer. When the diameter of the pores forming the voids of the anode catalyst layer is small, the force of retaining water in the pores is stronger than when the diameter is large. Thereby, water can be appropriately retained in the pores of the anode catalyst layer near the electrolyte membrane. Therefore, by performing the hydrogen compression operation of the electrochemical hydrogen pump before the user starts using it for the first time, drying up of the electrolyte membrane of the electrochemical hydrogen pump when the user starts using it for the first time is suppressed. It is thought that it will be possible to

As shown in FIG. 3B, since the main surface of the cathode catalyst layer and the main surface of the electrolyte membrane are in close contact with each other, the main surface of the electrolyte membrane on the cathode catalyst layer side has irregularities along the cross-sectional shape of the cathode catalyst layer. unevenness is formed. Further, as shown in FIG. 3C, since the main surface of the anode catalyst layer and the main surface of the electrolyte membrane are in close contact with each other, the main surface of the electrolyte membrane on the anode catalyst layer side has unevenness corresponding to the cross-sectional shape of the anode catalyst layer. Concavities and convexities are formed along the Since the unevenness of the cross-sectional shape of the anode catalyst layer is larger than the unevenness of the cross-sectional shape of the cathode catalyst layer, the unevenness of the main surface of the electrolyte membrane on the anode catalyst layer side is the same as the unevenness of the main surface of the electrolyte membrane on the cathode catalyst layer side. bigger than This is also verified in the surface roughness measurement described above. That is, the surface roughness of the former electrolyte membrane can be assumed to be 11.3 μm, and the surface roughness of the latter electrolyte membrane can be assumed to be 1.2 μm.

It is considered that the unevenness provided on the pair of main surfaces of the electrolyte membrane is caused by the differential pressure generated in the cell being applied to the anode catalyst layer via the electrolyte membrane. Such a phenomenon is presumed to be accompanied by pore shrinkage in the electrolyte membrane, and this may be one of the factors that reduce the overvoltage of the cell when the cathode pressure is increased as the number of hydrogen compression tests increases. There is In other words, the present inventors have found that making the unevenness of the main surface of the electrolyte membrane on the anode catalyst layer side larger than the unevenness on the main surface of the electrolyte membrane on the cathode catalyst layer side, for example, suppresses dry-up of the electrolyte membrane. It is speculated that it exerts an advantageous action and effect against it.

That is, the electrochemical hydrogen pump of the sixth aspect of the present disclosure is the electrochemical hydrogen pump of any one of the first to fifth aspects, wherein the electrolyte membrane is located on the anode catalyst layer side rather than the cathode catalyst layer side main surface. The main surface may have larger unevenness.

For example, when the electrochemical hydrogen pump performs a hydrogen compression operation before the user starts using it for the first time, the pressure difference (high pressure) generated by the electrochemical hydrogen pump causes the pressure difference between the two main surfaces of the electrolyte membrane to The pores in the electrolyte membrane can be appropriately shrunk when the unevenness is formed in the size relationship described above. As a result, the amount of reverse osmosis water that moves from the cathode catalyst layer to the anode catalyst layer due to the differential pressure generated by the electrochemical hydrogen pump can be suppressed, and water can be appropriately retained within the pores of the electrolyte membrane. can be done. Therefore, by performing the hydrogen compression operation of the electrochemical hydrogen pump before the user starts using it for the first time, drying up of the electrolyte membrane of the electrochemical hydrogen pump when the user starts using it for the first time is suppressed. It is thought that it will be possible to

In the electrochemical hydrogen pump of the seventh aspect of the present disclosure, in the electrochemical hydrogen pump of any one of the first to sixth aspects, the electrolyte membrane, the cathode catalyst layer and the anode catalyst are added to the electrochemical hydrogen pump before the user starts using it for the first time. A cell containing the layer may retain moisture at or above the moisture content in an 80% relative humidity atmosphere at the temperature of the cell during the hydrogen compression operation of the electrochemical hydrogen pump.

As described above, the electrochemical hydrogen pump of this embodiment can retain moisture in the cell at a water content equal to or higher than the above water content when the electrochemical hydrogen pump performs the hydrogen compression operation before the user starts using it for the first time. As a result, the electrolyte membrane can be sufficiently humidified by performing the hydrogen compression operation of the electrochemical hydrogen pump before the user starts using it for the first time. It is possible to appropriately suppress dry-up of the electrolyte membrane of the electrochemical hydrogen pump.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that each of the embodiments described below is an example of each of the aspects described above. Therefore, the shapes, materials, components, and arrangement positions and connection forms of the components shown below are merely examples, and do not limit each of the above aspects unless stated in the claims. . In addition, among the following constituent elements, constituent elements that are not described in independent claims representing the top concept of each of the above aspects will be described as optional constituent elements. Further, in the drawings, the description of the components with the same reference numerals may be omitted. The drawings schematically show each component for easy understanding, and the shape and dimensional ratio may not be exact representations.

(First embodiment)
[Device configuration]
FIG. 4 is a diagram showing an example of the electrochemical hydrogen pump of the first embodiment.

In the example shown in FIG. 4, the electrochemical hydrogen pump 100 includes an electrolyte membrane 22, an anode catalyst layer 23, a cathode catalyst layer 24, and a voltage applicator 21. In the electrochemical hydrogen pump 100 of this embodiment, the anode (electrode) of the electrochemical hydrogen pump 100 is composed of the anode catalyst layer 23 and the anode gas diffusion layer (not shown in FIG. 4). The cathode (electrode) of the electrochemical hydrogen pump 100 is composed of a cathode catalyst layer 24 and a cathode gas diffusion layer (not shown in FIG. 4).

The electrolyte membrane 22 is a polymer membrane having a pair of main surfaces and having proton (H ⁺ ) conductivity. The electrolyte membrane 22 may have any structure as long as it is a polymer membrane having such proton conductivity. For example, the electrolyte membrane 22 may be a fluoropolymer electrolyte membrane. Specifically, for example, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), or the like can be used as the electrolyte membrane 22, but the electrolyte membrane 22 is not limited thereto.

Cathode catalyst layer 24 is provided on one main surface of electrolyte membrane 22 . The cathode catalyst layer 24 may contain, for example, Pt or the like as a catalyst metal, but is not limited to this.

The anode catalyst layer 23 is provided on the other main surface of the electrolyte membrane 22 . The anode catalyst layer 23 may contain, for example, platinum (Pt) as a catalyst metal, but is not limited to this.

There are various methods for preparing catalysts for both the cathode catalyst layer 24 and the anode catalyst layer 23, and there is no particular limitation. Examples of catalyst carriers include conductive oxide powders and carbon-based powders. Examples of carbon-based powders include powders of graphite, carbon black, activated carbon having electrical conductivity, and the like. The method of supporting platinum or other catalytic metals on a carrier such as carbon is not particularly limited. For example, methods such as powder mixing or liquid phase mixing may be used. As the latter liquid phase mixing, for example, a method of dispersing a carrier such as carbon in a catalyst component colloidal liquid and adsorbing the carrier can be used. The state in which the catalyst metal such as platinum is supported on the carrier is not particularly limited. For example, the catalyst metal may be finely divided and supported on a carrier in a highly dispersed state.

The voltage applicator 21 is a device that applies voltage between the anode catalyst layer 23 and the cathode catalyst layer 24 .

Specifically, a high potential of the voltage applicator 21 is applied to the anode catalyst layer 23 and a low potential of the voltage applicator 21 is applied to the cathode catalyst layer 24 . The voltage applicator 21 may have any configuration as long as it can apply a voltage between the anode catalyst layer 23 and the cathode catalyst layer 24 . For example, voltage applicator 21 may be a device that adjusts the voltage applied between anode catalyst layer 23 and cathode catalyst layer 24 . Specifically, the voltage applicator 21 includes a DC/DC converter when connected to a DC power supply such as a battery, a solar battery, or a fuel cell, and a DC/DC converter when connected to an AC power supply such as a commercial power supply. , with an AC/DC converter.

In addition, the voltage applicator 21, for example, applies voltage between the anode catalyst layer 23 and the cathode catalyst layer 24 so that the power supplied to the electrochemical hydrogen pump 100 becomes a predetermined set value. It may be a power type power source in which the current flowing between the cathode catalyst layers 24 is regulated.

As described above, the electrochemical hydrogen pump 100 moves hydrogen in the hydrogen-containing gas supplied onto the anode catalyst layer 23 onto the cathode catalyst layer 24 by the voltage applicator 21 applying the voltage. , and boosts the pressure. The hydrogen-containing gas may be, for example, hydrogen gas generated by electrolysis of water, or reformed gas containing hydrogen.

As shown in FIG. 4 , in the electrochemical hydrogen pump 100 of the present embodiment, before the user starts using it for the first time, the anode catalyst layer 23 has a larger cross-sectional unevenness than the cathode catalyst layer 24 . . Also, the anode catalyst layer 23 is thinner than the cathode catalyst layer 24 . Also, the anode catalyst layer 23 has a smaller porosity than the cathode catalyst layer 24 . The main surface of the electrolyte membrane 22 on the anode catalyst layer 23 side is more uneven than the main surface on the cathode catalyst layer 24 side.

The configuration of the electrochemical hydrogen pump 100 described above is realized, for example, by performing a hydrogen compression operation (hereinafter referred to as a test run) of the electrochemical hydrogen pump 100 before the user starts using it for the first time. The user's first use refers to the first hydrogen compression operation of the electrochemical hydrogen pump 100 performed by the user after the electrochemical hydrogen pump 100 is shipped from the business to the user.

For example, as can be seen from the electron microscope observation of the cross section of the cell described above, before the test operation of the electrochemical hydrogen pump 100 is performed, although the cross-sectional shapes of the cathode catalyst layer 24 and the anode catalyst layer 23 are approximately the same, First, by performing a test run, the cross-sectional unevenness 200 of the anode catalyst layer 23 becomes larger than the cross-sectional unevenness 201 of the cathode catalyst layer 24 . In addition, although the thicknesses of the cathode catalyst layer 24 and the anode catalyst layer 23 were approximately the same before the test run, the thickness TA of the anode catalyst layer 23 was changed to that of the cathode catalyst layer 24 by performing the test run. becomes thinner than the thickness TC. In addition, although the porosities of the cathode catalyst layer 24 and the anode catalyst layer 23 were approximately the same before the test run, the porosity of the anode catalyst layer 23 decreased after the test run. 24 porosity.

At this time, since the main surface of the cathode catalyst layer 24 and the main surface of the electrolyte membrane 22 are in close contact with each other, the main surface of the electrolyte membrane 22 on the cathode catalyst layer side has unevenness corresponding to the cross-sectional shape of the cathode catalyst layer 24 . Concavities and convexities along 201 are formed. In addition, since the main surface of the anode catalyst layer 23 and the main surface of the electrolyte membrane 22 are in close contact with each other, the main surface of the electrolyte membrane 22 on the anode catalyst layer 23 side has the unevenness 200 of the cross-sectional shape of the anode catalyst layer 23 . Concavities and convexities along the groove are formed.

[motion]
The hydrogen compression operation of the electrochemical hydrogen pump 100 will be described below with reference to FIG. The following operations may be performed by, for example, a control program stored in a memory circuit of the controller by an arithmetic circuit (not shown) of the controller. However, it is not essential that the controller perform the following operations. The operator may perform some of the operations.

In the electrochemical hydrogen pump 100 of this embodiment, the hydrogen compression operation of the electrochemical hydrogen pump 100 is performed as a test run as follows, for example, before the user starts using it for the first time.

First, hydrogen-containing gas is supplied to the anode of the electrochemical hydrogen pump 100 , and electric power from the voltage applicator 21 is supplied between the anode catalyst layer 23 and the cathode catalyst layer 24 of the electrochemical hydrogen pump 100 .

Then, in the anode catalyst layer 23 of the electrochemical hydrogen pump 100, hydrogen (H ₂ ) in the hydrogen-containing gas is separated into hydrogen ions (protons) and electrons by an oxidation reaction (formula (1)). The protons are conducted through the electrolyte membrane 22 and move to the cathode catalyst layer 24, as shown in FIG. Electrons move to the cathode catalyst layer 24 through the voltage applicator 21 . Then, in the cathode catalyst layer 24, hydrogen molecules are generated again by a reduction reaction (equation (2)).

At this time, it is known that when the protons conduct through the electrolyte membrane 22, a predetermined amount of water moves from the anode to the cathode together with the protons as electroosmotic water.

Anode: H ₂ (low pressure) → 2H ⁺ +2e ^- (1)
Cathode: 2H ⁺ +2e ⁻ →H ₂ (high voltage) (2)
Here, the electrochemical hydrogen pump 100 is provided with a gas lead-out path (not shown) for leading out the hydrogen produced at the cathode to the outside of the cathode. Hydrogen at the cathode can be boosted to a high pressure by increasing the pressure drop of . Examples of flow rate regulators include a back pressure valve, a regulation valve, and the like provided in the gas lead-out path.

During the hydrogen compression operation of the electrochemical hydrogen pump 100, the electroosmotic water that has moved from the anode to the cathode along with the protons in the electrolyte membrane 22 in the electrochemical hydrogen pump 100 is generated in the electrochemical hydrogen pump 100. Pressure moves from the cathode to the anode (reverse osmosis).

As described above, the electrochemical hydrogen pump 100 of this embodiment can improve the efficiency of the hydrogen compression operation more than before when the user starts using it for the first time.

For example, when the electrochemical hydrogen pump 100 is trial run before the user starts using it for the first time, the unevenness 200 of the cross-sectional shape of the anode catalyst layer 23 is caused by the differential pressure (high pressure) generated by the electrochemical hydrogen pump 100. It can be made larger than the unevenness 201 of the cross-sectional shape of the cathode catalyst layer 24 . Then, for example, the anode catalyst layer 23 is presumed to crack more easily than the cathode catalyst layer 24 . Here, when a highly humidified hydrogen-containing gas is supplied to the anode of the electrochemical hydrogen pump 100, due to the presence of cracks in the anode catalyst layer 23, the anode catalyst layer 23 is flat and has few cracks. Moisture in the hydrogen-containing gas is easily supplied to the electrolyte membrane 22 through the cracks in the catalyst layer 23 . As a result, by performing a test run of the electrochemical hydrogen pump 100 before the user starts using it for the first time, the electrolyte membrane 22 of the electrochemical hydrogen pump 100 is dried up when the user starts using it for the first time. can be suppressed.

Further, for example, when the user performs a test run of the electrochemical hydrogen pump 100 before starting use for the first time, the thickness TA of the anode catalyst layer 23 increases due to the differential pressure (high pressure) generated by the electrochemical hydrogen pump 100. It can be thinner than the thickness TC of the catalyst layer 24 . Then, it is considered that the voids of the anode catalyst layer 23 are crushed in the process of decreasing the thickness TA of the anode catalyst layer 23, and the porosity of the anode catalyst layer 23 is decreased. As the porosity of the anode catalyst layer 23 decreases, the water content in the anode catalyst layer 23 decreases, but the diameter of the pores forming the pores of the anode catalyst layer 23 can be reduced. When the diameter of the pores forming the voids of the anode catalyst layer 23 is small, the force of retaining water in the pores is stronger than when the diameter is large. Thereby, water can be appropriately retained in the pores of the anode catalyst layer 23 near the electrolyte membrane 22 . Therefore, by performing a test run of the electrochemical hydrogen pump 100 before the user starts using it for the first time, the electrolyte membrane 22 of the electrochemical hydrogen pump 100 can be dried up when the user starts using it for the first time. It is thought that it becomes possible to suppress it.

Further, for example, when the user performs a test run of the electrochemical hydrogen pump 100 before starting use for the first time, the pressure difference (high pressure) generated by the electrochemical hydrogen pump 100 causes the pair of main surfaces of the electrolyte membrane 22 to The pores in the electrolyte membrane 22 can be appropriately shrunk when the provided unevenness is formed in the size relationship described above. As a result, the amount of reverse osmosis water that moves from the cathode to the anode due to the differential pressure generated by the electrochemical hydrogen pump 100 can be suppressed, and the water can be appropriately retained within the pores of the electrolyte membrane 22. . Therefore, by performing a test run of the electrochemical hydrogen pump 100 before the user starts using it for the first time, the electrolyte membrane 22 of the electrochemical hydrogen pump 100 can be dried up when the user starts using it for the first time. It is thought that it becomes possible to suppress it.

(Example)
FIG. 5 is a diagram showing an example of the electrochemical hydrogen pump of the example of the first embodiment.

In the example shown in FIG. 5, the electrochemical hydrogen pump 100 includes an electrolyte membrane 22, an anode catalyst layer 23, a cathode catalyst layer 24, a voltage applicator 21, an anode gas diffusion layer 25, and a cathode gas diffusion layer 26. , an anode separator 27 and a cathode separator 28 .

Here, the electrolyte membrane 22, the anode catalyst layer 23, the cathode catalyst layer 24, and the voltage applicator 21 are the same as those of the electrochemical hydrogen pump 100 of the first embodiment, so description thereof will be omitted.

The anode gas diffusion layer 25 is provided on the anode catalyst layer 23 . The anode gas diffusion layer 25 is made of, for example, a porous material, and has corrosion resistance, electrical conductivity, and gas diffusion properties. In addition, the anode gas diffusion layer 25 is made of a highly rigid material that can suppress the displacement and deformation of the constituent members caused by the differential pressure between the anode and cathode of the electrochemical hydrogen pump 100 during the hydrogen compression operation of the electrochemical hydrogen pump 100. It is preferable to configure

For example, the anode gas diffusion layer 25 is composed of a porous material having corrosion resistance and electrical conductivity, such as a titanium (Ti) powder sintered body plated with platinum, but is not limited to this.

Here, the anode gas diffusion layer 25 may be subjected to a water-repellent treatment almost evenly in the plane, for example, by impregnating a titanium powder sintered body with a water-repellent solution and firing the sintered body. As the water-repellent solution, for example, a PTFE (polytetrafluoroethylene) solution or the like can be used, but it is not limited to this. When a PTFE solution is used as the water-repellent solution, an appropriate amount of PTFE particles adheres to the surface of the titanium powder sintered compact having a porous structure. As a result, the anode gas diffusion layer 25 exhibits water repellency.

A cathode gas diffusion layer 26 is provided on the cathode catalyst layer 24 . Also, the cathode gas diffusion layer 26 is made of a porous material and has electrical conductivity and gas diffusion properties. Furthermore, it is desirable that the cathode gas diffusion layer 26 have elasticity so as to appropriately follow the displacement and deformation of the constituent members caused by the differential pressure between the cathode and anode during operation of the electrochemical hydrogen pump 100 .

For example, the cathode gas diffusion layer 26 is composed of a porous material including carbon fibers, but is not limited to this. This porous body may be, for example, a porous carbon fiber sheet such as carbon paper, carbon cloth, or carbon felt.

Here, the cathode gas diffusion layer 26 may be subjected to a water-repellent treatment substantially evenly in the plane by, for example, impregnating a carbon fiber sheet with a water-repellent solution and baking the carbon fiber sheet. As the water-repellent solution, for example, a PTFE solution or the like can be used, but it is not limited to this. When a PTFE solution is used as the water-repellent solution, an appropriate amount of PTFE particles adheres to the surface of the porous carbon fiber sheet. As a result, the cathode gas diffusion layer 26 exhibits water repellency.

The anode separator 27 is a member provided on the anode gas diffusion layer 25 . The cathode separator 28 is a member provided on the cathode gas diffusion layer 26 . A concave portion is provided in each central portion of the anode separator 27 and the cathode separator 28 . Each of these recesses accommodates an anode gas diffusion layer 25 and a cathode gas diffusion layer 26, respectively.

The anode separator 27 and the cathode separator 28 are made of, for example, metal members and have corrosion resistance and electrical conductivity. As a material of the anode separator 27 and the cathode separator 28, for example, titanium plated with platinum can be used, but the material is not limited to this.

In plan view, a sealing member is provided in an annular groove (not shown) of the anode separator 27 so as to surround the anode catalyst layer 23, and the hydrogen-containing gas is properly sealed by this sealing member. . In a plan view, a sealing member is provided in an annular groove (not shown) of the cathode separator 28 so as to surround the cathode catalyst layer 24, and hydrogen is properly sealed by this sealing member.

Here, the anode separator 27 is provided with a hydrogen-containing gas inlet 29 _IN and a hydrogen-containing gas outlet 29 _OUT extending from the outer surface of the anode separator 27 to the main surface within the recess of the anode separator 27 . there is A serpentine-shaped anode gas channel 29 including, for example, a plurality of U-shaped folded portions and a plurality of straight portions in plan view is provided on the main surface of the concave portion of the anode separator 27. One end of the channel 29 communicates with the hydrogen-containing gas inlet 29 _IN , and the other end of the anode gas channel 29 communicates with the hydrogen-containing gas outlet 29 _OUT . However, such an anode gas flow path is an example and is not limited to this example. For example, the anode gas channel may be composed of a plurality of linear channels.

As described above, during the hydrogen compression operation of the electrochemical hydrogen pump 100, when the hydrogen-containing gas passes through the anode gas flow path 29, part of the hydrogen-containing gas is supplied to the anode catalyst layer 23 through the anode gas diffusion layer 25. As a result, the hydrogen in the hydrogen-containing gas is boosted in the electrochemical hydrogen pump 100 .

The cathode separator 28 is provided with a cathode gas outlet 40 extending from the outer surface of the cathode separator 28 to the main surface within the recess of the cathode separator 28 . The cathode gas outlet 40 is connected to a gas lead-out path (not shown) through which high-pressure hydrogen pressurized at the cathode of the electrochemical hydrogen pump 100 flows to the outside.

As described above, during the hydrogen compression operation of the electrochemical hydrogen pump 100, the pressure loss in the gas lead-out path can be reduced by using the flow rate regulator on the gas lead-out path. is led out from the cathode gas outlet 40 through the gas lead-out path.

Although not shown in FIG. 5, members and equipment necessary for the hydrogen compression operation of the electrochemical hydrogen pump 100 of this embodiment are appropriately provided.

For example, in the electrochemical hydrogen pump 100, about 10 to 200 cells composed of MEAs, anode separators 27 and cathode separators 28 are stacked to form a laminate. It may be sandwiched between the end plates, and the both end plates may be fastened with a fastening rod or the like. Note that the number of such cells can be set to an appropriate number based on the operating conditions of the electrochemical hydrogen pump 100 . At this time, sealing members such as O-rings and gaskets are provided on both sides of the MEA so that the high-pressure gas does not leak from the electrochemical hydrogen pump 100 to the outside, and the MEA may be pre-assembled integrally with the MEA. The conductive anode separator 27 and cathode separator 28 are arranged outside the MEA for mechanically fixing the MEA and electrically connecting adjacent MEAs in series.

Hydrogen-containing gas may also be supplied to the electrochemical hydrogen pump 100 from an external source of hydrogen having a predetermined supply pressure. External hydrogen sources can include, for example, gas reservoirs (eg, gas cylinders), gas distribution infrastructure, and the like. In this case, the hydrogen-containing gas may be generated, for example, by a reformer, a water electrolysis device, or the like.

In addition, the hydrogen pressurized by the cathode of the electrochemical hydrogen pump 100 can be supplied to the hydrogen consumer in a timely manner. Examples of hydrogen demanders include household fuel cells and automobile fuel cells.

It should be noted that the configuration of the electrochemical hydrogen pump 100 described above and various members and devices (not shown) are merely examples, and are not limited to this example. For example, the electrochemical hydrogen pump 100 does not provide the hydrogen-containing gas outlet 29 _OUT in the anode separator 27, and the entire amount of hydrogen (H ₂ ) in the hydrogen-containing gas supplied to the anode through the hydrogen-containing gas inlet 29 _IN is A dead-end structure in which the voltage is boosted at the cathode may be employed.

The electrochemical hydrogen pump 100 of this embodiment may be the same as the electrochemical hydrogen pump 100 of the first embodiment except for the features described above.

(Second embodiment)
FIG. 6 is a diagram showing an example of the electrochemical hydrogen pump of the second embodiment.

In the example shown in FIG. 6, the electrochemical hydrogen pump 100 includes an electrolyte membrane 22, an anode catalyst layer 23, a cathode catalyst layer 24, a voltage applicator 21, a first water-repellent layer 30, and a second water-repellent layer. 31 and. In the electrochemical hydrogen pump 100 of this embodiment, the anode (electrode) of the electrochemical hydrogen pump 100 is composed of the anode catalyst layer 23, the first water-repellent layer 30 and the anode gas diffusion layer (not shown in FIG. 6). It is configured. The cathode (electrode) of the electrochemical hydrogen pump 100 is composed of a cathode catalyst layer 24, a second water-repellent layer 31 and a cathode gas diffusion layer (not shown in FIG. 6).

Here, the electrolyte membrane 22, the anode catalyst layer 23, the cathode catalyst layer 24, and the voltage applicator 21 are the same as those of the electrochemical hydrogen pump 100 of the first embodiment, so description thereof will be omitted.

The first water-repellent layer 30 is a layer containing a water-repellent material provided on the anode catalyst layer 23 . The first water-repellent layer 30 may have any structure as long as it is a layer containing such a water-repellent material. For example, the first water-repellent layer 30 may be a microporous layer in which a conductive material and a water-repellent material are mixed. In addition, although carbon black etc. can be mentioned as an electrically conductive material, for example, it is not limited to this. Examples of the water-repellent material include PTFE and FEP (polypropylene tetrafluoride/hexafluoride copolymer), but are not limited to these.

The second water-repellent layer 31 is a layer containing a water-repellent material provided on the cathode catalyst layer 24 . The second water-repellent layer 31 may have any structure as long as it is a layer containing such a water-repellent material. For example, the second water-repellent layer 31 may be a microporous layer in which a conductive material and a water-repellent material are mixed. In addition, although carbon black etc. can be mentioned as an electrically conductive material, for example, it is not limited to this. Examples of water-repellent materials include, but are not limited to, PTFE and FEP.

As shown in FIG. 6 , in the electrochemical hydrogen pump 100 of the present embodiment, the main surface of the first water-repellent layer 30 on the anode catalyst layer 23 side is provided with irregularities 300 along the irregularities of the anode catalyst layer 23 . there is Further, the main surface of the first water-repellent layer 30 on the anode catalyst layer side is more uneven than the main surface of the second water-repellent layer 31 on the cathode catalyst layer 24 side.

The configuration of the electrochemical hydrogen pump 100 described above is realized, for example, by performing a test run of the electrochemical hydrogen pump 100 before the user starts using it for the first time. The details can be easily understood from the electron microscopic observation of the cross section of the cell described above and the description of the first embodiment, so the details are omitted.

As described above, the electrochemical hydrogen pump 100 of this embodiment can improve the efficiency of the hydrogen compression operation more than before when the user starts using it for the first time.

For example, when the user performs a test run of the electrochemical hydrogen pump 100 before starting use for the first time, the differential pressure (high pressure) generated by the electrochemical hydrogen pump 100 causes the anode catalyst layer of the first water-repellent layer 30 to The main surface on the 23 side is provided with irregularities 300 along the irregularities of the anode catalyst layer 23 . In this case, the first water-repellent layer 30 is more prone to cracks than the second water-repellent layer 31 due to the size relationship between the unevennesses 300 and 301 between the first water-repellent layer 30 and the second water-repellent layer 31 . is likely to occur. Then, in the first water-repellent layer 30 , compared to the second water-repellent layer 31 , water can enter and exit between both main surfaces of the first water-repellent layer 30 at the anode through cracks in the first water-repellent layer 30 . easy to promote. As a result, by performing a test run of the electrochemical hydrogen pump 100 before the user starts using it for the first time, the electrolyte membrane 22 of the electrochemical hydrogen pump 100 is dried up when the user starts using it for the first time. can be suppressed.

Note that the higher the differential pressure generated by the electrochemical hydrogen pump 100, the greater the reverse osmosis water flux (j _P ) that moves from the cathode to the anode. Therefore, as the hydrogen compression operation of the electrochemical hydrogen pump 100 progresses, the amount of moisture present at the anode may become greater than that present at the cathode. Then, flooding of the anode is likely to occur due to reverse osmosis water to the anode. If the diffusibility of hydrogen is hindered at the anode due to the occurrence of such flooding, the diffusion resistance of the electrochemical hydrogen pump 100 may increase. efficiency may decrease.

Therefore, in the electrochemical hydrogen pump 100 of the present embodiment, the first water-repellent layer 30 is provided on the anode catalyst layer 23 to suppress the occurrence of flooding at the anode. Specifically, for example, in the first water-repellent layer 30, the water existing in the anode tends to move out of the anode together with the hydrogen-containing gas due to the flow of the hydrogen-containing gas in the anode.

Conversely, the lower the differential pressure generated by the electrochemical hydrogen pump 100, the smaller the reverse osmosis water flux (j _P ) moving from the cathode to the anode. , the moisture present at the cathode can be greater than that present at the anode. As a result, condensed water is likely to be generated from the hydrogen-containing gas at the cathode. The condensed water moves from the cathode to the anode via the electrolyte membrane 22 .

Therefore, in the electrochemical hydrogen pump 100 of the present embodiment, the second water-repellent layer 31 is provided on the cathode catalyst layer 24, so that even if the differential pressure generated in the electrochemical hydrogen pump 100 increases, the second water-repellent layer It is considered that the movement of condensed water existing outside the layer 31 to the electrolyte membrane 22 can be appropriately suppressed.

As described above, the electrochemical hydrogen pump 100 of the present embodiment can improve the state in which excess water stays in the anode, and thus can appropriately suppress the occurrence of flooding in the anode.

The electrochemical hydrogen pump 100 of this embodiment may be the same as the electrochemical hydrogen pump 100 of the first embodiment or the example of the first embodiment, except for the features described above.

(Third Embodiment)
Before the user starts using the electrochemical hydrogen pump 100 of the third embodiment, the moisture in the cells including the electrolyte membrane 22, the cathode catalyst layer 24 and the anode catalyst layer 23 is retained as follows. Other than that, it is the same as the electrochemical hydrogen pump 100 of the first embodiment.

In the electrochemical hydrogen pump 100 of the present embodiment, before the user starts using it for the first time, the above-mentioned cell is placed in an atmosphere with a relative humidity of 80% at the cell temperature during the hydrogen compression operation of the electrochemical hydrogen pump 100. retains more than the moisture content of The moisture content of the cell can be derived as follows by dividing the change in weight before and after drying by the weight after drying.

<Derivation of cell moisture content>
In general, both sides of the electrolyte membrane are provided with a laminate of a catalyst layer and a gas diffusion layer, or a laminate of a catalyst layer, a microporous layer (water-repellent layer) and a gas diffusion layer. Here, when dismantling the cell, it is easy to peel off the gas diffusion layer from the electrolyte membrane. However, due to the adhesion function of the ionomer in the catalyst layer, the electrolyte membrane and the catalyst layer are bonded together in an intimate state.

Therefore, in measuring the water content of the cell of this embodiment, a cell having the same structure as the cell used in the hydrogen compression test was used, and the hydrogen compression test was performed four times, and the water content A of the cell was derived by the following method. .

Only the gas diffusion layers on both sides of the electrolyte membrane were peeled off from the electrolyte membrane before weighing the cell. In other words, the moisture content of the cell was obtained while the catalyst layer and the microporous layer were provided on both sides of the electrolyte membrane.

First, the weight (W1) of the cell was measured before drying the cell.

Next, a dry gas of about 120° C. was passed through the cell to sufficiently dry the cell, and then the dry weight (W2) of the cell was measured. Then, the water content A of the cell was calculated by the following formula (3).
Moisture content A = (W1-W2)/W2 x 100 (3)

Next, as a comparative example, the moisture content B, which corresponds to the moisture content of the cell under the atmosphere of 80% relative humidity at the temperature of the cell during the hydrogen compression operation of the electrochemical hydrogen pump 100, was derived by the following method.

First, the temperature of the cell was set to 50° C., and a hydrogen-containing gas with a relative humidity of 80% at this temperature (50° C.) was circulated until the weight of the cell became constant.

Next, the weight (W3) of the cell was measured. Then, the water content B of the cell was calculated by the following formula (4).
Moisture content B = (W3-W2)/W2 x 100 (4)

<Comparison>
When the water content A and the water content B were compared, it was found that the water content A of the cell corresponding to the overvoltage and resistance of the cell when the hydrogen compression test (four times) of FIG. It was found that the temperature of the cell during the hydrogen compression operation was equal to or higher than the moisture content B, which corresponds to the moisture content in an atmosphere with a relative humidity of 80% (that is, moisture content A≧water content B).

As described above, the electrochemical hydrogen pump 100 of the present embodiment retains water having a water content B or more in the cell when the hydrogen compression operation of the electrochemical hydrogen pump 100 is performed before the user starts using it for the first time. can let As a result, the electrolyte membrane 22 can be sufficiently humidified by performing the hydrogen compression operation of the electrochemical hydrogen pump 100 before the user starts the first use, so that the user can start the first use. It is possible to suppress dry-up of the electrolyte membrane 22 of the electrochemical hydrogen pump 100 when pumping.

The electrochemical hydrogen pump 100 of this embodiment may be the same as the electrochemical hydrogen pump 100 of any one of the first embodiment, the example of the first embodiment, and the second embodiment, except for the features described above. .

The first embodiment, the examples of the first embodiment, the second embodiment, and the third embodiment may be combined with each other as long as they do not exclude each other.

Also, many modifications and other embodiments of the present disclosure will be apparent to those skilled in the art from the above description. Accordingly, the foregoing description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. Substantial changes may be made in its operating conditions, composition, structure and/or function without departing from the spirit of this disclosure.

One aspect of the present disclosure can be utilized in an electrochemical hydrogen pump that can improve the efficiency of the hydrogen compression operation when the user first starts using it.

21 : Voltage applicator 22 : Electrolyte membrane 23 : Anode catalyst layer 24 : Cathode catalyst layer 25 : Anode gas diffusion layer 26 : Cathode gas diffusion layer 27 : Anode separator 28 : Cathode separator 29 : Anode gas channel 29 _IN : Hydrogen containing Gas inlet 29 _OUT : Hydrogen-containing gas outlet 30: First water-repellent layer 31: Second water-repellent layer 40: Cathode gas outlet 100: Electrochemical hydrogen pump 200: Unevenness 201: Unevenness 300: Unevenness 301: Unevenness

Claims (7)

an electrolyte membrane comprising a pair of main surfaces;
a cathode catalyst layer provided on one main surface of the electrolyte membrane;
an anode catalyst layer provided on the other main surface of the electrolyte membrane;
a voltage applicator that applies a voltage between the cathode catalyst layer and the anode catalyst layer;
An electrochemical hydrogen pump that moves hydrogen in the hydrogen-containing gas supplied onto the anode catalyst layer onto the cathode catalyst layer and boosts the pressure by applying the voltage from the voltage applicator,
Before the user starts using for the first time,
The electrochemical hydrogen pump, wherein the anode catalyst layer has a larger uneven cross-sectional shape than the cathode catalyst layer. A first water-repellent layer containing a water-repellent material provided on the anode catalyst layer,
2. The electrochemical hydrogen pump according to claim 1, wherein the main surface of the first water-repellent layer on the anode catalyst layer side has irregularities along the irregularities of the anode catalyst layer. a second water-repellent layer containing a water-repellent material provided on the cathode catalyst layer;
3. The electrochemical hydrogen pump according to claim 2, wherein the main surface of the first water-repellent layer on the anode catalyst layer side is more uneven than the main surface of the second water-repellent layer on the cathode catalyst layer side. The electrochemical hydrogen pump according to any one of claims 1 to 3, wherein the anode catalyst layer is thinner than the cathode catalyst layer. The electrochemical hydrogen pump according to any one of claims 1 to 4, wherein the anode catalyst layer has a smaller porosity than the cathode catalyst layer. The electrochemical hydrogen pump according to any one of claims 1 to 5, wherein the main surface of the electrolyte membrane on the anode catalyst layer side is more uneven than the main surface on the cathode catalyst layer side. Prior to first use by a user, the cell, including the electrolyte membrane, the cathode catalyst layer and the anode catalyst layer, is subjected to a relative humidity of 80% at a temperature of the cell during hydrogen compression operation of the electrochemical hydrogen pump. The electrochemical hydrogen pump according to any one of claims 1 to 6, which retains moisture equal to or higher than the moisture content in the atmosphere.

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