Water electrolysis separation membrane comprising hydrogen-oxygen recombination reaction catalyst

Abstract

The water electrolysis separation membrane according to the present invention comprises a support mesh and a functional layer in which the support mesh is included, wherein the functional layer includes an ion-conducting material and a hydrogen-oxygen recombination catalyst.

Description

Water electrolysis membrane containing a hydrogen-oxygen recombination reaction catalyst

[0001] The present invention relates to a water electrolysis membrane capable of preventing gas diffusion by including a hydrogen-oxygen recombination reaction catalyst.

[0002] Water electrolysis is a technology that decomposes water using electrical energy obtained from various energy sources. Because the products of the electrolysis reaction are hydrogen and oxygen and there are no carbon dioxide emissions, it is one of the core technologies of the deoxygenation industry. A water electrolysis system includes a control unit that supplies water or electrolyte solution and manages power, a stack that produces hydrogen, a gas-liquid separator and gas purification device, and a hydrogen storage tank. Among these components, the stack is considered the most critical part as it is responsible for hydrogen production.

[0003] A cell, which is the basic unit of a stack, includes a cathode where hydrogen evolution occurs, an anode where oxygen evolution occurs, and a separator that separates the zones between them. The separator serves to prevent the gases generated at the cathode and anode from mixing. Additionally, it is desirable for the separator to have a small pore size while rapidly moving ions along the ion transport pathway. Furthermore, considering that 2 moles of water produce 2 moles of hydrogen and 1 mole of oxygen when decomposed, the amount of hydrogen produced at the cathode is twice the amount of oxygen produced, resulting in a pressure difference; therefore, the membrane must possess mechanical strength to withstand this pressure difference.

[0004] To form an eco-friendly energy system, renewable energy sources such as solar and wind power can be used as energy sources to drive water electrolysis systems. However, renewable energy sources such as solar and wind power exhibit significant output fluctuations due to climate change, making it difficult to supply a constant current. In this case, situations where a current lower than the rated current is supplied may occur frequently, which can lead to a decrease in hydrogen production. Furthermore, in low-power regions, oxygen generation decreases while the amount of hydrogen passing through the membrane remains constant, resulting in a period where the hydrogen concentration at the oxygen electrode rises rapidly. Since there is a risk of explosion when the hydrogen concentration at the oxygen electrode increases to 4 mol% or higher, it is necessary to develop a separator capable of suppressing hydrogen crossover to prevent this.

[0005] The objective of the present invention is to provide a water electrolysis membrane capable of preventing a decrease in the purity of hydrogen or oxygen produced by gas permeation through the membrane and preventing explosions caused by the mixing of hydrogen and oxygen.

[0006] A water electrolysis separation membrane according to the present invention comprises a support mesh; and a functional layer containing the support mesh; wherein the functional layer comprises an ion-conducting material and a hydrogen-oxygen recombination catalyst.

[0007] A water electrolysis membrane according to one embodiment of the present invention may be characterized by having a thickness of 100 to 500 μm.

[0008] In a water electrolysis separation membrane according to one embodiment of the present invention, the hydrogen-oxygen recombination catalyst may be characterized by comprising a support and a metal catalyst.

[0009] In a water electrolysis separation membrane according to one embodiment of the present invention, the support material may include one or more selected from alumina, zeolite, ceria, titanium dioxide, and silica.

[0010] In a water electrolysis membrane according to one embodiment of the present invention, the metal catalyst may be characterized by comprising one or more selected from platinum, palladium, ruthenium, rhodium, iridium, nickel, copper, and alloys thereof.

[0011] In a water electrolysis separation membrane according to one embodiment of the present invention, the hydrogen-oxygen recombination catalyst may be characterized by containing 0.05 to 2 weight percent of a metal catalyst.

[0012] A water electrolysis separator according to one embodiment of the present invention may be characterized by comprising 75 to 95 weight percent of a support mesh and the remainder being a functional layer.

[0013] In a water electrolysis separation membrane according to one embodiment of the present invention, the functional layer may further include a binder.

[0014] In a water electrolysis membrane according to one embodiment of the present invention, the functional layer may be characterized by comprising 300 to 500 parts by weight of a binder and 0.5 to 10 parts by weight of a hydrogen-oxygen recombination catalyst per 100 parts by weight of an ion-conducting material.

[0015] The present invention also provides a method for manufacturing a separator for water electrolysis, wherein the separator for water electrolysis according to the present invention comprises a first step of preparing a functional layer paste by mixing an ion-conducting material, a binder, an auxiliary binder, a hydrogen-oxygen recombination catalyst, and an organic solvent;

[0016] A second step of immersing a support mesh in the functional layer paste, coating the functional layer paste onto the support mesh, and removing the solvent; and

[0017] It includes a third step of removing the auxiliary binder by immersing the product of the second step in an alcohol solvent.

[0018] In a water electrolysis separation membrane according to one embodiment of the present invention, the auxiliary binder may be polyvinylpyrrolidone.

[0019] In a water electrolysis membrane according to one embodiment of the present invention, the auxiliary binder may be added in an amount of 0.02 to 0.08 moles relative to 1 mole of the ion-conducting material.

[0020] The water electrolysis membrane according to the present invention comprises a support mesh; and a functional layer containing the support mesh; wherein the functional layer comprises an ion-conducting material and a hydrogen-oxygen recombination catalyst, thereby preventing a decrease in the purity of hydrogen or oxygen produced by gas permeation through the membrane and preventing an explosion caused by the mixing of hydrogen and oxygen.

[0021] Figure 1 is a schematic diagram illustrating the phenomenon occurring in the membrane during a water electrolysis reaction when using a membrane for water electrolysis according to one embodiment of the present invention and when using a general membrane for water electrolysis.

[0022] Figure 2 illustrates the shape of a membrane according to the content of a hydrogen-oxygen recombination catalyst in a water electrolysis membrane according to one embodiment of the present invention, observed visually.

[0023] Figure 3 illustrates a comparative observation of a water electrolysis membrane according to one embodiment of the present invention and a commercially available membrane using a Scanning Electron Microscope (SEM).

[0024] Figure 4 illustrates a water electrolysis membrane according to one embodiment of the present invention, observed using a Transmission Electron Microscope (TEM).

[0025] Figure 5 shows the results of measuring the oxygen concentration of the hydrogen electrode in a cell with a water electrolysis membrane applied according to one embodiment and a comparative example of the present invention.

[0026] Figure 6 shows the results of measuring the voltage load of a cell with a water electrolysis membrane applied according to one embodiment and a comparative example of the present invention.

[0027] The advantages and features of the embodiments of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0028] In describing the embodiments of the present invention, specific descriptions of known functions or configurations will be omitted if it is determined that such detailed descriptions could unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined in consideration of their functions in the embodiments of the present invention, and these definitions may vary depending on the intentions or practices of the user or operator. Therefore, such definitions should be based on the content throughout this specification.

[0029] The water electrolysis separator according to the present invention comprises a support mesh; and

[0030] The above support mesh includes a functional layer contained therein; and

[0031] The above functional layer is characterized by comprising an ion-conducting material and a hydrogen-oxygen recombination catalyst.

[0032] The water electrolysis membrane according to the present invention has the advantage of primarily blocking gas movement between the hydrogen electrode and the oxygen electrode, while simultaneously preventing the loss of active sites caused by intermediates permeating through the membrane by including a hydrogen-oxygen recombination catalyst and preventing gas permeation.

[0033] Figure 1 is a schematic diagram illustrating the phenomena occurring in the membrane during a water electrolysis reaction. When it becomes difficult for the oxygen generation reaction to occur in the low-power range, intermediates such as O·, HO·, and HOO· are easily adsorbed onto ion-conducting active sites and lost, as shown in Figure 1a, and there is also a risk of gas permeation. When a hydrogen-oxygen recombination catalyst is included as shown in Figure 1b, intermediate products such as HOO· are stabilized via the pathway shown in Equation 1 below, and hydrogen ions can be supplied. Additionally, the hydrogen-oxygen recombination reaction occurs in the membrane via the pathway shown in Equation 2 below, which re-reacts gases passing through the membrane, thereby preventing gas permeation.

[0034] [Reaction Equation 1]

[0035] H2O + · → HO· + e - + H +

[0036] HO· → O· + e- + H +

[0037] H2O + O· → HOO· + e- + H +

[0038] HOO· → O2+ e- + H +

[0039] [Reaction Equation 2]

[0040] O· + H· → HO·

[0041] HO· + H· → H2O·

[0042] H2O· + O· → 2HO·

[0043] Consequently, the separation membrane according to the present invention has the advantage of not only physically blocking gas diffusion but also chemically blocking gas diffusion through hydrogen-oxygen recombination.

[0044]

[0045] The above hydrogen-oxygen recombination catalyst may include a support and a metal catalyst, and high catalytic activity can be secured by supporting the metal catalyst within the support.

[0046] The support material may use one or more selected from alumina, zeolite, ceria, titanium dioxide, and silica, preferably one or more selected from alumina, zeolite, ceria, and titanium dioxide, and more preferably alumina or zeolite.

[0047] A metal catalyst capable of inducing hydrogen-oxygen recombination can be used, specifically one or more selected from platinum, palladium, ruthenium, rhodium, iridium, nickel, copper, and alloys thereof. By using such a metal catalyst, intermediates can be stabilized as in the above-described reaction schemes 1 and 2 to prevent gas permeation and increase the purity of the produced hydrogen or oxygen.

[0048] The hydrogen-oxygen recombination catalyst may contain 0.05 to 2 weight%, preferably 0.1 to 1 weight%, and more preferably 0.2 to 0.8 weight% of a metal catalyst. If the content of the metal catalyst is low, it may be difficult to achieve sufficient catalytic activity for hydrogen-oxygen recombination, and if the content of the metal catalyst is high, the catalytic activity may not increase further, while causing an increase in the production cost of the separation membrane.

[0049]

[0050] A water electrolysis separator according to one embodiment of the present invention may comprise 75 to 95 weight%, preferably 78 to 90 weight%, of a support mesh and may comprise the remainder being a functional layer, and the functional layer will be described in detail below.

[0051] The functional layer may include an ion-conducting material and a hydrogen-oxygen recombination catalyst, and may additionally include a binder. In this case, the ion-conducting material may include one or more selected from zirconia, zirconia composites, alumina, ceria, titanium dioxide, Nafion, Abiquione, sulfonated polyether ketones, metal-organic frameworks (MOFs), spinel structure metal oxides, and perovskite structure metal oxides, and preferably, one or more selected from zirconia, zirconia composites, alumina, ceria, and titanium dioxide may be used, wherein the zirconia composite refers to a composite formed by mixing one or more selected from alumina, ceria, and titanium dioxide with zirconia.

[0052] When zirconia, zirconia composites, alumina, ceria, and titanium dioxide are used as ion-conducting materials, their average particle size may be 5 to 150 nm, preferably 7 to 100 nm, and the separator membrane has the characteristic of having high ion conductivity and mechanical strength by satisfying this average particle size.

[0053]

[0054] The above functional layer includes a hydrogen-oxygen recombination catalyst, and as described above, the separation membrane is characterized by chemically blocking gas movement in the separation membrane by including a hydrogen-oxygen recombination catalyst (hereinafter referred to as the catalyst or recombination catalyst). The above functional layer may include 0.5 to 10 parts by weight, preferably 0.7 to 7 parts by weight, and more preferably 1 to 5 parts by weight of a hydrogen-oxygen recombination catalyst per 100 parts by weight of an ion-conducting material, and if the content of the hydrogen-oxygen recombination catalyst is low or high, problems such as surface defects may occur during the manufacture of the separation membrane in terms of the manufacturing method.

[0055]

[0056] The above functional layer may include a binder to bind an ion-conducting material and a hydrogen-oxygen recombination catalyst, thereby forming a separation membrane. Specifically, polystyrene may be used as the binder, and the functional layer may contain 300 to 500 parts by weight, preferably 350 to 450 parts by weight, of the binder relative to 100 parts by weight of the ion-conducting material. If the proportion of the binder is high, it may be difficult to exhibit sufficient ion conductivity and hydrogen-oxygen recombination catalyst activity, and if the proportion of the binder is low, there is a limitation in that it is difficult to secure sufficient durability and mechanical strength.

[0057]

[0058] The water electrolysis membrane is required to exhibit high stability even under the pressure difference that occurs between the hydrogen electrode and the oxygen electrode during the operation of the water electrolysis cell, and this stability can be secured by including a support mesh within the functional layer.

[0059] The support mesh may utilize a resin-based mesh. Specifically, the mesh may comprise one or more selected from polyphenylene sulfide, polyether sulfone, and polytetrafluoroethylene, and preferably, a polyphenylene sulfide mesh may be used. By using such a mesh, it is possible to secure mechanical strength above a certain level while preventing the problem of reduced ion permeability caused by the membrane becoming excessively thick.

[0060] A water electrolysis membrane according to one embodiment of the present invention may have a thickness of 100 to 500 μm, preferably 120 to 400 μm. If the thickness of the membrane becomes excessively thick, the ion permeability may decrease, and if the thickness of the membrane becomes excessively thin, it is difficult to exhibit mechanical strength above a certain level, and the inhibition rate of gas permeation is lowered, which lowers the purity of the product and increases the risk of accidents such as explosions.

[0061]

[0062] The present invention also provides a method for manufacturing a separation membrane for water electrolysis.

[0063] A method for manufacturing a water electrolysis membrane according to the present invention comprises a first step of preparing a functional layer paste by mixing an ion-conducting material, a binder, an auxiliary binder, a hydrogen-oxygen recombination catalyst, and an organic solvent;

[0064] A second step of immersing a support mesh in the functional layer paste, coating the functional layer paste onto the support mesh, and removing the solvent; and

[0065] It includes a third step of removing the auxiliary binder by immersing the product of the second step in an alcohol solvent.

[0066] In the first step, the support mesh, ion-conducting material, binder, and hydrogen-oxygen recombination catalyst may be the same or similar as the water electrolysis membrane described above. In addition, the organic solvent may be used without limitation as long as it is a solvent capable of dissolving the binder and the auxiliary binder; specifically, an acetamide-based solvent may be used, and more specifically, dimethylacetamide may be used as the organic solvent.

[0067] In the first step, the auxiliary binder may specifically be polyvinylpyrrolidone, and the auxiliary binder including polyvinylpyrrolidone may be removed using an alcohol solvent in the third step. The auxiliary binder may be included in an amount of 0.02 to 0.08 moles, preferably 0.03 to 0.06 moles, relative to 1 mole of ion-conducting material; if the content of the auxiliary binder is excessively low, it may be difficult to form a separation membrane, and if the content of the auxiliary binder is excessively high, there is a risk of gas permeation occurring due to an excessive number of pores in the separation membrane after the third step. The alcohol in the third step may preferably be a monovalent alcohol with 5 or fewer carbon atoms, preferably a monovalent alcohol with 3 or fewer carbon atoms, or a mixture of these alcohols.

[0068] In the second step, a structure can be formed in which the support mesh is contained within the functional layer by immersing the support mesh in the functional layer paste and then performing a coating on the support mesh. The coating in the second step can be applied without limitation as long as it is a method of introducing the functional layer paste, and specifically, methods such as bar coating, doctor blade coating, slot die coating, slurry casting, or roll coating can be used. The coating in the second step can be applied to satisfy a thickness of 100 to 500 μm after solvent removal by drying, and specifically, it can be coated to a thickness of 150 to 700 μm to form a functional layer of appropriate thickness through solvent removal.

[0069]

[0070] The present invention will be explained in detail below through examples and comparative examples. The following examples are intended only to aid in understanding the present invention, and the scope of the present invention is not limited by the following examples.

[0071] [Preparation Example]

[0072] Zirconia powder with an average particle size of about 10 to 50 nm was prepared. 80 g of polystyrene, 1.9 g of polyvinylpyrrolidone with a weight-average molecular weight of about 29,000 (about 0.04 mol per 1 mol of zirconia), and 0.5 g of a hydrogen-oxygen recombination catalyst were mixed relative to 20 g of zirconia powder. At this time, the hydrogen-oxygen recombination catalyst used was a catalyst in which about 0.5 wt% of palladium particles with an average particle size of about 4 nm were supported on an alumina support. 500 ml of diethylacetamide solvent was added to this mixture, and stirring was carried out at 70 °C until completely dissolved to prepare a functional layer paste.

[0073] Separately, a polyphenylene sulfide mesh with a single fiber diameter of 30 to 70 μm was prepared, and the mesh was immersed in a functional layer paste. After immersion, the functional layer paste was coated onto the mesh via bar coating to a thickness of 300 μm before solvent evaporation, and then dried to remove the solvent. After drying, the mesh was immersed in a mixed solvent of isopropyl alcohol and ethanol in a 1:1 volume ratio to remove polyvinylpyrrolidone, thereby finally manufacturing a separation membrane.

[0074]

[0075] [Comparative Manufacturing Example]

[0076] A commercially available separator product (Zirfon PERL) was prepared and used in the experiment.

[0077]

[0078] Observation of the morphology of the final membrane according to the amount of hydrogen-oxygen recombination catalyst added

[0079] In the case of the preparation example, 20 g of zirconia powder and 0.5 g of hydrogen-oxygen recombination catalyst were added, with 2.5 parts by weight of hydrogen-oxygen recombination catalyst added per 100 parts by weight of zirconia powder. Then, the content of the hydrogen-oxygen recombination catalyst was changed to 0.5 parts by weight and 6 parts by weight per 100 parts by weight of zirconia powder, respectively, and a functional layer paste was prepared in the same manner as in the preparation example, and a separation membrane was prepared using the paste.

[0080] The prepared membranes were observed visually, and the results are shown in FIG. 2. In FIG. 2, a and b are membranes prepared by adding 0.5 parts by weight of a hydrogen-oxygen recombination catalyst, c and d are preparation examples, and e and f are membranes prepared by adding 6 parts by weight of a hydrogen-oxygen recombination catalyst.

[0081] Referring to Figure 2, it can be seen that defects occur during the membrane formation process when the content of the hydrogen-oxygen recombination catalyst is low or high, whereas in the case of the example, a uniform membrane is formed without defects.

[0082]

[0083] Observation of separation membrane

[0084] The separator prepared in the example and the separator of the comparative example were observed using a Scanning Electron Microscope (SEM), and the results are shown in Fig. 3. In Fig. 3, a is the separator of the comparative example, and b is the separator prepared in the example.

[0085] Referring to Fig. 3, it can be seen that the separator of the manufacturing example has a final thickness of about 190 to 220 μm after bar-coating the functional layer paste to 300 μm and evaporating the solvent, and it can be seen that the polyphenylene sulfide mesh supports the separator inside the separator.

[0086] In addition, when compared to the membrane of the comparative example, it can be confirmed that the membrane of the example formed a denser membrane, which can be attributed to the improvement in wettability resulting from the addition of the hydrogen-oxygen recombination catalyst.

[0087]

[0088] Figure 4 shows the separator prepared in the preparation example observed using a Transmission Electron Microscope (TEM). Referring to Figure 4, it can be seen that palladium particles with a particle size of about 4 nm are well supported inside.

[0089]

[0090] Applied to water electrolysis cells

[0091] The oxygen generating electrode (anode) utilized a nickel-iron (NiFe) layered double hydroxide, and the hydrogen generating electrode (cathode) utilized nickel foam; the active area of ​​each electrode was 25 cm². 2The electrolyte was a 25 wt% aqueous KOH solution, and the cell was constructed using a separator prepared in the preparation example or comparative preparation example. The experiment was conducted by operating the constructed cell at a temperature of 80 ℃.

[0092] 0.6 A / cm 2 The oxygen concentration of the gas discharged from the hydrogen electrode was measured as a result of operating the cell at a current density, and the results are shown in Fig. 5. In Fig. 5, a is the comparative manufacturing example and b is the case where the separator of the manufacturing example was applied. Referring to Fig. 5, it can be seen that when the separator prepared in the manufacturing example was applied, the oxygen concentration was 100 ppm or less after 300 hours, whereas when the separator of the comparative manufacturing example was applied, the oxygen concentration was 550 to 700 ppm after 300 hours. It can be seen that when the separator of the manufacturing example contains a hydrogen-oxygen recombination catalyst and the separator of the comparative manufacturing example is applied, the oxygen concentration is more than 5 times higher.

[0093] The previously manufactured cell at a current density of 0 to 1.2 A / cm² 2 The voltage change was measured while varying the values, and the results are shown in Fig. 6. Referring to Fig. 6, it can be seen that the separator prepared in the example exhibits a similar voltage load compared to the commercially available separator in the comparative example, and accordingly, it can be seen that the hydrogen-oxygen recombination catalyst does not cause a degradation in the performance of the electrolytic cell.

Claims

1. Support mesh; and The above support mesh includes a functional layer contained therein; and A water electrolysis membrane characterized by the above functional layer comprising an ion-conducting material and a hydrogen-oxygen recombination catalyst.

2. In Paragraph 1, The above-described water electrolysis separator is characterized by having a thickness of 100 to 500 μm.

3. In Paragraph 1, A water electrolysis separation membrane characterized by the above hydrogen-oxygen recombination catalyst comprising a support and a metal catalyst.

4. In Paragraph 3, A water electrolysis separation membrane characterized by comprising one or more of the above-mentioned support material selected from alumina, zeolite, ceria, titanium dioxide, and silica.

5. In Paragraph 3, A water electrolysis separator characterized by comprising one or more metal catalysts selected from platinum, palladium, ruthenium, rhodium, iridium, nickel, copper, and alloys thereof.

6. In Paragraph 3, A water electrolysis separator characterized by the above hydrogen-oxygen recombination catalyst containing 0.05 to 2 weight percent of a metal catalyst.

7. In Paragraph 1, The above-described water electrolysis separator is characterized by comprising 75 to 95 weight percent of a support mesh and the remainder being a functional layer.

8. In Paragraph 1, A water electrolysis separator characterized by the above functional layer further including a binder.

9. In Paragraph 8, A water electrolysis separator characterized by the above functional layer comprising 300 to 500 parts by weight of a binder and 0.5 to 10 parts by weight of a hydrogen-oxygen recombination catalyst per 100 parts by weight of an ion-conducting material.

10. A first step of preparing a functional layer paste by mixing an ion-conducting material, a binder, an auxiliary binder, a hydrogen-oxygen recombination catalyst, and an organic solvent; A second step of immersing a support mesh in the functional layer paste, coating the functional layer paste onto the support mesh, and removing the solvent; and A method for manufacturing a separator for water electrolysis, comprising: a third step of immersing the product of the second step above in an alcohol solvent to remove an auxiliary binder.

11. In Paragraph 10, A method for manufacturing a water electrolysis membrane characterized in that the above auxiliary binder is polyvinylpyrrolidone.

12. In Paragraph 10, A method for manufacturing a water electrolysis membrane characterized by adding 0.02 to 0.08 moles of the auxiliary binder per 1 mole of the ion-conducting material.

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