Hydrogen storage biochar as well as preparation method and application thereof

Abstract

The invention discloses hydrogen storage biochar and a preparation method and application thereof.The preparation method of the hydrogen storage biochar comprises the steps that a biomass precursor is taken and subjected to air carbonization, and an air carbonization precursor is obtained; uniformly mixing the air carbonization precursor and KOH according to a ratio, raising the temperature in a nitrogen atmosphere, and naturally cooling to room temperature; dispersing the obtained product in deionized water, and adding a nitrogen-calcium doping agent; adding the obtained mixed solution into a hydrothermal reaction kettle for reaction, and cleaning and drying a product to obtain the hydrogen storage biochar. The activation resistance of the biomass to KOH is improved through the first-step air atmosphere pre-carbonization process, meanwhile, the nitrogen doping process is optimized, anchor point N elements and Ca elements are loaded through a hydrothermal method, an N doping agent is used as an anchor point, Ca loading is promoted, the reaction condition is mild, the structure of the raw material is not damaged, and the hydrogen storage performance of the biochar is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biochar preparation, and particularly relates to a hydrogen storage biochar as well as a preparation method and application thereof. BACKGROUND

[0002] Hydrogen is the cleanest fuel, with a mass energy density of 33 kW / kg, which is three times that of petroleum. The utilization of hydrogen energy is an important strategy to cope with the depletion of fossil energy and global environmental problems. Among them, the continuous and cheap supply of hydrogen energy is a key problem, which is not only related to the production of hydrogen energy, but also closely related to the transportation and storage links. So far, extensive research has been made on the production of hydrogen, and industrial application has been achieved on a considerable scale, but the transportation and storage technology of hydrogen still needs to be gradually established.

[0003] The existing hydrogen storage technologies mainly include high-pressure liquefied hydrogen storage, chemical conversion hydrogen storage and solid material hydrogen storage. Among them, the solid hydrogen storage material has excellent cycle use performance, low cost and safety and reliability, and is one of the technical routes that can be hopefully realized in large-scale and industrialized application.

[0004] The solid hydrogen storage material needs to have excellent cycle adsorption and desorption performance, and the mass also needs to be light enough to reduce transportation cost. Among the solid hydrogen storage materials, carbon-based materials are very good adsorbents, including fullerenes, carbon nanotubes, carbon fibers, graphene and activated carbon. Among them, carbon nanotubes and activated carbon with rich pore structure have the application potential of physical adsorption hydrogen storage. However, at low temperature and normal pressure, the hydrogen storage performance of carbon-based hydrogen storage materials is generally lower than 3 wt.%, and the performance target of solid hydrogen storage materials proposed by the International Energy Agency is 5.5 wt.%. It can be seen that the current carbon-based hydrogen storage material still has a long way to go to reach this target, and it is urgent to explore the modification process and develop cheap, reliable and high-quality hydrogen storage density activated carbon. SUMMARY

[0005] In order to solve at least one of the above problems, the application provides a hydrogen storage biochar as well as a preparation method and application thereof.

[0006] In order to achieve the above purpose, the application adopts the following technical means: the first aspect of the application provides a preparation method of a hydrogen storage biochar, and the preparation method comprises the following steps: S1, taking a biomass precursor, air carbonizing the biomass precursor to obtain an air carbonized precursor; S2, uniformly mixing the air carbonized precursor with an activating agent KOH at a mass ratio of 1: (3-6), heating to 700-800 DEG C under a nitrogen atmosphere, keeping for 50-60 min, and naturally cooling to room temperature; S3, dispersing the product obtained in S2 in deionized water, and adding a nitrogen-calcium dopant; S4, adding the mixed solution obtained in S3 into a hydrothermal reactor, and reacting at 160-180 DEG C for 20-24 h, and then washing and drying the product to obtain the hydrogen storage biochar.

[0007] In some embodiments of the present application, in step S2, the mass ratio of the air carbonized precursor to the activating agent KOH is 1:6.

[0008] In some embodiments of the present application, in step S3, the amount of the nitrogen and calcium dopant added is 1:(30-60) in mass ratio of the product to the nitrogen and calcium dopant.

[0009] In some embodiments of the present application, in step S3, the nitrogen and calcium dopant is urea and calcium chloride, and the urea is added in a mass ratio of 1:45, and the calcium chloride is added in a mass ratio of 1:(5-10).

[0010] In some embodiments of the present application, in step S1, the method for air carbonizing the biomass precursor is as follows: the precursor is heated to 350-400 DEG C in a nitrogen atmosphere in a muffle furnace for 15-20 min, and then the atmosphere in the muffle furnace is switched to air, and the temperature is maintained at 350-400 DEG C for 30-40 min to obtain the air carbonized precursor.

[0011] In some embodiments of the present application, in step S1, the heating rate is 2-3 DEG C / min.

[0012] In some embodiments of the present application, in step S3, the heating rate is 8-10 DEG C / min.

[0013] The second aspect of the present application provides a hydrogen storage biochar prepared by the method of the first aspect.

[0014] The third aspect of the present application provides the use of the hydrogen storage biochar of the second aspect in adsorbing and storing hydrogen at low temperature and normal pressure.

[0015] In some embodiments of the present application, the adsorbing and storing hydrogen is carried out at 77 K and 1 atm.

[0016] Advantages of the present application Compared with the prior art, the present application has the following advantages: The present application uses air atmosphere pre-carbonization, and through the first step of carbonization process, the activating ability of the biomass to KOH is improved, and at the same time, the nitrogen doping process is optimized, the anchor N element and Ca element are loaded by using the hydrothermal method, the N dopant is used as an anchor point to promote the loading of Ca, the reaction condition is mild, and the structure of the raw material is not damaged, and the hydrogen storage performance of the biochar is significantly improved.

[0017] The biomass precursor used in the application is often waste, has wide sources and low cost; the preparation method adopted in the application is simple and efficient, and is suitable for scaling up to industrial scale preparation; the biochar prepared has a mass hydrogen storage density of 3.24wt.% under the condition of 77k, 1atm, and has advantages in application. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A comparison chart of mass hydrogen storage density results of biochar obtained from Example 1 to Example 4 is shown; Figure 2 A comparison chart of mass hydrogen storage density results of biochar obtained from Example 3, Example 5 and Example 6 is shown; Figure 3 A comparison chart of mass hydrogen storage density results of biochar obtained from Example 7 to Example 10 is shown; Figure 4 A comparison chart of mass hydrogen storage density results of biochar obtained from Example 7, Example 11 and Example 12 is shown; Figure 5 A comparison chart of mass hydrogen storage density results of biochar obtained from Example 13 to Example 15 is shown; Figure 6 A comparison chart of mass hydrogen storage density results of biochar obtained from Comparative Example 1 and Comparative Example 2 is shown; Figure 7 A chart of mass hydrogen storage density results of biochar obtained from Comparative Example 3 is shown; Figure 8 A chart of mass hydrogen storage density results of biochar obtained from Comparative Example 4 is shown; Figure 9 A SEM chart of biochar obtained from Example 7 under a scanning electron microscope is shown; Figure 10 A SEM chart of biochar obtained from Example 8 under a scanning electron microscope is shown; Figure 11 A SEM chart of biochar obtained from Example 9 under a scanning electron microscope is shown; Figure 12 A SEM chart of biochar obtained from Example 10 under a scanning electron microscope is shown; Figure 13 An EDS chart of biochar obtained from Example 8 under a scanning electron microscope is shown; Figure 14 An EDS chart of biochar obtained from Example 10 under a scanning electron microscope is shown. DETAILED DESCRIPTION

[0019] The following examples are put forth so as to demonstrate preferred embodiments of the application. Those skilled in the art will recognize that the examples disclosed herein represent techniques that the inventors have found to function well in the practice of the application, and thus can be considered to be preferred modes for its practice. However, those skilled in the art will further recognize, in light of the teachings herein, that many changes can be made to the particular embodiments disclosed in this specification without departing from the spirit and scope of the application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, and the materials referred to in this disclosure are described in terms of their capability to function in the application, together with like materials referred to herein. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the application described herein. Such equivalents are considered to be within the scope of the application.

[0021] The technical solutions of the present application will be further described in detail below in conjunction with the specific embodiments.

[0022] Example 1 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain amount of corn cob powder is weighed and placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air carbonized precursor; an activating agent K2CO3 is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and then raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and then naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0023] Example 2 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain amount of corn cob powder is weighed and placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air carbonized precursor; an activating agent K2CO3 is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and then raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and then naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0024] Example 3 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; an activating agent KOH is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0025] Example 4 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; an activating agent KOH is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0026] Example 5 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; an activating agent KOH is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0027] Example 6 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400°C at a rate of 3°C / min under a nitrogen atmosphere, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; an activating agent KOH is added in a mass ratio of 1:3, and the mixture is ground and mixed uniformly, and raised to 800°C at a rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min, and naturally cooled to room temperature; the product is washed with deionized water, and dried to obtain a hydrogen storage biochar.

[0028] Example 7 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400℃ at a rate of 3℃ / min under a nitrogen atmosphere, and maintained for 15min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400℃ for 30min to obtain an air carbonized precursor; an activating agent KOH is added in a mass ratio of 1:6, and the mixture is ground and mixed uniformly, and then raised to 800℃ at a rate of 10℃ / min under a nitrogen atmosphere, and maintained for 60min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, and a dopant urea is added in a mass ratio of 1:30, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180℃ for 24h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0029] Example 8 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400℃ at a rate of 3℃ / min under a nitrogen atmosphere, and maintained for 15min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400℃ for 30min to obtain an air carbonized precursor; an activating agent KOH is added in a mass ratio of 1:6, and the mixture is ground and mixed uniformly, and then raised to 800℃ at a rate of 10℃ / min under a nitrogen atmosphere, and maintained for 60min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, and a dopant urea is added in a mass ratio of 1:30, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180℃ for 24h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0030] Example 9 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and a muffle furnace is used to raise the temperature of the precursor to 400℃ at a rate of 3℃ / min under a nitrogen atmosphere, and maintained for 15min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400℃ for 30min to obtain an air carbonized precursor; an activating agent KOH is added in a mass ratio of 1:6, and the mixture is ground and mixed uniformly, and then raised to 800℃ at a rate of 10℃ / min under a nitrogen atmosphere, and maintained for 60min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, and a dopant urea is added in a mass ratio of 1:30, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180℃ for 24h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0031] Example 10 A preparation method of hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is weighed and placed in a crucible, a muffle furnace is used to raise the temperature of the precursor to 400 DEG C at a temperature increasing rate of 3 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 15 min; the atmosphere of the muffle furnace is switched to air, the temperature is kept at 400 DEG C for 30 min, and an air carbonized precursor is obtained; an activating agent KOH is added in a mass ratio of 1:6, grinding and mixing are uniformly carried out, the temperature is raised to 800 DEG C at a temperature increasing rate of 10 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 60 min, and then the product is naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, a dopant potassium metaborate is added in a mass ratio of 1:30, and calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added into a hydrothermal reaction kettle, and the product is washed and dried after reaction at 180 DEG C for 24 h, so as to obtain hydrogen storage biochar.

[0032] Example 11 A preparation method of hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is weighed and placed in a crucible, a muffle furnace is used to raise the temperature of the precursor to 400 DEG C at a temperature increasing rate of 3 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 15 min; the atmosphere of the muffle furnace is switched to air, the temperature is kept at 400 DEG C for 30 min, and an air carbonized precursor is obtained; an activating agent KOH is added in a mass ratio of 1:6, grinding and mixing are uniformly carried out, the temperature is raised to 800 DEG C at a temperature increasing rate of 10 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 60 min, and then the product is naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, a dopant potassium metaborate is added in a mass ratio of 1:30, and calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added into a hydrothermal reaction kettle, and the product is washed and dried after reaction at 180 DEG C for 24 h, so as to obtain hydrogen storage biochar.

[0033] Example 12 A preparation method of hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is weighed and placed in a crucible, a muffle furnace is used to raise the temperature of the precursor to 400 DEG C at a temperature increasing rate of 3 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 15 min; the atmosphere of the muffle furnace is switched to air, the temperature is kept at 400 DEG C for 30 min, and an air carbonized precursor is obtained; an activating agent KOH is added in a mass ratio of 1:6, grinding and mixing are uniformly carried out, the temperature is raised to 800 DEG C at a temperature increasing rate of 10 DEG C / min under a nitrogen atmosphere, and the temperature is kept for 60 min, and then the product is naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, a dopant potassium metaborate is added in a mass ratio of 1:30, and calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added into a hydrothermal reaction kettle, and the product is washed and dried after reaction at 180 DEG C for 24 h, so as to obtain hydrogen storage biochar.

[0034] Example 13 A preparation method of hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and the precursor is heated to 400°C at a heating rate of 3°C / min under a nitrogen atmosphere using a muffle furnace, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; the activating agent KOH is added in a mass ratio of 1:6, the mixture is ground and mixed uniformly, and the temperature is raised to 800°C at a heating rate of 800C / min under a nitrogen atmosphere, and maintained for 60 min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, the dopant urea is added in a mass ratio of 1:45, and the calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180°C for 24 h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0035] Example 14 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and the precursor is heated to 400°C at a heating rate of 3°C / min under a nitrogen atmosphere using a muffle furnace, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; the activating agent KOH is added in a mass ratio of 1:6, the mixture is ground and mixed uniformly, and the temperature is raised to 800°C at a heating rate of 800C / min under a nitrogen atmosphere, and maintained for 60 min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, the dopant urea is added in a mass ratio of 1:45, and the calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180°C for 24 h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0036] Example 15 A method for preparing a hydrogen storage biochar, comprising the following steps: A certain mass of corn cob powder is placed in a crucible, and the precursor is heated to 400°C at a heating rate of 3°C / min under a nitrogen atmosphere using a muffle furnace, and maintained for 15 min; the atmosphere of the muffle furnace is switched to air, and the temperature is maintained at 400°C for 30 min to obtain an air-carbonized precursor; the activating agent KOH is added in a mass ratio of 1:6, the mixture is ground and mixed uniformly, and the temperature is raised to 800°C at a heating rate of 800C / min under a nitrogen atmosphere, and maintained for 60 min, and then naturally cooled to room temperature; the product is dispersed in deionized water in a mass ratio of 1:100, the dopant urea is added in a mass ratio of 1:45, and the calcium chloride is added in a mass ratio of 1:5, and the obtained mixed solution is added to a hydrothermal reaction kettle, and reacted at 180°C for 24 h, and the product is washed and dried to obtain a hydrogen storage biochar.

[0037] Comparative Example 1 A certain amount of corn cob powder was placed in a crucible, and an activating agent KOH was added according to a mass ratio of 1:6, and the mixture was ground uniformly. The mixture was raised to 800°C at a temperature increasing rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min. The product was washed with deionized water and dried to obtain the desired biochar.

[0038] Comparative Example 2 A certain amount of corn cob powder was placed in a crucible, and an activating agent KOH was added according to a mass ratio of 1:3, and urea was added according to a mass ratio of 1:1. The mixture was ground uniformly. The mixture was raised to 800°C at a temperature increasing rate of 10°C / min under a nitrogen atmosphere, and maintained for 60 min. The product was washed with deionized water and dried to obtain the desired biochar.

[0039] Comparative Example 3 Commercial activated carbon purchased from Zhejiang Honeycomb Activated Carbon Co., Ltd. was used, which was a powder activated carbon with a specific surface area of 1300 m² / kg.

[0040] Comparative Example 4 Commercial activated carbon purchased from Zhejiang Honeycomb Activated Carbon Co., Ltd. was washed with hydrochloric acid and deionized water to remove its ash content, and was ground and sieved through an 80-mesh sieve after drying. The treated commercial activated carbon was dispersed in deionized water according to a mass ratio of 1:100, and a dopant urea was added according to a mass ratio of 1:45, and calcium chloride was added according to a mass ratio of 1:10. The obtained mixed solution was added to a hydrothermal reaction kettle, and reacted at 180°C for 24 h. The product was washed with deionized water and dried.

[0041] The hydrogen adsorption experiments of the biochars corresponding to Examples 1-15 and Comparative Examples 1-4 above were carried out at 77K 1 Bar, and the mass hydrogen storage densities were measured.

[0042] The mass hydrogen storage densities of the biochars obtained in Examples 1-4 were 0wt%, 1.31wt%, 2.19wt%, and 2.06wt%, respectively. The comparison results are shown in Table 1. Figure 1

[0043] The mass hydrogen storage densities of the biochars obtained in Examples 3, 5, and 6 were 2.19wt%, 2.52wt%, and 1.71wt%, respectively. The comparison results are shown in Table 2. Figure 2

[0044] The mass hydrogen storage densities of the biochars obtained in Examples 7-10 were 2.41wt%, 2.63wt%, 0.90wt%, and 0.86wt%, respectively. The comparison results are shown in Table 3. Figure 3

[0045] ​​​The mass hydrogen storage densities of the biochar obtained in Example 7, Example 11 and Example 12 are 2.41wt%, 2.70wt% and 2.75wt% respectively. The comparison results are shown in Table 1. Figure 4

[0046] The mass hydrogen storage densities of the biochar obtained in Example 13, Example 14 and Example 15 are 2.97wt%, 3.24wt% and 2.44wt% respectively. The comparison results are shown in Table 2. Figure 5

[0047] The mass hydrogen storage densities of the biochar obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are 1.74wt%, 0.92wt%, 1.18wt% and 2.31wt% respectively. The results are shown in Table 3. Figures 6-8

[0048] Meanwhile, the biochar obtained in Example 7, Example 8, Example 9 and Example 10 are observed by scanning electron microscope for surface microstructure, and the SEM images under 200nm and 2μm are shown in Table 4. Figures 9-12

[0049] The biochar in Example 8 and Example 10 are confirmed by EDS for the loading amount of Ca, as shown in Table 5. Figures 13-14

[0050] The results show that: comparing the morphology of Example 7 and Example 9, it can be found that N doping has no obvious effect on the pore structure of biochar, while after B doping, the pore structure of biochar is obviously blocked, and Figure 9 it can be seen that the biochar maintains a porous structure, while in Figure 11 the mesoporous structure is obviously reduced.

[0051] Comparative Example 1 shows a one-step activation method, and the traditional hydrogen storage biochar production method is mainly to activate the biomass precursor by an activator to produce ultramicropores. However, due to the limited activation resistance of the original biomass, KOH is easy to over-activate to etch and collapse the ultramicropores into micropores or mesopores, resulting in performance degradation.

[0052] The method of the present application first uses a pre-carbonization plus KOH activation method, which improves the activation resistance of biomass to KOH through the first carbonization process; and on the basis of traditional ultramicropore adsorption, a method of loading Ca sites to improve hydrogen storage capacity is proposed. However, the direct loading of Ca on activated carbon has very low efficiency, and needs to be fixed by other anchor elements.

[0053] ​​​​​Comparative Example 2 is based on Comparative Example 1, and nitrogen is doped by a one-step activation method, which is a commonly used method for doping nitrogen, and has the advantages of simple operation and high nitrogen doping rate. However, the doping agent will decompose and produce ammonia gas during the activation process, which will destroy the original ultra-micropore structure of the biochar and form mesopores, thereby leading to a decrease in hydrogen storage performance. Therefore, the present method uses a new hydrothermal post-treatment method for doping nitrogen, which has mild conditions and does not damage the structure of the raw material.

[0054] The present method attempts to use two anchor elements, N and B. Figure 13 and Figure 14 It can be seen that both N and B have anchoring effects on Ca, and the anchoring effect of B is stronger. However, B doping seriously blocks the pore structure of biochar, and B has a significant adverse effect on the hydrogen storage capacity of biochar. However, a proper amount of nitrogen element slightly improves the hydrogen storage performance. However, the hydrogen storage performance of single N doping is limited. Although the higher the amount of nitrogen doping, the higher the mass hydrogen storage density, the comprehensive economic consideration is that the preferred amount of nitrogen doping agent is 1:45 by mass. After optimization, the method of simultaneously loading anchor elements N and Ca elements by hydrothermal treatment significantly improves the hydrogen storage performance of biochar.

[0055] Comparative Example 3 and Comparative Example 4 show that the method of hydrothermal post-treatment doping modification also has a modification effect on conventional commercial activated carbon, and the mass hydrogen storage density is doubled before and after modification.

[0056] All the documents mentioned in the present application are incorporated by reference in the present application, as if each document is individually incorporated by reference. In addition, it should be understood that those skilled in the art can make various modifications or improvements to the present application after reading the above teachings of the present application, and these equivalent forms also fall within the scope defined by the present application.

Claims

1. A method for preparing hydrogen-storage biochar, characterized in that, The preparation method includes the following steps: S1. Take biomass precursors and air carbonize them to obtain air-carbonized precursors. S2. Mix the air carbonization precursor and activator KOH at a mass ratio of 1:(3-6) until homogeneous. Heat the mixture to 700-800℃ under a nitrogen atmosphere and hold for 50-60 minutes. Then allow it to cool naturally to room temperature. S3. Disperse the product obtained in S2 in deionized water and add nitrogen-calcium dopant; S4. Add the mixed solution obtained in S3 to a hydrothermal reactor and react at 160-180℃ for 20-24 hours. Wash and dry the product to obtain hydrogen storage biochar.

2. The method for preparing hydrogen-storage biochar according to claim 1, characterized in that, In step S2, the mass ratio of the air carbonization precursor to the activator KOH is 1:

6.

3. The method for preparing hydrogen-storage biochar according to claim 3, characterized in that, In step S3, the amount of nitrogen-calcium dopant added is the mass ratio of product to nitrogen-calcium dopant 1:(30-60).

4. The method for preparing hydrogen-storage biochar according to claim 3, characterized in that, In step S3, the nitrogen-calcium dopant is urea and calcium chloride. Urea is added at a mass ratio of 1:45, and calcium chloride is added at a mass ratio of 1:(5-10).

5. The method for preparing hydrogen-storage biochar according to claim 1, characterized in that, In step S1, the method for air carbonization of biomass precursor is as follows: in a muffle furnace, the precursor is heated to 350-400℃ under a nitrogen atmosphere and held for 15-20 minutes; then the atmosphere of the muffle furnace is switched to air and the temperature is held at 350-400℃ for 30-40 minutes to obtain the air-carbonized precursor.

6. The method for preparing hydrogen-storage biochar according to claim 1, characterized in that, In step S1, the heating rate is 2-3℃ / min.

7. The method for preparing hydrogen-storage biochar according to claim 1, characterized in that, In step S3, the heating rate is 8-10℃ / min.

8. A hydrogen storage biochar, characterized in that: It is prepared by the method described in any one of claims 1-7.

9. The application of the hydrogen storage biochar according to claim 8 in the adsorption and storage of hydrogen at low temperature and normal pressure.

10. The application according to claim 9, characterized in that: The conditions for hydrogen adsorption storage are 77 K and 1 atm.

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