Catalyst for electrosynthesis of hydrogen peroxide and preparation method thereof

Abstract

The invention relates to the field of electro-catalysis, and particularly discloses a catalyst for electro-synthesis of hydrogen peroxide and a preparation method of the catalyst. Petroleum asphalt is selected as a carbon source, an oxygen-containing carbon material is prepared by adopting a low-temperature one-step method, the temperature in a reaction kettle is 200-240 DEG C, the prepared catalyst has a pore structure, and oxygen-containing groups are formed on the outer surface of the catalyst. The preparation method is simple, the steps are easy to operate, the problem that energy consumption is too high when an oxygen-containing carbon material is prepared through a high-temperature calcination method is avoided, acid with strong oxidizing property does not need to be used, and the prepared catalyst is used for generating hydrogen peroxide through an electrocatalytic oxidation reduction method and is high in selectivity and good in catalytic effect.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and in particular to a catalyst for electrosynthesis of hydrogen peroxide and a preparation method thereof. Background Art

[0002] Currently, electrocatalytic O2 reduction to H2O2 is still at the laboratory research stage. The lack of low-cost, mass-produced catalysts with high catalytic activity and selectivity for the two-electron O2 reduction reaction is a major limitation to the industrialization of electrocatalytic H2O2 synthesis. The catalysts currently under investigation in the laboratory primarily include precious metal catalysts, metal oxide catalysts, metal complex catalysts, single-atom catalysts, and carbon-based catalysts. Carbon-based catalysts offer advantages such as abundant raw materials, acid and alkali resistance, non-toxicity, and easily tunable structures, making them ideal catalysts for electrocatalytic O2 reduction to H2O2. Carbon materials such as ordered mesoporous carbon, carbon nanohorns, graphene, and carbon nanotubes exhibit excellent H2O2 electroproduction performance after appropriate functionalization. However, the mass-production technology for these carbon materials remains immature or expensive, and the functionalization methods are complex. Consequently, the development of inexpensive, scalable, and easily tunable carbon-based catalysts remains a challenge.

[0003] Oxidized carbon materials are a type of carbon-based catalyst for the efficient electrosynthesis of H2O2, usually prepared through a two-step process of carbon material preparation and oxidation treatment. Carbon materials are usually prepared by high-temperature calcination of a carbon source in an airtight environment, and the oxidation treatment usually uses concentrated acid oxidation to introduce oxygen-containing groups. Direct calcination of a carbon source generally yields carbon materials with larger sizes and blocky morphology, which have a small specific surface area and low catalytic activity as catalysts. Therefore, it is necessary to control the carbonization conditions to obtain carbon materials with high specific surface area. In addition, the high-temperature calcination process generally requires temperatures above 800°C, resulting in high energy consumption and high carbon material preparation costs. The use of concentrated acid oxidation to introduce oxygen-containing groups into carbon materials has problems such as high acid consumption, slow reaction process, cumbersome solid-liquid separation, and difficult waste acid treatment, making the acid oxidation process of carbon materials difficult to industrialize. Summary of the Invention

[0004] The present invention provides a catalyst for electrosynthesis of hydrogen peroxide and a preparation method thereof, which can prepare carbon materials at a relatively low temperature and simultaneously introduce oxygen-containing groups, thereby solving the problems of high energy consumption in preparing carbon materials by calcining carbon sources at high temperatures, long oxidation treatment time using a strong oxidizing acid, complicated solid-liquid separation steps, and pollution caused by waste acid treatment.

[0005] The present invention adopts the following technical solutions: A method for preparing a catalyst for electrosynthesis of hydrogen peroxide comprises the following steps: (1) Take petroleum asphalt as raw material and use it as a carbon source after pretreatment; (2) Add deionized water to the carbon source obtained by pretreatment in step (1), stir thoroughly, and transfer to a high-pressure reactor. The amount of deionized water added is 10-30 times the mass of the carbon source. (3) The mixture in the reactor is reacted at 200-240°C for 1.5-5 hours, and then the reactor is cooled to room temperature; (4) The reactants obtained in the reactor are filtered through microporous vacuum, rinsed with distilled water until the filtrate is transparent, and the filter cake is dried to obtain a carbon-based catalyst.

[0006] Furthermore, when the petroleum asphalt is solid, the pretreatment adopts a method of first crushing and then screening, and the solid petroleum asphalt is screened using a 200-mesh screen.

[0007] Furthermore, after the carbon source is mixed with deionized water, a small amount of hydrogen peroxide is added. The mass concentration of the hydrogen peroxide is 30%, and the amount of the added hydrogen peroxide is 1-2‰ of the volume of the deionized water.

[0008] Furthermore, when the petroleum asphalt is liquid, 80% ethanol is added for pretreatment.

[0009] Furthermore, a polytetrafluoroethylene filter membrane is used in step (4), and the pore size of the filter membrane is 0.45 μm.

[0010] Furthermore, the filter cake in step (4) is dried in an oven at 75-85° C. for 24 hours.

[0011] A catalyst for electrosynthesis of hydrogen peroxide has a pore structure and oxygen-containing groups are formed on the outer surface of the catalyst.

[0012] A catalyst for electrosynthesis of hydrogen peroxide, wherein the BET specific surface area of the catalyst is 70-80 m 2 / g.

[0013] In the present invention, a one-step method using a high-pressure reactor is adopted, and a supercritical state is reached in the high-pressure reactor, so that the carbon source, intermediate product and reaction reagent can be fully mixed and contacted in the system, so that the reaction can be carried out more uniformly and efficiently, avoiding the mass transfer resistance and reaction unevenness caused by phase interface problems, providing a homogeneous reaction environment for the carbonization reaction of the carbon source, and changing the chemical potential and reaction free energy of the reaction system, so that the aromatic ring-rich carbon source molecules can quickly connect with each other by sharing carbon atoms at a lower temperature to form a large conjugated system, so that the material structure gradually changes to a graphitized carbon structure. Under the continuous action of high temperature and high pressure, the carbonization process continues, heteroatoms are continuously removed in the form of small molecules, the carbon content gradually increases, and finally a carbonized product with a high carbon content is formed. The product has typical properties of carbon materials, such as high specific surface area, good electrical conductivity and chemical stability.

[0014] By adding a small amount of H2O2 to the reaction system, the O2 produced by its high-temperature decomposition can be dissolved in a large amount of supercritical water. The reaction system is more active and the oxidation capacity is significantly improved. The carbonization process can be completed in a shorter time and oxygen-containing groups can be introduced.

[0015] Beneficial effects of the present invention: The present invention uses petroleum asphalt rich in condensed aromatic hydrocarbons and high in carbon content as a carbon source. The raw materials are cheap and easily available. The carbon-based catalyst is prepared by a one-step method under low-temperature conditions. A small amount of hydrogen peroxide is added during the preparation process to accelerate the carbonization and oxidation process of the carbon source, significantly shortening the carbonization reaction time. In addition, oxygen-containing groups are introduced during the carbonization process. The prepared carbon-based catalyst has a high specific surface area, excellent conductivity and chemical stability, and has good selectivity in the electrocatalytic oxidation and reduction of O2 to produce H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a comparison chart of the selectivity of electrosynthesis of H2O2 by the catalysts prepared in Example 1 and Comparative Example 1; Figure 2 2 is a comparison chart of the selectivity of electrosynthesis of H2O2 by the catalysts prepared in Example 2 and Comparative Example 1; Figure 3 1 is a comparison chart of the selectivity of electrosynthesis of H2O2 by the catalysts prepared in Example 3 and Comparative Example 1; Figure 4 This is the selectivity diagram of H2O2 electrosynthesis of petroleum asphalt oxygen-containing carbon material prepared in comparative example 1. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Example 1: Solid petroleum asphalt was crushed with a grinder and sieved with a 200-mesh sieve. 10 g of the sieved petroleum asphalt powder was weighed and mixed evenly with 300 mL of deionized water and 0.5 mL of 30% H2O2. The mixture was then transferred into a 500 mL high-pressure reactor and reacted at 200°C for 1.5 h. After the reactor was cooled to room temperature, the reaction mixture was vacuum filtered through a microporous filter membrane with an average pore size of 0.45 μm, rinsed with distilled water until the filtrate was colorless and transparent, and the filter cake was dried at 80°C for 24 h to obtain a carbon-based catalyst.

[0019] The BET specific surface area of the prepared carbon-based catalyst was determined to be 80 m 2 / g, and its selectivity for electrocatalytic O2 reduction to H2O2 was 92%. The rotating ring disk electrode (RRDE) test result showed that -0.4 V vs. RHE corresponds to a disk current density of 3.8 mA / cm 2 .

[0020] Example 2: Solid petroleum asphalt was crushed with a grinder and sieved with a 200-mesh sieve. 10 g of the sieved petroleum asphalt powder was weighed and mixed evenly with 300 mL of deionized water. The mixture was then transferred into a 500 mL high-pressure reactor and reacted at 240° C. for 3 h. After the reactor was cooled to room temperature, the reaction mixture was vacuum filtered through a microporous filter membrane with an average pore size of 0.45 μm, rinsed with distilled water until the filtrate was colorless and transparent, and the filter cake was dried at 80° C. for 24 h to obtain a carbon-based catalyst.

[0021] The BET specific surface area of the prepared carbon-based catalyst was determined to be 70 m 2 / g Its electrocatalytic O2 reduction to H2O2 selectivity is 91%, and its rotating ring disk electrode (RRDE) test result is -0.4 V vs. RHE corresponding to the disk current density of 3.5 mA / cm 2 .

[0022] Example 3: Weigh 10 g of liquid petroleum asphalt, stir and mix with 30 mL of ethanol and 270 mL of deionized water, transfer to a 500 mL high-pressure reactor, and react at 240°C for 5 hours. After the reactor is cooled to room temperature, the reaction mixture is vacuum filtered through a microporous filter membrane with an average pore size of 0.45 μm, rinsed with distilled water until the filtrate is colorless and transparent, and the filter cake is dried at 80°C for 24 hours to obtain an oxygen-rich carbon material.

[0023] The BET specific surface area of the prepared oxygen-rich carbon material was determined to be 75 m 2 / g, and its selectivity for electrocatalytic O2 reduction to H2O2 was 90%, and its rotating ring disk electrode (RRDE) test result was -0.4 V vs. RHE, corresponding to a disk current density of 3.7 mA / cm 2 .

[0024] Comparative Example 1: Weigh 10g of liquid petroleum asphalt into a quartz boat, place the quartz boat in a tube furnace, and heat it to 800℃ at a heating rate of 5℃ in an argon atmosphere. Maintain 800℃ for 2h. After the furnace temperature drops to room temperature, remove the quartz boat, remove the black carbon product in the quartz boat, grind it into powder, and pass it through a 200-mesh sieve. Weigh 1g of the sieved carbon material into a flask, add 1L of 12mol / L concentrated nitric acid, and heat and reflux at 85℃ for 24h. After the reaction liquid drops to room temperature, filter it with a polytetrafluoroethylene filter membrane with an average pore size of 0.45μm. Rinse with deionized water until the filtrate is neutral. Dry the filter cake at 80℃ for 24h to obtain an oxygen-rich carbon material.

[0025] The BET specific surface area of the prepared oxygen-rich carbon material was determined to be 6 m 2 / g, by Figure 4 The selectivity of electrocatalytic O2 reduction to H2O2 is 90%, and the rotating ring disk electrode (RRDE) test result is -0.4 V vs. RHE, corresponding to a disk current density of 1.5 mA / cm 2 .

[0026] Depend on Figure 1-Figure 4 The results show that the selectivity of the carbon-based catalyst obtained by the preparation method of the present invention in the electrocatalytic synthesis of hydrogen peroxide is higher than that of the oxygen-containing carbon material prepared by the high-temperature calcination method. The oxygen-containing carbon material prepared by the high-temperature calcination method, as shown by the BET specific surface area and the disk current density measured by the rotating ring disk electrode, has a significantly higher specific surface area than the high-temperature calcination method (increased by more than 10 times), and the catalytic activity of the electrocatalytic O2 reduction to synthesize H2O2 is also significantly improved (increased by more than 2 times).

Claims

1. A method for preparing a catalyst for electrosynthesis of hydrogen peroxide, characterized in that: The steps include: (1) Petroleum asphalt is used as raw material and pretreated as a carbon source; (2) Add deionized water to the carbon source obtained by pretreatment in step (1), stir thoroughly, and transfer to a high-pressure reactor. The amount of deionized water added is 10-30 times the mass of the carbon source. (3) The mixture in the reactor is reacted at 200-240°C for 1.5-5 hours, and then the reactor is cooled to room temperature; (4) The reactants obtained in the reactor were filtered through microporous vacuum, rinsed with distilled water until the filtrate was transparent, and the filter cake was dried to obtain the catalyst.

2. The method for preparing a catalyst for electrosynthesis of hydrogen peroxide according to claim 1, wherein: When the petroleum asphalt is solid, the pretreatment adopts the method of first crushing and then screening, and the solid petroleum asphalt is screened using a 200-mesh screen.

3. The method for preparing a catalyst for electrosynthesis of hydrogen peroxide according to claim 2, wherein: After the carbon source is mixed with deionized water, a small amount of hydrogen peroxide is added. The mass concentration of the hydrogen peroxide is 30%, and the amount of the added hydrogen peroxide is 1-2‰ of the volume of the deionized water.

4. The method for preparing a catalyst for electrosynthesis of hydrogen peroxide according to claim 1, wherein: When the petroleum asphalt is liquid, 80% ethanol is added for pretreatment.

5. The method for preparing a catalyst for electrosynthesis of hydrogen peroxide according to claim 1, wherein: In the step (4), a polytetrafluoroethylene filter membrane is used for filtration, and the pore size of the filter membrane is 0.45 μm.

6. The method for preparing a catalyst for electrosynthesis of hydrogen peroxide according to claim 1, wherein: In step (4), the filter cake is dried in an oven at 75-85° C. for 24 hours.

7. The catalyst for electrosynthesis of hydrogen peroxide obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The catalyst has a pore structure, and oxygen-containing groups are formed on the outer surface of the catalyst.

8. The catalyst for electrosynthesis of hydrogen peroxide according to claim 7, wherein: The BET specific surface area of the catalyst is 70-80 m 2 / g.

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