Chlorine-doped carbon-based catalyst, and preparation method and application thereof

Abstract

The application discloses a chlorine-doped carbon-based catalyst and a preparation method and application thereof; sodium tellurite and polyvinylpyrrolidone are dissolved in deionized water, an ammonia solution and an aqueous solution of hydrated hydrazine are added dropwise in sequence, and Te nanowires are prepared by reacting at 175-185 DEG C for 2-3 h; the Te nanowires, hexamethylenetetramine and phenol are uniformly dispersed in deionized water, and Te@PFR is prepared by reacting at 155-165 DEG C for 3-4 h; under an inert atmosphere, the Te@PFR is subjected to first heat treatment at 900-950 DEG C in a tube furnace for 2-3 h to obtain HC-carbon; the HC-carbon and NaCl are added into deionized water, stirred and uniformly mixed, dried, subjected to second heat treatment at 900-950 DEG C in a tube furnace for 2-3 h, and the chlorine-doped carbon-based catalyst is obtained; the catalyst is suitable for oxygen reduction reaction of a fuel cell, and the activity and durability are improved.

Description

Technical Field

[0001] This invention relates to a chlorine-doped carbon-based catalyst, its preparation method, and its application in oxygen reduction reactions. Background Technology

[0002] Amidst the escalating energy crisis and environmental pollution, there is a growing call to fully utilize clean and renewable energy sources. Electrocatalysis, as one of the most crucial technologies for developing clean and renewable energy, is vital for global development. Current international cutting-edge research focuses on the design and development of high-performance electrocatalysts.

[0003] Carbon-based materials are widely used in the synthesis of oxygen electrocatalysts due to their advantages such as large specific surface area, good electrical conductivity, high stability, and tunable structural morphology. These materials include carbon nanotubes, graphene, graphitic carbon-nitrogen (g-C3N4), and porous carbon. Carbon-based electrocatalysts fall into two categories: heteroatom-doped carbon materials and transition metal compound / carbon composite materials. Heteroatoms include non-metallic elements such as O, N, S, P, and Cl, as well as metallic elements such as Mn, Fe, Co, Ni, Cu, and Sn.

[0004] To further enhance or modulate the catalytic activity of carbon-supported single-atom-site catalysts, various strategies have been developed, including adjusting the electronic structure to improve intrinsic catalytic activity or increasing atom utilization through high loading. Mass transfer during the reaction process accelerates the efficiency of electrocatalysts by improving the kinetics of electrocatalytic reactions, such as by tuning the catalyst's pore size and particle size. The unique local atomic environment of heteroatom-doped catalysts plays a decisive role in determining the activity, selectivity, and stability of electrocatalytic conversions; however, the curvature of the carbon substrate is rarely considered. Compared to flat surfaces, high-curvature surfaces tend to generate non-planar curved structures, enhancing the local electric field, which may be beneficial for improving catalytic activity. Therefore, electrocatalysts with high curvature have attracted great attention from researchers in improving electrocatalytic activity.

[0005] Our research focuses on the role of surface curvature in electrocatalysis and explores the electrocatalytic performance of carbon-based catalysts with chlorine-modified surface curvature, aiming to design highly efficient electrocatalysts to promote the development of clean energy. Summary of the Invention

[0006] The present invention aims to provide a chlorine-doped carbon-based catalyst, its preparation method, and its application. This invention has advantages such as simple process and equipment, low energy consumption, and convenient post-processing, facilitating the large-scale production of carbon-based electrocatalysts. The obtained chlorine-doped carbon-based catalyst can be applied to oxygen reduction reactions, and the effects of chlorine atom doping and curvature effect on catalytic performance were investigated.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a chlorine-doped carbon-based catalyst includes the following steps:

[0009] S1: Dissolve sodium tellurite and polyvinylpyrrolidone in deionized water, then add ammonia solution and hydrazine solution dropwise in sequence, disperse evenly, react at 175-185℃ (preferably 180℃) for 2-3 hours (preferably 3 hours), cool naturally to room temperature, centrifuge, and wash (with acetone) to obtain Te nanowires.

[0010] The mass ratio of sodium tellurite, polyvinylpyrrolidone, ammonium hydroxide contained in the ammonia solution, and hydrazine hydrate contained in the aqueous solution is 0.09:0.99-1.04:0.745-0.767:1.23-1.31, preferably 0.09:1:0.756:1.272;

[0011] The mass-to-volume ratio of sodium tellurite to deionized water is 1:350.33–397.89, g / mL; preferably 1:379.74, g / mL.

[0012] The concentration of ammonia solution is 20-30 wt%, preferably 25 wt%.

[0013] The aqueous solution concentration of hydrazine hydrate is 80-85 wt%, preferably 85 wt%;

[0014] S2: The Te nanowires obtained in S1, hexamethylenetetramine, and phenol are uniformly dispersed in deionized water and reacted at 155-165℃ (preferably 160℃) for 3-4 hours (preferably 4 hours). After cooling to room temperature, the mixture is filtered, washed (with deionized water), and dried to obtain phenolic resin-coated Te nanowires, denoted as Te@PFR.

[0015] The molar ratio of hexamethylenetetramine, phenol and sodium tellurite in S1 is 0.000998-0.00285:0.0004-0.0015:0.000077, preferably 0.0025:0.001:0.000077;

[0016] The volume-to-mass ratio of deionized water to sodium tellurite in S1 is 1098.55–2022.54:1, mL / g; preferably 2016.22:1, mL / g.

[0017] Phenol is added in the form of an aqueous solution of phenol, preferably with a concentration of 0.1M.

[0018] S3: Under an inert atmosphere, the Te@PFR obtained in S2 is subjected to a first heat treatment with melamine in a tube furnace at 900-950°C (preferably 900°C) for 2-3 hours (preferably 2 hours). The resulting product is denoted as HC-carbon.

[0019] The inert atmosphere is nitrogen or argon;

[0020] The mass ratio of Te@PFR to melamine is 1:1 to 5, preferably 1:5;

[0021] S4: Add the HC-carbon and NaCl obtained in S3 to deionized water, stir and mix well, then stir at 80-90℃ (preferably 86℃) until dry. Under an inert atmosphere, heat the dried mixture for a second time in a tube furnace at 900-950℃ (preferably 900℃) for 2-3 hours (preferably 2 hours), and then cool to room temperature to obtain the chlorine-doped carbon-based catalyst.

[0022] The inert atmosphere is nitrogen or argon;

[0023] The mass ratio of HC-carbon to NaCl is 1:2 to 8, preferably 1:6.

[0024] This invention relates to chlorine-doped carbon-based catalysts prepared by the above-described method.

[0025] The chlorine-doped carbon-based catalyst described in this invention can be used in oxygen reduction reactions.

[0026] The technical principles of this invention include:

[0027] This invention first prepares Te@PFR, then uses melamine as a nitrogen dopant, and obtains HC-carbon through a first heat treatment. Next, Cl is doped with NaCl, followed by a second heat treatment to obtain the final catalyst. The preparation process of this invention can promote the formation of sp3 hybrid carbon. This structural change helps to alter the electronic structure of nitrogen-adjacent carbons, while NaCl molten salt etching provides abundant pathways for electron / proton transport, which helps to improve the efficiency of the electrocatalyst.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The raw materials used are readily available, the preparation method is simple, and the reproducibility is good. Compared with traditional electrocatalysts, the curvature effect can improve catalyst activity and durability. The chlorine-doped carbon-based catalyst of this invention is suitable for the oxygen reduction reaction (ORR) in fuel cells. Attached Figure Description

[0030] Figure 1 XRD pattern of Embodiment 1 of the present invention.

[0031] Figure 2 SEM image of Embodiment 1 of the present invention.

[0032] Figure 3 Raman diagram of Embodiment 1 of the present invention.

[0033] Figure 4 : LSV diagram of Embodiment 1 of the present invention.

[0034] Figure 5 Example 2 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0035] Figure 6 Example 3 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0036] Figure 7 Example 4 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0037] Figure 8 Example 5 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0038] Figure 9 Example 6 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0039] Figure 10 Example 7 of the present invention: LSV performance curve of ORR in 0.1M KOH solution.

[0040] Figure 11 Example 8 of the present invention: LSV performance curve of ORR in 0.1M KOH solution. Detailed Implementation

[0041] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0042] Example 1

[0043] 0.09 g of sodium tellurite and 1 g of polyvinylpyrrolidone were dispersed in 35.2 mL of deionized water and stirred on a magnetic stirrer until a clear and transparent solution was obtained. Then, 3.35 mL of 25 wt% ammonia solution and 1.45 mL of 85 wt% hydrated hydrazine solution were slowly added dropwise to the solution, and the mixture was stirred slowly for 5 min. The solution was then transferred to a 50 mL reaction vessel and reacted in an oven at 180 °C for 3 h. During the reaction, the solution reacted to form a filamentous substance (Te nanowire mixture). After the reaction was completed and the solution was allowed to cool naturally to room temperature, 7.6 mL of the prepared Te nanowire mixture was taken and repeatedly centrifuged with acetone to obtain a precipitate. Then, 0.35 g of hexamethylenetetramine, 10 mL of phenol aqueous solution (0.1 mol / L), and 25 mL of deionized water were added to initiate a hydrothermal reaction. The reaction was carried out at 160℃ for 4 hours. After cooling, the product was washed with deionized water and the organic matter was filtered out. After drying, a certain amount of the dried Te@PFR was placed in a quartz boat with melamine (1:5) and calcined at 900℃ for 2 hours under nitrogen atmosphere (the reaction heating rate was 5℃ / min). -1 After cooling, HC-carbon is obtained.

[0044] Weigh 100 mg of HC-carbon and 600 mg of NaCl and add them to 50 ml of deionized water. Stir overnight to obtain a mixed solution. Dry the solution at 86 °C with stirring to obtain a mixture. Place the mixture in a quartz boat and calcine it again at 900 °C for 2 hours under nitrogen atmosphere (the reaction heating rate is 5 °C / min). -1 The product was obtained after cooling at room temperature.

[0045] The crystalline phase analysis is as follows:

[0046] The crystalline phase of Example 1 was analyzed using powder X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown, only characteristic peaks of carbon were found, with no other diffraction peaks, indicating that no other metal particles were present in Example 1.

[0047] Surface analysis is as follows:

[0048] The surface morphology of the material was observed using a scanning electron microscope (SEM), and the results are as follows: Figure 2 As shown, Example 1 exhibits a curved nanonecklace structure.

[0049] Raman analysis is as follows: Raman spectroscopy was used to analyze the D and G bands of Example 1, and the results are as follows. Figure 3 As shown. After heat treatment, ID / IG is approximately 1.04.

[0050] Electrochemical performance testing:

[0051] Preparation of catalyst ink: 5 mg of catalyst sample was dispersed in 700 μL of deionized water, 250 μL of ethanol, and 50 μL of Nafion (5 wt%) to form catalyst ink.

[0052] Electrochemical tests were performed using a traditional three-electrode electrochemical workstation (CHI 760E), with a Pt wire as the counter electrode, a glassy carbon electrode as the working electrode, and an Ag-AgCl (saturated potassium chloride solution) electrode as the reference electrode.

[0053] All potentials were calibrated relative to the reversible hydrogen electrode (RHE) using the following calculation: E(vs.RHE) = E(vs.Ag-AgCl) + 0.222 + 0.059pH. All polarization profiles were corrected for 95% IR compensation.

[0054] Linear sweep voltammetry (LSV) was performed with 0.1 M KOH solution as the electrolyte. The results are as follows: Figure 4 As shown, Example 1 has a half-wave potential of 0.91V and exhibits high alkaline oxygen reduction performance.

[0055] Example 2

[0056] The other procedures are the same as in Example 1, except that the mass of sodium chloride added is 200 mg. The LSV performance graph for ORR is shown below. Figure 5 Its half-wave potential is 0.852V.

[0057] Example 3

[0058] The other procedures are the same as in Example 1, except that the mass of sodium chloride added is 400 mg. The LSV performance graph of ORR is shown below. Figure 6 Its half-wave potential is 0.885V.

[0059] Example 4

[0060] The other procedures are the same as in Example 1, except that the mass of sodium chloride added is 800 mg. The LSV performance graph of ORR is shown below. Figure 7 Its half-wave potential is 0.861V.

[0061] Example 5

[0062] The other operations are the same as in Example 1, except that the mass ratio of Te@PFR to melamine is 1:1 during the first calcination. The LSV performance graph of ORR is shown below. Figure 8 Its half-wave potential is 0.866V.

[0063] Example 6

[0064] The other operations are the same as in Example 1, except that melamine is added during the second calcination, and the amount of melamine used is 100 mg. The LSV performance graph of ORR is shown below. Figure 9 Its half-wave potential is 0.855V.

[0065] Example 7

[0066] The other operations are the same as in Example 1, except that the heat treatment temperature during the first calcination is 700℃. The LSV performance graph of ORR is shown below. Figure 10 Its half-wave potential is 0.794V.

[0067] Example 8

[0068] The other operations are the same as in Example 1, except that the heat treatment temperature during the first calcination is 1150℃. The LSV performance graph of ORR is shown below. Figure 11 Its half-wave potential is 0.826V.

[0069] All of the above technical solutions can be combined in any way to form optional embodiments of the present invention, and will not be described in detail here.

[0070] This invention uses specific examples to illustrate the principles and implementation methods of the invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A method for preparing a chlorine-doped carbon-based catalyst, characterized in that, Includes the following steps: S1: Sodium tellurite and polyvinylpyrrolidone were dissolved in deionized water, and ammonia solution and hydrazine hydrate solution were added dropwise in sequence. The mixture was dispersed evenly and reacted at 175~185℃ for 2~3h. After naturally cooling to room temperature, the mixture was centrifuged and washed to obtain Te nanowires. S2: The Te nanowires obtained in S1, hexamethylenetetramine, and phenol are uniformly dispersed in deionized water and reacted at 155~165℃ for 3~4h. After cooling to room temperature, the mixture is filtered, washed, and dried to obtain phenolic resin-coated Te nanowires, denoted as Te@PFR. S3: Under an inert atmosphere, the Te@PFR obtained in S2 was subjected to a first heat treatment with melamine in a tube furnace at 900~950℃ for 2~3h. The resulting product was denoted as HC-carbon. The mass ratio of Te@PFR to melamine is 1:5; S4: Add the HC-carbon and NaCl obtained in S3 to deionized water, stir and mix well, then stir at 80~90℃ until dry. Under an inert atmosphere, heat the dried mixture in a tube furnace at 900~950℃ for a second time for 2~3 hours, and then cool to room temperature to obtain the chlorine-doped carbon-based catalyst. The mass ratio of HC-carbon to NaCl is 1:

6.

2. The method for preparing the chlorine-doped carbon-based catalyst as described in claim 1, characterized in that, In S1, the mass ratio of sodium tellurite, polyvinylpyrrolidone, ammonium hydroxide contained in the ammonia solution, and hydrazine hydrate contained in the aqueous solution is 0.09:0.99~1.04:0.745~0.767:1.23~1.

31.

3. The method for preparing the chlorine-doped carbon-based catalyst as described in claim 1, characterized in that, In S2, the molar ratio of hexamethylenetetramine, phenol and sodium tellurite in S1 is 0.000998~0.00285:0.0004~0.0015:0.000077.

4. The chlorine-doped carbon-based catalyst prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the chlorine-doped carbon-based catalyst as described in claim 4 in the oxygen reduction reaction.

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