KR102223998B1 - Membrane electrode assembly for anion exchange membrane water electrolyzer and method of manufacturing membrane electrode assembly for anion exchange membrane water electrolyzer - Google Patents

Abstract

A membrane electrode assembly for a proton exchange membrane water electrolysis device, comprising: an oxygen electrode including an _{iridium oxide (IrO 2} ) layer as an oxygen electrode electrode layer electroplated on a titanium (Ti) layer as a diffusion layer; A hydrogen electrode in which a hydrogen electrode layer is formed on the diffusion layer; And an electrolyte membrane positioned between the oxygen electrode layer and the hydrogen electrode layer, wherein some of the pores of the Ti layer as the diffusion layer are filled with an electrolyte in the electrolyte membrane, and a membrane electrode assembly for a water electrolysis device for a proton exchange membrane is provided.

Description

TECHNICAL FIELD The manufacturing method of a membrane electrode assembly for a proton exchange membrane water electrolysis device and a membrane electrode assembly for a proton exchange membrane water electrolysis device TECHNICAL FIELD [MEMBRANE ELECTRODE ASSEMBLY FOR ANION EXCHANGE MEMBRANE WATER ELECTROLYZER AND METHOD OF MANUFACTURING MEMBRANE ELECTRODE ASSEMBLY FOR ANION EXCHANGE MEMBRANE WATER ELECTRODE]

The present invention relates to a new membrane electrode assembly for a proton exchange membrane water electrolysis device and a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.

Hydrogen is rapidly emerging as an alternative as an energy carrier of the future to overcome environmental and coal depletion problems. However, current hydrogen production mainly relies on petrochemical processes such as steam reforming of natural gas (48%), partial oxidation (30%) and coal gasification (18%), and inevitably releases carbon into the atmosphere.

In an effort to reduce dependence on fossil fuels and suppress carbon emissions, a water electrolyzer (WE), a technology that uses electric energy to separate water into hydrogen and oxygen, is attracting much attention. This technology aims to store energy produced from renewable energy sources such as solar heat, wind power, and hydrothermal heat in a chemical form (H ₂ ) and use it for fuel cells. With the recent increase in renewable energy capacity, development of fuel cell technology, and strengthening of greenhouse gas regulations, research and industrial applications for water electrolysis equipment have increased exponentially over the past 10 years.

Among such water electrolysis devices, there is a low-temperature water electrolysis device. Currently, low-temperature water electrolysis devices include, for example, an alkaline water electrolyzer (AWE), a proton exchange membrane electrolyzer (PEMWE), an anion. Anion exchange membrane water electrolyzer (AEMWE), etc. exist. Among them, AWE occupied most of the commercial market share at a relatively low cost due to the maturity of the technology, but there are problems such as the need for a large-scale plant and the use of toxic solvents, thus exhibiting high energy efficiency and high H ₂ purity. Polyelectrolyte-based water electrolysis devices such as PEMWE and AEMWE have been widely studied and commercialized for small and medium-sized electrolysis devices (<300 kW) applications.

As an alternative, proton exchange membrane water electrolysis (PEMWE) has received special attention because it can produce hydrogen with excellent purity in high yield. In addition, it has been widely used because the system is small in size and has the advantage of not emitting harmful substances.

However, in the case of using PEMWE, there is a problem that the _{operating cost for AWE (3.2 to 5.9 €/kgH 2} ) is about 4.1 to 8.6 €/kgH ₂ , which is relatively high, and the initial investment cost (2090 €/kW) is also, It is about twice as expensive as AWE (1100€/kW) due to expensive materials such as Ti-based bipolar plates, Nafion membranes and PGM-based catalysts.

Considering scale-up, PGM-based metals currently used for both anodes (Ir, Ru) and cathodes (Pt) may be problematic because their amount is very limited. Currently, the cost of Ir is only 6% of the stack, but if PEMWE is widely used, its price may increase significantly. In relation, according to a recent review by Carmo (Non-Patent Document 1), etc., the catalyst requirement of the anode metal (Pt, Ir, Ru) was about 2 mg/cm ₂ (1-6 mg/cm ² ), which is EU-NOVEL. Project), which is about four times higher than the total target PGM loading (less than 0.5 mg) proposed in the project), and in other recent studies, no membrane electrode assembly (MEA) with a catalyst load of less than 1 mg/cm2 has been reported. Accordingly, for commercialization of PEMWE, research efforts to reduce the use of PGM-based metals are required.

On the other hand, in order to manufacture the electrode for PEMWE, various processes including spray coating, decal, sputtering and electrodeposition are used. Of these, spray and decal processes are preferred in most cases, and the positive electrode produced by this technology is a particulate electrode (Fig. 1a), for example, a battery with excellent battery voltage of 1.55-1.8V at ^{1 A/cm 2 and 80°C.} Showed efficiency. However, even in this case, the catalyst loading requirement is relatively high (about 2 mg/cm ² ), and it is difficult to reduce the catalyst loading amount of less than 0.5 mg/cm ^{2 without loss of performance.} On the other hand, in this case, there was a case in which the hydrogen electrode was bonded using a compression process when bonding the electrode after the oxygen electrode was generated, but it was confirmed that the efficiency of the cell was decreased due to the degradation of the hydrogen electrode (FIG. 1B). On the other hand, in the recent studies of Non-Patent Documents 2 and 3 ^{, it was confirmed that the anode was prepared by a decal method containing a catalyst of 0.5 mg/cm 2} or less, but suffered a significant ohmic loss due to the low conductivity of the catalyst layer.

On the other hand, it is also possible to manufacture a film-type electrode by sputtering and electrodeposition processes, and such a film-type electrode ^{exhibited lower performance loss than that even when the amount of catalyst loading was reduced (<0.5 mg/cm 2} ) (FIG. 1C). In relation to, in Non-Patent Document 4, a sputtered IrO ₂ catalyst (loading amount: 0.2 mg / cm ² ) was applied to PEMWE, and in this case, PEMWE ^{showed a voltage of 1.825 at 1A/cm 2} and 80°C. In addition, in Non-Patent Document 5, various alloy films (Pt ₆₈ Co ₂₉ Mn ₃ , Pt ₅₀ Ir ₅₀ and Pt ₅₀ Ir ₂₅ Ru ₂₅ ) were prepared by sputtering, and the performance of PEMWE as a cathode and anode catalyst was tested. The best results they obtained were 1.7 V at 1A/cm ² and 80° C. using Pt black (4 mg/cm ² ) and Pt ₅₀ Ir ₅₀ (0.15 mgPt/cm ^{2 ), respectively, as anode and cathode catalysts.} In addition, in addition, recently, it has _{been studied that the performance of the IrO 2} electrode sputtered at the MEA level is improved by optimizing the loads of the support, ionomer and catalyst (1A/cm ² to 1.71V, 0.24mg/cm ² to 80).

On the other hand, _{research is also underway to prepare an electroplated IrO 2} catalyst (ED IrO ₂ ) for PEMWE, and in this case, the electrode is only 0.1 mg/cm ² of IrO ₂ loading, and very good activity (1A/cm ² and It exhibits 1.6 V) at 90°C, but is industrially restricted because of the use of a carbon-based material. In addition, such film-type electrodes generally have lower cell efficiency than particle-type electrodes due to the three-phase boundary where the electrode, electrolyte and reactants meet together. In the case of the particulate electrode, the ionomer mixed with the nano-sized catalyst size can provide a very high interface surface area between the electrode and the electrolyte, whereas in the case of the film-type electrode, only the catalyst located at the top of the diffusion layer (DL) is an electrolyte. And restricts proton transport from the catalyst to the electrolyte. Thickening the catalyst layer basically does not lead to enlargement of the electrolyte/electrode interface of the film-type electrode. Accordingly, even in the case of manufacturing a film-type electrode, a study on an electrode capable of expanding the interface between the electrolyte/electrode is required.

M. Carmo, D.L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38 (2013) 4901-4934 C. Rozain, E. Mayousse, N. Guillet, P. Millet, Appl. Catal., B 182 (2016) 123-131. C. Rozain, E. Mayousse, N. Guillet, P. Millet, Appl. Catal., B 182 (2016) 153-160. E. Slavcheva, I. Radev, S. Bliznakov, G. Topalov, P. Andreev, E. Budevski, Electrochim. Acta 52 (2007) 3889-3894. M.K. Debe, S.M. Hendricks, G.D. Vernstrom, M. Meyers, M. Brostrom, M. Stephens, Q. Chan, J. Willey, M. Hamden, C.K. Mittelsteadt, C.B. Capuano, K.E. Ayers, E.B. Anderson, J. Electrochem. Soc. 159 (2012) K165. H.-S. Oh, H.N. Nong, T. Reier, M. Gliech, P. Strasser, Chem. Sci. 6 (2015) 3321-3328. P. Lettenmeier, L. Wang, U. Golla-Schindler, P. Gazdzicki, N.A. Canas, M. Handl, R. Hiesgen, S.S. Hosseiny, A.S. Gago, K.A. Friedrich, Angewandte Chemie 55 (2016) 742-746 S. Siracusano, N. Van Dijk, E. Payne-Johnson, V. Baglio, A.S. Arico, Appl. Catal., B 164 (2015) 488-495. A. Skulimowska, M. Dupont, M. Zaton, S. Sunde, L. Merlo, D.J. Jones, J. Roziere, Int. J. Hydrogen Energy 39 (2014) 6307-6316. A. Marshall, S. Sunde, M. Tsypkin, R. Tunold, Int. J. Hydrogen Energy 32 (2007) 2320-2324.

In embodiments of the present invention, a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device capable of increasing an electrolyte/electrode interface is provided.

In other embodiments of the present invention, it is intended to provide a membrane electrode assembly for a proton exchange membrane water electrolysis device manufactured according to the above manufacturing method.

In one embodiment of the present invention, a membrane electrode assembly for a proton exchange membrane water electrolysis device, comprising: an oxygen electrode including an _{iridium oxide (IrO 2) layer, which is an oxygen electrode electrode layer electroplated on a titanium (Ti) layer, which is a diffusion layer;} A hydrogen electrode in which a hydrogen electrode layer is formed on the diffusion layer; And an electrolyte membrane positioned between the oxygen electrode layer and the hydrogen electrode layer, wherein some of the pores of the Ti layer, which is the diffusion layer, are filled with an electrolyte in the electrolyte membrane.

In an exemplary embodiment, the Ti layer is divided into an upper region and a lower region, the pores of the upper region of the Ti layer are filled with the electrolyte of the electrolyte membrane, and the pores of the lower region of the Ti layer are not filled with the electrolyte of the electrolyte membrane. I can.

In an exemplary embodiment, the upper region of the Ti layer may have a thickness of 25 to 35 μm.

In an exemplary embodiment, the IrO ₂ layer may include 0.01 to 1.05 mg /cm ² of iridium oxide loaded on the Ti layer.

In another embodiment of the present invention, there is provided a proton exchange membrane water electrolysis apparatus comprising a membrane electrode assembly for the proton exchange membrane water electrolysis apparatus.

In another embodiment of the present invention, as a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device, a Ti layer, which is a diffusion layer, is formed by _{electroplating iridium oxide (IrO 2} ) on a _{titanium (Ti) layer to form an IrO 2 layer.} And _{preparing an oxygen electrode including an IrO 2} layer which is an oxygen electrode electrode layer. Laminating an electrolyte membrane on _{the IrO 2} layer of the oxygen electrode; Forming an oxygen electrode-electrolyte membrane assembly by performing a compression process on the oxygen electrode and the electrolyte membrane; After the pressing process, manufacturing a membrane electrode assembly by bonding a hydrogen electrode having a hydrogen electrode layer formed on a diffusion layer on one surface of the exposed electrolyte membrane; A method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device comprising a is provided.

In an exemplary embodiment, the Ti layer of the oxygen electrode includes a plurality of pores, and some of the pores of the Ti layer of the oxygen electrode of the membrane electrode assembly may be filled with the electrolyte of the electrolyte membrane.

In an exemplary embodiment, the Ti layer is divided into an upper region and a lower region, the pores of the upper region of the Ti layer are filled with the electrolyte of the electrolyte membrane, and the pores of the lower region of the Ti layer are not filled with the electrolyte of the electrolyte membrane. I can.

In an exemplary embodiment, the upper region of the Ti layer may have a thickness of 20 to 40 μm.

In an exemplary embodiment, the pressing process may be performed for 1 minute to 5 minutes under a temperature condition of 120 to 160°C.

In an exemplary embodiment, the pressing process may be performed under a pressure condition of 4 to 20 MPa.

In an exemplary embodiment, the Ti layer may be titanium mesh or titanium paper.

In an exemplary embodiment, _{the process of electroplating IrO 2} may be performed for 1 minute to 10 minutes under a plating voltage condition of 0.5 to 0.9 V.

In an exemplary embodiment, the IrO ₂ layer may include 0.01 to 1.05 mg/cm ² of IrO ₂ loaded on the Ti layer.

In an exemplary embodiment, _{prior to electroplating IrO 2} , the titanium layer may be immersed in oxalic acid and then washed with ionized water.

According to a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device according to an embodiment of the present invention, _{after manufacturing an electrode including an IrO 2} layer, an electrolyte membrane is stacked and a compression process is performed. In this case, the _{electrolyte may penetrate into the IrO 2} /TP electrode and the pores of the Ti layer may be partially filled with the electrolyte, thereby increasing the electrolyte/electrode interface. Accordingly, a film-type electrode having superior performance compared to a conventional particle-type electrode can be manufactured, and an excellent proton exchange membrane water electrolysis device can be manufactured.

1A to 1D are schematic diagrams showing a manufacturing process of a membrane electrode assembly according to a conventional electrode.
2 is a schematic diagram showing a manufacturing process of the membrane electrode assembly according to the present invention.
3 shows the results of comparing the surfaces of the oxygen electrode-electrolyte membrane assembly before and after the compression (hot press) process.
4A is _{a photograph showing the surface shape of an electroplated IrO 2} layer and a corresponding EPMA mapping result, and FIG. 4B is a graph showing the change in the amount of _{IrO 2} loading according to the change of _{t dep, measured by ICP-MS.}
5A shows iV curves of various electrodes (IrO ₂ /CP, IrO ₂ /TP, and a film-oxygen electrode assembly including an _{IrO 2} /TP electrode compressed by the P1 method to the P2 method), and FIG. 5B shows the The Nyquist plot at 1.6 V is shown.
_{6 shows changes in R ohm} according to changes in current densities at 1.6V, 1.8V, and 2.0V and voltages applied during the compression (hot press) process. The compression (hot press) process was performed in the P2 method of FIG. 5A.
FIG. 7A shows _{each configuration constituting R ohm} of the entire battery, and FIG. 7B shows each configuration constituting R _ohm of a battery without a film. 7C shows the contributions of _{R t} , R _m and R _i to the _{total R ohm in various electrodes.} On the other hand, in the upper right of FIG. 7C, the iV characteristics of the membrane-free battery having CP and TP as DL of the anode are described.
Figure 8a shows the change in the thickness of the TP, membrane, and TP-membrane assembly after a compression (hot press) process under a pressure of 0-20 MPa, and Figure 8b shows a cross-sectional image of the _{IrO 2 /TP-membrane assembly after hot pressing at 8 MPa.} EPMA results for F, Ti and Ir are shown.
9A shows the thickness of the ME zone between the membrane-electrode and the corresponding contact area (Ac) in the pressure change in the compression (hot press) process, and FIG. 9B shows R _{i,m according to the change of 1/Ac.} It is described.
10 shows the current density at 2.0 V as a function of the ME region for various electroplated IrO _{2 /TP electrodes.
11 shows the cell voltage of electroplated IrO 2} /TP according to the amount of catalyst loading in the anode, and the prior art is also described.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention disclosed in the text are illustrated for purposes of explanation only, and the embodiments of the present invention may be implemented in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention is not intended to limit the present invention to a specific disclosed form, as various changes may be added and various forms may be added, and all changes, equivalents, or substitutes included in the spirit and scope of the present invention It should be understood to include.

Definition of terms

In the present specification, "titanium paper" refers to a paper-shaped substrate formed by densely intertwining titanium (Ti) fibers in a cylindrical or polygonal tube. The cross-sectional area of the titanium fiber may be 50-10000 μm ² .

In this specification,'oxygen electrode' is used as a term referring to the same electrode as'anode', and'hydrogen electrode' is used as a term referring to the same electrode as'cathode'.

Membrane Electrode Assembly for Proton Exchange Membrane Water Electrolysis Equipment and Proton Exchange Membrane Water Electrolysis Equipment

In one embodiment of the present invention, a membrane electrode assembly for a proton exchange membrane water electrolysis device is provided. The membrane electrode assembly for the proton exchange membrane water electrolysis device includes an oxygen electrode including an _{iridium oxide (IrO 2} ) layer as an oxygen electrode electrode layer electroplated on a titanium (Ti) layer as a diffusion layer; A hydrogen electrode in which a hydrogen electrode layer is formed on the diffusion layer; And an electrolyte membrane positioned between the oxygen electrode layer and the hydrogen electrode layer, and some of the pores of the Ti layer as the diffusion layer may be filled with the electrolyte of the electrolyte membrane.

Specifically, the oxygen electrode contains a Ti layer as a diffusion layer.

In this case, the Ti layer is a porous Ti layer, and may include titanium mesh or titanium paper (TP). In one embodiment, it may be preferable to use titanium paper because the area ratio of exposed Ti per unit volume is high, and the probability of occurrence of a short in the hot pressing process is low.

Meanwhile, the Ti layer may include a plurality of pores, and the porosity of the Ti layer may be about 50-80%, preferably about 60-70%.

In an exemplary embodiment, the Ti layer may have a thickness of 60 to 500 μm. If the thickness is less than 60 μm, the pores of the titanium paper are clogged after the pressing process, resulting in a decrease in performance, and if it exceeds 500 μm, the material transfer path of water is lengthened, resulting in a decrease in performance.

Meanwhile, some of the pores of the Ti layer may be filled with the electrolyte of the electrolyte membrane positioned between the hydrogen electrode layers, because the electrolyte of the electrolyte membrane penetrates into the upper region of the Ti layer when the pressure bonding process is performed on the oxygen electrode and the electrolyte membrane. In this case, since the electrolyte/electrode interface may be increased, the performance of the proton exchange membrane water electrolysis device including the same may be superior to that of the conventional particulate electrode.

Meanwhile, the pores of the lower portion of the Ti layer may not be filled with the electrolyte of the electrolyte membrane. For example, when the Ti layer is divided into an upper region and a lower region, the pores of the upper region of the Ti layer may be filled with the electrolyte of the electrolyte membrane, The pores in the lower region may not be filled with the electrolyte of the electrolyte membrane.

In one embodiment, the Ti layer may be a Ti layer that has been immersed in oxalic acid and washed with ionized water. In this case, the natural oxide layer on the surface of the Ti layer is removed, so that IrO ₂ is uniformly supported on the entire surface, thereby increasing performance. .

On the other hand, the IrO ₂ layer can function as an oxygen electrode layer. The IrO ₂ layer is electroplated, and the characteristic (or morphology) or structure of electrolytic plating is distinguished from the case of using other manufacturing methods (e.g., spray method or decal method) for forming _{IrO 2} on the Ti layer. Will have.

In an exemplary embodiment, the IrO ₂ layer is to cover the surface of the titanium layer, IrO ₂ layer preferably has a (crack free) structure with no cracking.

Meanwhile, in the present invention, _{even if the IrO 2} layer is loaded on the Ti layer in a small amount, the same or improved effect may be exhibited compared to the conventional anode. For example, the Ti layer from 0.01 to 1.05mg / cm ² of IrO _2, specifically, even if the IrO ₂ of 0.2 mg / cm ² loading at 0.075 can be seen a conventional PEM water electrolysis device contrast improved effect.

Meanwhile, in another embodiment of the present invention, there is provided a proton exchange membrane water electrolysis apparatus including a membrane electrode assembly for the proton exchange membrane water electrolysis apparatus.

As described above, in the present invention, _{after manufacturing an oxygen electrode including an IrO 2} layer/Ti layer, a single-sided compression process is performed using an electrolyte membrane. Accordingly, the membrane electrolyte may penetrate into the Ti layer of the oxygen electrode, so that _{the pores of IrO 2} /TP may be partially filled with the electrolyte. The average thickness of the pore-filled portion of the Ti layer affects the active area. Within the optimum thickness range, the ^{cell voltage under 1.0A/cm 2} and 80° C. may be lowered from 1.78V to 1.64V. This is a value comparable to that when a PGM-based catalyst is loaded (eg, 1-3 mg). Accordingly, it can be widely used in a water electrolysis device.

Method for producing membrane electrode assembly for proton exchange membrane water electrolysis device

In one embodiment of the present invention, as a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device, a Ti layer as a diffusion layer by forming an _{IrO 2 layer by electroplating iridium oxide (IrO 2} ) on a titanium (Ti) layer, and Preparing an oxygen electrode including an _{IrO 2} layer as an oxygen electrode electrode layer; Laminating an electrolyte membrane on _{the IrO 2} layer of the oxygen electrode; Forming an oxygen electrode-electrolyte membrane assembly by performing a compression process on the oxygen electrode and the electrolyte membrane; And preparing a membrane electrode assembly by bonding a hydrogen electrode to one surface of the exposed electrolyte membrane after the pressing process. A method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device comprising a is provided. In Fig. 2, the manufacturing method is briefly described. Hereinafter, each step will be described in detail.

First, by electrolytic plating a titanium (Ti), iridium oxide (IrO ₂₎ on the layer to form the IrO ₂ layer to prepare an oxygen electrode comprising a Ti layer and an IrO ₂ layer. The Ti layer may function as a diffusion layer, and the IrO ₂ layer may function as an electrode layer.

In an exemplary embodiment, the Ti layer is not limited, but may include titanium mesh or titanium paper. However, titanium paper may be preferable because the area ratio of exposed Ti per unit volume is high, and the probability of occurrence of a short in the hot pressing process is low.

Meanwhile, the Ti layer is a porous Ti layer, and may include a plurality of pores. In one embodiment, the porosity of the porous Ti layer may be about 50-80%, and preferably about 60-70%.

In an exemplary embodiment, the Ti layer may have a thickness of 60 to 500 μm. If the thickness is less than 60 μm, the pores of the titanium paper are clogged after the pressing process, resulting in a decrease in performance, and if it exceeds 500 μm, the material transfer path of water is lengthened, resulting in a decrease in performance.

In one embodiment, _{prior to electroplating IrO 2} , the Ti layer may be further washed with ionized water after being immersed in oxalic acid. In this case, the natural oxide film on the surface of the Ti layer is removed so that IrO ₂ is removed from the entire surface. It can be supported evenly.

On the other hand, in the present invention, when the iridium oxide (IrO ₂ ) layer is electroplated, it is distinguished from the case of using other manufacturing methods (eg, spray method or decal method) for forming _{IrO 2} on the corresponding mesh-shaped Ti layer. It has a characteristic (or morphology) or structure peculiar to electrolytic plating. That is, when the IrO ₂ layer is formed on the _{Ti layer by electroplating, IrO 2} particles (for example, spherical particles) begin to be formed and IrO ₂ particles are generated on the surface of the Ti layer and grow in the form of a film, so that the surface of the Ti layer becomes IrO. Covered (ie, surface coated) with _two layers (or _{may also be expressed as an IrO 2 film), and IrO 2} particles further formed over the passage of plating time are attached (or deposited) to the IrO _{2 layer (structure)} Will have.

In an exemplary embodiment, this is to the IrO ₂ layer covering the surface of ti layer, IrO ₂ layer preferably has a (crack free) structure with no cracking.

In one embodiment, _{the surface of the IrO 2} layer titanium paper may be covered.

Meanwhile, in the present invention, _{even if the IrO 2} layer is loaded on the Ti layer in a small amount, the same or improved effect may be exhibited compared to the conventional anode. For example, the Ti layer from 0.01 to 1.05mg / cm ² of IrO _2, specifically, even if the IrO ₂ of 0.2 mg / cm ² loading at 0.075 can be seen a conventional PEM water electrolysis device contrast improved effect.

Meanwhile, in an exemplary embodiment, during the electroplating process, it may be performed under a plating voltage condition of 0.5 to 0.9 V, and more specifically, it may be performed under a plating voltage condition of 0.6 to 0.9 V. When electroplating is performed at less than 0.5 V _{, cracks may be generated in the IrO 2} layer, and when electroplating is performed at more than 0.9 V, the deposition efficiency is not excellent, and thus, it may not be preferable in terms of economy.

In an exemplary embodiment, the electroplating may be performed in 1 minute or more and less than 20 minutes, and specifically, it may be performed in 5 minutes or more and 15 minutes or less. When electroplating is performed in less than 1 minute, the IrO ₂ layer may not completely cover the Ti layer, and when it exceeds 10 minutes, cracks may be generated in the _{IrO 2 layer.}

Thereafter, an electrolyte membrane may be laminated on _{the IrO 2} layer of the oxygen electrode.

In an exemplary embodiment, as the electrolyte membrane, for example, Nafion, polybenzimidazole (PBI), Aquivion, or a polymer membrane thereof may be used. In addition, the electrolyte membrane is not limited at the time of lamination and may be laminated using a conventional technique. I can.

Subsequently, a compression process is performed on the oxygen electrode and the electrolyte membrane to form an oxygen electrode-electrolyte membrane assembly. Pressure is applied to the oxygen electrode and the electrolyte membrane through the compression process, so that the oxygen electrode and the electrolyte membrane may be compressed.

When the compression process is performed on the oxygen electrode and the electrolyte membrane, the pores of the Ti layer may be partially filled with the electrolyte of the electrolyte membrane. Accordingly, the interface between the electrode and the electrolyte is enlarged, and an additional interface between the electrode and the electrolyte may be provided.

In an exemplary embodiment, the pressing process may be performed for 1 minute to 5 minutes under a temperature condition of 120 to 160°C, and specifically, may be performed for 2 to 4 minutes under a temperature condition of 135 to 150°C. . If it is out of the above range, the pores of the Ti layer of the oxygen electrode may have too small or large penetration depth of the electrolyte in the electrolyte membrane, and thus performance improvement may not be sufficient.

In an exemplary embodiment, the pressing process may be performed under a pressure condition of 4 to 20 MPa. The higher the pressure, the greater the number of pores in the Ti layer of the oxygen electrode that are filled with the electrolyte in the electrolyte membrane, thereby increasing the active area. However, if the pores are filled with the electrolyte in this way, the raw material for the proton exchange membrane water electrolysis device Since the reaction sites for phosphorus water to react are reduced, it is preferable that only the pores in the upper region adjacent to _{IrO 2 in the Ti layer of the oxygen electrode are filled with the electrolyte of the electrolyte membrane.}

In one embodiment, the pressing process may be performed under a pressure condition of 5 to 10 MPa.

In one embodiment, the pressing process may be a hot press process.

Through the compression process, some pores of the Ti layer may be filled with the electrolyte of the electrolyte membrane. For example, the Ti layer is divided into an upper region and a lower region. In this case, the pores in the upper region of the Ti layer are filled with the electrolyte of the electrolyte membrane, whereas in the lower region of the Ti layer, the pores may not be filled with the electrolyte of the electrolyte membrane. have.

In this case, the upper region of the Ti layer may have a thickness (vertical) of 20 to 40 μm, for example, may have a thickness of 25 to 35 μm.

If the upper region of the Ti layer has a thickness of less than 20 μm, the effect of expanding the three-phase boundary due to the enlargement of the interface between the electrode and the electrolyte may be insignificant. If it exceeds 40 μm, the raw material of the proton exchange membrane water electrolysis device Reaction sites for phosphorus to react may be reduced, and the performance of the electrolyzer may be degraded.

Thereafter, after preparing a hydrogen electrode, a membrane electrode assembly is manufactured by bonding the hydrogen electrode to one surface of the exposed electrolyte membrane. In one embodiment, the hydrogen electrode may also include a diffusion layer and a hydrogen electrode layer formed on the diffusion layer. In one embodiment, the hydrogen electrode may be manufactured to have a configuration of Pt/C.

On the other hand, the hydrogen electrode should be bonded to the electrolyte membrane after the above-described compression process. When performing the compression process after placing the hydrogen electrode and the oxygen electrode with the electrolyte membrane interposed as shown in FIG. 1D, the carbon material of the hydrogen electrode is Because it can be damaged.

As described above, in the present invention, after the oxygen electrode including the IrO 2 layer/Ti layer is manufactured, a single-sided pressing process is performed using an electrolyte membrane. Accordingly, the membrane electrolyte may permeate the Ti layer of the oxygen electrode, so that the pores of IrO2/TP may be partially filled with the electrolyte. The average thickness of the pore-filled portion of the Ti layer affects the active area, and within the optimum thickness range, the cell voltage under 1.0A/cm2 and 80°C may be lowered from 1.78V to 1.64V. Accordingly, it can be widely used in a water electrolysis device.

Hereinafter, the present invention will be described in more detail through examples. These examples are for illustrative purposes only, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not construed as being limited by these examples.

Example

Manufacturing example

IrO ₂ /TP manufacturing

Consisting of 10 mM iridium chloride hydrate (IrCl ₄ · H ₂ O), 100 mM hydrogen peroxide (H ₂ O ₂ ), 40 mM oxalic acid (COOH ₂ · 2H ₂ O) and 340 mM potassium carbonate (KCO ₃ ) After preparing a water bath containing the electrolytic plating solution, the IrO ₂ catalyst was positively electrodeposited. To stabilize the Ir complex, the water bath was aged for at least 3 days of electrodeposition. Titanium paper (berkit, ST/Ti/20/ 450/60) with an active area of 6.25 cm ² was used as the working electrode, and Ti mesh and standard calomel electrode (SCE) were each counter electrode. And as a reference electrode. Before electroplating, the working electrode was immersed in 5 wt% oxalic acid at 60° C. for 30 minutes and then washed with pure DI water. Thereafter, this was transferred to a Teflon cell, and a potential difference of _{0.7 V SCE was continuously applied for 10 minutes at room temperature.}

IrO ₂ /CP manufacturing

For comparison, IrO ₂ /TP was prepared under the same experimental conditions, but IrO ₂ was electrodeposited on carbon paper instead of titanium paper.

HP-IrO ₂ /TP manufacturing

_{IrO 2} /TP was prepared by electrodepositing _{IrO 2} on TP as described above. Thereafter, by hot pressing the electrolyte membrane and the oxygen electrode at 140° C. and 4-20 MPa for 2 minutes, HP-IrO _{2 /TP (or HP-IrO 2} /TP manufactured according to the P2 method of FIG. 5A) Was prepared. In addition, in the following examples, HP-IrO ₂ /TP was prepared by variously changing the pressure conditions during the hot press process. Among these, the cases in which the pressure was adjusted to 4 MPa, 8 MPa and 20 MPa were respectively expressed as HP-IrO ₂ /TP@4MPa, HP-IrO ₂ /TP@8MPa and HP-IrO ₂ /TP@20MPa.

HP’-IrO ₂ /TP manufacturing

For comparison, after each of an oxygen electrode and a hydrogen electrode were manufactured, a Nafion film (NR-212, Dupont) was placed in the middle, and then hot pressed. The oxygen electrode was prepared as described above, and the hydrogen electrode was prepared by using a catalyst ink consisting of 46.5wt% Pt/C (Johnson Matthey), 5wt% Nafion solution, isopropyl alcohol (IPA, JT Baker), and deionized water. (39BC, SGL carbon) was prepared by spray coating. The loading amount of Pt was 0.4 mg/cm ² , the Nafion content was 30 wt%, and the hot press process was performed at 140, 4-20 MPa for 2 minutes. Accordingly, HP-IrO _{2 /TP (or HP-IrO 2} /TP prepared according to the P1 method of FIG. 5A) was prepared.

IrO2/CP electrode and IrO ₂ /TP electrode characteristics analysis

All processes were performed using potentiostat equipment (AUT302N, AUTO LAB Ltd.). _{The distribution of IrO 2} and the _{amount of IrO 2} loading on the electrode surface were investigated through EPMA and inductively coupled plasma mass spectroscopy (ICP-MS) analysis, respectively.

Membrane electrode assembly and PEMWE single cell fabrication

MEA was prepared after each of the above-described electrodes (IrO ₂ /CP, IrO ₂ /TP, HP-IrO ₂ /TP, HP'-IrO _{2 /TP, etc.) and hydrogen electrodes were prepared.} The hydrogen electrode was manufactured through the same process as described above. Are joined HP-IrO ₂ / when using the TP, HP-IrO Place the ₂ / TP to be negative (Pt / C) on both surfaces of the Nafion membrane (NR-212, Dupont) was prepared in the MEA. Subsequently, the MEA was mounted on a single cell for a home equipped with graphite (cathode) and Au/Ti bipolar plate (anode) to prepare a single cell for a proton exchange membrane water electrolysis device (PEWME). At this time, the exposed active area of the MEA was fixed to ^{6.25 cm 2.}

Membrane Electrode Assembly and PEMWE Single Cell Characterization

The iV curve and electrochemical impedance spectroscopy (EIS) results were obtained from a potentiostat (HCP-803, biologic) combined with a power booster. Constant voltages from 1.35V to 2.0V were each applied at 0.05V intervals for 1 minute. D. I. Ionized water was supplied to the anode side of the cell at a flow rate of 15 mL/min. The temperature of the ionized water and the cell temperature were fixed at 80 °C.

Results and discussion

IrO ₂ /TP and IrO ₂ /CP electrode characteristics review

_{The surface morphology of the IrO 2} film electrodeposited on titanium paper (TP) for 10 minutes at an E _dep of 0.7 V is shown in FIG. 4A. It can be seen that the electrodeposited IrO ₂ is uniformly distributed without noticeable defects or lumps. The enlarged image showed that IrO ₂ particles of submicron diameter were formed on the cracked IrO ₂ film to provide a high surface area. This shape is similar to the _{IrO 2} film electrodeposited on carbon paper. Looking at the results of the ICP-MS analysis of Figure 4b, it was shown that the IrO ₂ loading amount is almost proportional to _{t dep} having a slope of 0.0148 mg / cm ^{2 ·min.} In the case of 10 minutes t _dep , it was confirmed that the _{IrO 2} loading amount reached 0.13 mg/cm ² , which was almost identical to CP (0.1 mg/cm ^{2 ).}

Then, the performance of the water electrolysis device including the electrode was examined.

5A shows the iV curves of _{IrO 2} electrodes (ie, IrO ₂ /CP and IrO ₂ /TP) electrodeposited on CP and TP under _{an E dep} of 0.7 V for 10 minutes. Despite the similar IrO ₂ loading amount, _{it was confirmed that the IrO 2} /TP electrode provided _{inferior voltage efficiency than IrO 2} /CP for all current densities (However, the IrO ₂ /CP electrode could not be used due to stability issues. There is a problem). The cell voltage at 1A/cm ² for IrO ₂ /TP was 1.78V, which was 0.13V higher than _{IrO 2 /CP (1.65V).} The EIS results at 1.6 V show that higher ohmic resistance (R _ohm ) and lower kinetics _{contribute to the degradation of IrO 2} /TP (Fig. 5b). HP-IrO ₂ / TP and HP'-IrO iV curve of the ₂ / TP electrode also has been described with in Figure 5a (in Fig. 5a, HP-IrO ₂ / TP is represented by P2, HP'-IrO ₂ / TP Is denoted as P1). HP'-IrO ₂ /TP only improves electrode performance by reducing _{R kin , whereas for HP-IrO 2} /TP, it was confirmed that the compression process not only provided better power but also provided low R _ohm. (Fig. 5b). This _{reduction of R kin} showed that the application of the compression process enlarged the interface between the electrode and the electrolyte, thereby expanding the three-phase boundary. _{The expanded interface can also provide a low R ohm} by providing an additional interface for proton transfer, as in the case of HP-IrO _{2 /TP.} On the other hand, in the case of performing a compression process after manufacturing a cathode such as _{HP'-IrO 2} /TP, the carbon fiber structure on the cathode side may be _{destroyed during the compression process, resulting in an increase in R ohm.} Accordingly, it was confirmed that the most effective method of improving the cell performance is to bond the cathode after the anode is fabricated and then the electrolyte membrane and the compression process are performed.

In the compression process performed during HP-IrO ₂ /TP production, the experiment was performed by varying the pressure, and the performance results are shown in FIG. 6. _{In addition, R ohm} measured by a high frequency intercept of the EIS at 1.6V is also described in FIG. 6. Referring to Figure 6, R _ohm is the case that the pressure applied during the crimping process exceeds 8 MPa R _ohm were cut in half (0 MPa 0.238 Ω · cm in the ² -> 0.118 Ω at 20 MPa · cm ^2). The increase in current density was observed at low voltage (1.6V) and medium voltage (1.8V) where activation and ohmic losses are important, and at high voltage (2.0V), the highest current density was observed around 8 MPa, and performance deteriorated with additional pressure. Was able to confirm. This result suggests that excessively high pressure during the compression process has a positive effect on reaction kinetics and ohmic losses, but negatively for mass transfer.

As shown in FIG. 6, R _ohm can be expressed as a function of the pressure applied during the hot press and the anode substrate. For clarity, R _{ohm is the external battery resistance R O} as shown in [Equation 1], It was expressed as the sum of the membrane resistance (R _m ), the cathode resistance (R _c ), the anode resistance (R _a ), and the interface resistance (R _i,cm , R _i,am , R _i,cb , R _{i,ab ).}

[Equation 1]

R _ohm = R _O + R _m + R _i,cm + R _i,am + R _c + R _a + R _i,cb + R _i,ab

_{7A is a schematic diagram showing R ohm} of a battery including an electrolyte membrane, and FIG. 7B is a schematic diagram showing _{R ohm of a battery not including an electrolyte membrane.}

Referring to FIG. 7B _{, the contributions of R O} , R _c , R _a , R _i,cb and R _i,ab are approximately approximated in _{R ohm} of the cell not including the electrolyte membrane _{, where R i,ca} may be omitted. It's about. On the other hand, R _m can be calculated from the conductivity of the Nafion membrane in a completely wet state at 80°C (0.16 S/cm ^{2 ).} Therefore, reflecting this, and if R _i,cm and R _i,am are summed _{and expressed as R i,m} , the [Equation 1] can be expressed by the following [Equation 2].

[Equation 2]

R _ohm = 0.031 Ωcm ² + R _t + R _{i , m}

_{Total R ohms for} various electrodes (IrO ₂ /CP, IrO ₂ /TP, HP-IrO ₂ /TP(@4MPa), HP-IrO ₂ /TP(@8MPa) and HP-IrO ₂ /TP(@20MPa)) The individual contributions of R _t , R _m and R _{i, m to} are shown in Fig. 7c. When TP was used instead of CP, there were two notable changes, with a naturally formed non-conductive TiO ₂ layer on the TP. As a result, R _t increased from 0.034 to 0.078 Ω·cm ² and R _{i ,m} increased from 0.028 Ω·cm ² to 0.129 Ω·cm ^2. _{The difference between R i ,m} between CP and TP is the electrode and the electrolyte is thought to be related to the roughness factor (roughness factor) of the substrate affecting the contact area between. (CP: 35.7, TP: 20.0) in addition, the application of the hot-pressed under a predetermined pressure condition is the R _{i, m} It was found to be considerably reduced from 0.129 to 0.009 Ω/cm ² , and in order to confirm the change of the electrode, under various pressure conditions as shown in FIG. 8A, a hot press process was performed on _{IrO 2 /TP, TP, and membrane.} Unlike the uncompressed TP and the membrane, _{the thickness of the membrane-TP conjugate formed after hot pressing for IrO 2} /TP was significantly reduced because the rigid TP body penetrated the membrane electrolyte. The penetration depth is roughly proportional to the applied pressure, and in the case of the pressing process performed under the pressure conditions of 4 MPa, 8 MPa and 20 MPa, it was confirmed that the thickness decreases of 13.4, 20.4 and 37.2 μm, respectively. The figure inserted in FIG. 8A schematically shows the bonding of the TP and the membrane after the pressing process. When the TP body penetrates the membrane, it can be seen that a region partially filled with the membrane (hereinafter, the ME region) is formed by the pores of the TP. The ME region was at the _{boundary of R if} and three phases. It provides an additional interface between the electrode and the electrolyte, which has a direct effect, and the cross-sectional photographs and EPMA results of the hot-pressed membrane-TP assembly at 8 MPa are shown in FIG. Referring to FIG. 8B, it can be clearly seen that the TP penetrated the membrane and the ME region was formed. The average vertical thickness (t _ME ) of the ME region and the corresponding electrode/electrolyte contact area (A _C ) may be represented by the following [Equation 3] and [Equation 4].

[Equation 3]

t _ME =Δt _a /p

[Equation 4]

Here, Δta denotes the _{change in thickness of the IrO 2} /membrane assembly after the compression process, p denotes the porosity of the TP, t _Ti denotes the thickness of the TP, and D denotes the diameter of the Ti fiber. 9A shows the contact area corresponding to _{t ME} as a function of the applied pressure. When pressures of 4 MPa, 8 MPa, and 20 MPa were applied, the average contact areas were ^{increased to 1.23, 2.16 and 4.40 cm 2} /cm ² _geo , respectively. Assuming that R _i,m is inversely proportional to _{Ac, the correlation between R i,m} and Ac can be expressed as Equation 5.

[Equation 5]

Meanwhile, FIG. 9B shows R _if as a function of 1/Ac, indicating that a specific contact resistance (σ) is 0.024 Ω·cm ⁴ .

As described above, it was confirmed that the electrode/electrolyte interface additionally appeared when the hot press was applied, but disturbance of mass transfer occurred. _{For generalization, after forming an electrode by electrodepositing IrO 2} on Ti paper having a porosity of 56%, 60%, and 73%, the current density at 2.0 V was _{calculated as a function of t M -E} (Fig. 10). . The highest current density was found at _{t M -E of about 30 μm.} Below this value, a limited electrode/electrolyte interface can be provided, and R _kin as well as R _ohm can be increased. When t _{ME exceeded 30 μm, H 2} O access to the electrolyte/electrode interface appeared to be blocked by membrane scraps in the pores of the TP. It was confirmed that the best performance can be obtained when the electrode/electrolyte contact and mass transfer of water are balanced (eg, t _{ME of 30 μm).}

On the other hand, _{the performance of the IrO 2} / TP electrode after the pressing process was compared with the various electrodes reported in the reference literature. As shown in Fig. 11, the current density of the IrO 2 / TP electrode was similar at 80°C and 1.7 V before hot press. It showed similar values to the results of the reference literature having the catalyst loading amount (Non-Patent Document 2), but after hot press, similar to the cells (Non-Patent Documents 6, 7, 8) having a ^{catalyst loading amount of 1 to 1.5 mg/cm 2.} It could be confirmed that the figures were shown.

As described above, in the present invention, the effect of a single-sided compression bonding process in an _{electroplated IrO 2 electrode for a PEMWE is described.} IrO to apply the electrolyte laminated film after contact bonding to the upper surface of the ₂ / TP electrodes, by penetrating the membrane electrolyte to the IrO ₂ / TP electrode to form a pore of the ME region is IrO ₂ / diffusion filled with partially electrolyte. Higher thickness of the ME region provides a better electrode/electrolyte interface, but limits the access of _{H 2 O.} For the optimal ME thickness, the _{cell voltage of the IrO 2} / TP electrode under the conditions of 1.0 A/cm ² and 80 °C was considerably lowered from 1.78 V to 1.64 V, which is the result of the recent particle electrode with more _{IrO 2 loading.} It is comparable when used (1-3mg/cm ² ). Accordingly, it was confirmed that for PEMWE, an excellent film-type electrode could be manufactured with a small amount of PGM metal.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those of ordinary skill in the technical field of the present invention can improve and change the technical idea of the present invention in various forms. Therefore, such improvements and changes will fall within the scope of the present invention as long as it is apparent to those of ordinary skill in the art.

Claims (12)

As a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device,
Comprising the steps of electroplating a titanium (Ti), iridium oxide (IrO ₂₎ on the layer to form a layer made of IrO ₂ an oxygen electrode comprising a diffusion layer of Ti layer and the oxygen-electrode-electrode layer of IrO ₂ layer;
Laminating an electrolyte membrane on _{the IrO 2} layer of the oxygen electrode;
A step of forming an oxygen electrode-electrolyte membrane assembly by performing a compression process on the oxygen electrode and the electrolyte membrane,
The Ti layer electroplated with the iridium oxide (IrO ₂ ) layer is divided into an upper region and a lower region, and _{the pores in the upper region of the Ti layer electroplated with the iridium oxide (IrO 2} ) layer are partially filled with the electrolyte of the electrolyte membrane. And, the pores in the lower region of the electroplated Ti layer of the iridium oxide (IrO ₂ ) layer are not to be filled with the electrolyte of the electrolyte membrane,
In order to increase the interface between the electrode and the electrolyte and prevent the mass transfer of water from being disturbed, the iridium oxide (IrO ₂ ) layer is in the upper region of the electroplated Ti layer, in the ME region where the pores are partially filled with the electrolyte of the electrolyte membrane. Making the average vertical thickness t _ME have a thickness of 25 μm or more and 30 μm or less;
After the pressing process, manufacturing a membrane electrode assembly by bonding a hydrogen electrode having a hydrogen electrode layer formed on a diffusion layer on one surface of the exposed electrolyte membrane to prepare a membrane electrode assembly; and
The membrane electrode assembly for the proton exchange membrane water electrolysis device,
_{An oxygen electrode including an iridium oxide (IrO 2} ) layer that is an oxygen electrode electrode layer electrolytically plated on a titanium (Ti) layer as a diffusion layer;
A hydrogen electrode in which a hydrogen electrode layer is formed on the diffusion layer; And
It includes an electrolyte membrane positioned between the oxygen electrode layer and the hydrogen electrode layer,
Some of the pores of the Ti layer as the diffusion layer are filled with the electrolyte of the electrolyte membrane,
The Ti layer electroplated with the iridium oxide (IrO ₂ ) layer is divided into an upper region and a lower region, and _{the pores in the upper region of the Ti layer electroplated with the iridium oxide (IrO 2} ) layer are partially filled with the electrolyte of the electrolyte membrane. And, the pores in the lower region of the electroplated Ti layer of the iridium oxide (IrO ₂ ) layer are not filled with the electrolyte of the electrolyte membrane,
In the upper region of the Ti layer on which the iridium oxide (IrO _{2 ) layer is electroplated, t ME, which} is the average vertical thickness of the ME region, where the pores are partially filled with the electrolyte of the electrolyte membrane, has a thickness of 25 μm or more and 30 μm or less. Will,
Part of the iridium oxide (IrO ₂ ) layer is located in the upper region,
The remaining part of the iridium oxide (IrO ₂ ) layer is located in the lower region, a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.
The method of claim 1,
The IrO ₂ layer is a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device containing 0.01 to 1.05 mg /cm ^{2 of iridium oxide loaded on the Ti layer.}
The method of claim 1,
The Ti layer is a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device of titanium mesh or titanium paper.
delete delete The method of claim 1,
A method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device, wherein the Ti layer of the oxygen electrode includes a plurality of pores.
The method of claim 1,
The compression process is performed for 1 to 5 minutes under a temperature condition of 120 ~ 160 ℃, a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.
The method of claim 1,
The compression process is performed under a pressure condition of 4 to 20 MPa, a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.
delete The method of claim 1,
The _{process of electroplating IrO 2} is performed for 1 minute to 10 minutes under a plating voltage condition of 0.5 to 0.9 V _SCE , a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.
delete The method of claim 1,
Before electroplating IrO ₂ , the Ti layer is immersed in oxalic acid and then washed with ionized water, a method of manufacturing a membrane electrode assembly for a proton exchange membrane water electrolysis device.

Images