A fullerene-modified nickel atom electrocatalyst, its preparation method and application

Abstract

This invention discloses a fullerene-modified nickel atom electrocatalyst, its preparation method, and its application. In the fullerene-modified nickel atom electrocatalyst, nickel and fullerene are coordinated via amino groups. The preparation method includes three steps: fullerene modification, precursor preparation, and electrocatalyst preparation. The application is the generation of hydrogen peroxide using the nickel atom electrocatalyst. The fullerene-modified nickel atom electrocatalyst provided by this invention has advantages such as high hydrogen peroxide yield, good pH adaptability, and good two-electron selectivity. Unlike existing technologies that cannot target and control material properties, the preparation method provided by this invention mainly relies on zero-dimensional fullerenes to regulate the atomic coordination environment, which can stably produce high-performance nickel atom electrocatalysts, avoid dopamine oxidation, and eliminate the need for excessively high reaction temperatures, making it safer and more controllable.

Description

Technical Field

[0001] This invention relates to a nickel atom electrocatalyst, its preparation method and application, and more particularly to a fullerene-modified nickel atom electrocatalyst, its preparation method and application. Background Technology

[0002] Advanced oxidation processes, such as Fenton oxidation, persulfate oxidation, and electrocatalytic oxidation, can generate highly reactive free radicals, such as hydroxyl radicals (·OH) and sulfate radicals (SO4·). - Electrocatalysis, including cathode-based electrocatalysis, is an effective strategy for removing high-risk organic pollutants such as bisphenol A from wastewater. Among these, cathode-based electrocatalysis primarily extracts reactive oxygen species from oxygen, eliminating the need for external chemical reagents and complex post-treatment steps, thus providing clean and efficient removal of high-risk organic pollutants from wastewater. With the continuous development of future energy systems, the carbon emission equivalent of electricity will gradually decrease. Compared to chemical oxidation, electrocatalysis will demonstrate enormous potential as a low-carbon wastewater treatment technology.

[0003] The electrocatalytic oxygen reduction process is complex, mainly consisting of two-electron reduction to hydrogen peroxide and four-electron reduction to water, accompanied by the generation of various reactive oxygen species. Even though the four-electron reaction pathway has the highest energy efficiency, water treatment relies on reactive oxygen species attacking organic pollutants. Furthermore, the hydrogen peroxide generated by the two-electron reaction can produce reactive oxygen species through Fenton or Fenton-like pathways. Therefore, adjusting electrode materials to enhance the selectivity of the two-electron process is crucial for improving electrocatalytic water treatment technology.

[0004] In recent years, transition metal (such as Fe, Co, and Ni) based catalysts have attracted widespread attention due to their abundant reserves and potential for high activity. Among them, atomically dispersed catalysts, with their highest atom utilization (approaching 100%), well-defined active sites, and unique electronic structures, have demonstrated excellent performance and great application potential in many catalytic reactions. However, the catalytic activity of a single atom is highly dependent on its local coordination environment. Although traditional carbon-nitrogen coordination modes are common, their ability to regulate the electronic structure of the metal center is limited, making it difficult to further optimize the adsorption energy of reaction intermediates, thus limiting the limits of catalytic performance. The catalytic performance of existing single-atom catalysts depends on the electronic structure of the atom, which in turn depends on the coordination environment. Since the synthesis of current single-atom electrocatalysts relies on high-temperature calcination, it is very difficult to synthesize single atoms with specific coordination environments. In summary, existing single-atom electrocatalysts have low hydrogen peroxide yields and struggle to simultaneously achieve good pH adaptability and two-electron selectivity. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a fullerene-modified nickel atom electrocatalyst synthesized without high-temperature calcination, its preparation method, and its application.

[0006] Technical solution: The fullerene-modified nickel atom electrocatalyst, wherein nickel and fullerene are linked through amino coordination.

[0007] Fullerenes are carbon allotropes with a unique zero-dimensional spherical structure, abundant electron systems, and well-defined molecular structures, making them suitable as functional modification units in catalysis. The electron-deficient cage-like structure of fullerenes enables strong interactions with metal centers, making them stable and ideal ligands for electronically modulating single metal atoms. This invention primarily relies on zero-dimensional fullerenes to regulate the atomic coordination environment. Under inert gas protection, fullerenes remain stable at high temperatures and exhibit excellent conjugated structures.

[0008] The preparation method includes the following steps:

[0009] (1) Fullerene modification: Fullerene is functionalized with ethylenediamine to make it rich in amino groups and soluble in water and organic reagents;

[0010] (2) Preparation of precursor: react dopamine with divalent nickel salts such as nickel chloride or nickel nitrate to form a first precursor in which nickel is coordinated with dopamine; use the first precursor to coordinate with the modified fullerene obtained in step (1) to form a second precursor;

[0011] (3) Preparation of electrocatalyst: Under the protection of inert gas, the second precursor is heated to pyrolyze and carbonize dopamine to obtain a fullerene-modified nickel atom electrocatalyst.

[0012] In step (2), the first precursor and the modified fullerene are preferably added at a fullerene:nickel element mass ratio of 0.5-5:1. The operating environment is preferably an organic solvent such as methanol or negative pressure to prevent dopamine from being oxidized. The negative pressure is preferably below 0.06 MPa.

[0013] In step (3), the heating temperature is preferably 320-420℃, and most preferably 400℃. This temperature allows dopamine to pyrolyze and carbonize without damaging the fullerene structure.

[0014] Step (1) preferred: Weigh 0.1-1 mg / mL of fullerene and place it in ethylenediamine. Stir at 40-80℃ for 10-36 h until the fullerene is completely dissolved. After ultrasonic reaction for 1-5 h, remove the excess ethylenediamine completely in a rotary evaporator and dissolve it in methanol to achieve a final fullerene concentration of 10 mg / mL.

[0015] Step (2) preferred method: Weigh nickel chloride and dopamine (at a molar ratio of 1:1-5) and dissolve them in methanol. Control the amount of methanol added so that the mass concentration of nickel is 1-10 mg / mL. Stir for 10-36 h under a negative pressure of less than 0.06 MPa until nickel and dopamine have completed coordination. Add fullerene methanol solution at a mass ratio of fullerene:nickel = 1:1. Stir for 10-36 h under a negative pressure of less than 0.06 MPa until nickel and fullerene have completed coordination. Remove excess methanol completely using a rotary evaporator.

[0016] Step (3) preferred: Take the product from step (2), heat it to 400℃ at 5℃ / min under argon protection, keep it for 2 h, cool it to room temperature, and grind it thoroughly for later use.

[0017] The application is the electrocatalytic reduction of oxygen to produce hydrogen peroxide using the nickel atom electrocatalyst, including the following steps:

[0018] S1. Disperse the fullerene-modified nickel atom electrocatalyst in an ethanol-water solution of Nafion resin and sonicate until a uniform ink is formed.

[0019] S2. Apply the ink to the surface of the graphite electrode and allow it to air dry naturally to obtain the graphite electrode;

[0020] S3. Using a cylindrical electrochemical reactor, a three-electrode system is constructed with a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and the graphite electrode as the working electrode; electrolyte solutions such as sodium sulfate solution are added to the electrochemical reactor and oxygen is introduced; a constant potential is applied to the working electrode.

[0021] In step S3, the voltage of the constant potential is preferably -0.4 V to -1.5 V. The pH of the sample solution is preferably 1 to 11.

[0022] Step S1 is preferred: Prepare a solution of ethanol:water:Nafion resin = 5:4:1, weigh 10 mg / mL of the fullerene-modified nickel atom electrocatalyst and dissolve it in the above solution, and sonicate for 30 min until a uniform ink is formed.

[0023] Step S2 preferred: according to 0.25 mg / cm 2 Apply the ink evenly to the surface of the graphite electrode in the specified proportions, and allow it to air dry naturally before use.

[0024] Step S3 is optimized as follows: An electrocatalytic degradation experiment is conducted in a three-electrode system. The electrochemical reactor is a 100 mL cylindrical reactor. The counter electrode is a platinum sheet (10×10×0.1 mm), the reference electrode is Ag / AgCl, and the working electrode is a graphite electrode coated with a catalyst. All electrodes are spaced 2 cm apart. Sodium sulfate solution is added to the electrochemical reactor, and oxygen is aerated. The temperature is controlled at 30℃, the stirring speed at 500 rpm, and the oxygen aeration flow rate at 20 mL / min. A constant potential is applied to the working electrode using an electrochemical workstation.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] 1. The fullerene-modified nickel atom electrocatalyst exhibits high hydrogen peroxide yield, along with good pH adaptability and two-electron selectivity: the cumulative concentration of hydrogen peroxide generated by the fullerene-modified nickel atom electrocatalyst is significantly increased, reaching 86.3 mg / L after 1 h, while the hydrogen peroxide generated by the nickel atom electrode without fullerene is 28.8 mg / L; the fullerene-modified nickel atom electrocatalyst maintains a stable hydrogen peroxide production rate within the pH range of 1-11, demonstrating good pH adaptability; the electron transfer number of the fullerene-modified nickel atom electrocatalyst during the electrocatalytic process is close to 2, indicating good two-electron selectivity.

[0027] 2. The preparation method described above can stably produce high-performance nickel atom electrocatalysts, avoids the oxidation of dopamine, and does not require excessively high reaction temperatures, making it safer and more controllable. Attached Figure Description

[0028] Figure 1 A schematic diagram illustrating the effect of fullerene modification on the efficiency of nickel atom electrocatalysts in generating hydrogen peroxide;

[0029] Figure 2 A schematic diagram showing the hydrogen peroxide production of a fullerene-modified nickel atom electrocatalyst at different pH values.

[0030] Figure 3 A schematic diagram showing the hydrogen peroxide production of a fullerene-modified nickel atom electrocatalyst at different voltages;

[0031] Figure 4 KL curves for the electrocatalytic oxygen reduction process using a fullerene-modified nickel atom electrocatalyst;

[0032] Figure 5 A schematic diagram showing the hydrogen peroxide production of electrocatalysts obtained by modifying fullerenes with different transition metals.

[0033] Figure 6 A schematic diagram showing the electrocatalytic hydrogen peroxide production of electrocatalysts at different calcination temperatures;

[0034] Figure 7 The effect of fullerene modification on the removal efficiency of nickel atom electrocatalysts for bisphenol A. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] This embodiment provides a fullerene-modified nickel atom electrocatalyst, wherein nickel and fullerene are linked through amino coordination.

[0038] Example 2

[0039] This embodiment provides a method for preparing the fullerene-modified nickel atom electrocatalyst described in Example 1, the steps of which are as follows:

[0040] (1) Fullerene modification. 0.5 mg / mL of fullerene was weighed and placed in ethylenediamine. The mixture was stirred at 50 °C for 24 h until the fullerene was completely dissolved. After sonication for 1 h, excess ethylenediamine was completely removed in a rotary evaporator and dissolved in methanol to achieve a final fullerene concentration of 10 mg / mL.

[0041] (2) Preparation of the precursor. Weigh nickel chloride and dopamine (at a molar ratio of 1:4) and dissolve them in methanol. Control the amount of methanol added to ensure a nickel concentration of 5 mg / mL. Stir for 24 h under a negative pressure of less than 0.06 MPa until nickel and dopamine have completed coordination. Add fullerene to a methanol solution at a mass ratio of 1:1 (fullerene:nickel). Stir for 24 h under a negative pressure of less than 0.06 MPa until nickel and fullerene have completed coordination. Remove excess methanol completely using a rotary evaporator.

[0042] (3) Preparation of nickel atom electrocatalysts coordinated with fullerene: Take the product from the previous step, heat it to 400℃ at 5℃ / min under argon protection, keep it for 2 h, cool it to room temperature, and grind it thoroughly for later use.

[0043] Example 3

[0044] This embodiment provides another method for preparing the fullerene-modified nickel atom electrocatalyst described in Example 1. The steps are basically the same as those in Example 2, except that in step (1), 1 mg / mL of fullerene is weighed and placed in ethylenediamine, and stirred at 80°C for 12 h.

[0045] Example 4

[0046] This embodiment provides another method for preparing the fullerene-modified nickel atom electrocatalyst described in Example 1. The steps are basically the same as in Example 2, except that in step (2), a fullerene methanol solution is added at a mass ratio of fullerene to nickel of 4:1.

[0047] Example 5

[0048] This embodiment provides the application of the fullerene-modified nickel atom electrocatalyst described in Example 1 in the generation of hydrogen peroxide, and the steps are as follows:

[0049] S1. Prepare a solution of ethanol:water:Nafion resin = 5:4:1. Weigh 10 mg / mL of the catalyst prepared in Example 1 and dissolve it in the above solution. Sonicate for 30 min until a uniform ink is formed.

[0050] S2, according to 0.25mg / cm 2 Apply the ink evenly to the surface of the graphite electrode in the specified proportions, and allow it to air dry naturally before use.

[0051] S3. Electrocatalytic degradation experiments were conducted in a three-electrode system. The electrochemical reactor was a 100 mL cylindrical reactor. The counter electrode was a platinum sheet (10×10×0.1 mm), the reference electrode was Ag / AgCl, and the working electrode was a graphite electrode coated with catalyst. All electrodes were spaced 2 cm apart. Sodium sulfate solution was added to the electrochemical reactor, and oxygen was aerated. The temperature was controlled at 30℃, the stirring speed at 500 rpm, and the oxygen aeration flow rate at 20 mL / min. A constant potential was applied to the working electrode using an electrochemical workstation, with the voltage set to -1 V. After 1 hour, the concentration of hydrogen peroxide produced was measured. 200 μL of potassium phthalate (0.1 M) and 200 μL of potassium iodide reagent (0.4 M potassium iodide, 0.06 M NaOH, 0.1 mM ammonium molybdate) were added to 400 μL of sample. After 1 h of reaction, the absorbance at 351 nm was measured to quantify the hydrogen peroxide.

[0052] Test results: such as Figure 1 As shown, the hydrogen peroxide production concentration of the fullerene-modified nickel atom electrocatalyst described in Example 1 is 86.3 mg / L, which is much higher than that of the electrode without fullerene (28.8 mg / L), indicating that the addition of fullerene significantly improves the yield of hydrogen peroxide produced by nickel atom electrocatalysis of oxygen reduction.

[0053] Example 6

[0054] This embodiment is based on the application of Example 5, and tests the pH adaptability of the fullerene-modified nickel atom electrocatalyst described in Example 1. Test method: Before applying the potential in S3, the pH of the sample solution is adjusted to 1, 3, 5, 7, 9, and 11 with 0.1 M sodium hydroxide or 0.1 M sulfuric acid, and the test is started after stabilizing for 10 min.

[0055] Test results: such as Figure 2 As shown, fullerene-modified nickel atoms have good pH adaptability and can be used in water systems with pH = 1-11.

[0056] Example 7

[0057] This embodiment is based on the application of Example 5, and tests the voltage adaptability of the fullerene-modified nickel atom electrocatalyst described in Example 1. Test method: Change the set voltage in S3 to -1.0, -0.8, -0.7, -0.6, -0.5, and -0.4 V.

[0058] Test results: such as Figure 3 As shown, under voltage conditions below -0.4 V, fullerene-modified nickel atoms can efficiently electrocatalyze the reduction of oxygen to produce hydrogen peroxide.

[0059] Example 8

[0060] This embodiment is based on the application of Example 5, and detects the number of electrons transferred in the fullerene-modified nickel atom electrocatalyst described in Example 1.

[0061] Test results: such as Figure 4 As shown, the electron transfer number of fullerene-modified nickel atoms in the electrocatalytic oxygen reduction process is 2.25, indicating that oxygen tends to undergo two-electron reduction to produce hydrogen peroxide.

[0062] Comparative Example 1

[0063] This comparative study investigated the effect of metal centers on the electrocatalytic reduction of oxygen to produce hydrogen peroxide. Based on the preparation method of Example 2, nickel in step (2) was replaced with other transition metals: iron, cobalt, copper, and zinc, to prepare fullerene-modified transition metal atom electrocatalysts. The hydrogen peroxide yield of different metal centers was compared with the application method of Example 5.

[0064] The results are as follows Figure 5 As shown, nickel atom centers exhibit the best electrocatalytic hydrogen peroxide yield compared to metal centers such as iron, cobalt, copper, and zinc.

[0065] Comparative Example 2

[0066] This comparative example investigates the effect of heating temperature in step (3) of the preparation method on the fullerene-modified nickel atom electrocatalyst. The steps are basically the same as in Example 2, except that in step (3), the temperature is raised to 900℃.

[0067] The results are as follows Figure 6 As shown, under calcination conditions of 900℃, the concentration of hydrogen peroxide produced at 60 min was only 24.3 mg / L, which is lower than that under calcination conditions of 400℃.

[0068] Comparative Example 3

[0069] This comparative study investigated the effect of the ratio of fullerene to nickel in step (2) of the preparation method on the fullerene-modified nickel atom electrocatalyst. The steps were basically the same as in Example 2, except that in step (2), a fullerene methanol solution was added at a mass ratio of fullerene to nickel of 0.1:1. The effect of the prepared fullerene-modified nickel atom electrocatalyst on the production of hydrogen peroxide was detected, and the detection method was the same as in Example 5.

[0070] The results showed that the hydrogen peroxide production concentration of the prepared catalyst was 29.7 mg / L, which was only slightly higher than that of the electrode without fullerene, proving that the above ratio could not produce a high-performance fullerene-modified nickel atom electrocatalyst.

[0071] Example 9

[0072] This embodiment provides the application of the fullerene-modified nickel atom electrocatalyst described in Example 1 in the removal of bisphenol A, and the steps are as follows:

[0073] S1. Prepare a solution of ethanol:water:Nafion resin = 5:4:1. Weigh 10 mg / mL of the catalyst prepared in Example 1 and dissolve it in the above solution. Sonicate for 30 min until a uniform ink is formed.

[0074] S2, according to 0.25mg / cm 2 Apply the ink evenly to the surface of the graphite electrode in the specified proportions, and allow it to air dry naturally before use.

[0075] S3. Electrocatalytic degradation experiments were conducted in a three-electrode system. The electrochemical reactor was a 100 mL cylindrical reactor. The counter electrode was a platinum sheet (10×10×0.1 mm), the reference electrode was Ag / AgCl, and the working electrode was a graphite electrode coated with catalyst. All electrodes were spaced 2 cm apart. Sodium sulfate solution and 5 mg / L bisphenol A were added to the electrochemical reactor, and oxygen was aerated. The temperature was controlled at 30℃, the stirring speed at 500 rpm, and the oxygen aeration flow rate at 20 mL / min. A constant potential was applied to the working electrode using an electrochemical workstation, with the voltage set to -1 V. After 1 hour, the residual concentration of bisphenol A was measured. Bisphenol A was quantified by liquid chromatography using acetonitrile:water = 70:30 as the mobile phase. The excitation wavelength of the fluorescence detector was 275 nm, and the emission wavelength was 315 nm.

[0076] Test results: such as Figure 7 As shown, the bisphenol A removal rate of the fullerene-modified nickel atom electrocatalyst described in Example 1 was 46%, which was much higher than that of the electrode without fullerene (24%), indicating that the addition of fullerene significantly improved the performance of nickel atom electrocatalysis for oxygen activation to remove bisphenol A.

Claims

1. A fullerene-modified nickel atom electrocatalyst, characterized in that, Nickel is linked to fullerenes via amino coordination.

2. A method for preparing the nickel atom electrocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Fullerene modification: Fullerene is functionalized with ethylenediamine to make it rich in amino groups and soluble in water and organic reagents; (2) Preparation of precursor: reacting divalent nickel salt with dopamine to form a first precursor coordinated with nickel and dopamine; using the first precursor to coordinate with the modified fullerene obtained in step (1) to form a second precursor; (3) Preparation of electrocatalyst: Under the protection of inert gas, the second precursor is heated to pyrolyze and carbonize dopamine to obtain a fullerene-modified nickel atom electrocatalyst.

3. The preparation method according to claim 2, characterized in that, In step (2), the first precursor and the modified fullerene are added at a mass ratio of fullerene: nickel = 0.5-5:

1.

4. The preparation method according to claim 2, characterized in that, In step (3), the heating temperature is 320-420℃.

5. The preparation method according to claim 2, characterized in that, The operating environment for step (2) is an organic solvent or negative pressure.

6. The preparation method according to claim 5, characterized in that, The negative pressure is below 0.06 MPa.

7. The application of the nickel atom electrocatalyst of claim 1 in the electrocatalytic reduction of oxygen to produce hydrogen peroxide.

8. The application according to claim 7, characterized in that, The generation of hydrogen peroxide includes the following steps: S1. Disperse the fullerene-modified nickel atom electrocatalyst in an ethanol-water solution of Nafion resin and sonicate until a uniform ink is formed. S2. Apply the ink to the surface of the graphite electrode and allow it to air dry naturally to obtain the graphite electrode; S3. Using a cylindrical electrochemical reactor, a three-electrode system is constructed with a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and the graphite electrode coated with the catalyst as the working electrode; an electrolyte solution is added to the electrochemical reactor and oxygen is introduced; a constant potential is applied to the working electrode.

9. The application according to claim 8, characterized in that, In step S3, the voltage of the constant potential is -0.4 V to -1.5 V.

10. The application according to claim 8, characterized in that, In step S3, the pH of the sample solution is 1~11.

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