KR20240056151A - composite membrane-electrode assembly for hydrogen isotope separation based on water electrolysis, hydrogen isotope separation system and method for separation of hydrogen isotopes using the same assembly - Google Patents

Abstract

The present invention relates to a composite membrane-electrode composite for hydrogen isotope separation by water electrolysis, a hydrogen isotope separation system and a hydrogen isotope separation method using the same, and specifically, to significantly improve the separation ability of light hydrogen, heavy hydrogen, and tritium. A composite membrane-electrode complex for hydrogen isotope separation by water electrolysis that can be used as a technology to improve the concentration of deuterium or tritium water containing separated deuterium and tritium, and hydrogen isotope separation using the same. It relates to systems and hydrogen isotope separation methods.

Description

Composite membrane-electrode assembly for hydrogen isotope separation based on water electrolysis, hydrogen isotope separation system and method for using the same separation of hydrogen isotopes using the same assembly}

The present invention relates to a composite membrane-electrode composite for hydrogen isotope separation by water electrolysis, a hydrogen isotope separation system and a hydrogen isotope separation method using the same, and specifically, to significantly improve the separation ability of light hydrogen, heavy hydrogen, and tritium. A composite membrane-electrode complex for hydrogen isotope separation by water electrolysis that can be used as a technology to improve the concentration of deuterium or tritium water containing separated deuterium and tritium, and hydrogen isotope separation using the same. It relates to systems and hydrogen isotope separation methods.

Isotopes of hydrogen naturally include light hydrogen (H), deuterium (D), and tritium (T). In water, when the content of D or T is low, they exist as compounds in the form of HDO or HTO. do. Deuterium and tritium have the characteristic of having a larger atomic weight than general light hydrogen. High-purity deuterium and tritium are used as expensive raw materials. Deuterium is used in various fields such as the semiconductor and display industries and analytical chemistry, and tritium is used in industries such as self-luminous materials and nuclear fusion. Therefore, hydrogen isotope separation technology is very important in terms of production of useful resources.

Meanwhile, tritium is a radioactive substance and is hazardous. Tritium is generated during the operation of a nuclear power plant. In pressurized water reactors, it is generated as a mixture of HTO/H ₂ O by the neutron reaction of boron and lithium contained in the coolant, and in heavy water reactors, neutrons of deuterium contained in the moderator and coolant are generated. The reaction produces a mixture of DTO/D ₂ O. If it is leaked into the environment through an unplanned route due to a leak or accident during the operation of a nuclear power plant, it will cause environmental pollution such as groundwater and generate a large amount of tritium contaminated water. Tritium-containing cooling water, moderators, and contaminated water generated during the operation and decommissioning of nuclear power plants must be purified to meet emission management standards, but tritium water has physical and chemical properties similar to water, so it is difficult to separate.

A very small amount of tritium naturally exists in aquatic environments such as groundwater and surface water, but in order to accurately quantitatively analyze the concentration of tritium, a pretreatment step is required to concentrate tritium in water to a level that can be analyzed, and this requires hydrogen isotopes. Separation technology that separates and concentrates the liquid is important.

Hydrogen isotope separation technologies such as water distillation process, cryogenic distillation process, catalytic exchange process, laser separation technology, and electrolysis technology have been developed to separate light hydrogen, heavy hydrogen, and tritium mixtures. However, for efficient separation, high separation efficiency is required. improvement is needed.

Electrolysis separates hydrogen isotopes by generating hydrogen gas with a low content of deuterium or tritium in the process of decomposing water to generate gas. A general alkaline water electrolysis device can be used to concentrate deuterium or tritium from a large amount of water, but since concentration occurs in a state containing electrolytes such as KOH, an additional desalting step is required, and the current density is low, so the device scale is small. There is a big drawback.

As polymer electrolyte membrane water electrolyzer technology improves, it can be applied as a technology for hydrogen isotope separation. Commercial polymer electrolyte membranes based on perfluorinated sulfonic acid (Nafion, etc.) are used, but the difference in diffusion between hydrogen isotopes within a typical polymer electrolyte membrane is small, so a polymer electrolyte membrane-electrode complex is needed to increase the hydrogen isotope separation effect.

Recently, the use of hydrogen ion conductive materials and two-dimensional material complexes is expected to enable separation of hydrogen ions due to differences in hydrogen isotope permeability for the two-dimensional materials. However, separation of hydrogen gas isotope mixtures (H ₂ , D ₂ ) is expected to be possible. A technology to utilize it as an electrochemical hydrogen pump has been proposed, and is attracting attention as a technology for separating hydrogen/deuterium mixtures. However, it is difficult to apply to the separation of deuterium or tritium contained in an aqueous liquid, and there is a difficulty in converting the aqueous solution into gas and then separating the gas mixture using an electrochemical hydrogen pump.

US patent 2018/0056240 A1 (2018.03.01.)

The present invention was invented to solve the above-described conventional problems. The problem to be solved by the present invention is to provide a hydrogen isotope ion separation membrane that improves hydrogen isotope separation performance based on electrolysis and a membrane-electrode complex thereof. To provide a method and system for improving separation performance by extracting relatively light hydrogen isotopes from an aqueous solution mixture as gas and concentrating deuterium or tritium in an aqueous solution.

In order to solve the above-described technical problem, the present invention provides a semi-permeable ion separation membrane having a difference in permeability for hydrogen isotope ions; and a hydrogen ion conductive polymer electrolyte membrane formed on at least one surface of the ion separation membrane; a composite membrane for water electrolysis comprising a. An anode catalyst formed on both sides of the composite membrane for water electrolysis; and a cathode catalyst that induces hydrogen isotope exchange. It provides a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, including a cathode catalyst that induces hydrogen isotope exchange.

In addition, a hydrogen ion conductive polymer electrolyte membrane; and a composite membrane for water electrolysis in which a two-dimensional crystal material having a difference in permeability to hydrogen isotope ions is dispersed within the hydrogen ion conductive polymer electrolyte membrane, and an anode formed to face both sides of the composite membrane for water electrolysis. catalyst; and a cathode catalyst that induces hydrogen isotope exchange. It provides a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, including a cathode catalyst that induces hydrogen isotope exchange.

In addition, it includes the composite membrane-electrode complex for hydrogen isotope separation by water electrolysis described above, wherein the composite membrane-electrode complex for hydrogen isotope separation by water electrolysis is supplied with water near the anode. It includes an inlet for injecting oxygen (O ₂ ) and an outlet for unreacted water generated by the oxidation-reduction reaction, and an outlet for hydrogen (H2) generated by the oxidation-reduction reaction near the cathode. Provided is a hydrogen isotope separation system comprising:

In addition, the present invention is a method of separating light hydrogen (H, hydrogen) contained in water (H ₂ O) from heavy hydrogen (D, Deuterium) and tritium (T, Tritium) using the above-described hydrogen isotope separation system. , injecting water containing deuterium and tritium through an inlet near the anode; A voltage is applied between the anode and the cathode to perform an oxygen generation reaction at the anode, and the hydrogen ions generated as a result of the oxygen generation reaction are attracted by electric force and move toward the cathode. It provides a hydrogen isotope separation method comprising: penetrating the ion separation membrane, reaching the cathode, causing a hydrogen generation reaction, and generating hydrogen gas having a concentrated light hydrogen mole fraction compared to the light hydrogen mole fraction in the input water. .

When separating hydrogen isotopes by employing the composite membrane-electrode complex for hydrogen isotope separation by water electrolysis according to the present invention and the isotope separation system using the same, it has improved hydrogen isotope separation ability and light hydrogen is collected as gas. The remaining discharged water is concentrated in deuterium or tritium, so it can be used as a method of producing deuterium-enriched water or tritium-concentrated water, and it can also be used as a method of treating tritium-contaminated water.

1 is a diagram schematically showing the structure of a composite membrane-electrode complex for water electrolysis applied to a hydrogen isotope separation system according to a preferred embodiment of the present invention.
Figure 2 is a diagram schematically showing only the core components of a hydrogen isotope separation system according to a preferred embodiment of the present invention.
Figure 3a is a diagram schematically showing the structure of a water electrolysis-based hydrogen isotope separation device according to a preferred embodiment of the present invention.
Figure 3b is a diagram schematically showing the structure of a tritium contaminated water treatment device using a water electrolysis-based hydrogen isotope separation device according to a preferred embodiment of the present invention.
Figure 4 is a diagram schematically showing the manufacturing process of a composite membrane-electrode composite for water electrolysis according to a preferred embodiment of the present invention.
Figure 5a is a photograph taken using an SEM microscope of the surface structure of a composite membrane combining an ion separation membrane and a hydrogen ion conductive polymer electrolyte membrane according to a preferred embodiment of the present invention.
Figure 5b is a photograph of a composite membrane-electrode composite according to a preferred embodiment of the present invention.
Figure 6 shows a comparison of the deuterium (D) and light deuterium (H) separation coefficients measured when Nafion alone, hBN/Nafion composite membrane, and graphene/Nafion composite membrane were used in the composite membrane-electrode composite, respectively. This is one graph.
Figure 7 is a schematic diagram schematically showing the principle of separation of hydrogen/deuterium or tritium using a composite membrane-electrode composite according to a preferred embodiment of the present invention.
FIG. 8 is a graph comparing the tritium separation performance measured when a Nafion alone membrane, an hBN/Nafion composite membrane, and a graphene/Nafion composite membrane were used in the composite membrane-electrode composite used in FIG. 7.
Figures 9a and 9b show a comparison of the hydrogen isotope separation ability by water electrolysis when a Nafion alone membrane is used and a graphene/Nafion composite membrane is used in a composite membrane-electrode complex for water electrolysis according to a preferred embodiment of the present invention. It's a graph.

Hereinafter, the specific configuration and effects of the present invention will be described in more detail.

Conventionally, water electrolysis has been widely used as a method to separate light hydrogen, heavy hydrogen, and tritium from water containing hydrogen isotopes, but the difference in diffusion ability between hydrogen isotopes in the ion conductive electrolyte is not large, so separation is not possible. The effect was not large, so multiple repeated separations had to be performed, which had the disadvantage of being costly and time-consuming.

Accordingly, the present inventors accelerated research to solve this problem and developed a hydrogen isotope separation method with improved resolution.

In the present invention, a semi-permeable ion separation membrane having a difference in permeability between hydrogen isotope ions; and a hydrogen ion conductive polymer electrolyte membrane formed on at least one surface of the semi-permeable ion separation membrane; a composite membrane for water electrolysis comprising a. An anode catalyst formed on both sides of the composite membrane for water electrolysis; and a cathode catalyst that induces hydrogen isotope exchange. By providing a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, it was possible to implement a separation method with significantly improved hydrogen isotope separation ability.

The semi-permeable ion separation membrane may preferably be made of a two-dimensional crystal material. Two-dimensional crystal materials can transmit hydrogen ions between the lattices, but light hydrogen ions, heavy hydrogen ions, and tritium ions have different sizes due to differences in the number of neutrons, so there is a difference in permeability when they pass through the lattices of two-dimensional crystal materials. occurs. Therefore, the two-dimensional crystal material can be an effective semipermeable membrane for separating light hydrogen, heavy hydrogen, and tritium.

The present invention also provides, as another aspect of the invention, a hydrogen ion conductive polymer electrolyte membrane; and a composite membrane for water electrolysis in which a two-dimensional crystal material having a difference in permeability to hydrogen isotope ions is dispersed within the hydrogen ion conductive polymer electrolyte membrane, and an anode formed to face both sides of the composite membrane for water electrolysis. catalyst; and a cathode catalyst that induces hydrogen isotope exchange. It provides a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, including a cathode catalyst that induces hydrogen isotope exchange.

In this specification, “anode” means “anode” in the dictionary meaning of the electrode where oxygen generation reaction occurs in water electrolysis reaction, and “cathode” means “anode” where hydrogen generation reaction occurs in water electrolysis reaction. The electrode that occurs means “cathode” in the dictionary.

In addition, in this specification, “anode catalyst” or “cathode catalyst” is a term used to indicate that the anode is made of a catalytic material and is not a material consumed by a direct reaction, and “in “Node” and “anode catalyst” refer to the same thing, and “cathode” and “cathode catalyst” refer to the same thing.

In the present invention, in the process of separating water into hydrogen and oxygen by electrolysis, water is injected into the anode to first cause an oxygen evolution reaction (OER) to produce oxygen gas (O ₂ ) is generated, and the hydrogen ions generated along with the oxygen move across the electrolyte toward the cathode, causing a hydrogen evolution reaction (HER) at the cathode to generate hydrogen gas (H ₂ ), As hydrogen ions move across the electrolyte, light hydrogen (H, Hydrogen), heavy hydrogen (D, Deuterium), and tritium (T,) each have different diffusion rates within the electrolyte, so the content of light hydrogen in the generated hydrogen gas increases. Separation of hydrogen isotopes is achieved by using the increase in water to concentrate deuterium and tritium and reducing the content of tritium, a radioactive isotope, in the generated gas.

However, as described above, the diffusion rate of hydrogen isotope ions in the electrolyte is not particularly large, so this separation method has not been effective in the past. In the present invention, the electrolyte has transmission selectivity between hydrogen isotope ions. Separation performance could be significantly improved by additionally providing a semi-permeable ion separation membrane. This ion separation membrane can be provided in two forms. One method is to provide a semi-permeable ion separator separately from the hydrogen ion conductive polymer electrolyte membrane, and the other method is to provide a two-dimensional crystal material forming the semi-permeable ion separator dispersed within the hydrogen ion conductive polymer electrolyte membrane.

Figure 3 is a schematic diagram schematically showing the manufacturing process of a composite membrane-electrode composite according to a preferred embodiment of the present invention. In particular, it relates to a manufacturing process of a composite membrane-electrode complex in which a semi-permeable ion separation membrane and a hydrogen ion conductive polymer electrolyte membrane are separate layers, and a semi-permeable ion separation membrane (110) is formed on the hydrogen ion conductive polymer electrolyte membrane (100). ) and a metal layer (Cu) are formed, heated and compressed, and then the metal is removed by a method such as etching. Afterwards, an anode and a cathode are heated and pressed to this composite to manufacture a composite membrane-electrode composite.

At this time, the electrode of the composite membrane-electrode composite may be formed by attaching it to the composite membrane in a powder-coated form on a porous transport layer or gas diffusion layer, or by directly transferring the electrode catalyst itself to the composite membrane. It can also be manufactured by attaching it.

In the latter case, the final composite can be manufactured by laminating a porous transport layer or gas diffusion layer to the three-layer structure composite of electrode-composite membrane-electrode, and in the former case, powder of the electrode (catalyst) is added to the porous transport layer or gas diffusion layer such as carbon paper. After coating, it can be finalized by attaching it to a separator.

However, the semi-permeable ion separation membrane does not necessarily have to be formed on only one side of the hydrogen ion conductive polymer electrolyte membrane as shown in FIG. 3, and may be formed on both sides.

The semi-permeable ion separation membrane is made of a two-dimensional crystal material, and the two-dimensional crystal material allows hydrogen ions to pass through its crystal lattice, allowing hydrogen ions to move between the anode and the cathode. . However, depending on the size of the crystal lattice, light hydrogen, heavy hydrogen, and tritium each have different diffusion rates, resulting in a lot of light hydrogen permeating, while heavy hydrogen and tritium have low permeability, so the cathode contains a lot of light hydrogen. Hydrogen gas is generated, and water with a concentrated concentration of deuterium and trihydrogen remains at the anode.

In a preferred embodiment of the present invention, the two-dimensional crystal material is graphene, hexagonal Boron Nitride (hBN), g-C3N4, Black Phosphorus, borophene, It may be one or more selected from graphene, graphdiyne, phyllosilicate, transition metal oxide, and layered double hydroxide. However, it is not necessarily limited to this, as long as it is a material with a two-dimensional crystal structure that is conductive to hydrogen ions and does not have properties that interfere with achieving the purpose of the present invention (e.g., decomposition in electrolyte). Anything can be used.

Preferably, the ion separation membrane can be formed using graphene or hexagonal boron nitride crystals.

In a preferred embodiment of the present invention, the semi-permeable ion separation membrane may have a structure in which 1 to 100 layers of the two-dimensional crystal material are stacked. If the number of layers exceeds 100, the conductivity of hydrogen ions in the electrolyte decreases excessively, so it is not appropriate because it has characteristics that run counter to the purpose of the present invention, such as requiring a lot of power to be input. More preferably, the semi-permeable ion separation membrane may have a structure in which 10 to 30 layers of the two-dimensional crystal material are stacked. Since deuterium or tritium ions cannot pass through the crystal lattice of the two-dimensional crystal material at all, a large number of stackings is advantageous for improving resolution, but if the number of stackings is too high, light hydrogen ions also have a problem of reduced transmittance. Therefore, it is desirable to limit the number of layers to the above range.

In a preferred embodiment of the present invention, the semi-permeable ion separation membrane may have one continuous layer of the two-dimensional crystal material per layer. In other words, the entire membrane may be composed of a single crystal. Additionally, in another embodiment, the semi-permeable ion separation membrane may have a form in which flakes of the two-dimensional crystal material with a surface diameter of 10 nm to 100 μm are aggregated.

Here, the term “flakes are assembled” refers to a form in which two-dimensional crystal materials in the form of flakes are compressed to form a semi-permeable ion separation membrane.

Additionally, “flake having an in-plane diameter of ##nm (or ##μm)” means that flake-shaped particles are like circles having a diameter of ##nm (or ##μm) in the in-plane direction. It means having an area.

In both cases, there is a difference in permeability to hydrogen isotope ions, but preferably, each layer is made of a single crystal, which is superior in separation performance. Conversely, if a semi-permeable ion separation membrane is made of a collection of flakes of a two-dimensional crystal material, manufacturing costs can be reduced.

In a preferred embodiment of the present invention, the hydrogen ion conductive polymer membrane is sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, polybenzimidazole, sulfonated polyether ether ketone (poly ether ether) It may be one or more selected from ketone, PEEK) and polysulfone.

The hydrogen ion conductive polymer membrane can be selected from polymer electrolytes having ionic conductivity, but does not necessarily have to be selected from those listed above, and can be selected without limitation as long as it can be used as a polymer electrolyte membrane for water electrolysis.

The anode is an electrode catalyst for performing an oxygen generation reaction, and preferably includes iridium (Ir) and its oxide, which are materials that are stable even at high current densities, and include nickel (Ni), cobalt (Co), A catalyst selected from alloys and oxides containing one or more of iron (Fe), lanthanum (La), platinum (Pt), manganese (Mn), tungsten (W), and rubidium (Ru) can be used.

In addition, the cathode is an electrode catalyst for performing a hydrogen generation reaction, and is preferably platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), silver (Ag), and copper (Cu). , one or more selected from iridium (Ir), nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), and chromium (Cr) can be used. However, it is not necessarily limited to this. They may be used while supported on porous carbon or carbon compound powder, or may be used directly.

In addition, the present invention includes the above-described composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, wherein the composite membrane-electrode complex for hydrogen isotope separation by water electrolysis includes input water near the anode. It includes an inlet for injecting water and an outlet for oxygen (O ₂ ) and unreacted water generated by the oxidation-reduction reaction, and an outlet for hydrogen (H ₂ ) generated by the oxidation-reduction reaction near the cathode. It provides a hydrogen isotope separation system including.

Figure 2 is a diagram schematically showing only the core components of a hydrogen isotope separation system including a composite membrane-electrode complex according to a preferred embodiment of the present invention. Referring to FIG. 2, the hydrogen ion conductive polymer electrolyte membrane 100 and the semi-permeable ion separation membrane 110 are located between the two electrodes 121 and 122, allowing ions to selectively permeate (there is a difference in permeability). The anode 121 is provided with an inlet 121' through which water can be injected, so that water electrolysis can be performed. From this, it can be seen that an oxygen generation reaction in which oxygen gas is generated occurs at the anode, and the generated oxygen can be discharged through the outlet (121”). In the oxygen generation reaction, hydrogen ions (H ⁺ ) are generated. The hydrogen generation reaction is a reaction that hydrogen ions undergo at the cathode 122. The hydrogen ions are attracted to the cathode by electric force and move to the polymer electrolyte. It passes through the composite membrane of the membrane 100 and the semi-permeable ion separation membrane 110. At this time, since the permeability is high for light hydrogen and relatively low for deuterium and tritium, the mole fraction of light hydrogen in the hydrogen generation reaction becomes larger than the mole fraction of light hydrogen contained in the input water (water). The generated hydrogen gas is discharged through the cathode side outlet (122”). Unreacted water is discharged through the anode side outlet. In the drawing, the oxygen gas outlet and the discharged water outlet are depicted as the same, but this is not necessarily the case. Importantly, hydrogen ions penetrate the semi-permeable ion separation membrane 110, but water molecules do not. Water molecules can move only when there is a defect in the ion separation membrane 110, so the permeability is very low. Accordingly, light hydrogen gradually penetrates toward the cathode and causes a hydrogen generation reaction, resulting in a concentrated concentration of deuterium and tritium in the discharged water.

In operating this system, the discharged water enriched in deuterium and tritium can be fed back into the inlet through the pump, and by repeating this separation process, the mole fraction of deuterium and tritium in the water is gradually concentrated. You can do it.

This system can also be used in combination with other devices to enrich isotopes such as deuterium or to treat water contaminated with radioactive hydrogen isotopes.

The present invention also provides a method for separating light hydrogen (H, hydrogen) contained in water (H ₂ O) from heavy hydrogen (D, Deuterium) and tritium (T, Tritium) using the above-described hydrogen isotope separation system. , injecting water containing deuterium and tritium through an inlet near the anode; And a voltage is applied between the anode and the cathode to perform an oxygen generation reaction at the anode, and the hydrogen ions generated as a result of the oxygen generation reaction are attracted by electric force and move to the cathode, A hydrogen isotope separation method comprising: passing through the semi-permeable ion separation membrane and reaching the cathode to cause a hydrogen generation reaction, thereby generating hydrogen gas having a concentrated light hydrogen mole fraction compared to the light hydrogen mole fraction in the input water. to provide.

Preferably, the hydrogen isotope separation method can be performed at 0°C to 80°C. Lower temperatures than that are not appropriate because water may freeze, and if the temperature exceeds 80°C, the separation effect may be impaired, so it is most appropriate to carry out the procedure within the above range. In addition, the operating conditions of the separation device are appropriately within 0.1 to 3 A/cm2, and the voltage is appropriately set to a range of 1.5V or more, which can decompose water. There is no particular limit to the upper limit, but the higher it is, the more the cost increases, so it can be performed within 3V as appropriate.

This can be performed as shown in FIG. 2 as described above, and referring to FIG. 6, the introduced water causes an oxygen generation reaction at the anode and the generated hydrogen ions are attracted by electromotive force and move to the cathode. However, since deuterium ions (D ⁺ ) and tritium ions (T ⁺ ) have low permeability, the proportion of light hydrogen is high in the hydrogen generation reaction.

Hereinafter, specific embodiments of the present invention will be described with reference to examples. The configuration of the present invention is limited only by the configuration described in the claims, and the examples are merely for illustrating specific aspects of the present invention by way of example and do not limit the scope of the invention. Those skilled in the art will be able to easily implement the invention within the scope of the invention by adding, changing, or deleting non-essential components of the invention by referring to the following examples.

<Example>

Example 1: Preparation of water electrolysis cell based on composite membrane-electrode composite

A copper foil on which a single layer of graphene was deposited was placed on a Nafion membrane, a hydrogen ion-conducting polymer, and attached using a hot press machine. Afterwards, copper was removed using an ammonium persulfate solution.

The above graphene-Nafion composite film was placed between Ti mesh (2 mg/cm2) coated with Ir black electrode and carbon paper (0.4 mg/cm2) coated with Pt/C and then used a hot press. By bonding, a composite membrane-electrode composite for water electrolysis was manufactured.

The composite membrane-electrode complex prepared as above was assembled into a water electrolysis stack using gaskets, titanium bipolar plates, aluminum end plates, etc.

Example 2: Preparation of water electrolysis cell based on composite membrane-electrode composite

A water electrolysis stack was assembled in the same manner as in Example 1, except that a hexagonal boron nitride (hBN) sheet was used as an ion separator instead of a graphene sheet.

Comparative Example 1: Manufacturing of water electrolysis cell based on composite membrane-electrode composite

The same procedure as in Example 1 was performed, but a water electrolysis stack was assembled using only the Nafion polymer membrane without the ion separation membrane.

<Experimental example>

Experimental Example 1: Evaluation of hydrogen/deuterium separation ability

After adding distilled water to the water tank, water was introduced into the anode side of the composite membrane-electrode composite-based water electrolysis cell manufactured according to Examples and Comparative Examples using a liquid transfer pump, and using a power supply device. Current was supplied to 0.28 A/cm2. The temperature of the water electrolysis cell was adjusted to 15 to 75°C by controlling the temperature of the water tank.

The moisture contained in the hydrogen gas generated from the cathode was recovered through a cooling device, the hydrogen isotope ratio of the hydrogen gas was measured using a quadrupole mass spectrometer or mass balance equation, and the hydrogen in the water generated from the water tank and cathode was measured. The /deuterium ratio was quantitatively analyzed using a cavity ring down spectrometer to confirm the separation of hydrogen/deuterium.

Figure 6 shows a measurement showing that when light hydrogen was separated in the form of hydrogen gas from distilled water containing 146 ppm of deuterium, the content of deuterium in the hydrogen gas was reduced. The graph on the left shows the content of deuterium in the hydrogen gas generated when the operating temperature was changed. Nafion was produced in Comparative Example 1, hBN/Nafion was produced in Example 2, and Graphene/Nafion was produced by the water electrolysis stack according to Example 1. This is the result of isotope separation. Referring to the graph on the left of FIG. 6, as the operating temperature increased, the content of deuterium in the generated gas increased, so it was confirmed that the lower the temperature, the better the separation efficiency. Rather than Comparative Example 1 using only the Nafion electrolyte membrane, the hBN or graphene ion separation membrane was used. It was found that Examples 1 and 2, which used a composite membrane-electrode composite together, separated deuterium more effectively. Additionally, comparing Example 1 and Example 2, it was found that graphene had better resolution than hBN.

The graph on the right side of Figure 6 is a graph showing the D/H separation coefficient of each experimental result.

The D/H separation coefficient was defined as the concentration of deuterium in the residual liquid (distilled water) compared to the concentration of deuterium in the generated gas. Referring to the graph on the right side of FIG. 6, like the graph on the left side of FIG. 6, it was confirmed that the case where a composite membrane was used compared to the case where a Nafion membrane alone was used, and in particular, when a graphene membrane was used rather than hBN, better separation performance was observed. Specifically, it was found that the examples had a separation coefficient that was improved by about 1.5 to 2 times compared to the comparative examples.

Experimental Example 2: Evaluation of hydrogen/tritium resolution

After adding distilled water to the water tank, the water is circulated to the anode side of the water electrolysis cell based on the composite membrane-electrode complex including the hydrogen ion separation layer using a liquid transfer pump, and the power supply is used to circulate the water at 0.28 A/ Current was supplied to make it ㎠. The water electrolysis cell was operated at room temperature.

The moisture contained in the hydrogen gas generated from the cathode was recovered through a cooling device, the tritium concentration of the hydrogen gas was measured using an ion chamber analyzer, and the tritium concentration of the water generated from the water tank and cathode was Quantitative analysis was performed using a liquid scintillation counter.

Figure 8 shows an example of separation of light hydrogen in the form of hydrogen gas from 4.6 MBq/L of tritium water through a separation device, and shows the results of real-time analysis of the content of tritium in the generated hydrogen gas using an ion chamber (for 1 hour). Operated at 0.28 A/cm2 at room temperature)

Referring to FIG. 8, the results of Examples 1 and 2 (expressed as Graphene/Nafion and hBN/Nafion, respectively) have a lower content of tritium in the generated gas compared to the separation results (expressed as Nafion) according to the comparative example. When observed to have superior resolution, it was confirmed in this experiment that the resolution in Example 1 using the graphene-Nafion composite membrane was the best.

In addition, when light hydrogen was separated into hydrogen gas form from 4.6 MBq/L of tritium water through a separation device, the tritium concentration (W _cathode ) in the permeate water generated at the cathode and the tritium concentration in the water tank after reaction ( W _Rf ), overall separation coefficient (β(T/H) ^total or β ^total = (W _Rf /G) ) and cathode separation coefficient (β(T/H) ^cathode or β ^cathode = (W _cathode /G) )) are shown in Table 1 below, respectively.

W _Rf (MBq/L) W _Rf (MBq/L) W _cathode (MBq/L) G(kBq/㎥) β ^total β ^cathode Example 1 4.68±0.05 4.71±0.05 5.06±0.06 271.89±0.11 12.78±0.37 13.71±0.40 Example 2 4.69±0.55 4.72±0.04 5.07±0.08 327.40±0.01 10.61±0.37 13.71±0.40 Comparative Example 1 4.62±0.12 4.66±0.12 4.94±0.12 484.08±0.02 7.08±0.16 7.52±0.20

Referring to Table 1 above, it was confirmed that when hydrogen isotopes were separated using the water electrolysis composite cell according to Examples 1 and 2, the tritium concentration (G) in the generated gas was lowered. In addition, the tritium concentration of the permeated water generated from the cathode (W _cathode ) is higher than the tritium concentration (W _Rf ) in the water tank after reaction, and the water generated from the cathode is passed through an additional separation device. The concentration of cases could be increased.

In addition, it was found that the overall separation coefficient (β ^total ) and cathode separation coefficient β ^cathode were improved by up to 1.82 times in the separation method according to Examples 1 and 2 compared to the separation method according to Comparative Example 1. .

Figures 9a and 9b are graphs showing comparative results of the hydrogen/tritium separation method by water electrolysis according to Example 1 and Comparative Example 1, respectively. Figure 9a specifically compares the tritium content in the generated gas, and Figure 9b specifically compares the cathode separation coefficient in real time. Referring to Figures 9a and 9b, it was seen that as the separation was performed for 8 hours, the tritium in the water tank gradually increased, and the content of tritium in the gas also slightly increased accordingly, but the separation coefficient remained constant. It has been done.

100: Hydrogen ion conductive polymer electrolyte membrane
110: Ion separation membrane
121: anode
121': Inlet
121”: outlet
122: cathode
122”: outlet

Claims (10)

A composite membrane for water electrolysis comprising a semi-permeable ion separation membrane having a difference in permeability to hydrogen ion isotopes and a hydrogen ion conductive polymer electrolyte membrane formed on at least one surface of the ion separation membrane; and
An anode catalyst formed opposite to both sides of the composite membrane for water electrolysis and a cathode catalyst for inducing hydrogen isotope exchange; comprising
Composite membrane-electrode complex for hydrogen isotope separation by water electrolysis.
According to paragraph 1,
A composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, wherein the semi-permeable ion separation membrane is a two-dimensional crystal material.
According to paragraph 2,
The two-dimensional crystal materials include graphene, hexagonal boron nitride (hBN), borophene, graphene, graphdiyne, phyllosilicate, and gC. A composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, characterized in that it is one or more selected from ₃ N ₄ , black phosphorus, transition metal oxide, and layered double hydroxide.
According to paragraph 2,
The semi-permeable ion separation membrane is a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, characterized in that the two-dimensional crystal material has a structure in which 1 to 100 layers are stacked.
According to paragraph 4,
The semi-permeable ion separation membrane is a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, wherein each layer consists of one continuous layer of the two-dimensional crystal material.
According to paragraph 4,
The semi-permeable ion separation membrane is a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis, characterized in that the flakes of the two-dimensional crystal material with a surface diameter of 10 nm to 100 ㎛ are aggregated.
According to paragraph 1,
The hydrogen ion conductive polymer membrane is selected from sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, polybenzimidazole, sulfonated polyether ether ketone (PEEK), and polysulfone. A complex for hydrogen isotope separation by water electrolysis, characterized in that it contains one or more selected substances.
Hydrogen ion conductive polymer electrolyte membrane; and
It includes a composite membrane for water electrolysis in which a two-dimensional crystal material having permeability to hydrogen ions is dispersed in the hydrogen ion conductive polymer electrolyte membrane,
An anode catalyst formed on both sides of the water electrolysis composite membrane to face each other; And a cathode catalyst that induces hydrogen isotope exchange.
Composite membrane-electrode complex for hydrogen isotope separation by water electrolysis.
Including a composite membrane-electrode complex for hydrogen isotope separation by water electrolysis according to claim 1 or 8,
The composite membrane-electrode complex for hydrogen isotope separation by water electrolysis has an inlet for injecting water near the anode and an outlet for oxygen (O ₂ ) and unreacted water generated by the oxidation-reduction reaction. A hydrogen isotope separation system that includes an outlet for hydrogen (H ₂ ) generated by an oxidation-reduction reaction near the cathode.
A method of separating light hydrogen (H, hydrogen) contained in water (H ₂ O) from heavy hydrogen (D, Deuterium) and tritium (T, Tritium) using the hydrogen isotope separation system according to claim 9,
Injecting water containing deuterium and tritium through an inlet near the anode; and
A voltage is applied between the anode and the cathode to perform an oxygen generation reaction at the anode, and the hydrogen ions generated as a result of the oxygen generation reaction are attracted by electric force and move to the cathode. A hydrogen isotope separation method comprising the step of passing through the ion separation membrane, reaching the cathode, causing a hydrogen generation reaction, and generating hydrogen gas having a light hydrogen mole fraction concentrated compared to the light hydrogen mole fraction in the input water.