Nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide as well as preparation method and application of nitrogen-doped carbon catalyst

Abstract

The invention relates to a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide as well as a preparation method and application of the nitrogen-doped carbon catalyst, and belongs to the field of electro-catalysis new energy materials and technologies. According to the catalyst, polyaniline serves as a carbon source and a nitrogen source, silicon dioxide balls serve as a sacrificial template, and the hollow nitrogen-doped carbon material is prepared through a one-step pyrolysis method in combination with a wet chemical etching method. The nitrogen-doped carbon material prepared by the method has relatively high electrocatalytic activity and hydrogen peroxide selectivity in a two-electron oxygen reduction process, and has a potential application prospect in the field of electrochemical preparation of hydrogen peroxide.

Description

Technical Field

[0001] The invention belongs to the technical field of electrode materials for electrochemical catalytic synthesis of hydrogen peroxide, and in particular relates to a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide, and a preparation method and application thereof. Background Art

[0002] As a recognized environmentally friendly oxidant, hydrogen peroxide is widely used in chemical synthesis, medical disinfection, sewage treatment, semiconductor cleaning, pulp bleaching and other fields because it does not produce byproducts other than water during the reaction process. In addition, H2O2 has the advantages of convenient storage, safe operation and high oxidation potential, and can also be used as an ideal oxidant and reliable hydrogen energy carrier in fuel cells. The obvious defects of the traditional anthraquinone process and the direct synthesis of hydrogen peroxide from hydrogen and oxygen mixed gas have forced the industry and academia to develop alternative methods for hydrogen peroxide synthesis that are low-cost, environmentally friendly, highly resource-efficient and sustainable.

[0003] Based on the electrochemical oxygen reduction reaction, oxygen is selectively reduced to hydrogen peroxide through a two-electron transfer pathway at room temperature and pressure. This method has the advantages of safety, environmental protection, and mild reaction. It can effectively solve the problems existing in the anthraquinone process for synthesizing hydrogen peroxide and is considered to be a very promising strategy for hydrogen peroxide synthesis. However, due to the slow oxygen reduction reaction kinetics and the competing four-electron reaction process, the development of high-performance catalysts with high oxygen reduction reaction activity and two-electron selectivity is the core of current research. In recent years, carbon-based materials have been widely used in the field of two-electron oxygen reduction synthesis of hydrogen peroxide due to their advantages such as abundant reserves, low cost, and easy structure regulation, and have made significant research progress. Summary of the invention

[0004] The purpose of the present invention is to provide an application of a nitrogen-doped carbon material in electrochemical catalytic synthesis of hydrogen peroxide. The nitrogen-doped carbon material is used as a cathode catalyst for oxygen reduction reaction to synthesize hydrogen peroxide with high selectivity.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] The invention provides a preparation method of a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide and application thereof.

[0007] In the above technical solution, further, the preparation method of the nitrogen-doped carbon catalyst comprises the following steps:

[0008] Step S1: Take 10 mL of ammonia solution and add it to a mixed solution of deionized water (40 mL) and ethanol (250 mL), stir vigorously for 10 min to make the mixed solution fully uniform, then add 10 mL of tetraethyl silicate thereto, and continue stirring for 10 min.

[0009] Step S2: The suspension in step S1 was placed in an ice bath and protected from light. 500 μL of aniline was added dropwise under magnetic stirring. After stirring for 15 min, 3 mL of 1.5 mol·L-1 ammonium persulfate was added dropwise. The mixture was then stirred for 6 h under ice bath conditions.

[0010] Step S3: The mixture obtained after the reaction in step 2 is filtered and washed with anhydrous ethanol and deionized water respectively. The obtained sample is dried in a vacuum drying oven at 80° C. for 5 h and ground into powder.

[0011] Step S4: The powder in step S3 is placed in a horizontal tube furnace, pyrolyzed at 800° C. under an inert gas atmosphere and kept warm for 2 h to obtain a carbonized sample.

[0012] Step S5: The sample obtained in step S4 was placed in 20 mL of hydrofluoric acid solution (5%) and vigorously stirred for 24 h, followed by filtration, washing and drying to obtain the final nitrogen-doped carbon catalyst sample.

[0013] In the above invention, further, the carbon material is hollow porous carbon.

[0014] In the above invention, further, in step 1, the ratio of tetraethyl silicate to solvent is 1:30.

[0015] In the above invention, further, in step 2, the volume ratio of aniline to ammonium persulfate is 1:6.

[0016] In the above invention, further, the inert gas in step 4 is 99.999% high-purity N2.

[0017] In the above invention, further, in step 4, the heating rate of the tubular furnace is 5-10°C·min-1.

[0018] In the above invention, further, according to the method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, it is characterized in that: the nitrogen-doped carbon catalyst is used for preparing hydrogen peroxide by electrochemical oxygen reduction reaction.

[0019] The present invention uses silicon dioxide obtained by hydrolyzing tetraethyl silicate as a template, utilizes in-situ aniline combined with high-temperature pyrolysis, and finally etches the template through a wet chemical method to obtain a hollow nitrogen-doped carbon material having a high nitrogen functional group (such as pyridinic nitrogen, pyrrolic nitrogen, etc.) content, which can increase the specific surface area of ​​the catalyst and increase the catalytic active sites, regulate hydrophilicity / hydrophobicity, and adjust the adsorption behavior of OOH intermediates, thereby improving the selectivity of H2O2.

[0020] The present invention also provides a method for preparing hydrogen peroxide by electrochemical means, wherein the nitrogen-carbon catalyst is coated on a conductive electrode, and then an oxygen reduction reaction is performed to prepare hydrogen peroxide. The medium of the electrochemical reaction may be acidic or alkaline.

[0021] The reagents and raw materials used in the present invention are commercially available. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM electron microscope photograph of the catalyst prepared in the present invention.

[0023] Figure 2 This is a SEM electron microscope photograph of the catalyst prepared in the present invention.

[0024] Figure 3 The activity of the catalyst prepared in the present invention in synthesizing hydrogen peroxide by oxygen reduction was tested.

[0025] Figure 4 This is a hydrogen peroxide selectivity curve of the catalyst prepared in the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below by way of examples, but the present invention is not limited thereby.

[0027] Step S1: 10 mL of ammonia solution was added to a mixed solution of 40 mL of deionized water and 250 mL of ethanol, and the mixed solution was stirred vigorously for 10 min to make it fully uniform. Then, 10 mL of tetraethyl silicate was added thereto, and stirring was continued for 10 min.

[0028] Step S2: The suspension in step S1 was placed in an ice bath and protected from light. 500 μL of aniline was added dropwise under magnetic stirring. After stirring for 15 min, 3 mL of 1.5 mol·L-1 ammonium persulfate was added dropwise. The mixture was then stirred for 6 h under ice bath conditions.

[0029] Step S3: The mixture obtained after the reaction in step 2 is filtered and washed with anhydrous ethanol and deionized water respectively. The obtained sample is dried in a vacuum drying oven at 80° C. for 5 h and ground into powder.

[0030] Step S4: The powder in step S3 is placed in a horizontal tube furnace, pyrolyzed at 800° C. under an inert gas atmosphere and kept warm for 2 h to obtain a carbonized sample.

[0031] Step S5: The sample obtained in step S4 was placed in 20 mL of hydrofluoric acid solution (5%) and vigorously stirred for 24 h, followed by filtration, washing and drying to obtain the final nitrogen-doped carbon catalyst sample.

[0032] The catalyst prepared in step S5 is dispersed in a mixed solution of water, isopropanol and nafion. After uniform ultrasonic dispersion, a certain amount of the dispersed liquid is dropped onto a rotating ring disk electrode and dried naturally in the air. Then, a 0.1M KOH solution is added to an H-type electrolytic cell for electrochemical testing. During the reaction, the electrode speed is 1600rpm and the Pt ring current is 1.23V. The current for oxidizing hydrogen peroxide can be calculated from the ring current (Iring, in mA). The current size of the ring electrode is mainly determined by the collection efficiency (N).

[0033] The hydrogen peroxide selectivity (%) of the catalyst in the oxygen reduction reaction process was calculated by the following formula:

[0034]

[0035] Where Idesk is the current detected by the disk electrode, Iring is the current detected by the Pt ring, and Iring,bg represents the background ring current.

Claims

1. Preparation of a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide, characterized in that The steps include: Step S1: Take 10 mL of ammonia solution and add it to a mixed solution of deionized water (40 mL) and ethanol (250 mL), stir vigorously for 10 min to make the mixed solution fully uniform, then add 10 mL of tetraethyl silicate thereto, and continue stirring for 10 min. Step S2: The suspension in step S1 was placed in an ice bath and protected from light. 500 μL of aniline was added dropwise under magnetic stirring. After stirring for 15 min, 3 mL of 1.5 mol·L-1 ammonium persulfate was added dropwise. The mixture was then stirred for 6 h under ice bath conditions. Step S3: The mixture obtained after the reaction in step 2 is filtered and washed with anhydrous ethanol and deionized water respectively. The obtained sample is dried in a vacuum drying oven at 80° C. for 5 h and ground into powder. Step S4: The powder in step S3 is placed in a horizontal tube furnace, pyrolyzed at 800° C. under an inert gas atmosphere and kept warm for 2 h to obtain a carbonized sample. Step S5: The sample obtained in step S4 was placed in 20 mL of hydrofluoric acid solution (5%) and vigorously stirred for 24 h, followed by filtration, washing and drying to obtain the final nitrogen-doped carbon catalyst sample.

2. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The carbon material is hollow porous carbon.

3. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The ratio of tetraethyl silicate to solvent in step 1 is 1:

30.

4. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The volume ratio of aniline to ammonium persulfate in step 2 is 1:

6.

5. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The inert gas in step 4 is 99.999% high purity N2.

6. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The heating rate of the tubular furnace in step 4 is 5-10°C·min-1.

7. The method for preparing a nitrogen-doped carbon catalyst for electrochemical synthesis of hydrogen peroxide according to claim 1, characterized in that: The nitrogen-doped carbon catalyst is applied to prepare hydrogen peroxide by electrochemical oxygen reduction reaction.

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