A method and application of preparing biomass bulk carbon catalyst by ionic liquid pretreatment

Abstract

The present invention discloses a method and application for preparing a biomass block carbon catalyst by ionic liquid pretreatment. The method comprises the following steps: placing block agricultural and forestry biomass in an ionic liquid and rapidly stirring at high temperature, then filtering to obtain a mixture A; adding water, a nitrogen source and a transition metal salt to the mixture A and ultrasonically stirring, then freeze-drying to obtain a mixture B; and carbonizing the mixture B to obtain the biomass block carbon catalyst. The material has a three-dimensional interconnected pore structure that can provide a microenvironment for chemical reactions and is conducive to mass transfer. Compared with traditional powder catalysts, it has a higher catalytic active sites per unit area, better working stability, and prevents the active sites of the catalyst from being blocked. In addition, the preparation process of the material is simple, wherein the ionic liquid is reusable, and the raw material source is wide and low-priced, which can effectively reduce the production cost of porous block carbon materials and is easy to prepare on a large scale, providing an effective way to high-value utilization of wood.

Description

Technical Field

[0001] The present invention belongs to the field of high-value utilization of agricultural and forestry biomass resources, and specifically relates to a method for preparing a biomass block carbon catalyst by ionic liquid pretreatment and its application. Background Art

[0002] Energy crisis and environmental pollution have made people urgently develop energy storage systems with high energy density and high safety. Fuel cells and metal-air batteries not only have the above advantages, but also have attracted widespread attention due to their cleanliness, low cost and ease of use. For fuel cells, cathode catalysts are the most important part affecting battery performance. However, an important problem facing cathode catalysts is the slow four-electron oxygen reduction reaction. At present, platinum-based catalysts have become the most widely used cathode catalysts due to their ultra-low overpotential and ultra-high activity in the oxygen reduction process. However, platinum-based materials are expensive, have limited reserves, poor stability, and are easily poisoned. Therefore, the development of highly active, inexpensive, green, sustainable, and stable catalysts to replace platinum-based catalysts is of epoch-making significance for scientific research and industrial applications.

[0003] In recent years, porous carbon-based catalysts have attracted extensive research from both academics and industry due to their excellent resistance to poisoning and stability. Existing methods for preparing porous carbon catalysts typically utilize template-based approaches. However, these methods require multiple steps, such as the preparation of carbon precursors in bottom-up synthesis and the removal of templates during etching and purification. This not only increases the cost of large-scale production but also pollutes the environment. Furthermore, the materials synthesized by bottom-up methods are generally in powder form and therefore cannot be self-supporting. Furthermore, powdered catalysts require the addition of additional polymer binders during application, which can block active sites on the catalyst surface and further increase the internal impedance of the catalytic layer, leading to strong ohmic polarization effects that negatively impact the actual electrocatalytic process. Naturally abundant and renewable agricultural and forestry biomass resources, with their naturally occurring pore structures and readily available, are excellent precursors for preparing porous carbon catalysts. However, naturally derived agricultural and forestry biomass carbon materials have a low specific surface area, a low proportion of micropores and mesopores, and a low number of active sites. Therefore, developing an efficient, inexpensive, and sustainable method for the large-scale preparation of porous carbon would have a significant impact on numerous fields. Summary of the Invention

[0004] In view of the problems of expensive raw materials, complex processes, and the use of strong acid and strong base etching in the preparation method of doped porous carbon-based catalysts, the purpose of the present invention is to provide a method for preparing biomass bulk carbon catalysts by ionic liquid pretreatment. The method of the present invention is in line with the concept of green and sustainable development, and is simple, easy to implement, and low-cost, and has important application prospects in the fields of catalysis and energy storage. The material prepared by the present invention has the advantages of rich micro-mesopore ratio, good mechanical properties, high density of active sites, and large specific surface area.

[0005] Another object of the present invention is to provide a biomass block carbon catalyst prepared by the above method.

[0006] Another object of the present invention is to provide an application of the biomass bulk carbon catalyst, which can be applied in the fields of catalysis, energy storage, environmental remediation, etc.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a biomass bulk carbon catalyst by ionic liquid pretreatment comprises the following steps:

[0009] (1) placing bulk agricultural and forestry biomass in an ionic liquid and heating and stirring at 60-120° C. for 0.1 h-24 h, followed by filtration to obtain a mixture A;

[0010] (2) adding water, a nitrogen source, and a transition metal salt to the mixture A obtained in step (1), stirring the mixture with ultrasound, and then freeze-drying the mixture to obtain a mixture B;

[0011] (3) Carbonizing the mixture B at 600-1100° C. for 0.2-10 h under an inert atmosphere to obtain a biomass bulk carbon catalyst prepared by the ionic liquid pretreatment.

[0012] This invention uses bulk agricultural and forestry biomass as raw material. The selective, directional dissolution of cellulose, hemicellulose, and lignin in the bulk agricultural and forestry biomass by ionic liquids creates abundant micro-mesopores. Nitrogen sources and transition metal salts are then used to control the density of active centers within the catalyst. The result is a biomass bulk carbon catalyst pretreated with ionic liquid. This material possesses a three-dimensional interconnected pore structure, providing a microenvironment conducive to chemical reactions and mass transfer.

[0013] Preferably, the size of the block-shaped agricultural and forestry biomass in step (1) is 5 cm*5 cm*0.5 cm.

[0014] Block catalysts can solve the following drawbacks of traditional powder catalysts: 1) The insulating polymer binder will block the active sites on the catalyst surface; 2) The insulating polymer binder will further increase the internal impedance of the catalytic layer, resulting in a strong ohmic polarization effect that has a negative impact on the actual electrocatalytic process; 3) Under actual industrial operating conditions, the current density is high, and the impact of a large amount of hydrogen and oxygen generated inside the pores of the catalytic layer will cause the catalyst to fall off, further reducing the stability of the electrode.

[0015] The water in step (2) can be distilled water, deionized water or ultrapure water.

[0016] Preferably, the bulk agricultural and forestry biomass in step (1) includes but is not limited to one of larch, eucalyptus, beech, birch, basswood, eucalyptus, cypress, fig and bamboo. Further preferably, the bulk agricultural and forestry biomass is eucalyptus.

[0017] Preferably, the mass ratio of the bulk agricultural and forestry biomass to the ionic liquid in step (1) is 1:0.1-30. Further preferably, the mass ratio is 1:20.

[0018] Preferably, the ionic liquid described in step (1) includes but is not limited to 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-allyl-3-methylimidazolium chloride, tetradecyldimethylbenzylammonium chloride, 1-hydroxyethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-benzyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium thiocyanate, 1,3-dimethylimidazolium dimethylphosphine, 1-ethyl-3-methylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium bromide, 1-allyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium diethyl phosphate and 1-butyl-3-methylimidazolium chloride. One or more. More preferably, the ionic liquid is 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

[0019] Ionic liquids can disrupt hydrogen bonds within and between cellulose molecules, effectively dissolving polysaccharide molecules. This allows for the controlled dissolution of biomass polysaccharides in the preparation of monolithic carbon catalysts, thereby regulating the micro-mesoporous ratio of the catalyst. Furthermore, ionic liquids are environmentally friendly and recyclable solvents, significantly reducing production costs.

[0020] Preferably, the heating and stirring in step (1) is performed at a speed of 50-2000 rpm. Further preferably, the heating and stirring in step (1) is performed at 80° C. and 600 rpm for 12 h.

[0021] Preferably, the nitrogen source in step (2) is one or more of ammonium chloride, urea, dicyandiamide, melamine, ethylenediamine, glucosamine, diammonium hydrogen phosphate, and ammonia. Further preferably, the nitrogen source is ammonium chloride.

[0022] Preferably, the mass ratio of the mixture A to the nitrogen source in step (2) is 1:0.2-30. Further preferably, the mass ratio of the mixture A to the nitrogen source is 1:20.

[0023] Preferably, the transition metal salt in step (2) is one or more of ferric chloride, cobalt chloride, nickel chloride, copper chloride, manganese chloride, ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, manganese nitrate, ferric sulfate, cobalt sulfate, nickel sulfate, copper sulfate, and manganese sulfate. Further preferably, the transition metal salt is manganese chloride.

[0024] Preferably, the mass ratio of the mixture A to the transition metal salt in step (2) is 1000:1-200. Further preferably, the mass ratio of the mixture A to the transition metal salt is 1000:7.2.

[0025] Preferably, the freezing in step (2) is -20°C freezing or liquid nitrogen freezing. Further preferably, the freezing is liquid nitrogen freezing.

[0026] Preferably, the inert atmosphere in step (3) is a nitrogen atmosphere.

[0027] Preferably, the carbonization process in step (3) is to increase the temperature from room temperature to 600-1100°C at a rate of 0.5-20°C / min and hold the temperature for 0.2-10 hours. More preferably, the heating rate is 5°C / min, the carbonization temperature is 900°C, and the holding time is 2 hours.

[0028] A biomass block carbon catalyst prepared by ionic liquid pretreatment is prepared by the above method.

[0029] The biomass bulk carbon catalyst prepared by the above-mentioned ionic liquid pretreatment can be applied in the fields of catalysis, energy storage, environmental remediation, etc.

[0030] The material prepared by the above method has the following advantages and beneficial effects:

[0031] (1) Based on blocky agricultural and forestry biomass, the raw materials are widely available and inexpensive, which can not only alleviate the excessive consumption of fossil resources and reduce production costs, but also realize the high-value utilization of forestry resources.

[0032] (2) Using ionic liquids to dissolve part of the cellulose, hemicellulose, and lignin in the biomass to regulate the micro-mesoporous ratio of the catalyst and thus the catalyst activity. This can solve the problems of complex process and high energy consumption brought by traditional preparation methods.

[0033] (3) The biomass block carbon catalyst prepared by the three-step method of the present invention has a simple preparation process, few steps, is easy to implement, and can be prepared on a large scale.

[0034] (4) The biomass bulk carbon catalyst prepared by the present invention has high oxygen reduction catalytic activity, and its onset potential (1.02V) and half-wave potential (0.875V) are both higher than those of the platinum carbon electrode (0.98V / 0.837V). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the SEM image of MSCN-2 prepared in Example 1.

[0036] Figure 2 This is the XPS graph of MSCN-2 prepared in Example 1.

[0037] Figure 3 These are the nitrogen adsorption and desorption curves of the catalysts prepared in Example 1 and Comparative Example 1.

[0038] Figure 4 Linear sweep voltammetry curves of the catalysts prepared in Examples 1, 6 and 7, and commercial Pt / C.

[0039] Figure 5 This is an optical photograph of the catalyst sample of Example 1. DETAILED DESCRIPTION

[0040] The present invention will be described in further detail below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically noted, conventional techniques can be used.

[0041] Example 1

[0042] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 12 h, and then filtered to obtain a mixture A;

[0043] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0044] (3) Place the mixture B in a tube furnace, heat it from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for 2 hours, and cool it to room temperature after the reaction is completed to obtain the biomass bulk carbon catalyst prepared by the ionic liquid pretreatment. The obtained catalyst is marked as MSCN-2. Figure 1 The SEM image shows that the carbonized material has a rich three-dimensional pore structure. Figure 2 The XPS spectra of the carbon nanotubes show that nitrogen is successfully doped into the bulk carbon in different forms. Figure 3 As shown, it can reach 968.7m 2 / g, and has abundant micro-mesopores, which is beneficial to catalytic reactions. Figure 4 The linear sweep voltammetry curve of the catalyst shows that the ORR half-wave potential of the catalyst (0.875V) is higher than that of the platinum carbon electrode (0.837V). Figure 5 A larger-scale photo of the catalyst is shown.

[0045] Example 2

[0046] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 12 h, and then filtered to obtain a mixture A;

[0047] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0048] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 800°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled MSCN-800.

[0049] Example 3

[0050] (1) Eucalyptus wood (5 cm*5 cm*0.5 cm) (approximately 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and rapidly stirred at 80°C for 12 h, followed by filtration to obtain a mixture A;

[0051] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0052] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 1000°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, it was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The resulting catalyst was labeled MSCN-1000.

[0053] Example 4

[0054] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 12 h, and then filtered to obtain a mixture A;

[0055] (2) adding deionized water, nitrogen source ammonium chloride, and ferric chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to ferric chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0056] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled FSCN.

[0057] Example 5

[0058] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 12 h, and then filtered to obtain a mixture A;

[0059] (2) adding deionized water, nitrogen source ammonium chloride, and cobalt chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to cobalt chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0060] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by the ionic liquid pretreatment. The obtained catalyst was labeled CSCN.

[0061] Example 6

[0062] (1) Eucalyptus wood (5 cm*5 cm*0.5 cm) (approximately 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and rapidly stirred at 80°C for 12 h, followed by filtration to obtain a mixture A;

[0063] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:18 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0064] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled MSCN-5.

[0065] Example 7

[0066] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 12 h, and then filtered to obtain a mixture A;

[0067] (2) adding deionized water, nitrogen source ammonium chloride, and 3.6 mg of manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:3.6 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0068] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled MSCN-1.

[0069] Example 8

[0070] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 6 h, followed by filtration to obtain a mixture A;

[0071] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0072] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled MSCN-J6.

[0073] Example 9

[0074] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and stirred at 80°C (500 rpm) for 24 h, followed by filtration to obtain a mixture A;

[0075] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0076] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by ionic liquid pretreatment. The obtained catalyst was labeled MSCN-J24.

[0077] Example 10

[0078] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-hexyl-3-methylimidazolium diethyl phosphate was 1:20, g / g) and stirred at 80°C (500 rpm) for 24 h, and then filtered to obtain a mixture A;

[0079] (2) adding deionized water, nitrogen source ammonium chloride, and manganese chloride to mixture A and stirring with ultrasound, wherein the mass ratio of mixture A to ammonium chloride is 1:20 (g / g), and the mass ratio of mixture A to manganese chloride is 1000:7.2 (g / g), followed by freezing with liquid nitrogen and freeze-drying with a freeze dryer to obtain mixture B;

[0080] (3) Mixture B was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a biomass bulk carbon catalyst prepared by the ionic liquid pretreatment. The obtained catalyst was labeled MPCN.

[0081] Comparative Example 1

[0082] (1) Eucalyptus wood (5 cm x 5 cm x 0.5 cm) (approximately 5.3 g) was placed in a tubular furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for 2 h. After the reaction was complete, it was cooled to room temperature to obtain an untreated bulk carbon catalyst. The resulting catalyst is labeled C.

[0083] Comparative Example 2

[0084] (1) Eucalyptus wood with a size of 5 cm*5 cm*0.5 cm (about 5.3 g) was placed in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (the mass ratio of eucalyptus wood to 1-butyl-3-methylimidazolium trifluoromethanesulfonate was 1:20, g / g) and rapidly stirred at 80°C for 12 h, and then filtered to obtain mixture A.

[0085] (2) adding deionized water and nitrogen source ammonium chloride to mixture A and ultrasonically stirring the mixture, wherein the mass ratio of mixture A to ammonium chloride is 1:20 g / g, and then freezing the mixture with liquid nitrogen and freeze-drying the mixture with a freeze dryer to obtain mixture B;

[0086] (3) The mixture B in step (2) was placed in a tube furnace and heated from room temperature to 900°C at a heating rate of 5°C / min in a nitrogen atmosphere for carbonization for 2 hours. After the reaction was completed, it was cooled to room temperature to obtain the biomass bulk carbon catalyst prepared by the ionic liquid pretreatment. The obtained catalyst was labeled SCN.

[0087] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. Application of a biomass bulk carbon catalyst in an oxygen reduction reaction, characterized in that: The biomass block carbon catalyst is prepared by the following steps: (1) A bulk agricultural and forestry biomass was placed in an ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate and heated and stirred at 80°C for 12 hours, followed by filtration to obtain a mixture A; the bulk agricultural and forestry biomass was eucalyptus; the mass ratio of the bulk agricultural and forestry biomass to the ionic liquid was 1:20; the size of the bulk agricultural and forestry biomass was 5 cm*5 cm*0.5 cm; (2) adding water, a nitrogen source and a transition metal salt to the mixture A obtained in step (1), stirring the mixture under ultrasonic conditions, and freeze-drying the mixture to obtain a mixture B; wherein the nitrogen source is ammonium chloride, the transition metal salt is manganese chloride, the mass ratio of the mixture A to the nitrogen source is 1:20, and the mass ratio of the mixture A to the transition metal salt is 1000:3.6-18; (3) Carbonizing the mixture B at 900° C. for 2 h under an inert atmosphere to obtain the biomass bulk carbon catalyst.

2. The use according to claim 1, characterized in that The freezing in step (2) is -20°C freezing or liquid nitrogen freezing.

3. The use according to claim 1, characterized in that The inert atmosphere in step (3) refers to a nitrogen atmosphere; The carbonization process in step (3) is to increase the temperature from room temperature to 900°C at a rate of 0.5-20°C / min and keep the temperature for 2 hours.

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