Preparation method of nitrogen-oxygen co-doped microporous carbon based on pre-oxidation assisted sodium amide activation

Abstract

The invention discloses a preparation method of nitrogen-oxygen co-doped microporous carbon based on pre-oxidation assisted sodium amide activation, and the method comprises the following steps: 1, carrying out mechanical crushing and screening on raw coal to obtain powder with a target particle size; 2, weighing coal powder, putting the coal powder into a muffle furnace, heating the coal powder to a target temperature in an air atmosphere, preserving heat for 2-4 hours, then naturally cooling the coal powder to room temperature, and taking out the coal powder for later use; 3, weighing the air pre-oxidized pulverized coal obtained in the step 2, adding an activating agent, and performing solid-phase premixing in a mortar; heating the mixture to a target temperature in an inert protective atmosphere, preserving heat for 0.5-2 hours, cooling to room temperature, and taking out; and 4, repeatedly washing the mixture obtained in the step 3 with deionized water until the pH value reaches 7, and then drying with hot air to obtain the nitrogen-oxygen co-doped microporous carbon. According to the method, porous carbon with large specific surface area and high microporosity / ultra-microporosity is prepared at a lower activation temperature in one step, and efficient doping of nitrogen and oxygen atoms is realized.

Description

Technical Field

[0001] This invention relates to a method for preparing a gas adsorption material, specifically a method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation. Background Technology

[0002] Fossil fuels, represented by coal, have faced resource shortages and emitted large amounts of CO2 over a long period, exacerbating environmental problems such as global warming. Compared to developing clean energy, carbon capture and storage (CCS) technologies, such as post-combustion capture, are the most effective way to achieve low carbon emissions in the short term. Among various CCS technologies, physical adsorption based on solid porous materials shows high competitiveness due to its simplicity of operation, low energy consumption, and environmental friendliness. However, the large-scale application of this technology still faces challenges due to the lack of suitable adsorbents. Porous carbon, with its well-developed and tunable pore structure, abundant surface functional groups, and wide availability from low-cost precursors such as coal and biomass, is considered one of the most promising CO2 adsorbents. Among various precursors, coal is the main source of porous carbon, accounting for about two-thirds of total production. Furthermore, using coal as a raw material for porous carbon has higher economic value and lower carbon emissions compared to direct combustion as fuel.

[0003] Pores are crucial sites for CO2 adsorption on porous carbon, and their development determines the adsorption performance of porous carbon. Influenced by the pore-filling mechanism, constructing micropores (especially ultramicropores) with narrow pore sizes is considered an effective means to enhance CO2 adsorption on porous carbon. However, due to pore expansion during activation, it is difficult for porous carbon to simultaneously achieve high microporosity / ultramicroporosity while developing a large specific surface area, which severely limits the improvement of CO2 adsorption capacity. Constructing heteroatom functional groups is another effective means to enhance CO2 adsorption on porous carbon. This can be attributed to the fact that heteroatoms increase the Lewis basicity of the porous carbon surface, thereby enhancing the adsorption capacity of the carbon matrix for acidic CO2 molecules. Nevertheless, the introduction of heteroatoms not only requires a large amount of exogenous reagents, but also usually involves severe heteroatom removal during high-temperature activation, leading to high costs and low doping levels. Summary of the Invention

[0004] To address the challenges of achieving both well-developed pores and good micropore / ultramicropore properties in CO2 adsorption on porous carbon, as well as the difficulty in heteroatom doping, this invention provides a method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation. This method not only prepares porous carbon with both large specific surface area and high micropore / ultramicropore ratio in a single step at a relatively low activation temperature, but also achieves efficient doping of nitrogen and oxygen atoms. Compared with existing methods, this method is simpler, requires less energy, and is less polluting and corrosive. Furthermore, it enables synergistic control of pore size and heteroatom functional groups. The prepared porous carbon exhibits high CO2 adsorption capacity, selectivity, and appropriate adsorption heat, showing promising application prospects.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation includes the following steps:

[0007] Step 1, Grinding and Screening: The raw coal is mechanically crushed and screened to obtain powder of the target particle size;

[0008] Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Heat it to the target temperature in an air atmosphere and keep it at that temperature for 2-4 hours. Then let it cool naturally to room temperature and remove it for later use.

[0009] Step 3, sodium amino acid activation: Weigh the air pre-oxidized coal powder obtained in Step 2, add the activator, and perform solid-phase premixing in a mortar; then heat the mixture to the target temperature under an inert protective atmosphere, keep it at the temperature for 0.5~2h, and then cool it to room temperature and take it out. The mass ratio of activator to pre-oxidized coal is 1~3:1, and the activator is sodium amino acid.

[0010] Step 4: Obtaining porous carbon: The mixture obtained in Step 3 is repeatedly washed with deionized water until the pH reaches 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] (1) This invention uses coal as a low-cost raw material and optimizes the physicochemical structure of deashed coal through simple air pre-oxidation, resulting in a large number of initial pores, a loose carbon structure, abundant active sites (mainly O functional groups), and defects, effectively improving the reactivity of the deashed coal. The large number of initial pores and loose carbon structure in the pre-oxidized coal facilitates the diffusion of activators and, together with the active sites and defects, promotes the etching of the carbon matrix by the activators, thereby enabling porous carbon to form more micropores and ultramicropores. In addition, compared with deashed coal, the loose carbon structure and abundant O functional group active sites in the pre-oxidized coal provide a structural basis for the introduction of heteroatoms and introduce more N functional groups into the carbon skeleton by strengthening the O substitution reaction.

[0013] (2) This invention uses sodium amide as an activator and nitrogen source, and pre-oxidized coal as a precursor, to prepare nitrogen-oxygen co-doped porous carbon in a step-by-step activation process at a relatively low activation temperature of 400-600℃. Compared with the preparation of heteroatom-doped porous carbon by traditional chemical activation methods, this method not only eliminates the need for additional nitrogen source reagents, but also avoids the use of highly polluting and corrosive reagents (such as KOH and H3PO4). The porous carbon preparation process has significant advantages in terms of low cost and environmental friendliness. In addition, compared with traditional chemical activation methods, the lower activation temperature effectively avoids excessive expansion of the porous carbon pores and the removal of a large number of heteroatoms; by optimizing and controlling the activation temperature and the amount of sodium amide added, the prepared porous carbon has a large specific surface area (2018 m²). 2 With its high microporosity (94.32%) and ultramicroporosity (60.55%), as well as appropriate heteroatom doping (N content: 3.90 at.%; O content: 16.12 at.%), porous carbon exhibits good CO2 adsorption performance. Attached Figure Description

[0014] Figure 1 This is a flowchart of the preparation method of the present invention.

[0015] Figure 2 Nitrogen adsorption isotherms for the deashed and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3.

[0016] Figure 3 The XRD patterns are of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3.

[0017] Figure 4 Raman spectra of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3.

[0018] Figure 5 The FTIR spectra of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are shown.

[0019] Figure 6XPS spectra of the deashed and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3.

[0020] Figure 7 TEM images of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3.

[0021] Figure 8 Nitrogen adsorption isotherms of the porous carbon described in Comparative Examples 1-3 and Examples 1-3.

[0022] Figure 9 These are SEM comparison images of the porous carbon described in Comparative Examples 1-3 and Examples 1-3.

[0023] Figure 10 The XRD statistical spectra of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are shown.

[0024] Figure 11 Raman statistical maps of the porous carbon described in Comparative Examples 1-3 and Examples 1-3.

[0025] Figure 12 XPS spectra of the porous carbon described in Comparative Examples 1-3 and Examples 1-3. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0027] This invention provides a method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation. First, air pre-oxidation is used to form numerous initial pores, oxygen functional group active sites, defects, and a loose carbon structure in the precursor coal, effectively improving its reactivity. Then, using sodium amide as an activator and nitrogen source, nitrogen-oxygen co-doped microporous carbon is prepared in a next step at a lower activation temperature. By changing the activation temperature, the synergistic regulation of the porous carbon's pore size (micropores / ultramicropores) and heteroatom functional groups (N and O) is achieved. Figure 1 As shown, the following steps are included:

[0028] Step 1, Grinding and Screening: The raw coal is mechanically crushed and screened to obtain powder of the target particle size. The raw coal can be any type of coal, including lignite, bituminous coal, and anthracite, such as Ningdong coal. The target particle size is 40-80 mesh. The raw coal needs to be washed with a combination of hydrochloric acid and hydrofluoric acid to remove ash. The concentration of both hydrochloric acid and hydrofluoric acid is 5 mol / L, and the acid washing temperature is 80℃.

[0029] Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Under an air atmosphere, heat it to the target temperature of 200-350℃ at a heating rate of 5-15℃ / min, hold it at that temperature for 2-4 hours, and then let it cool naturally to room temperature. Remove it for later use. The target temperature for air pre-oxidation should be determined based on the thermogravimetric curve of the coal type used in Step 1.

[0030] Step 3, Sodium Amino Acid Activation: Weigh an appropriate amount of the air-pre-oxidized coal powder obtained in Step 2 (hereinafter referred to as pre-oxidized coal, denoted as Y-ND), add the activator at a mass ratio of 1~3:1, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and perform programmed temperature-increasing activation using a tube furnace, with nitrogen as the inert protective atmosphere, heat to the target temperature at a rate of 5~15℃ / min, hold for 0.5~2h, and then cool down to room temperature at the same rate, and remove. The activator and pre-oxidized coal should be solid-phase premixed under inert gas protection; the activator is sodium amino acid; considering that the activation temperature has a significant impact on the porous structure of carbon and heteroatom doping, the target activation temperature is adjusted to 400~600℃; the nitrogen flow rate is 200~300mL / min.

[0031] Step 4: Obtaining porous carbon: The mixture obtained in Step 3 is repeatedly washed with deionized water until the pH reaches 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon, wherein the microporosity of the nitrogen-oxygen co-doped microporous carbon should be higher than 80%.

[0032] The innovation of this invention lies in the sodium amino acid activation stage in step three. Using pre-oxidized coal as a precursor and sodium amino acid as an activator and nitrogen source, nitrogen-oxygen co-doped porous carbon is prepared in a simple one-step activation method. The pore structure and heteroatom doping amount of the porous carbon can be controlled by changing the activation temperature.

[0033] Example 1:

[0034] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0035] Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Under air atmosphere, heat it to the target temperature of 300℃ at a heating rate of 10℃ / min, hold it at that temperature for 3 hours, and then let it cool naturally to room temperature before taking it out for use.

[0036] Step 3, sodium amino acid activation: Weigh an appropriate amount of the pre-oxidized coal obtained in Step 2, add sodium amino acid at a mass ratio of 2:1 of activator to pre-oxidized coal, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to 400℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0037] Step 4: Obtaining porous carbon: The mixture obtained in Step 3 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon, the sample of which was designated as Y400.

[0038] The porous carbon prepared in this embodiment has a specific surface area of ​​1100 m². 2 / g, pore volume 0.47 cm³ 3 / g, micropore volume is 0.43 cm³ 3 / g, with an ultramicropore volume of 0.34 cm³. 3 / g, microporosity is 92.38%; N content is 6.33 at.%, O content is 19.15 at.%.

[0039] Example 2:

[0040] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0041] Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Under air atmosphere, heat it to the target temperature of 300℃ at a heating rate of 10℃ / min, hold it at that temperature for 3 hours, and then let it cool naturally to room temperature before taking it out for use.

[0042] Step 3, sodium amino acid activation: Weigh an appropriate amount of the pre-oxidized coal obtained in Step 2, add sodium amino acid at a mass ratio of 2:1 between activator and pre-oxidized coal, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to 500℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0043] Step 4: Obtaining porous carbon: The mixture obtained in Step 3 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon. The sample was designated as Y500.

[0044] The porous carbon prepared in this embodiment has a specific surface area of ​​2018 m². 2 / g, pore volume is 0.88cm³ 3 / g, micropore volume is 0.83cm³ 3 / g, with an ultramicropore volume of 0.53cm³. 3 / g, microporosity is 94.32%; N content is 3.90 at.%, O content is 16.12 at.%.

[0045] Example 3:

[0046] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0047] Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Under air atmosphere, heat it to the target temperature of 300℃ at a heating rate of 10℃ / min, hold it at that temperature for 3 hours, and then let it cool naturally to room temperature before taking it out for use.

[0048] Step 3, sodium amino acid activation: Weigh an appropriate amount of the pre-oxidized coal obtained in Step 2, add sodium amino acid at a mass ratio of 2:1 of activator to pre-oxidized coal, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to 600℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0049] Step 4: Obtaining porous carbon: The mixture obtained in Step 3 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon, the sample of which was designated as Y600.

[0050] The porous carbon prepared in this embodiment has a specific surface area of ​​3104 m². 2 / g, pore volume is 1.57cm³ 3 / g, micropore volume is 1.29cm³ 3 / g, with an ultramicropore volume of 0.68cm³. 3 / g, microporosity 82.17%; N content 2.21 at.%, O content 11.36 at.%.

[0051] Comparative Example 1:

[0052] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0053] Step 2, sodium amino acid activation: Weigh an appropriate amount of the deashed coal obtained in Step 1 (denoted as ND), add sodium amino acid at a mass ratio of 2:1 of activator to deashed coal, and premix the mixture in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to the target temperature of 400℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0054] Step 3: Obtaining porous carbon: The mixture obtained in Step 2 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon. The sample was designated as T400.

[0055] The porous carbon prepared in this comparative example has a specific surface area of ​​900 m². 2 / g, pore volume is 0.38cm³ 3 / g, micropore volume is 0.35cm³ 3 / g, with an ultramicropore volume of 0.27cm³. 3 / g, microporosity is 92.55%; N content is 2.82 at.%, O content is 18.16 at.%.

[0056] Comparative Example 2:

[0057] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0058] Step 2, sodium amino acid activation: Weigh an appropriate amount of the deashed coal obtained in Step 1 (denoted as ND), add sodium amino acid at a mass ratio of 2:1 between activator and deashed coal, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to the target temperature of 500℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0059] Step 3: Obtaining porous carbon: The mixture obtained in Step 2 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon. The sample was designated as T500.

[0060] The porous carbon prepared in this comparative example has a specific surface area of ​​1966 m². 2 / g, pore volume is 0.96cm³ 3 / g, micropore volume is 0.80cm³ 3 / g, with an ultramicropore volume of 0.52cm³. 3 / g, microporosity is 93.02%; N content is 2.53 at.%, O content is 14.61 at.%.

[0061] Comparative Example 3:

[0062] Step 1: Grinding and sieving: The Ningdong coal is mechanically crushed and sieved to obtain 40-80 mesh powder.

[0063] Step 2, sodium amino acid activation: Weigh an appropriate amount of the deashed coal obtained in Step 1 (denoted as ND), add sodium amino acid at a mass ratio of 2:1 of activator to deashed coal, and perform solid-phase premixing in a mortar; then place the mixture in a crucible and activate it by programmed heating in a tube furnace with nitrogen as the inert protective atmosphere, heating to the target temperature of 600℃ at a rate of 5℃ / min, holding for 1 hour, and then cooling to room temperature at the same rate before taking it out.

[0064] Step 3: Obtaining porous carbon: The mixture obtained in Step 2 was repeatedly washed with deionized water until the pH reached 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon. The sample was designated as T600.

[0065] The porous carbon prepared in this comparative example has a specific surface area of ​​2949 m². 2 / g, pore volume 1.50cm³ 3 / g, micropore volume is 1.22cm³ 3 / g, with an ultramicropore volume of 0.65cm³. 3 / g, microporosity is 81.33%; N content is 2.44 at.%, O content is 10.16 at.%.

[0066] The nitrogen adsorption isotherms of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are as follows: Figure 2 As shown. The XRD patterns of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 3 As shown. The Raman spectra of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 4 As shown. The FTIR spectra of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 5 As shown. The XPS spectra of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 6 As shown. TEM images of the deashed coal and pre-oxidized coal described in Comparative Examples 1-3 and Examples 1-3 are shown below. Figure 7 As shown. The nitrogen adsorption isotherms of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 8 As shown. Comparative SEM images of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are shown below. Figure 9 As shown. The XRD statistical spectra of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 10 As shown. The Raman statistical spectra of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 11 As shown. The XPS spectra of the porous carbon described in Comparative Examples 1-3 and Examples 1-3 are as follows. Figure 12 As shown.

[0067] This invention uses coal as raw material and activates sodium amide with air pre-oxidation to synthesize microporous carbon with well-developed pore structure and high N / O doping in one step at a relatively low activation temperature (400~600℃) and a relatively low alkali-to-carbon ratio (2:1). This provides new insights into the simple synthesis of low-cost, high-performance porous carbon for CO2 adsorption.

[0068] (1) Compared to raw coal, air pre-oxidation causes raw coal to form more pores and a more loose and disordered carbon framework (d 002 Increase, L a and L c(Reduced) and higher density of oxygen functional groups and defects. These structures are beneficial to the dispersion and pore formation of sodium amide during the activation stage, enabling porous carbon to form more micropores and ultramicropores. On the other hand, they increase the number of active sites in the raw materials, which is conducive to the introduction of nitrogen atoms.

[0069] (2) Activation temperature is a crucial factor affecting the porosity and functional groups of porous carbon. With increasing activation temperature, the volume of micropores and ultramicropores increases, while the pore size expands significantly, leading to a decrease in microporosity and ultramicroporosity. Furthermore, high temperatures are unfavorable for the introduction of heteroatoms. Thanks to optimized activation temperature and oxidation pretreatment, Y500 achieved synergistic construction of pores and N / O functional groups. Porous carbon exhibits a porosity as high as 2018 m... 2 It has a specific surface area of ​​ / g, a microporosity of 94.32% and an ultramicroporosity of 60.55%, and appropriate N doping (3.90 at%) and O doping (16.12 at%).

Claims

1. A method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation, characterized in that... The method includes the following steps: Step 1, Grinding and Screening: The raw coal is mechanically crushed and screened to obtain powder of the target particle size; Step 2, Pre-oxidation treatment: Weigh an appropriate amount of pulverized coal and place it in a muffle furnace. Heat it to the target temperature in an air atmosphere and keep it at that temperature for 2-4 hours. Then let it cool naturally to room temperature and remove it for later use. Step 3, sodium amino acid activation: Weigh the air pre-oxidized coal powder obtained in Step 2, add the activator, and perform solid-phase premixing in a mortar; then heat the mixture to the target temperature under an inert protective atmosphere, keep it at the temperature for 0.5~2h, and then cool it to room temperature and take it out. The mass ratio of activator to pre-oxidized coal is 1~3:1, and the activator is sodium amino acid. Step 4: Obtaining porous carbon: The mixture obtained in Step 3 is repeatedly washed with deionized water until the pH reaches 7, and then dried with hot air to obtain nitrogen-oxygen co-doped microporous carbon.

2. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step one, the raw coal is one of lignite, bituminous coal, or anthracite.

3. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 2, characterized in that... The raw coal needs to be washed with a combination of hydrochloric acid and hydrofluoric acid to remove ash. The concentration of both hydrochloric acid and hydrofluoric acid is 5 mol / L, and the acid washing temperature is 80℃.

4. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step one, the target particle size is 40-80 mesh.

5. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step two, the temperature is increased to the target temperature of 200-350°C at a heating rate of 5-15°C / min.

6. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step three, nitrogen is used as an inert protective atmosphere, and the temperature is heated to the target temperature of 400-600℃ at a rate of 5-15℃ / min. After holding at this temperature for 0.5-2 hours, the temperature is cooled down to room temperature at the same rate.

7. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 6, characterized in that... The nitrogen flow rate is 200~300 mL / min.

8. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step three, the activator and pre-oxidized coal are premixed in a solid phase under the protection of an inert gas.

9. The method for preparing nitrogen-oxygen co-doped microporous carbon based on pre-oxidation-assisted sodium amide activation according to claim 1, characterized in that... In step four, the microporosity of the nitrogen-oxygen co-doped microporous carbon is higher than 80%.

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