KR102098708B1 - Electrode structure control technology for fuel cell and manufacturing method - Google Patents

Abstract

The present invention relates to a membrane electrode assembly for a fuel cell and a method for manufacturing the same, and more particularly, to include a patterned catalyst layer having an in-plane channel structure, and a membrane electrode assembly for a fuel cell with improved mass transfer and output performance. And a method of manufacturing the same. The membrane electrode assembly including the catalyst layer having an in-plane channel structure according to the present invention improves material transfer characteristics and can significantly improve output performance even in a membrane electrode assembly carrying a small amount of Pt. In addition, while patterning the polymer membrane has been used in other fields, there has never been a case of patterning a porous fragile electrode, through which various structures can be generated on the electrode, and the base technology for electrode structure control and optimization Can be

Description

Electrode structure control technology for fuel cell and manufacturing method

The present invention relates to a membrane electrode assembly for a fuel cell and a method for manufacturing the same, and more particularly, to include a patterned catalyst layer having an in-plane channel structure, and a membrane electrode assembly for a fuel cell with improved mass transfer and output performance. And a method of manufacturing the same.

Fuel cells have been seen as promising candidates for eco-friendly power generation systems. Among various fuel cell systems, polymer electrolyte membrane fuel cells (PEMFC) have advantages such as proper operating temperature, high power density and high mechanical robustness due to the use of flexible polymer electrolyte membranes (Steele, BC et. al., Nature 2001, 414 (6861), 345-352; Perry, ML et al., Journal of the electrochemical society 2002, 149 (7), S59-S67; Wee, J.-H., Renewable and sustainable energy reviews 2007, 11 (8), 1720-1738; Kirubakaran, A. et al., Renewable and Sustainable Energy Reviews 2009, 13 (9), 2430-2440). For this reason, PEFMC has been intensively studied for decades and commercialized in the fields of power generation and automobiles (Ticianelli, E. et al., Journal of the Electrochemical Society 1988, 135 (9), 2209-2214; Costamagna, P. et al., Journal of power sources 2001, 102 (1), 253-269; Winter, M. et al., What are batteries, fuel cells, and supercapacitors? ACS Publications: 2004). However, expensive platinum catalysts are a major barrier to the widespread use of PEFMC systems. One way to solve this cost problem is to develop a membrane electrode assembly (MEA) carrying platinum while minimizing performance degradation. However, reducing platinum loading in MEA is usually accompanied by significant loss in MEA output performance due to increased kinetic and mass transfer polarization (Billy, E. et al., Journal of Power) Sources 2010, 195 (9), 2737-2746; Ono, Y. et al., Ecs Transactions 2010, 28 (27), 69-78; Brouzgou, A. et al., Applied Catalysis B: Environmental 2012, 127, 371-388). Therefore, the development of an improved catalyst layer with high activity and an improved catalyst layer (CL) structure with improved mass transfer properties is very important to achieve a catalyst layer carrying a small amount of Pt (Lefevre, M. et al., Science) 2009, 324 (5923), 71-74; Kim, HY et al., Small 2016, 12 (38), 5347-5353; Gan, L. et al., Small 2016, 12 (23), 3189-3196; Choi, K.-H. et al., Chemical Communications 2016, 52 (3), 597-600; Bayatsarmadi, B. et al., Small 2017; Tian, ZQ et al., Advanced Energy Materials 2011, 1 (6 ), 1205-1214; Kim, O.-H. et al., Nature communications 2013, 4, 2473; Choo, MJ et al., ChemSusChem 2014, 7 (8), 2335-2341; Choo, MJ et al. , ChemElectroChem 2015, 2 (3), 382-388).

Mass transfer in the catalyst layer is a complex process in which gas and water travel through pores of various scales and ionomer thin films are involved. The catalytic layer through a thin ionomer film covered with Pt particles and the Knudsen diffusion through the meso / macro pores of membrane diffusion have been of great interest to MEAs carrying small amounts of Pt. However, the mass transfer of the catalyst layer is influenced by the flow field and the gas diffusion layer (GDL). This is typically one of the fundamental problems of PEMFC, as evidenced by the channel / rib effect. Below the rib region of the flow plate, the gas diffusion layer was compressed due to contact pressure, gas and water were transferred from the compressed gas diffusion layer, and the underlying catalyst layer region was suppressed (Sinha, PK et al., Electrochemical and Solid-State) Letters 2006, 9 (7), A344-A348; Nitta, I. et al., Fuel Cells 2008, 8 (6), 410-421; Wang, L. et al., Journal of Power Sources 2008, 180 (1 ), 365-372; Higier, A. et al., Journal of Power Sources 2009, 193 (2), 639-648; Mahmoudi, A. et al., Energy Conversion and Management 2016, 110, 78-89). Recently, Yoshida et al. Reported a three-dimensional fine mesh flow field capable of alleviating the channel / rib effect by minimizing the flow field / gas diffusion layer contact area (Yoshida, T. et al., The Electrochemical Society Interface) 2015, 24 (2), 45-49). However, even in the case of a mesh type flow field, since the electrical contact between the flow field and the gas diffusion layer is essential, gas diffusion layer compression cannot be completely avoided. Therefore, in order to use a portion of the catalyst layer more efficiently under the compressed gas diffusion layer, in-plane mass transfer must be used in the catalyst layer.

The present invention provides a patterned catalyst layer (PCL) having an in-plane channel structure in order to improve the output performance of MEA carrying a small amount of Pt. A key feature of the catalyst layer is that in-plane channels are engraved in the catalyst layer while improving the use of a portion of the catalyst layer under a compressed gas diffusion layer. A line pattern was formed directly on the catalyst layer by casting the catalyst layer slurry into an inverse patterned mold and transferring the catalyst layer to a membrane. Figure 1 shows the structural characteristics of the catalyst layer according to an embodiment of the present invention. The in-plane channels of the catalyst layer provide efficient in-plane mass transfer between the catalyst bed segments under compressed and uncompressed gas diffusion layers. Previously, some attempts have been made to produce a patterned catalyst layer structure by forming a patterned membrane surface and then forming a catalyst layer coating on the membrane surface (Shah, K. et al., Journal of power sources 2003, 123 (2), 172-181; Bae, JW et al., Journal of Industrial and Engineering Chemistry 2012, 18 (3), 876-879; Cho, H. et al., Nature communications 2015, 6, 8484; Seo , J. et al., ACS applied materials & interfaces 2016, 8 (26), 16656-16663; Jang, S. et al., ACS applied materials & interfaces 2016, 8 (18), 11459-11465; Kim, SM et al., Journal of Power Sources 2016, 317, 19-24). However, the patterned catalyst layer structure derived from the patterned membrane does not have high structural accuracy due to structural changes in the membrane that change during the catalyst layer coating and drying process. Compared to previous catalyst layer patterning techniques, recent patterning methods can have higher structural fidelity due to the use of dimensionally stable substrates for catalytic layer patterning.

Accordingly, the present inventors have a membrane electrode assembly including a catalyst layer having an in-plane channel structure, which improves material transfer characteristics, and can significantly improve output performance even in a membrane electrode assembly carrying a small amount of Pt. It has been confirmed that the catalyst layer patterning strategy can be a multi-purpose platform for advanced fuel cell development, and the present invention has been completed.

An object of the present invention is to provide a membrane electrode assembly for a fuel cell with improved mass transfer characteristics and output performance.

Another object of the present invention is to provide a method of manufacturing a membrane electrode assembly for a fuel cell.

Another object of the present invention is to provide a fuel cell including a membrane electrode assembly manufactured by the above method.

In order to achieve the above object, the present invention is a polymer electrolyte membrane; A catalyst layer disposed in contact with one surface of the polymer electrolyte membrane; And a patterned catalyst layer disposed in contact with the back surface of the polymer electrolyte membrane and having an in-plane channel structure.

The present invention also, (a) manufacturing a patterned first substrate; (b) plasma treating the manufactured first substrate; (c) depositing a hydrophobic chemical on the plasma-treated first substrate; (d) spraying a catalyst layer ink on the deposited first substrate to form a catalyst layer on the first substrate; (e) laminating a polymer electrolyte membrane on one surface of the catalyst layer formed on the first substrate; (f) forming a catalyst layer on the second substrate; (g) laminating a catalyst layer formed on the second substrate on one surface of the laminated polymer electrolyte membrane; (h) decal transfer of the catalyst layer formed on the first substrate, the polymer electrolyte membrane and the catalyst layer formed on the second substrate; And (i) removing the first substrate and the second substrate.

The present invention also, the membrane electrode assembly; And it provides a fuel cell including a separator (separator) or a bipolar plate (bipolar plate).

The membrane electrode assembly including the catalyst layer having an in-plane channel structure according to the present invention improves material transfer characteristics and can significantly improve output performance even in a membrane electrode assembly carrying a small amount of Pt. In addition, while patterning the polymer membrane has been used in other fields, there has never been a case of patterning a porous fragile electrode, through which various structures can be generated on the electrode, and the base technology for electrode structure control and optimization Can be

1 shows a schematic diagram of mass transfer through an in-plane channel structure catalyst layer and an in-plane channel according to an embodiment of the present invention.
Figure 2 shows a SEM image and a digital image and the manufacturing process of the in-plane channel structure patterned catalyst layer according to an embodiment of the present invention.
Figure 3 shows the results of measuring the battery configuration and iV polarization curve and oxygen gain according to an embodiment of the present invention.
Figure 4 shows the sum of the total oxygen transfer resistance, molecular diffusion resistance and knucene and film diffusion resistance of the battery configuration according to an embodiment of the present invention.
Figure 5 shows the water contact angle of the original patterned substrate and the hydrophobic patterned plate according to an embodiment of the present invention.
6 is a cross-sectional SEM image of a flat catalyst layer according to an embodiment of the present invention.
7 shows Nyquist plots and CV curves of a battery configuration according to an embodiment of the present invention.
8 is a cross-sectional SEM image of the patterned catalyst layer after the battery operation according to an embodiment of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

The following abbreviations are used in the specification of the present invention.

CL: catalyst layer

FCL: flat catalyst layer

PCL: patterned catalyst layer

PA-PCL: Channel direction and flow field direction in PCL are parallel

PE-PCL: Channel direction and flow field direction in PCL are vertical (perpendicular)

CCM: catalyst coated membrane

MEA: membrane electrode assembly

GDL: gas diffusion layer

PUA: Polyurethane acrylate (poly (urethane acrylate))

PDMS: polydimethylsiloxane

FEP: fluorinated ethylene polymer

ECSA: electrochemical surface area

CV: cyclic voltammetry

RH: relative humidity

In the specification of the present invention, the fuel cell is manufactured in a form in which various parts are stacked. At this time, the stacked direction, that is, the vertical direction through the membrane-electrode means the through-plane direction, and the in-plane direction is perpendicular to this. It means the direction formed in the plane. Therefore, the catalyst layer according to the present invention has a pattern formed on the surface of the catalyst layer, and is particularly formed on the surface in contact with the gas diffusion layer.

In the present invention, there is a difference in that the electrode is patterned directly rather than the polymer membrane of a conventional fuel cell, and the catalyst layer having an in-plane channel has a catalyst layer ink (slurry) on a surface-treated substrate having a retrograde pattern. Is coated and dried to form a patterned catalyst layer, and exhibits excellent output performance at high current density compared to an unpatterned flat catalyst layer (FCL). It was confirmed that the membrane electrode assembly (MEA) including -patterned catalyst layer (IC-CL) has a remarkable improvement in mass transfer characteristics by an in-plane channel engraved on the catalyst layer. In addition, the oxygen gain is more pronounced when the channel direction of the patterned catalyst layer is perpendicular to the flow field direction, indicating that the in-plane channel increases the utilization of the catalyst layer under the rib region, and the oxygen transfer resistance analysis ( Oxygen transport resistance analysis) indicates that the introduction of in-plane channels can promote molecular and Knudsen diffusion. In addition, while patterning the polymer membrane has been used in other fields, there has never been a case of patterning a porous fragile electrode, through which various structures can be generated on the electrode, and the base technology for electrode structure control and optimization I confirmed that this could be.

Therefore, the present invention, in one aspect, a polymer electrolyte membrane; A catalyst layer disposed in contact with one surface of the polymer electrolyte membrane; And a patterned catalyst layer disposed in contact with the back side of the polymer electrolyte membrane and having an in-plane channel structure.

In the present invention, the amount of the noble metal catalyst supported in the patterned catalyst layer is preferably 0.01 to 5 mg / cm ² , more preferably 0.01 to 0.20 mg / cm ² , and most preferably 0.162 to 0.170 mg / cm ² Do.

The noble metal catalyst is preferably at least one selected from the group consisting of platinum (Pt), palladium (Pd), platinum alloy and palladium alloy, and platinum-catalyst catalysts include platinum-cobalt (Pt-Co), platinum-ruthenium ( Pt-Ru) and the like, and any precious metal catalyst commonly used in the fuel cell field or an alloy containing a precious metal catalyst may be used without being limited thereto.

In the present invention, it is preferable that some or all of the channels of the patterned catalyst layer are formed in a direction crossing the land portion of the bipolar plate.

In the present invention, the channel direction of the patterned catalyst layer is preferably perpendicular to each other (perpendicular) or parallel (parallel) with the direction of the flow field, but is not limited thereto.

In the present invention, the patterned catalyst layer is preferably prepared by coating the catalyst layer on a patterned substrate and transferring the patterned catalyst layer to a membrane.

In the present invention, the catalyst layer disposed in contact with one surface of the polymer electrolyte membrane may be a patterned catalyst layer having an in-plane channel structure, wherein the membrane electrode assembly for a fuel cell includes a polymer electrolyte membrane and the polymer electrolyte. It may be disposed in contact with both sides of the membrane, and may include a patterned catalyst layer having an in-plane channel structure.

In another aspect, the present invention, (a) manufacturing a patterned first substrate; (b) plasma treating the manufactured first substrate; (c) depositing a hydrophobic chemical on the plasma-treated first substrate; (d) spraying a catalyst layer ink on the deposited first substrate to form a catalyst layer on the first substrate; (e) laminating a polymer electrolyte membrane on one surface of the catalyst layer formed on the first substrate; (f) forming a catalyst layer on the second substrate; (g) laminating a catalyst layer formed on the second substrate on one surface of the laminated polymer electrolyte membrane; (h) decal transfer of the catalyst layer formed on the first substrate, the polymer electrolyte membrane and the catalyst layer formed on the second substrate; And (i) removing the first substrate and the second substrate.

In the present invention, the first substrate is preferably a poly (urethane acrylate) (PUA) or a polydimethylsiloxane (PDMS), and a poly (urethane acrylate) (PUA) is more preferable.

In the present invention, it is preferable that the patterned first substrate is spin-coated a curable solution on a PET film, and then put a patterned silicone master mold on a cast and then cured, and the silicone master mold is PDMS (polydimethylsiloxane). ), PUA (polyurethane acrylate) or polysilicon wafer is preferred, and PDMS (polydimethylsiloxane) is more preferred.

In the present invention, the plasma treatment is preferably an oxygen (O ₂ ) plasma treatment.

In the present invention, the hydrophobic chemical is preferably a C ₈ H ₄ F ₁₃ SiCl ₃ or fluoro carbon compound, C ₈ H ₄ F ₁₃ SICl ₃ is more preferred, and the fluoro carbon compound is a fluoro carbon-based material It can be used without being limited.

In the present invention, the catalyst layer ink preferably includes a Pt / C catalyst and a Nafion solution, and the Pt / C catalyst has a Pt content of 46.9 wt%, and the Nafion solution contains a solid content of 3 wt%. Nafion solution having a more preferred.

In the present invention, it is preferable to further include a step of forming a catalyst layer on the first substrate and then removing the residual solvent by annealing at 130 ° C. for 4 hours.

In the present invention, the second substrate is preferably PI (polyimide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate) or FEP (fluorinated ethylene propylene), more preferably PI (polyimide).

In another aspect, the present invention, the membrane electrode assembly produced by the method; And it relates to a fuel cell comprising a separator (separator) or a bipolar plate (bipolar plate).

The present invention relates to a novel catalyst layer (CL) having an in-plane flow channel to improve mass transfer in polymer electrolyte membrane fuel cells (PEMFC). The catalyst layer CL having an in-plane channel on the surface coats the catalyst layer CL slurry on the surface-treated substrate having an inverse line pattern, and the dried catalyst layer CL is removed from the substrate. It is prepared by delivery to a membrane. Membrane electrode assembly with an in-plane channel-patterned catalyst layer (IC-CL) that exhibits superior output performance at high current densities compared to an unpatterned flat catalyst layer (FCL) (membrane electrode assembly, MEA) proved that the mass transfer property by the in-plane channel engraved on the catalyst layer was significantly improved. The performance gain becomes more pronounced when the channel direction is perpendicular to the flow field direction, indicating that the in-plane channel increases the utilization of the catalyst bed under the rib region. Oxygen transport resistance analysis indicates that the introduction of in-plane channels can promote molecular and Knudsen diffusion. The direct catalyst layer patterning technology provides an improved catalyst layer structure manufacturing platform with high structural fidelity and design flexibility, and a reasonable guideline for high performance catalyst layer design.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.

Example 1: Preparation of a membrane electrode assembly comprising an in-plane channel-structured patterned catalyst layer

The biggest challenge is to manufacture the in-plane channel structure PCL with high structural accuracy, and it is difficult to engrave the pattern on the CL without causing structural damage due to the high vulnerability of the porous CL. In order to solve this problem in this embodiment, as shown in FIG. 2A, a new manufacturing process was developed in which CL is coated on a patterned substrate and PCL is transferred to a film.

1-1. Preparation of patterned substrates

The patterned PUA substrate is spin-coated with a curable PUA solution (MINS-311RM) on a PET film (SKC KOREA) at 1000 rpm for 1 minute, and a patterned PDMS master mold on a PUA cast is placed, followed by UV for 10 minutes. It was prepared by curing. After removing the PDMS mold from the patterned PUA layer on the PET film, the PUA surface was treated with O ₂ plasma (MyPL-150, APPLASMA), followed by hydrophobic chemicals (C ₈ H ₄ F ₁₃ SiCl) for 3 minutes at room temperature under vacuum. _3, SIT8174.0, Gelest Inc.) by chemical vapor deposition.

1-2. Preparation of patterned catalyst layer and membrane electrode assembly

The cathode catalyst layer was coated on a hot plate (150 ° C) by spraying a catalyst layer ink containing a Pt / C catalyst (46.9 wt% Pt, Tanaka Kikinzoku Kogyo) and a Nafion solution (D520 ™, Dupont) having a solids content of 3 wt%. It was formed on the patterned and surface-treated PUA substrate fixed to the. The cathode catalyst layer ink was homogeneously dispersed by tip sonication 2 hours before use. The ionomer / carbon ratio (I / C ratio) of the ink was set to 1.0. After coating the catalyst layer, the catalyst layer on the PUA substrate was annealed at 130 ° C. for 4 hours to remove residual solvent. The anode catalyst layer was formed on a FEP film by casting the same catalyst layer slurry mixed with a ball milling process, and dried in an oven at 60 ° C. for 12 hours. CCM was prepared by a decal transfer method. The cathode catalyst layer on the PUA substrate, the Nafion 211 membrane (25 μm thick, Dupont ™) and the stack of anode catalyst layers on the polyamide substrate were pressed at 130 ° C., 25 atm for 10 minutes, and the PUA and polyimide substrates were removed from the laminate. . The active area of CCM is 12.25 cm ² .

To characterize the structure of the patterned substrate and the patterned catalyst layer, an electrospinning scanning electron microscope (FE-SEM, Sirion, FEI) was used. The supported amount of Pt in the catalyst layer was 0.166 ± 0.004 mg _Pt cm ^-2 . A single cell is assembled with a CCM, a pair of GDLs (JNT20-A3, JNTG), a pair of rigid gaskets, a pair of graphite blocks with a single serpentine flow field, and a pair of end plates with 8 screws. Did. The single cell was fixed at a torque pressure of 75 kgf cm ^-1 .

The patterned PUA substrate was prepared by nanoimprint technology from a silicon master mold. The curable PUA was spin coated onto a flat PET film and the PDMS mold was placed on the cast. After curing of the PUA, the patterned PUA layer (˜10 μm) supported by the PET film (˜100 μm) was peeled from the PDMS master pattern. The uniformity of the patterned PUA thickness determines the quality of the final CL. The change in thickness results in a local collapse of CL by applying more pressure to the thicker portion during decal delivery. To obtain high thickness uniformity of the PUA substrate, a spin coating process was used. 2B and 2C show that the fabricated PUA substrate has a very uniform thickness and a clear channel structure. In addition, a pressure distribution layer of the FEP film was inserted during the decal transfer process to relieve the pressure distribution. Another important step for high quality CL patterning is proper wetting of the CL ink and surface treatment of the PUA substrate, which can easily separate the dried CL from the PUA substrate. For surface modification, a hydroxyl group surface functional group was first formed on a patterned PUA through oxygen plasma treatment, and then C ₈ H ₄ F ₁₃ SiCl ₃ capable of forming a chemical bond with a hydroxyl group was deposited by chemical vapor deposition. As shown in FIG. 5, the contact angle of the water was changed from 87 ° to 98 ° after surface treatment, through which surface modification was confirmed. A typical effect of surface modification is shown in Figure 2d. It was confirmed that the CL coated on the hydrophobic treated PUA substrate was completely transferred to the film, which was in contrast to the partial CL delivery to the untreated PUA substrate.

The PCL delivered by the CCM shows a vivid prism on the surface (FIG. 2E), and it can be confirmed that a regular pattern was formed. The structure of PCL and the prepared CCM were investigated using SEM. As shown in Figure 2f, a very neat and regularly arranged planar channel was successfully formed in the PCL. The surface of PCL was very porous as observed in conventional CL (FIG. 2G). After decal delivery, no local densification or local degradation to PCL was observed. As a result of SEM image measurement of PCL, the channel depth, width and spacing were 1.8 μm, 1.5 μm and 2.6 μm, respectively (FIG. 2H). The values were close to the silicon master pattern (1.8 μm depth, 1.5 μm width, 2.7 μm spacing) values, indicating a high structural accuracy of the CL patterning method impossible with previous manufacturing strategies. The cross-sectional SEM image of the CCM confirmed that the PCL had a very uniform thickness (3.0 ± 0.4 μm), and an interfacial bond in close contact with the membrane was formed (FIG. 2i). For comparison, an unpatterned FCL having the same Pt loading amount was prepared. The SEM images of the FCL and the corresponding CCM are shown in Figure 6, and the thickness of the FCL was 2.4 ± 0.2 μm.

Example 2: Single cell operation and electrochemical analysis

2-1. Single cell operation

Break-in and iV polarization experiments were performed using a fuel cell test station (Scitech Korea). The break-in experiment was performed by injecting hydrogen / oxygen (H ₂ / O ₂ , 300/1000 sccm) into the cell at a constant flow rate and sweeping the cell voltage at 50 mV s ⁻¹ between 0.07 and 1.2 V 10 times. . The iV polarization curve was measured at an absolute pressure of 180 kPa, 80 ° C. and relative humidity of 50% and 100%. The stoichiometric coefficient of the feed gas is 1.5 for both hydrogen and air. For a current density of 400 mA cm ^-2 or less, hydrogen (H ₂ , 57 sccm) and air (air, 137 sccm) equivalent to a stoichiometric coefficient of 1.5 at 400 mA cm ^-2 were used at a constant flow rate. The iV polarization curve was obtained by increasing the current density in 10mA cm ^-2 units that can stabilize the cell when measuring the cell voltage. For stabilization, two minutes were spent at a current density of 0.1 A cm ^-2 or less, and three minutes were spent at a current density of 0.1 A cm ^-2 or more, respectively.

2-2. Electrochemical analysis

Electrochemical characterization was performed using potentiostat (HCP-803, BioLogics Science Instrument). In order to quantify the proton transfer resistance of the catalyst layer, hydrogen / nitrogen (H ₂ / N ₂ , Electrochemical impedance spectroscopy (EIS) was measured in OCV with counter / working, 500/1500 sccm) feed. Electrochemical surface area (ECSA) was calculated from cyclic voltammetry (CV) measurements of a single cell under an atmosphere of hydrogen (anode, 100 sccm) / nitrogen (cathode, 0 sccm). The oxygen transfer resistance of the catalyst layer was obtained by limiting current method; Linear sweep voltammetry was performed by injecting excess hydrogen (500 sccm) and diluted oxygen (1% oxygen in nitrogen or helium, 650 sccm) into the anode and cathode at 150 kPa absolute, respectively, at various temperatures ( 50, 60, 70 and 80 ° C.) and 90% relative humidity at a scan rate of 5 mV s ⁻¹ at OCV to 0.15 V and measured for a single cell.

The effect of in-plane channels on output performance in CL is a major concern of the present invention. To demonstrate the effect, the directions of the in-plane channels were arranged vertically or parallel to the direction of a single serpentine flow field, denoted PE-PCL and PA-PCL, respectively (FIG. 3A). FCL may have a channel / rib effect due to local compression of GDL under the rib region. In the case of PA-PCL, the in-plane channel of PCL does not cross the rib region. Therefore, in-plane mass transfer through the channel between the channel and the CL segment below the rib region is not allowed. However, the patterned structure may affect the mass transfer of CL in the thickness direction, which is called a 'through-plane effect'. On the other hand, the PE-PCL configuration provides an in-plane channel across the rib and channel regions. Thus, mass transfer can occur in the plane between the rib and the CL segment below the channel region.

Since the effect of the in-plane channel on the mass transfer in CL is the main focus of the present invention, the proton conduction and catalytic activity of CL are carefully controlled independent of the three (FCL, PA-PCL, PE-PCL) cell configurations. Did. The proton conduction resistance (R _CL ) and ohm resistance (R _ohm ) of _CL were measured from AC impedance at an open circuit voltage (OCV) under an H ₂ / N ₂ (positive / negative) atmosphere. R _ohm was the largest contribution between film resistance and interface resistance, and was determined from the intercept of the high-frequency impedance of the X-axis in a Nyquist plot. As shown in Figure 7A, the sections for the three cells were nearly identical due to the use of the same membrane and membrane / CL interface structures. R _CL is three times the distance between the high-frequency section and the section of the asymptote extending at a slightly inclined low-frequency impedance on the X-axis. R _CL values (FCL; 0.0147 Ωcm2, PA-PCL; 0.0190 Ωcm2, PE-PCL; 0.0166 Ωcm2) are close to each other and due to the thin CL thickness, R _ohm values (FCL; 0.0563 Ωcm2, PA-PCL; 0.0535 Ω Cm2, PE-PCL; 0.0551 Ωcm2). Thus, proton transfer in CL does not significantly affect the polarization behavior of CL and does not cause significant power performance differences between the three cells. The electrochemical surface area (ECSA) of CL was measured by cyclic voltammetry (CV) technology. The value for ESCA was quantified from the amount of charge for the electrosorption of hydrogen on the Pt surface. As shown in Figure 7B, the CV curves of FCL, PA-PCL and PE-PCL are similar ECSA values for CL (FCL; 54.8 m ² g ^-1 , PA-PCL; 55.1 m ² g ^-1 , PE- PCL; 58.7 m ² g ⁻¹ ) was almost the same. This electrochemical analysis confirms that the CL compared in the present invention has similar proton conduction properties and catalytic activity, and is properly designed to investigate the effect of in-plane channels on mass transfer properties.

3B and 3C show the iV polarization curves of FCL, PA-PCL and PE-PCL at 50% and 100% relative humidity (RH), respectively. Polarization was measured at a stoichiometric coefficient of 1.5 / 1.5 for hydrogen / air feed and an absolute pressure of 180 kPa. The comparison of the two RH conditions is to understand how the in-plane channel in CL affects the water overflow behavior. A relatively low air stoichiometry factor of 1.5 was chosen to amplify the mass transfer resistance for a clearer detection of the in-plane channel effect. Overall, the output performance was independent of the low current density region, but varied greatly in the high current density region depending on the CL structure and cell configuration. Specifically, at 50% RH, the iV curves of the three cells overlap each other below 0.6 Acm ^-2 , indicating that the kinetic and ohmic polarizations of the cells from impedance and CV analysis are almost the same as expected. Shows. Above 0.6 Acm ^-2 , PE-PCL showed higher output performance than FCL and PA-PCL, indicating that the mass transfer polarization is smaller. However, PA-PCL showed no significant improvement over FCL. Therefore, the in-plane effect was clearly observed at 50% RH, but the through-plane effect was not apparent. At 100% RH, the in-plane channel effect was more pronounced. Below 0.2 Acm ^-2 , iV polarization was identical to that observed in the 50% RH results. PE-PCL and PA-PCL showed higher output performance than FCL at 0.2 Acm ^-2 or more, and proved to exist both in-plane and through-surface effects during high RH operation. The error bars in the iV polarization curve indicate the degree of voltage fluctuation during constant current measurement at each current density. Voltage fluctuations can be an indicator of water flooding as they reflect the dynamic process of accumulation and removal of liquid water. The polarization curve at 100% RH showed a larger error bar than the polarization curve at 50% RH, and more marked water overflow at high RH conditions. 3B and 3C confirmed that the voltage fluctuation at a fixed current density is decreased in the order of FCL>PA-PCL> PE-PCL, so that the in-plane channel can effectively mitigate water overflow.

The comparison between FCL and PA-PCL shows the through face effect. It is clear that at 100% RH mass transfer can be facilitated by the through-surface effect. In contrast, at 50% RH, the penetration surface effect is not clear. These results suggest that moisture removal from CL can be promoted by the channel structure. Due to the extended external surface area of PCL, the evaporation of water from CL to the bulk gas phase can be promoted. The in-plane effect of mass transfer through the channel connecting the channel and the rib region was verified by comparison of PA-PCL and PE-PCL. PE-PCL showed higher output performance than PA-PCL confirming the presence of in-plane effect, regardless of RH conditions. The large difference in cell voltage at 50% RH indicates that gas transfer from the channel region to the rib region can lead to higher utilization of CL segments below the rib region at high current densities. At 100% RH, the in-plane effect was more pronounced; Improved output performance with a vertical configuration and reduction in error bar size became more important at higher RHs. This means that the in-plane channel across the channel and rib region can improve the overall gas and water transfer.

To further confirm the in-plane and through-plane effects, oxygen gain, an indicator of mass transfer polarization, was obtained by subtracting the air feed cell voltage from the oxygen feed cell voltage. 3D and 3E compare the oxygen gains of FCL, PA-PCL and PE-PCL at 50% and 100% RH, respectively. Oxygen gain increases the current density exponentially due to the increase in mass transfer polarization. At 50% RH, the oxygen gain of PE-PCL was higher than that of FCL and PA-PCL at all current densities investigated. In addition, FCL and PA-PCL did not show any difference in oxygen gain. On the other hand, oxygen gain at 100% RH decreased in the order of FCL> PA-PCL> PE-PCL. These results were confirmed once again that the in-plane effect contributes to both gas and water transfer, and the through-plane effect mainly contributes to water transfer, which is very consistent with the iV polarization analysis result. After iV polarization measurement, the cell was disassembled and the structure of PCL was investigated by SEM to preserve the in-plane channel structure under cell compression. Cross-sectional SEM images of the PCL after cell operation showed that the in-plane channel structure was preserved (Figure 8).

To understand the mechanisms of the proven in-plane and through-plane effects of the channel CL structure, molecular diffusion and Knudsen diffusion resistance of FCL, PA-PCL and PE-PCL were analyzed by limiting current method. The total gas delivery resistance (r _Total ) of MEA generally includes three additive contributions: molecular diffusion resistance (r _MD ) from O ₂ delivery through large pores in GDL; Knucene diffusion resistance (r _KD ) through mesopores from O ₂ transfer in microporous layers of GDL and CL; And film diffusion resistance (r _film ) through the ionomer thin film covering the catalyst surface from O ₂ transfer. The sum of r _MD and r _KD and r _film (r _others ) can be quantified by two dilute O ₂ feeds with N ₂ and He balance gas and limiting current method. Since the microstructure of FCL and PCL is very similar to that shown in impedance and CV analysis, it can be assumed that r _film is the same for CL and the difference between r _others is due to the difference of r _KD .

4A, 4B and 4C compare r _total , r _MD and r _others (r _KD + r _film ), respectively. To increase the reliability of the analysis, the resistance was measured at various temperatures. The r _total value decreased in the following order, which was consistent with the iV polarization and oxygen gain analysis results: FCL>PA-PCL> PE-PCL (FIG. 4A). Interestingly, as compared to r _MD indicates the the PE-PCL r _MD considerably smaller than r _MD of the FCL and PA-PCL, which can be recovered by providing a molecular diffusion in-plane gas delivery channel down due to the compressed GDL It is present. Indifference in r _MD between FCL and PA-PCL resulted because molecular diffusion into the CL segment under compressed GDL could not be enhanced for PA-PCL. On the other hand, in the case of PA-PCL and PE-PCL, the r _others values are very similar to each other and significantly smaller than the values of FCL. It can be understood that the in-plane channel structure CL allows for Knudsen diffusion from the top surface of the patterned CL as well as from the sidewalls. Due to the extended diffusion surface, the effective diffusion distance through CL can be shortened for the PCL structure regardless of direction. Thus, there are two proven mass transfer enhancements by the in-plane channel structure: both molecular diffusion and knucene diffusion are accelerated. The double effects provide a design guide for fuel cells carrying a small amount of Pt. The extended outer surface of CL and the in-plane channel connecting the compressed and uncompressed regions can independently and additionally enhance the mass transfer properties. Based on this understanding, in the present invention, a new high-performance CL structure can be more rationally designed.

The present invention developed a direct catalyst layer patterning method and invented an in-plane channel structured catalyst layer. By using the surface treatment of the patterned substrate for coating the catalyst layer, a patterned catalyst layer with high structural accuracy was prepared. Comparing the flat catalyst layer and the two patterned catalyst layers having different in-plane channel directions for the flow field direction, the in-plane channel in the catalyst layer connecting the catalyst layer portion under the flow channel and the catalyst layer portion under the rib facilitates the catalyst layer under the rib. It has been shown that it can provide gas and water transfer. Oxygen transfer resistance analysis showed that the in-plane channel enhances molecular and Kunudsen diffusion in the catalyst layer. These results demonstrated that the direct catalyst layer patterning strategy can be an effective platform for achieving an improved catalyst layer structure with high structural accuracy.

Since the specific parts of the present invention have been described in detail above, it will be apparent to those of ordinary skill in the art that this specific technique is only a preferred embodiment, whereby the scope of the present invention is not limited. will be. Therefore, the substantial scope of the present invention will be defined by the claims and their equivalents.

Claims (16)

Polymer electrolyte membrane;
A catalyst layer disposed in contact with one surface of the polymer electrolyte membrane; And
It is disposed in contact with the back surface of the polymer electrolyte membrane, has an in-plane flow channel structure, and includes a patterned catalyst layer carrying a noble metal catalyst of 0.01 to 5 mg / cm ² ,
The channel direction of the patterned catalyst layer is characterized in that the direction of the flow field is perpendicular or horizontal to each other,
The in-plane flow channel structure is a membrane electrode assembly for a fuel cell, characterized in that formed on the surface opposite to the surface contacting the electrolyte membrane.
delete The membrane electrode assembly for a fuel cell according to claim 1, wherein the noble metal catalyst is at least one selected from the group consisting of platinum (Pt), palladium (Pd), platinum alloy, and palladium alloy.
The membrane electrode assembly for a fuel cell according to claim 1, wherein some or all of the channels of the patterned catalyst layer are formed in a direction crossing the land portion of the bipolar plate.
The membrane electrode assembly for a fuel cell according to claim 1, wherein the patterned catalyst layer is prepared by coating a catalyst layer on a patterned substrate and transferring the patterned catalyst layer to a membrane.
The membrane electrode assembly for a fuel cell according to claim 1, wherein the catalyst layer disposed in contact with one surface of the polymer electrolyte membrane is a patterned catalyst layer having an in-plane channel structure.
(a) preparing a patterned first substrate;
(b) plasma treating the manufactured first substrate;
(c) depositing a hydrophobic chemical on the plasma-treated first substrate;
(d) spraying a catalyst layer ink on the deposited first substrate to form a catalyst layer on the first substrate;
(e) laminating a polymer electrolyte membrane on one surface of the catalyst layer formed on the first substrate;
(f) forming a catalyst layer on the second substrate;
(g) laminating a catalyst layer formed on the second substrate on one surface of the laminated polymer electrolyte membrane;
(h) decal transfer of the catalyst layer formed on the first substrate, the polymer electrolyte membrane and the catalyst layer formed on the second substrate; And
(i) removing the first and second substrates
A method of manufacturing a membrane electrode assembly for a fuel cell according to claim 1 comprising a.
The method of manufacturing a membrane electrode assembly for a fuel cell according to claim 7, wherein the first substrate is PU (polyurethane acrylate) (PUA) or polydimethylsiloxane (PDMS).
8. The method of claim 7, wherein the patterned first substrate is spin-coated a curable solution on a PET film, put a patterned silicon master mold on a cast, and then harden the membrane electrode assembly for a fuel cell. Way.
The method of claim 9, wherein the silicon master mold is a polydimethylsiloxane (PDMS), a polyurethane acrylate (PUA), or a polysilicon wafer.
The method of claim 7, wherein the plasma treatment is oxygen (O ₂ ) plasma treatment.
The method of claim 7, wherein the hydrophobic chemical is C ₈ H ₄ F ₁₃ SiCl ₃ or a fluoro carbon compound.
The method of claim 7, wherein the catalyst layer ink comprises a Pt / C catalyst and a Nafion solution.
The method of claim 7, further comprising the step of forming a catalyst layer on the first substrate, and then annealing at 130 ° C. for 4 hours to remove residual solvent.
The method of manufacturing a membrane electrode assembly for a fuel cell according to claim 7, wherein the second substrate is polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN) or fluorinated ethylene propylene (FEP).
The membrane electrode assembly according to any one of claims 1 and 3 to 6; And a separator or a bipolar plate.

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