Doping modified cobalt-based catalyst and preparation method thereof

Abstract

The invention relates to the field of proton exchange membrane water electrolysis, in particular to a doped and modified cobalt-based catalyst and a preparation method thereof. Cobalt and nitrate doped with metal are dissolved in a liquid solvent containing combustible organic fuel to form a combustion solution, the porous carbon substrate is soaked in the combustion solution and taken out, combustion reaction is triggered through open fire ignition, and the catalyst is obtained. In the combustion process, the violent oxidation-reduction reaction is accompanied with rapid release of a large amount of gas, and abundant micropore structures and defect sites are induced to be formed on the surface of the substrate, so that the obtained catalyst has relatively high specific surface area and activity, and the catalytic efficiency is favorably improved.

Description

Technical Field

[0001] The present invention relates to the field of proton exchange membrane water electrolysis, and in particular to a doped and modified cobalt-based catalyst and a preparation method thereof. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis is an efficient and green hydrogen production technology that utilizes a proton exchange membrane to decompose water into hydrogen and oxygen, offering advantages such as high purity and rapid response. The hydrogen evolution reaction at the anode relies on iridium (Ir) or ruthenium (Ru)-based precious metal catalysts, whose high cost severely restricts the application and widespread adoption of water electrolysis hydrogen production technology.

[0003] Replacing precious metal catalysts with cobalt-based catalysts can effectively reduce the cost of water electrolysis. However, the catalytic performance of cobalt-based catalysts, such as cobalt oxide, is limited and cannot meet practical requirements. To improve their activity, existing technologies use transition metal doping. However, the maximum activity achieved by simply varying the doping amount and type still falls short of meeting production requirements. Summary of the Invention

[0004] The object of the present invention is to provide a doped and modified cobalt-based catalyst with higher activity and a preparation method thereof.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a doped and modified cobalt-based catalyst comprises:

[0007] Dissolving cobalt nitrate and the metal-doped nitrate in a liquid solvent to prepare a combustion solution, wherein the liquid solvent includes an organic fuel that is combustible under open flame conditions;

[0008] A porous carbon substrate is obtained, and the porous carbon substrate is immersed in the combustion solution. The porous carbon substrate is taken out and ignited with an open flame, and a doped and modified cobalt-based catalyst is obtained after complete combustion.

[0009] Optionally, the doping metal is one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0010] Optionally, the concentration of the cobalt nitrate in the combustion solution is any value between 0.5 mol / L and 1 mol / L, and the molar ratio of the doping metal element to the cobalt element in the combustion solution is any value between 1:(5 and 18).

[0011] Optionally, the liquid solvent includes only the organic fuel, and the liquid solvent is one or more of ethylene glycol, ethanol and glycerol.

[0012] Optionally, the liquid solvent includes a dispersant and the organic fuel dissolved in the dispersant, and the organic fuel is one or more of citric acid, urea, ascorbic acid, glycine and oxalic acid.

[0013] Optionally, the dispersant is water, and the concentration of the organic fuel in the liquid solvent is any value between 0.3 mol / L and 2 mol / L.

[0014] Optionally, the porous carbon substrate is ignited with an open flame and then immersed in the combustion solution again, and the process is repeated multiple times.

[0015] Optionally, after the cobalt nitrate and the metal-doped nitrate are dissolved in the liquid solvent, a dispersion treatment is performed, and the dispersion treatment includes one or more of microwave treatment and ultrasonic treatment.

[0016] Optionally, the porous carbon substrate is a cleaned carbon fiber cloth.

[0017] The present invention also provides a doped and modified cobalt-based catalyst, which is prepared by the above method and supported on the porous carbon substrate in the form of porous nanosheets.

[0018] The beneficial effects of the present invention are as follows: after uniformly mixing the doped metal ions and cobalt ions through a solution method, the mixture is attached to a porous carbon substrate, and the organic fuel, the doped metal ions and the cobalt ions undergo an instantaneous combustion reaction under high temperature conditions to generate cobalt oxide doped with doped metal atoms. Since a large amount of gas is quickly released during the combustion reaction, a large number of micropores and defect sites are formed in the generated effective substances, thereby increasing the specific surface area and activity of the catalyst and improving the reaction efficiency. Open flame combustion has a high reaction rate, which helps to form more micropores and defect sites in the product to improve the catalytic efficiency. The overall operation of the preparation method is simple, and no complex equipment is required, which helps to reduce the preparation cost of the catalyst. This method has good universality and repeatability, and has high practicality in large-scale production.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the preparation method of the doped and modified cobalt-based catalyst shown in Example 1 of the present invention;

[0021] Figure 2 This is an electron microscope image of the catalyst obtained in Example 1 of the present invention;

[0022] Figure 3This is a scanning transmission electron microscope high-angle annular dark field image of the catalyst obtained in Example 1 of the present invention;

[0023] Figure 4 The cyclic voltammetry curves of the three-electrode system corresponding to each catalyst obtained in Example 1, Example 2 and Comparative Example 1 of the present invention are shown;

[0024] Figure 5 The X-ray diffraction patterns of the catalysts and pure cobalt oxide obtained in Example 1 and Comparative Example 1 of the present invention are shown;

[0025] Figure 6 The cyclic voltammetry curves of the three-electrode system corresponding to each catalyst obtained in Example 1 and Comparative Example 1 of the present invention and pure cobalt oxide;

[0026] Figure 7 The chronopotentiometry curves of the three-electrode system corresponding to each catalyst obtained in Example 1 and Comparative Example 1 of the present invention and pure cobalt oxide;

[0027] Figure 8 is the polarization curve of an electrolytic cell using the catalyst obtained in Example 1 of the present invention and iridium dioxide as an anode catalyst;

[0028] Figure 9 This is a chronopotentiometry curve of an electrolytic cell using the catalyst obtained in Example 1 of the present invention as an anode catalyst. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0032] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The present invention applies to protect a method for preparing a doped and modified cobalt-based catalyst, comprising:

[0034] S1. Dissolving cobalt nitrate and metal-doped nitrate in a liquid solvent to prepare a combustion solution, wherein the liquid solvent includes an organic fuel, and the organic fuel is combustible under open flame conditions.

[0035] S2. Obtain a porous carbon substrate, immerse the porous carbon substrate in a combustion solution, take it out and ignite it with an open flame, and obtain a doped and modified cobalt-based catalyst after complete combustion.

[0036] After uniformly mixing doped metal ions and cobalt ions through a solution method, they are attached to a porous carbon substrate. The organic fuel, doped metal ions, and cobalt ions react instantly with each other under high temperature conditions to produce cobalt oxide doped with doped metal atoms. The rapid release of large amounts of gas during the combustion reaction creates numerous micropores and defect sites within the resulting active material, thereby increasing the specific surface area and activity of the catalyst and improving reaction efficiency. Open flame combustion has a high reaction rate, which helps form more micropores and defect sites within the product, thereby improving catalytic efficiency. The overall preparation method is simple to operate and does not require complex equipment, which helps reduce the cost of catalyst preparation. This method has good universality and reproducibility, and is highly practical for large-scale production.

[0037] In the prior art, a hydrothermal-annealing method is often used. A cobalt-containing precursor is subjected to a high-temperature, high-pressure hydrothermal reaction under sealed conditions to generate a precursor material, which is then oxidized and crystallized by high-temperature annealing. This method allows for good control of the product morphology and crystallinity, resulting in cobalt oxide that often exhibits a regular granular or bulk structure. However, due to limitations in the reaction rate and gas release process, the material's specific surface area and pore structure are often limited, and some defect sites may be trapped, affecting its electrocatalytic performance. Furthermore, the prior art solution combustion method for synthesizing metal oxides using a muffle furnace suffers from issues such as high energy consumption and imprecise reaction control. The muffle furnace requires continuous heating to maintain a high temperature environment, resulting in high energy consumption. Furthermore, its limited heating rate and temperature uniformity can lead to localized overheating or uneven reactions, compromising product purity and morphology. Furthermore, the static air atmosphere in the muffle furnace is difficult to dynamically adjust, which can easily lead to secondary oxidation or compositional deviations in the product, making it particularly unfavorable for the synthesis of complex oxides, such as doped materials or mixed-valence compounds. Furthermore, differences in sample position during batch processing can lead to temperature gradients, reducing batch consistency. These factors limit the application of this technology in efficient, controllable synthesis and large-scale production. However, the preparation method of the present invention overcomes the technical bias of improving product controllability through accurate temperature control, uses a porous carbon substrate as a carrier to support the precursor, and directly ignites the precursor with an open flame to induce oxidation of metal ions. Compared with hydrothermal post-annealing, it improves the product morphology and accelerates the reaction rate compared to heating the solution in a muffle furnace, allowing the gas to be released quickly to form more pores and defect sites, thereby increasing the contact area and activity, so that the obtained catalyst has better electrochemical properties and higher production efficiency.

[0038] In some embodiments, the doping metal is one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0039] In existing technologies, transition metals are often used as doping metals. However, transition metals compete with cobalt for defect sites. While transition metal ions have a smaller radius, they form stronger covalent bonds but are more easily dissolved in acidic conditions, leading to rapid catalyst deactivation. Lanthanum (La) compounds, with their larger ionic radius and unique 4f electron configuration, effectively stabilize the cobalt oxide's lattice structure when doped with cobalt oxide, improving the material's resistance to dissolution and significantly enhancing its catalytic stability in acidic environments.

[0040] In some embodiments, the concentration of cobalt nitrate in the combustion solution is any value between 0.5 mol / L and 1 mol / L, for example, it can be any value between 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L and 1 mol / L, which helps to fully adhere to the ions, and the molar ratio of the doped metal element to the cobalt element in the combustion solution is any value between 1: (5 and 18), for example, it can be any value between (1:5), (1:9), (1:11), (1:14) and (1:18), which helps to improve the performance of the obtained catalyst by constraining the doping ratio.

[0041] In some embodiments, the liquid solvent includes only organic fuel, and the liquid solvent is one or more of ethylene glycol, ethanol and glycerol, which has a good combustion-supporting effect and helps to accelerate the combustion reaction.

[0042] In some embodiments, the liquid solvent includes a dispersant and an organic fuel dissolved in the dispersant, and the organic fuel is one or more of citric acid, urea, ascorbic acid, glycine, and oxalic acid.

[0043] In some embodiments, the dispersant is water, and the concentration of the organic fuel in the liquid solvent is any value between 0.3 mol / L and 2 mol / L, for example, it can be any value between 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1.2 mol / L, 1.6 mol / L and 2 mol / L, which helps to accelerate the combustion reaction.

[0044] In some embodiments, the porous carbon substrate is ignited with an open flame and then immersed in a combustion solution again, and this is repeated multiple times to help increase the catalyst loading capacity.

[0045] In some embodiments, after the cobalt nitrate and the metal-doped nitrate are dissolved in a liquid solvent, a dispersion treatment is performed. The dispersion treatment includes one or more of microwave treatment and ultrasonic treatment, which helps to ensure sufficient and uniform mixing between ions.

[0046] In some embodiments, the porous carbon substrate is a cleaned carbon fiber cloth, which has good carrying capacity and facilitates the sufficient attachment of ions to its surface.

[0047] The present invention also applies for protection of a doped and modified cobalt-based catalyst, which is prepared by the above method and supported on a porous carbon substrate in the form of porous nanosheets.

[0048] Please refer to the following examples for details.

[0049] Example 1:

[0050] See Figure 1The preparation method of the doped modified cobalt-based catalyst shown in a preferred embodiment of the present application includes:

[0051] S1. Dissolving cobalt nitrate and metal-doped nitrate in a liquid solvent to prepare a combustion solution, wherein the liquid solvent includes an organic fuel, and the organic fuel is combustible under open flame conditions.

[0052] S2. Obtain a porous carbon substrate, immerse the porous carbon substrate in a combustion solution, take it out and ignite it with an open flame, and obtain a doped and modified cobalt-based catalyst after complete combustion.

[0053] The doping metal in this embodiment is neodymium. In step S1, 3.6 mmol of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 0.36 mmol of neodymium nitrate hexahydrate (Nd(NO3)3·6H2O) are accurately weighed and placed in a 10 mL beaker. 50 mL of ethylene glycol (EG) is added and ultrasonically treated for 30 minutes to obtain a uniform, clear pink solution, i.e., a combustion solution, in which no precipitate is visible to the naked eye.

[0054] Step S2 includes:

[0055] S210. Take the carbon fiber cloth and cut it into a size of 2cm×4cm, and immerse it in ethanol, acetone, 5% hydrochloric acid solution and pure water in turn. After each immersion, it is ultrasonically treated for 10 minutes and then taken out to remove impurities and oxides on the surface of the carbon fiber cloth, thereby obtaining a porous carbon substrate and weighing its mass.

[0056] S220. Fully immerse the porous carbon substrate in the combustion solution, take it out after there is no more natural dripping, and place it directly above the flame of an alcohol lamp for combustion. The combustion time is about 10 seconds.

[0057] S230. After the combustion is completed, the porous carbon substrate is fully immersed in the combustion solution again, and step S220 is repeated for a total of seven times to obtain a doped and modified cobalt-based catalyst supported on the carbon fiber cloth, and its mass is weighed.

[0058] The difference between the two weighings was used as the total mass of the doped and modified cobalt-based catalyst. The loading of the catalyst obtained in this example on the carbon fiber cloth was calculated to be approximately 7.5 mg cm -2 The doped and modified cobalt-based catalyst supported on carbon fiber cloth was named Nd-Co3O4.

[0059] See Figure 2 Using an electron microscope to examine Nd-Co3O4 on the surface of carbon fiber cloth, it can be seen that Nd-Co3O4 has a porous nanosheet structure. This unique structure gives the catalyst a large specific surface area, thereby significantly improving its catalytic performance.

[0060] Please refer to Figure 3 , scanning Nd-Co3O4 with a scanning transmission electron microscope equipped with a spherical aberration corrector, obtaining a high-angle annular dark-field scanning transmission electron microscope image (HAADF-STEM), and analyzing each atomic spacing in the figure, it can be seen that Nd exists in Nd-Co3O4 in an atomic dispersion manner, proving that Nd atoms are uniformly dispersed between Co atoms.

[0061] Example 2:

[0062] The difference between this embodiment and Example 1 is only that the doping metals in this embodiment are La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, respectively, and the doped and modified cobalt-based catalysts supported on carbon fiber cloth obtained are named as La-Co3O4, Ce-Co3O4, Pr-Co3O4, Nd-Co3O4, Sm-Co3O4, Eu-Co3O4, Gd-Co3O4, Tb-Co3O4, Dy-Co3O4, Ho-Co3O4, Er-Co3O4, Tm-Co3O4, Yb-Co3O4 and Lu-Co3O4, respectively.

[0063] Comparative Example 1:

[0064] The difference between this comparative example and Example 1 is only that the combustion solution in this comparative example is obtained by dissolving Co(NO3)2·6H2O in EG, and does not contain a doping metal nitrate, and the cobalt-based catalyst supported on carbon fiber cloth obtained is named as CoO x .

[0065] The catalysts obtained in Example 1, Example 2 and Comparative Example 1 were used for water electrolysis reaction.

[0066] The carbon fiber cloth loaded with various catalysts of equal mass was cut into a size of 0.5 cm x 0.5 cm, and was used as a working electrode. A 0.1 mol / L HClO4 acid solution was used as an electrolyte, a porous metal silver (Ag) immersed in saturated KCl solution and covered with silver chloride (AgCl) on the surface was used as a reference electrode, and a platinum wire was used as a counter electrode to form a three-electrode system, and an electrochemical workstation was connected.

[0067] Please refer to Figure 4 , the cyclic voltammograms of each three-electrode system were measured. As can be seen from the figure, the cobalt-based catalyst doped with lanthanide metals has performance advantages compared with the pure cobalt-based catalyst. As can be seen from the figure, the output of each three-electrode system is 10 mA·cm -2The overpotential required for the current density of 100 nm was 317 mV for the three-electrode system corresponding to Nd-Co3O4, while the overpotential required for the three-electrode system corresponding to each catalyst in Example 2 was within the range of 310 mV to 330 mV, indicating that each catalyst had good activity.

[0068] Purchase commercial pure cobalt oxide Co3O4 and obtain x The catalyst powder was scraped from the carbon fiber cloth surface and the purchased Co3O4 and the two catalyst powders were tested by X-ray diffraction (XRD). Figure 5 It can be seen that all three contain cobalt oxide components, but Nd-Co3O4 and CoO x The sample exhibited relatively broad diffraction peak intensities, indicating its low crystallinity.

[0069] The same mass of Co3O4 was dissolved in a solution containing deionized water, EG and a binder, and then dropped onto the surface of a carbon fiber cloth of equal size and after surface cleaning. After standing and drying, a carbon fiber cloth loaded with Co3O4 was obtained, and a three-electrode system was prepared. Co3O4, Nd-Co3O4 and CoO were detected respectively. x The corresponding cyclic voltammetry and chronopotentiometry curves of the three-electrode system.

[0070] See Figure 6 It can be seen that the CoO prepared by solution combustion method x The catalyst has higher catalytic activity than pure substance Co3O4. Figure 5 It can be inferred that CoO prepared by solution combustion method x The catalyst's crystallinity is reduced due to the presence of numerous lattice defects, and these structural defects likely provide more defect sites, leading to higher catalytic activity. Notably, Nd doping further optimizes the electronic structure of the catalyst, resulting in even better catalytic performance for the Nd-Co3O4 sample.

[0071] See Figure 7 , it can be seen that compared with the undoped CoO x Compared with pure Co3O4, Nd-Co3O4 modified with neodymium exhibits excellent stability in acidic environment, even at 10 mA cm -2 It can continue to work for more than 800 hours at a current density of 100 nm without any obvious deactivation, while the voltage change is only 76 mV and the average degradation rate is 95 μV / h, which shows that after modification with lanthanide metals, the stability of cobalt-based oxides in the acidic OER process has been effectively improved.

[0072] The scraped Nd-Co3O4 powder was used as the anode catalyst in the PEM electrolytic cell, and platinum carbon was used as the cathode to assemble the PEM electrolytic cell. The anode ink was prepared by mixing powders of various catalysts with isopropyl alcohol, deionized water, and Nafion solution. The anode ink was sprayed onto the Nafion membrane and then hot-pressed with platinum carbon and titanium plates to form a membrane electrode assembly (MEA), namely the PEM electrolytic cell, and named Nd-Co3O4||Pt / C. Using the same method, an equal amount of commercially available iridium dioxide (IrO2) was used as the anode catalyst to prepare a PEM electrolytic cell, and named IrO2||Pt / C. The PEM electrolytic cell was pretreated in pure water at 80°C, and the polarization curves of the two were tested and plotted. Please refer to the following table. Figure 8 It can be seen that Nd-Co3O4||Pt / C only needs 1.93V and 2.12V voltages to reach 1A·cm -2 and 2A·cm -2 The high current density surpasses that of IrO2||Pt / C.

[0073] See Figure 9 The chronopotentiometry curve of Nd-Co3O4||Pt / C was measured. It can be seen from the figure that the PEM electrolytic cell can -2 The device can stably operate for more than 100 h at an operating voltage of about 1.69 V at a current density of 1.5 GHz, indicating that it has high stability. Combined with its excellent electrochemical performance, it is proved that the Nd-Co3O4 obtained in the present invention has excellent industrialization potential.

[0074] Example 3:

[0075] The difference between this embodiment and the first embodiment is that the amount of Nd(NO3)3·6H2O added in this embodiment is adjusted to 0.08 mmol, 0.72 mmol, 0.45 mmol, 0.03 mmol, 0.02 mmol and 0.018 mmol, respectively. The prepared carbon fiber cloths carrying the doped modified cobalt-based catalyst are respectively assembled into a three-electrode system and connected to an electrochemical workstation to detect the output of 10 mA·cm -2 The overpotential required for the current density of 100 nm is combined with the data measured by the three-electrode system corresponding to Nd-Co3O4 in Example 1, and is summarized in Table 1 below.

[0076] Table 1:

[0077]

[0078]

[0079] It can be seen from Table 1 that when the molar ratio of Nd to Co is in the range of 1:(5-18), the measured overpotential is small, and reaches the lowest value when the molar ratio of Nd to Co is 1:10.

[0080] Example 4:

[0081] The only difference between this embodiment and the first embodiment is that the combustion solution in this embodiment is a 1 mol / L deionized citric acid solution. The prepared carbon fiber cloth carrying the doped modified cobalt-based catalyst is assembled into a three-electrode system and connected to an electrochemical workstation. The output is detected to be 10 mA cm -2 The overpotential required for the current density is 319 mV, which is not significantly different from the value corresponding to Nd-Co3O4 in Example 1.

[0082] Embodiment 5:

[0083] The only difference between this embodiment and embodiment 1 is that in this embodiment, after mixing nitrate and EG, they are heated in a microwave oven on low heat for 1 minute to obtain a combustion solution. The final catalyst is detected by HAADF-STEM, and it is found that Nd exists in an atomically dispersed manner, indicating that microwaves also help to uniformly disperse ions and have higher efficiency.

[0084] Comparative Example 2:

[0085] The only difference between this comparative example and Example 1 is that in step S2 of this comparative example, the carbon fiber cloth is immersed in the combustion solution, removed, and then dried in a vacuum drying oven at 60°C. After repeating this process seven times, the carbon fiber cloth is calcined in a muffle furnace at annealing temperatures of 200°C, 300°C, 400°C, and 500°C for 2 hours, respectively, to obtain a carbon fiber cloth loaded with catalyst. The catalyst loading on the carbon fiber cloth in this comparative example is calculated to be approximately 7 mg·cm based on the mass difference before and after loading. -2 .

[0086] The carbon fiber cloths prepared at different annealing temperatures in this comparative example were assembled into three-electrode systems, and their outputs were detected by an electrochemical workstation at 10 mA cm -2 The overpotential required for the current density is shown in Table 2 below.

[0087] Table 2:

[0088]

[0089]

[0090] As can be seen in Table 1, the catalyst annealed at 300°C exhibits the best performance. This is because Co₃O₄ typically crystallizes within a temperature range of 250°C to 350°C. 200°C is insufficient to decompose cobalt precursors, such as cobalt nitrate and neodymium nitrate, resulting in residual organic matter or the formation of amorphous cobalt oxides, such as the amorphous form of Co₃O₄, which lacks an ordered crystal structure and exhibits virtually no performance. However, at temperatures of 400°C to 500°C, the mobility of cobalt oxides, such as Co₃O₄, increases, leading to agglomeration and grain growth, a decrease in specific surface area, and a reduction in defect sites, resulting in reduced activity.

[0091] In addition, the method in this comparative example is relatively complex, time-consuming, and costly, and the performance of the resulting catalyst deviates from that of the Nd-Co3O4 catalyst in Comparative Example 1. This is because the muffle furnace environment is oxygen-deficient, which easily leads to carbonized residues, while open flame combustion facilitates more thorough oxidation and accelerates the crystallization rate. This comparative example also conducted an experiment in which the solvent was directly heat-treated at 300°C in a muffle furnace without drying. The calculated corresponding excess unit was approximately 381 mV. This is because the pyrolysis reaction occurs during solvent evaporation, which easily forms more carbon impurities in the low-oxygen muffle furnace environment, thereby reducing catalytic activity.

[0092] Comparative Example 3:

[0093] The only difference between this comparative example and Example 1 is that in step S2 of this comparative example, the combustion solution is directly placed in a muffle furnace at 300°C and calcined for 2 hours to obtain a doped catalyst. The doped catalyst is supported on a carbon fiber cloth and assembled into a three-electrode system. The output of the system is detected by an electrochemical workstation at 10 mA cm -2 The overpotential required for the current density of 100 nm is 369 mV. This demonstrates that the preparation method of the present invention is more conducive to improving the performance of the catalyst than the conventional solution combustion method.

[0094] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a doped and modified cobalt-based catalyst, characterized in that: include: Dissolving cobalt nitrate and a metal-doped nitrate in a liquid solvent to prepare a combustion solution, wherein the liquid solvent includes an organic fuel that is combustible under open flame conditions; A porous carbon substrate is obtained, and the porous carbon substrate is immersed in the combustion solution. The porous carbon substrate is taken out and ignited with an open flame, and a doped and modified cobalt-based catalyst is obtained after complete combustion.

2. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: The doping metal is one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

3. The method for preparing the doped and modified cobalt-based catalyst according to claim 2, wherein: The concentration of the cobalt nitrate in the combustion solution is any value between 0.5 mol / L and 1 mol / L, and the molar ratio of the doping metal element to the cobalt element in the combustion solution is any value between 1:(5-18).

4. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: The liquid solvent only includes the organic fuel, and the liquid solvent is one or more of ethylene glycol, ethanol and glycerol.

5. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: The liquid solvent includes a dispersant and the organic fuel dissolved in the dispersant, and the organic fuel is one or more of citric acid, urea, ascorbic acid, glycine and oxalic acid.

6. The method for preparing a doped and modified cobalt-based catalyst according to claim 5, wherein: The dispersant is water, and the concentration of the organic fuel in the liquid solvent is any value between 0.3 mol / L and 2 mol / L.

7. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: The porous carbon substrate is ignited by an open flame and then immersed in the combustion solution again, and the process is repeated multiple times.

8. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: After the cobalt nitrate and the metal-doped nitrate are dissolved in the liquid solvent, a dispersion treatment is performed, wherein the dispersion treatment includes one or more of microwave treatment and ultrasonic treatment.

9. The method for preparing a doped and modified cobalt-based catalyst according to claim 1, wherein: The porous carbon substrate is a cleaned carbon fiber cloth.

10. A doped and modified cobalt-based catalyst, characterized in that: The porous carbon nanosheet is prepared by the method according to any one of claims 1 to 9 and supported on the porous carbon substrate in the form of a porous nanosheet.

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