Nitrogen / phosphorus co-doped fullerene material as well as preparation method and application thereof

Abstract

The invention discloses a nitrogen / phosphorus co-doped fullerene material and a preparation method and application thereof.The nitrogen / phosphorus co-doped fullerene material is composed of fullerene, melamine and ammonium hypophosphite, the fullerene serves as a carbon skeleton precursor to form a rich pentagonal topological defect structure in the high-temperature pyrolysis process, and the nitrogen / phosphorus co-doped fullerene material is obtained; melamine and ammonium hypophosphite are respectively used as a nitrogen source and a phosphorus source, are decomposed at a high temperature and are uniformly doped with nitrogen and phosphorus atoms in a carbon skeleton. The method comprises the following steps: dissolving fullerene in carbon disulfide, adding melamine, uniformly mixing, heating until the carbon disulfide is completely volatilized, adding an ammonium hypophosphite solution, and pyrolyzing in an inert atmosphere to obtain the nitrogen / phosphorus co-doped fullerene material. The electrocatalyst provided by the invention has a relatively large specific surface area, can provide more active sites, and also can provide higher mass transfer efficiency and HO selectivity due to rich pores and a topological defect structure, so that the oxygen reduction reaction rate can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic synthesis of hydrogen peroxide, and in particular to a nitrogen / phosphorus co-doped fullerene material and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2), also known as hydrogen peroxide, is a chemical with remarkable oxidizing power. Its green, pollution-free nature and wide range of applications have made it an indispensable chemical in modern society. From pulp bleaching to medical disinfection to the degradation of environmental pollutants, hydrogen peroxide, with its unique chemical properties, plays a key role in industrial production and daily life. Currently, the anthraquinone method is the primary method for large-scale industrial production of hydrogen peroxide. While this production process is mature and well-established, it also has significant drawbacks, such as complex processes, high energy consumption, high pollution, and high costs. Alternatively, the direct catalytic synthesis of H2O2 using hydrogen and oxygen over precious metal catalysts such as palladium offers advantages such as simplicity, low production costs, and atom economy. However, the hydrogen-oxygen mixture reaction is thermodynamically exothermic, posing a risk of explosion. Consequently, the search for alternative methods for hydrogen peroxide synthesis that are both low-cost, environmentally friendly, resource-efficient, and sustainable is underway.

[0003] In recent years, electrochemical methods, especially through the two-electron oxygen reduction reaction (2e − The technology of producing hydrogen peroxide by ORR (two-electron oxygen reduction reaction) has attracted widespread attention due to its advantages such as high hydrogen peroxide synthesis efficiency, economic safety, and environmental friendliness. The key to two-electron oxygen reduction is to design high-performance catalysts with good activity, high selectivity, and long-term stability. Noble metals and their alloys (such as Pt-Hg, Pd-Hg, and AuPd) are currently considered to be efficient 2e − ORR catalysts have small overpotential and high selectivity, but their large-scale application is greatly limited by their shortcomings such as resource scarcity, high cost and poor stability. Carbon materials have attracted widespread attention from researchers due to their many advantages such as excellent conductivity, controllable structure, abundant resources and low cost. Biomass resources are abundant and widely available, which can not only provide rich carbon sources and heteroatoms, but also biomass can easily form a porous structure after pyrolysis and post-treatment due to the characteristics of its own structure. Therefore, seeking a suitable method to process biomass to prepare carbon-based nanomaterial electrocatalysts with high ORR activity and high H2O2 selectivity, thereby achieving the dual goals of environmental protection and biomass value-added, has become one of the problems that need to be solved urgently. Summary of the Invention

[0004] The present invention aims to provide a nitrogen / phosphorus co-doped fullerene material, its preparation method, and its application. This material can produce a porous structure with abundant active sites while achieving efficient two-electron oxygen reduction reaction selectivity, thereby obtaining a highly efficient nitrogen / phosphorus co-doped fullerene material and improving the performance of carbon-based nanomaterial electrocatalysts for electrochemical H2O2 production.

[0005] In one aspect, the present invention proposes a nitrogen / phosphorus co-doped fullerene material. According to an embodiment of the present invention, the material is composed of fullerene, melamine, and ammonium hypophosphite. Fullerene, as a carbon skeleton precursor, forms a rich pentagonal topological defect structure during high-temperature pyrolysis. Melamine and ammonium hypophosphite serve as nitrogen sources (taking advantage of their high nitrogen content and controllable pyrolysis behavior) and phosphorus sources (taking advantage of their high reactivity and doping uniformity), respectively. Melamine decomposes at high temperatures and uniformly dopes nitrogen and phosphorus atoms into the carbon skeleton, forming highly active catalytic sites.

[0006] In another aspect of the present invention, a method for preparing nitrogen / phosphorus co-doped fullerene materials is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0007] (1) Fullerene is dissolved in carbon disulfide, and then melamine is added and mixed uniformly to obtain a mixture A;

[0008] (2) heating the mixture A until the carbon disulfide in the mixture A is completely volatilized, adding the ammonium hypophosphite solution to the mixture A, ultrasonically treating the mixture, and then drying to obtain a precursor mixture;

[0009] (3) The precursor mixture is placed in an inert atmosphere for pyrolysis to obtain the nitrogen / phosphorus co-doped fullerene material.

[0010] In addition, the method for preparing a nitrogen / phosphorus co-doped fullerene material according to the above embodiment of the present invention may also have the following additional technical features:

[0011] In some embodiments of the present invention, in step (1), the mass ratio of fullerene to melamine is 1:(30-50), and the use of a high proportion of nitrogen source can prevent pyrolysis loss and promote effective doping.

[0012] In some embodiments of the present invention, in step (2), the mass ratio of ammonium hypophosphite to fullerene is (2-6):1. Effective doping can be achieved by using a moderate ratio of phosphorus source, while an excessive amount will cause the structure to be destroyed.

[0013] In some embodiments of the present invention, in step (2), the heating temperature is 60-70°C.

[0014] In some embodiments of the present invention, in step (3), the inert atmosphere is argon, the pyrolysis temperature is 750-800°C, the time is 0.5-1h, and the heating rate is 10-15°C / min.

[0015] In some embodiments of the present invention, in step (3), after the pyrolysis is cooled, pickling and drying are performed, wherein the pickling is performed with 0.5-1 mol / L hydrochloric acid at a temperature of 60-80°C for 4-6 hours, and the drying is performed at a temperature of 60-70°C for 8-12 hours. Acid washing can remove impurities that have not been completely decomposed, thereby improving the purity of the material.

[0016] In another aspect, the present invention provides an application of a nitrogen / phosphorus co-doped fullerene material. According to an embodiment of the present invention, the nitrogen / phosphorus co-doped fullerene material is used as an electrocatalyst.

[0017] In addition, the application of a nitrogen / phosphorus co-doped fullerene-based material according to the above embodiment of the present invention may also have the following additional technical features:

[0018] In some embodiments of the present invention, the nitrogen / phosphorus co-doped fullerene-based material is used as an electrocatalyst in an electrocatalytic oxygen reduction reaction in a mobile electrolysis cell.

[0019] In some embodiments of the present invention, the electrocatalyst is used for electrosynthesis of hydrogen peroxide.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Compared with traditional carbon-based catalysts with insufficient ORR activity and poor H2O2 selectivity, the nitrogen / phosphorus co-doped fullerene material of the present invention has excellent ORR activity and high H2O2 selectivity. Through a simple one-step pyrolysis method, nitrogen / phosphorus co-doped fullerene material with rich topological defects was successfully prepared.

[0022] (2) The synergistic doping of nitrogen and phosphorus atoms effectively regulates the electronic structure of the carbon skeleton, forming a high-density active site and significantly improving the 2e⁻ ORR catalytic performance.

[0023] (3) In the process of preparing nitrogen / phosphorus co-doped fullerene materials, the present invention preferentially adds a nitrogen source. Nitrogen atoms are similar in size to carbon and easily replace carbon in fullerenes, forming stable C-N bonds, reducing structural strain, enhancing reactivity, and promoting subsequent phosphorus doping. Co-doping with nitrogen (high electronegativity) and phosphorus (low electronegativity) balances charge, improving material stability and performance.

[0024] (4) The nitrogen / phosphorus co-doped fullerene material of the present invention has a developed multi-level pore structure, which can promote the efficient mass transfer of O2 on the one hand, and provide a larger specific surface area on the other hand, thereby exposing more catalytic active sites and greatly improving the ORR reaction efficiency.

[0025] (5) The mesoporous structure enables 2e - The H2O2 generated by the ORR reaction quickly diffuses into the solution, preventing it from being further reduced to generate H2O2, which is beneficial to improving the H2O2 selectivity of the material, thereby greatly improving the efficiency of electrocatalytic production of hydrogen peroxide.

[0026] (6) Compared with precious metal catalysts, the nitrogen / phosphorus co-doped fullerene material of the present invention is low-cost and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a morphology image of the nitrogen / phosphorus co-doped fullerene material prepared in Example 1 of the present invention;

[0028] Figure 2 FIG1 is an LSV (linear sweep voltammetry) diagram of nitrogen / phosphorus co-doped fullerene materials in Examples 1 to 4 of the present invention;

[0029] Figure 3 The H2O2 selectivity and two-electron selectivity calculated for the nitrogen / phosphorus co-doped fullerene materials in Example 1 of the present invention and Comparative Example 1;

[0030] Figure 4 LSV (Linear Sweep Voltammogram) diagram of nitrogen / phosphorus co-doped fullerene materials in Example 1 of the present invention and Comparative Example 1;

[0031] Figure 5 LSV (Linear Sweep Voltammogram) diagram of nitrogen / phosphorus co-doped fullerene materials in Example 1 of the present invention (i.e., curve 5-1 in the figure) and Comparative Examples 2-3;

[0032] Figure 6 Graphs showing H2O2 yield and Faraday efficiency of nitrogen / phosphorus co-doped fullerene materials in Application Examples 1 to 5 of the present invention at different potentials in a pure oxygen environment. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing nitrogen / phosphorus co-doped fullerene material comprises the following steps:

[0036] (1) 0.1g of fullerene (C 60 ) was dissolved in 50 mL of carbon disulfide (CS2) and ultrasonicated for 30 minutes to obtain a clear and transparent fullerene solution; then 2 g of melamine was added and mixed uniformly to obtain a mixture A;

[0037] (2) Mixture A is heated until carbon disulfide in mixture A is completely volatilized, 0.4 g of ammonium hypophosphite solution is added to mixture A, and the mixture is dried after ultrasonic treatment to obtain a precursor mixture, which is magnetically stirred until it is completely dissolved to obtain a mixed solution.

[0038] (2) The fullerene solution was slowly poured into the mixed solution and magnetically stirred in a constant temperature water bath at 60 °C for 8 h until CS2 was completely evaporated to form a black viscous precursor mixture.

[0039] (3) The precursor mixture was transferred to a tube furnace and heated to 900°C at a rate of 10°C / min in a high-purity argon (flow rate 50 mL / min) atmosphere. The mixture was kept at this temperature for 0.5 hours for pyrolysis reaction. The mixture was cooled to room temperature naturally and then taken out and ground through a 200-mesh sieve to obtain nitrogen / phosphorus co-doped fullerene material (NPC). 60 ).

[0040] like Figure 1 As shown in the figure, NPC 60 The porous structure exhibits a rich pore structure, with pore sizes primarily ranging from 5 to 15 nm. This porous structure significantly improves the mass transfer efficiency of reactants (such as O2 molecules) on the catalyst surface, acting as a "transport channel" to rapidly deliver reactants to the catalytically active sites. Furthermore, the catalyst's porous structure exposes more active sites, thereby enhancing electrocatalytic performance.

[0041] like Figure 2 As shown in the figure, the nitrogen / phosphorus co-doped fullerene material prepared according to the above steps has an electrochemical performance test (scan rate 10 mV / s, electrolyte pH = 1 perchloric acid solution) with an onset potential of 0.55 V (vs. RHE), a ring current of 0.5 mA, and a H2O2 selectivity of 94%. In terms of kinetics, the catalyst obtained above is more favorable for 2e - ORR produces H2O2.

[0042] Example 2

[0043] A method for preparing nitrogen / phosphorus co-doped fullerene material, which differs from Example 1 only in that the pyrolysis temperature in step (3) is adjusted to 700°C, the heating rate is maintained at 10°C / min, the holding time is extended to 1 hour, and the other parameters are the same, to obtain NPC 60 (700℃).

[0044] like Figure 2 As shown in the figure, the nitrogen / phosphorus co-doped fullerene material prepared according to the above steps has an initial potential of 0.52 V (vs. RHE) under the electrochemical performance test (scan rate 10 mV / s, electrolyte is perchloric acid solution with pH = 1), and the NPC 60 The ring current (700°C) is 0.125 mA, which is about 75% lower than that of Example 1.

[0045] Example 3

[0046] A method for preparing nitrogen / phosphorus co-doped fullerene material, which differs from Example 1 only in that the pyrolysis temperature in step (3) is adjusted to 800°C, the heating rate is maintained at 10°C / min, the holding time is extended to 1 hour, and the other parameters are the same, to obtain NPC 60 (800℃).

[0047] like Figure 2 As shown in the figure, the nitrogen / phosphorus co-doped fullerene material prepared according to the above steps has an initial potential of 0.52 V (vs. RHE) under the electrochemical performance test (scan rate 10 mV / s, electrolyte is perchloric acid solution with pH = 1), and the NPC 60 The ring current at 800°C is 0.26 mA, which is about 48% lower than that in Example 1.

[0048] Example 4

[0049] A method for preparing nitrogen / phosphorus co-doped fullerene material, which differs from Example 1 only in that: in step (3), the pyrolysis temperature is increased to 1000°C, the heating rate is maintained at 10°C / min, and the holding time is extended to 2 hours. The other parameters are the same, and NPC is obtained. 60 (1000℃).

[0050] like Figure 2 As shown in the figure, the nitrogen / phosphorus co-doped fullerene material prepared according to the above steps has an initial potential of 0.50 V (vs. RHE) under the electrochemical performance test (scan rate 10 mV / s, electrolyte is perchloric acid solution with pH = 1), and the NPC 60 The ring current (1000°C) is 0.25 mA, which is about 50% lower than that of Example 1.

[0051] Comparative Example 1

[0052] A method for preparing nitrogen / phosphorus co-doped carbon nanotube material, which is different from Example 1 only in that: fullerene (C 60 ) were replaced with carbon nanotubes (CNTs) of equal mass, and the other parameters and steps were the same to obtain a comparative sample (NPCNT).

[0053] like Figure 3 and Figure 4 As shown, after testing, the nitrogen / phosphorus co-doped carbon nanotube electrocatalyst prepared according to the above steps has an initial potential of 0.588V, a ring current of 0.33mA, and a H2O2 selectivity of 69.5% under the electrochemical performance test (scan rate 10mV / s, electrolyte is perchloric acid solution with pH=1).

[0054] Comparative Example 2

[0055] A method for preparing nitrogen / phosphorus co-doped fullerene material, which differs from Example 1 only in that the mass of ammonium hypophosphite is 0.67 g, and the other parameters and steps are the same, to obtain a comparative sample NPC 60 (3-1).

[0056] like Figure 5 As shown, the nitrogen / phosphorus co-doped fullerene electrocatalyst prepared according to the above steps was tested, and under the electrochemical performance test (scan rate 10mV / s, electrolyte is perchloric acid solution with pH=1), the starting potential was 0.579V and the ring current was 0.4mA, which was about 20% lower than that of Example 1.

[0057] Comparative Example 3

[0058] A method for preparing nitrogen / phosphorus co-doped fullerene material, which differs from Example 1 only in that the mass of ammonium hypophosphite is 0.29 g, and the other parameters and steps are the same, to obtain a comparative sample NPC 60 (7-1).

[0059] like Figure 5 As shown, the nitrogen / phosphorus co-doped fullerene electrocatalyst prepared according to the above steps has an initial potential of 0.623 V and a ring current of 0.35 mA under the electrochemical performance test (scan rate 10 mV / s, electrolyte is perchloric acid solution with pH = 1), which is about 30% lower than that of Example 1.

[0060] Application Example 1

[0061] The electrocatalytic oxygen reduction method of the mobile electrolytic cell comprises the following steps:

[0062] (1) Weigh 10 mg of NPC prepared in Example 1 60The catalyst was prepared into catalyst ink and evenly sprayed on 1×1 cm carbon paper (loading amount about 1 mg / cm²) as the working electrode; Ag / AgCl (saturated with KCl) and RuOx / Ti plates (1×1 cm) were used as the reference electrode and counter electrode, respectively.

[0063] (2) Add 20 ml of 1 mol / L perchloric acid electrolyte to the cathode chamber and the anode chamber respectively, use a peristaltic pump to circulate it at 30% power, and introduce high-purity oxygen into the cathode chamber at a rate of 100 mL / min. Set the voltage to -0.044 V (vs. RHE) and electrolyze for 15 minutes.

[0064] (3) Take 10 μL of the electrolyzed solution and add 4 ml of 0.5 mM cerium sulfate solution. Compare the absorbance of the test solution with the standard curve to obtain the concentration of hydrogen peroxide.

[0065] like Figure 6 As shown, the prepared NPC 60 In the flow electrolysis cell test, the catalyst achieved a Faradaic efficiency of 23.31% at a potential of -0.144 V, and an H2O2 yield of 831.6 mmol·gcat⁻¹·h⁻¹.

[0066] Application Example 2

[0067] A method for producing hydrogen peroxide by oxygen reduction in a mobile electrolytic cell is provided, which differs from Application Example 1 only in that the voltage in step (2) is set to -0.044 V, and the other parameters and steps are the same.

[0068] like Figure 6 As shown in the flow electrolysis cell test, the catalyst has a Faradaic efficiency of nearly 90% and an H2O2 yield of 1122.6 mmol·gcat⁻¹·h⁻¹ at a voltage of -0.044 V.

[0069] Application Example 3

[0070] A method for producing hydrogen peroxide by oxygen reduction in a mobile electrolytic cell is provided, which differs from Application Example 1 only in that the voltage in step (2) is set to 0.056 V, and the other parameters and steps are the same.

[0071] like Figure 6 As shown in the flow electrolysis cell test, the catalyst achieved a Faradaic efficiency of 75.47% at a voltage of 0.056 V and a hydrogen peroxide yield of 833.4 mmol·gcat⁻¹·h⁻¹.

[0072] Application Example 4

[0073] A method for producing hydrogen peroxide by oxygen reduction in a mobile electrolytic cell is provided, which differs from Application Example 1 only in that the voltage in step (2) is set to 0.156 V, and the other parameters and steps are the same.

[0074] like Figure 6 As shown in the flow electrolysis cell test, the catalyst achieved a Faradaic efficiency of 64.55% at a voltage of 0.156 V and a hydrogen peroxide yield of 292.97 mmol·gcat⁻¹·h⁻¹.

[0075] Application Example 5

[0076] A method for producing hydrogen peroxide by oxygen reduction in a mobile electrolytic cell is provided, which differs from Example 1 only in that the voltage in step (2) is set to 0.256 V, and the other parameters and steps are the same.

[0077] like Figure 6 As shown, in the flow electrolysis cell test, the catalyst had a Faradaic efficiency of 38.98% at a voltage of 0.256 V and a hydrogen peroxide yield of 87.23 mmol·gcat⁻¹·h⁻¹.

[0078] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

Claims

1. A nitrogen / phosphorus co-doped fullerene material, characterized by: It is composed of fullerene, melamine and ammonium hypophosphite. Fullerene serves as a carbon skeleton precursor to form rich pentagonal topological defect structures during high-temperature pyrolysis. At the same time, melamine and ammonium hypophosphite serve as nitrogen and phosphorus sources, respectively, decompose at high temperature and evenly dope nitrogen and phosphorus atoms into the carbon skeleton to form highly active catalytic sites.

2. A method for preparing the nitrogen / phosphorus co-doped fullerene material according to claim 1, characterized in that: The following steps are involved: (1) Fullerene is dissolved in carbon disulfide, and then melamine is added and mixed uniformly to obtain a mixture A; (2) heating the mixture A until the carbon disulfide in the mixture A is completely volatilized, adding the ammonium hypophosphite solution to the mixture A, ultrasonically treating the mixture, and then drying to obtain a precursor mixture; (3) The precursor mixture is placed in an inert atmosphere for pyrolysis to obtain the nitrogen / phosphorus co-doped fullerene material.

3. The method for preparing a nitrogen / phosphorus co-doped fullerene material according to claim 2, characterized in that: In step (1), the mass ratio of fullerene to melamine is 1:(30-50).

4. The method for preparing a nitrogen / phosphorus co-doped fullerene material according to claim 2, wherein: In step (2), the mass ratio of ammonium hypophosphite to fullerene is (2-6):

1.

5. The method for preparing a nitrogen / phosphorus co-doped fullerene material according to claim 2, wherein: In step (2), the heating temperature is 60-70°C.

6. The method for preparing a nitrogen / phosphorus co-doped fullerene material according to claim 2, characterized in that: In step (3), the inert atmosphere is argon, the pyrolysis temperature is 750-800°C, the time is 0.5-1h, and the heating rate is 10-15°C / min.

7. The method for preparing a nitrogen / phosphorus co-doped fullerene material according to claim 2, characterized in that: In step (3), the pyrolysis is cooled and then pickled, 0.5-1 mol / L hydrochloric acid is used for pickling, the pickling temperature is 60-80 °C, and the pickling time is 4-6 h; the drying temperature is 60-70 °C, and the drying time is 8-12 h.

8. Use of the nitrogen / phosphorus co-doped fullerene material according to claim 1, characterized in that: The nitrogen / phosphorus co-doped fullerene material is used as a cathode electrocatalyst.

9. The use of a nitrogen / phosphorus co-doped fullerene material according to claim 8, characterized in that: The nitrogen / phosphorus co-doped fullerene material is used as an electrocatalyst in an electrocatalytic oxygen reduction reaction in a mobile electrolytic cell.

10. The use of a nitrogen / phosphorus co-doped fullerene material according to claim 8, characterized in that: The electrocatalyst is used for electrosynthesis of hydrogen peroxide.

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