High-performance double-layer heterojunction water electrolysis oxygen evolution catalyst and preparation method and application thereof

Abstract

The application provides a preparation method of a high-performance double-layer heterojunction water electrolysis oxygen evolution catalyst, and comprises the following steps: plating a NiFe or NiFeM plating layer on the surface of a foam metal, wherein M is one or more of Cu, Cr and Zn; and plating a NiFeCo plating layer on the surface of the NiFe or NiFeM plating layer, so as to obtain a high-performance water electrolysis oxygen evolution catalyst with a double-layer heterojunction. The application also provides the catalyst prepared by the method and the application of the catalyst in the field of water electrolysis. The double-layer heterojunction oxygen absorption catalyst prepared by the method has low overpotential, good water electrolysis oxygen evolution performance and low cost, and can also improve the stability of the electrode. The method has the advantages of simplicity, high efficiency, low cost, low environmental requirement, easy expansion and the like.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis, specifically relating to a high-performance bilayer heterojunction oxygen evolution catalyst for water electrolysis, its preparation method, and its application. Background Technology

[0002] Hydrogen energy has garnered widespread attention due to its cleanliness, renewability, and high energy density per unit mass, and is considered a potential next-generation energy source for the 21st century, with the potential to replace traditional chemical energy sources. Water electrolysis is the most ideal green hydrogen production technology, consisting of two parts: cathode hydrogen evolution (HER in alkaline solution) and anodic oxygen evolution (OER in alkaline solution). Compared to the two-electron transfer in HER, OER requires four electrons, making it kinetically much more difficult than the hydrogen evolution reaction. Under ideal conditions (25°C, one atmosphere), the voltage required for HER should be 0V, while the voltage required for OER is 1.23V; therefore, the ideal driving voltage for water electrolysis is 1.23V. However, in practice, due to complex factors, the required voltage is often greater than 1.23V, and this additional applied potential is called the overpotential. Overpotential becomes an important parameter for evaluating catalyst performance. Generally, the lower the overpotential, the lower the energy consumption and the better the catalytic activity of the catalyst.

[0003] Currently, most commercially available oxygen evolution catalysts are precious metal catalysts, such as ruthenium-based and iridium-based catalysts. These catalysts have excellent performance, but they are expensive. When exposed to high currents in industrial applications for extended periods, they may detach and shed residue, resulting in poor long-term stability. This hinders the large-scale application of water electrolysis for hydrogen production. Therefore, there is an urgent need to develop a non-precious metal OER catalyst that is inexpensive, has excellent catalytic activity, and exhibits superior long-term stability.

[0004] Among the many oxygen evolution catalysts for water electrolysis synthesized via hydrothermal methods, although the catalysts have excellent performance, they usually suffer from problems such as long cycle time, high energy consumption, complex steps, easy catalyst detachment, and difficulty in scale-up in production. Electrodeposition, as a simple and efficient electrochemical method, has advantages such as simple process, mild conditions, short reaction time, good reproducibility, safe operation, high yield, and easy scale-up, making it suitable for large-scale production. However, many oxygen evolution catalysts for water electrolysis synthesized by conventional electrodeposition also face problems such as limited performance improvement, low catalyst loading, and limited catalyst stability after industrial production.

[0005] Chinese invention patent CN 113832478 A discloses a hydrothermal synthesis method for NiCo2S4@CoFeMo-LDH electrolytic oxygen evolution catalyst. This catalyst exhibits excellent performance; however, the hydrothermal method typically suffers from problems such as long cycle time, high energy consumption, complex steps, insufficient catalyst stability, easy detachment, and difficulty in scale-up production. Chinese invention patent CN114293201 A discloses a one-step electrodeposition synthesis method for nickel-iron oxygen evolution catalyst for electrolytic hydrogen production via water electrolysis. This catalyst has a short preparation cycle and simple process; however, it suffers from low catalyst loading, high internal resistance, poor performance, and high voltage loss, potentially leading to a limited catalyst lifespan after industrial production. Summary of the Invention

[0006] To address the above problems, this invention provides a high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst, its preparation method, and its application.

[0007] This invention proposes the following solution:

[0008] A method for preparing a high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst includes:

[0009] S1. Dissolve soluble nickel salt, soluble iron salt, and optionally soluble metal M salt in water, and adjust the pH value to 2.5-3.5 to obtain a first deposition solution; dissolve soluble nickel salt, soluble iron salt, and soluble cobalt salt in water, and adjust the pH value to 2.5-3.5 to obtain a second deposition solution; wherein the soluble metal M salt is one or more of soluble copper salt, soluble chromium salt, and soluble zinc salt;

[0010] S2. Using pretreated foam metal as the working electrode and graphite rod as the counter electrode, and using the first deposition solution as the plating solution, perform the first electrodeposition to deposit a NiFe or NiFeM coating on the surface of the foam metal.

[0011] S3. Using a foam metal coated with NiFe or NiFeM as the working electrode and a graphite rod as the counter electrode, and using the second deposition solution as the plating solution, a second electrodeposition is performed to deposit a NiFeCo coating on the surface of the NiFe or NiFeM coating, thereby obtaining a high-performance water electrolysis oxygen evolution catalyst with a double-layer heterojunction.

[0012] Preferably, in the first deposition plating solution, the concentration of soluble nickel salt is 0.1-1M; the concentration of soluble iron salt is 0.05-1M; when the soluble metal M salt is a soluble copper salt or a soluble zinc salt, the concentration of the soluble metal M salt is 0 or 0.001-0.01mol / L; and when the soluble M salt is a soluble chromium salt, the concentration of the soluble metal M salt is 0 or 0.01-0.4mol / L.

[0013] Preferably, in step S2, the current for the first electrodeposition is 10-50 mA, the deposition temperature is 20-45 °C, and the deposition time is 5-60 min.

[0014] Preferably, in the second deposition solution, the concentration of nickel salt is 0.1-1M, the concentration of iron salt is 0.05-0.5M, and the concentration of cobalt salt is 0.05-0.3M.

[0015] Preferably, in step S3, the current for the second electrodeposition is 10-50 mA, the deposition temperature is 20-45 °C, and the deposition time is 5-60 min.

[0016] Preferably, the pretreatment of the foamed metal includes: cutting the foamed metal, then pickling, washing with ethanol and washing with water to remove the oxide layer, impurities and oil stains on the surface of the foamed metal, and finally drying.

[0017] Preferably, the first deposition solution also contains additives, namely boric acid and / or saccharin; in the first deposition solution, the concentration of boric acid is 1-5 g / 100 mL, and the concentration of saccharin is 0.1-1 g / 100 mL.

[0018] Preferably, the second deposition solution also contains additives, wherein the concentration of boric acid in the second deposition solution is 1-5 g / 100 mL and the concentration of saccharin is 0.1-1 g / 100 mL.

[0019] Preferably, the soluble nickel salt is one of nickel nitrate, sulfate, chloride, or acetate.

[0020] The soluble iron salt is one of the following: iron nitrate, sulfate, chloride, and acetate.

[0021] The soluble copper salt is one of copper nitrate, sulfate, chloride, or acetate.

[0022] The soluble cobalt salt is one of the following: cobalt nitrate, sulfate, chloride, or acetate.

[0023] Soluble chromium salts are one of the following: nitrates, sulfates, and chlorides of chromium.

[0024] Soluble zinc salts are one of the following: zinc nitrates, sulfates, chlorides, and acetates.

[0025] The foamed metal is foamed nickel, foamed copper, foamed aluminum, etc.

[0026] As a general inventive concept, the present invention also provides a catalyst prepared by the aforementioned preparation method.

[0027] As a general inventive concept, the present invention also provides an application of the aforementioned catalyst in water electrolysis.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The preparation method of the present invention involves electrodepositing NiFe / NiFeM coating and NiFeCo coating on the surface of foam metal material. These two catalyst layers are not simply superimposed on the surface of foam metal. Instead, different components are combined between the foam metal and NiFe(M) interface and between NiFe(M) and NiFeCo interface to cause electron redistribution and synergistic effect. At the interface between NiFe(M) and NiFeCo, a Fe-Co alloy with high chemical stability and high electrical conductivity is formed. At the same time, the composition and crystal phase between the interfaces are changed to form new coordination structures or interfacial stress, forming a double-layer heterojunction. This induces rapid charge flow and activates the synergistic effect between the interfaces, improving the bonding force between the inner and outer catalyst layers and the number of active sites on the catalyst surface. It also improves the catalyst loading on the foam metal surface and the utilization rate of the overall active material of the electrode, thereby improving the overall catalytic performance and forming a double-layer heterojunction non-precious metal catalyst. This significantly improves the oxygen evolution performance of non-precious metal electrolysis water. The obtained catalyst has a low overpotential, which is far superior to most commercial OER catalysts. Compared with existing technologies, this invention can significantly reduce the overpotential of OER catalyst while also improving the stability of the electrode.

[0030] (2) The preparation method of the present invention has advantages such as simplicity, high efficiency, low cost, low environmental requirements, and easy scale-up. The prepared catalyst has the characteristics of low overpotential, low cost, good catalytic performance, and excellent stability. The catalyst of the present invention, NiFe(M) / NiFeCo@NF, has a stability of 100 mA / cm². -2 The overpotential reaches 196mV at the current density, which is superior to inexpensive electrodes such as Cu@NiFeLDH (281mV), Co3O4 (340mV) and P-Co2N (315mV), and is a significant improvement over currently available commercial catalysts. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1The figures show the electrochemical performance of the catalysts in each example and comparative example, where (a) is the overpotential curve of the catalysts prepared in each example and comparative example; and (b) is the overpotential curve of the catalysts prepared in each example and comparative example at 5, 10, 20, 50, and 100 mA·cm⁻¹. -2 (c) is a multi-stage chronopotential graph under current density; (d) is a 60-hour chronopotential stability test graph of the catalyst prepared in Example 1; (e) is a Tafel slope curve of the catalysts prepared in each example and the comparative example.

[0033] Figure 2 The images show SEM images of the catalysts prepared in Example 1 and Comparative Example 1, where (a) and (b) are SEM images of Example 1 at different magnifications; and (c) and (d) are SEM images of Comparative Example 1 at different magnifications.

[0034] Figure 3 The images shown are standard TEM images of the NiFe / NiFeCo@NF sample prepared in Example 1, where (a) is a TEM image of the sample section at 200 nm, (b) is the total elemental spectrum at that position, (c) is the Ni elemental spectrum, (d) is the Fe elemental spectrum, (e) is the Co elemental spectrum, and (f) is the O elemental spectrum.

[0035] Figure 4 The image shows the electrochemical performance of the NiFeCr / NiFeCo@NF catalyst prepared in Example 3. Detailed Implementation

[0036] This invention provides a method for preparing a high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst, comprising:

[0037] (1) Pre-treat the porous foam metal material to obtain the matrix;

[0038] (2) Preparation of the first and second alloy plating solutions: Dissolve soluble nickel salt, soluble iron salt and soluble metal M salt in water, and adjust the pH value to 2.5-3.5 to obtain the first deposition plating solution; dissolve soluble nickel salt, soluble iron salt and soluble cobalt salt in water, and adjust the pH value to 2.5-3.5 to obtain the second deposition plating solution; the soluble metal M salt is one or more of soluble copper salt, soluble chromium salt and soluble zinc salt;

[0039] (3) Using the obtained foam metal material as the working electrode and the graphite rod as the counter electrode, the two are placed parallel in the first alloy plating solution through the electrolytic cell cover. The deposition current and deposition temperature are adjusted by DC power supply and water bath to perform electrodeposition and deposit NiFe or NiFeM coating on the surface of porous foam metal substrate.

[0040] (4) Using the obtained foam metal material with NiFe or NiFeM deposited on the surface as the working electrode and the graphite rod as the counter electrode, the two are placed in parallel in the second alloy plating solution. The deposition current and deposition temperature are adjusted by DC power supply and water bath to perform electrodeposition. A NiFeCo coating is deposited on the surface of the NiFe or NiFeM coating to obtain a high-performance water electrolysis oxygen evolution catalyst with a double heterojunction.

[0041] In some specific embodiments of the present invention, in step (1), the foam metal material includes, but is not limited to, foam nickel (NF), foam copper, foam aluminum, etc., with foam nickel being preferred.

[0042] In some specific embodiments of the present invention, in step (1), the pretreatment involves cutting the foam metal material and then sequentially performing acid washing, ethanol washing, water washing, and ultrasonic treatment to remove the oxide layer, impurities, and oil stains on the surface of the foam metal, followed by drying at a suitable temperature for later use; wherein, ultrasonic treatment can be performed simultaneously with various cleaning methods to enhance the cleaning effect.

[0043] In some preferred embodiments of the present invention, the concentration of the soluble nickel salt in the first alloy plating solution is 0.1-1M, preferably 0.4-0.9M, more preferably 0.5-0.8M, and even more preferably 0.55-0.75M, such as 0.56M, 0.57M, 0.58M, 0.59M, 0.6M, 0.61M, 0.62M, 0.63M, 0.64M, 0.65M, 0.66M, 0.67M, 0.68M, 0.69M, 0.7M, 0.71M, 0.72M, 0.73M, 0.74M, etc.; the concentration of the soluble iron salt is 0.05M-1M, preferably... The concentration of the soluble metal M salt is 0.1-0.8 M, more preferably 0.1-0.5 M, such as 0.15 M, 0.2 M, 0.25 M, 0.3 M, 0.35 M, 0.4 M, 0.45 M, etc.; when a soluble copper salt or zinc salt is added to the alloy plating solution, the concentration of the soluble metal M salt is 0.001 M-0.01 M, preferably 0.001-0.008 M, such as 0.002 M, 0.003 M, 0.004 M, 0.005 M, 0.006 M, 0.007 M, etc.; when a soluble chromium salt is added to the alloy plating solution, the concentration of the soluble metal M salt is 0.01-0.4 mol / L, preferably 0.1-0.4 mol / L.

[0044] In some preferred embodiments of the present invention, an additive is also added to the first deposition plating solution, the additive being boric acid and / or saccharin; the amount of boric acid added is 1-5 g / 100 mL, and the amount of saccharin added is 0.1-1 g / 100 mL.

[0045] In some preferred embodiments of the present invention, the concentration of the soluble nickel salt in the second alloy plating bath is 0.1M-1M, preferably 0.4-0.9M, more preferably 0.5-0.8M, for example 0.52M, 0.55M, 0.56M, 0.57M, 0.58M, 0.59M, 0.6M, 0.61M, 0.62M, 0.63M, 0.64M, 0.65M, 0.66M, 0.67M, 0.68M, 0.69M. The concentrations of soluble iron salts are 0.05M-0.5M, preferably 0.1-0.45M, such as 0.15M, 0.2M, 0.25M, 0.3M, 0.35M, 0.4M, etc.; the concentrations of soluble cobalt salts are 0.05M-0.3M, preferably 0.05-0.25M, such as 0.1M, 0.15M, 0.2M, etc.

[0046] In some preferred embodiments of the present invention, an additive is also added to the second deposition plating solution, the additive being boric acid and / or saccharin; the amount of boric acid added is 1-5 g / 100 mL, and the amount of saccharin added is 0.1-1 g / 100 mL.

[0047] In some specific embodiments of the present invention, the soluble nickel salt is selected from one of nickel nitrates, sulfates, chlorides, acetates, etc., preferably a sulfate; the soluble iron salt is selected from one of iron nitrates, sulfates, chlorides, acetates, etc., preferably a sulfate; the soluble copper salt is selected from one of copper nitrates, sulfates, chlorides, acetates, preferably a nitrate; the soluble copper salt is selected from one of nitrates, sulfates, chlorides, acetates, preferably a sulfate; the soluble chromium salt is one of chromium nitrates, sulfates, chlorides, chlorides, acetates, preferably a sulfate; and the soluble zinc salt is one of zinc nitrates, sulfates, chlorides, acetates, preferably a sulfate.

[0048] In some specific embodiments of the present invention, dilute hydrochloric acid and sodium hydroxide solution are used to adjust the pH value. For example, the concentration of dilute hydrochloric acid may be, but is not limited to, 1 mol / L, and the concentration of sodium hydroxide solution may be, but is not limited to, 0.1 mol / L, to avoid excessive NaOH concentration from generating precipitation in the plating solution.

[0049] In some preferred embodiments of the present invention, the conditions for the first electrodeposition are as follows: the deposition current is 10-50mA, preferably 15-45mA, such as 20mA, 25mA, 30mA, 35mA, 40mA, etc.; the deposition temperature is 20-45℃, preferably 20-40℃, such as 25℃, 30℃, 35℃, etc.; and the deposition time is 5-60min, preferably 10-50min, such as 15min, 20min, 25min, 30min, 35min, 40min, 45min, etc.

[0050] In some preferred embodiments of the present invention, the conditions for the second electrodeposition are as follows: the deposition current is 10-50 mA, preferably 15-45 mA, such as 20 mA, 25 mA, 30 mA, 35 mA, 40 mA, etc.; the deposition temperature is 20-45 °C, preferably 20-40 °C, such as 25 °C, 30 °C, 35 °C, etc.; and the deposition time is 5-60 min, preferably 10-50 min, such as 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, etc.

[0051] In some specific embodiments of the present invention, after the first electrodeposition and the second deposition are completed, the foam substrate coated with the coating is repeatedly rinsed with deionized water and then continuously dried under vacuum. The drying temperature is 60℃-100℃, and the drying time is 4h-12h.

[0052] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0053] Example 1

[0054] A method for preparing a high-performance two-step electrodeposition catalyst for water electrolysis and oxygen evolution includes the following steps:

[0055] (1) Using nickel foam (NF) cut to 2cm×2cm as a base, take a certain amount of concentrated hydrochloric acid and dilute it to 3mol / L. Immerse the nickel foam in the prepared dilute hydrochloric acid, and then place it in an ultrasonic machine for ultrasonic vibration and washing for 15min, while constantly stirring to remove the oxide layer on the surface of the nickel foam.

[0056] (2) Place the foamed nickel from step (1) in anhydrous ethanol and continue ultrasonic washing for 10 minutes, stirring constantly, repeating twice to ensure that the oil and residual acid on the NF surface are washed away.

[0057] (3) Place the foamed nickel from step (2) in deionized water and continue ultrasonic washing for 10 minutes, stirring constantly, repeating twice to ensure that the foamed nickel slag and other impurities are washed away.

[0058] (4) Place the washed nickel foam from step (3) in a vacuum drying oven at 70°C and continue drying for 4 hours, then seal it in a sealed bag for later use.

[0059] (5) Add 0.7 mol / L nickel sulfate hexahydrate crystals and 0.25 mol / L ferrous sulfate heptahydrate crystals to 100 mL of aqueous solution in sequence, and continue to sonicate for 15 min until they are completely dissolved. Then adjust the pH of the solution to about 3.0 using 1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide prepared in advance to obtain a clear dark green plating solution.

[0060] (6) The nickel foam obtained in step (4) is used as the working electrode and the graphite rod is used as the counter electrode. The two are placed in parallel in the plating solution obtained in step (5). The deposition current is set to 30mA using a DC power supply. After deposition for 30 minutes at room temperature, the power supply is turned off. The deposited nickel foam is taken out and rinsed with deionized water. Then it is placed in a vacuum drying oven at 80℃ and dried for 4 hours to obtain nickel foam with NiFe plated on the surface.

[0061] (7) Add 0.7 mol / L nickel sulfate hexahydrate crystals, 0.25 mol / L ferrous sulfate heptahydrate crystals and 0.1 mol / L cobalt nitrate hexahydrate crystals to 100 mL of aqueous solution in sequence, and continue to sonicate for 30 min until they are completely dissolved. Then adjust the pH of the solution to about 2.5 with 1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide to obtain a clear dark green plating solution.

[0062] (8) The nickel foam with NiFeCo deposited on the surface obtained in step (6) is used as the working electrode and the graphite rod is used as the counter electrode. The two are placed in parallel in the plating solution obtained in step (7). The deposition current is set to 30mA using a DC power supply. After deposition for 30min at room temperature, the power supply is turned off. The deposited nickel foam is taken out and rinsed with deionized water. Then it is placed in a vacuum drying oven at 80℃ and dried for 8h to obtain the nickel foam material with NiFeCo deposited on the surface, namely the high-performance double-layer heterojunction water electrolysis oxygen evolution catalyst NiFe / NiFeCo@NF. It is then placed in a sealed bag for testing.

[0063] Example 2

[0064] The difference between Example 2 and Example 1 is that in step (5), after adding 0.7 mol / L nickel sulfate hexahydrate crystals and 0.25 mol / L ferrous sulfate heptahydrate crystals to 100 mL of aqueous solution, 0.004 mol / L copper sulfate pentahydrate crystals are added and stirred to mix them thoroughly; the catalyst obtained in step (8) is NiFeCu / NiFeCo@NF.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that in step (5), after adding 0.7 mol / L nickel sulfate hexahydrate crystals and 0.25 mol / L ferrous sulfate heptahydrate crystals to 100 mL of aqueous solution, 0.2 mol / L chromium nitrate nonahydrate crystals are added and stirred to mix them thoroughly; the catalyst obtained in step (8) is NiFeCr / NiFeCo@NF.

[0067] Comparative Example 1

[0068] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 only performed electrodeposition once, so up to step (6), the catalyst obtained was NiFe@NF.

[0069] Comparative Example 2

[0070] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 only performs electrodeposition once, but in step (5), after adding 0.7 mol / L of nickel sulfate hexahydrate crystals and 0.25 mol / L of ferrous sulfate heptahydrate crystals in 100 mL of aqueous solution, copper sulfate pentahydrate crystals need to be added at 0.004 mol / L and stirred to mix them thoroughly. There are no subsequent steps, and the resulting catalyst is NiFeCu@NF.

[0071] Comparative Example 3

[0072] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 only performs electrodeposition once, but in step (5), after adding 0.7 mol / L of nickel sulfate hexahydrate crystals and 0.25 mol / L of ferrous sulfate heptahydrate crystals in 100 mL of aqueous solution, it is necessary to add 0.1 mol / L of cobalt nitrate hexahydrate crystals and stir to mix them thoroughly. There are no subsequent steps, and the resulting catalyst is NiFeCo@NF.

[0073] The catalysts obtained in each embodiment and / or comparative example were used to perform performance tests using a three-electrode system. The obtained catalyst was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and a graphite rod with a diameter of 5 mm was used as the counter electrode. A saturated 1M KOH solution was used as the electrolyte. The three-electrode system electrolytic cell was connected to a Gamry electrochemical workstation for a series of tests, including linear sweep voltammetry, stage tests, stability tests using chronoamperometry, and EIS tests.

[0074] The scan rate for the linear sweep voltammetry test was set to 5 mV / s, and the results are shown in the attached figure. Figure 1 (a) When the current density is 100 mA·cm -2 When 100% IR compensation was performed, the results are shown in Table 1. The overpotential of Example 1 was only 196 mV, which is much lower than that of currently commercially available precious metal oxygen evolution catalysts. Compared with other examples and comparative examples, Example 1 also showed the best oxygen evolution reaction catalytic performance.

[0075] Phase-based testing, set at 5mA·cm -2 10mA·cm -2 20mA·cm -2 50mA·cm -2 and 100mA·cm -2 Different current densities were used to test the stability and overpotential of each embodiment and comparative example at current densities ranging from small to large. The results are shown in Table 2. Figure 1 (b) It can be seen that, although the test duration was only 30 minutes, all examples and comparative examples showed good stability and catalytic performance at different current densities in the five stages.

[0076] Stability testing was conducted using the chronoamperometry method. Besides catalytic activity, long-term stability is also a crucial parameter for evaluating a catalyst's superiority and practical application. The results for the sample in Example 1 are attached. Figure 1 (c) As can be seen from the figure, Example 1 at 100 mA·cm -2 Under high current for more than 60 hours, the potential did not deviate significantly. The slight fluctuations may be due to the generation of oxygen and its escape from the catalyst. This shows that Example 1 can still maintain good performance after long-term use without significant degradation, and has good durability and stability.

[0077] Tafel slope fitting analysis, through formula η = a + blog iη The Tafel slope can be derived from the given relationship between overpotential and current density and the test data. bThe smaller the Tafel slope, the faster the current density increases with the same increase in potential, and the better the kinetics and catalytic performance. (See attached image) Figure 1 (d) represents the Tafel slope of catalysts prepared under different conditions. The catalyst NiFe / NiFeCo@NF prepared in Example 1 exhibits the lowest Tafel slope of 34 mV / dec, indicating that this catalyst has the best catalytic performance and better kinetic performance, which is consistent with the results presented by LSV. This may be related to its obvious network structure on its surface, which has a higher specific surface area and more active sites.

[0078] The morphology of the catalysts obtained in Example 1 and Comparative Example 1 was observed by scanning electron microscopy (SEM), as follows: Figure 2 As shown, (a) and (b) are SEM images of Example 1 at different magnifications; (c) and (d) are SEM images of Comparative Example 1 at different magnifications; from the appendix... Figure 2 As can be seen in (a) and (c), both are banded nanostructures. However, because Example 1 involves an additional electrodeposition compared to Comparative Example 1, resulting in a new NiFeCo coating, the banded nanostructure formed in the former is thicker and denser. While not obscuring the porous structure of the NF surface, it tightly binds to the NF through complex texture features, allowing for more thorough contact between the catalyst and the solution, and providing more pores for gas transport during the oxygen evolution process. Due to the tight bonding between the upper and lower catalyst layers, the former provides a more complete coverage of the NF substrate than the latter, and the NF surface structure is not observable at the bottom, providing a high specific surface area and more active sites, which is beneficial for improving its OER catalytic performance. (Comparative Appendix) Figure 2 (b) and (d) and the data in Table 3 show that, due to the deposition of an additional NiFeCo layer, the catalyst thickness on the NF surface in Example 1 was significantly increased compared to Comparative Example 1. Therefore, the catalyst loading was significantly increased, and the surface protrusions further increased the specific surface area of ​​the catalyst.

[0079] The catalyst loading of each embodiment and comparative example was tested, and the results are shown in Table 3. It can be seen from the table that the catalyst loading of Example 1 and Example 2 is much higher than that of Comparative Examples 1-3. It can be seen that first electrodepositing NiFe or NiFeCu coating and then electrodepositing NiFeCo coating can effectively improve the catalyst loading.

[0080] The EIS test results are shown in Table 3. Comparing the internal resistance of the catalysts in each example and the comparative example, it can be seen that the NiFe / NiFeCo@NF catalyst prepared in Example 1 exhibits the best performance (overpotential 196mV, Tafel slope 34mV / dec) while also showing a low internal resistance of 0.422Ω, second only to the NiFeCu / NiFeCo@NF catalyst obtained in Example 2 (0.364Ω). The addition of Cu in Example 2 reduced the internal resistance of its sample. Under 100% IR compensation, the internal resistance of Example 2 was lower than that of Comparative Example 3. Therefore, the reduction in overpotential after compensation was less than that of Comparative Example 3, making the overpotentials of the two samples more similar. However, the overpotential of Example 2 before compensation was more than 30mV lower than that of Comparative Example 3. This is because the addition of highly conductive Cu in Example 2 improved the catalyst's conductivity, reduced its minimum charge transfer resistance and voltage consumption, and did not significantly affect the catalyst's performance. Therefore, in Example 1 of this invention, Cu, Zn, and other metal elements can be added to further improve the catalyst's conductivity and reduce voltage consumption, thus saving costs.

[0081] The TEM image of the catalyst obtained in Example 1 is shown below. Figure 3 As shown. Generally, heterojunction catalysts consist of two or more components linked by a well-defined interface. The NiFe / NiFeCo@NF catalyst described in Example 1 forms two catalyst layers on the NF surface through two electrodepositions with different bath ratios. These two catalyst layers do not simply exist on the NF surface in a superimposed manner, but rather, through the bonding between the NF and NiFe interfaces, and between the NiFe and NiFeCo interfaces, different components are formed, causing electron redistribution and synergistic effects. For example... Figure 3 As shown in (a), the first-layer heterojunction forms between the NF substrate and the NiFe catalyst under the interfacial stress of deposition, i.e., region A, which corresponds to region A in the elemental spectrum (b); combined with Figure 3 (e) and (f) show that the distributions of Co and O elements are almost identical, indicating that there is a large amount of Co oxide on the surface of the sample in Example 1. The second heterojunction is presumably due to the presence and dissolution of iron compounds on the surface of NiFeCo during the OER process, which leads to the incorporation of more active Fe cations into the crystal structure gaps of Co oxides. At the same time, it changes the composition and crystal phase between the interfaces to form new coordination structures or interfacial stresses, forming a Fe-Co alloy with high chemical stability and high electrical conductivity, thus forming another heterojunction, namely region B, which corresponds to region B in elemental diagram (b). Figure 3(c), (d), (e), and (f) correspond to the elements Ni, Fe, Co, and O, respectively. This structure effectively couples the two catalyst layers with the NF through strong electronic interactions, generating or activating more active iron sites on the catalyst surface. The uniform distribution of Co also exposes a larger specific surface area for the Co-Ni support, further optimizing the electronic structure and charge transfer performance of the catalyst in the OER process. Furthermore, the addition of Co atoms forms a Fe-Co alloy heterostructure with stronger bonding and a larger specific surface area, further enhancing its OER catalytic performance and stability. Moreover, the unique charge flow of this bilayer heterostructure results in a lower charge transfer resistance for the catalyst itself, leading to a faster charge transfer rate between the NF and the catalyst layers. All of these factors play a crucial role in improving the catalyst's OER performance.

[0082] The catalyst prepared in Example 3 had an overpotential of 190 mV and an internal resistance of 0.415 Ω. Compared with Example 1, this shows that the addition of Cr can reduce the internal resistance while maintaining the catalyst performance. Furthermore, based on the elemental characteristics, the addition of Cr can improve the corrosion resistance of the catalyst to a certain extent.

[0083] Table 1. Catalysts prepared in each example and comparative example at 100 mA·cm⁻¹ -2 Overpotential at current density

[0084]

[0085] Table 2. Overpotentials of the catalysts in the examples and comparative examples at various current densities during phase testing.

[0086]

[0087] Table 3. Comparison of catalyst loading values ​​between each embodiment and the comparative example.

[0088]

[0089] Table 4. Catalyst internal resistance values ​​for each embodiment and comparative example.

[0090]

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst, characterized in that, include: S1. Dissolve soluble nickel salt, soluble iron salt, and optionally soluble metal M salt in water, and adjust the pH value to 2.5-3.5 to obtain a first deposition solution; dissolve soluble nickel salt, soluble iron salt, and soluble cobalt salt in water, and adjust the pH value to 2.5-3.5 to obtain a second deposition solution; wherein the soluble metal M salt is one or more of soluble copper salt, soluble chromium salt, and soluble zinc salt; S2. Using pretreated foam metal as the working electrode and graphite rod as the counter electrode, and using the first deposition solution as the plating solution, perform the first electrodeposition to deposit a NiFe or NiFeM coating on the surface of the foam metal. S3. Using a foam metal coated with NiFe or NiFeM as the working electrode and a graphite rod as the counter electrode, and using the second deposition solution as the plating solution, a second electrodeposition is performed to deposit a NiFeCo coating on the surface of the NiFe or NiFeM coating, thereby obtaining a high-performance water electrolysis oxygen evolution catalyst with a double-layer heterojunction.

2. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, In the first deposition plating solution, the concentration of soluble nickel salt is 0.1-1 mol / L; the concentration of soluble iron salt is 0.05-1 mol / L; when the soluble metal M salt is a soluble copper salt or a soluble zinc salt, the concentration of the soluble metal M salt is 0 or 0.001-0.01 mol / L; when the soluble M salt is a soluble chromium salt, the concentration of the soluble metal M salt is 0 or 0.01-0.4 mol / L.

3. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, In step S2, the current for the first electrodeposition is 10-50 mA, the deposition temperature is 20-45 °C, and the deposition time is 5-60 min.

4. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, In the second deposition solution, the concentration of soluble nickel salt is 0.1-1 mol / L, the concentration of soluble iron salt is 0.05-0.5 mol / L, and the concentration of soluble cobalt salt is 0.05-0.3 mol / L.

5. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, In step S3, the current for the second electrodeposition is 10-50 mA, the deposition temperature is 20-45 °C, and the deposition time is 5-60 min.

6. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, The first deposition solution also contains additives, namely boric acid and / or saccharin; the concentration of boric acid in the first deposition solution is 1-5 g / 100 mL, and the concentration of saccharin is 0.1-1 g / 100 mL. The second deposition solution also contains additives, namely boric acid and / or saccharin; the concentration of boric acid in the second deposition solution is 1-5 g / 100 mL, and the concentration of saccharin is 0.1-1 g / 100 mL.

7. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, The pretreatment of the foamed metal includes: cutting the foamed metal, then pickling, washing with ethanol and washing with water to remove the oxide layer, impurities and oil stains on the surface of the foamed metal, and finally drying.

8. The preparation method of the high-performance bilayer heterojunction water electrolysis oxygen evolution catalyst as described in claim 1, characterized in that, The soluble nickel salt is one of nickel nitrate, sulfate, chloride, or acetate. The soluble iron salt is one of the following: iron nitrate, sulfate, chloride, and acetate. The soluble copper salt is one of copper nitrate, sulfate, chloride, or acetate. The soluble cobalt salt is one of the following: cobalt nitrate, sulfate, chloride, or acetate. Soluble chromium salts are one of the following: nitrates, sulfates, and chlorides of chromium. Soluble zinc salts are one of the following: zinc nitrates, sulfates, chlorides, and acetates. The foamed metal is foamed nickel, foamed copper, or foamed aluminum.

9. The catalyst prepared by the method according to any one of claims 1-8.

10. The application of the catalyst as described in claim 9 in water electrolysis.

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