Chlorine-doped carbon-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a chlorine-doped carbon-based catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving sodium tellurite and polyvinylpyrrolidone in deionized water, sequentially dropwise adding an aqueous solution of ammonia and an aqueous solution of hydrazine hydrate, and reacting at 175-185 DEG C for 2-3 hours to prepare a Te nanowire; the preparation method comprises the following steps: uniformly dispersing Te nanowires, hexamethylenetetramine and phenol in deionized water, and reacting at 155-165 DEG C for 3-4 hours to prepare Te-coated PFR; the method comprises the following steps: in an inert atmosphere, carrying out first heat treatment on Te-coated PFR and melamine in a tube furnace at 900-950 DEG C for 2-3 hours to obtain HC-carbon; and adding HC-carbon and NaCl into deionized water, uniformly stirring and mixing, drying, and carrying out secondary heat treatment in a tubular furnace at 900-950 DEG C for 2-3 hours to obtain the chlorine-doped carbon-based catalyst. The catalyst is suitable for the oxygen reduction reaction of a fuel cell, and the activity and durability are improved.

Description

Technical Field

[0001] The invention relates to a chlorine-doped carbon-based catalyst and a preparation method thereof, as well as application of the catalyst in an oxygen reduction reaction. Background Art

[0002] Under the increasingly serious energy crisis and environmental pollution pressure, the call for making full use of clean new energy is getting louder and louder. As one of the most important technologies for developing clean new energy, electrocatalysis is crucial to global development. The current international frontier research focuses on the design and development of high-performance electrocatalysts.

[0003] Carbon-based materials are widely used in oxygen synthesis electrocatalysts due to their large specific surface area, good conductivity, high stability, and adjustable structural morphology. They include carbon nanotubes, graphene, graphitic carbon nitrogen (g-C3N4), and porous carbon. There are two types of carbon-based electrocatalysts: heteroatom-doped carbon materials and transition metal compounds / carbon composites. Heteroatoms include non-metallic elements such as O, N, S, P, Cl, and metal elements such as Mn, Fe, Co, Ni, Cu, Sn, etc.

[0004] In order to further enhance or regulate the catalytic activity of carbon-supported single-atom site catalysts, various strategies have been developed, including adjusting the electronic structure to enhance the intrinsic catalytic activity, or increasing the atomic utilization by high loading. Mass transfer during the reaction process accelerates the efficiency of electrocatalysts by improving the kinetics of electrocatalytic reactions, such as the regulation of the pores and particle size of the catalyst. The unique local atomic environment of heteroatom-doped catalysts plays a decisive role in determining the activity, selectivity, and stability of electrocatalytic conversions, but the curvature of the carbon substrate is less considered. Compared with flat surfaces, high-curvature surfaces are prone to produce non-planar curved structures and enhance the local electric field, which may be beneficial to improve catalytic activity. Therefore, electrocatalysts with high curvature have greatly attracted the attention of 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 surface curvature modified by chlorine atoms, aiming to design efficient electrocatalysts and promote the development of clean energy. Summary of the invention

[0006] The present invention aims to provide a chlorine-doped carbon-based catalyst and its preparation method and application. The present invention has the advantages of simple process and equipment, low energy consumption, simple post-treatment, etc., and is easy to mass-produce carbon-based electrocatalysts. The obtained chlorine-doped carbon-based catalyst can be applied to oxygen reduction reaction, and the influence of chlorine atom doping and curvature effect on catalytic performance is studied.

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

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

[0009] S1: Sodium tellurite and polyvinyl pyrrolidone are dissolved in deionized water, and aqueous ammonia solution and aqueous hydrazine solution are added dropwise in sequence to disperse evenly, react at 175-185°C (preferably 180°C) for 2-3h (preferably 3h), naturally cool to room temperature, centrifuge, and wash (with acetone) to obtain Te nanowires;

[0010] The mass ratio of sodium tellurite, polyvinyl pyrrolidone, ammonium hydroxide contained in the aqueous ammonia solution, and hydrazine hydrate contained in the aqueous hydrazine hydrate 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 volume ratio of sodium tellurite to deionized water is 1:350.33-397.89, g / mL; preferably 1:379.74, g / mL;

[0012] Ammonia solution concentration 20-30wt%, preferably 25wt%;

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

[0014] S2: Te nanowires, hexamethylenetetramine and phenol obtained in S1 are uniformly dispersed in deionized water, reacted at 155-165°C (preferably 160°C) for 3-4h (preferably 4h), cooled to room temperature, filtered, washed (with deionized water), and dried to obtain phenolic resin-coated Te nanowires, recorded 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 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 0.1 M of the aqueous solution of phenol;

[0018] S3: Under an inert atmosphere, the Te@PFR obtained in S2 and melamine are first heat-treated in a tube furnace at 900-950°C (preferably 900°C) for 2-3h (preferably 2h), and the obtained product is recorded 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: adding the HC-carbon and NaCl obtained in S3 into deionized water, stirring and mixing, and then stirring at 80-90° C. (preferably 86° C.) until dry, and heat-treating the dried mixture for a second time in a tube furnace at 900-950° C. (preferably 900° C.) for 2-3 h (preferably 2 h) under an inert atmosphere, and then cooling 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] The invention relates to a chlorine-doped carbon-based catalyst prepared by the preparation method.

[0025] The chlorine-doped carbon-based catalyst of the present invention can be used in oxygen reduction reaction.

[0026] The technical principles of the present invention include:

[0027] The present invention first prepares Te@PFR, then uses melamine as a nitrogen doping agent, obtains HC-carbon through a first heat treatment, then dopes Cl with NaCl, and obtains the final catalyst through a second heat treatment. The preparation process of the present invention can promote the formation of sp3 hybridized carbon, and this structural change helps to change the electronic structure of nitrogen-adjacent carbon. At the same time, NaCl molten salt etching provides abundant paths for the transmission of electrons / protons, which helps to improve the efficiency of the electrocatalyst.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The raw materials used are easily available, the preparation method is simple and has good repeatability. Compared with traditional electrocatalysts, the activity and durability of the catalyst can be improved due to the curvature effect. The chlorine-doped carbon-based catalyst of the present invention can be applied to the oxygen reduction reaction (ORR) of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : XRD diagram of Example 1 of the present invention.

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

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

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

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

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

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

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

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

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

[0040] Fig.11 : LSV performance curve of ORR of Example 8 of the present invention in 0.1M KOH solution. DETAILED DESCRIPTION

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

[0042] Example 1

[0043] 0.09g of sodium tellurite and 1g of polyvinyl pyrrolidone were dispersed in 35.2ml of deionized water and stirred on a magnetic stirrer until a clear and transparent solution was obtained. Subsequently, 3.35ml of 25wt% ammonia solution and 1.45ml of 85wt% hydrated hydrazine solution were slowly added to the solution in sequence and stirred slowly for 5min. Subsequently, the solution was transferred to a 50ml reactor and reacted in an oven at 180°C for 3h. During the reaction, the solution reacted and a linear substance (Te nanowire mixture) was generated. After the reaction was completed and naturally cooled to room temperature, 7.6ml of the obtained Te nanowire mixture was taken and repeatedly centrifuged using acetone to obtain a precipitate, and 0.35g of hexamethylenetetramine, 10ml of phenol aqueous solution (0.1 mol / L) and 25ml of deionized water were added for hydrothermal reaction. The reaction was carried out at 160 °C for 4 h. After cooling, the organic matter was washed with deionized water and filtered and dried. A certain amount of the dried Te@PFR and melamine (1:5) were placed in a quartz boat and calcined for the first time at 900 °C for 2 h in nitrogen (the reaction heating rate was 5 °C min -1 ). After cooling, HC-carbon was obtained.

[0044] 100 mg of HC-carbon and 600 mg of NaCl were weighed and added to 50 ml of deionized water and stirred overnight to obtain a mixed solution. The mixture was dried under stirring at 86 °C and placed in a quartz boat and calcined at 900 °C for 2 h in nitrogen (the reaction heating rate was 5 °C min -1 ). The product was obtained after cooling at room temperature.

[0045] The crystal phase analysis is as follows:

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

[0047] The surface analysis is as follows:

[0048] The surface morphology of the material was observed using a scanning electron microscope (SEM). Figure 2 It can be observed that Example 1 has a curved nano-necklace structure.

[0049] Raman analysis is as follows: Using Raman spectroscopy, the D band and G band of Example 1 were analyzed, and the results are as follows: Figure 3 After heat treatment, ID / IG is about 1.04.

[0050] Electrochemical performance test:

[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 a catalyst ink.

[0052] Electrochemical tests were performed using a conventional 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) by the following calculation: E(vs. RHE) = E(vs. Ag-AgCl) + 0.222 + 0.059 pH All polarization curves were corrected with 95% IR compensation.

[0054] The linear sweep voltammetry curve LSV was performed with 0.1M KOH solution as the electrolyte. Figure 4 As shown, it can be seen that the half-wave potential of Example 1 is 0.91 V, which has a higher alkaline oxygen reduction performance.

[0055] Example 2

[0056] The other operations were the same as in Example 1, except that the mass of sodium chloride added was 200 mg. Figure 5 , its half-wave potential is 0.852V.

[0057] Example 3

[0058] The other operations were the same as in Example 1, except that the mass of sodium chloride added was 400 mg. Figure 6 , its half-wave potential is 0.885V.

[0059] Example 4

[0060] The other operations were the same as in Example 1, except that the mass of sodium chloride added was 800 mg. Figure 7 , its half-wave potential is 0.861V.

[0061] Example 5

[0062] The other operations were the same as in Example 1, except that the mass ratio of Te@PFR to melamine during the first calcination was 1:1. Figure 8 , its half-wave potential is 0.866V.

[0063] Example 6

[0064] The other operations were the same as in Example 1, except that melamine was added during the second calcination, and the amount of melamine used was 100 mg. Fig. 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°C. Fig.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°C. Fig.11 , its half-wave potential is 0.826V.

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

[0070] The present invention applies specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a chlorine-doped carbon-based catalyst, characterized in that: The steps include: S1: Sodium tellurite and polyvinyl pyrrolidone are dissolved in deionized water, and aqueous ammonia solution and aqueous hydrazine solution are added dropwise in sequence to disperse evenly, react at 175-185°C for 2-3h, cool naturally to room temperature, centrifuge, and wash to obtain Te nanowires; S2: Te nanowires, hexamethylenetetramine and phenol obtained in S1 are uniformly dispersed in deionized water, reacted at 155-165°C for 3-4 hours, cooled to room temperature, filtered, washed and dried to obtain phenolic resin-coated Te nanowires, recorded as Te@PFR; S3: Under an inert atmosphere, the Te@PFR obtained in S2 and melamine were first heat-treated in a tube furnace at 900-950°C for 2-3h, and the obtained product was recorded as HC-carbon; S4: Add the HC-carbon and NaCl obtained in S3 to deionized water, stir and mix, and then stir at 80-90°C until dry. Under an inert atmosphere, heat treat the dried mixture for a second time in a tube furnace at 900-950°C for 2-3h, and then cool to room temperature to obtain the chlorine-doped carbon-based catalyst.

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

31.

3. The method for preparing a chlorine-doped carbon-based catalyst according to 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 method for preparing a chlorine-doped carbon-based catalyst according to claim 1, characterized in that: In S3, the mass ratio of Te@PFR to melamine is 1:1-5.

5. The method for preparing a chlorine-doped carbon-based catalyst according to claim 1, characterized in that: In S4, the mass ratio of HC-carbon to NaCl is 1:2-8.

6. A chlorine-doped carbon-based catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the chlorine-doped carbon-based catalyst as claimed in claim 6 in oxygen reduction reaction.

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