Asymmetric metal monatomic electrocatalyst and its application in electrochemical production of hydrogen peroxide
By constructing an asymmetric NiB2N2 single-atom catalyst and utilizing boron doping to adjust the microenvironment of the metal sites, the problem of low two-electron selectivity of nickel single-atom electrocatalysts in oxygen reduction reaction was solved, achieving efficient hydrogen peroxide generation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TONGJI UNIV
- Filing Date
- 2025-01-02
- Publication Date
- 2026-07-31
AI Technical Summary
In existing technologies, nickel single-atom electrocatalysts exhibit low two-electron selectivity in oxygen reduction reactions, making it difficult to achieve efficient hydrogen peroxide production and failing to meet practical application requirements.
By constructing an asymmetric NiB2N2 single-atom catalyst, boron doping is used to adjust the microenvironment of the metal sites, enhance the local electric field, and promote the activation process of molecular oxygen, thereby achieving efficient two-electron selective generation of hydrogen peroxide.
It achieves a Faraday efficiency of up to 90% in an alkaline environment, demonstrating excellent electrocatalytic performance and high 2e-H2O2 selectivity, thus meeting the demand for economical and flexible hydrogen peroxide production.
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Figure CN119800409B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrode preparation technology, and in particular to an asymmetric metal single-atom electrocatalyst and its application in the electrochemical production of hydrogen peroxide. Background Technology
[0002] Hydrogen peroxide (H2O2) is an environmentally friendly chemical reagent that can be used as both an oxidant and a reducing agent, and is widely used in various industrial fields, such as organic synthesis, wastewater treatment, bleaching, and disinfection. Currently, the industrial production of H2O2 mainly relies on the anthraquinone redox process; however, this process suffers from high cost, high energy consumption, and the generation of organic waste. Therefore, developing more economical, efficient, and environmentally friendly H2O2 production technologies has become a research hotspot. In recent years, electrocatalysis, photocatalysis, and enzyme-based catalysis processes have been extensively explored, among which the electrocatalytic two-electron oxygen reduction reaction (2e...) is particularly promising. - ORR (Organic Anthraquinone Regeneration) is a green method for producing H2O2, exhibiting good selectivity and activity. Compared with traditional anthraquinone processes, this method operates under environmental conditions, demonstrating greater environmental friendliness and providing a feasible alternative for sustainable H2O2 production.
[0003] Developing highly active and selective electrocatalysts for the electrocatalytic production of H₂O₂ remains a significant challenge. Noble metal-based nanoalloy catalysts show promising potential due to the ability to optimize the binding energy during alloying. However, their high cost casts doubt on their economic viability. In contrast, non-noble metal-based transition metal catalysts (such as metal nanoparticles, metal oxides, and metal selenides) have been widely explored, but often fail to achieve ideal results due to their catalytic decomposition of H₂O₂ during the reaction. Carbon-based materials are also considered promising candidates, but their complex surface chemistry (such as the presence of various functional groups like ethers, hydroxyl groups, carbonyl groups, carboxyl groups, quinones, and other main group elements) makes the reaction mechanism difficult to elucidate and limits the possibility of further activity optimization. Single-atom catalysts (SACs), especially those with M-N₄ or M-N₅ structures, have shown great potential in the photoelectrochemical activation of molecular oxygen to produce H₂O₂. Through atomic-level structural modulation, these catalysts can effectively decipher the structure-performance relationship of electrocatalysts, leading to a deeper understanding of the reaction mechanism. Studies have shown that, compared to pyridine coordination, the active center of pyrrole coordination is more inclined to selectively generate H2O2 via the 2e- pathway. Summary of the Invention
[0004] It is worth noting that while the traditional symmetrical MN4 configuration exhibits high efficiency in oxygen reduction, its symmetry results in a weak local electric field, making it difficult to effectively activate molecular oxygen. To enhance the external electric field, constructing asymmetric coordination microenvironments with high polarity is a potentially feasible strategy. Ideally, by doping with non-metallic heteroatoms (such as sulfur, phosphorus, and boron), the local environment of the carbon substrate can be modulated, thereby enhancing its polarity. Since boron and nitrogen have similar atomic radii, boron doping typically partially replaces the N atom in the covalent substrate and directly coordinates with metal atoms, thus altering the catalyst configuration. Due to the significant difference in electronegativity between boron and carbon, this alteration can significantly increase the strength of the local electric field, providing additional driving force for the reaction system. Through this asymmetric structure, the proton-coupled electron transfer process of molecular oxygen (*OOH) can be promoted at a lower energy barrier, further selectively generating H₂O₂.
[0005] To address the problem that existing nickel single-atom electrocatalysts exhibit low two-electron selectivity in most oxygen reduction reactions, making it difficult to achieve selectivity control from four-electron to two-electron, thus resulting in low hydrogen peroxide yield and failing to meet the demand for efficient hydrogen peroxide production in practical applications, this invention provides an asymmetric single-atom metal catalyst and its application in electrochemical hydrogen peroxide production. This invention constructs a NiB₂N₂ single-atom catalyst by regulating the microenvironment of the single-atom Ni site through the coordination of the first shell of B and N. The prepared NiB₂N₂ catalyst exhibits excellent ORR activity and high 2e-H₂O₂ selectivity in an alkaline environment. In solid-state electrolyte electrolysis cell tests, this catalyst achieved a Faradaic efficiency of up to 90%, demonstrating excellent electrocatalytic performance.
[0006] The first objective of this invention is to provide a method for preparing an asymmetric metal single-atom electrocatalyst, comprising the following steps:
[0007] (1) The zinc precursor and the metal precursor are mixed in a solvent to obtain solution A; the nitrogen source is dissolved in the solvent to obtain solution B; solution A and solution B are mixed and heated to obtain the metal nitrogen precursor;
[0008] (2) The metal nitrogen precursor and the boron source are mixed and ball-milled, and then heated and calcined under an inert atmosphere. The calcined material is then acidified in an acid solution to obtain an asymmetric metal single-atom electrocatalyst.
[0009] In some embodiments of the present invention, in step (1), the zinc precursor is selected from one or more of zinc nitrate, zinc acetate, and zinc sulfate;
[0010] The metal precursor is one of nickel, copper, cobalt, and iron; more preferably, nickel.
[0011] The salt in the metal precursor is selected from one or more of nitrates, sulfates, and chlorides.
[0012] In some embodiments of the present invention, in step (1), the nitrogen source is selected from one or more of dimethylimidazole, acetonitrile, and urea;
[0013] The metal nitrogen precursor includes one or more of zeolite imidazole ester metal, zeolite imidazole ester zinc, and zeolite imidazole ester metal / zinc.
[0014] In some embodiments of the present invention, the mass ratio of the metal precursor to the boron source is (1-10):(1-10).
[0015] In some embodiments of the present invention, in step (1), the mass ratio of zinc precursor, metal precursor and nitrogen source is 10:(0.1-3):(100-500).
[0016] In some embodiments of the present invention, in step (1), the heating reaction temperature is 25-60°C, and the reaction time is 8-24 hours. After the heating reaction, the product is dried using vacuum drying for 10-24 hours.
[0017] In some embodiments of the present invention, in step (2), the boron source is selected from boric acid and / or borate.
[0018] In some embodiments of the present invention, in step (2), the heating and calcination conditions are as follows: heating temperature is 700℃~900℃, constant temperature time is 1-6h, and heating rate is 1~10℃·min. -1 ;
[0019] In an inert atmosphere, the inactive gas is selected from argon and / or nitrogen.
[0020] Furthermore, the heating and calcination are carried out using a tube furnace.
[0021] In some embodiments of the present invention, in step (2), the acid is selected from one or more of sulfuric acid, hydrochloric acid, and nitric acid; the present invention removes non-monoatomic metal clusters by acid washing, thereby forming a metal monoatomic catalyst.
[0022] The acidification treatment temperature is 20-90℃, and the acidification treatment time is 4-12h;
[0023] The concentration of the acid solution is 0.1-6.0 mol / L.
[0024] In some embodiments of the present invention, step (2) after acidification further includes drying, wherein the drying method is vacuum drying; and the drying time is 10-24 hours.
[0025] A second objective of this invention is to provide an asymmetric single-atom metal catalyst, prepared by the aforementioned method, wherein the asymmetric single-atom metal catalyst is MB. m N n Where 0 ≤ m ≤ 4, 0 ≤ n ≤ 4, m + n ≤ 4, m and n are integers, and M is one of nickel, cobalt, copper, and iron. For example, m is 0, 1, 2, or 3, and n is 0, 1, 2, or 3. Preferably, MB m N n The terms are MB2N2, MBN3, MB3N1, MB2N2, etc., except for MB4 and MN4, where m and n are not both 0.
[0026] Furthermore, the metal loading in the asymmetric metal single-atom electrocatalyst is 0.5-3.5 wt%; the boron loading is 0.3-7 wt%.
[0027] A third objective of this invention is to provide the asymmetric metal single-atom electrocatalyst in the fields of electrochemical selective hydrogen peroxide production and electrochemical water pollution control.
[0028] The technical solution of the present invention has the following advantages compared with the prior art:
[0029] 1. This invention provides an asymmetric metal single-atom electrocatalyst, wherein the mass fraction of the single-atom metal in the asymmetric metal single-atom electrocatalyst is 0.5-3.5%. The asymmetric metal single-atom electrocatalyst provided by this invention exhibits high ORR activity, high two-electron selectivity for catalytic H2O2 production, high Faraday efficiency, simple preparation method, and good electrocatalytic performance and electrochemical stability.
[0030] 2. Compared with traditional nickel-nitrogen catalysts, the asymmetric metal single-atom electrocatalyst provided by this invention exhibits higher 2e content in the integrated single-atom nickel single-atom electrocatalyst. - The oxygen reduction selectivity was increased from 30% to 90%, realizing the transformation from a four-electron to a two-electron oxygen reduction process.
[0031] 3. The asymmetric metal single-atom electrocatalyst provided by this invention, wherein boron and nitrogen have similar atomic radii but significantly different electronegativity, boron doping typically partially replaces the N atom in the covalent substrate and directly coordinates with the metal atom, thereby altering the catalyst configuration. This change can significantly increase the intensity of the local electric field, providing additional driving force for the reaction system. Through this asymmetric structure, the activation process of molecular oxygen (*OOH) and the proton-coupled electron transfer process can be promoted at a lower energy barrier, further selectively generating H2O2.
[0032] 4. This invention provides a method for preparing the above-mentioned asymmetric metal single-atom electrocatalyst, comprising the following steps: (1) mixing, reacting, and drying a nitrogen-containing heterocyclic organic compound, a zinc precursor, sodium carbonate, a nickel precursor, and methanol to obtain a nickel-nitrogen precursor; (2) mixing and ball-milling the nickel-nitrogen precursor and boric acid, followed by calcination, acidification, and drying to obtain a nickel single-atom electrocatalyst. Acidification treatment can remove elemental nickel and nickel oxides, thereby improving the two-electron selectivity in the oxygen reduction process.
[0033] 5. This invention also provides the application of an asymmetric metal single-atom electrocatalyst, or a nickel single-atom electrocatalyst prepared using this method, in hydrogen peroxide production. The electrocatalyst provided by this invention meets the demand for economical, flexible, and sustainable hydrogen peroxide production, enabling its implementation in remote communities and regions. Attached Figure Description
[0034] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...
[0035] Figure 1 This is a spherical aberration electron microscope image of the catalyst prepared in this invention.
[0036] Figure 2 This is a two-electron oxygen reduction selectivity diagram of the catalysts prepared by the embodiments and comparative examples of the present invention, as tested by a rotating disk. Detailed Implementation
[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0038] Example 1
[0039] This embodiment provides an asymmetric nickel single-atom electrocatalyst, wherein the mass fraction of nickel single atoms in the electrocatalyst is 3.00±0.2%, and the boron content is 2.00±0.2%. The preparation method specifically includes the following steps:
[0040] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0041] (2) Mix 500 mg of dried NiZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1 The samples were heated to 700℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a forced-air drying oven at 60℃ to obtain the NiB2N2 catalyst.
[0042] Example 2
[0043] This embodiment provides a nickel single-atom electrocatalyst, wherein the mass fraction of nickel single atoms in the electrocatalyst is 3.00±0.2% and the mass fraction of boron is 0.7%. The preparation method specifically includes the following steps:
[0044] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0045] (2) Mix 500 mg of dried NiZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1The samples were heated to 800℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a 60℃ forced-air drying oven to obtain the nickel single-atom electrocatalyst NiBN3 catalyst.
[0046] Example 3
[0047] This embodiment provides a nickel single-atom electrocatalyst, wherein the mass fraction of nickel single atoms in the electrocatalyst is 3.00±0.2% and the mass fraction of boron is 0.2%. The preparation method specifically includes the following steps:
[0048] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0049] (2) Mix 500 mg of dried NiZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1 The samples were heated to 900℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a forced-air drying oven at 60℃ to obtain the NiN3-B catalyst.
[0050] Example 4
[0051] This embodiment provides a cobalt single-atom electrocatalyst, wherein the mass fraction of cobalt single atoms in the electrocatalyst is 3.00 ± 0.2%, and the mass fraction of boron is 0.6%. The preparation method specifically includes the following steps:
[0052] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Co(NO3)2·6H2O (2.095 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and dried under vacuum at 60 °C overnight to obtain the CoZn-ZIF-8 precursor.
[0053] (2) Mix 500 mg of dried CoZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1 The samples were heated to 700℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a 60℃ forced-air drying oven to obtain the cobalt single-atom electrocatalyst CoB2N2 catalyst.
[0054] Example 5
[0055] This embodiment provides an iron single-atom electrocatalyst, wherein the mass fraction of single-atom iron is 3.00±0.2% and the mass fraction of boron is 2.0%. The preparation method specifically includes the following steps:
[0056] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Fe(NO3)2·9H2O (2.909 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and dried under vacuum at 60 °C overnight to obtain the FeZn-ZIF-8 precursor.
[0057] (2) Mix 500 mg of dried FeZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1The samples were heated to 700℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a 60℃ forced-air drying oven to obtain the FeB2N2 catalyst.
[0058] Example 6
[0059] This embodiment provides a copper single-atom electrocatalyst, wherein the mass fraction of copper single atoms in the electrocatalyst is 3.00±0.2%, and the mass fraction of boron is 0.5%. The preparation method specifically includes the following steps:
[0060] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Cu(NO3)2·3H2O (1.739 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and dried under vacuum at 60 °C overnight to obtain the CuZn-ZIF-8 precursor.
[0061] (2) Mix 1000 mg of dried CuZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1 The samples were heated to 700℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a forced-air drying oven at 60℃ to obtain the CuB2N2 catalyst.
[0062] Comparative Example 1 (no acidification treatment was performed compared to Example 1)
[0063] This comparative example provides a nickel nanoparticle electrocatalyst, wherein the nickel mass fraction is 3.00 ± 0.2% and the boron mass fraction is 0.5%. The preparation method specifically includes the following steps:
[0064] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0065] (2) Mix 500 mg of dried NiZn-ZIF-8 precursor with 50 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1 The samples were heated to 700, 800, and 900 °C at varying heating rates, and held at this temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting materials were washed with deionized water until neutral, and then dried in a 60 °C forced-air drying oven to obtain the NiB2N2 catalyst.
[0066] Comparative Example 2 (compared to Example 1, the mass ratio of nickel-nitrogen precursor to boron source is not within the protection range)
[0067] This comparative example provides a nickel single-atom electrocatalyst, wherein the mass fraction of nickel single atoms is 3.00 ± 0.2% and the mass fraction of boron is 1.7%. The preparation method specifically includes the following steps:
[0068] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0069] (2) Mix 500 mg of dried NiZn-ZIF-8 precursor with 25 mg of boric acid and ball mill for 1 h. Then transfer the mixed powder to a ceramic boat and place it in a tube furnace. Heat at 5 °C·min -1The samples were heated to 800℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a 60℃ forced-air drying oven to obtain the NiB3N1 catalyst.
[0070] Comparative Example 3
[0071] This comparative example provides a nickel single-atom electrocatalyst, wherein the mass fraction of single-atom nickel in the nickel single-atom electrocatalyst is 3.00±0.2%, and the preparation method specifically includes the following steps:
[0072] (1) Zn(NO3)2·6H2O (21.419 g, 72 mmol) and Ni(NO3)2·6H2O (2.093 g, 7.2 mmol) were dissolved in 100 mL of methanol and stirred for 15 minutes with ultrasonic assistance to form a clear solution A. Then, dimethylimidazole (23.644 g, 288 mmol) was dissolved in 100 mL of methanol by ultrasonication, and this solution was designated as solution B. Solution A was then slowly added dropwise to solution B, and the reaction was heated at 60 °C for 12 hours. After the reaction was completed, the product was separated by centrifugation, washed three times with DMF and twice with methanol, and then vacuum dried overnight at 60 °C to obtain the NiZn-ZIF-8 precursor.
[0073] (2) Transfer 500 mg of the dried NiZn-ZIF-8 precursor to a ceramic boat and place it in a tube furnace. Heat at 5 °C / min. -1 The samples were heated to 700℃ at a controlled heating rate and held at that temperature for 2 hours under an argon atmosphere, followed by natural cooling to room temperature. The resulting material was acid-washed in 3M H2SO4 at 80℃ for 4 hours, then filtered and washed with deionized water until neutral, and dried in a 60℃ forced-air drying oven to obtain the nickel single-atom electrocatalyst NiN4 catalyst.
[0074] Test Example 1
[0075] The electrodes prepared in Examples 1-6 and Comparative Examples 1-3 were subjected to performance tests, specifically testing the yield of hydrogen peroxide. The specific test methods are as follows:
[0076] Selectivity test method for hydrogen peroxide: The electrodes prepared in Examples 1-6 and Comparative Examples 1-3 were ground, and then 0.4 mL of 0.05% naphthol solution was added to a container containing 2 mg of catalyst powder. The mixture was ultrasonically dispersed for 10 min. 10 μL of the mixed solution was pipetted onto the surface of a rotating disk electrode and then allowed to air dry at room temperature before electrochemical testing. The counter electrode was a platinum wire, the reference electrode was a saturated calomel electrode, and the electrolyte solution was 0.1 M KOH. The rotating disk electrode test was performed using an electrochemical workstation. Before the electrochemical test, oxygen was continuously introduced into the electrolyte solution for 20–30 min at a flow rate of 100.0 mL / min. After oxygen saturation, a linear sweep voltammetric curve of the rotating disk was performed. The test results are shown in Table 1 below.
[0077] Table 1
[0078] Example 1 92 Example 2 70 Example 3 65 Example 4 72 Example 5 64 Example 6 61 Comparative Example 1 12 Comparative Example 2 34 Comparative Example 3 58
[0079] Conclusion: The electrodes prepared in Examples 1-6 and Comparative Examples 1-3 were tested by rotating disk electrode experiments. The two-electron selectivity was calculated to be between 90% and 55%. The optimal sample, Example 1, had a selectivity of 90%, which was much higher than that of the nickel-carbon based catalyst.
[0080] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing an asymmetric metal single-atom electrocatalyst, characterized in that, Includes the following steps: (1) The zinc precursor and the metal precursor are mixed in a solvent to obtain solution A; the nitrogen source is dissolved in the solvent to obtain solution B; solution A and solution B are mixed and heated to obtain the metal nitrogen precursor; (2) The metal nitrogen precursor and the boron source are mixed and ball-milled, and then heated and calcined under an inert atmosphere. The calcined material is then acidified in an acid solution to obtain an asymmetric metal single-atom electrocatalyst. The metal precursor is one of nickel, copper, cobalt, and iron. The nitrogen source is selected from dimethylimidazole; The mass ratio of zinc precursor, metal precursor and nitrogen source is 10:(0.1-3):(100-500). The mass ratio of the metal precursor to the boron source is (1-10):(1-10).
2. The production method according to claim 1, characterized by, In step (1), the zinc precursor is selected from one or more of zinc nitrate, zinc acetate, and zinc sulfate; The salt in the metal precursor is selected from one or more of nitrates, sulfates, and chlorides.
3. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the heating reaction is 25-60℃ and the reaction time is 8-24h.
4. The method of claim 1, wherein, In step (2), the boron source is selected from boric acid and / or borate.
5. The preparation method according to claim 1, characterized in that, In step (2), the heating and calcination conditions are as follows: heating temperature is 700℃~900℃, constant temperature time is 1-6h, and heating rate is... ; In an inert atmosphere, the inactive gas is selected from argon and / or nitrogen.
6. The method of claim 1, wherein, In step (2), the acid is selected from one or more of sulfuric acid, hydrochloric acid, and nitric acid; The acidification treatment temperature is 20-90℃, and the acidification treatment time is 4-12h; The concentration of the acid solution is 0.1-6.0 mol / L.
7. An asymmetric metal monatomic electrocatalyst characterized in that, The asymmetric metal single-atom electrocatalyst prepared by the preparation method according to any one of claims 1 to 6 is MB. m N n Where m is 1 or 2, n is 2 or 3, m+n=4, and M is one of nickel, copper, cobalt, and iron.
8. The asymmetric metal monatomic electrocatalyst of claim 7, wherein, The metal loading in the asymmetric metal single-atom electrocatalyst is 0.5-3.5 wt%; the boron loading is 0.3-7 wt%.
9. The application of the asymmetric metal single-atom electrocatalyst as described in claim 7 or 8 in electrochemical selective hydrogen peroxide production and electrochemical water pollution control.