A ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, its preparation method and application

Abstract

The present invention discloses a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, its preparation method and application, which relates to the technical field of electrocatalysts. The preparation method is as follows: Weigh cobalt salt and trimesic acid and dissolve them together in a methanol solution. After a first ultrasonic mixing treatment, a mixed solution A is obtained; Drop the methanol solution containing ruthenium salt into the mixed solution A. After a second ultrasonic mixing treatment, a mixed solution B is obtained. The mixed solution B is subjected to a hydrothermal reaction to obtain a ruthenium-cobalt metal-organic framework precursor; The ruthenium-cobalt metal-organic framework precursor is subjected to a calcination treatment. Compared with the prior art, the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared by the present invention exhibits excellent hydrogen evolution electrocatalytic activity and stability in the alkaline water electrolysis reaction. The performance of this catalyst is superior to that of commercial platinum-carbon catalysts, and it can maintain a stable potential output during continuous testing for 100 hours without obvious attenuation.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and particularly to a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Compared with the traditional fossil fuel-based hydrogen production methods, the water electrolysis hydrogen production technology stands out due to its unique advantages. From the perspective of raw materials, the raw material water for water electrolysis hydrogen production is extremely widespread, not restricted by resource scarcity, providing a solid foundation for continuous and stable hydrogen production; in terms of product quality, the produced hydrogen has extremely high purity, meeting the requirements of application scenarios with strict hydrogen quality requirements such as high-end electronics and fine chemicals. In addition, the water electrolysis hydrogen production process has the characteristics of simple process and mild reaction conditions, and no harmful substances polluting the environment are generated during the entire preparation process, fully conforming to the concept of green environmental protection, and is an ideal way to achieve green and sustainable hydrogen production. Currently, proton exchange membrane water electrolysis (PEM) technology and anion exchange membrane water electrolysis (AEM) technology are both common water electrolysis hydrogen production technology routes. Among them, compared with proton exchange membrane technology, the latter has higher requirements for material corrosion resistance. However, it cannot be ignored that in the case of high current density and long-term operation conditions of the anion exchange membrane electrolytic cell, the catalyst activity will be significantly reduced, which seriously restricts the further popularization and application of AEM water electrolysis hydrogen production technology and the expansion of industrial scale.

[0003] Among various types of alkaline hydrogen evolution catalysts, noble metal platinum-based catalysts have developed into products with a relatively high technology maturity and a top-level commercialization degree among current cathode hydrogen evolution catalysts due to their extremely excellent corrosion resistance and catalytic activity. However, the market price of platinum metal is much higher than that of other noble metals such as ruthenium and palladium. The high cost has severely hindered the wide application of this platinum-based catalyst in the field of water electrolysis. Therefore, researchers have focused on finding alternative solutions for platinum-based catalysts, and a large number of research projects on using ruthenium-based catalysts with relatively lower costs to replace platinum-based catalysts have been successively launched and steadily promoted. For example, Chinese patent document with publication number CN119392292A discloses a ruthenium-based catalyst and its preparation method. First, ruthenium salt, germanium oxide, and sodium carbonate are ground in a mortar until evenly mixed. Then, the mixture is placed in a muffle furnace and heated to 550 °C at a heating rate of 3 °C / min, and kept at 550 °C for 5 hours, followed by natural cooling. Finally, the sample is pickled and washed with water to obtain a Ge-doped RuO2 product. Another example is Chinese patent document with publication number CN117187870A, which discloses a tungsten ruthenium oxide electrode catalyst, its preparation method, and application. First, ruthenium chloride, ammonium tungstate, zirconyl nitrate, and sodium nitrate are placed in an aqueous phase to obtain a mixed solution; then the mixed solution is rotary evaporated and dried to obtain a precursor powder. Subsequently, the precursor powder is put into a muffle furnace at 350 °C and kept warm for 30 min, taken out to obtain a molten salt mixture, and then washed with a large amount of deionized water to finally obtain a zirconium-modified tungsten ruthenium oxide catalyst product.

[0004] However, although the literature including the above-mentioned published patent texts shows that certain achievements have been made in the research work of ruthenium-based catalysts, among the currently reported ruthenium-based electrocatalysts, their hydrogen evolution activities generally decline to varying degrees, and there is a significant gap in catalytic activity compared with commercial platinum-carbon noble metal catalysts. Summary of the Invention

[0005] Aiming at the problem of low hydrogen evolution activity in ruthenium-based catalysts in the prior art, the present invention provides a preparation method of a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst. The prepared ruthenium-doped cobalt metal oxide nanosheet electrocatalyst exhibits excellent electrocatalytic activity in the cathodic hydrogen evolution reaction of alkaline water electrolysis and has good long-term working stability at the same time.

[0006] The present invention provides a preparation method of a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, and the preparation method specifically includes the following steps:

[0007] S1. Weigh cobalt salt and trimesic acid and dissolve them together in a methanol solution. After one ultrasonic mixing treatment, a mixed solution A is obtained;

[0008] S2. Drop the ruthenium salt-containing methanol solution into the mixed solution A obtained in step S1. After secondary ultrasonic mixing treatment, a mixed solution B is obtained. Subject the mixed solution B to a hydrothermal reaction to obtain a ruthenium-cobalt metal-organic framework precursor;

[0009] S3. Calcinate the ruthenium-cobalt metal-organic framework precursor obtained in step S2 to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0010] The synthesis principle of the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention is as follows: Under the high-temperature and high-pressure environment created by hydrothermal conditions, relying on the coordination between metal ions and ligands, a ruthenium-cobalt metal-organic framework precursor with a specific structure is gradually formed; Subsequently, under the conditions of calcination treatment, most cobalt ions form cobalt oxides, and a small part of ruthenium ions are doped into the cobalt metal oxide lattice during the calcination process, and finally a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst is obtained.

[0011] Furthermore, the preparation method disclosed in the present invention utilizes the metal-organic framework (MOF) precursor strategy to achieve uniform doping of ruthenium atoms in the cobalt oxide lattice, optimize the electronic structure and expose abundant active sites, significantly enhancing the alkaline hydrogen evolution reaction (HER) activity; The ultrathin porous structure of the nanosheets enhances the mass transfer efficiency and conductivity. At the same time, the ruthenium-cobalt synergistic effect and stable lattice doping inhibit the degradation of active components, endowing the catalyst with both high catalytic activity (low overpotential) and long-term stability.

[0012] In a possible implementation manner, in the step S1, the molar ratio of the cobalt salt to trimesic acid is 1:(2 - 5)

[0013] Compared with the prior art, the precise adoption of a specific molar ratio in the present invention has significant scientific basis and advantages. During the hydrothermal synthesis process, if the content of the cobalt salt is too low, only a small part of trimesic acid can coordinate with cobalt ions, making it difficult to form a cobalt metal-organic framework. When the content of the cobalt salt is too high, the concentration of cobalt ions in the solution increases significantly, and side reactions are likely to occur, generating cobalt metal hydroxide hydrates. The appearance of this by-product will interfere with the entire reaction process and have a significant negative impact on the formation of the final product, ruthenium-doped cobalt oxide, not only possibly causing disorder in the product structure but also seriously reducing its catalytic performance.

[0014] In a possible implementation manner, in the step S1, the cobalt salt is a soluble salt, and the type of the cobalt salt is selected from one of nitrates, chlorides, sulfates, hydrates of nitrates, hydrates of chlorides, and hydrates of sulfates.

[0015] Compared with the prior art, the advantages of selecting nitrate, chloride, sulfate or their hydrates as cobalt salts are as follows: Their high solubility ensures the uniform dispersion of cobalt ions in methanol, laying a foundation for the formation of a structurally stable ruthenium-cobalt metal-organic framework (MOF) precursor; during calcination, anions (such as nitrate, chloride, sulfate) can decompose into gases and escape, reducing impurity residues and ensuring the high purity of the final product; anions with weak coordination ability avoid interfering with the coordination of organic ligands with cobalt ions and maintain the structural integrity of the precursor; at the same time, these salts are low-cost and easily available, and the hydrate form is more soluble and easier to operate, which is conducive to the efficient preparation of highly active and uniformly shaped ruthenium-doped cobalt oxide nanosheet electrocatalysts.

[0016] In a possible implementation manner, in the step S1, in the methanol solution, the volume ratio of deionized water to methanol is 1:(1 - 10).

[0017] Compared with the prior art, using a mixed solution of deionized water and methanol as the reaction solvent, and the present invention limits the ratio of deionized water to methanol within the above range, the advantages are as follows: Different selections of solvents during the hydrothermal reaction process will have an obvious impact on the microscopic morphology of the product. In order to obtain the target nanosheet structure, a mixed solution of deionized water and methanol is selected as the reaction solvent.

[0018] In a possible implementation manner, in the step S2, in the methanol solution containing ruthenium salt: the concentration of ruthenium salt is 5 - 15 mg / mL.

[0019] Compared with the prior art, the present invention uses ruthenium salts with the above concentrations and mass ratios because: when the content of ruthenium salt is too high, it will affect the coordination between cobalt metal ions and trimesic acid, which is not conducive to the formation of cobalt metal-organic frameworks. When the content of ruthenium salt is too low, it will affect the chelation between ruthenium metal ions and trimesic acid, resulting in too low ruthenium content in the final product and a decrease in catalytic activity.

[0020] In a possible implementation manner, in the step S2, the type of ruthenium salt is selected from one of chloride, ruthenate, hydrate of chloride, and hydrate of ruthenate.

[0021] Compared with the prior art, the advantages of the present invention in selecting ruthenium salts as chlorides, ruthenates or their hydrates are as follows: Their good solubility in methanol ensures the uniform dispersion of ruthenium ions and synergistically forms a stable metal-organic framework precursor with cobalt salts; during the calcination process, chloride ions or ruthenate ions can decompose into volatile gases, reducing impurity residues and improving the purity of ruthenium-doped cobalt oxide; anions with weak coordination avoid competing for coordination with organic ligands and maintain the structural stability of the precursor; at the same time, such ruthenium salts are easily available and the hydrate form is more soluble, which is conducive to accurately controlling the doping ratio and forming highly active nanosheet electrocatalysts.

[0022] In a possible implementation, in the step S2, the hydrothermal reaction is carried out in a high-pressure hydrothermal reactor, and the parameters of the hydrothermal reaction are as follows: the temperature is 110 - 170 °C, and the time is 10 - 20 h.

[0023] Compared with the prior art, the present invention adopts the hydrothermal reaction with the above parameters. Under specific temperature and pressure conditions, it promotes the full coordination of metal ions and organic ligands, forming a ruthenium-cobalt metal-organic framework precursor with high crystallinity and stable structure. The controllable reaction time and thermokinetic environment are conducive to the directional growth and thickness control of nanosheets, ensuring uniform product morphology and large specific surface area. At the same time, the hydrothermal conditions accelerate the reaction process and optimize the atomic arrangement, providing an ideal precursor basis for the subsequent calcination to prepare a ruthenium-doped cobalt oxide electrocatalyst with high activity and high stability.

[0024] In a possible implementation, in the step S3, the parameters of the calcination treatment are as follows: the temperature is 350 - 550 °C, the heating rate is 1 - 5 °C / min, the atmosphere is air, and the time is 2 - 3 h.

[0025] Compared with the prior art, the present invention adopts the above parameters for the calcination treatment because: the mild heating rate combined with the appropriate temperature range ensures that the ruthenium-cobalt metal-organic framework precursor is gradually transformed into an oxide, avoiding structural collapse or excessive particle aggregation, and maintaining the nanosheet morphology; the air atmosphere promotes the full oxidation and decomposition of the organic ligand and the controllable oxidation of cobalt and ruthenium ions, forming a stable crystal phase and high-active sites; at the same time, the short-time calcination balances the optimization of crystallinity and specific surface area, and finally obtains a ruthenium-doped cobalt metal oxide nanosheet with uniform structure, good conductivity and excellent catalytic performance.

[0026] The second object of the present invention is to provide a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared by the above preparation method.

[0027] It is worth mentioning that the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared by the present invention can be represented by the chemical formula: Ru-Co3O4, where Ru- is ruthenium doping; Co3O4 is cobalt metal oxide. In the cobalt oxide nanosheet electrocatalyst prepared by the present invention, ruthenium doping can further accelerate the electron transfer between metal sites, optimize the adsorption energy of hydrogen intermediates during the hydrogen evolution reaction process, and enable the cobalt and ruthenium active sites to be in a highly active state for a long time.

[0028] The third object of the present invention is to provide an application of a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst as a working electrode in the hydrogen evolution reaction at the cathode of water electrolysis in an alkaline solution.

[0029] In the hydrogen evolution reaction at the cathode of acidic electrolyzed water, a three-electrode system is adopted. Specifically, a Hg / HgO electrode is used as the reference electrode, a carbon rod is used as the counter electrode, a glassy carbon electrode coated with the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention is used as the working electrode, and 1 M potassium hydroxide solution is used as the electrolyte.

[0030] The ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention consists of two parts: doped ruthenium and cobalt oxide. Cobalt tetroxide exhibits good electron transfer properties and is also beneficial to the stability of the overall structure during the reaction. At the same time, ruthenium is doped into the metal oxide, which is beneficial to the interaction between cobalt and the metal oxide substrate, further accelerating the electron transfer to improve the overall catalytic activity of the material.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention exhibits high hydrogen evolution electrocatalytic activity and stability during the alkaline electrolyzed water reaction. When the current density is 10 mA cm -2 , the anodic reaction overpotential is only about 20 mV, and it can maintain for 100 h without obvious potential change, further promoting the technical development of anion exchange membrane electrolyzed water for hydrogen production;

[0033] (2) The ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention optimizes the electronic environment of cobalt and ruthenium metal sites through ruthenium doping, improving the catalytic activity while ensuring the relative stability of the site valence state;

[0034] (3) The ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention can optimize the adsorption of active sites on water molecules and hydrogen intermediates by controlling the ruthenium doping ratio, which is beneficial to the subsequent hydrogen evolution reaction of electrolyzed water;

[0035] (4) The present invention is committed to developing a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst. By skillfully using cobalt atoms to precisely regulate the electronic structure of ruthenium sites, the hydrogen evolution activity of the catalyst can be effectively improved. The addition of cobalt metal oxide significantly reduces the ruthenium metal loading while opening up a new path for obtaining low-loading and high-activity ruthenium-based catalysts. This innovative research result has an important significance that cannot be ignored for promoting the progress of anion exchange membrane electrolyzed water for hydrogen production technology and is expected to inject new vitality into the development of this field. Description of the Drawings

[0036] Figure 1 It is the scanning electron microscope (SEM) image of the catalyst Ru-Co3O4 prepared in Example 1 of the present invention;

[0037] Figure 2 TEM image of the catalyst Ru-Co3O4 prepared in Example 1 of the present invention;

[0038] Figure 3 XRD pattern of the catalyst Ru-Co3O4 prepared in Example 1 of the present invention;

[0039] Figure 4 Polarization curves of glassy carbon coated with the catalyst prepared in Example 1 of the present invention, the catalyst prepared in Comparative Example 1, and Pt / C of Comparative Example 2 during the alkaline electrolytic water hydrogen evolution reaction in the application example;

[0040] Figure 5 Curve of voltage change with time under constant current during the alkaline electrolytic water hydrogen evolution reaction of the catalyst Ru-Co3O4 prepared in Example 1 of the present invention. Detailed Description of the Invention

[0041] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings.

[0042] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of this application are merely exemplary.

[0044] The following provides a more detailed description of the present application in conjunction with the accompanying drawings and specific embodiments.

[0045] Example 1: This example provides a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, which is prepared by the following preparation method:

[0046] S1. Weigh 149 mg of cobalt nitrate hexahydrate and 210 mg of trimesic acid, dissolve them in a methanol solution containing 20 mL of methanol and 2 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed;

[0047] S2. Drop the methanol solution of ruthenium chloride with a concentration of 10 mg / mL into 1 mL of the mixed solution in S1. After ultrasonic treatment for 20 min, transfer the mixed solution to a 50 mL high-pressure hydrothermal reaction kettle. Place the high-pressure hydrothermal reaction kettle in an electrothermal constant temperature forced air drying oven, set the temperature to 150 °C and the reaction time to 15 h. Take out the high-pressure hydrothermal reaction kettle when the temperature drops to room temperature, and centrifuge and wash it three times with methanol and deionized water respectively to obtain a ruthenium-cobalt-based organometallic framework;

[0048] S3. Place the prepared ruthenium-cobalt-based organometallic framework powder in a muffle furnace. Under an air atmosphere, heat it at 5 o °C / min -1 to 450 o °C and keep it at this temperature for 2 h; After the reaction is completed, cool it to room temperature to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, labeled as Ru-Co3O4.

[0049] The catalyst prepared in this example was observed for its microscopic morphology by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM results are as Figure 1 shown, and the TEM image is as Figure 2 shown. It can be seen from Figure 1 - Figure 2 that the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst maintains a sheet structure. The X-ray diffraction (XRD) pattern of the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared in this example is as Figure 3 shown. It can be seen from Figure 3 that the characteristic peaks of cobalt tetroxide are shown in the catalyst, and at the same time, the characteristic peaks of ruthenium oxide do not appear, which proves the successful synthesis of the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0050] Example 2: This example provides a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, which is prepared by the following preparation method:

[0051] S1. Weigh 149 mg of cobalt nitrate hexahydrate and 315 mg of trimesic acid, dissolve them in a methanol solution containing 11 mL of methanol and 11 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it mix evenly;

[0052] S2. Drop the methanol solution of potassium ruthenate with a concentration of 5 mg / mL into 1 mL of the mixed solution in S1. After ultrasonic treatment for 20 min, transfer the mixed solution to a 50 mL high-pressure hydrothermal reaction kettle. Place the high-pressure hydrothermal reaction kettle in an electrothermal constant temperature forced air drying oven, set the temperature to 110 °C and the reaction time to 20 h. Take out the high-pressure hydrothermal reaction kettle when the temperature drops to room temperature, and centrifuge and wash it three times with methanol and deionized water respectively to obtain a ruthenium-cobalt-based organometallic framework;

[0053] S3. Place the prepared ruthenium-cobalt-based metal-organic framework powder in a muffle furnace. Under an air atmosphere, heat it at a rate of 1 o °C / min -1 to 450 o °C and keep it at this temperature for 2.5 h. After the reaction is completed, cool it to room temperature to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0054] Example 3: This example provides a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, which is prepared by the following method:

[0055] S1. Weigh 77.5 mg of cobalt sulfate and 420 mg of trimesic acid, dissolve them in a methanol solution containing 20 mL of methanol and 4 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed.

[0056] S2. Drop 1 mL of a methanol solution of ruthenium chloride with a concentration of 15 mg / mL into the mixed solution in S1. After ultrasonication for 20 min, transfer the mixed solution to a 50 mL high-pressure hydrothermal reactor, put the high-pressure hydrothermal reactor into an electrothermal constant temperature blast drying oven, set the temperature to 170 °C and the reaction time to 10 h. When the temperature drops to room temperature, take out the high-pressure hydrothermal reactor and centrifuge and wash it three times with methanol and deionized water respectively to obtain a ruthenium-cobalt-based metal-organic framework.

[0057] S3. Place the prepared ruthenium-cobalt-based metal-organic framework powder in a muffle furnace. Under an air atmosphere, heat it at a rate of 3 o °C / min -1 to 550 o °C and keep it at this temperature for 2 h. After the reaction is completed, cool it to room temperature to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0058] Example 4: This example provides a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, which is prepared by the following method:

[0059] S1. Weigh 238 mg of cobalt dichloride hexahydrate and 1050 mg of trimesic acid, dissolve them in a methanol solution containing 20 mL of methanol and 5 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed.

[0060] S2. Drop the methanol solution of ruthenium chloride with a concentration of 5 mg / mL into 1 mL of the mixed solution in S1, ultrasonicate for 20 min, then transfer it to a 50 mL high-pressure hydrothermal reactor. Place the high-pressure hydrothermal reactor in an electrothermal constant temperature forced air drying oven, set the temperature to 120 °C and the reaction time to 18 h. When the temperature drops to room temperature, take out the high-pressure hydrothermal reactor and centrifuge and wash it three times with methanol and deionized water respectively to obtain a ruthenium-cobalt-based metal-organic framework;

[0061] S3. Place the prepared ruthenium-cobalt-based metal-organic framework powder in a muffle furnace. Under an air atmosphere, raise the temperature at a rate of 3 o °C / min -1 to 450 o °C and keep it at this temperature for 2 h; After the reaction is completed, cool it to room temperature to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0062] Example 5: This example provides a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, which is prepared by the following preparation method:

[0063] S1. Weigh 149 mg of cobalt nitrate hexahydrate and 850 mg of trimesic acid, dissolve them in a methanol solution containing 20 mL of methanol and 2 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it mix evenly;

[0064] S2. Drop the methanol solution of potassium ruthenate with a concentration of 15 mg / mL into 1 mL of the mixed solution in S1, ultrasonicate for 20 min, then transfer it to a 50 mL high-pressure hydrothermal reactor. Place the high-pressure hydrothermal reactor in an electrothermal constant temperature forced air drying oven, set the temperature to 160 °C and the reaction time to 12 h. When the temperature drops to room temperature, take out the high-pressure hydrothermal reactor and centrifuge and wash it three times with methanol and deionized water respectively to obtain a ruthenium-cobalt-based metal-organic framework;

[0065] S3. Place the prepared ruthenium-cobalt-based metal-organic framework powder in a muffle furnace. Under an air atmosphere, raise the temperature at a rate of 2 o °C / min -1 to 450 o °C and keep it at this temperature for 3 h; After the reaction is completed, cool it to room temperature to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

[0066] Comparative Example 1: This comparative example provides a catalyst, which is only different from that in Example 1 in that ruthenium doping is not carried out in this comparative example, and it is prepared by the following steps:

[0067] S1. Weigh 149 mg of cobalt nitrate hexahydrate and 210 mg of trimesic acid, dissolve them in a methanol solution containing 20 mL of methanol and 2 mL of deionized water, then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it mix evenly.

[0068] S2. Transfer the mixed solution to a 50 mL high-pressure hydrothermal reaction kettle, put the high-pressure hydrothermal reaction kettle into an electrothermal constant temperature blast drying oven, set the temperature to 150 °C and the reaction time to 15 h. When the temperature drops to room temperature, take out the high-pressure hydrothermal reaction kettle and centrifuge and wash it three times with methanol and deionized water respectively to obtain a cobalt-based metal-organic framework.

[0069] S3. Place the prepared cobalt-based metal-organic framework powder in a muffle furnace. Under an air atmosphere, heat it at 5 o °C / min -1 to 450 o °C and keep it warm for 2 h. After the reaction is completed, cool it to room temperature to obtain a cobalt metal oxide nanosheet electrocatalyst, denoted as Co3O4.

[0070] Comparative Example 2: This comparative example provides a Pt / C material, which is obtained through commercial channels.

[0071] Application Example: (1) Use a three-electrode system. Respectively use the glassy carbon coated with the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared in Example 1, the glassy carbon coated with the cobalt oxide nanosheet electrocatalyst prepared in Comparative Example 1, and the glassy carbon coated with Pt / C in Comparative Example 2 as the working electrode, the counter electrode is a carbon rod, the reference electrode is a saturated Hg / HgO electrode, and the electrolyte is 1 M KOH;

[0072] (2) CV activation: Use a Shanghai Chenhua CHI 760E electrochemical workstation. Before testing, pass nitrogen into the electrolyte for 30 min. Adopt the CV program, the test range is -0.8 to -1.5 V vs. RHE, and the scan rate is 50 mV s -1 , and cycle 40 times until the electrode reaches a stable state.

[0073] Perform linear sweep voltammetry (LSV) tests on the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst prepared in Example 1, the cobalt oxide nanosheet electrocatalyst prepared in Comparative Example 1, and Pt / C in Comparative Example 2;

[0074] After activation, switch the program to the LSV program. The test range is -0.8 to -1.5 V vs. RHE, and the scan rate is 5 mV s -1 , and the overpotential is the difference between the potential measured at 0 V relative to the reversible hydrogen electrode and the potential measured at 10 mA cm -2 ². Figure 4Polarization curves of glassy carbon coated with the catalyst prepared in Example 1 of the present invention, the catalyst prepared in Comparative Example 1, and Pt / C of Comparative Example 2 during the alkaline electrolytic water hydrogen evolution reaction in the application example; from Figure 4 As can be seen, in the alkaline hydrogen evolution reaction, the overpotential of the Ru-Co3O4 catalyst prepared in Example 1 of the present invention is only 20 mV, and the effect is significantly better than that of Co3O4 and commercial Pt / C.

[0075] Perform a stability test on the ruthenium-doped cobalt metal oxide nanorod electrocatalyst Ru-Co3O4 prepared in Example 1:

[0076] After CV activation, switch the program to the ISTEP program, set the current to 0.7 mA, and set the time to 100 h. The test results are as Figure 5 shown. As can be seen from Figure 5 it that the potential of the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst basically does not change, proving its good oxygen evolution stability.

[0077] As can be seen from the above results, for the ruthenium-doped cobalt metal oxide nanosheet electrocatalyst provided by the present invention, through ruthenium doping, the electronic environment of cobalt and ruthenium metal sites is optimized, improving the catalytic activity while ensuring the relative stability of the site valence state.

[0078] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A preparation method of a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, characterized in that, The preparation method specifically includes the following steps: S1. Weigh cobalt salt and trimesic acid and dissolve them together in a methanol solution. After a first ultrasonic mixing treatment, a mixed solution A is obtained; The molar ratio of cobalt salt to trimesic acid is 1:(2 - 5); S2. Drop the methanol solution containing ruthenium salt into the mixed solution A prepared in step S1. After a second ultrasonic mixing treatment, a mixed solution B is obtained. The mixed solution B is subjected to a hydrothermal reaction to obtain a ruthenium-cobalt metal-organic framework precursor; S3. The ruthenium-cobalt metal-organic framework precursor prepared in step S2 is subjected to a calcination treatment to obtain a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the cobalt salt is a soluble salt, and the type of cobalt salt is selected from one of nitrate, chloride, sulfate, hydrate of nitrate, hydrate of chloride, and hydrate of sulfate.

3. The preparation method according to claim 1, characterized in that, In step S1, the methanol solution is composed of deionized water and methanol, and in the methanol solution, the volume ratio of deionized water to methanol is 1:(1 - 10).

4. The preparation method according to claim 1, characterized in that, In step S2, in the methanol solution containing ruthenium salt: the concentration of ruthenium salt is 5 - 15 mg / mL.

5. The preparation method according to claim 4, characterized in that, In step S2, the type of ruthenium salt is selected from one of chloride, ruthenate, hydrate of chloride, and hydrate of ruthenate.

6. The preparation method according to claim 1, characterized in that, In step S2, the hydrothermal reaction is carried out in a high-pressure hydrothermal reactor, and the parameters of the hydrothermal reaction are as follows: the temperature is 110 - 170 °C, and the time is 10 - 20 h.

7. The preparation method according to claim 1, characterized in that, In step S3, the parameters of the calcination treatment are as follows: the temperature is 350 - 550 °C, the heating rate is 1 - 5 °C / min, the atmosphere is air, and the time is 2 - 3 h.

8. A ruthenium-doped cobalt metal oxide nanosheet electrocatalyst, characterized in that, Prepared by using the preparation method described in any one of claims 1 - 7.

9. Application of a ruthenium-doped cobalt metal oxide nanosheet electrocatalyst as described in claim 8 as a working electrode in the cathodic hydrogen evolution reaction of water electrolysis in an alkaline solution.

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