Preparation method of gas transmission layer electrode with microporous layer

Abstract

The invention belongs to the field of electrolysis, and particularly relates to a preparation method of a gas transmission layer electrode with a microporous layer, which comprises the following steps: step 1, pretreating a porous titanium substrate; step 2, preparing slurry for a microporous layer; 3, coating the slurry to obtain a gas diffusion layer with a microporous layer; 4, preparing an active layer; the obtained gas transmission layer electrode with the microporous layer comprises a titanium substrate, the microporous layer covering the surface of the titanium substrate and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer. According to the invention, the microporous layer with gas-liquid transmission effect, high conductivity and strong hydrophobicity is prepared on the surface of the titanium-based gas transmission layer through phase conversion and suction filtration methods, so that the noble metal-loaded membrane electrode shows lower electrolytic voltage under high current density.

Description

Technical Field

[0001] This invention belongs to the field of electrolysis, specifically relating to a method for preparing an electrode with a microporous gas transport layer. Background Technology

[0002] In PEM hydrogen production electrolyzers, the porous transport layer (PTL) is a core component, requiring excellent electrical and thermal conductivity, mechanical strength, water / gas transport performance, and corrosion resistance. The PTL significantly impacts voltage efficiency because electron and water / oxygen transport through the PTL affect the ohmic and mass transport overpotentials, respectively. Furthermore, the CL-PTL interface has been found to affect catalyst utilization, thus influencing the kinetic overpotential. To improve the CL-PTL interface contact, microporous layers (MPLs) with smaller pore sizes than the PTL have attracted considerable attention. Improved interface contact can reduce mass transfer and ohmic losses, and increase catalyst utilization. Numerous studies have confirmed the impact of MPLs on mass transfer and ohmic losses. The presence of MPLs increases interface contact by 20%, thereby improving mass transfer characteristics. Simultaneously, MPLs play a positive role in improving catalyst utilization. Due to the requirement for low noble metal loading, there is currently a lack of effective commercially available conductive catalyst supports; therefore, utilizing MPLs to provide in-plane electronic conductivity between catalyst particles under low loading, thereby achieving high catalyst utilization, becomes possible. However, poor in-plane electronic conductivity in the microporous layer may lead to a fatal loss of catalyst utilization. The microporous layer structure is also closely related to the mass transfer process of bubble removal, i.e., electrolysis. Existing technologies cannot meet the problems of poor interfacial conductivity, high contact resistance, and increased electrolysis voltage caused by bubble accumulation under high current density in the application of low-noble metal loaded membrane electrodes. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method for preparing a microporous gas transport layer electrode. By employing phase inversion and filtration methods, a microporous layer with gas-liquid transport function, high conductivity, and strong hydrophobicity is prepared on the surface of a titanium substrate, enabling the noble metal-loaded membrane electrode to exhibit a lower electrolysis voltage under high current density.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An electrode with a microporous gas transport layer includes a titanium substrate, a microporous layer covering the surface of the titanium substrate, and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer.

[0006] A method for preparing an electrode with a microporous gas transport layer includes the following steps:

[0007] Step 1: Pre-treat the titanium substrate;

[0008] Step 2: Prepare the slurry for the microporous layer;

[0009] The microporous layer slurry is composed of the following components by mass percentage: 5%–15% conductive powder, 5%–15% polysulfone, 0.1%–1.05% ionomer, and 120%–150% N-methylpyrrolidone as solvent;

[0010] Step 3, slurry coating: The microporous layer slurry prepared in step 2 is filtered from one side of the titanium substrate pretreated in step 1 to the other side for coating; the coated titanium substrate is heated and then quickly transferred to deionized water to achieve the reverse inversion, resulting in a gas diffusion layer with microporous layer; the gas diffusion layer with microporous layer is sintered at high temperature under vacuum and then cleaned to remove surface impurities.

[0011] Step 4, preparation of active layer: a noble metal supported catalyst with catalytic activity is distributed on the surface of the microporous layer of the gas diffusion layer in step 3 to obtain a noble metal dispersed microporous gas transport layer electrode.

[0012] Preferably, the pretreatment involves immersing the titanium substrate in a dilute hydrochloric acid solution for surface treatment, followed by ultrasonic cleaning, and finally rinsing thoroughly with deionized water and drying.

[0013] Preferably, in step 2, the microporous layer slurry is prepared by: weighing ionomer and polysulfone by mass percentage and dissolving them in N-methylpyrrolidone at low speed for 4 hours, then adding conductive powder, dispersing the solution at high speed for 6 hours, and finally degassing to prepare a uniformly mixed microporous layer slurry.

[0014] Preferably, the ionic polymer consists of 0.05% to 1% polyvinylpyrrolidone and 0.05% other ionic polymers by mass.

[0015] Preferably, the other ionic polymers include one or a combination of several of polytetrafluoroethylene dispersions, naphthol solutions, and perfluorosulfonic acids.

[0016] Preferably, the conductive powder comprises one or a combination of several of the following: titanium suboxide, titanium nitride, titanium carbide, titanium powder and its compound powder, tantalum powder and its compound powder; the conductive powder is preferably in the form of nanosheets, and the particle size of the conductive powder is between 0.05 and 5 μm.

[0017] Preferably, the filtration process in step 3 is vacuum filtration, which requires adding low-speed filter paper or 0.22-1μm nylon filter cloth on the side near the negative pressure, and using the negative pressure to make the conductive powder evenly distributed on the surface of the porous titanium matrix through which the gas and liquid flow.

[0018] Preferably, the active layer comprises compounds of noble metals such as iridium, ruthenium, and platinum, or composite phases thereof with other non-noble metal compounds.

[0019] Preferably, the titanium matrix is ​​a porous material formed by bonding and connecting any one or more of powder-sintered porous titanium, titanium mesh, and titanium fiber felt.

[0020] Beneficial effects:

[0021] This invention prepares a microporous layer adapted to gas-liquid dispersion on the surface of a titanium substrate by phase inversion and vacuum filtration. The vacuum-assisted filtration method utilizes vacuum negative pressure during the filtration process, and the microporous layer structure formed under pressure is more adapted to the gas-liquid two-phase flow transmission, reducing mass transfer resistance.

[0022] In this invention, the presence of a microporous layer serves as a microporous extension of the porous gas diffusion layer, reducing the impact of water and gas flow on the proton exchange membrane. At the same time, the hydrophobic surface in the microporous layer effectively accelerates bubble removal, reduces voltage loss caused by bubble resistance under high current density, facilitates the transport of oxygen evolution intermediates during hydrogen production, and adapts to strong gas and liquid impacts under high current density. By utilizing the good acid resistance, high conductivity, and strong hydrophobicity of the microporous layer, the noble metal-loaded membrane electrode exhibits a lower electrolysis voltage under high current density. Attached Figure Description

[0023] Figure 1 These are the polarization curves of Embodiment 1, Embodiment 2 and Comparative Example 1 of the present invention. Detailed Implementation

[0024] The present invention will be clearly and completely described below with reference to specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0025] The present invention provides an electrode with a microporous gas transport layer, comprising a titanium substrate, a microporous layer covering the surface of the titanium substrate, and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer.

[0026] This invention also provides a method for preparing an electrode with a microporous gas transport layer, comprising the following steps:

[0027] Step 1: Pre-treat the titanium matrix; the titanium matrix is ​​any one or more of the following porous materials formed by bonding together powder sintered porous titanium, titanium mesh, and titanium fiber felt; in this embodiment of the invention, the titanium matrix is ​​preferably titanium fiber felt.

[0028] Specifically, after cutting the titanium substrate into appropriate sizes, immerse it in a 0.5M dilute hydrochloric acid solution at 80°C for 15 minutes. Then, clean the titanium felt PTL material with an ultrasonic bath and ultrasonically clean it with 2-propanol and acetone at ambient temperature for 15 minutes. Finally, rinse it thoroughly twice with deionized water for 15 minutes each time, and dry it overnight in a vacuum oven at 60°C.

[0029] Step 2: Prepare the slurry for the microporous layer;

[0030] The microporous layer slurry is composed of the following components by mass percentage: 5%–15% conductive powder, 5%–15% polysulfone, 0.1%–1.05% ionomer, and 120%–150% N-methylpyrrolidone as solvent; wherein the ionomer is composed of 0.05%–1% polyvinylpyrrolidone and 0.05% other ionomers by mass percentage.

[0031] Other ionic polymers include one or more of polytetrafluoroethylene dispersions, naphthol solutions, and perfluorosulfonic acids; the ionic polymers serve to disperse and form pores; in the embodiments of the present invention, the other ionic polymers are preferably polytetrafluoroethylene dispersions and naphthol solutions.

[0032] The conductive powder includes one or a combination of several of the following: titanium suboxide, titanium nitride, titanium carbide, titanium powder and its compound powder, tantalum powder and its compound powder; the conductive powder is preferably in the form of nanosheets, and the particle size of the conductive powder is between 0.05 and 5 μm; in the embodiments of the present invention, the conductive powder is preferably titanium suboxide powder, titanium powder, and titanium nitride powder;

[0033] Specifically, the preparation method of the microporous layer slurry is as follows: weigh the ionomer and polysulfone according to the mass percentage and dissolve them in N-methylpyrrolidone at a low speed for 4 hours. Then add the conductive powder, disperse the solution at a high speed for 6 hours, and finally degas to prepare a uniformly mixed microporous layer slurry.

[0034] Step 3, slurry coating: Using vacuum-assisted filtration, conductive powder is evenly distributed on the surface of the porous titanium substrate through which the gas and liquid flow by utilizing vacuum negative pressure. Low-speed filter paper or 0.22-1μm nylon filter cloth needs to be added on the side near the negative pressure; in this embodiment of the invention, 1μm nylon filter cloth is preferred.

[0035] Specifically, the microporous layer slurry prepared in step 2 is filtered from one side of the pretreated titanium substrate in step 1 to the other side for coating. This process is repeated multiple times until the slurry weight loss rate reaches 20%. The coated titanium substrate is then kept still on a heating plate at 40°C for 5–10 minutes, and then rapidly transferred to deionized water at 5°C for 20–30 minutes to achieve phase inversion, resulting in a gas diffusion layer with microporous structure. This layer is then vacuum sintered at 500°C for 3 hours, followed by ultrasonic cleaning with deionized water for 15 minutes on a vacuum filter to remove surface impurities. A microporous layer adapted to gas-liquid dispersion is prepared on the surface of the titanium substrate through phase inversion and vacuum filtration. The vacuum-assisted filtration method utilizes negative pressure during the filtration process, and the resulting microporous structure under pressure is more suitable for gas-liquid two-phase flow, reducing mass transfer resistance.

[0036] Step 4, preparation of the active layer: using methods such as ultrasonic spraying and thermal decomposition, a noble metal supported catalyst with catalytic activity is distributed on the surface of the microporous layer of the gas diffusion layer in step 3 to obtain a noble metal dispersed microporous gas transport layer electrode; wherein, the active layer is composed of compounds of noble metals such as iridium, ruthenium, and platinum, or composite phases of them with other non-noble metal compounds; in the embodiments of the present invention, the noble metal in the active layer is preferably an iridium compound.

[0037] Specifically, first, prepare the active coating solution B: accurately weigh 90 mg of chloroiridium acid and dissolve it in n-butanol solvent, stirring at room temperature until completely dissolved to form a 0.1 mmol / L iridium-based active solution B, which is then stored for later use; then, immerse the gas diffusion layer with a microporous layer obtained in step 3 in the active solution B for 20 min, remove and dry it, and then calcine it in a muffle furnace at 400℃ for 15 min; after immersion and sintering five times, an iridium-dispersed microporous gas transport layer electrode is obtained; or

[0038] Accurately weigh 80 mg of iridium oxide catalyst and disperse it in a mixed solution of 8 μL naphthol, 10 mL water and 5 mL isopropanol. After ultrasonic dispersion for 30 min, spray it onto the gas diffusion layer with microporous layer obtained in step 3 using an ultrasonic sprayer under heating conditions of 70 °C. After drying, the iridium dioxide dispersed microporous gas transport layer electrode is obtained.

[0039] In this invention, the presence of a microporous layer serves as a microporous extension of the porous gas diffusion layer, reducing the impact of water and gas flow on the proton exchange membrane. At the same time, the hydrophobic surface in the microporous layer effectively accelerates bubble removal, reduces voltage loss caused by bubble resistance under high current density, facilitates the transport of oxygen evolution intermediates during hydrogen production, and adapts to strong gas and liquid impacts under high current density. By utilizing the good acid resistance, high conductivity, and strong hydrophobicity of the microporous layer, the noble metal-loaded membrane electrode exhibits a lower electrolysis voltage under high current density.

[0040] The following are preferred embodiments for illustration.

[0041] Example 1

[0042] An electrode with a microporous gas transport layer includes a titanium substrate, a microporous layer covering the surface of the titanium substrate, and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer.

[0043] A method for preparing an electrode with a microporous gas transport layer includes the following steps:

[0044] Step 1: Pre-treatment of the titanium substrate; cut the titanium felt into 100mm diameter circular pieces, immerse the titanium felt in a 0.5M dilute hydrochloric acid solution at 80℃ for 15 minutes, clean the titanium felt PTL material with an ultrasonic bath, and then ultrasonically clean it with 2-propanol and acetone at ambient temperature for 15 minutes. Finally, rinse thoroughly twice with deionized water for 15 minutes each time, and dry overnight in a vacuum oven at 60℃.

[0045] Step 2: Prepare the slurry for the microporous layer;

[0046] Weigh 15 g of polysulfone, 0.1 g of polyvinylpyrrolidone, and 0.05 g of naphthol and dissolve them in 120 g of N-methylpyrrolidone at low speed for 4 h to obtain a homogeneous solution; then weigh 15 g of titanium suboxide powder and add it to the above homogeneous solution. After ultrasonication in a water bath for 30 min, continue stirring to disperse the solution at high speed for 6 h. Finally, place it in a centrifuge to degas and obtain a uniformly mixed microporous slurry.

[0047] Step 3, Slurry Coating: Place a circular nylon filter with a pore size of 1 micrometer in a Buchner funnel, wet it with ethylene glycol to achieve a negative pressure state, place the pretreated titanium felt in it, add the microporous layer slurry at a low speed, after complete filtration, remove the filtrate and filter it again, then remove the coated titanium felt and place it on a heating plate at 40°C for 10 minutes, then quickly transfer it to deionized water at 5°C for 20 minutes to achieve reverse inversion, and obtain a gas diffusion layer with a microporous layer. After vacuum sintering it at 500°C for 3 hours, ultrasonically clean it with deionized water for 15 minutes on a vacuum filter to remove surface impurities.

[0048] Step 4, preparation of the active layer: First, prepare the active coating solution B: accurately weigh 90 mg of chloroiridium acid and dissolve it in n-butanol solvent, stir at room temperature until completely dissolved to form 0.1 mmol / L iridium-based active solution B, store it for later use; then, immerse the gas diffusion layer with microporous layer obtained in step 3 in active solution B for 20 min, take it out and dry it, and then calcine it in a muffle furnace at 400℃ for 15 min; after immersion and sintering 5 times, the iridium-dispersed microporous gas transport layer electrode is obtained.

[0049] Example 2

[0050] An electrode with a microporous gas transport layer includes a titanium substrate, a microporous layer covering the surface of the titanium substrate, and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer.

[0051] A method for preparing an electrode with a microporous gas transport layer includes the following steps:

[0052] Step 1: Pre-treatment of the titanium substrate; cut the titanium felt into 100mm diameter circular pieces, immerse the titanium felt in a 0.5M dilute hydrochloric acid solution at 80℃ for 15 minutes, clean the titanium felt PTL material with an ultrasonic bath, and then ultrasonically clean it with 2-propanol and acetone at ambient temperature for 15 minutes. Finally, rinse thoroughly twice with deionized water for 15 minutes each time, and dry overnight in a vacuum oven at 60℃.

[0053] Step 2: Prepare the slurry for the microporous layer;

[0054] 10 g of polysulfone, 0.1 g of polyvinylpyrrolidone, and 0.05 g of polytetrafluoroethylene dispersion were weighed and dissolved in 150 g of N-methylpyrrolidone at low speed for 4 h to obtain a homogeneous solution. Then, 10 g of titanium powder (particle size 50 nm) and 5 g of titanium nitride powder (particle size 50 nm) were weighed and mixed, and added to the above homogeneous solution. After ultrasonication in a water bath for 30 min, the solution was further stirred to disperse at high speed for 6 h. Finally, the solution was placed in a centrifuge to remove bubbles and obtain a uniformly mixed microporous slurry.

[0055] Step 3, Slurry Coating: Place a circular nylon filter with a pore size of 1 micrometer in a Buchner funnel, wet it with ethylene glycol to achieve a negative pressure state, place the pretreated titanium felt in it, add the microporous layer slurry at a low speed, after complete filtration, remove the filtrate and filter it again, then remove the coated titanium felt and place it on a heating plate at 40°C for 5 minutes, then quickly transfer it to deionized water at 5°C for 30 minutes to achieve reverse inversion, and obtain a gas diffusion layer with a microporous layer. After vacuum sintering it at 500°C for 3 hours, ultrasonically clean it with deionized water for 15 minutes on a vacuum filter to remove surface impurities.

[0056] Step 4, preparation of active layer: Accurately weigh 80 mg of iridium oxide catalyst and disperse it in a mixed solution of 8 μL naphthol, 10 ml water and 5 mL isopropanol. After ultrasonic dispersion for 30 min, use an ultrasonic sprayer to spray it onto the gas diffusion layer with microporous layer obtained in step 3 under heating at 70 °C. After drying, the iridium dioxide dispersed microporous gas transport layer electrode is obtained.

[0057] Comparative Example 1

[0058] After ultrasonic cleaning with deionized water, the bare titanium felt was dried. 80 mg of iridium oxide catalyst was accurately weighed and dispersed in a mixed solution of 8 μL naphthol, 10 ml water and 5 mL isopropanol. After ultrasonic dispersion for 30 min, it was sprayed onto the bare titanium felt using an ultrasonic sprayer under heating conditions of 70 °C. After drying, the iridium dioxide dispersed gas transport layer electrode was obtained.

[0059] The samples from Examples 1, 2, and Comparative Example 1 were cut into 20*20mm pieces and used as the anode gas transport layer of a PEM electrolyzer test fixture with an active area of ​​20*20mm for water electrolysis testing. The matching membrane electrode was loaded with a noble metal at 1mg / cm³. 2 For a comparison of the current-voltage polarization curves obtained from the testing of a commercial membrane electrode at 60℃ using an electrolytic cell, please refer to [reference needed]. Figure 1 Observation and testing results showed that the film electrodes prepared in Examples 1 and 2 had a performance of 2 A / cm. 2 The lower electrolysis voltage observed at the above current density indicates that the microporous layer preparation optimizes the mass transfer and conductivity processes under high electrical density conditions, reducing voltage loss caused by problems such as bubble accumulation and poor mass transfer and conductivity.

Claims

1. An electrode with a microporous gas transport layer, characterized in that, It includes a titanium matrix, a microporous layer covering the surface of the titanium matrix, and noble metal compound nanoparticles highly dispersed on the surface of the microporous layer.

2. The method for preparing a gas transport layer electrode with a microporous layer according to claim 1, characterized in that, Includes the following steps: Step 1: Pre-treat the titanium substrate; Step 2: Prepare the slurry for the microporous layer; The microporous layer slurry is composed of the following components by mass percentage: 5%–15% conductive powder, 5%–15% polysulfone, 0.1%–1.05% ionomer, and 120%–150% N-methylpyrrolidone as solvent; Step 3, slurry coating: The microporous layer slurry prepared in step 2 is filtered from one side of the titanium substrate pretreated in step 1 to the other side for coating; the coated titanium substrate is heated and then quickly transferred to deionized water to achieve the reverse inversion, resulting in a gas diffusion layer with microporous layer; the gas diffusion layer with microporous layer is sintered at high temperature under vacuum and then cleaned to remove surface impurities. Step 4, preparation of active layer: a noble metal supported catalyst with catalytic activity is distributed on the surface of the microporous layer of the gas diffusion layer in step 3 to obtain a noble metal dispersed microporous gas transport layer electrode.

3. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The pretreatment involves immersing the titanium substrate in a dilute hydrochloric acid solution for surface treatment, followed by ultrasonic cleaning, and finally rinsing thoroughly with deionized water and drying.

4. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, In step 2, the microporous layer slurry is prepared by weighing ionomer and polysulfone by mass percentage and dissolving them in N-methylpyrrolidone at low speed for 4 hours. Then, conductive powder is added, and the solution is dispersed at high speed for 6 hours. Finally, degassing is performed to prepare a uniformly mixed microporous layer slurry.

5. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The ionic polymer consists of 0.05% to 1% polyvinylpyrrolidone and 0.05% other ionic polymers by mass.

6. The method for preparing an electrode with a microporous gas transport layer according to claim 5, characterized in that, The other ionic polymers include one or a combination of several of the following: polytetrafluoroethylene dispersion, naphthol solution, and perfluorosulfonic acid.

7. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The conductive powder includes one or a combination of several of the following: titanium suboxide, titanium nitride, titanium carbide, titanium powder and its compound powder, tantalum powder and its compound powder; the conductive powder is preferably in the form of nanosheets, and the particle size of the conductive powder is between 0.05 and 5 μm.

8. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The filtration process in step 3 is vacuum filtration, which requires adding low-speed filter paper or 0.22-1μm nylon filter cloth on the side near the negative pressure. The negative pressure is used to make the conductive powder evenly distributed on the surface of the porous titanium matrix through which the gas and liquid flow.

9. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The active layer is composed of compounds of noble metals such as iridium, ruthenium, and platinum, or composite phases of these compounds with other non-noble metal compounds.

10. The method for preparing an electrode with a microporous gas transport layer according to claim 1, characterized in that, The titanium matrix is ​​a porous material formed by bonding and connecting any one or more of the following: powder sintered porous titanium, titanium mesh, and titanium fiber felt.

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