Carbon-loaded cobalt phosphate nanodot material as well as preparation method and application thereof

Abstract

The invention discloses a carbon-loaded cobalt phosphate nanodot material as well as a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage materials. The preparation method of the carbon-loaded cobalt phosphate nanodot material comprises the following steps: S01, adding cobaltosic oxide into a first solvent, and carrying out ultrasonic dispersion and uniform mixing to obtain a cobaltosic oxide dispersion solution; s02, adding organic phosphonic acid and a second solvent into the cobaltosic oxide dispersion solution, and reacting in a nitrogen environment; after the reaction is finished, cooling to room temperature, and centrifuging the mixed solution to obtain a sample containing impurities; adding a washing solution for soaking and stirring; centrifuging the product, and drying to obtain a precursor material; and S03, carrying out annealing treatment on the precursor material in a vacuum environment or a nitrogen environment to obtain the carbon-loaded cobalt phosphate nanodot material. The carbon-loaded cobalt phosphate nanodot electro-catalytic material with high purity, good dispersity and uniform size is obtained, and shows excellent electro-catalytic activity in oxygen evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials technology, and in particular to a carbon-supported cobalt phosphate nanodot material, its preparation method, and its application. Background Technology

[0002] Nanodots refer to nanoparticle materials with a particle size of less than or equal to 10 nm. They are zero-dimensional spheres with extremely high specific surface area and unique physical and chemical properties due to the quantum confinement effect, showing extraordinary application potential in many fields such as photovoltaics and catalysis. However, nanodots are small in size, have high surface energy, are highly active, and are extremely unstable, easily agglomerating or oxidizing.

[0003] Cobalt phosphate crystals possess a rigid framework structure, in which phosphate groups are strongly covalently bonded to cobalt ions, effectively stabilizing the electrophilic cobalt active sites and endowing the material with excellent structural stability, especially in resisting corrosion and phase transitions during redox processes. Cobalt exhibits diverse valence states, enabling high redox activity and abundant active sites. Its synergistic effect with phosphate groups enhances the catalyst's adsorption capacity for water molecules and intermediate products, further improving catalytic efficiency.

[0004] However, cobalt phosphate nanodots suffer from low conductivity and poor dispersibility, which reduces the exposure of adsorption sites and lowers electrocatalytic activity. To address these issues, combining them with a carbon support can significantly reduce charge transfer resistance, prevent oxidation, corrosion, and aggregation of metal nanoparticles during electrocatalysis, enhance catalyst stability, improve dispersibility, and expose more electrocatalytic active sites.

[0005] Chemical Engineering Journal, 2021(31):130854 reported a self-supporting nickel-cobalt phosphate electrocatalyst prepared using ZIF-67-derived cobalt-nitrogen co-doped carbon material (Co-NC) as a precursor and nickel foam (NF) as a current collector. The synthesis of the precursor ZIF-67 (cobalt-based MOF) itself is complex and costly, and the use of sodium hypophosphite as a phosphorus source for phosphating easily generates highly toxic, flammable, and explosive phosphine (PH3) gas. Small, 2020,16(12) reported a mixed dihydrogen / cobalt metaphosphate supported nano-carbon flower composite material prepared by uniformly modifying a cobalt polymer onto a mesoporous layered structure of exfoliated carbon nanoflowers (NCF). The preparation steps of the carbon nanoflowers used in its substrate are relatively cumbersome and costly, the solvent acetonitrile is toxic and flammable, and the low-temperature heat treatment also results in the carbon support having a much lower conductivity than high-temperature graphitized carbon. Clearly, how to efficiently and controllably prepare uniformly dispersed carbon-supported cobalt phosphate nanodots remains a challenge in this research field. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a carbon-supported cobalt phosphate nanodot material, its preparation method, and its application. This aims to solve the problems of complex synthesis, cumbersome steps, high cost, and safety hazards caused by the generation or use of highly toxic, flammable, and explosive substances during the preparation of carbon-supported cobalt phosphate materials in existing technologies. The preparation method of this invention uses hexylphosphonic acid (HPA) as an etchant and template agent in the reaction system, and reacts with cobalt tetroxide. When cobalt tetroxide is separated by HPA, hydrogen ions (H... + After acid etching, the generated metal ions will react with the hexylphosphonic acid anions (PA) after deprotonation by HPA. - () Combination. Through the strong ionic bonds between phosphate and metal ions, and PA - The solvent-dependent effect of the tail-end carbon chains spontaneously assembles them into layered micelles. Subsequently, the obtained precursor material is subjected to assisted annealing under high vacuum or nitrogen conditions, ultimately yielding carbon-supported cobalt phosphate nanodot materials with a uniform nanodot distribution. This preparation method is simple and highly controllable, avoiding the complex template removal steps in traditional methods, and provides a new approach for the preparation of high-performance carbon-supported functional materials.

[0007] To achieve the above objectives, in one aspect, embodiments of the present invention provide a method for preparing carbon-supported cobalt phosphate nanodot materials, comprising the following steps:

[0008] S01. Cobalt tetroxide is added to the first solvent and ultrasonically dispersed and mixed to obtain a cobalt tetroxide dispersion solution.

[0009] S02. Add organophosphonic acid and the second solvent to the cobalt tetroxide dispersion obtained in step S01 and react under nitrogen atmosphere; after the reaction is completed, cool to room temperature and centrifuge the mixed solution to obtain a sample containing impurities; add washing solution to the sample containing impurities and soak and stir; centrifuge the product and dry it to obtain the precursor material;

[0010] S03. Anneal the precursor material obtained in step S02 in a vacuum or nitrogen environment to obtain carbon-supported cobalt phosphate nanodot material.

[0011] In a preferred embodiment, in step S01,

[0012] The first solvent is preferably n-hexane, and the solid-liquid ratio of cobalt tetroxide to n-hexane is 100mg:5ml to 100mg:10ml.

[0013] The ultrasonic instrument used for the ultrasound is an ultrasonic cleaner; the conditions for the ultrasound are an ultrasonic power of 800W, an ultrasonic frequency of 40kHz, and an ultrasonic time of 15-30min.

[0014] In a preferred embodiment, in step S02,

[0015] The organophosphonic acid is n-hexylphosphonic acid (HPA). The n-hexylphosphonic acid simultaneously serves as a phosphorus source, carbon source, and template agent, avoiding the introduction and removal of additional templates, resulting in a simpler and more environmentally friendly system.

[0016] The second solvent is at least one of lauric acid or trioctylphosphonic acid. Lauric acid or trioctylphosphonic acid has a high boiling point, enabling successful high-temperature testing.

[0017] The molar ratio of cobalt tetroxide to the organophosphonic acid is 1:8.

[0018] The mass of the second solvent used is 50 to 200 times that of cobalt tetroxide.

[0019] The initial temperature of the reaction is 60°C, the reaction temperature is 240–300°C, and the reaction time is 4–8 hours.

[0020] The specific steps of the reaction are as follows: under magnetic stirring (stirring speed set at 450-600 rpm), the temperature is raised to 60°C and held for 1 hour in a nitrogen atmosphere to remove the first solvent (n-hexane) from the mixed solution; then a condenser is connected, the temperature is raised to 240-300°C and held for 4-8 hours.

[0021] The cooling method involves removing the heating device after the reaction is complete, allowing the sample to cool rapidly to room temperature.

[0022] The washing solution is used in an amount 10 to 20 times the sample volume. Immersion in the washing solution removes residual impurities generated during the reaction.

[0023] The washing solution is at least one of N,N-dimethylformamide, a mixture of methanol and acetone in a volume ratio of 2:3, and ethanol.

[0024] The centrifuge speed is set to 9000-10000 rpm, and each centrifugation lasts 8-15 minutes.

[0025] Each soaking and stirring session lasts 10–12 hours, followed by centrifugation, replacement of the washing solvent, and soaking and stirring again.

[0026] The soaking and stirring are repeated 3 to 5 times;

[0027] The soaking and stirring refers to the process of placing the conical flask containing a magnetic rotor on a magnetic stirring table, with the stirring speed set to 450-600 rpm.

[0028] The drying temperature is 50–100°C, and the drying time is 10–12 hours.

[0029] The drying process is preferably carried out in an electrically heated forced-air drying oven.

[0030] In a preferred embodiment, in step S03...

[0031] The high-temperature reactor vessel for the annealing treatment is a corundum ark; the high-temperature heat treatment equipment for the annealing treatment is a water-cooled tube furnace.

[0032] The vacuum environment is defined as a vacuum level of 10. -5 Pa.

[0033] The annealing temperature is 440–600℃, and the annealing time is 3–8 hours. When the annealing temperature is 440–600℃, the obtained carbon-supported cobalt phosphate nanodot material has a nanodot size of approximately 4 nm, exhibiting excellent electrocatalytic reaction performance. More preferably, the annealing temperature is 450–550℃, and the annealing time is 4–6 hours.

[0034] On the other hand, this embodiment of the invention also provides a carbon-supported cobalt phosphate nanodot material, obtained by the above preparation method.

[0035] Furthermore, this invention also provides the application of the aforementioned carbon-supported cobalt phosphate nanodot material in electrocatalysis and electrochemical energy storage energy conversion materials. Specifically, the carbon-supported cobalt phosphate nanodot material is used as an OER electrocatalyst in electrocatalysis and electrochemical energy storage energy conversion materials.

[0036] Compared with the prior art, this application has the following technical effects:

[0037] This application proposes a method for preparing carbon-supported cobalt phosphate nanodots by reacting hexylphosphonic acid (HPA) with cobalt tetroxide followed by high vacuum or nitrogen annealing. This method offers significant technical advantages. First, HPA simultaneously serves as an organic template, phosphorus source, and carbon source, simplifying the reaction system and reducing preparation costs. Second, the strong ionic bonds between phosphate and metal ions, along with the solubilizing effect of the PA-tailed carbon chain, effectively guide the formation of a highly ordered layered micelle structure, achieving the directional assembly of the precursor. Finally, the carbon nanodots are annealed under high vacuum (10⁻⁶ ppm). -5Heat treatment under conditions of Pa or nitrogen allows the template to decompose completely at lower temperatures, significantly inhibiting grain growth and structural collapse. Cobalt phosphate nanodots are generated in situ on a carbon matrix derived from HPA, thus successfully obtaining a carbon-supported cobalt phosphate nanodot material with a nanodot diameter that can be controlled from 4 to 10 nm. Compared with traditional hard template methods, soft template methods, or metal-organic framework derivatization methods, the method in this application has strong nanodot size control capability, mild process conditions, simple synthesis steps, and excellent product performance. It is particularly suitable for the preparation of energy conversion materials and devices such as electrocatalysis and electrochemical energy storage, and has broad application prospects and promotional value. Attached Figure Description

[0038] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a TEM characterization image of the carbon-supported cobalt phosphate nanodot material prepared in Example 1 of the present invention;

[0040] Figure 2 This is a TEM characterization image of the carbon-supported cobalt phosphate nanoparticle material prepared in Comparative Example 1 of this invention.

[0041] Figure 3 The image shows the XRD characterization of the carbon-supported cobalt phosphate nanoparticles prepared in Comparative Example 1 of this invention.

[0042] Figure 4 This is a comparison of the LSV curves of carbon-supported cobalt phosphate nanoparticles prepared in Example 1 and Comparative Example 1 of the present invention.

[0043] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] The numerical range of this invention includes the numbers that define the range. The phrase “comprising” is used herein as an open-ended term, substantially equivalent to the words “including, but not limited to,” and the phrase “comprising” has a corresponding meaning. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural indicators. Thus, for example, reference to “one thing” includes more than one such thing, including substantially all embodiments and variations as described herein and with reference to examples and figures.

[0046] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0047] It should be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0048] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0049] Currently, existing technologies for preparing carbon-supported cobalt phosphate materials suffer from drawbacks such as complex synthesis, cumbersome steps, high cost, and the potential safety hazards posed by the generation or use of highly toxic, flammable, and explosive substances during the preparation process. To address these technical problems, this invention proposes a carbon-supported cobalt phosphate nanodot material, its preparation method, and its applications.

[0050] This invention provides a method for preparing carbon-supported cobalt phosphate nanodot materials, comprising the following steps:

[0051] S01. Place cobalt tetroxide in an experimental apparatus containing n-hexane, and place the experimental apparatus in an ultrasonic instrument for ultrasonic dispersion and mixing to obtain a cobalt tetroxide dispersion solution.

[0052] S02. Place the organophosphonic acid, solvent, and high-temperature magnetic rotor into the experimental apparatus of S01. Place the experimental apparatus in the heating device and heat the experimental apparatus under nitrogen atmosphere to carry out the reaction. After the reaction is completed, cool to room temperature and centrifuge the mixed solution to obtain a sample containing impurities. Then add washing solution to the sample containing impurities and soak and stir. After soaking and stirring is completed, centrifuge the product, dry it, and obtain the precursor material.

[0053] S03. Take out the precursor material from step S02, put the precursor material into a high-temperature reactor dish, and put the high-temperature reactor dish with the precursor material into a high-temperature heat treatment device for vacuum annealing to obtain carbon-supported cobalt phosphate nanodot material.

[0054] In a preferred embodiment, in step S01,

[0055] The specific steps are as follows: Cobalt tetroxide is placed in a three-necked flask containing n-hexane, the three-necked flask is placed in an ultrasonic cleaner, the ultrasonic power is adjusted to 800W, the ultrasonic frequency is 40kHz, and the three-necked flask is fixed with a cross clamp. The ultrasonic time is 15-30 minutes to obtain a uniformly dispersed mixed solution of cobalt tetroxide.

[0056] The solid-liquid ratio of cobalt tetroxide to n-hexane is 100mg:5ml to 100mg:10ml.

[0057] In a preferred embodiment, in step S02,

[0058] The organophosphonic acid mentioned is hexylphosphonic acid (HPA), and the solvent is at least one of lauric acid or trioctylphosphonic acid. HPA serves as a phosphorus source, carbon source, and template agent simultaneously, avoiding the introduction and removal of additional templates, resulting in a simpler and more environmentally friendly system; lauric acid or trioctylphosphonic acid has a high boiling point, enabling successful high-temperature testing.

[0059] The molar ratio of cobalt tetroxide to organophosphonic acid is 1:8.

[0060] The mass of the solvent used is 50 to 200 times that of cobalt tetroxide.

[0061] The specific steps of the reaction are as follows: turn on the magnetic stirrer (set the stirring speed to 450-600 rpm), introduce nitrogen into the three-necked flask and raise the temperature of the heating mantle to 60°C and keep it at that temperature for 1 hour to remove n-hexane from the mixed solution; then connect the condenser and raise the temperature of the heating mantle to 240-300°C and keep it at that temperature for 4-8 hours.

[0062] The washing solution is used in an amount 10 to 20 times the sample volume. Immersion in the washing solution removes residual impurities generated during the reaction.

[0063] The washing solution is at least one of N,N-dimethylformamide, a mixture of methanol and acetone in a volume ratio of 2:3, and ethanol.

[0064] The centrifuge speed is set to 9000-10000 rpm, and each centrifugation lasts 8-15 minutes.

[0065] Each soaking and stirring session lasts 10–12 hours, followed by centrifugation, replacement of the washing solvent, and soaking and stirring again.

[0066] The soaking and stirring are repeated 3 to 5 times;

[0067] The soaking and stirring refers to the process of placing the conical flask containing a magnetic rotor on a magnetic stirring table, with the stirring speed set to 450-600 rpm.

[0068] The drying temperature is 50–100°C, and the drying time is 10–12 hours.

[0069] The drying process is preferably carried out in an electrically heated forced-air drying oven.

[0070] In a preferred embodiment, in step S03...

[0071] The high-temperature reactor vessel is a corundum ark; the high-temperature heat treatment equipment is a water-cooled tube furnace.

[0072] The vacuum environment is defined as a vacuum level of 10. -5 Pa.

[0073] The annealing temperature is 440–600℃; the annealing time is 3–8 hours.

[0074] Example 1

[0075] A method for preparing carbon-supported cobalt phosphate nanodots includes the following steps:

[0076] S01. Place cobalt tetroxide in an experimental apparatus containing n-hexane, and place the experimental apparatus in an ultrasonic instrument for ultrasonication.

[0077] S02. Place the organophosphonic acid, solvent, and high-temperature magnetic rotor into the experimental apparatus of S01. Place the experimental apparatus in the heating device and heat the experimental apparatus under nitrogen atmosphere to carry out the reaction. After the reaction is completed, cool to room temperature and centrifuge the mixed solution to obtain a sample containing impurities. Then add washing solution to the sample containing impurities and soak and stir. After soaking and stirring is completed, centrifuge and dry to obtain the precursor material.

[0078] S03. Take out the precursor material from step S02, put the precursor material into a high-temperature reactor dish, and put the high-temperature reactor dish with the precursor material into a high-temperature heat treatment device for nitrogen annealing treatment to finally obtain carbon-supported cobalt phosphate nanodot material.

[0079] In step S01,

[0080] The amount of cobalt tetroxide used is 315 mg.

[0081] The amount of n-hexane (the first solvent) used is 12 ml.

[0082] The experimental setup is a three-necked flask.

[0083] The ultrasonic instrument is an ultrasonic cleaner device.

[0084] The conditions for the ultrasound were: ultrasound power of 800W, ultrasound frequency of 40kHz, and ultrasound time of 30min.

[0085] In step S02,

[0086] The organophosphonic acid is n-hexylphosphonic acid (HPA).

[0087] The solvent is lauric acid.

[0088] The magnetic stirring speed during the reaction was 550 rpm.

[0089] The molar ratio of cobalt tetroxide to organophosphonic acid is 1:8.

[0090] The solvent has a mass of 30g.

[0091] The initial temperature of the reaction is 60°C, and the reaction temperature is 290°C.

[0092] The reaction time was 6 hours.

[0093] The cooling method involves removing the heating device after the reaction is complete, allowing the sample to cool rapidly to room temperature.

[0094] The washing solution used is 40 ml, and the washing solution is N,N-dimethylformamide.

[0095] The centrifuge speed was set to 9000 rpm, and each centrifugation lasted 10 minutes.

[0096] The soaking and stirring time is 10 hours, followed by centrifugation, changing the washing solvent, soaking and stirring again, and repeating this process 4 times.

[0097] The soaking and stirring refers to the process of placing the conical flask containing a magnetic rotor on a magnetic stirring table, with the stirring speed set at 550 rpm.

[0098] The drying temperature is 60°C, and the drying time is 10 hours.

[0099] The drying process is carried out in an electrically heated blast drying oven.

[0100] In step S03,

[0101] The high-temperature reactor vessel is a corundum ark; the high-temperature heat treatment equipment is a water-cooled tube furnace.

[0102] The annealing temperature is 500℃; the annealing time is 6 hours.

[0103] The carbon-supported cobalt phosphate nanodots prepared in Example 1 were characterized and tested. The TEM images of the test results are shown below. Figure 1 As shown.

[0104] Comparative Example 1

[0105] A method for preparing carbon-supported cobalt phosphate nanoparticles includes the following steps:

[0106] S01. Place cobalt tetroxide in an experimental apparatus containing n-hexane, and place the experimental apparatus in an ultrasonic instrument for ultrasonication.

[0107] S02. Place the organophosphonic acid, solvent, and high-temperature magnetic rotor into the experimental apparatus of S01. Place the experimental apparatus in the heating device and heat the experimental apparatus under nitrogen atmosphere to carry out the reaction. After the reaction is completed, cool to room temperature and centrifuge the mixed solution to obtain a sample containing impurities. Then add washing solution to the sample containing impurities and soak and stir. After soaking and stirring is completed, centrifuge and dry to obtain the precursor material.

[0108] S03. Take out the precursor material from step S02, put the precursor material into a high-temperature reactor dish, and put the high-temperature reactor dish with the precursor material into a high-temperature heat treatment device for nitrogen annealing treatment to finally obtain carbon-supported cobalt phosphate nanoparticle material.

[0109] In step S01,

[0110] The amount of n-hexane (the first solvent) used is 12 ml.

[0111] The amount of cobalt tetroxide used is 315 mg.

[0112] The experimental setup is a three-necked flask.

[0113] The ultrasonic instrument is an ultrasonic cleaner device.

[0114] The conditions for the ultrasound were: ultrasound power of 800W, ultrasound frequency of 40kHz, and ultrasound time of 30min.

[0115] In step S02,

[0116] The organophosphonic acid is n-hexylphosphonic acid (HPA).

[0117] The solvent is lauric acid.

[0118] The magnetic stirring speed during the reaction was 550 rpm.

[0119] The molar ratio of cobalt tetroxide to organophosphonic acid is 1:8.

[0120] The solvent has a mass of 30g.

[0121] The initial temperature of the reaction is 60°C, and the reaction temperature is 290°C.

[0122] The reaction time was 6 hours.

[0123] The cooling method involves removing the heating device after the reaction is complete, allowing the sample to cool rapidly to room temperature.

[0124] The washing solution used is 40 ml, and the washing solution is N,N-dimethylformamide.

[0125] The centrifuge speed was set to 9000 rpm, and each centrifugation lasted 10 minutes.

[0126] The soaking and stirring time is 10 hours, followed by centrifugation, changing the washing solvent, soaking and stirring again, and repeating this process 4 times.

[0127] The soaking and stirring refers to the process of placing the conical flask containing a magnetic rotor on a magnetic stirring table, with the stirring speed set at 550 rpm.

[0128] The washing solution is still ethanol.

[0129] The amount of the washing solution used is 40 ml.

[0130] The washing cycle is 1 time.

[0131] The drying temperature is 60°C, and the drying time is 10 hours.

[0132] The drying process is carried out in an electrically heated blast drying oven.

[0133] In step S03,

[0134] The high-temperature reactor vessel is a corundum ark; the high-temperature heat treatment equipment is a water-cooled tube furnace.

[0135] The annealing temperature is 700℃; the annealing time is 3 hours.

[0136] The carbon-supported cobalt phosphate nanoparticles prepared in Comparative Example 1 were characterized and tested. The TEM images of the results are shown below. Figure 2 As shown.

[0137] The characterization test results of the materials obtained in Examples 1 and 2 are as follows:

[0138] Figure 1 This is a TEM characterization image of the carbon-supported cobalt phosphate nanodot material provided in Example 1; from Figure 1 The overall morphology of the carbon load can be observed to be a nanosheet structure, with the size of the nanosheets reaching hundreds of nanometers. Cobalt phosphate nanodots are uniformly dispersed on the carbon nanosheets, with a uniform size of about 4 nm. The carbon load anchors the nanodots on its surface, and no nanodot aggregation phenomenon is observed.

[0139] Figure 2 The TEM image shows the carbon-supported cobalt phosphate nanoparticles prepared in Comparative Example 1; from Figure 2 Rod-shaped particles with a size of tens of nanometers were observed, and the lattice fringes were obvious, indicating that the particles had good crystallinity.

[0140] Figure 3 XRD characterization of the carbon-supported cobalt phosphate nanoparticles prepared in Comparative Example 1; Figure 3 This indicates that the cobalt metaphosphate nanoparticles are highly crystalline.

[0141] Figure 4 This is a comparison of the LSV curves of the carbon-supported cobalt phosphate nanodot material prepared in Example 1 of this invention and the carbon-supported cobalt phosphate nanoparticle material prepared in Comparative Example 1. From... Figure 4 The study observed that the OER electrocatalytic performance of carbon-supported cobalt phosphate nanodots with a nanodot size of 4 nm was far superior to that of carbon-supported cobalt phosphate nanoparticles with a nanoparticle size of tens of nanometers, indicating that smaller cobalt phosphate nanodots have stronger catalytic activity.

[0142] In summary, the test results show that the carbon-supported cobalt phosphate nanodots of this application, obtained through organophosphonic acid-guided layer-by-layer self-assembly and high-vacuum or nitrogen annealing processes, yielded a carbon-supported cobalt phosphate nanodot electrocatalytic material with high purity, good dispersibility, and uniform size, exhibiting excellent electrocatalytic activity in the oxygen evolution reaction (OER). Furthermore, the size of the cobalt phosphate nanodots can be adjusted by regulating the annealing temperature and time to meet different application requirements.

[0143] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing carbon-supported cobalt phosphate nanodot materials, characterized in that: Includes the following steps: S01. Cobalt tetroxide is added to the first solvent and ultrasonically dispersed and mixed to obtain a cobalt tetroxide dispersion solution. S02. Add organophosphonic acid and the second solvent to the cobalt tetroxide dispersion obtained in step S01 and react under nitrogen atmosphere; after the reaction is completed, cool to room temperature and centrifuge the mixed solution to obtain a sample containing impurities; add washing solution to the sample containing impurities and soak and stir; centrifuge the product and dry it to obtain the precursor material; S03. Anneal the precursor material obtained in step S02 in a vacuum or nitrogen environment to obtain carbon-supported cobalt phosphate nanodot material.

2. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S01, The first solvent is n-hexane, and the solid-liquid ratio of cobalt tetroxide to n-hexane is 100mg:5ml to 100mg:10ml; The ultrasonic instrument used for the ultrasound is an ultrasonic cleaner; the conditions for the ultrasound are an ultrasonic power of 800W, an ultrasonic frequency of 40kHz, and an ultrasonic time of 15-30min.

3. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S02, The organophosphonic acid is n-hexylphosphonic acid; The second solvent is at least one of lauric acid or trioctylphosphonic acid, and the mass of the second solvent used is 50 to 200 times the mass of cobalt tetroxide; The molar ratio of cobalt tetroxide to the organophosphonic acid is 1:

8.

4. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S02, The initial temperature of the reaction is 60°C, the reaction temperature is 240–300°C, and the reaction time is 4–8 hours.

5. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S02, The magnetic stirring speed during the reaction is 450–600 rpm; The washing solution is at least one of N,N-dimethylformamide, a mixture of methanol and acetone in a volume ratio of 2:3, and ethanol. The centrifuge speed is set to 9000-10000 rpm, and each centrifugation lasts 8-15 minutes. Each soaking and stirring session lasts 10–12 hours, followed by centrifugation and replacement of the washing solvent. The soaking and stirring are repeated 3 to 5 times; The stirring speed for the soaking and stirring is set to 450–600 rpm.

6. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S02, The drying temperature is 50–100°C, and the drying time is 10–12 hours. The drying process is carried out in an electrically heated blast drying oven.

7. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S03, The high-temperature reactor vessel for the annealing treatment is a corundum ark; the high-temperature heat treatment equipment for the annealing treatment is a water-cooled tube furnace. The vacuum environment is defined as a vacuum level of 10. -5 Pa.

8. The method for preparing carbon-supported cobalt phosphate nanodots according to claim 1, characterized in that: In step S03, The annealing temperature is 440–600℃; the annealing time is 3–8 hours.

9. A carbon-supported cobalt phosphate nanodot material, characterized in that: Obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the carbon-supported cobalt phosphate nanodot material according to claim 9 in energy conversion materials for electrocatalysis and electrochemical energy storage.

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