Precursor for preparing ruthenium-based catalyst, ruthenium-based catalyst as well as preparation method and application of ruthenium-based catalyst

Abstract

The invention belongs to the technical field of electrolyzed water materials, and discloses a preparation method and application of a precursor for preparing a catalyst and a preparation method and application of the catalyst. According to the precursor, hydrogen atoms on hydroxyl in cyclodextrin molecules are substituted by R groups, polyphenol structures in the R groups and metal ruthenium form a coordination structure, and the number of the R groups in the cyclodextrin molecules is 1-7. According to the precursor for preparing the ruthenium-based catalyst, the ruthenium-based catalyst and the preparation method and application of the ruthenium-based catalyst, the coordination environment of Ru in the precursor is regulated and controlled, and a hydrogen evolution catalyst obtained after pyrolysis of the prepared precursor has high HER activity and stable performance.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis materials technology, and particularly relates to a method for preparing a precursor for a catalyst and its application, as well as a method for preparing and applying a catalyst. Background Technology

[0002] Hydrogen energy is an ideal clean energy source to replace traditional fossil fuels. Compared with traditional hydrogen production technologies, water electrolysis for hydrogen production has advantages such as high hydrogen purity and environmentally friendly, pollution-free processes, making it highly promising. However, the hydrogen evolution reaction (HER) faces problems such as high cost and low efficiency in practical applications. Developing highly active and stable catalysts is key to its large-scale application. Currently, platinum (Pt)-based catalysts are widely used in the HER due to their excellent catalytic performance. However, Pt-based catalysts suffer from high cost, resource scarcity, and insufficient stability during long-term operation, limiting their large-scale application. In recent years, ruthenium (Ru)-based catalysts, also a precious metal, have attracted widespread attention due to their similar activity to Pt and their greater price advantage. However, the strong binding force between Ru and OH and H species can lead to the occupation of Ru's active sites, thereby reducing the HER activity of the catalyst. Therefore, how to regulate the catalytic activity of Ru-based catalysts has become a key research focus. Summary of the Invention

[0003] To overcome the problems in the prior art, the present invention provides a precursor for preparing ruthenium-based catalysts, ruthenium-based catalysts, preparation methods and applications thereof. By regulating the coordination environment of Ru in the precursor, the precursor prepared is pyrolyzed to obtain a hydrogen evolution catalyst with high HER activity and stable performance.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0005] This invention provides a precursor for preparing ruthenium-based catalysts. The precursor is a cyclodextrin molecule in which the hydrogen atom on the hydroxyl group is replaced by an R group. The R group is shown below, wherein the polyphenolic structure in the R group forms a coordination structure with metallic ruthenium, and the number of R groups in the cyclodextrin molecule is 1 to 7.

[0006] As an optional implementation, in the precursor provided by the present invention, the schematic diagram of the coordination structure between the polyphenol structure and the metallic ruthenium in the precursor is shown in the following formula (1), wherein... Represents the metal ruthenium.

[0007] As an optional implementation, in the precursor provided by the present invention, the schematic diagram of the coordination structure between the polyphenol structure and the metallic ruthenium in the precursor is shown in the following formula (2), wherein... Represents the metal ruthenium.

[0008] As an optional implementation, in the precursor provided by the present invention, the schematic diagram of the coordination structure between the polyphenol structure and the metallic ruthenium in the precursor is shown in the following formula (3), wherein... Represents the metal ruthenium.

[0009] Based on the same technical concept, the present invention also provides a method for preparing a precursor for a ruthenium-based catalyst, comprising the following steps:

[0010] S1. Add carbonyl diimidazole to the cyclodextrin solution, and after the reaction, solution A1 is obtained;

[0011] S2. Triethylamine is added to the dopamine solution, and after mixing, it is added to solution A1. After the reaction, solution B1 is obtained.

[0012] S3. Add ruthenium salt to solution B1 obtained in step S2, precipitate the mixed solution in a buffer solution with pH 1 to 9, and obtain a precursor with polyphenol structure coordinated with metal ruthenium after treatment.

[0013] In this invention, cyclodextrin is used as the main molecular component. After reacting with carbonyl diimidazole and dopamine, a nitrogen-containing polyphenol structure is obtained. Then, ruthenium salt is added, and by controlling the pH of the buffer solution from 1 to 9, the coordination form between the polyphenol and Ru metal in the precursor is changed. Precursors with different coordination forms are obtained in buffer solutions with different pH values. Then, a series of Ru-based catalysts with different Ru–N coordination effects can be prepared by high-temperature pyrolysis.

[0014] The preparation principle of the nitrogen-containing polyphenol structure in this invention is as follows: Cyclodextrin is used as the main molecular component, and carbonyl diimidazole is used as an activator. The imidazole group combines with the oxygen atom of the hydroxyl group on the cyclodextrin to form an active ester intermediate. The amino group in dopamine attacks the carbonyl carbon atom in the active ester intermediate, undergoing a cyclization reaction to generate a five-membered ring structure.

[0015] As an optional implementation, in the method for preparing the precursor provided by the present invention, in step S3, when pH < 2, the schematic diagram of the coordination structure of the polyphenol structure and the metal ruthenium in the precursor is shown in formula (1).

[0016] When precipitating in a buffer solution with pH < 2, the coordination form of polyphenol and ruthenium metal in the obtained product is as shown in formula (1). The coordination effect is strong, and the catalyst exhibits extremely excellent HER activity.

[0017] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, in step S3, when 3 < pH < 6, the schematic diagram of the coordination structure between the polyphenol structure and ruthenium metal in the precursor is as shown in formula (2).

[0018] When precipitating in a buffer solution with 3 < pH < 6, the coordination form of polyphenol and ruthenium metal in the obtained product is as shown in formula (2). Compared with that in formula (2), although the coordination effect is slightly weakened, the catalytic effect is still strong.

[0019] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, in step S3, when pH > 7, the schematic diagram of the coordination structure between the polyphenol structure and ruthenium metal in the precursor is as shown in formula (3).

[0020] When precipitating in a buffer solution with 3 < pH < 6, the coordination form of polyphenol and ruthenium metal in the obtained product is as shown in formula (3). Compared with that in formula (2), although the coordination effect is weakened, it still has a certain catalytic effect, which is equivalent to the effect of 20% Pt / C.

[0021] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, the mass ratio of cyclodextrin, carbonyldiimidazole and dopamine is 1:3:3 to 1:7:7.

[0022] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, the treatment process in step S3 includes filtration, washing and drying.

[0023] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, the cyclodextrin is selected from one of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin.

[0024] Furthermore, it is preferably β-cyclodextrin.

[0025] As an alternative embodiment, in the preparation method of the precursor provided by the present invention, the buffer solution is selected from one or several of hydrochloric acid buffer solution, acetic acid buffer solution, phosphate buffer solution, 3-morpholinopropanesulfonic acid buffer solution.

[0026] Based on the same technical concept, the present invention also provides a ruthenium-based catalyst, which comprises a carbon skeleton having a three-dimensional porous structure and metallic ruthenium supported on the carbon skeleton. The metallic ruthenium is uniformly dispersed on the surface of the nitrogen-doped carbon skeleton and embedded in the interior of the carbon skeleton. The particle size of the metallic ruthenium is 5.77 nm to 13.19 nm. The coordination number of Ru-N in the ruthenium-based catalyst is 1.0 to 2.0.

[0027] As an optional implementation, in the ruthenium-based catalyst provided by the present invention, the specific surface area of ​​the catalyst is 300 m². 2 g -1 ~440m 2 g -1 ,

[0028] As an optional implementation, in the ruthenium-based catalyst provided by the present invention, the pore volume of the catalyst is 0.1 cm³. 3 g -1 ~0.2cm 3 g -1 The pore size is 1.1nm to 1.8nm.

[0029] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned ruthenium-based catalyst, comprising the following steps:

[0030] S1. Add carbonyl diimidazole to the cyclodextrin solution, and after the reaction, solution A1 is obtained;

[0031] S2. Triethylamine is added to the dopamine solution, and after mixing, it is added to solution A1. After the reaction, solution B1 is obtained.

[0032] S3. Add ruthenium salt to solution B1 obtained in step S2, precipitate the mixed solution in a buffer solution with pH 1 to 9, and obtain a precursor of phenolic structural unit coordinated with metallic ruthenium after treatment.

[0033] S4. The precursor is pyrolyzed under an inert atmosphere to prepare the hydrogen evolution catalyst.

[0034] As an optional implementation, in the preparation method of the ruthenium-based catalyst provided by the present invention, in step S4, the heating rate during the pyrolysis process is 1℃ / min to 20℃ / min, the pyrolysis temperature is 400℃ to 800℃, and the pyrolysis time is 1h to 8h.

[0035] As an optional implementation, in the method for preparing the ruthenium-based catalyst provided by the present invention, the inert gas is selected from one or both of argon and nitrogen.

[0036] Based on the same technical concept, the present invention also provides the application of the above-described precursor or the precursor obtained by the above-described preparation method in the hydrolysis to produce hydrogen.

[0037] Based on the same technical concept, the present invention also provides the application of the above-described catalyst or the catalyst obtained by the above-described preparation method in the hydrolysis to produce hydrogen.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) In this invention, a precursor particularly suitable for preparing hydrogen evolution catalysts is prepared. By introducing single atoms and ruthenium into the precursor, the Ru–N coordination effect is utilized to adjust the electronic structure of the Ru active center, change the position of the catalyst d-band center, and optimize the adsorption energy of H*. The hydrogen evolution catalyst prepared by pyrolysis of the precursor can promote the desorption of H2 in the HER process and accelerate the HER reaction rate.

[0040] (2) The present invention prepares hydrogen evolution catalysts by pyrolysis of precursors. Utilizing metal-polyphenol interaction, cyclodextrin is used as the molecular host. By introducing nitrogen atoms and ruthenium into the cyclodextrin molecule, the prepared catalysts all exhibit HER activity superior to Pt / C in alkaline medium.

[0041] (3) The unique molecular structure of cyclodextrin in this invention can further accelerate the mass transfer efficiency of the HER process and enhance HER activity by generating a large specific surface area and abundant pore structure after pyrolysis. Attached Figure Description

[0042] 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.

[0043] Figure 1 This is a schematic diagram of the reaction of the precursor prepared in Example 1;

[0044] Figure 2 The scanning electron microscope (SEM) and transmission electron microscope (TEM) results of the catalysts Bis-Ru@CN, Tris-Ru@CN, and Mono-Ru@CN prepared in Example 1 are shown in Figure ac, where the SEM results are shown in Figure df, the TEM results of the samples in Examples 1-3 are shown in Figure g, and the EDX image of Mono-Ru@CN is shown in Figure g.

[0045] Figure 3The XRD results are for the catalysts Bis-Ru@CN, Tris-Ru@CN, and Mono-Ru@CN prepared in Example 1.

[0046] Figure 4 The N2 isotherm adsorption-desorption curves (a) and BET detection results (b) of the catalysts Bis-Ru@CN, Tris-Ru@CN and Mono-Ru@CN prepared in Example 1 are shown.

[0047] Figure 5 The EXAFS spectra of the catalysts Bis-Ru@CN, Tris-Ru@CN and Mono-Ru@CN prepared in Example 1 are obtained by Fourier transform, where (a) is the EXAFS curve of Mono-Ru@CN, Bis-Ru@CN and Tris-Ru@CN, and (b) is the Ru-N coordination number obtained by fitting the EXAFS curve of each sample.

[0048] Figure 6 The CV curves and electrochemical active areas of the catalysts Bis-Ru@CN, Tris-Ru@CN, and Mono-Ru@CN prepared in Example 1 at different scan rates are shown in Figure ac, which shows the CV curves of each sample, and Figure d shows the electrochemical active area calculated from the CV curves.

[0049] Figure 7 The electrochemical impedance spectroscopy and stability results of the catalysts Bis-Ru@CN, Tris-Ru@CN and Mono-Ru@CN prepared in Example 1 are shown in Figure a. Figure a shows the electrochemical impedance spectra of each sample, and Figure b shows the LSV curves of Mono-Ru@CN before and after 10,000 CV cycles.

[0050] Figure 8 The results of the total water splitting performance of the catalyst MonoRu@CN prepared in Example 1 under alkaline conditions are shown in (a) the LSV curve of Mono-Ru@CN, the inset is a diagram of the hydrogen production test device for water electrolysis, (b) the hydrogen production diagram, and (c) the stability test curve of Mono-Ru@CN.

[0051] Figure 9 The electrochemical active area and electrochemical impedance spectroscopy results of the catalysts Bis-Ru@CN, Tris-Ru@CN and Mono-Ru@CN prepared in Example 1 in acidic solution are shown in Figure (a), where (b) is the electrochemical active area and (a) is the electrochemical impedance spectrum. Detailed Implementation

[0052] To facilitate understanding of the present invention, the present 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] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0054] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0055] Example 1

[0056] A method for preparing a ruthenium-based catalyst includes the following steps:

[0057] (1) Dissolve 0.5 mM β-cyclodextrin and 2.5 mM 1,1-carbonyldiimidazole (CDI) in 8 mL of N,N-dimethylformamide, dissolve rapidly by sonication, and then place the solution in the dark and react under ice bath conditions for 8 h to 10 h to obtain solution A.

[0058] (3) Dissolve 2.5 mM dopamine hydrochloride (DA) in 5 mL of N,N-dimethylformamide, then add 700 μL of triethylamine (TEA), shake and react at 25 °C for 5 min, filter, add the filtrate to the solution obtained in (1), and continue stirring and reacting for 8 h under the same conditions to obtain solution B, which is a polyphenol structure. The synthesis circuit diagram is as follows. Figure 1 As shown.

[0059] (3) Add 0.75 mM RuCl3 to the reaction solution obtained in (2), and precipitate the mixture in buffer solutions with pH=1, pH=5 and pH=9 respectively to obtain precursors with different coordination forms, which are named Mono-Ru, Bis-Ru and Tris-Ru respectively.

[0060] (4) The precursor was pyrolyzed at 800℃ for 4 h under an argon atmosphere at a heating rate of 5℃ / min to obtain ruthenium-based catalysts with different coordination forms. They were named Bis-Ru@CN, Tris-Ru@CN, and Mono-Ru@CN.

[0061] Example 2

[0062] A method for preparing a ruthenium-based catalyst includes the following steps:

[0063] (1) Dissolve 0.5 mM β-cyclodextrin and 1.5 mM 1,1-carbonyldiimidazole (CDI) in 8 mL of N,N-dimethylformamide, dissolve rapidly by sonication, and then place the solution in the dark and react under ice bath conditions for 8 h to 10 h to obtain solution A.

[0064] (2) Dissolve 1.5 mM dopamine hydrochloride (DA) in 5 mL of N,N-dimethylformamide, then add 700 μL of triethylamine (TEA), shake and react at 25 °C for 5 min, filter, add the filtrate to the solution obtained in (1), and continue stirring and reacting for 8 h under the same conditions to obtain solution B.

[0065] (3) Add 0.75 mM RuCl3 to the reaction solution obtained in (2), and precipitate the mixture in a buffer solution with pH=1 to obtain the precursor.

[0066] (4) The precursor was pyrolyzed at 800℃ for 4 h under an argon atmosphere at a heating rate of 5℃ / min to obtain ruthenium-based catalysts with different coordination forms. The prepared catalysts were named Ru@C-1 (degree of substitution 1, number of branches 1).

[0067] Example 3

[0068] A method for preparing a ruthenium-based catalyst includes the following steps:

[0069] (1) Dissolve 0.5 mM β-cyclodextrin and 3.5 mM 1,1-carbonyldiimidazole (CDI) in 8 mL of N,N-dimethylformamide, dissolve rapidly by sonication, and then place the solution in the dark and react under ice bath conditions for 8 h to 10 h to obtain solution A.

[0070] (2) Dissolve 3.5 mM dopamine hydrochloride (DA) in 5 mL of N,N-dimethylformamide, then add 700 μL of triethylamine (TEA), shake and react at 25 °C for 5 min, filter, add the filtrate to the solution obtained in (1), and continue stirring and reacting for 8 h under the same conditions to obtain solution B.

[0071] (3) Add 0.75 mM RuCl3 to the reaction solution obtained in (2), and precipitate the mixture in a buffer solution with pH=1 to obtain the precursor.

[0072] (4) The precursor was pyrolyzed at 800℃ for 4 h under an argon atmosphere at a heating rate of 5℃ / min to obtain ruthenium-based catalysts with different coordination forms. The prepared catalysts were named Ru@C-5 (degree of substitution 5, number of branches 5).

[0073] Example 4

[0074] The difference from Example 1 is that in step (1), β-cyclodextrin is replaced with α-cyclodextrin, and in step (4), the mixture is precipitated in a buffer solution with pH=1. The rest is the same as in Example 1. The catalyst prepared is named α-Ru@CN.

[0075] Example 5

[0076] The difference from Example 1 is that in step (1), β-cyclodextrin is replaced with γ-cyclodextrin, and in step (4), the mixture is precipitated in a buffer solution with pH=1. The rest is the same as in Example 1. The prepared catalyst is named γ-Ru@CN.

[0077] Comparative Example 1 (No Metal)

[0078] (1) Dissolve 0.5 mM β-cyclodextrin and 2.5 mM 1,1-carbonyldiimidazole (CDI) in 8 mL of N,N-dimethylformamide, dissolve rapidly by sonication, and then place the solution in the dark and react under ice bath conditions for 8 h to 10 h to obtain solution A.

[0079] (2) Dissolve 2.5 mM dopamine hydrochloride (DA) in 5 mL of N,N-dimethylformamide, then add 700 μL of triethylamine (TEA), shake the reaction at 25 °C for 5 min, filter, add the filtrate to the solution obtained in (1), and continue stirring the reaction for 8 h under the same conditions to obtain solution B.

[0080] (3) Add solution B to acetone to precipitate, and then filter, wash and dry to obtain pure cyclodextrin-polyphenol compound (CC).

[0081] Comparative Example 2

[0082] The difference from Example 1 is that β-cyclodextrin is replaced with maltose; otherwise, it is the same as in Example 1. The prepared catalyst is named M-Ru@CN.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that in step (4), the mixture is precipitated in a buffer solution with pH=10, otherwise it is the same as in Example 1.

[0085] Comparative Example 4

[0086] (1) Dissolve 0.5 mM ruthenium acetylacetonate and 0.5 mM β-cyclodextrin in 8 mL of N,N-dimethylformamide and stir at 25 °C for 24 h.

[0087] (2) Add the solution obtained in (1) to acetone to precipitate, filter and wash, and dry at 80°C for 8 hours to obtain the precursor.

[0088] (3) The precursor obtained in (2) is pyrolyzed at 800℃ for 4 hours under an argon atmosphere at a heating rate of 5℃ / min to obtain the catalyst. Structural characterization

[0089] The morphology and structure of the catalyst were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 2 As shown in figures a through 2c, the morphologies of all three catalysts are typical carbon-encapsulated nanoparticle structures. TEM observation further confirms this, as shown in... Figure 2 As shown in d~2f, compared to Bis-Ru@CN and Tris-Ru@CN, the Ru nanoparticles in Mono-Ru@CN are smaller, which may be due to stronger Ru-N coordination. The smaller nanoparticle size facilitates the exposure of more active sites, enhancing HER activity. Furthermore, as... Figure 2 As shown in g, energy-dispersive X-ray (EDX) spectroscopy confirmed that C, N, O, and Ru were uniformly distributed in Mono-Ru@CN, demonstrating that N heteroatoms were successfully introduced into the catalyst through cyclodextrin molecular design. The introduction of N is beneficial to enhancing the conductivity of the carbon support and regulating the electronic structure of the Ru active center, thereby improving the HER performance of the catalyst.

[0090] The structure of the catalyst was evaluated using XRD, such as Figure 3 As shown, all three catalysts exhibit a broad characteristic peak near 23.8°, similar to that of graphitic carbon, confirming that all three catalysts possess a graphitic carbon structure. Characteristic peaks also appear near 38.1°, 42.2°, 44.0°, 58.2°, 69.3°, and 78.3°, corresponding to the (100), (002), (101), (102), (110), and (103) crystal planes of the Ru metallic phase (PDF#06–0663), respectively, demonstrating that Ru nanoparticles in the catalysts primarily exist in metallic form. The broader characteristic peak of Mono-Ru@CN indicates smaller nanoparticle size, consistent with TEM observations.

[0091] Taking Mono-Ru@CN as an example, its specific surface area and pore structure were investigated. Figure 4 As shown in Figures a and 4b, the nitrogen adsorption-desorption isotherms and Brunauer–Emmett–Teller (BET) calculations indicate that the specific surface area of ​​Mono-Ru@CN is 288.44 m². 2 g -1 The pore volume and average pore diameter are 0.17 cm. 3 g -1And 5.28 nm. The larger specific surface area and abundant pore structure will facilitate electrolyte permeation, improve the mass transfer efficiency of the HER process, and also facilitate the exposure of active sites, thereby enhancing HER activity.

[0092] The EXAFS spectrum obtained by Fourier transform is as follows Figure 5 a shows that the three catalysts in A distinct sharp peak appears on both sides, corresponding to the characteristic peak of Ru-Ru coordination, proving that all three catalysts formed ruthenium nanoparticles, consistent with the XRD and TEM results. Furthermore, the three catalysts... A peak also appeared on both sides, corresponding to Ru–N coordination, proving that there is coordination interaction between Ru atoms and N atoms in all three catalysts. The fitting data results for the three catalysts are as follows: Figure 5 As shown in b and Table 1, the coordination number of Ru–N in Mono-Ru@CN is 1.9, which is higher than that of Bis-Ru@CN (1.0) and Tris-Ru@CN (1.24). This indicates that Ru and N have stronger electronic interactions in Mono-Ru@CN. Stronger electronic interactions are beneficial to optimizing the electronic structure of the Ru active center, thereby improving the HER activity of the catalyst. Table 1: EXAFS curve fitting data for Mono-Ru@CN, Bis-Ru@CN, and Tris-Ru@CN Performance Characterization

[0093] The hydrogen evolution catalyst prepared in the examples was subjected to a three-electrode system hydrogen evolution reaction (HER) performance test, and the test method is as follows:

[0094] Electrocatalyst slurry preparation: Weigh 0.5 mg of catalyst and add it to a mixed solution (ethanol, water, and Nafion volumes are 480, 480, and 40 μL, respectively), and ultrasonically disperse it evenly at 20 °C to obtain electrocatalyst ink.

[0095] The working electrode is a glassy carbon electrode with a catalyst supported (3 mm in diameter), the reference electrode is an Ag|AgCl electrode, the counter electrode is a carbon rod, and the electrolyte solution is a 1.0 M KOH or 0.5 M H2SO4 solution.

[0096] The test potential range is -0.8 to -1.6V, and the scan rate is 10mV / s.

[0097] 5 μL of catalyst ink was dropped onto the surface of the glassy carbon electrode and allowed to air dry before testing. The HER performance is shown in Table 2. Table 2: Three-electrode HER performance

[0098] As shown in Table 2, the catalyst prepared by this invention has a better overpotential than 20% Pt / C under both acidic and alkaline conditions at the same current density, and has broad application prospects.

[0099] Performance testing in alkaline electrolysis

[0100] To evaluate the intrinsic activity of the catalyst, the electrochemical active area in the 1M KOH electrolyte was measured using the electrochemical double-layer capacitance method. The CV curves of Mono-Ru@CN, Bis-Ru@CN, and Tris-Ru@CN at different scan rates are shown below. Figure 6 As shown in a–6c. The calculated active area is as follows. Figure 6 As shown in d, the active area of ​​Mono-Ru@CN is 88.61 mFcm. -2 Higher than Bis-Ru@CN (42.03mF cm) -2 ) and Tris-Ru@CN(53.01mF cm -2 The Ru–N coordination interaction was enhanced, which showed stronger HER activity. This indicates that the enhanced Ru–N coordination interaction is beneficial to improving the intrinsic activity of the catalyst. Furthermore, the large specific surface area and abundant pore structure of the carbon support can expose more active sites and enhance the transport rate of reaction intermediates, thereby further improving HER activity.

[0101] Electrochemical impedance spectroscopy was used to assess the charge transfer behavior of catalysts, such as... Figure 7 As shown in Figure a, the semi-circular radius of Mono-Ru@CN is smaller than that of Bis-Ru@CN and Tris-Ru@CN, indicating that it has the lowest charge transfer impedance, faster charge transport capability, and higher catalytic activity. Besides high activity, catalysts also need high stability. Long-term operational stability is another key criterion for evaluating the practical application potential of catalysts. Therefore, cycle durability tests were also conducted on MonoRu@CN, such as... Figure 7 As shown in b, the LSV polarization curve of Mono-Ru@CN almost overlaps with the initial curve after 10,000 CV cycles, indicating that it has excellent stability. The excellent stability of Mono-Ru@CN can be attributed to the strong coordination between Ru and N, which prevents it from dissolving and deactivating during the catalytic process.

[0102] Based on the excellent HER performance exhibited by Mono-Ru@CN in a three-electrode system, the overall water splitting performance of MonoRu@CN under alkaline conditions was investigated in depth. For example... Figure 8As shown in Figure a, the water-splitting activity of the catalyst was investigated using an H-cell, with Mono-Ru@CN (loaded onto nickel foam) and nickel foam used as the cathode and anode for water splitting, respectively. Figure 8 As shown in Figure a, Mono-Ru@CN only requires 1.96V to achieve 10mA / cm. -2 The current density exhibited excellent water-splitting activity. Furthermore, the hydrogen production rate of MonoRu@CN was tested. Figure 8 As shown in b, it produced 49 mL of hydrogen and 24 mL of oxygen within 20 min, exhibiting extremely high water-splitting activity. Furthermore, the long-term stability of Mono-Ru@CN water-splitting was tested, such as... Figure 8 As shown in c, at 10mAcm -2 Stability tests were conducted at a current density of [value missing]. After 12 hours, the current only slightly decreased, and its retention rate remained close to 100%, demonstrating extremely high stability. This indicates that Mono-Ru@CN has great potential for practical applications.

[0103] Performance testing in acidic solutions

[0104] To evaluate the intrinsic activity of the catalysts, the electrochemical active areas of the three catalysts were measured. For example... Figure 9 As shown in figure a, the active surface area of ​​Mono-Ru@CN is 42.81 mF cm⁻¹. -2 Greater than Bis-Ru@CN(33.44mF cm) -2 ) and Tris-Ru@CN(33.06mF cm -2 This indicates a stronger intrinsic activity. Electrochemical impedance spectroscopy was used to assess the charge transfer behavior of the catalyst, such as... Figure 9 As shown in b, the semi-circular radius of Mono-Ru@CN is smaller than that of BisRu@CN and Tris-Ru@CN, indicating that it has the lowest charge transfer impedance, faster charge transport capability, and higher catalytic activity. These results demonstrate that Mono-Ru@CN exhibits excellent HER activity and stability in both acidic and alkaline solutions, showing broad potential for practical applications.

[0105] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A precursor for preparing a ruthenium-based catalyst, characterized in that, The precursor is that the hydrogen atoms on the hydroxyl groups in the cyclodextrin molecule are replaced by R groups. The R groups are shown as follows. The polyphenol structure in the R groups forms a coordination structure with ruthenium metal. The number of R groups in the cyclodextrin molecule is 1 to 7.

2. The precursor for preparing a ruthenium-based catalyst according to claim 1, characterized in that, The schematic diagram of the coordination structure between the polyphenol structure and ruthenium in the precursor is shown in equation (1-3) below, where Represents the metal ruthenium.

3. A method for preparing a precursor for a ruthenium-based catalyst, characterized in that, It includes the following steps: S1. Add carbonyldiimidazole to the cyclodextrin solution, and after reaction, obtain solution A1. S2. Add triethylamine to the dopamine solution, mix and then add it to solution A1, and after reaction, obtain solution B1. S3. Add a ruthenium salt to the solution B1 obtained in step S2, precipitate the mixed solution in a buffer solution with a pH of 1 to 9, and after treatment, obtain a precursor in which the polyphenol structure is coordinated with ruthenium metal.

4. The preparation method according to claim 3, characterized in that, In step S3, when pH < 2, the schematic diagram of the coordination structure between the polyphenol structure and ruthenium metal in the precursor is shown in formula (1); when 3 < pH < 6, the schematic diagram of the coordination structure between the polyphenol structure and ruthenium metal in the precursor is shown in formula (2); when pH > 7, the schematic diagram of the coordination structure between the polyphenol structure and ruthenium metal in the precursor is shown in formula (3).

5. The preparation method according to claim 3, characterized in that, The mass ratio of the cyclodextrin, carbonyldiimidazole and dopamine is 1:3:3 to 1:7:7; the cyclodextrin is selected from one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; the buffer solution is selected from one or several of hydrochloric acid buffer solution, acetic acid buffer solution, phosphate buffer solution or 3-morpholinopropanesulfonic acid buffer solution.

6. A ruthenium-based catalyst, characterized in that, The ruthenium-based catalyst comprises a carbon framework with a three-dimensional porous structure and metallic ruthenium supported on the carbon framework. The metallic ruthenium is uniformly dispersed on the surface of the nitrogen-doped carbon framework and embedded within the carbon framework. The particle size of the metallic ruthenium is 5.77 nm to 13.19 nm. The coordination number of Ru-N in the ruthenium-based catalyst is 1.0 to 2.

0. The specific surface area of ​​the catalyst is 300.0 m². 2 g -1 ~440.5m 2 g -1 The catalyst has a pore volume of 0.10 cm³. 3 g -1 ~0.20cm 3 g -1 The pore size is 1.10 nm to 1.81 nm.

7. A method for preparing a ruthenium-based catalyst as described in any one of claims 6, characterized in that, It includes the following steps: S1. Add carbonyldiimidazole to the cyclodextrin solution, and after reaction, obtain solution A1. S2. Add triethylamine to the dopamine solution, mix and then add it to solution A1, and after reaction, obtain solution B1. S3. Add a ruthenium salt to the solution B1 obtained in step S2, precipitate the mixed solution in a buffer solution with a pH of 1 to 9, and after treatment, obtain a precursor in which the phenolic structural unit is coordinated with ruthenium metal. S4. Pyrolyze the precursor under an inert atmosphere to prepare a hydrogen evolution catalyst.

8. The method for preparing the ruthenium-based catalyst according to claim 7, characterized in that, In step S4, the heating rate during the pyrolysis process is 1 °C / min to 20 °C / min, the pyrolysis temperature is 400 °C to 800 °C, and the pyrolysis time is 1 h to 8 h.

9. Application of a precursor as described in any one of claims 1-2 or a precursor obtained by the preparation method as described in any one of claims 3-5 in hydrolyzing to prepare hydrogen.

10. Application of a catalyst as described in any one of claims 6 or a catalyst obtained by the preparation method as described in claim 7 or 8 in hydrolyzing to prepare hydrogen.

Images