Hydrothermal pretreatment cow dung-based hydrogen storage material and preparation method thereof

Abstract

The invention provides a hydrothermal pretreatment cow dung-based hydrogen storage material and a preparation method thereof, and belongs to the technical field of lignocellulose pretreatment and hydrogen storage materials. The method comprises the following steps: putting cow dung into a hydrothermal reaction kettle for hydrothermal pretreatment, and taking out the cow dung to obtain pretreated cow dung; the temperature of the hydrothermal pretreatment is 140-200 DEG C. The pretreatment time is 12 to 48 hours; and mixing the pretreated cow dung with an activating agent, and calcining in a nitrogen atmosphere to obtain the cow dung-based porous carbon material. The aggregation structure of lignocellulose is changed through hydrothermal pretreatment, the change of the aggregation structure of the material is beneficial to formation of more micropores, and compared with a porous carbon material formed by cow dung which is not subjected to hydrothermal pretreatment, the porous carbon material has better micropore structure and adsorption performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the pretreatment of biomass lignocellulose, and more particularly to a one-step pretreatment technology of cow dung lignocellulose and the influence of the change of lignocellulose aggregation structure on the preparation of porous carbon materials and the adsorption performance. BACKGROUND

[0002] Hydrogen energy, as a clean and efficient secondary energy, is a key component of the future low-carbon energy system. However, the large-scale commercial application of hydrogen energy is severely limited by economic and efficient hydrogen storage technology. Among the three main hydrogen storage methods of high-pressure gas, low-temperature liquid and material-based solid, solid-state hydrogen storage is considered as the most promising direction due to its high safety and high volumetric hydrogen storage density. The core of solid-state hydrogen storage materials is to fix hydrogen in the material through physical adsorption and chemical hydrogenation. Among them, porous carbon materials have attracted widespread attention in the field of physical hydrogen storage due to their large specific surface area, adjustable pore structure, good chemical stability and fast hydrogen absorption and desorption kinetics.

[0003] The production of global agricultural waste is increasing, and the accumulation problem is becoming increasingly serious, leading to resource waste and environmental pollution. Research on the full use of agricultural waste resources is increasing, and the high-value utilization of these large biomass resources is of great significance for sustainable development. Therefore, the development of low-cost porous carbon materials using renewable biomass as a precursor has become a major research direction. Agricultural waste mainly includes plant-derived waste and animal-derived waste such as livestock and poultry manure. Livestock and poultry manure, especially the large amount of cow dung produced by large-scale livestock farming, poses a greater challenge to its disposal and resource utilization. Improper disposal of cow dung not only causes serious environmental pollution but also limits the sustainable development of the livestock industry. Studies have shown that the resource utilization of cow dung is mainly concentrated in traditional ways such as anaerobic fermentation to produce biogas and aerobic composting to produce organic fertilizer, with low added value. Converting cow dung into porous carbon materials is an effective solution, but this process also faces many challenges. Direct pyrolysis of cow dung is difficult to obtain porous carbon materials with uniform structure and stable performance, and the hydrogen storage performance of the prepared carbon materials is often poor.

[0004] The aggregation structure of lignocellulose in biomass directly determines the porosity, micropore specific surface area and hydrogen storage performance of the derived carbon materials. Therefore, pretreatment of the aggregation structure of lignocellulose is a technical problem that needs to be solved in optimizing the structure of carbon materials. SUMMARY

[0005] The technical problem to be solved by the present application is to change the aggregation structure of lignocellulose in cow dung by hydrothermal pretreatment, thereby improving the porosity, micropore specific surface area and hydrogen storage performance of the porous carbon material, and preparing a cow dung-based porous carbon material.

[0006] One of the purposes of the present application is to provide a method for changing the aggregation structure of lignocellulose in cow dung.

[0007] Another purpose of the present application is to provide a method for preparing porous carbon material by one-step treatment of cow dung.

[0008] Still another purpose of the present application is to provide the application of hydrothermal pretreatment of cow dung and preparation of porous carbon material in H2 adsorption.

[0009] The purposes of the present application are achieved by the following technical solutions:

[0010] A method for hydrothermal pretreatment of cow dung and preparation of porous carbon material, wherein the raw material is cow dung, and the aggregation structure of the cow dung is changed by hydrothermal pretreatment.

[0011] According to the present application, the one-step hydrothermal pretreatment principle is to promote the conversion of polysaccharide polymers into small molecular compounds through hydrolysis reaction, so as to realize the depolymerization of hemicellulose and cellulose, and the generation of pseudo-lignin. Further, the aggregation structure of lignocellulose in cow dung is changed.

[0012] A method for preparing a hydrothermal pretreatment of cow dung-based hydrogen storage material, comprising the following processing steps:

[0013] 1) Hydrothermal pretreatment: 2g of dried, crushed, and sieved cow dung and 60ml of deionized water are placed in a hydrothermal reactor, and after pretreatment at different hydrothermal temperatures and hydrothermal times, the sample is dried. The hydrothermal temperature is 140-200 o C, and the hydrothermal time is 12-48h.

[0014] 2) Activation: the dried pretreated sample in step 1) is ground into powder, then mixed with an activator according to a certain proportion, stirred, and dried. The activator is potassium hydroxide, the mass ratio of the pretreated sample powder to the activator is 1:1, and the stirring time is 1h.

[0015] 3) Carbonization: the dried solid in step 2) is ground into powder, then calcined at high temperature under nitrogen atmosphere, washed to neutral after cooling to room temperature, and dried and ground into powder to obtain a cow dung-based porous carbon material. The calcination temperature of the dried solid powder under nitrogen atmosphere is 800 o C, and the time is 1h; the drying temperature is 80 o C, and the time is 24h.

[0016] The prepared hydrothermal pretreatment of cow dung and the prepared porous carbon material will be applied in H2 adsorption.

[0017] The present application has the following beneficial effects:

[0018] The aggregated structure of lignocellulose is mainly a three-dimensional network structure formed by cellulose, hemicellulose and lignin through hydrogen bonding, van der Waals forces and other interactions. This structure directly affects the pyrolysis behavior, pore formation and the physical and chemical properties of the final material such as micropore specific surface area, pore size distribution and hydrogen storage performance during carbonization. Pretreatment is the first and essential step in the conversion of lignocellulosic biomass into carbon materials. The purpose of pretreatment is to change the aggregated structure of the biomass precursor. During hydrothermal pretreatment, cellulose and hemicellulose are hydrolyzed in the hydrothermal reactor to produce acidic substances and small molecule compounds, and their oxygen-containing functional groups will produce initial microporous structures in the form of gas. Among them, the produced acidic substances will further promote the decomposition of cellulose and hemicellulose, and there are furfural and 5-hydroxymethyl furfural in small molecule compounds, which can further form pseudo-lignin through hydroxyaldehyde condensation reaction. This is why the content of cellulose and hemicellulose decreases and the content of lignin increases after hydrothermal pretreatment. In addition, compared with traditional preparation of porous carbon materials, hydrothermal pretreatment not only changes the aggregated structure of lignocellulose and produces initial microporous structures to provide initial pores for the subsequent carbonization step, but also simplifies the preparation steps of porous carbon materials. Because the traditional preparation of porous carbon materials needs a pre-carbonization step after pretreatment, the purpose of pre-carbonization is to prevent the collapse of pores caused by high-temperature rapid decomposition, and to provide initial pores for the subsequent activation step, while hydrothermal pretreatment can also play the same role.

[0019] The use of hydrothermal pretreatment of cow dung to prepare porous carbon materials for hydrogen storage not only realizes the resource utilization of agricultural waste cow dung, but also converts cow dung into solid hydrogen storage materials. It realizes the leap from waste management to high-value resource creation. The application of this technology expands the resource utilization way of biomass waste, and has important economic and social value. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The mass percentage of cellulose, hemicellulose and lignin in the intermediate product obtained in step 3 of the example preparation and step 2 of the comparative example preparation is plotted.

[0021] Figure 2 The XRD pattern and crystallinity of the intermediate product obtained in step 3 of the example preparation and step 2 of the comparative example preparation are plotted.

[0022] Figure 3 The TG and DTG curves of the intermediate product obtained in step 3 of the example preparation and step 2 of the comparative example preparation are plotted.

[0023] Figure 4 The SEM pattern of the intermediate product obtained in step 3 of the example preparation and step 2 of the comparative example preparation is plotted.

[0024] Figure 5XRD and Raman patterns of samples were prepared for examples and comparative examples.

[0025] Figure 6 ID / IG value patterns of samples were prepared for examples and comparative examples.

[0026] Figure 7 SEM patterns of samples were prepared for examples and comparative examples.

[0027] Figure 8 N2 adsorption-desorption isotherm and pore size distribution patterns of samples were prepared for examples and comparative examples.

[0028] Figure 9 Fourier transform infrared (FTIR) patterns of samples were prepared for examples and comparative examples.

[0029] Figure 10 X-ray electron diffraction (XPS) patterns of samples were prepared for examples and comparative examples.

[0030] Figure 11 CO2 isotherm patterns of samples were prepared for examples. DETAILED DESCRIPTION

[0031] The hydrothermal pretreated cow dung-based hydrogen storage material provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0032] Example 1:

[0033] 1) The cow dung was crushed and washed with deionized water for 5 times, and then dried in an 80 o C oven.

[0034] 2) The dried cow dung was ground for subsequent use.

[0035] 3) The cow dung obtained in step 2) was added into the inner liner of a hydrothermal reactor together with 60 ml of deionized water, and reacted at 140 o C for 12 h, and then dried in an 80 o C oven to obtain a pretreated sample.

[0036] 4) The pretreated sample obtained in step 3) was mixed with KOH at a mass ratio of 1:1, stirred for 1 h, and dried in an 80 o C oven.

[0037] 5) The dried sample obtained in step 4) was placed in a tubular furnace and calcined at 800 o C for 1 h under a nitrogen atmosphere, washed with hydrochloric acid after cooling to room temperature, and then washed with deionized water until neutral, and dried at 80 o C for 24 h to obtain a porous carbon material.

[0038] Example 2:

[0039] 1) After crushing the cow dung, wash it 5 times with deionized water and then place it in an 80°C container. o Dry in an oven at C.

[0040] 2) Grind the dried cow dung for later use.

[0041] 3) Add the cow dung obtained in step 2) and 60 ml of deionized water to the lining of the hydrothermal reactor, and heat at 160°C. o After 12 hours of reaction at C, 80 o The pretreated sample was obtained by drying in an oven at C.

[0042] 4) Mix the pretreated sample obtained in step 3) with KOH at a mass ratio of 1:1 and stir for 1 hour, then heat at 80°C. o Dry in an oven at C.

[0043] 5) Place the dried sample obtained in step 4) in a tubular furnace and heat it at 800°C under a nitrogen atmosphere. o Calcination at C for 1 hour, cooling to room temperature, washing with hydrochloric acid, and finally washing with deionized water until neutral, then 80°C. o Drying at C for 24 hours yields porous carbon material.

[0044] Example 3:

[0045] 1) After crushing the cow dung, wash it 5 times with deionized water and then place it in an 80°C container. o Dry in an oven at C.

[0046] 2) Grind the dried cow dung for later use.

[0047] 3) Add the cow dung obtained in step 2) and 60 ml of deionized water to the lining of the hydrothermal reactor, and heat at 180°C. o After 12 hours of reaction at C, 80 o The pretreated sample was obtained by drying in an oven at C.

[0048] 4) Mix the pretreated sample obtained in step 3) with KOH at a mass ratio of 1:1 and stir for 1 hour, then heat at 80°C. o Dry in an oven at C.

[0049] 5) Place the dried sample obtained in step 4) in a tubular furnace and heat it at 800°C under a nitrogen atmosphere. o Calcination at C for 1 hour, cooling to room temperature, washing with hydrochloric acid, and finally washing with deionized water until neutral, then 80°C. o Drying at C for 24 hours yields porous carbon material.

[0050] Example 4:

[0051] 1) After crushing the cow dung, wash it 5 times with deionized water and then place it in an 80°C container. o Dry in an oven at C.

[0052] 2) Grind the dried cow dung for later use.

[0053] 3) Add the cow dung obtained in step 2) and 60 ml of deionized water to the lining of the hydrothermal reactor, and heat at 200°C. o After 12 hours of reaction at C, 80 o The pretreated sample was obtained by drying in an oven at C.

[0054] 4) Mix the pretreated sample obtained in step 3) with KOH at a mass ratio of 1:1 and stir for 1 hour, then heat at 80°C. o Dry in an oven at C.

[0055] 5) Place the dried sample obtained in step 4) in a tubular furnace and heat it at 800°C under a nitrogen atmosphere. o Calcination at C for 1 hour, cooling to room temperature, washing with hydrochloric acid, and finally washing with deionized water until neutral, then 80°C. o Drying at C for 24 hours yields porous carbon material.

[0056] Example 5:

[0057] 1) After crushing the cow dung, wash it 5 times with deionized water and then place it in an 80°C container. o Dry in an oven at C.

[0058] 2) Grind the dried cow dung for later use.

[0059] 3) Add the cow dung obtained in step 2) and 60 ml of deionized water to the lining of the hydrothermal reactor, and heat at 200°C. o After 48 hours of reaction at C, 80 o The pretreated sample was obtained by drying in an oven at C.

[0060] 4) Mix the pretreated sample obtained in step 3) with KOH at a mass ratio of 1:1 and stir for 1 hour, then heat at 80°C. o Dry in an oven at C.

[0061] 5) Place the dried sample obtained in step 4) in a tubular furnace and heat it at 800°C under a nitrogen atmosphere. o Calcination at C for 1 hour, cooling to room temperature, washing with hydrochloric acid, and finally washing with deionized water until neutral, then 80°C. o Drying at C for 24 hours yields porous carbon material.

[0062] Comparative example:

[0063] 1) After crushing the cow dung, wash it 5 times with deionized water and then place it in an 80°C container. o Dry in an oven at C.

[0064] 2) Grind the dried cow dung for later use.

[0065] 3) Mix the cow dung obtained in step 2) with KOH at a mass ratio of 1:1 and stir for 1 hour at 80°C. o Dry in an oven at C.

[0066] 4) Place the dried sample obtained in step 3) in a tubular furnace and heat it at 800°C under a nitrogen atmosphere. o Calcination at C for 1 hour, cooling to room temperature, washing with hydrochloric acid, and finally washing with deionized water until neutral, then 80°C. o Drying at C for 24 hours yields porous carbon material.

[0067] Structural and performance characterization

[0068] 1. Analysis of the pretreated samples and raw cow dung obtained in steps 1-3 of the embodiment.

[0069] Hydrothermal pretreatment of cow manure has a certain impact on its hemicellulose, cellulose, and lignin, thereby altering the aggregation structure of lignocellulose in cow manure. Figure 1 The graph shows the content changes after pretreatment at different hydrothermal temperatures and times. As the hydrothermal temperature increases, the hemicellulose content in the example gradually decreases. When the hydrothermal temperature reaches 160°C... o C-hemicellulose was almost completely decomposed. When the hydrothermal temperature reached 200°C... o At time C, cellulose in some examples gradually decomposed with increasing hydrothermal time. The lignin content gradually increased with increasing hydrothermal temperature and time (Table 1). This is because hemicellulose and cellulose undergo hydrolysis during hydrothermal pretreatment, generating small molecule compounds such as furfural and 5-hydroxyfurfural. These aldehydes react with the generated small molecule compounds through aldol condensation to form pseudolignin. This indicates that changing the temperature and time of hydrothermal pretreatment can alter the aggregation structure of lignocellulose in cow manure seeds.

[0070] Table 1. Hemicellulose, cellulose, and lignin content of comparative examples and embodiments

[0071]

[0072] XRD of pretreated samples Figure 2 In (a), the crystallinity of cow manure lignocellulose changed significantly due to the degradation of the entire hemicellulose-cellulose array. The pretreatment XRD pattern showed that the crystallinity of cow manure after hydrothermal pretreatment was higher than that of the comparative example. Figure 2 (b) The highest crystallinity in Example 3 reached 43.65%. This indicates that hydrothermal pretreatment altered the lignocellulose aggregation structure in cow dung. To investigate the effect of this change in the lignocellulose aggregation structure on its thermal stability, thermogravimetric analysis was performed on the pretreated samples. Figure 3 a and Figure 3 b represents the TG and DTG curves of the pretreated sample, respectively. The temperature range in the DTG curve is 230-330°C. oC represents the variation in hemicellulose, 330-390. o C represents the change in cellulose, 390-490. o C represents the lignin variation. Between 230-330... o In zone C, hemicellulose gradually decomposes as the hydrothermal temperature increases, reaching almost complete decomposition in Example 2. (330-390) o In section C, as the hydrothermal time increased, most of the cellulose decomposed as in Example 5. (390-490) o In interval C, lignin content gradually increases with increasing hydrothermal temperature and time. This aligns with the changes in hemicellulose, cellulose, and lignin content in the comparative and examples shown in Table 1. Simultaneously, the slope K value in the TG plot reflects the change in material crystallinity. Due to the increase in lignin content, the K value shows an upward trend.

[0073] SEM images after hydrothermal pretreatment Figure 4 As can be seen, after hydrothermal pretreatment, the bundle structure of the examples was damaged to varying degrees compared with the comparative examples, and irregular pores appeared on the surface. With the increase of hydrothermal pretreatment time, the number of pores in the examples increased significantly with the increase of hydrothermal temperature and time. This is because the cellulose and hemicellulose in the lignocellulose structure are mainly connected by hydrogen bonds. Hydrothermal pretreatment disrupts this physical connection, and the bundle structure is also damaged. The bundle structure in Example 5 was particularly significantly damaged. The pores that appeared in this process were mainly due to the vaporization and etching of hydrolysis products during hydrothermal pretreatment. Therefore, hydrothermal pretreatment can regulate the aggregation structure of lignocellulose in cow dung and provide initial channels for subsequent step 4) of the examples.

[0074] 2. Analysis of porous carbon samples obtained in steps 1-5 of the embodiment and comparative examples

[0075] XRD patterns of comparative examples and embodiments are as follows Figure 5 As shown in (a), all samples exhibit broad and weak diffraction peaks at 2θ = 24.5° and 43.5°, corresponding to the (002) and (100) crystal planes of graphite, respectively. These broad and weak diffraction peaks indicate that the crystal structure of the samples is highly disordered. Raman spectra of the comparative examples and embodiments. Figure 5 (b) shows that all samples were at 1350 cm. -1 and 1602 cm -1 Strong peaks are present at each location, corresponding to the D and G peaks of the carbon material, respectively. The degree of disorder of the material can be determined by calculating the ID / IG value in the Raman spectrum. Figure 6The ID / IG plots for the comparative examples and embodiments show that the ID / IG values ​​gradually decrease with increasing hydrothermal pretreatment temperature. Example 3 exhibits the lowest disorder degree of 0.83. This is consistent with the crystallinity results of the XRD analysis of the pretreated samples, further verifying that hydrothermal pretreatment can regulate the aggregation structure of lignocellulose in cow dung by adjusting crystallinity.

[0076] Figure 7 The images show SEM images of the comparative and exemplary cases. As can be seen from the images, the surface structure of the activated comparative and exemplary cases exhibits a sea urchin-like structure. Compared with the pretreated comparative and exemplary cases, more porous structures are formed, and carbon microspheres appear on the surface. This indicates that KOH activation increases the pore structure of the carbon material.

[0077] N2 adsorption-desorption isotherms of the examples and comparative examples ( Figure 8 a) All samples exhibited Type I isotherms. Under low relative pressure (P / P0 < 0.1), the N2 adsorption capacity of all samples increased rapidly. As P / P0 gradually increased, the curves gradually stabilized, indicating that all samples contained abundant micropores. Pore size distribution ( Figure 8 (b) This indicates that the pore size of the material is mainly concentrated in the range of <2 nm. With increasing hydrothermal pretreatment temperature, the decrease in hemicellulose and the increase in lignin in the examples resulted in a first increase and then a decrease in the micropore area of ​​the carbonized samples (Table 2). This may be because the decomposition of hemicellulose leads to an increase in micropore area. However, with increasing hydrothermal temperature and time, the pores generated during hydrothermal pretreatment collapsed during carbonization, even falling below the level of the comparative example. This observation demonstrates that changing the hydrothermal pretreatment temperature and time can regulate the aggregation structure of lignocellulose in cow dung, thereby affecting the micropore area and pore size distribution of the material.

[0078] Table 2 shows the pore structure parameters of the pre-carbonization step in the comparative examples and embodiments.

[0079]

[0080] Through FTIR spectra ( Figure 9 The surface functional groups of the proportions and examples were analyzed. All samples were tested at 3450, 1620, and 1100 cm⁻¹. -1 The peaks on the left and right correspond to the stretching vibrations of -OH / NH, C=C, and CO, respectively. From the sample's full XPS spectrum ( Figure 10 In a), it was observed that all samples exhibited three distinct peaks at 285 eV, 400 eV, and 532 eV, representing the elemental peaks of C, N, and O, respectively. The elemental contents are shown in Table 3. The C1s peak of all samples (…) Figure 10b) It can be deconvolved into three peaks at 284.8, 285.7, and 288.8 eV, corresponding to CC, CO, and OC=O, respectively. The sample's O1s ( Figure 10 c) The spectrum deconvoluted to produce three peaks with binding energies of approximately 530.6, 533.2, 535.1, and 537.1 eV, corresponding to C=O, CO, O=CO, and oxygen in water molecules, respectively. The sample's N1s ( Figure 10 d) The peaks with spectral deconvolution values ​​of 398.8, 400.1, and 401.2 eV correspond to pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, respectively. These oxygen- and nitrogen-containing functional groups provide more active sites, thereby enhancing the adsorption performance of the sample.

[0081] Table 3. Element content of the examples and comparative examples

[0082]

[0083] Figure 11 The H2 adsorption and desorption figures for the examples and comparative examples are shown in the attached figures at 77 K and 1 bar. The adsorption capacities of the materials are as follows: Comparative Example: 1.73 wt.%, Example 1: 1.97 wt.%, Example 2: 2.12 wt.%, Example 3: 2.16 wt.%, Example 4: 2.03 wt.%, Example 5: 2.05 wt.%. The adsorption capacities of all examples are higher than those of the comparative examples, with Example 3 showing the highest adsorption capacity. This is because the crystallinity of the examples first increases and then decreases with increasing hydrothermal pretreatment temperature and time, reaching its maximum value in Example 3. Therefore, hydrothermal pretreatment can adjust the aggregation structure of lignocellulose in cow dung by regulating crystallinity, thereby affecting H2 adsorption performance.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrothermally pretreated cow dung-based hydrogen storage material, which promotes the transformation of polysaccharide polymers into small molecule compounds through hydrolysis, thereby achieving the depolymerization of hemicellulose and cellulose, and the formation of pseudolignin; thus altering the aggregation structure of lignocellulose in cow dung; characterized in that, Includes the following steps: 1) Hydrothermal pretreatment: The dried, crushed, and sieved cow manure is pretreated under different hydrothermal temperatures and times before drying. 2) Activation: Grind the dried pretreated sample from step 1) into powder, mix it with the activator in a certain proportion, and then dry the stirred sample. 3) Carbonization: The dried solid from step 2) is ground into powder and then calcined at high temperature under a nitrogen atmosphere. After cooling to room temperature, it is washed until neutral, dried and ground into powder to obtain cow dung-based porous carbon material.

2. The preparation method of the hydrothermally pretreated cow dung-based hydrogen storage material according to claim 1, characterized in that: In step 1), the hydrothermal temperature is characterized by being 140~200°C. o C, the hydrothermal time is 12-48h.

3. The preparation method of the hydrothermally pretreated cow dung-based hydrogen storage material according to claim 1, characterized in that: In step 2), the activator is potassium hydroxide, and the ratio of the pretreated sample powder to the activator is 1:

1.

4. The preparation method of the hydrothermally pretreated cow dung-based hydrogen storage material according to claim 1, characterized in that: In step 3), the characteristic feature is that the calcination temperature of the dried solid powder under a nitrogen atmosphere is 800°C. o C, the time is 1 hour.

5. The method for preparing hydrothermally pretreated cow dung-based hydrogen storage material according to any one of claims 1-4, characterized in that: Hydrothermal pretreated cow dung-based porous carbon material was prepared.

6. The method for preparing hydrothermally pretreated cow dung-based hydrogen storage material according to any one of claims 1-4, characterized in that: The prepared hydrothermally pretreated cow dung-based porous carbon material is used for H2 adsorption.

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