Electrode ink for water electrolysis, electrode comprising same for water electrolysis, and membrane electrode assembly for water electrolysis

Abstract

An electrode ink for water electrolysis of the present invention comprises: a catalyst for water electrolysis; silica nanoparticles; and an ionomer, wherein the silica nanoparticles are included in an amount of 5 to 40 wt% (based on solids content) in the total electrode ink for water electrolysis.

Description

Water electrolysis electrode ink, a water electrolysis electrode including the same, and a membrane electrode assembly for water electrolysis

[0001] The present invention relates to a water electrolysis electrode ink, a water electrolysis electrode containing the same, and a membrane electrode assembly for water electrolysis. More specifically, the present invention relates to a water electrolysis electrode ink having excellent electrical conductivity, anion exchange membrane water electrolysis performance and durability, and improved coating properties and surface characteristics, a water electrolysis electrode containing the same, and a membrane electrode assembly for water electrolysis.

[0002] In the current climate where the development of eco-friendly fuels is a major topic, water electrolysis is the only commercially available technology capable of producing the most perfectly green hydrogen. Water electrolysis technology is divided into three types: Proton Exchange Membrane Electrolysis Cell (PEMEC), Alkaline Electrolysis Cell (AEC), and Solid Oxide Electrolysis Cell (SOEC). As AEC has a history spanning over 100 years, it is a mature field in both market and technology; consequently, it is difficult to expect significant reductions in equipment production and operating costs through technological development. Furthermore, due to the low hydrogen production density of AEC, producing large volumes of hydrogen inevitably requires scaling up production and consequently increasing the size of equipment, making it difficult to ensure economic viability. PEMEC is a relatively recently commercialized technology that can directly produce high-purity, high-pressure hydrogen in compact facilities, and offers significant potential for reducing production and operating costs through technological development. However, as this is a recently commercialized technology, long-term operating data has not been secured, making it difficult to guarantee stability. Furthermore, the cost and processing expenses of the separator (or bipolar plate) materials, which are inevitably required under acidic operating conditions, account for a significant portion of production costs and can act as a burden. SOEC has the unique advantage of being usable as either an electrolyzer or a fuel cell with the same configuration, depending on the operating method. However, there are limitations: the solid oxide catalyst is susceptible to physical shock, limiting its stable application to stationary facilities; and the extremely high temperature of the water used in the process necessitates installation near sites where ultra-high temperature water is generated, such as steel mills or nuclear power plants.

[0003] Accordingly, anion exchange membrane electrolysis (AEMEC) is being proposed as an alternative to solve the problems of existing water electrolysis methods. AEMEC has the advantage of enabling high-density hydrogen production similar to the hydrogen production density of PEMEC, resulting in a small facility size, and low production costs because it utilizes AEC materials.

[0004] Conventionally, when manufacturing anion exchange membrane water electrolysis MEA, heat and pressure during the process of transferring the electrode layer to the electrolyte membrane caused most of the pores of the electrode layer to be lost, reducing the active area, which in turn reduced mass transfer and caused performance degradation.

[0005] Therefore, there is a need to develop an electrode ink that can maintain excellent active area and mass transfer without the loss of pores in the electrode layer even after electrode fabrication.

[0006] Related prior art is KR 10-2018-0121004.

[0007] The objective of the present invention is to provide a water electrolysis electrode ink capable of improving the performance of a water electrolyzer by increasing the specific surface area and enhancing mass transfer.

[0008] Another objective of the present invention is to provide a water electrolysis electrode ink that can improve the performance of a water electrolyzer by having a high specific surface area and porosity even when heat and pressure are applied after transfer to an electrolyte membrane.

[0009] Another objective of the present invention is to provide a water electrolysis electrode comprising the above-mentioned water electrolysis electrode ink and a membrane electrode assembly for water electrolysis using the same.

[0010] The above and other objectives of the present invention can all be achieved by the present invention described below.

[0011] 1. One aspect of the present invention relates to a water electrolysis electrode ink. The water electrolysis electrode ink comprises a water electrolysis catalyst; silica nanoparticles; and an ionomer; wherein the silica nanoparticles comprise about 5 to 40 weight percent (based on solid content) of the total water electrolysis electrode ink.

[0012] 2. In the above 1 embodiment, the water electrolysis catalyst may have a spinel crystal structure.

[0013] 3. In the above 1 to 2 embodiments, the water electrolysis catalyst may have an average particle size (D50) of about 3 to 5 μm.

[0014] 4. In the above 1 to 3 embodiments, the silica nanoparticles may have an average particle size (D50) of about 100 to 1000 nm.

[0015] 5. In the above 1 to 4 embodiments, the water electrolysis electrode ink may comprise about 5 to 40 weight% of silica nanoparticles based on solid content; and about 1 to 15 weight% of ionomer.

[0016] 6. In the above 1 to 5 embodiments, the water electrolysis electrode ink may further contain about 50 to 90 weight percent of solvent.

[0017] 7. In the above 1 to 6 embodiments, the solvent may include one or more of water, alcohol, acetone, ethylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and acetonitrile.

[0018] 8. Another aspect of the present invention relates to a water electrolysis electrode. The water electrolysis electrode comprises the water electrolysis electrode ink of embodiments 1 to 7.

[0019] 9. In the above 8 embodiments, the electrode may have pores of about 100 to 1000 nm in mercury porosity measurements.

[0020] 10. In the above 8 to 9 embodiments, the electrode may be porous and have an interconnected structure.

[0021] 11. Another aspect of the present invention relates to a membrane electrode assembly for water electrolysis. The membrane electrode assembly for water electrolysis comprises an electrolyte membrane; and an electrode layer formed on the surface of the electrolyte membrane; wherein the electrode layer is formed from the water electrolysis electrode ink of embodiments 1 to 7.

[0022] 12. In the above 11 embodiment, the electrode layer may have pores of about 100 to 1000 nm as measured by mercury porosity measurement.

[0023] 13. Another aspect of the present invention relates to a method for manufacturing a membrane electrode assembly for water electrolysis. The method comprises the steps of: coating the water electrolysis electrode ink onto a polymer film to form an electrode layer; and transferring the electrode layer onto the surface of an electrolyte membrane.

[0024] The present invention has the effect of providing a water electrolysis electrode ink that can improve water electrolysis performance by increasing the specific surface area and enhancing mass transfer, and can improve water electrolysis performance by maintaining a high specific surface area and porosity even when heat and pressure are applied after transfer to an electrolyte membrane, a water electrolysis electrode including the same, a membrane electrode assembly for water electrolysis using the same, and a method for manufacturing the same.

[0025] Figure 1 is a graph of log differential intrusion (mL / g) according to pore size of the examples and comparative examples.

[0026] Figure 2 is the current-voltage characteristic curve (IV characteristic curve) of the example and comparative example.

[0027] The present invention will be described in more detail below. Where terms such as 'comprising,' 'having,' and 'consisting of' are used in this specification, other parts may be added unless 'only' is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0028] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0029] The water electrolysis electrode ink according to the present invention will be described in detail below.

[0030]

[0031] Water electrolysis electrode ink

[0032] The water electrolysis electrode ink of the present invention comprises a water electrolysis catalyst; silica nanoparticles; and an ionomer; and contains about 5 to 40 weight percent of silica nanoparticles based on solid content.

[0033] (a) Water electrolysis catalyst

[0034] The above water electrolysis catalyst may have a spinel crystal structure.

[0035] In a specific example, the water electrolysis catalyst may include a spinel-based oxide of the following chemical formula 1.

[0036] [Chemical Formula 1]

[0037] NiCo (2-x) M x O4

[0038] (In the above Chemical Formula 1, 0≤x≤0.5, and the metal (M) is one or more elements selected from the group consisting of Fe, Sc, Ti, V, Cr, Y, Zr, Nb, and Mo)

[0039] When a catalyst of the above structure is applied, excellent electrical conductivity, catalytic activity, and MEA coating properties can be exhibited, and a large surface area can be provided.

[0040] The above water electrolysis catalyst may have an average diameter (D50) of about 3 to 5 µm. For example, it may be 3 µm, 4 µm, and 5 µm. It has the advantage of having excellent water electrolysis performance within the above range.

[0041] In addition to the above-mentioned water electrolysis catalyst, electrochemical catalysts such as commercial Pt / C catalysts may also be used.

[0042]

[0043] (b) Silica nanoparticles

[0044] The silica nanoparticles above may have an average particle size (D50) of about 100 to 1000 nm. For example, it may be 150 to 950 µm or 200 to 900 µm. Within this range, a larger specific surface area and excellent porosity can be provided, and a water electrolysis electrode with a pore size of about 100 to 1000 nm can be secured. Within this range, excellent porosity can be maintained even when high heat and pressure are applied after transfer.

[0045] The above silica nanoparticles are included in the total water electrolysis electrode ink at about 5 to 40 weight percent (based on solid content). For example, it may be about 8 to 36 weight percent, or about 10 to 35 weight percent. If the above range is exceeded, there is a disadvantage that the quality of the electrode film deteriorates, and if applied at a range less than the above range, there is a problem that the porosity maintenance effect by the added nanoparticles is reduced.

[0046]

[0047] (c) Ionomer

[0048] The above ionomer may be a perfluorinated ionomer, a partially fluorinated ionomer, or a hydrocarbon ionomer, but is not necessarily limited thereto. Examples include polyperfluorosulfonic acid, polyperfluorocarboxylic acid, a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, PTFE-g-TFS, PVDF-g-PSSA, polysulfonated imide, etc.

[0049] The above ionomer is included in the total water electrolysis electrode ink at about 1 to 15 weight percent (based on solid content). For example, it may be about 2 to 14 percent, or about 3 to 13 percent. Within the above range, there is an advantage in that the physical properties of the water electrolysis ink and the water electrolysis performance can be optimized.

[0050]

[0051] The water electrolysis electrode ink of the present invention may further include a solvent and other conventional additives in addition to the above components.

[0052] In a specific example, the solvent may be water, alcohol, acetone, ethylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), acetonitrile, etc., but is not necessarily limited thereto. The solvent may be used alone or as a mixture of two or more types. The alcohol may include monohydric or dihydric alcohols. For example, methyl alcohol, isopropyl alcohol, etc. may be used. The solvent may be included in an amount of 50 to 90 weight percent of the total electrode ink.

[0053] The above additives include viscosity modifiers, leveling agents, etc., and may be included in an amount of 0.1 to 5 weight percent of the total electrode ink.

[0054]

[0055] The water electrolysis electrode ink of the present invention can be prepared by mixing a water electrolysis catalyst, silica nanoparticles, an ionomer, a solvent, and optionally other additive components.

[0056] The above water electrolysis electrode ink may have a viscosity of 1,000 to 2,000 cPs at 25°C. Excellent coating properties can be exhibited within the above range.

[0057]

[0058] Water electrolysis electrode and membrane electrode assembly

[0059] Another aspect of the present invention relates to a water electrolysis electrode. The water electrolysis electrode may be formed by including the water electrolysis electrode ink described above.

[0060] In one embodiment, the electrode may be formed by coating and drying the water electrolysis electrode ink. The coating may be spray coating, bar coating, doctor blade, roll-to-roll coil, impregnation coating, gravure coating, slot die coating, lip coating, etc., but is not necessarily limited thereto.

[0061] Another aspect of the present invention relates to a membrane electrode assembly for water electrolysis. The membrane electrode assembly for water electrolysis comprises an electrolyte membrane; and an electrode layer formed on the surface of the electrolyte membrane; wherein the electrode layer is formed from the water electrolysis electrode ink.

[0062] The above electrolyte membrane may preferably be an anion exchange membrane.

[0063] In one embodiment, the electrode layer can be formed by coating it onto a polymer film and then transferring it to an electrolyte membrane to bond it. In this case, bonding is performed by applying a temperature of about 80 to 180°C and a pressure of about 50 to 300 kgf. Conventionally, there is a problem in that pores are lost during this process, resulting in a decrease in specific surface area and reduced mass transfer performance, which leads to a decrease in the performance of the water electrolysis cell. In the present invention, by applying silica nanoparticles, the silica particles dissolve during water electrolysis operation, thereby maintaining the pores and securing excellent active surface area and mass transfer performance.

[0064] The electrode may have pores of approximately 100 to 1000 nm when measuring mercury porosity. For example, it may be 150 to 950 nm, or 200 to 900 nm. Additionally, the electrode may be porous and have an interconnected structure of pores.

[0065]

[0066] The present invention is to be explained more specifically below through examples and comparative examples; however, these examples are for illustrative purposes only and should not be interpreted as limiting the invention.

[0067] Examples

[0068] The specifications of each component used below are as follows:

[0069] (1) Water electrolysis catalyst: A spinel-based catalyst (NixCoy FezOa) manufactured by Hanwha Solutions Co., Ltd. was used.

[0070] (2) Ionomer: Nafion manufactured by 3M (Nafion product name: E-21669D Developmental Material) was used.

[0071] (3) Silica nanoparticles:

[0072] Silica nanoparticles with a diameter of 400 nm manufactured by US Research Nanomaterials, Inc. (Product name: Silicon Dioxide powder stock#:US1333M) were used.

[0073] (4) Solvent: A mixture of 31 wt% distilled water, 8 wt% IPA, 26 wt% acetonitrile, and 35 wt% methanol was used in the total solution.

[0074]

[0075] Example 1

[0076] Electrode ink was prepared by mixing and dispersing the components of the composition in Table 1, excluding silica particles, and then adding and dispersing silky particles to complete the electrode ink. The prepared electrode ink was bar-coated onto a PEN film to a thickness of 50 to 150 μm to form an electrode layer, and then transferred to an electrolyte membrane at a temperature of 150 °C and a pressure of 300 kgf to fabricate a membrane electrode assembly, after which the physical properties were evaluated by the following method. Mercury porosity was measured by immersing the membrane electrode assembly in 1 M KOH (water electrolysis conditions) for 1 day to remove silica particles. The results are shown in Table 1 and Figures 1-2, respectively.

[0077]

[0078] Comparative Example 1

[0079] The procedure was performed in the same manner as Example 1 above, except that silica nanoparticles were removed.

[0080]

[0081] Example 1 Comparative Example 1 Water electrolysis catalyst 100 100 Ionomer 20 20 Silica nanoparticles 80 - Solvent 400 400 Pore size (nm) 100 ~ 400 3 ~ 20 Water electrolysis device performance (@ 1.5 A / cm2) 1.709 V 1.73 V

[0082] Content is in parts by weight.

[0083] Physical property evaluation method

[0084] (1) Pore size (nm): The pore size was measured using a porosimeter (Micromeritics).

[0085] (2) Device performance: Electrolysis performance was evaluated using an anion water electrolysis evaluation device (CNL).

[0086]

[0087] As shown in Table 1 above, Example 1, which uses the electrode ink of the present invention, has a large pore size of 100 to 400 nm similar to that of the added silica particles even when high temperature and pressure are applied during transfer (Fig. 1), and it can be confirmed that the device performance is excellent. In addition, as shown in Fig. 1, some pore sizes of 1000 nm or larger indicate a structure in which the pores are connected. On the other hand, Comparative Example 1, which did not add silica nanoparticles, had a small pore size of 3 to 20 nm. As shown in Fig. 2, it can be confirmed that the device performance of Comparative Example 1 is degraded, and it can be confirmed that the example improves electrolytic performance by adding silica particles to the electrode ink to maintain the pores of the electrode, which would otherwise mostly disappear during the transfer process.

[0088]

[0089] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be included within the scope of the present invention.

Claims

1. Water electrolysis catalyst; Silica nanoparticles; and Ionomer; It is a water electrolysis electrode ink containing, The above silica nanoparticles are included in 5 to 40 weight% (based on solid content) of the total water electrolysis electrode ink.

2. In Paragraph 1, The above-mentioned water electrolysis catalyst is a water electrolysis electrode ink having a spinel crystal structure.

3. In Paragraph 2, The above-mentioned water electrolysis catalyst is a water electrolysis electrode ink having an average particle size (D50) of 3 to 5 μm.

4. In Paragraph 1, The above silica nanoparticles are a water electrolysis electrode ink having an average particle size (D50) of 100 to 1000 nm.

5. In Paragraph 1, The above-described water electrolysis electrode ink comprises 5 to 40 weight% of silica nanoparticles and 1 to 15 weight% of ionomer based on solid content.

6. In Paragraph 1, The above electrode ink is a water electrolysis electrode ink that further comprises 50 to 90 weight percent of a solvent.

7. In Paragraph 1, A water electrolysis electrode ink comprising one or more of the following solvents: water, alcohol, acetone, ethylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and acetonitrile.

8. A water electrolysis electrode comprising the water electrolysis electrode ink of any one of claims 1 to 7.

9. In Paragraph 8, The above electrode is a water electrolysis electrode having a pore size of 100 to 1000 nm when measuring mercury porosity.

10. In Paragraph 8, The above electrode is a water electrolysis electrode having a porous structure in which the pores are interconnected.

11. Electrolyte membrane; and Includes an electrode layer formed on the surface of the above electrolyte membrane; A membrane electrode assembly for water electrolysis, wherein the electrode layer is formed from the water electrolysis electrode ink of any one of claims 1 to 7.

12. In claim 11, the electrode layer is a membrane electrode assembly for water electrolysis having pores of 100 to 1000 nm in mercury porosity measurement.

13. A water electrolysis electrode ink according to any one of claims 1 to 7 is coated onto a polymer film to form an electrode layer; and Transferring the above electrode layer to the surface of the electrolyte membrane; A method for manufacturing a membrane electrode assembly for water electrolysis comprising the steps. forming; and Transferring the above electrode layer to the surface of the electrolyte membrane; A method for manufacturing a membrane electrode assembly for water electrolysis comprising the steps.

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