A high-stability integrated oxygen evolution catalyst for an anion exchange membrane electrolyzer and a preparation method and application thereof

Abstract

This invention relates to the field of electrocatalyst technology, specifically to a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, its preparation method, and its application. To address the problems of high OER overpotential, easy catalyst layer detachment at ampere-level current densities, and complex preparation methods in current anion exchange membrane electrolyzers, which hinder large-scale production, this invention employs the following method: 1) Add ferric nitrate to isopropanol and dissolve it under vigorous stirring to obtain solution A; add thiourea to deionized water and dissolve it to obtain solution B; add solution B to solution A under vigorous stirring to obtain a homogeneous solution C; 2) Immerse a porous metal substrate, which has been ultrasonically cleaned with ethanol and hydrochloric acid solution, in solution C, then remove it, rinse it thoroughly with a large amount of deionized water, and dry it to obtain the integrated oxygen evolution catalyst. The oxygen evolution catalyst prepared by this invention not only has high oxygen evolution catalytic activity but also bonds tightly to the substrate, enabling long-term stable operation at ampere-level current densities.

Description

Technical Field

[0001] This invention relates to the fields of functional materials and electrocatalysts, specifically to a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, its preparation method, and its application. Background Technology

[0002] Compared to alkaline water electrolysis (ALK) and proton exchange membrane water electrolysis (PEMWE) technologies, anion exchange membrane water electrolysis (AEMWE) technology combines the low cost of ALK with the high current density, low electrolyte corrosion, and rapid response of PEMWE. Furthermore, like ALK, AEMWE can utilize non-precious metal-based catalysts, making it one of the ideal technological routes for low-cost, large-scale production of "green hydrogen." However, the slow kinetics of the four-electron transfer anodic oxygen evolution reaction (OER) lead to high overpotentials, resulting in excessively high energy consumption for hydrogen production, necessitating high-performance catalysts to reduce the reaction overpotential. In addition, the impact of numerous bubbles on the catalyst layer at ampere-level current densities, causing it to detach from the substrate, is also a challenge for industrial applications.

[0003] Traditional oxygen evolution electrodes in electrolyzers are formed by bonding powdered catalysts to a substrate. This method has several drawbacks: it requires expensive binders, and the catalyst is prone to detachment and deactivation at ampere-level current densities. Integrated catalysts, prepared using conventional hydrothermal or electrodeposition methods, eliminate the need for binders; however, the bonding between most catalysts and the substrate remains insufficient, and significant catalyst detachment occurs under ampere-level current densities due to bubble erosion. Besides significantly reducing activity, substantial powder detachment can even clog tightly packed electrolyzer components, causing severe equipment damage.

[0004] Nickel foam and nickel felt are among the most commonly used substrates for alkaline water electrolysis. However, pure substrates have poor activity, making it difficult to meet the requirements of low-energy hydrogen production. Attaching a highly active catalyst layer to the substrate surface has become a major means of improving activity.

[0005] For example, in patent 202410927247.1, a highly active alkaline water electrolysis oxygen evolution reaction catalyst based on transition metals, its preparation method, and its application are disclosed, belonging to the fields of new energy technology and electrocatalytic materials. This invention primarily uses electrodeposition combined with high-temperature annealing to load cerium dioxide nanoparticles with vacancies onto a nickel foam substrate, and then uses high-temperature hydrothermal loading to load two-dimensional nickel-iron nanosheets onto the substrate. The entire catalyst preparation process is complex; scale-up preparation requires not only expensive electrodeposition equipment but also significant energy consumption for high-temperature annealing and hydrothermal processes. The high-temperature, high-pressure hydrothermal reaction itself greatly limits the large-scale preparation of this process. More importantly, the adhesion between the hydrothermally loaded catalyst layer and the substrate is limited, potentially making it difficult to withstand prolonged scouring by bubbles at ampere-level current densities. Therefore, similar methods are not only energy-intensive and difficult to scale up, but their stability under high current conditions also needs verification.

[0006] Patent No. 202410063229.3 discloses an oxygen evolution electrode loaded with nickel-iron layered double hydroxides and its preparation method. The preparation method of the oxygen evolution electrode loaded with nickel-iron layered double hydroxides includes the following steps: (1) placing a foamed nickel-iron substrate material in an acid solution for acid etching, followed by water washing to obtain an etched foamed nickel-iron substrate material; (2) placing the etched foamed nickel-iron substrate material in a solution containing Ni 2+ Fe 2+ The reaction is carried out in an aqueous solution of an alkaline buffer, followed by washing and drying to obtain an oxygen evolution electrode loaded with nickel-iron layered double hydroxides. This published patent requires etching with a strong acid, followed by the addition of nickel and iron sources for catalyst layer growth. The use of strong acid poses certain risks, and the need to introduce a nickel source and heat to 40-50°C for the reaction increases production costs. More importantly, the catalyst layer growth and substrate etching are performed in two steps, which reduces the adhesion between the catalyst and the substrate. This patent also lacks an ampere-level current density (≥1000 mA cm⁻¹). -2 Long-term stability testing.

[0007] Developing a low-cost, highly active, and tightly bonded catalyst layer to the substrate that can operate at ampere-level current densities for extended periods and is prepared using a simple process remains a challenge. Summary of the Invention

[0008] In view of this, in order to solve the problems of high OER overpotential, easy catalytic layer detachment under ampere-level current density, and complex preparation methods in current anion exchange membrane electrolyzers, which make large-scale preparation difficult, a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers is provided, along with its preparation method and application.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, comprising the following steps: 1) Add ferric nitrate to isopropanol and stir vigorously to dissolve to obtain solution A; add thiourea to deionized water to dissolve to obtain solution B; add solution B to solution A under vigorous stirring to obtain homogeneous solution C; 2) The porous metal substrate, which has been ultrasonically cleaned with ethanol and hydrochloric acid solution, is immersed in solution C, then taken out and rinsed with a large amount of deionized water, and then dried to obtain an integrated oxygen evolution catalyst.

[0010] In step 1) above, solution A contains 1-15g of ferric nitrate and 20-100mL of isopropanol. The ferric nitrate and isopropanol are added in a ratio of 13.5 cm². 2 calculate.

[0011] In step 1) above, solution B contains 10-100 mg of thiourea and 10-50 mL of deionized water, with the thiourea and deionized water arranged in a ratio of 13.5 cm². 2 calculate.

[0012] In step 2) above, the immersion temperature is 15 ~ 35℃ at room temperature, and the immersion time is 12 ~ 36 hours.

[0013] The porous metal substrate in step 2) above includes nickel foam, nickel mesh, nickel felt, cobalt foam, cobalt mesh, cobalt felt, or iron foam.

[0014] The integrated oxygen evolution catalyst prepared by the above method.

[0015] The integrated oxygen evolution catalyst prepared by the above method is used in anion exchange membrane electrolyzers, alkaline electrolyzer anodes, and alkaline oxygen evolution catalytic reactions.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The main raw material for preparing the integrated catalyst in this invention is Fe-containing... 3+ Iron salts and thiourea, utilizing Fe 3+ Slow etching of a porous metal substrate, along with the addition of thiourea and the low-valence Ni, Co, and Fe generated during etching, produces nanosheet catalysts in situ at the etched site. The Fe added in this invention... 3+Not only does it act as an etchant, but it can also serve as a dopant element for the subsequent generation of catalysts. On the one hand, it avoids the use of dangerous reagents such as strong acids and bases for substrate etching. On the other hand, Fe doping can greatly promote the reconstruction of the catalyst in the OER reaction to generate highly active species. In addition, corrosion and growth occur almost simultaneously, which makes the in-situ generated catalyst layer very tightly bonded to the substrate, and it can still maintain good performance under bubble impact at ampere-level current densities.

[0017] 2. The method of this invention only requires simple room temperature impregnation, eliminating the need for complex steps such as heating, pressurization, and annealing. It consumes almost no energy and has a certain degree of versatility, allowing for substrate replacement and large-scale preparation according to different needs, thus demonstrating promising application prospects. For example, the preparation method of this invention can scale up the catalyst to 400 cm⁻¹. 2 The above points are true, and the performance can be kept consistent across different batches.

[0018] 3. The catalyst prepared in Example 1 of this invention requires only 221 and 265 mV overpotentials to achieve 10 and 100 mA / cm² in the oxygen evolution reaction at 1.0 MKOH. 2 Current density, at 2.0 A / cm 2 It has achieved continuous and stable operation for over 1100 hours at ampere-level current densities, exhibiting low overpotential and good stability at high current densities; in anion exchange membrane electrolyzers, it can achieve 1.0 and 2.0 A / cm at 1.70 and 1.85 V, respectively. 2 It achieves industrial-grade current density and can operate stably for 1000 hours; the performance of both the half-cell and electrolyzer devices exceeds that of current commercial RuO2 catalysts. The catalyst prepared by combining slow substrate corrosion with in-situ catalyst layer formation is tightly bonded to the substrate, which is expected to solve the problem of catalyst layer detachment and deactivation at ampere-level current densities. This technology is expected to further promote the development of AEMWE hydrogen production technology. Attached Figure Description

[0019] Figure 1 SEM images of the catalysts in Examples 1, 2, and 3 (using pure nickel foam substrate) and Comparative Example 1, and TEM-mapping image of Example 1. Figure 2 The LSV polarization curves and overpotential comparison diagrams at different current densities of Examples 1, 2, 3, Comparative Example 1, nickel foam substrate, and commercial RuO2 catalyst in 1.0 M KOH solution are shown. Figure 3 This is a graph showing the Et test results of Example 1 in 1M KOH solution; Figure 4 This is a comparison graph showing the Vi curves and voltages required to achieve different current densities for Example 1 and a commercial RuO2 catalyst in an AEM electrolyzer device. Figure 5 Figure 1 shows the long-term Vt durability test results of Example 1 and the commercial RuO2 catalyst in the AEM electrolyzer device. Figure 6 LSV polarization curves of the catalysts in Examples 4, 5, 6 and 7 in 1.0 M KOH solution; Figure 7 This is a comparison graph of the overpotentials of the catalysts in Examples 4, 5, 6, and 7 at different current densities; Figure 8 LSV polarization curves of nickel felt substrate and catalyst of Example 8 in 1.0 M KOH solution; Figure 9 This is a graph showing the Et test results in 1M KOH solution for Example 8; Figure 10 LSV polarization curves of cobalt foam substrate and catalyst of Example 9 in 1.0 M KOH solution; Figure 11 LSV polarization curves of foamed iron substrate and catalyst of Example 10 in 1.0 M KOH solution; Figure 12 The images show a physical picture of the catalyst in Example 11 and LSV polarization curves of three batches of catalyst in 1.0 M KOH solution. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0021] Example 1: A method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, comprising the following specific steps: (1) Add 3.5 g of ferric nitrate to 50 mL of isopropanol and stir vigorously to dissolve to obtain solution A; add 40 mg of thiourea to 20 mL of deionized water to dissolve to obtain solution B; pour solution B into solution A under vigorous stirring to obtain a homogeneous solution C; (2) The foamed nickel substrate, which has been ultrasonically cleaned with ethanol and hydrochloric acid solution, is immersed in solution C for 24 hours. After rinsing with a large amount of deionized water, it is then dried to prepare an integrated oxygen evolution catalyst.

[0022] Examples 2-3: To investigate the effect of impregnation time on the oxygen evolution performance of the catalyst, the immersion corrosion time in Examples 2 and 3 was adjusted to 12 and 36 hours, respectively, while the other conditions were the same as those in Example 1. Comparative Example 1: To investigate the high valence state Fe 3+ The effect of ions on the oxygen evolution performance of the catalyst was investigated. In Comparative Example 1, no ferric nitrate was added to solution A, and the immersion corrosion time was 24 hours. The other conditions were the same as those in Example 1. A comparison of the SEM images of the catalyst and the pure nickel foam substrate in Example 1 shows that ( Figure 1 (ac) In Example 1, obvious corrosion was observed along the grain boundaries of the substrate, and a thin nanosheet catalyst layer was formed in situ on the surface. The catalyst layer, which was corroded and grown in situ, was very tightly bonded to the substrate, which was very beneficial for maintaining the mechanical stability of the catalyst layer under high current density. The nanosheet catalyst was also beneficial for the exposure of catalytic active sites and the transport of electrolyte and bubbles. Figure 1 The TEM-mapping image of gk clearly shows that various elements are uniformly dispersed in the catalyst, which once again successfully proves that the catalyst of Example 1 was successfully synthesized. Figure 1 d and e are SEM images of Example 2 and Example 3, respectively. It can be seen that the substrate has been corroded to different degrees and a thin catalytic layer has been formed on the surface, proving that Example 2 and Example 3 were successfully prepared. Figure 1 f is the SEM image of Comparative Example 1, which shows that no Fe was added. 3+ It does not cause corrosion of the substrate or in-situ formation of a catalyst layer, indicating that Fe 3+ The addition of [a specific substance] is one of the key factors in catalyst formation; LSV curves were tested in 1.0 M KOH solution using a nickel foam substrate, commercial RuO2, and catalysts from Examples 1, 2, 3, and Comparative Example 1. (See attached diagram). Figure 2 a; The catalyst prepared in Example 1 requires only 221 mV overpotential to reach 10 mA / cm. 2 The current density is superior to that of Comparative Example 1 and the nickel foam substrate, and also superior to the 247 mV of the commercial RuO2 catalyst. Figure 2 b) Compared with Comparative Example 1, it shows that Fe 3+ The addition of the corroded substrate and the in-situ generation of a nano-catalyst layer are the main sources of its high catalytic activity; Example 1: The catalyst was subjected to a high current density of 2000 mA / cm². 2 Stability tests were conducted, and the catalyst in Example 1 was able to operate stably continuously for over 1000 hours (see below). Figure 3 This indicates that the catalyst, which undergoes slow substrate corrosion and in-situ catalytic layer formation, not only exhibits good activity but also demonstrates excellent long-term stability under high current. The above three-electrode results show that the catalyst prepared in Example 1 of this invention has high catalytic activity and long-term stability in the alkaline oxygen evolution reaction. In order to further verify the performance of the catalyst in the AEM electrolyzer, it was subsequently assembled with commercial Pt / C into an AEM electrolyzer device. Figure 4 The results showed that Example 1 achieved 1.0 A / cm² in an AEM electrolytic cell at 60°C with only 1.70 V. 2 The current density is significantly better than 1.91 V of commercial RuO2 catalyst, which further proves that the catalyst prepared in Example 1 of this invention still has excellent catalytic performance under actual working conditions; Figure 5 Further verification shows that Example 1 also has good long-term durability under actual working conditions, and can also operate stably for 1000 hours under the device, which is far superior to commercial RuO2 catalysts, showing good application prospects. The integrated electrode derived from the homogeneous slow corrosion of the nickel foam substrate prepared in this embodiment exhibits good catalytic activity and excellent long-term durability for OER in alkaline three-electrode and AEM electrolyzer devices. Its activity and durability are superior to those of current commercial RuO2 catalysts. This invention is expected to prepare an AEM water electrolysis anode oxygen evolution catalyst with lower cost and better overall performance, especially with long-term stable operation at ampere-level current densities.

[0023] Example 4: A method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, the specific steps of which are as follows: (1) 1.5 g of ferric nitrate was added to 50 mL of isopropanol and stirred vigorously to dissolve to obtain solution A; 40 mg of thiourea was added to 20 mL of deionized water to dissolve to obtain solution B; solution B was poured into solution A under vigorous stirring to obtain a homogeneous solution C; (2) After ultrasonic cleaning with ethanol and hydrochloric acid solution, the foam nickel substrate is immersed in solution C for 24 hours, then rinsed with a large amount of deionized water and then dried.

[0024] Examples 5-7: To investigate the effect of ferric nitrate content on the oxygen evolution performance of the catalyst, the ferric nitrate content added to solution A in Examples 5, 6 and 7 was 2.5 g, 4.5 g and 5.5 g, respectively, and the other conditions were the same as those in Example 4. From the above embodiments, it can be seen that Fe 3+ The addition of iron ions is one of the important factors in the preparation of catalysts and their ability to exhibit high-performance oxygen evolution characteristics. Therefore, a series of catalysts with different iron ion contents in solution A were further prepared to clarify the role of Fe... 3+ The trend of performance impact; LSV curves were tested by placing the catalysts of Examples 4-7 in 1.0 M KOH solution, see [reference]. Figure 6 Examples 4-7 show that adding ferric nitrate in the range of 1.5 g to 5.5 g can prepare oxygen evolution catalysts with performance superior to currently available commercial RuO2 catalysts. Figure 7 This indicates that, within certain conditions, changing the preparation conditions can also produce high-performance oxygen evolution catalysts, while further clarifying the Fe...3+ Its key role.

[0025] Example 8: A method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, the specific steps of which are as follows: (1) Add 3.5 g of ferric nitrate to 50 mL of isopropanol and stir vigorously to dissolve to obtain solution A; add 40 mg of thiourea to 20 mL of deionized water to dissolve to obtain solution B; pour solution B into solution A under vigorous stirring to obtain a homogeneous solution C; (2) After ultrasonic cleaning with ethanol and hydrochloric acid solution, the nickel felt substrate is immersed in solution C for 24 hours, then rinsed with plenty of deionized water and dried.

[0026] Examples 9-10: To verify that the method of the present invention can be extended to different substrates, the substrates in Examples 9 and 10 are cobalt foam and iron foam, and the other conditions are the same as the preparation conditions in Example 3; This embodiment extends the use of nickel foam substrates; the self-supporting oxygen evolution electrode prepared by the method of this invention is also applicable to substrates such as nickel felt, cobalt foam, and iron foam. The catalysts of Examples 8, 9, and 10 were placed in 1.0 M KOH solution to test their LSV curves; see [link to relevant documentation]. Figure 8-11 ;from Figure 8 , Figure 10 and Figure 11 It is evident that the alkaline oxygen evolution catalytic performance is significantly improved compared to the pure substrate after treatment with the method of this invention, demonstrating the good scalability of the method and its ability to be prepared according to different requirements. Simultaneously, the catalyst prepared on the nickel felt substrate also exhibits excellent stability at industrial-grade current densities. Figure 9 Under certain conditions, the method of this invention can be used to prepare oxygen evolution catalysts with excellent performance by treating different substrates, indicating that the method of this invention has a certain degree of universality and the substrate can be replaced according to different usage conditions.

[0027] In the above embodiments, ferric nitrate, isopropanol, thiourea, and deionized water were used in a single-piece area of ​​13.5 cm². 2 Calculations show that the preparation method of the present invention can also be scaled up to the same proportion of raw materials.

[0028] Example 11: A method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, the specific steps of which are as follows: (1) 103.7 g of ferric nitrate was added to 1481 mL of isopropanol and stirred vigorously to dissolve to obtain solution A; 1185 mg of thiourea was added to 593 mL of deionized water and dissolved to obtain solution B; solution B was poured into solution A under vigorous stirring to obtain a homogeneous solution C; (2) The 400 cm section after ultrasonic cleaning with ethanol and hydrochloric acid solution 2 Immerse the nickel foam substrate in solution C for 24 hours, then rinse it thoroughly with plenty of deionized water and dry it.

[0029] Besides performance limitations on catalyst applications, scalable production, cost-effectiveness, and batch-to-batch consistency are also significant challenges. Therefore, the catalyst prepared by the method of this invention was scaled up to 400 cm⁻¹. 2 Thanks to a simple preparation method that only requires impregnation at room temperature and the ability to successfully scale up the catalyst to 400 cm⁻¹ without the need for expensive reagents. 2 ,See Figure 12 a; The LSV curves of three different batches of catalyst from Example 11 were tested in 1.0 M KOH solution, see [reference]. Figure 12 b, from which we can see that 400 cm is performed. 2 The performance of the three batches prepared on scale was almost identical, demonstrating good consistency. Example 4 shows that, under certain conditions, the integrated oxygen evolution electrode area can be scaled up to 400 cm² using the method of this invention. 2 Furthermore, the method of this invention has good consistency between different batches. The oxygen evolution electrode can be prepared by impregnation at room temperature without consuming any additional energy, which is highly economical and simple. At the same time, it also has the conditions for large-scale preparation.

[0030] The above-described embodiments 1 and 11 are the best embodiments.

[0031] The above embodiments are only the preferred embodiments of the present invention and do not limit any modifications to the present invention. Any modifications, changes and optimizations made according to the embodiments of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzers, characterized in that, The steps are as follows: 1) Add ferric nitrate to isopropanol and stir vigorously to dissolve to obtain solution A; add thiourea to deionized water to dissolve to obtain solution B; add solution B to solution A under vigorous stirring to obtain homogeneous solution C; 2) The porous metal substrate, which has been ultrasonically cleaned with ethanol and hydrochloric acid solution, is immersed in solution C, then taken out and rinsed with a large amount of deionized water, and then dried to obtain an integrated oxygen evolution catalyst.

2. The method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzer according to claim 1, characterized in that, In step 1), solution A contains 1-15 g of ferric nitrate and 20-100 mL of isopropanol. The ferric nitrate and isopropanol are mixed in a ratio of 13.5 cm². 2 calculate.

3. The method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzer according to claim 1, characterized in that, In step 1), solution B contains 10-100 mg of thiourea and 10-50 mL of deionized water, with the thiourea and deionized water arranged in a ratio of 13.5 cm². 2 calculate.

4. The method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzer according to claim 1, characterized in that, In step 2), the immersion temperature is 15-35°C at room temperature, and the immersion time is 12-36 hours.

5. The method for preparing a highly stable integrated oxygen evolution catalyst for anion exchange membrane electrolyzer according to claim 1, characterized in that, The porous metal substrate in step 2) includes nickel foam, nickel mesh, nickel felt, cobalt foam, cobalt mesh, cobalt felt, or iron foam.

6. The integrated oxygen evolution catalyst prepared by the method according to claim 1.

7. The application of the integrated oxygen evolution catalyst prepared by the method according to claim 1 in anion exchange membrane electrolyzers, alkaline electrolyzer anodes, and alkaline oxygen evolution catalytic reactions.

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