Sr atom modified cooh nanosheet catalyst and preparation method and application thereof

Abstract

The application discloses a Sr atom modified CoOOH nanosheet catalyst and a preparation method and application thereof. The Sr atom modified CoOOH nanosheet catalyst is prepared by a simple solvothermal method and in-situ electrochemical reconstruction under alkaline anode oxygen evolution reaction conditions. d The Sr atom modified CoOOH nanosheet catalyst reduces the electron cloud density around the metal cobalt through Sr atom modification, simultaneously The center of the band is moved to the Fermi level, so that the orbital hybridization of the Co site and the reaction intermediate is enhanced, the adsorption of the oxygen-containing intermediate is promoted, and thus the activity of the alkaline anode oxygen evolution reaction is improved. The catalyst shows excellent catalytic activity and stability in an anion exchange membrane water electrolysis hydrogen production anode oxygen evolution reaction, and provides a new idea for industrialization development of the anion exchange membrane water electrolysis hydrogen production technology.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional nanosheet material synthesis and electrocatalysis technology, specifically relating to a Sr atom-modified CoOOH nanosheet catalyst, its preparation method, and its application. Background Technology

[0002] Electrolysis of water for hydrogen production is a key technology for coupling renewable energy and achieving stable hydrogen production. Anion exchange membrane (EEM) water electrolysis combines the high efficiency of proton exchange membrane electrolysis with the low cost of traditional alkaline electrolysis, and is compatible with non-precious metal catalysts, significantly reducing system costs. Currently, this technology is constrained by the slow kinetics of the oxygen evolution reaction (OER) at the anode and the difficulty in synergistically balancing activity and stability, severely limiting reaction efficiency and lifespan. Therefore, developing highly active and durable non-precious metal-based OER catalysts and overcoming the key technical challenges hindering anion exchange membrane water electrolysis is of significant strategic importance for promoting large-scale green hydrogen production, improving the hydrogen energy industry chain, and ensuring energy security.

[0003] Currently, cobalt hydroxyoxide (CoOOH) is widely studied as a highly active phase in the basic oxygen evolution reaction. CoOOH prepared by in-situ reconstruction is rich in... d Electrons and empty orbitals exhibit significantly higher activity than directly synthesized materials. For example, in *Advanced Materials*... Advanced Materials (37, 2501381, 2025) reported an N, F co-doped Co3O4 precatalyst, in which a CoOOH active layer generated by surface reconstruction during alkaline OER significantly reduces the reaction energy barrier and optimizes the alkaline OER pathway. Therefore, developing reconstructed cobalt-based catalysts for regulating alkaline OER has become a feasible strategy.

[0004] However, in the oxygen evolution reaction (OER) of anion exchange membrane water electrolysis for hydrogen production, the reconstruction process of N and F co-doped Co3O4 is limited by the spinel matrix structure, resulting in a limited depth of transformation only at the surface layer. Complete bulk reconstruction is difficult to achieve, leading to insufficient exposure of active sites and hindered charge transport. To date, few studies have achieved deep bulk reconstruction of cobalt-based precatalysts or clearly elucidated the structure-activity relationship between the degree of reconstruction and OER activity. This means that the alkaline OER reaction still cannot fully utilize the intrinsic catalytic advantages of reconstructed CoOOH, thus limiting the energy efficiency improvement of anion exchange membrane water electrolysis for hydrogen production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a Sr atom-modified CoOOH nanosheet electrocatalyst, its preparation method, and its application. This enables Sr atom-modified CoOOH with a two-dimensional nanosheet structure to achieve high catalytic activity and durability in the process of hydrogen production by anion exchange membrane water electrolysis, effectively overcoming the technical problem in existing technologies where uncontrollable remodeling makes it difficult to synergistically improve catalytic activity and stability.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, this invention provides an Sr-modified CoOOH nanosheet electrocatalyst. By precisely constructing an Sr-modified CoOOH nanosheet structure under electrochemical in-situ reconstruction conditions, and leveraging the electronic regulation of Sr atoms and optimization of the coordination environment, the local electron cloud distribution of the active center of metallic Co is effectively controlled, inducing the Co sites to exhibit higher oxidation states. Simultaneously, Sr modification can regulate the oxidation characteristics of CoOOH. d By shifting the oxygen intermediate to the Fermi level, the orbital hybridization and charge transfer between the oxygen-containing intermediate and the Co active site are further enhanced, thereby optimizing the adsorption-desorption energy barrier of the reaction intermediate. This ultimately achieves a simultaneous improvement in the intrinsic activity and long-term stability of the oxygen evolution reaction in alkaline media, providing a new solution for the industrial application of anion exchange membrane electrolysis for hydrogen production.

[0007] A second aspect of the present invention discloses a method for preparing Sr atom-modified CoOOH nanosheet electrocatalysts, comprising: It provides cobalt-containing precursors, strontium sources, and sulfur sources; Based on the cobalt-containing precursor, strontium source, and sulfur source, an Sr-doped cobalt sulfide precursor was prepared. The Sr-doped cobalt sulfide precursor was placed in an alkaline electrolyte and subjected to in-situ electrochemical reconstruction under oxygen evolution reaction conditions to obtain an Sr atom-modified CoOOH nanosheet catalyst.

[0008] Preferably, the preparation method of Sr atom-modified CoOOH nanosheet electrocatalyst disclosed in this invention specifically includes the following steps: Step 1: At room temperature, cobalt salt and dimethylimidazole are dispersed separately in deionized water solution. The dimethylimidazole solution is added dropwise to the cobalt salt solution, and the mixture is magnetically stirred. After washing and centrifugation, the ZIF-67 precursor is obtained.

[0009] Step 2: The ZIF-67 precursor and strontium salt are uniformly dispersed in water to prepare a mixed solution. The thioamide sulfur source is dispersed in deionized water. The sulfur source solution is added dropwise to the mixed solution of ZIF-67 precursor and Sr salt. Strontium-doped cobalt sulfide nanosheets are synthesized by a simple solvothermal method.

[0010] Step 3: The prepared strontium-doped cobalt sulfide nanosheets are placed under alkaline water electrolysis and oxygen evolution reaction conditions, and Sr atom-modified CoOOH nanosheet electrocatalysts are obtained through in-situ electrochemical oxidation reconstruction.

[0011] Preferably, the cobalt salt is one of cobalt acetate, cobalt nitrate, cobalt chloride, cobalt sulfate, or cobalt acetylacetonate; the strontium salt is one of strontium acetate, strontium nitrate, strontium chloride, or strontium acetylacetonate; and the thioamide is one or a mixture of N,N-dimethylthioacetamide, thioacetamide, thiobenzamide, or thiopropionamide.

[0012] Preferably, the ratio of the total molar amount of cobalt salt and strontium salt to the molar amount of thioamide sulfur source is 1:(1~2); the molar ratio of strontium salt to cobalt salt is (0.001~1):1.

[0013] Preferably, cobalt salt and dimethylimidazole are dispersed in aqueous solution, and the dimethylimidazole solution is slowly added dropwise to the cobalt salt solution. After stirring continuously for 3-7 hours, the ZIF-67 precursor is obtained by washing with deionized water and centrifuging.

[0014] As a preferred method, ZIF-67 precursor and strontium salt and thioamide sulfur source are dispersed in deionized water, and the sulfur source solution is slowly added dropwise to the mixed solution of ZIF-67 precursor and Sr salt. The reaction is carried out at 120℃~150℃ for 5~10h to obtain strontium-doped cobalt sulfide nanosheets.

[0015] As a preferred method, the prepared strontium-doped cobalt sulfide nanosheets are placed under alkaline water electrolysis anodic oxygen evolution reaction conditions, and in-situ electro-oxidation reconstruction is carried out in potassium hydroxide electrolyte to obtain Sr atom-modified CoOOH nanosheet catalyst.

[0016] As a preferred embodiment, under alkaline water electrolysis anodic oxygen evolution reaction, the voltage range of electro-oxidation reconstruction is (0-1.2)V~(1.4-2.0)V vs. RHE, and the scan rate is 1mV / s~1000mV / s.

[0017] A third aspect of the present invention provides the application of Sr atom-modified CoOOH nanosheet catalyst in the oxygen evolution reaction at the anode of anion exchange membrane water electrolysis for hydrogen production.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The Sr-atom-modified CoOOH nanosheet catalyst disclosed in this invention not only enhances Co-O covalentity and reduces the electron cloud density around Co sites through Sr atom modification, providing high-valence cobalt sites, but also... dThe upward shift of the band center enhances the orbital interaction between the reaction intermediate and the Co site, promotes the adsorption of oxygen-containing intermediates, and thus reduces the overpotential of the alkaline oxygen evolution reaction.

[0019] This invention employs a simple solvothermal method to prepare strontium-doped cobalt sulfide through in-situ electro-oxidation reconstruction. The operation is simple, and the raw materials are inexpensive and readily available.

[0020] From a practical application perspective, the Sr-modified CoOOH nanosheet catalyst obtained in this invention simultaneously achieves excellent catalytic activity and long-term operational stability in the anodic oxygen evolution reaction of anion exchange membrane water electrolysis for hydrogen production. At 10 mA / cm², 2 At a current density of 2A / cm², the overpotential of Sr-modified CoOOH nanosheets is only 257 mV, which is 31 mV lower than that of CoOOH nanosheet catalysts and 50 mV lower than that of commercial ruthenium oxide catalysts. At an overpotential of 300 mV, the current density of this catalyst is 8.07 times that of commercial ruthenium oxide, demonstrating excellent alkaline electrocatalytic activity for the oxygen evolution reaction (OER). Furthermore, after 3000 accelerated cycles of OER, the overpotential of the Sr-modified CoOOH nanosheet catalyst did not increase significantly, demonstrating its unique durability in the anode reaction of anion exchange membrane water electrolysis for hydrogen production. Moreover, in the industrial application of anion exchange membrane water electrolysis, 2A / cm²... 2 At a current density of 500 mA / cm², the Sr-modified CoOOH nanosheet catalyst exhibits a cell voltage of only 1.84 V, which is 0.57 times that of commercial ruthenium oxide catalysts. In an anion exchange membrane water electrolysis hydrogen production system, this catalyst achieves a cell voltage of only 1.84 V / cm². 2 At a current density of [value missing], it can operate stably for 60 hours with a decay rate of only 0.87 mV / h. Therefore, the prepared Sr atom-modified CoOOH nanosheet catalyst exhibits industrial application potential with both high activity and high stability in the field of anion exchange membrane water electrolysis for hydrogen production. Attached Figure Description

[0021] Figure 1 Transmission electron microscope images of Sr atom-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2; where a is a Sr atom-modified CoOOH nanosheet and b is a CoOOH nanosheet.

[0022] Figure 2 The image shows the scanning transmission electron microscope-elemental analysis of the Sr atom-modified CoOOH nanosheets prepared in Example 1; where a is a high-angle annular dark field image; b is the elemental distribution analysis of Co; c is the elemental distribution analysis of O; and d is the elemental distribution analysis of Sr.

[0023] Figure 3 Comparison of X-ray diffraction (XRD) spectra of Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2, and their corresponding sulfide substrates. In Figure a, a is a comparison of the XRD spectra of Sr-modified CoOOH nanosheets and CoOOH nanosheets, and b is a comparison of the corresponding precursor sulfides.

[0024] Figure 4 Comparison of X-ray photoelectron spectra of Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2. Where a represents Co₂. p X-ray photoelectron spectrum; b represents O 1 s X-ray photoelectron spectrum; comparison of subband content of O (c).

[0025] Figure 5 Extended X-ray absorption fine structure spectra of Sr atom-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2.

[0026] Figure 6 Comparison of UV photoelectron spectra of Sr atom-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2.

[0027] Figure 7 Linear scan curves of Sr atom-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2, and commercial ruthenium oxide catalyst in the oxygen evolution reaction at the anode of alkaline water electrolysis.

[0028] Figure 8 The image shows a comparison of the linear scan curves of the Sr atom-modified CoOOH nanosheets prepared in Example 1 before and after a 3000-cycle test.

[0029] Figure 9 The curves show a performance comparison of the Sr-modified CoOOH nanosheets prepared in Example 1 and a commercial ruthenium oxide catalyst in the process of hydrogen production by anion exchange membrane water electrolysis.

[0030] Figure 10 The durability test curves of the Sr atom-modified CoOOH nanosheets prepared in Example 1 in an anion exchange membrane water electrolysis hydrogen production system are shown. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings: This invention provides a method for preparing Sr atom-modified CoOOH nanosheet electrocatalysts. This method achieves stable modification of Sr atoms in the CoOOH lattice by constructing a specific precursor structure and combining it with an in-situ electrochemical reconstruction strategy.

[0034] Specifically, the preparation method includes the following steps: Step S1 involves providing a cobalt-containing precursor, a strontium source, and a sulfur source. The cobalt-containing precursor, serving as the source of cobalt, can be in the form of a salt solution, solid powder, or a specific coordination polymer framework structure, which can be selected by those skilled in the art according to actual needs. The strontium source and sulfur source respectively provide the Sr atoms required for modification and the S element required for forming the sulfide precursor.

[0035] Step S2 involves preparing an Sr-doped cobalt sulfide precursor based on a cobalt-containing precursor, a strontium source, and a sulfur source. This step utilizes chemical synthesis to pre-assemble Sr, S, and Co atoms at the molecular or lattice level, forming an Sr-doped cobalt sulfide compound. The structural design of this intermediate product is crucial, providing a structural template and elemental source for the subsequent reconstruction process. This ensures that Sr elements are uniformly dispersed within the precursor matrix, avoiding localized agglomeration.

[0036] Step S3 involves placing the Sr-doped cobalt sulfide precursor in an alkaline electrolyte and performing in-situ electrochemical reconstruction under oxygen evolution reaction conditions to obtain an Sr-atom-modified CoOOH catalyst. This step is the core of the preparation method of this invention. Under the high-potential environment of the oxygen evolution reaction, the sulfides in the precursor undergo oxidative decomposition, while the OH groups in the electrolyte... - The catalyst participates in the reaction, inducing deep reconstruction of the material. During this process, Sr atoms originally doped in the cobalt sulfide lattice are anchored in situ at newly formed CoOOH lattice sites as the lattice structure evolves. Compared to traditional post-treatment doping or surface modification, this in-situ reconstruction strategy achieves uniform distribution and stable binding of Sr atoms in the CoOOH bulk phase, effectively preventing the loss of active components during long-term operation. Simultaneously, the intense electrochemical oxidation environment promotes the formation of surface defects and the exposure of active sites, further enhancing the catalyst's activity.

[0037] Through the above preparation method, this embodiment successfully constructed a Sr atom-modified CoOOH catalyst with a specific microscopic electronic structure. The method has a simple process flow, does not require complex equipment, and has a wide range of raw material sources, providing a feasible technical path for the large-scale preparation of high-performance oxygen evolution catalysts.

[0038] Further, the cobalt-containing precursor includes ZIF-67 obtained by reacting cobalt salt with an organic ligand. The step of preparing the Sr-doped cobalt sulfide precursor includes: dispersing the ZIF-67, strontium source, and sulfur source in a solvent, and carrying out a solvothermal reaction at 120℃~150℃ for 5h~10h.

[0039] Furthermore, the preparation of the ZIF-67 precursor includes the following steps: Step S1, Preparation of ZIF-67 precursor. At room temperature, a cobalt salt (such as cobalt nitrate hexahydrate) is dissolved in water and stirred until homogeneous to obtain a cobalt salt solution; an organic ligand (such as dimethylimidazole) is dissolved in water and uniformly dispersed to obtain a ligand solution. Subsequently, the ligand solution is added dropwise to the cobalt salt solution, and the reaction is continuously stirred for 3-7 hours. After the reaction is complete, the resulting precipitate is washed with water, centrifuged, and freeze-dried to obtain the ZIF-67 precursor. ZIF-67, as a typical metal-organic framework material, has a regular pore structure and abundant coordination sites, which provides an ideal confined space for the entry of sulfur ions and the doping of strontium ions during the subsequent sulfidation process, facilitating the formation of a uniform nanosheet precursor structure.

[0040] Step S2, Preparation of Sr-doped cobalt sulfide precursor. The ZIF-67 prepared above is dispersed in water to form a homogeneous suspension. A strontium source (such as strontium nitrate solution) is added and stirred until homogeneous, followed by the dropwise addition of a sulfur source (such as thioacetamide solution). The mixed solution is transferred to a reaction vessel and subjected to a solvothermal reaction at 120℃~150℃ for 5h~10h. For example, the reaction is carried out at 130℃ for 7h. After the reaction, the precursor is obtained by centrifugation, washing, and drying. In this process, the temperature and time of the solvothermal reaction are key process parameters. Too low a temperature (below 120℃) may lead to incomplete sulfidation and poor crystallinity of the precursor; too high a temperature (above 150℃) may destroy the framework structure of ZIF-67, causing product morphology collapse or agglomeration. Similarly, too short a reaction time (less than 5h) makes it difficult to form a complete nanosheet structure, while too long a time (more than 10h) may cause excessive grain growth and reduce the specific surface area. By controlling the above process parameters, it is possible to ensure that the ZIF-67 framework undergoes a topological transformation during sulfidation, guiding the generation of Sr-doped cobalt sulfide precursors with a two-dimensional nanosheet structure. This unique two-dimensional structure provides abundant active site exposure and short-range charge transport channels for subsequent electrochemical reconstruction.

[0041] Step S3, in-situ electrochemical reconstruction. The prepared Sr-doped cobalt sulfide nanosheet precursor was dispersed in an alcohol solution of Nafion, drop-coated onto the surface of the working electrode, and placed in an alkaline electrolyte (such as potassium hydroxide solution). Cyclic voltammetry was performed within the oxygen evolution reaction potential range to induce in-situ electrochemical reconstruction, ultimately yielding an Sr atom-modified CoOOH catalyst.

[0042] Example 1 A method for preparing Sr atom-modified CoOOH nanosheets includes the following steps: Step 1, Preparation of ZIF-67 precursor: At room temperature, 658.9 mg of cobalt nitrate hexahydrate was dissolved in 48 mL of water and stirred to disperse it evenly. 191.1 mg of dimethylimidazole was dissolved in 48 mL of water and dispersed evenly. The solution was then added dropwise to the cobalt solution and stirred for 5 h. The resulting solution was washed with water, centrifuged, and freeze-dried to obtain the ZIF-67 precursor.

[0043] Step 2, Preparation of Strontium-doped cobalt sulfide nanosheets: The prepared ZIF-67 was dispersed in 38 mL of water to form a homogeneous solution. 1 mL of 28.8 mg / mL strontium nitrate solution was added and stirred to disperse it evenly. 1 mL of 192 mg / mL thioacetamide solution was added dropwise. After magnetic stirring for 30 min, the solution was solvothermal reacted at 130 °C for 7 h. The resulting solution was centrifuged with water and ethanol, washed, and vacuum dried to obtain strontium-doped cobalt sulfide nanosheets.

[0044] Step 3, Preparation of Sr atom-modified CoOOH nanosheets: The strontium-doped cobalt sulfide nanosheets prepared above were dispersed in an alcohol solution of Nafion. An appropriate amount of the slurry was drop-coated onto the surface of the working electrode. The working electrode was placed in an oxygen-saturated potassium hydroxide solution, and electrochemical in-situ oxidation was performed at a scan rate of 50 mV / s within the potential range of 1.02 V to 1.50 V vs. RHE to obtain the reconstructed Sr atom-modified CoOOH nanosheet catalyst.

[0045] Example 2 A method for preparing a CoOOH nanosheet catalyst differs from Example 1 in that it omits Sr salt and uses a different amount of Co salt. The method includes the following steps: Step 1, Preparation of ZIF-67 precursor: At room temperature, 698.5 mg of cobalt nitrate hexahydrate was dissolved in 48 mL of water and stirred to disperse it evenly. 191.1 mg of dimethylimidazole was dissolved in 48 mL of water and dispersed evenly. The solution was then added dropwise to the cobalt solution and stirred for 5 h. The resulting solution was washed with water, centrifuged, and freeze-dried to obtain the ZIF-67 precursor.

[0046] Step 2, Preparation of cobalt sulfide nanosheets: The prepared ZIF-67 was dispersed in 39 mL of water to form a homogeneous solution. 1 mL of 192 mg / mL thioacetamide solution was added dropwise. After magnetic stirring for 30 min, the solution was solvothermal reacted at 130 °C for 7 h. The resulting solution was centrifuged with water and ethanol, washed, and vacuum dried to obtain cobalt sulfide nanosheets.

[0047] Step 3, Preparation of CoOOH nanosheets: The cobalt sulfide nanosheets prepared above were dispersed in an alcoholic solution of Nafion. An appropriate amount of the slurry was drop-coated onto the surface of the working electrode. The working electrode was placed in an oxygen-saturated potassium hydroxide solution, and electrochemical in-situ oxidation was carried out at a scan rate of 50 mV / s within the potential range of 1.02 V to 1.50 V vs. RHE to obtain the reconstructed Sr atom-modified CoOOH nanosheet catalyst.

[0048] The structure of the Sr atom-modified CoOOH nanosheets prepared in the above examples was tested.

[0049] Test 1: Transmission electron microscopy and elemental analysis.

[0050] like Figure 1Figure a shows a transmission electron microscope image of the Sr-modified CoOOH prepared in Example 1. The obtained sample is a two-dimensional nanosheet structure, composed of a large number of stacked small nanosheets with sizes ranging from 10 nm to 50 nm. This unique micro-assembly method endows the material with a rich porous structure. For comparison, as shown in Figure a... Figure 1 Figure b in the image shows a transmission electron microscope image of the CoOOH prepared in Example 2, revealing a sheet-like structure. This indicates that the introduction of Sr does not alter the nanosheet structure of the substrate sulfide, and this comparative result strongly demonstrates that the introduction of Sr atoms did not disrupt the main morphological framework of the CoOOH substrate.

[0051] From an effectiveness perspective, the two-dimensional nanosheet structure provided by this invention plays a crucial role in enhancing the performance of the electrocatalytic oxygen evolution reaction (OER). The ultrathin two-dimensional sheet structure significantly increases the specific surface area of ​​the material, thereby exposing more Co active sites and providing a richer reaction interface for the electrochemical reaction. Therefore, the Sr-modified CoOOH catalyst described in this embodiment achieves a unity of macroscopic morphology and microscopic activity through the synergistic effect of the two-dimensional nanosheet morphology and the electronic structure regulation of Sr atom modification, providing a structural basis for the design of high-performance OER catalysts.

[0052] like Figure 2 The scanning transmission electron microscopy-elemental analysis diagram of the Sr atom-modified CoOOH nanosheets prepared in Example 1 shows that, Figure 2 In the image, 'a' represents a high-angle annular dark field image. Figure 2 In this context, 'b' represents the distribution analysis of the Co element. Figure 2 In this context, 'c' represents the distribution analysis of the O element. Figure 2 In this context, d represents the distribution analysis of Sr elements. Figure 2 It can be seen that Co, O and Sr elements are uniformly distributed in the nanosheets. The uniform distribution of Co, O and Sr elements in the nanosheet structure confirms that Sr atoms were successfully introduced into the lattice structure of CoOOH, rather than simple surface adsorption or mixing.

[0053] Test 2: X-ray diffraction pattern analysis.

[0054] like Figure 3 The image shows a comparison of the X-ray diffraction patterns of the Sr-modified CoOOH nanosheets prepared in Examples 1 and 2, and the CoOOH nanosheets and their corresponding sulfide substrates. Figure 3 It can be seen that the obtained Sr atom-modified CoOOH nanosheets have the same phase structure as CoOOH nanosheets, and both are transformed into amorphous forms after reconstruction. This indicates that the introduction of Sr atoms did not destroy the main crystal lattice framework of CoOOH, but existed in the lattice sites in an atomically dispersed form.

[0055] Test 3: X-ray electron spectroscopy analysis.

[0056] like Figure 4 , Figure 4 The X-ray photoelectron spectra of Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2 are compared. Where a represents Co₂. p X-ray electron spectrum; b is O 1 s A comparison of O content in X-ray electron spectra. (From...) Figure 4 As shown in 'a', compared to CoOOH nanosheets, the binding energies of the metal Co sites in Sr-modified CoOOH nanosheets all exhibit a positive shift, indicating that the valence electron density of the Co sites decreases after the introduction of Sr atoms. This positive shift in binding energy suggests that, because Sr atoms are less electronegative than Co atoms, when Sr atoms enter the CoOOH lattice, they reduce the electron cloud density around the Co sites, causing the Co sites to exhibit higher valence oxidation characteristics. This is beneficial for enhancing the adsorption capacity of active sites for reaction intermediates. Figure 4 As shown in b and c, by comparing the O content in the X-ray photoelectron spectrum of O element, the Sr atom modified CoOOH nanosheets adsorb more water content than CoOOH nanosheets, which is beneficial to water adsorption and activation.

[0057] Test 4: Fine-grained structural analysis.

[0058] like Figure 5 The image shows the extended X-ray absorption fine structure spectra of the Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2. Figure 5 It can be seen that, compared with CoOOH nanosheets, the Co-O bond length of Sr atom-modified CoOOH nanosheets is significantly shorter. The shortened bond length indicates that the covalentity of the Co-O bond is enhanced. This enhanced covalent interaction helps to accelerate the charge transfer rate in the electrocatalytic process, thereby improving the catalytic reaction kinetics.

[0059] Test 5: Ultraviolet photoelectron spectroscopy analysis.

[0060] Figure 6 Comparison of UV photoelectron spectra of Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2. Figure 6 It can be seen that the Sr atom-modified CoOOH nanosheets d The upward shift of the band center indicates enhanced orbital hybridization between the Co site and the reaction intermediate, promoting the adsorption of oxygen-containing intermediates. According to... d Belt center theory, d The upward shift of the band center indicates that the Co site dThe orbital energy level is closer to the Fermi level, which will significantly enhance the orbital hybridization between the Co site and the oxygen-containing reaction intermediate, optimize the adsorption energy barrier of the intermediate at the active site, and thus reduce the overpotential of the oxygen evolution reaction.

[0061] Test 6: Performance testing and comparison of Sr atom-modified CoOOH nanosheets and CoOOH nanosheets and commercial ruthenium oxide catalyst in the oxygen evolution reaction at the anode of alkaline water electrolysis.

[0062] The Sr-modified CoOOH nanosheets and CoOOH nanosheets prepared in Examples 1 and 2, along with a commercial ruthenium oxide catalyst, were used as working electrodes, and their catalytic activity in the alkaline water electrolysis anodic oxygen evolution reaction was determined in an oxygen-saturated potassium hydroxide electrolyte. The linear scan curves obtained at a rotation speed of 1600 rpm and a scan rate of 5 mV / s are shown below. Figure 7 As shown. At a current density of 10 mA / cm². 2 At an overpotential of only 257 mV, the Sr-modified CoOOH nanosheet electrocatalyst was 31 mV lower than that of the commercial ruthenium oxide catalyst and 50 mV lower than that of the commercial ruthenium oxide catalyst. Simultaneously, at an overpotential of 300 mV, the current density of the Sr-modified CoOOH nanosheet catalyst was 8.07 times higher than that of the commercial ruthenium oxide catalyst, demonstrating the excellent catalytic activity of the Sr-modified CoOOH nanosheets in the alkaline water electrolysis anodic oxygen evolution reaction. Furthermore, as... Figure 8 As shown, during the alkaline water electrolysis anodic oxygen evolution reaction of 3000 accelerated cycles, the overpotential of the Sr atom-modified CoOOH nanosheet catalyst hardly changed, demonstrating excellent durability.

[0063] Test 7: Performance testing and comparison of Sr atom-modified CoOOH nanosheets in anion exchange membrane water electrolysis hydrogen production system.

[0064] The Sr-modified CoOOH nanosheet catalyst prepared in Example 1 was used as the working electrode, and its electrocatalytic performance in an anion exchange membrane water electrolysis hydrogen production system was tested in potassium hydroxide solution. The obtained linear sweep curve is shown below. Figure 9 As shown, at 2A / cm 2 At this voltage, it is only 1.84V, significantly better than the commercial catalyst ruthenium oxide. Furthermore, as... Figure 10 As shown, at a current density of 500 mA / cm² 2After 60 hours of stability testing, the Sr-modified CoOOH nanosheet catalyst exhibited a decay rate of only 0.87 mV / h, demonstrating excellent catalytic stability in the anion exchange membrane water electrolysis hydrogen production system. Therefore, the obtained Sr-modified CoOOH nanosheet catalyst exhibits outstanding catalytic performance in the oxygen evolution reaction at the anolyte of anion exchange membrane water electrolysis hydrogen production, and possesses broad prospects for industrial application.

[0065] In summary, this invention successfully constructed a Sr-modified CoOOH catalyst with a unique electronic structure by introducing Sr atoms into the CoOOH lattice. This catalyst utilizes the precise modulation of the electronic environment of the Co sites by Sr atoms to achieve a reduction in the electron cloud density around Co. d The synergistic optimization mechanism of upward shift of the band center and enhanced covalentity improves the activity of the alkaline oxygen evolution reaction.

[0066] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A Sr atom-modified CoOOH nanosheet catalyst, characterized in that, The nanosheet catalyst contains a CoOOH active phase modified with Sr atoms and has a two-dimensional nanosheet structure; wherein, the Sr atoms are modified in the CoOOH lattice, which reduces the electron cloud density of the Co sites and shifts the d-band center toward the Fermi level.

2. The Sr atom-modified CoOOH nanosheet catalyst according to claim 1, characterized in that, At a current density of 10 mA / cm², the overpotential of the Sr atom-modified CoOOH nanosheet catalyst is no higher than 257 mV; And / or, during 3000 accelerated cycles of alkaline water electrolysis for oxygen evolution, the overpotential of the Sr atom-modified CoOOH nanosheet catalyst does not decay.

3. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 1 or 2, characterized in that, include: It provides cobalt-containing precursors, strontium sources, and sulfur sources; Based on the cobalt-containing precursor, strontium source, and sulfur source, an Sr-doped cobalt sulfide precursor was prepared. The Sr-doped cobalt sulfide precursor was placed in an alkaline electrolyte and subjected to in-situ electrochemical reconstruction under oxygen evolution reaction conditions to obtain an Sr atom-modified CoOOH nanosheet catalyst.

4. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 3, characterized in that, The ratio of the total molar amount of the cobalt salt and strontium source to the molar amount of the sulfur source is 1:(1~2). The molar ratio of the strontium source to the cobalt salt is (0.001~1):

1.

5. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 3, characterized in that, The cobalt-containing precursor is ZIF-67, which is prepared by cobalt salt and organic ligand.

6. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 4, characterized in that, The preparation of Sr-doped cobalt sulfide precursors specifically includes: The ZIF-67, strontium source, and sulfur source were dispersed in a solvent and subjected to a solvothermal reaction at 120℃~150℃ for 5h~10h.

7. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 3, characterized in that, The alkaline electrolyte is a potassium hydroxide or sodium hydroxide solution.

8. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 3, characterized in that, The voltage range for the in-situ electrochemical reconstruction is (0-1.2)V~(1.4-2.0)V vs. RHE, and the scan rate is 1mV / s~1000mV / s.

9. The method for preparing the Sr atom-modified CoOOH nanosheet catalyst according to claim 3, characterized in that, The cobalt-containing precursor is prepared from a cobalt salt, which is selected from cobalt acetate, cobalt nitrate, cobalt chloride, cobalt sulfate, or cobalt acetylacetonate. The strontium source is selected from at least one of strontium acetate, strontium nitrate, strontium chloride, and strontium acetylacetone; The sulfur source is selected from at least one of N,N-dimethylthioacetamide, thioacetamide, thiobenzamide, and thiopropionamide.

10. The application of the Sr atom-modified CoOOH nanosheet catalyst according to claim 1 or 2 in the hydrogen production and oxygen evolution reaction of water electrolysis via anion exchange membrane.

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