Preparation method of deoxygenized hydrogen composite diffusion layer and composite diffusion layer

Abstract

The invention relates to the technical field of hydrogen production through water electrolysis, in particular to a preparation method of a deoxygenated hydrogen composite diffusion layer and the composite diffusion layer. The components of the coating slurry are blended, brush coating adsorption is carried out on the diffusion layer, and on the basis that the basic functions of the diffusion layer are not affected, construction of a micropore structure of the diffusion layer and a hydrogen elimination layer is achieved. The diffusion layer is used in the field of water electrolysis hydrogen production, and secondary elimination of hydrogen in oxygen can be effectively achieved. The method comprises the following steps: cleaning a titanium substrate, sequentially adding metal oxide powder, a catalyst, titanium nitride powder and an ionomer into a high-alcohol-ratio solvent in a low-temperature water bath, and stirring to form composite slurry; and spraying the composite slurry on a single side of a base material, and carrying out negative pressure and hot pressing treatment to obtain the composite diffusion layer. The hydrogen elimination layer and the microporous layer are synchronously constructed on the diffusion layer by regulating and controlling the components of the slurry, so that secondary elimination of hydrogen in oxygen is realized. Tests show that the content of hydrogen in oxygen of the diffusion layer is reduced by more than 50% compared with an untreated substrate, and the conductivity and the mass transfer efficiency are not affected.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by electrolysis of water, and in particular to a preparation method of a deoxygenated hydrogen composite diffusion layer and the composite diffusion layer. Background Art

[0002] As a crucial piece of equipment for green hydrogen production, the safety of PEM electrolyzers has attracted widespread attention. A key safety metric is the hydrogen-in-oxygen ratio. When the hydrogen-in-oxygen ratio ranges from 4% to 94%, there's a risk of explosion. Therefore, controlling the hydrogen-in-oxygen ratio at the electrolyzer outlet to below 2% is a key development objective. The diffusion layer, a core component of the electrolyzer, performs crucial functions such as gas-liquid transport, mechanical support, electrical conductivity and heat transfer, and two-phase flow management. The porosity, pore structure, corrosion resistance, and electrical conductivity of the diffusion layer are key indicators determining the quality of these functions.

[0003] Existing strategies for reducing hydrogen in oxygen mostly involve constructing a hydrogen removal layer between the proton membrane and the catalytic layer on the anode side of the membrane electrode, or mixing a hydrogen removal catalyst into the anode catalyst to adsorb and oxidize the hydrogen that permeates the anode, and then conduct the generated hydrogen protons back to the cathode through the proton membrane, forming a closed-loop hydrogen removal pathway. For example, a low-hydrogen permeability PEM water electrolysis membrane electrode and its preparation method, published in CN119287410A, can effectively reduce the hydrogen content in oxygen by more than 85%. However, due to the current trend of the proton membrane thin film and the need for differential pressure hydrogen removal, some hydrogen is still not removed in time in the proton membrane hydrogen removal layer.

[0004] In summary, whether constructing a hydrogen removal layer between the proton membrane and the anode catalyst layer or mixing the hydrogen removal catalyst into the anode catalyst to form a closed-loop hydrogen removal pathway, the following defects still exist:

[0005] Incomplete hydrogen removal: Due to the trend toward thinner proton membranes and the need for differential pressure hydrogen removal, hydrogen penetration is accelerated. The proton membrane hydrogen removal layer cannot completely remove the penetrating hydrogen, resulting in the hydrogen concentration in the residual oxygen still being close to 1% (the measured comparative ratio is 0.92%), posing a safety risk.

[0006] Functional limitations: If a hydrogen removal structure is added directly to the surface of the diffusion layer, it will clog the pores or destroy the conductive network, affecting the core functions of the diffusion layer such as gas-liquid transmission, mechanical support, and conductive heat transfer (porosity must be greater than 50%, and resistance must be less than 10mΩ·cm).

[0007] Therefore, how to break through the hydrogen elimination problem from the manufacturing process of the diffusion layer and achieve deep elimination of hydrogen in oxygen while retaining the basic functions of the diffusion layer. Summary of the Invention

[0008] The problem to be solved by the present invention is how to break through the hydrogen elimination problem from the manufacturing process of the diffusion layer and realize the deep elimination of hydrogen in oxygen while retaining the basic function of the diffusion layer.

[0009] In view of the shortcomings of the prior art, the present invention solves the technical problems thereof by adopting a technical solution: a method for preparing a deoxidizing hydrogen composite diffusion layer, comprising the following steps:

[0010] S1: Substrate cleaning: Select titanium mesh, titanium felt or porous titanium substrate, perform surface pre-rinsing, ultrasonic cleaning and alcohol spray cleaning in sequence, and dry for later use;

[0011] S2: Preparation of composite slurry: In a low-temperature water bath at 15-20°C and stirring at 500-800 rpm, add the following to a solvent in sequence: metal oxide powder, catalyst, titanium nitride powder, and ionomer; wherein the solvent comprises at least two of isopropyl alcohol, ethanol, and ultrapure water;

[0012] The metal oxide powder comprises a mixture of aluminum oxide powder, zirconium oxide powder and cerium oxide powder, the mesh size of the metal oxide powder is 400-500 mesh, and the mass of the metal oxide powder accounts for 1‰-4‰ of the mass of the solvent;

[0013] The catalyst comprises at least one of platinum black, iridium black and palladium black and must comprise platinum black, the catalyst mesh number is 500-600 mesh, and the catalyst mass is 1‰-4‰ of the solvent mass;

[0014] The mesh size of titanium nitride powder is 400-500 mesh, accounting for 2‰-5‰ of the solvent mass;

[0015] The ionomer is Nafion perfluorosulfonic acid resin, accounting for 2‰ to 6‰ of the solvent mass;

[0016] After mixing, the mixture is subjected to stirring, ultrasonication and stirring to obtain a composite slurry;

[0017] S3: Composite slurry coating: spray the composite slurry on one side of the substrate, and fix the substrate on the heating plate.

[0018] Heating plate temperature 100-120°C, solid loading 10-50 mg / cm 2 ;

[0019] S4: Negative pressure treatment: treatment at a vacuum degree range of 0.1-0.5 MPa for 10 min;

[0020] S5: Hot pressing treatment: the treatment time is 4 to 8 minutes under the conditions of pressure 2 to 5 MPa and temperature 100 to 180°C.

[0021] Preferably, the solvent is a composite solvent of isopropyl alcohol / ultrapure water or ethanol / ultrapure water or isopropyl alcohol + ethanol / ultrapure water, wherein the volume ratio of alcohol / ultrapure water is ≥4:1.

[0022] Preferably, the mass ratio of aluminum oxide powder, zirconium oxide powder and cerium oxide powder is 1-2:1-3:8-10. Preferably, the mass ratio of platinum black, iridium black and palladium black is (9-10):(0-2):(0-2).

[0023] Preferably, the surface pre-rinsing in S1 uses deionized water or ultrapure water to rinse the substrate for no less than 5 minutes; ultrasonic cleaning is performed using an ultrasonic cleaning machine with ultrapure water as a solvent at a temperature of no more than 80° C. for 30 minutes; and ultrasonic cleaning is repeated two to three times.

[0024] Preferably, the metal oxide powder is added within 1 to 5 minutes after the solvent is added to S2; the catalyst is added after stirring for 5 to 10 minutes; the titanium nitride powder is added after stirring for 5 to 10 minutes; the ionomer is finally added after stirring for 30 minutes.

[0025] A deoxidizing hydrogen composite diffusion layer is prepared by the method according to any one of claims 1 to 6, comprising a diffusion layer, a microporous layer and a hydrogen removal layer.

[0026] The beneficial effects of the present invention are as follows: the diffusion layer produced by the method of the present invention directly constructs the hydrogen removal layer, forms a synergistic relationship with the proton membrane hydrogen removal layer, realizes the secondary elimination of hydrogen on the anode side, and reduces the hydrogen content in oxygen to within 0.5% (reduced by more than 50% compared with the traditional diffusion layer), breaking through the technical problem of incomplete hydrogen removal of the thin film proton membrane; at the same time, the addition of titanium nitride can synchronously construct a microporous layer, optimize the gas-liquid transmission path, improve the mass transfer efficiency and reaction active sites, and enhance the electrical conductivity; the slurry components and process parameter control ensure that the hydrogen removal layer is tightly combined with the diffusion layer substrate (titanium mesh / titanium felt / porous titanium) without affecting the porosity, corrosion resistance and mechanical support function; the negative pressure treatment optimizes the arrangement of the microporous structure, the hot pressing process improves the surface flatness, and the residual solvent is completely removed, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a production flow chart of the composite diffusion layer involved in the present invention;

[0028] Figure 2 A schematic diagram of the microstructure of the composite diffusion layer according to the present invention;

[0029] Figure 3 The following are photos of Example 1 (left) and Comparative Example 1 (right) according to the present invention.

[0030] Explanation of the accompanying figures: 1. Diffusion layer; 2. Microporous layer; 3. Hydrogen removal layer. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described to better illustrate the principles of the invention and its practical application, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for specific applications.

[0032] In order to solve the problems raised in the background technology, the present invention proposes a method for preparing a hydrogen composite diffusion layer in a deoxidation process as follows:

[0033] S1: Substrate cleaning: The diffusion layer substrate can be titanium mesh, titanium felt, porous titanium, or a composite form, with a precious metal coating or untreated surface. Cleaning is a conventional material cleaning step. First, use deionized water or ultrapure water to pre-rinse the substrate surface for no less than 5 minutes. Then, use an ultrasonic cleaner with ultrapure water as the solvent, and ultrasonically clean for 30 minutes at a temperature of 80°C or less. Repeat two to three times. Then, use 100-1000mL of alcohol with a purity of >99.8% to spray the surface. After cleaning, place the substrate in a blast drying oven to dry for use at a drying temperature of 25-40°C.

[0034] S2: Composite slurry preparation: Under stirring conditions in a low-temperature water bath, add metal oxide powder, catalyst, titanium nitride powder, and ionomer to the solvent in sequence. The low-temperature water bath temperature is controlled between 15 and 20°C, the stirring speed is 500 to 800 rpm, the solvent is added within 1 to 5 minutes, the metal oxide powder is slowly added, and after stirring for 5 to 10 minutes, the catalyst is slowly added, and after stirring for 5 to 10 minutes, the titanium nitride powder is added and stirred for 30 minutes, and finally the ionomer is added, as follows:

[0035] Solvents: isopropyl alcohol, ethanol, ultrapure water, or a combination of two or more solvents, wherein the volume ratio of isopropyl alcohol / ultrapure water, ethanol / ultrapure water, or isopropyl alcohol + ethanol / ultrapure water (isopropyl alcohol / ethanol = 1 / 3 to 3 / 1) must be greater than or equal to 4 / 1, and the purity of the isopropyl alcohol and ethanol must be greater than or equal to 99.9%;

[0036] Metal oxide powder: a mixture of aluminum oxide (Al2O3), zirconium oxide (ZrO2), and cerium oxide (CeO2) powders, with a powder mesh size of 400-500 mesh, a mass of 1‰-4‰ of the solvent, and a mass ratio of (1-2): (1-3): (8-10). The function of the metal oxide powder is to provide hydrogen adsorption sites and enhance the stability of the hydrogen removal layer;

[0037] Catalyst: at least one of platinum black (Pt), iridium black (Ir), and palladium black (Pd) or a mixture thereof, wherein platinum black is a required item and accounts for a larger proportion, with a mass ratio of (9-10):(0-2):(0-2), the catalyst mesh size is 500-600 mesh, and the mass is 1‰-4‰ of the solvent;

[0038] Titanium nitride powder: The powder mesh size is 400-500 mesh, and the mass is 2‰-5‰ of the solvent, which constructs a microporous layer and enhances conductivity;

[0039] Ionomer: The ionomer is Nafion perfluorosulfonic acid resin, with a mass of 2‰ to 6‰ of the solvent, providing a proton transport channel and acting as an adhesive;

[0040] After mixing, stir for 30 minutes, ultrasonicate for 30 minutes, and stir for 30 minutes. The stirring environment is low-temperature water bath stirring, the temperature is 15-20°C, the ultrasonic temperature is 15-20°C, and the ultrasonic power is 40-50kHz. The preparation of the composite slurry is now completed.

[0041] S3: Composite slurry coating: The prepared composite slurry is evenly coated on one side of the treated substrate using a pneumatic spray gun. The substrate is fixed on a heating plate with a temperature of 100-120°C. The solid loading is 10-50 mg / cm 2 , the solid loading was calculated by weighing the mass difference before and after the diffusion layer.

[0042] S4: Negative pressure treatment: Use a vacuum circulation pump to perform negative pressure treatment on the coated diffusion layer in order to optimize the surface spatial arrangement of the microporous layer and the hydrogen removal layer. The vacuum degree range is 0.1-0.5 MPa and the treatment time is 10 min.

[0043] S5: Hot Pressing: Use a hot press to perform hot pressing at a pressure of 2-5 MPa, a temperature of 100-180°C, and a duration of 4-8 minutes. This step aims to improve the surface smoothness of the microporous layer and evaporate any residual solvent. This completes the preparation of the deoxidized hydrogen composite diffusion layer material.

[0044] like Figure 2 Figure 2 shows the microstructure of a composite diffusion layer fabricated using the method of the present invention, comprising a diffusion layer 1, a microporous layer 2, and a hydrogen removal layer 3. The microporous layer 2 and hydrogen removal layer 3 are uniformly mixed and firmly bonded to the surface of the diffusion layer 1 via an ionomer, achieving both microporous transmission channels and hydrogen removal and electrical conductivity, while also ensuring strong coating adhesion and improving contact with the membrane electrode.

[0045] The following is Example 1, which further illustrates the preparation method of the present invention:

[0046] Substrate cleaning: A 50*50mm, 0.4mm thick platinum-coated titanium felt with a platinum layer thickness of 200nm and a porosity of 60% was selected. The substrate was pre-rinsed with deionized water for 5 minutes. Then, an ultrasonic cleaner was used with ultrapure water as the solvent at 60°C for 30 minutes. This was repeated three times. 250mL of 99.8% pure alcohol was then used for surface spraying. After cleaning, the substrate was placed in a blast drying oven for drying at 30°C.

[0047] Composite slurry preparation: In a 100mL beaker, in a 15°C water bath, stirring at 600 rpm, add 50mL of 99.9% pure isopropyl alcohol, 12.5mL of 99.9% pure ethanol, and 12.5mL of ultrapure water, totaling approximately 62g. After stirring for 2 minutes, add 84mg of metal oxide powder ground to 500 mesh. The weights of aluminum oxide (Al2O3), zirconium oxide (ZrO2), and cerium oxide (CeO2) are 14mg, 14mg, and 56mg, respectively. After stirring for 10 minutes, slowly add 90mg of 600 mesh catalyst. The weights of platinum black (Pt), iridium black (Ir), and palladium black (Pd), respectively, are 75mg, 7.5mg, and 7.5mg, respectively. After stirring for 10 minutes, add 170mg of 500 mesh titanium nitride powder. Stir for 30 minutes, and finally, add 200mg of Nafion ionomer. After mixing, the mixture was stirred for 30 minutes, ultrasonicated for 30 minutes, and stirred for 30 minutes. The stirring environment was low-temperature water bath stirring at a temperature of 15°C, an ultrasonic temperature of 15°C, and an ultrasonic power of 50 kHz. Thus, the slurry preparation was completed.

[0048] Composite slurry coating: The prepared slurry is evenly coated on one side of the treated titanium felt through a pneumatic spray gun. The substrate is fixed on a heating plate, and the heating plate temperature is controlled at 120°C. The solid loading is 21.76 mg / cm 2 .

[0049] Negative pressure treatment: Use a vacuum circulation pump to perform negative pressure treatment on the coated diffusion layer, with a vacuum degree of 0.1 MPa and a treatment time of 10 minutes.

[0050] Hot pressing treatment: Use hot pressing machine to perform hot pressing treatment, pressure 3.5MPa, temperature 140℃, time 6min. So far, the preparation of a deoxidizing hydrogen composite diffusion layer has been completed. Figure 3 Left.

[0051] The following is Example 2: Compared with Example 1, the difference in Example 2 is that the masses of platinum black, iridium black, and palladium black are 80 mg, 0 mg, and 7.5 mg, respectively, and the remaining steps are the same as in Example 1.

[0052] Compared with Example 1, Example 3 is different in that the mass of titanium nitride is 180 mg, the mass of cerium oxide is 46 mg, and the remaining steps are the same as Example 1.

[0053] Comparative Example 1: Compared with Example 1, Example 2, and Example 3, the comparative titanium felt is not treated in any way. The characteristics are 50*50mm, 0.4mm thick platinum-plated titanium felt, the platinum layer thickness is 200nm, the porosity is 60%, and the actual object is shown in FIG. Figure 3 right.

[0054] To characterize the material properties, the diffusion layer prepared by the present invention was placed in a PEM electrolyzer fixture for electrochemical performance and hydrogen content in oxygen testing. The anode diffusion layer materials were those of Example 1, Example 2, and Example 3, respectively. For Comparative Example 1, an 80 μm proton membrane with a hydrogen removal layer was selected, and the platinum loading of the hydrogen removal layer was 0.2 mg / cm 2 The anode catalyst is IrO2, with an Ir loading of 1 mg / cm 2 The cathode catalyst is Pt / C, with a Pt loading of 0.4 mg / cm 2 The cathode diffusion layer was made of carbon paper. The operating temperature was 60°C, the differential pressure was 3 MPa, the cathode side was high pressure, and the water flow rate was 60 mL / min. The results are shown in Table 1:

[0055] Table 1

[0056] Group <![CDATA[Hydrogen content in oxygen % (0.1 A / cm 2 )]]> Chamber voltage V Example 1 0.38 1.512 Example 2 0.31 1.517 Example 3 0.45 1.509 Comparative Example 1 0.92 1.522

[0057] According to the test results, the composite diffusion layer samples of Examples 1, 2, and 3 prepared by this method have a low current density of 0.1 A / cm 2 Compared with the untreated diffusion layer, the concentration of hydrogen in oxygen can be controlled within 0.5%, and the reduction rate of the hydrogen in oxygen parameter is greater than 50%, which provides a guarantee for the safe operation of the PEM electrolyzer.

[0058] The present invention addresses the potential safety hazard of incomplete hydrogen removal from oxygen in PEM electrolyzers and innovatively proposes a solution to composite hydrogen removal function on the diffusion layer substrate. By precisely controlling the slurry formula containing metal oxide powder, platinum catalyst, titanium nitride and ionomer, combined with single-side coating, negative pressure and hot pressing processes, a composite layer with both hydrogen removal and microporous structure is constructed while retaining the core functions of gas-liquid transmission, electrical conduction and heat transfer of the diffusion layer. The examples confirm that the diffusion layer prepared by this method controls the hydrogen content in oxygen to 0.31%-0.45% (0.1A / cm 2), with a voltage stable at 1.509-1.517V, significantly superior to the untreated substrate (0.92% hydrogen in oxygen, voltage 1.522V). By combining a hydrogen removal layer with a diffusion layer, the present invention achieves secondary hydrogen removal on the anode side without affecting the basic function of the diffusion layer, thereby improving electrolyzer safety. Simultaneously, by adjusting the slurry ratio and adding titanium nitride components, a single-sided microporous layer is constructed while constructing the hydrogen removal layer, improving mass transfer and electrical conductivity, and increasing reactive sites.

Claims

1. A method for preparing a hydrogen composite diffusion layer for deoxidation, characterized in that: The following steps are involved: S1: Substrate cleaning: Select titanium mesh, titanium felt or porous titanium substrate, perform surface pre-rinsing, ultrasonic cleaning and alcohol spray cleaning in sequence, and dry for later use; S2: Preparation of composite slurry: In a low-temperature water bath at 15-20°C and stirring at 500-800 rpm, add the following into the solvent in sequence: metal oxide powder, catalyst, titanium nitride powder, and ionomer; wherein the solvent comprises at least two of isopropyl alcohol, ethanol, and ultrapure water; The metal oxide powder comprises a mixture of aluminum oxide powder, zirconium oxide powder and cerium oxide powder, the mesh size of the metal oxide powder is 400-500 mesh, and the mass of the metal oxide powder accounts for 1‰-4‰ of the mass of the solvent; The catalyst comprises at least one of platinum black, iridium black and palladium black and must comprise platinum black, the catalyst mesh number is 500-600 mesh, and the catalyst mass is 1‰-4‰ of the solvent mass; The mesh size of titanium nitride powder is 400-500 mesh, accounting for 2‰-5‰ of the solvent mass; The ionomer is Nafion perfluorosulfonic acid resin, accounting for 2‰ to 6‰ of the solvent mass; After mixing, the mixture is subjected to stirring, ultrasonication and stirring to obtain a composite slurry; S3: Composite slurry coating: Spray the composite slurry on one side of the substrate, fix the substrate on a heating plate at a temperature of 100-120°C, and a solid loading of 10-50 mg / cm 2 ; S4: Negative pressure treatment: treatment at a vacuum degree range of 0.1-0.5 MPa for 10 min; S5: Hot pressing treatment: the treatment time is 4 to 8 minutes under the conditions of pressure 2 to 5 MPa and temperature 100 to 180°C.

2. The method for preparing a deoxidizing hydrogen composite diffusion layer according to claim 1, characterized in that: The solvent is a composite solvent of isopropyl alcohol / ultrapure water or ethanol / ultrapure water or isopropyl alcohol+ethanol / ultrapure water, wherein the volume ratio of alcohol / ultrapure water is ≥4:

1.

3. The method for preparing a deoxidizing hydrogen composite diffusion layer according to claim 1, characterized in that: The mass ratio of the aluminum oxide powder, the zirconium oxide powder and the cerium oxide powder is 1-2:1-3:8-10.

4. The method for preparing a deoxidizing hydrogen composite diffusion layer according to claim 2 or 3, characterized in that: The mass ratio of platinum black, iridium black and palladium black is (9-10):(0-2):(0-2).

5. The method for preparing a deoxidizing hydrogen composite diffusion layer according to claim 1, characterized in that: In S1, the surface is pre-rinsed with deionized water or ultrapure water for no less than 5 minutes. Ultrasonic cleaning is performed in an ultrasonic cleaning machine with ultrapure water as a solvent at a temperature of no more than 80° C. for 30 minutes. The ultrasonic cleaning is repeated two to three times.

6. The method for preparing a deoxidizing hydrogen composite diffusion layer according to claim 4, characterized in that: Add the metal oxide powder within 1 to 5 minutes after adding the solvent to S2; add the catalyst after stirring for 5 to 10 minutes; add the titanium nitride powder after stirring for 5 to 10 minutes; finally add the ionomer after stirring for 30 minutes.

7. A deoxidizing hydrogen composite diffusion layer, characterized by: The invention is prepared by the method according to any one of claims 1 to 6, and comprises a diffusion layer (1), a microporous layer (2) and a hydrogen removal layer (3).

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