Method for preparing high-entropy spinel / biochar composite material by Joule thermal shock method and application of high-entropy spinel / biochar composite material

Abstract

The invention belongs to the technical field of nano material synthesis and volatile organic compounds (VOCs) degradation, and particularly relates to a method for preparing a high-entropy spinel / biochar composite material by using a Joule thermal shock method and application of the high-entropy spinel / biochar composite material. The preparation method comprises the following steps: firstly, forming gel from metal salt precursors and biomass through a sol-gel method, and then rapidly synthesizing the precursors into the high-entropy spinel by adopting Joule thermal shock. The biochar in the composite material prepared by the invention is of a wormlike lamellar structure, and the high-entropy spinel is polygonal particles and is uniformly loaded on the biochar. Due to the high-entropy effect and lattice distortion effect of the composite material, the number of oxygen vacancies of the material can be obviously increased, defect sites can be formed on the surface of the material through instant energy impact, the catalytic performance of the material can be improved, and the catalytic material can efficiently convert methylbenzene into carbon dioxide and water.

Description

Technical Field

[0001] The present invention relates to the technical fields of nanomaterial synthesis technology and VOCs degradation technology, and particularly relates to a method for preparing a high-entropy spinel / biochar composite material by using a Joule heat shock method and its application. Background Art

[0002] In recent years, the emissions of various industrial pollutants have brought a large number of environmental and health problems. In particular, the emissions of volatile organic compounds (VOCs) play a major role in the formation of photochemical smog and ozone pollution. VOCs compounds have high chemical stability and complexity, making their removal from the atmosphere an urgent problem to be solved. Among many VOCs treatment technologies, catalytic oxidation is considered to be a very promising method in industry due to its high conversion and degradation rate and the characteristic of no secondary pollution. The core is to develop a catalyst with high catalytic oxidation activity, and in particular, spinel oxides have attracted a great deal of attention.

[0003] High-entropy spinels are a class of oxides composed of five or more main elements, and the atomic fraction of each main element is greater than 5% and less than 35%. The concept of high-entropy spinels breaks through the limitations of the composition of traditional spinels. Through the arrangement and combination of multiple components and the adjustment of their contents, excellent catalytic performance is given to the spinels, and they show excellent performance in catalytic conversion of VOCs. However, high-entropy spinels have the disadvantages of difficult synthesis, often requiring a large amount of organic complexing agents, long reaction time and easy agglomeration leading to inactivation, which affect their application in catalytic conversion of VOCs. Summary of the Invention

[0004] Based on the above technical background, the present invention provides a method for preparing a high-entropy spinel / biochar composite material by using a Joule heat shock method. Using metal salt precursors and biomass such as chestnut shells, pomegranate peels, and oriental arborvitae as raw materials, a catalyst is synthesized by using the Joule heat shock method, realizing the high-value reuse of low-value solid waste.

[0005] The method for preparing a high-entropy spinel biochar composite material by using the Joule heat shock method includes the following steps:

[0006] (1) Dissolve the metal salt precursor in deionized water;

[0007] (2) Add the biomass powder to the solution prepared in (1). The dosage ratio of the metal salt precursor to the biomass is 0.004 mol: 2 - 6 g. Then, place the beaker in a water bath and heat it to 60 - 90 °C, stir evenly, maintain the temperature and let it stand for reaction for 6 - 10 h to form a gel; dry it in an oven and then grind it into powder;

[0008] (3) Put the powder prepared in (2) into a Joule heating device, and synthesize the high-entropy spinel / biochar composite by the Joule shock method under an air atmosphere.

[0009] Furthermore, the biomass powder is obtained by grinding biomass; the biomass sources include chestnut shells, pomegranate peels, Platycladus orientalis, walnut shells, pomelo peels, etc.

[0010] Furthermore, the metal salt precursor includes one or more of cobalt salts, manganese salts, nickel salts, iron salts, copper salts, and chromium salts.

[0011] Furthermore, when the metal salt precursor is composed of multiple metal salts, the molar masses of the metal salts are the same.

[0012] Preferably, the metal salt precursor is composed of 5 metal salts, and the molar masses of the metal salts are the same.

[0013] In some embodiments, the metal salt precursor is composed of manganese salt, copper salt, chromium salt, iron salt, and nickel salt, or composed of manganese salt, copper salt, nickel salt, iron salt, and cobalt salt, or composed of manganese salt, copper salt, chromium salt, nickel salt, and cobalt salt, or composed of manganese salt, copper salt, chromium salt, iron salt, and cobalt salt, or composed of manganese salt, chromium salt, nickel salt, iron salt, and cobalt salt.

[0014] Furthermore, the maximum temperature generated by the discharge parameters of the Joule heating device is 500 - 3000 °C; the parameters of the Joule thermal shock method are: the discharge voltage is 120 - 280 V, the discharge time is 0.5 - 1.5 s, and the number of times is 2 - 6 times.

[0015] Preferably, the resistance of the high-entropy spinel / biochar composite needs to be measured before the Joule heating device is turned on, and the resistance should be ≤ 6 Ω.

[0016] Application of the high-entropy spinel / biochar composite prepared by the above method in the catalytic conversion of VOCs.

[0017] Preferably, the application is to catalytically convert toluene into carbon dioxide and water.

[0018] In some embodiments, the specific steps of the application are as follows: Put the catalyst into the quartz tube of the fixed-bed reactor, bubble toluene through N 2 while using air as the balance gas, and introduce them into the reaction device at the same time. Then, heat the reaction furnace to the reaction temperature to carry out the catalytic conversion of toluene.

[0019] The reaction temperature can be determined according to the catalytic performance. For example, to achieve a toluene degradation rate of 99%, the reaction temperature is set to 265 - 280 °C.

[0020] Compared with the existing technology, the advantages of the present invention are:

[0021] The present invention makes full use of waste biomass to replace citric acid as a complexing agent in the sol-gel process, and at the same time, the biomass is carbonized at high temperature as a carrier for high-entropy spinel, combining the two organically. On the one hand, it solves the problems of waste biomass waste and environmental pollution, and on the other hand, it also solves the disadvantages of poor thermal stability of high-entropy spinel without a carrier and easy agglomeration leading to its inactivation. Due to the high-entropy effect and lattice distortion effect possessed by the composite material, the number of oxygen vacancies in the material can be significantly increased, and the instantaneous energy impact can form defect sites on the material surface, improving the catalytic performance of the material, thereby accelerating the catalytic reaction and enabling the catalytic material to efficiently convert toluene into carbon dioxide and water. Description of the Drawings

[0022] Figure 1 XRD patterns of the high-entropy spinel / biochar composite prepared in Example 1 and Comparative Example 1;

[0023] Figure 2 TEM image of the high-entropy spinel / biochar composite sample prepared in Example 1;

[0024] Figure 3 Performance graphs of the catalytic degradation of toluene by the high-entropy spinel / biochar composites prepared in Examples 1 to 3 and Comparative Examples 1 and 2. Detailed Embodiments

[0025] Example 1

[0026] (1) Take 4 g of chestnut shells, wash them with deionized water, dry them and grind them into powder for later use;

[0027] (2) Weigh 0.004 mol of each of the precursors Mn(CH 3 COO) 2 ·4H 2 O, Cu(NO 3 ) 2 ·3H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, and add 100 mL of deionized water, stir magnetically to mix them evenly for later use;

[0028] (3) Add the chestnut shell powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat it to 80 °C, stir evenly, maintain the temperature and let it stand for reaction for 9 h to form a gel. Dry it in an oven and then grind it into powder for standby;

[0029] (4) Load the precursor prepared in (3) into a quartz tube with a 12 mm inner diameter wrapped with all-graphite paper, plug both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm, slowly compress the plugs and measure the resistance, and stop compressing until the resistance is about 1 Ω. Install and align the temperature probe, and close the box. Set the discharge voltage to 200 V and the discharge time to 1 s, and repeat the discharge 4 times. After 4 discharges are completed, cool it to room temperature and then take out the quartz tube, pour out the powder after the reaction in the quartz tube, which is the high-entropy spinel / chestnut shell composite material; the XRD pattern of the high-entropy spinel / chestnut shell composite material is as Figure 1 shown. The peaks of the composite material correspond to the card (JCPDS: 01-1110), indicating that the material synthesis is successful. The TEM pattern of the high-entropy spinel / chestnut shell composite material is as Figure 2 shown. High-entropy spinel nanoparticles are evenly distributed on the biochar with a worm-like lamellar structure, indicating successful loading;

[0030] (5) Conduct a thermal catalytic experiment for toluene degradation in a fixed-bed reactor. Put the catalyst prepared in (4) into the quartz tube of the evaluation device, bubble toluene through N 2 , and use air as the balance gas, and introduce them into the reaction device at the same time. Test the initial toluene concentration of 1500 ppm and the space velocity of 20000 mL·g -1 ·h -1 . Then heat up the reaction furnace, record the real-time concentration every 5 °C, calculate the degradation rate of toluene, and use the temperature at which the degradation rate reaches 99% as the evaluation of the ability to degrade toluene, that is, T 99 . The performance diagram of the high-entropy spinel / chestnut shell composite material for catalytic degradation of toluene is as Figure 3 shown. T 99 is 265 °C, and the prepared material has a significant toluene degradation effect.

[0031] Example 2

[0032] (1) Take 2 g of Platycladus orientalis, wash it with deionized water, dry it and grind it into powder for standby;

[0033] (2) Weigh the precursors Mn(CH 3 COO·) 2 ·4H 2 O, Cu(NO 3 ) 2 ·3H 2 O, Cr(NO 3 ) 3 ·9H2 O, Fe(NO 3 ) 3 ·9H 2 O and Ni(NO 3 ) 2 ·6H 2 O, each 0.004 mol, and add 100 mL of deionized water, stir magnetically to mix evenly, and set aside;

[0034] (3) Add the thuja powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat to 80 °C, stir evenly, maintain the temperature and let it stand for reaction for 8 h to form a gel. Dry it in an oven and grind it into powder, and set aside;

[0035] (4) Load the precursor prepared in (3) into a quartz tube with a 12 mm inner diameter wrapped with graphite paper, block both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm, slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing, install and align the temperature probe, and close the box. Set the discharge voltage to 160 V and the discharge time to 0.8 s, and repeat the discharge 5 times. After 5 discharges, cool to room temperature and take out the quartz tube, pour out the powder after the reaction in the quartz tube, which is the high-entropy spinel / thuja composite material;

[0036] (5) The toluene catalytic degradation experiment is as in Example 1, and the performance diagram of the high-entropy spinel / thuja composite material for catalytic degradation of toluene is as Figure 3 shown, T 99 is 270 °C, and the prepared material has excellent toluene degradation effect.

[0037] Example 3

[0038] (1) Take 6 g of pomegranate peel, wash it with deionized water, dry it and grind it into powder, and set aside;

[0039] (2) Weigh the precursors Mn(CH 3 COO) 2 ·4H 2 O, Cu(NO 3 ) 2 ·3H 2 O, Cr(NO 3 ) 3 ·9H 2 O, Ni(NO 3 ) 2 ·6H 2 O and Co(NO 3 ) 2 ·6H 2 O, each 0.004 mol, and add 100 mL of deionized water, stir magnetically to mix evenly, and set aside;

[0040] (3) Add the pomegranate peel powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat it to 75 °C, stir evenly, maintain the temperature and let it stand for reaction for 7 h to form a gel. After drying in an oven, grind it into powder for standby;

[0041] (4) Load the precursor prepared in (3) into a quartz tube with a graphite paper full package and an inner diameter of 12 mm, block both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm, slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing, install and align the temperature probe, and close the box. Set the discharge voltage to 240 V and the discharge time to 1.2 s, and repeat the discharge 3 times. After 3 discharges are completed, cool to room temperature and take out the quartz tube, pour out the powder after reaction in the quartz tube, which is the high-entropy spinel / pomegranate peel composite material;

[0042] (5) The toluene catalytic degradation experiment is as in Example 1, and the performance graph of the high-entropy spinel / pomegranate peel composite material for catalytic degradation of toluene is as Figure 3 shown, T 99 is 275 °C, and the prepared material has a good toluene degradation effect.

[0043] Example 4

[0044] (1) Take 4 g of walnut shell, wash it with deionized water, dry it and grind it into powder for standby;

[0045] (2) Weigh the precursors Mn(CH 3 COO) 2 ·4H 2 O, Cu(NO 3 ) 2 ·3H 2 O, Cr(NO 3 ) 3 ·9H 2 O, Fe(NO 3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, 0.004 mol each, and add 100 mL of deionized water, stir magnetically to mix evenly for standby;

[0046] (3) Add the walnut shell powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat it to 60 °C, stir evenly, maintain the temperature and let it stand for reaction for 10 h to form a gel. After drying in an oven, grind it into powder for standby;

[0047] (4) Load the precursor prepared in (3) into a quartz tube with an inner diameter of 12 mm wrapped with all-graphite paper. Plug both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm. Slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing. Install and align the temperature probe, and close the chamber. Set the discharge voltage to 120 V and the discharge time to 0.5 s, and repeat the discharge 6 times. After 6 discharges are completed, cool to room temperature, take out the quartz tube, and pour out the reacted powder in the quartz tube, which is the high-entropy spinel / walnut shell composite material;

[0048] (5) The toluene catalytic degradation experiment is as in Example 1. The T99 for the high-entropy spinel / walnut shell composite material to catalytically degrade toluene is 280 °C, and the prepared material has good toluene degradation effect.

[0049] Example 5

[0050] (1) Take 4 g of pomelo peel, wash it with deionized water, dry it and grind it into powder for standby;

[0051] (2) Weigh the precursors Mn(CH 3 COO) 2 ·4H 2 O, Cr(NO 3 ) 3 ·9H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, each 0.004 mol, and add 100 mL of deionized water, stir magnetically to mix evenly for standby;

[0052] (3) Add the pomelo peel powder prepared in (1) to the solution prepared in (2), then put the beaker into a water bath and heat it to 90 °C, stir evenly, maintain the temperature and let it react for 6 h to form a gel. Dry it in an oven and grind it into powder for standby;

[0053] (4) Load the precursor prepared in (3) into a quartz tube with an inner diameter of 12 mm wrapped with all-graphite paper. Plug both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm. Slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing. Install and align the temperature probe, and close the chamber. Set the discharge voltage to 280 V and the discharge time to 1.5 s, and repeat the discharge 2 times. After 2 discharges are completed, cool to room temperature, take out the quartz tube, and pour out the reacted powder in the quartz tube, which is the high-entropy spinel / pomelo peel composite material;

[0054] (5) The toluene catalytic degradation experiment was carried out as in Example 1. The T99 of the high-entropy spinel / pomelo peel composite for catalytic degradation of toluene was 280 °C, indicating that the prepared material had good toluene degradation effect.

[0055] Comparative Example 1

[0056] (1) Take 4 g of chestnut shells, wash them with deionized water, dry and grind them into powder for later use.

[0057] (2) Weigh the precursors Mn(CH 3 COO) 2 ·4H 2 O, Cu(NO 3 ) 2 ·3H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H2O and Co(NO 3 ) 2 ·6H 2 O, 0.004 mol each, and add 100 mL of deionized water. Stir magnetically to make them mixed evenly for later use.

[0058] (3) Add the chestnut shell powder prepared in (1) to the solution prepared in (2). Then put the beaker into a water bath and heat it to 80 °C, stir evenly, maintain the temperature and let it stand for reaction for 8 h to form a gel. Dry it in an oven and then grind it into powder for later use.

[0059] (4) Load the precursor prepared in (3) into a crucible and put it into a muffle furnace for calcination at 500 °C for 4 h. After calcination, take it out and grind it into powder, which is the high-entropy spinel / chestnut shell composite. The XRD pattern of the high-entropy spinel / chestnut shell composite is as Figure 1 shown. The peaks of the composite correspond to the card (JCPDS: 01-1110), indicating that the material synthesis is successful.

[0060] (5) The toluene catalytic degradation experiment was carried out as in Example 1. The performance graph of the high-entropy spinel / chestnut shell composite for catalytic degradation of toluene is as Figure 3 shown. The T 99 was 310 °C. The toluene degradation effect of the prepared material had an obvious gap compared with all examples, and compared with the joule heat shock, the calcination time required in the muffle furnace was longer.

[0061] Comparative Example 2

[0062] (1) Weigh the precursor Mn(CH 3 COO) 2 ·4H2 O, Cu(NO 3 ) 2 ·3H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, 0.004 mol each, and add 100 mL of deionized water, stir magnetically to mix evenly, and set aside;

[0063] (2) Weigh 4 g of citric acid monohydrate and add it to the solution prepared in (1). Then, place the beaker in a water bath and heat it to 80 °C, stir evenly, and maintain the temperature for static reaction for 8 h to form a gel. Dry it in an oven and grind it into powder, and set aside;

[0064] (3) Load the precursor prepared in (2) into a quartz tube with an inner diameter of 12 mm wrapped with graphite paper. Use graphite electrode plugs with a diameter of 12 mm to block both ends of the quartz tube. Slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing. Install and align the temperature probe, and close the box. Set the discharge voltage to 200 V and the discharge time to 1 s, and repeat the discharge 4 times. After 4 discharges are completed, cool it to room temperature and take out the quartz tube, pour out the powder after the reaction in the quartz tube, which is the high-entropy spinel material;

[0065] (4) The toluene catalytic degradation experiment is as in Example 1. The performance graph of the high-entropy spinel material for catalytic degradation of toluene is as Figure 3 shown. T 99 is 320 °C. There is a large gap in the toluene degradation effect between the prepared material and Comparative Example 1. Moreover, compared with using biomass, using citric acid not only has no economic benefits but also cannot form a carrier after calcination, and has no promoting effect on the catalytic performance of the material.

[0066] Comparative Example 3

[0067] (1) Take 8 g of pomelo peel, wash it with deionized water, dry it and grind it into powder, and set aside;

[0068] (2) Weigh the precursor Mn(CH 3 COO) 2 ·4H 2 O, Cr(NO 3 ) 3 ·9H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, 0.004 mol each, and add 100 mL of deionized water, stir magnetically to mix evenly, and set aside;

[0069] (3) Add the pomelo peel powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat to 90 °C, stir evenly, maintain the temperature and let it stand for reaction for 6 h to form a gel. Dry it in an oven and grind it into powder, set aside;

[0070] (4) Load the precursor prepared in (3) into a fully enclosed graphite paper quartz tube with an inner diameter of 12 mm, block both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm, slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing, install and align the temperature probe, and close the box. Set the discharge voltage to 280 V and the discharge time to 1.5 s, and repeat the discharge 2 times. After 2 discharges, cool to room temperature and take out the quartz tube, pour out the powder after the reaction in the quartz tube, which is the high-entropy spinel / pomelo peel composite material;

[0071] (5) The toluene catalytic degradation experiment is as in Example 1. The T of the high-entropy spinel / pomelo peel composite material for catalytic degradation of toluene 99 is 328 °C. Due to excessive addition of pomelo peel, the biochar agglomerates after the thermal shock reaction, and the toluene degradation effect of the prepared material is poor.

[0072] Comparative Example 4

[0073] (1) Take 1 g of pomelo peel, wash it with deionized water, dry it and grind it into powder, set aside;

[0074] (2) Weigh the precursor Mn(CH 3 COO) 2 ·4H 2 O, Cr(NO 3 ) 3 ·9H 2 O, Ni(NO 3 ) 2 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O and Co(NO 3 ) 2 ·6H 2 O, 0.004 mol each, and add 100 mL of deionized water, stir magnetically to mix evenly, and set aside;

[0075] (3) Add the pomelo peel powder prepared in (1) to the solution prepared in (2), then place the beaker in a water bath and heat it to 90 °C, stir evenly, maintain the temperature and let it stand for reaction for 6 h to form a gel. Dry it in an oven and then grind it into powder for standby;

[0076] (4) Load the precursor prepared in (3) into a quartz tube with an inner diameter of 12 mm wrapped with graphite paper. Plug both ends of the quartz tube with graphite electrode plugs with a diameter of 12 mm. Slowly compress the plugs and measure the resistance until the resistance is about 1 Ω, then stop compressing. Install and align the temperature probe, and close the box. Set the discharge voltage to 280 V and the discharge time to 1.5 s, and repeat the discharge 2 times. After the 2 discharges are completed, cool it to room temperature and then take out the quartz tube. Pour out the powder after the reaction in the quartz tube, which is the high-entropy spinel / pomelo peel composite material;

[0077] (5) The toluene catalytic degradation experiment is as in Example 1. The T of the high-entropy spinel / pomelo peel composite material for catalytic degradation of toluene 99 is 319 °C. Since too little pomelo peel was added, the sol-gel complex reaction in the early stage was insufficient and the components were uneven, and the toluene degradation effect of the prepared material was poor.

[0078] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a high entropy spinel / biochar composite material using a Joule thermal shock method, characterized in that: The steps include: (1) preparing a metal salt precursor solution; (2) adding biomass powder, heating and stirring evenly, and then maintaining the temperature and allowing to stand to react to form a gel; (3) After the gel is dried, it is ground into powder and a high entropy spinel / biochar composite material is synthesized using the Joule thermal shock method.

2. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The metal salt precursor includes one or more of cobalt salt, manganese salt, nickel salt, iron salt, copper salt and chromium salt; the ratio of the metal salt precursor to biomass is 0.004 mol: 2-6 g.

3. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The biomass sources in step (2) include chestnut shells, pomegranate peels, arborvitae, walnut shells, and grapefruit peels.

4. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The heating and stirring temperature in step (2) is 60-90°C.

5. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The static reaction time in step (2) is 6-10 hours.

6. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The Joule thermal shock method in step (3) uses a Joule heating device.

7. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The parameters of the Joule thermal shock method in step (3) are: discharge voltage of 120 to 280 V, discharge time of 0.5 to 1.5 s, and number of times of 2 to 6 times.

8. The method for preparing a high entropy spinel / biochar composite material using Joule thermal shock method according to claim 1, characterized in that: The Joule thermal shock method in step (3) is carried out under air atmosphere.

9. A high entropy spinel / biochar composite material prepared by the method according to any one of claims 1 to 8.

10. Use of the high entropy spinel / biochar composite material as claimed in claim 9 in VOCs degradation.

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