Preparation method of three-dimensional porous carbon loaded transition metal monatomic scandium solid hydrogen storage material

Abstract

A preparation method of a three-dimensional porous carbon loaded transition metal monatomic scandium solid hydrogen storage material comprises the following steps: dispersing porous carbon powder in deionized water to obtain a porous carbon material dispersion liquid; the preparation method comprises the following steps: dissolving ScCl3.H2O in deionized water to obtain a scandium chloride dispersion liquid; mixing and uniformly stirring the porous carbon material dispersion liquid and the scandium chloride dispersion liquid to obtain a porous carbon material-scandium chloride precursor dispersion liquid, standing, then carrying out centrifugal treatment, reserving a filter cake to obtain a porous carbon material-scandium chloride precursor material, drying in a vacuum drying oven, then putting in a tubular furnace, and carrying out sintering in an argon atmosphere to obtain the porous carbon material-scandium chloride composite material. And heating to 200 DEG C, calcining for 2 hours, and cooling to room temperature to obtain the three-dimensional porous carbon loaded transition metal monatomic scandium solid hydrogen storage material. The method has the advantages of simple process, mild reaction conditions, capability of realizing loading without high-temperature pyrolysis, good dispersity and stable material performance, and has high energy density and good hydrogen storage reversibility when being used as a solid hydrogen storage material.

Description

Technical Field

[0001] The present invention relates to a preparation method of a three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material, which is mainly used for solid-state hydrogen storage materials. Background Art

[0002] With the transformation of the global energy structure and the increasingly serious problem of climate change, renewable energy and the hydrogen energy economy have gradually become the focus of global energy development. As a clean and efficient energy carrier, hydrogen energy has great application potential and market value. However, the wide application of hydrogen energy is limited by its efficient and safe storage and transportation technologies.

[0003] In hydrogen energy storage technologies, solid-state hydrogen storage technology has become a research hotspot due to its high safety, large volumetric density, and easy transportation. Currently, commonly used solid-state hydrogen storage materials such as metal hydrides, inorganic porous materials, and carbon-based materials still face many challenges in terms of hydrogen storage capacity, hydrogen absorption and desorption kinetics, and cycle stability.

[0004] Three-dimensional porous carbon materials have shown great application potential in the fields of energy storage and conversion due to their unique pore structure, high specific surface area, and excellent electrochemical stability. Their porous structure not only provides abundant active sites and channels for the rapid adsorption and diffusion of hydrogen, but also effectively improves the hydrogen storage efficiency and kinetic performance. However, the adsorption of hydrogen molecules by porous carbon materials is mainly achieved through physical adsorption, and its adsorption force is weak, which limits its performance as an efficient hydrogen storage material.

[0005] In order to further improve the hydrogen storage performance of porous carbon materials, researchers have tried to disperse transition metal single atoms on porous carbon to enhance the adsorption ability of hydrogen molecules through chemical adsorption. Among them, transition metal scandium has become an ideal candidate material due to its unique electronic structure and chemical properties. However, current synthesis methods for porous carbon-supported transition metal atoms, such as direct pyrolysis, have problems of excessive crystallization and structural damage of the material caused by high-temperature pyrolysis, making the performance of the material unstable. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of a three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material, which has a simple process, mild reaction conditions, can achieve the loading of transition metal scandium on three-dimensional porous carbon without high-temperature pyrolysis, has good dispersion, and the obtained material has stable performance and high energy density and good hydrogen storage reversibility for solid-state hydrogen storage materials.

[0007] The technical solution of the present invention is as follows:

[0008] A preparation method of a three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material, the specific steps are as follows:

[0009] S1: Prepare a dispersion of porous carbon material

[0010] Disperse the porous carbon powder in deionized water according to the mass ratio of porous carbon powder to deionized water (0.8 - 1.5):500 to obtain a dispersion of porous carbon material;

[0011] S2: Prepare a dispersion of scandium chloride

[0012] Dissolve ScCl3·H2O in deionized water according to the mass ratio of ScCl3·H2O to deionized water (0.6 - 1):50 to obtain a dispersion of scandium chloride;

[0013] S3: Prepare a dispersion of porous carbon material - scandium chloride (ScCl3·H2O) precursor

[0014] Mix the dispersion of porous carbon material and the dispersion of scandium chloride according to the volume ratio of 10:1 and stir evenly to obtain a dispersion of porous carbon material - scandium chloride precursor;

[0015] S4: Centrifugation treatment

[0016] Let the dispersion of porous carbon material - scandium chloride precursor stand still, then perform centrifugation treatment, retain the filter cake to obtain a porous carbon material - scandium chloride precursor material;

[0017] S5: Prepare a three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material

[0018] Place the porous carbon material - scandium chloride precursor material in a vacuum oven to dry, then place it in a tube furnace, under an argon atmosphere, heat up to 200°C and calcine for 2 h, cool down to room temperature to obtain a three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material.

[0019] Furthermore, when dispersing the porous carbon powder in deionized water in step S1, first add the porous carbon material to the deionized water while stirring with a magnetic stirrer, then under ultrasonic conditions, perform ultrasonic treatment for 15 min, and then stir with a magnetic stirrer.

[0020] As a further preference, when stirring in step S1, the stirring speed is 500 r / min, the first stirring time is 30 min, and the second stirring time is 60 - 75 min.

[0021] Furthermore, when dispersing ScCl3·H2O in deionized water in step S2, first add ScCl3·H2O to the deionized water while stirring with a magnetic stirrer for the first time, then under ultrasonic conditions, perform ultrasonic treatment for 10 min, and then stir with a magnetic stirrer for the second time.

[0022] As a further preference, during the stirring in step S2, the stirring speed is 500 r / min, the first stirring time is 30 min, and the second stirring time is 30 - 50 min.

[0023] Further, during the stirring in step S3, use a magnetic stirrer to stir at a rotation speed of 50 r / min for 30 min, and then stir at a rotation speed of 200 r / min in a water bath at 50 °C for 8 hours.

[0024] Further, during the centrifugation process, the centrifugation speed is 12,000 r / min and the centrifugation time is 10 min.

[0025] Further, during the drying process, the drying temperature is 100 °C and the drying time is 10 h.

[0026] Further, the specific surface area of the porous carbon is 2000 - 2100 m 2 g -1 .

[0027] Further, the heating rate of the tubular furnace is 10 °C / min.

[0028] Advantages of the present invention:

[0029] The present invention uses ScCl3·H2O as a precursor and porous carbon as the main material. Through a unique low-temperature pyrolysis process, the process is simple and the reaction conditions are mild. A solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon is obtained. In addition to inheriting the advantages of porous carbon itself, it also combines the supported scandium atoms, resulting in good solid hydrogen storage capacity. The obtained solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon has a large specific surface area, up to 2895 m 2 g -1 , providing a large number of adsorption sites for hydrogen storage; the scandium particles have good dispersion on the three-dimensional porous carbon, which is beneficial to improving its adsorption activity. The solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon has significantly improved hydrogen absorption and desorption amounts and nitrogen adsorption and desorption amounts at the liquid nitrogen temperature of 77 K, and the material performance is stable. It has a high energy density and good hydrogen storage reversibility for use as a solid hydrogen storage material. Description of the Drawings

[0030] Figure 1 is the nitrogen adsorption - desorption isotherm curve of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1);

[0031] Figure 2 is the nitrogen adsorption - desorption isotherm curve of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon of the present invention (corresponding to Example 1);

[0032] Figure 3It is the pore size distribution diagram of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1);

[0033] Figure 4 It is the pore size distribution diagram of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1);

[0034] Figure 5 It is the X-ray diffraction pattern of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1);

[0035] Figure 6 It is the X-ray diffraction pattern of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1);

[0036] Figure 7 It is the hydrogen adsorption-desorption isotherm curve diagram of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1) at nitrogen temperature;

[0037] Figure 8 It is the hydrogen adsorption-desorption isotherm curve diagram of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127 of the present invention (corresponding to Comparative Example 2) at liquid nitrogen temperature;

[0038] Figure 9 It is the hydrogen adsorption-desorption isotherm curve diagram of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1) at liquid nitrogen temperature;

[0039] Figure 10 It is the adsorption rate time-pressure curve diagram of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1);

[0040] Figure 11 It is the adsorption rate time-pressure curve diagram of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127 of the present invention (corresponding to Comparative Example 2);

[0041] Figure 12 It is the adsorption rate time-pressure curve diagram of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1);

[0042] Figure 13 It is the scanning electron microscope images of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1) at different scales (a. 5μm; b. 1μm);

[0043] Figure 14 It is the scanning electron microscope images of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1) at different scales (a. 5μm; b. 1μm);

[0044] Figure 15 are high-resolution photos of the porous carbon powder obtained by low-temperature calcination treatment of the present invention (corresponding to Comparative Example 1) at different scales (a. 50 nm; b. 10 nm);

[0045] Figure 16 are high-resolution photos of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1) at different scales (a. 50 nm; b. 10 nm);

[0046] Figure 17 are aberration-corrected images of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1) at different scales (a. 5 nm; b. 2 nm);

[0047] Figure 18 is the X-ray photoelectron spectroscopy full spectrum and the corresponding element proportion map of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1) (Cl: 0.38 at%; C: 90.13 at%; Sc: 0.51 at%; O: 8.98 at%);

[0048] Figure 19 is the scanning electron microscopy image of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1);

[0049] Figure 20 is the corresponding element distribution map of the energy spectrum analysis of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material of the present invention (corresponding to Example 1). Detailed implementation manners

[0050] The porous carbon powders used in Examples 1 to 3, Comparative Example 1 and Comparative Example 2 of the present invention are the same batch of porous carbon.

[0051] Example 1

[0052] S1: Prepare a dispersion of porous carbon material

[0053] Add 500 mL of deionized water to a beaker, and then add 1 g of porous carbon powder (specific surface area 2000 - 2100 m 2 g -1 ), while adding the porous carbon material, stir with a magnetic stirrer at a speed of 500 r / min for 30 minutes, then perform ultrasonic treatment for 15 minutes, and then stir with a magnetic stirrer at a speed of 500 r / min for 60 minutes to obtain a dispersion of porous carbon material;

[0054] S2: Prepare a dispersion of scandium chloride

[0055] Add 50 mL of deionized water to a beaker, and then add 800 mg of solid powder of ScCl3·H2O. While adding the solid powder of ScCl3·H2O, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, and heat in a water bath at 40 °C. Then, perform ultrasonic treatment for 10 minutes, and use the magnetic stirrer to stir again at 500 r / min for 30 minutes to obtain a scandium chloride dispersion;

[0056] S3: Prepare a porous carbon material - scandium chloride precursor dispersion

[0057] Mix the porous carbon material dispersion and the scandium chloride dispersion in a volume ratio of 1:1 and stir with a magnetic stirrer at a speed of 50 r / min for 30 min. Then, increase the stirring speed and stir at a speed of 200 r / min in a water bath at 50 °C for 8 hours to obtain a porous carbon material - scandium chloride precursor dispersion;

[0058] S4: Centrifugation treatment

[0059] Let the porous carbon material - scandium chloride precursor dispersion stand at room temperature for 6 hours to fully react and precipitate. Then, centrifuge with a centrifuge at a centrifugation speed of 12000 r / min for 10 minutes, pour off the supernatant, and retain the black precipitate of the porous carbon material - scandium chloride precursor material at the bottom;

[0060] S5: Prepare a three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material

[0061] Vacuum - dry the porous carbon material - scandium chloride precursor material at 100 °C for 10 hours, then place it in a tubular furnace. Under an argon atmosphere, heat it to 200 °C at a rate of 10 °C / min and calcine at 200 °C for 2 hours, and then cool it to room temperature to obtain a three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material.

[0062] The nitrogen adsorption - desorption isotherm curve of the three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material in Example 1 is as Figure 2 shown. It can be seen from Figure 2 that the adsorption - desorption capacity of this material is 920 cm 3 g -1 , significantly exceeding the adsorption capacity of porous carbon. At the same time, the three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material has a large specific surface area, up to 2895 m 2 g -1 . The pore distribution and X - ray diffraction pattern of the three - dimensional porous carbon - supported transition metal single - atom scandium solid hydrogen storage material in Example 1 are as Figure 4 , Figure 6 shown. It can be seen from Figure 4 , Figure 6It can be seen that the pore size of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material obtained in this example is smaller than that of the porous carbon powder obtained by low-temperature calcination treatment in Comparative Example 1, indicating that single-atom scandium fills the pores of the porous carbon, and the peaks of both the porous carbon and scandium atoms appear in the figure, and there are no other impurity peaks, indicating that the purity of this material is high.

[0063] The hydrogen adsorption-desorption isotherm curve of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material in Example 1 at liquid nitrogen temperature is as Figure 9 shown. From Figure 9 it can be seen that the hydrogen uptake and desorption amount of this material reaches 5.48 wt%; the adsorption rate time-pressure curve of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material is as Figure 12 shown. From Figure 12 it can be seen that this material reaches the same pressure as that of porous carbon during hydrogen absorption in less than 4 hours, and dehydrogenation only takes 2.57 hours, further proving that the porous carbon supported by scandium atoms prepared by the low-temperature process of the present invention greatly improves the hydrogen absorption and dehydrogenation performance of the porous carbon material.

[0064] In terms of the structural characterization of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material in Example 1, Figure 14 are the scanning electron microscope images of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material at different magnifications. From Figure 14 it can be observed that some pore structures of the porous carbon are filled with scandium atoms, making the surface of the material partially smooth, and at the same time there are a large number of fine pore structures, indicating that the loading of single-atom scandium increases the pore structure of the porous carbon without significantly changing the morphology structure and size distribution of the porous carbon; from Figure 16 the microstructure of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material in it can be seen that the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material also shows a pore-like distribution, but its pore volume is smaller than that of the porous carbon powder obtained by low-temperature calcination treatment in Comparative Example 1; from Figure 17 it can be seen that the scandium atoms of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material are evenly distributed on the surface and pores of the mesoporous carbon material, forming highly dispersed scandium atom clusters; from Figure 18 it can be seen that after the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material is treated with scandium-containing, a new peak appears at 401.9 eV corresponding to the scandium element, indicating that the scandium element is successfully doped into the porous carbon, and the doping content is 0.51 at%, proving the success of the synthesis method; from Figure 19 it can be observed that the particle size range of the three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage material is about 10 microns, and its surface is distributed with fine pore structures. Figure 20EDS energy spectrum analysis in it shows that C and Sc elements are evenly distributed in the scandium-loaded porous carbon material. However, the carbon content in the porous carbon is much higher than that of scandium in it, indicating that only part of scandium is doped into the porous carbon structure, which plays a role in modifying its atomic structure, rather than forming a composite material or generating a phase change phenomenon.

[0065] Example 2

[0066] S1: Prepare a porous carbon material dispersion

[0067] Add 500 mL of deionized water to a beaker, and then gradually add 1.5 g of porous carbon powder (specific surface area is 2000 - 2100 m 2 g -1 ). While adding the porous carbon material, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, then perform ultrasonic treatment for 15 minutes, and then use a magnetic stirrer to stir at a speed of 500 r / min for 75 minutes to obtain a porous carbon material dispersion;

[0068] S2: Prepare a scandium chloride dispersion

[0069] Add 50 mL of deionized water to a beaker, and then add 1 g of ScCl3·H2O solid powder. While adding the ScCl3·H2O solid powder, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, and heat in a water bath at 40 °C, then perform ultrasonic treatment for 10 minutes, and then use a magnetic stirrer to stir at 500 r / min for 50 minutes to obtain a scandium chloride dispersion;

[0070] S3: Prepare a porous carbon material - scandium chloride precursor dispersion

[0071] Mix the porous carbon material dispersion and the scandium chloride dispersion in a volume ratio of 1:1 and stir with a magnetic stirrer at a speed of 50 r / min for 30 min, then increase the stirring speed and stir at a speed of 200 r / min in a water bath at 50 °C for 8 hours to obtain a porous carbon material - scandium chloride precursor dispersion;

[0072] S4: Centrifugation

[0073] Let the porous carbon material - scandium chloride precursor dispersion stand at room temperature for 6 hours to fully react and precipitate. Then, centrifuge with a centrifuge at a centrifugation speed of 12000 r / min for 10 minutes, pour off the supernatant, and retain the black precipitate of the porous carbon material - scandium chloride precursor material;

[0074] S5: Prepare a three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material

[0075] The porous carbon material-scandium chloride precursor material was vacuum dried at 100 °C for 10 hours, then placed in a tube furnace. Under an argon atmosphere, it was heated to 200 °C at a rate of 10 °C / min and calcined at 200 °C for 2 hours, and then cooled to room temperature to obtain a solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon. The nitrogen adsorption-desorption test results of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon show that the adsorption and desorption amount of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon is 952 cm 3 g -1 , significantly exceeding the adsorption and desorption amount of porous carbon and slightly higher than the adsorption and desorption amount of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon in Example 1; the hydrogen adsorption and desorption amount of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon at liquid nitrogen temperature reached 5.57 wt%, which is not much different from the hydrogen adsorption and desorption amount of the solid hydrogen storage material of transition metal single-atom scandium supported on three-dimensional porous carbon in Example 1.

[0076] Example 3

[0077] S1: Prepare a dispersion of porous carbon material

[0078] Add 500 mL of deionized water to a beaker, and then gradually add 0.8 g of porous carbon powder (specific surface area 2000 - 2100 m 2 g -1 ). While adding the porous carbon material, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, then perform ultrasonic treatment for 15 minutes, and then use a magnetic stirrer to stir at a speed of 500 r / min for 60 minutes to obtain a dispersion of porous carbon material;

[0079] S2: Prepare a dispersion of scandium chloride

[0080] Add 50 mL of deionized water to a beaker, and then add 600 mg of ScCl3·H2O solid powder. While adding the ScCl3·H2O solid powder, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, and heat in a water bath at 40 °C, then perform ultrasonic treatment for 10 minutes, and then use a magnetic stirrer to stir at 500 r / min for 50 minutes to obtain a dispersion of scandium chloride;

[0081] S3: Prepare a dispersion of porous carbon material-scandium chloride precursor

[0082] After stirring the dispersion of porous carbon material and the dispersion of scandium chloride at a volume ratio of 1:1 with a magnetic stirrer at a speed of 50 r / min for 30 min, increase the stirring speed and stir at a speed of 200 r / min in a water bath at 50 °C for 8 hours to obtain a dispersion of porous carbon material-scandium chloride precursor;

[0083] S4: Centrifugation

[0084] Let the porous carbon material-scandium chloride precursor dispersion stand at room temperature for 6 hours to fully react and precipitate. Then, centrifuge it with a centrifuge at a speed of 12,000 r / min for 10 minutes. Pour off the supernatant and retain the black precipitate of the porous carbon material-scandium chloride precursor material at the bottom layer.

[0085] S5: Preparation of three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material

[0086] Vacuum-dry the porous carbon material-scandium chloride precursor material at 100 °C for 10 hours. Then, place it in a tube furnace. Under an argon atmosphere, heat it to 200 °C at a rate of 10 °C / min and calcine it at 200 °C for 2 hours. Cool it down to room temperature to obtain a three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material. The nitrogen adsorption-desorption test results of this three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material show that the adsorption and desorption amount of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material is 860 cm 3 g -1 , significantly exceeding the adsorption and desorption amount of porous carbon, slightly lower than the adsorption and desorption amount of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material in Example 1. The adsorption and desorption hydrogen amount of this three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material reaches 5.32 wt% at liquid nitrogen temperature, with little difference from the adsorption and desorption hydrogen amount of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material in Example 1.

[0087] Comparative Example 1

[0088] Place the porous carbon powder (specific surface area: 2000 - 2100 m 2 g -1 ) in a vacuum oven, set the temperature to 100 °C, and conduct drying treatment for 10 hours. Keep the vacuum state during the drying process to ensure complete evaporation of moisture. After drying, take out the porous carbon powder and place it in a tube furnace. Under an argon atmosphere, heat it to 200 °C at a rate of 10 °C / min and calcine it at 200 °C for 2 hours. Cool it down to room temperature, and keep the argon atmosphere during this period to prevent oxidation, to obtain the porous carbon powder treated by low-temperature calcination.

[0089] The nitrogen adsorption-desorption isotherm curve of the porous carbon powder treated by low-temperature calcination in Comparative Example 1 is as Figure 1 shown. From Figure 1 the results, it shows that the nitrogen adsorption and desorption amount of the porous carbon is 670 cm 3 g -1 ; The pore distribution and X-ray diffraction pattern of this porous carbon powder treated by low-temperature calcination are respectively as Figure 3 ,Figure 5 As shown, it can be concluded from the test results that the porous carbon has mesoporous and microporous structures and obvious characteristic peaks in the characterization.

[0090] Regarding the performance test of the porous carbon powder subjected to low-temperature calcination treatment in Comparative Example 1, Figure 7 is the hydrogen adsorption-desorption isotherm curve of the porous carbon powder subjected to low-temperature calcination treatment at nitrogen temperature. From Figure 7 it can be seen that when the pressure is 40 Pa, the porous carbon reaches a hydrogen adsorption-desorption amount of 4.4 wt%; from Figure 10 it can be observed that the pressure of the porous carbon reaches 50.1 Pa after 5.9 hours of hydrogen absorption, and it takes 4.3 hours for dehydrogenation.

[0091] Figure 13 is the scanning electron microscope image of the porous carbon powder subjected to low-temperature calcination treatment at different magnification factors. From Figure 13 it can be known that the porous carbon presents a blocky amorphous morphology, the particle size of the particles is 7 to 9 microns, its surface is relatively smooth, and a large number of tiny pores are distributed on it; from Figure 15 it can be observed that the microstructure of the porous carbon powder subjected to low-temperature calcination treatment consists of many mesopores.

[0092] Control group with dispersant added in Comparative Example 2

[0093] S1: Prepare the porous carbon material dispersion

[0094] Add 500 mL of deionized water to a beaker, then add 1 g of porous carbon powder (specific surface area 2000 - 2100 m 2 g -1 ) and 1 g of dispersant Pluronic F127. While adding the porous carbon material, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, then perform ultrasonic treatment for 15 minutes, and then use a magnetic stirrer to stir at a speed of 500 r / min for 60 minutes to obtain the porous carbon material dispersion;

[0095] S2: Prepare the scandium chloride dispersion

[0096] Add 50 mL of deionized water to a beaker, then add 800 mg of ScCl3·H2O solid powder. While adding the ScCl3·H2O solid powder, use a magnetic stirrer to stir at a speed of 500 r / min for 30 minutes, and heat in a water bath at 40 °C, then perform ultrasonic treatment for 10 minutes, and then use a magnetic stirrer to stir at 500 r / min for 30 minutes to obtain the scandium chloride dispersion;

[0097] S3: Prepare the porous carbon material-scandium chloride precursor dispersion

[0098] After dispersing the porous carbon material dispersion and scandium chloride dispersion in a volume ratio of 1:1 and stirring them with a magnetic stirrer at a speed of 50 r / min for 30 min, the stirring speed was increased, and they were stirred at a speed of 200 r / min in a water bath at 50 °C for 8 hours to obtain a porous carbon material-scandium chloride precursor dispersion;

[0099] S4: Centrifugation treatment

[0100] The porous carbon material-scandium chloride precursor dispersion was left standing at room temperature for 3 hours to allow sufficient reaction and precipitation. Then, it was centrifuged using a centrifuge at a centrifugation speed of 8000 r / min for 30 minutes. The supernatant was poured off, and the black precipitate, the porous carbon material-scandium chloride precursor material, was retained;

[0101] S5: Preparation of a three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material

[0102] The porous carbon material-scandium chloride precursor material was vacuum dried at 100 °C for 10 hours, and then placed in a tube furnace. Under an argon atmosphere, it was heated to 200 °C at a rate of 10 °C / min and calcined at 200 °C for 2 hours, and then cooled to room temperature to obtain a three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127.

[0103] Comparative Example 2 was a parallel test of adding the dispersant Pluronic F127 during the preparation process based on Example 1 of the present invention. The adsorption and desorption isotherm curve of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127 at liquid nitrogen temperature was as Figure 8 shown. It can be seen from Figure 8 that the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127 only achieved a hydrogen adsorption and desorption capacity of 1.12 wt%. Therefore, the addition of the dispersant did not promote hydrogen storage; the adsorption rate and time-pressure curve graph of the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127 was as Figure 11 shown. It can be seen from Figure 11 that for the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material added with the dispersant Pluronic F127, the hydrogen adsorption reached a pressure of 50.3 Pa at 4 hours, and the dehydrogenation only took 3 hours, which was faster than the hydrogen adsorption and desorption rate of the porous carbon powder treated by low-temperature calcination in Comparative Example 1.

[0104] In Comparative Example 3, a small amount of scandium was added under low-temperature pyrolysis conditions

[0105] Change the mass fraction of the ScCl3·H2O dispersion prepared in Step 2 of Example 1 to 0.6 wt%, and keep other steps the same as in Example 1 to obtain a solid hydrogen storage material of a small amount of transition metal single-atom scandium supported on three-dimensional porous carbon.

[0106] For the solid hydrogen storage material of a small amount of transition metal single-atom scandium supported on three-dimensional porous carbon in Comparative Example 3, the hydrogen adsorption and desorption amount only reaches 0.9 wt% at liquid nitrogen temperature. The addition of scandium can reduce the activation energy of the chemical reaction. In the case of too little scandium, it is difficult to prepare a solid hydrogen storage material of a transition metal single-atom scandium supported on three-dimensional porous carbon with good performance at a low pyrolysis temperature; at 5 hours of hydrogen absorption, the pressure is only 47 Pa, and it takes 6 hours for dehydrogenation, which is slower than the hydrogen adsorption and desorption rate of the solid hydrogen storage material of a transition metal single-atom scandium supported on three-dimensional porous carbon in Example 1 of the parallel experiment.

[0107] Comparative Example 4 High-temperature pyrolysis

[0108] Change the temperature in the tube furnace in Step S5 of Example 1 from 200 °C in Example 1 to 600 °C, and keep other steps the same as in Example 1 to obtain a solid hydrogen storage material of a transition metal single-atom scandium supported on three-dimensional porous carbon by high-temperature pyrolysis.

[0109] For the solid hydrogen storage material of a transition metal single-atom scandium supported on three-dimensional porous carbon by high-temperature pyrolysis in Comparative Example 4, the hydrogen adsorption and desorption amount reaches 4.9 wt% at liquid nitrogen temperature. High-temperature pyrolysis reduces the activation energy of the reaction. At 5 hours of hydrogen absorption, the pressure reaches 50 Pa, and it only takes 4 hours for dehydrogenation.

[0110] Comparative Example 5 Adding excessive scandium under low-temperature pyrolysis

[0111] Change the mass fraction of the ScCl3·H2O dispersion prepared in Step 2 of Example 1 to 2.5 wt%, and keep other steps the same as in Example 1 to obtain a solid hydrogen storage material of an excessive amount of transition metal single-atom scandium supported on three-dimensional porous carbon.

[0112] For the solid hydrogen storage material of an excessive amount of transition metal single-atom scandium supported on three-dimensional porous carbon in Comparative Example 5, the hydrogen adsorption and desorption amount only reaches 1.3 wt% at liquid nitrogen temperature. At 4.6 hours of hydrogen absorption, the pressure does not reach 50 Pa, and it takes 5 hours for dehydrogenation. It is speculated that due to too high scandium content, aggregates are formed in the porous carbon material, reducing the thermal stability of the material, and heat treatment at a higher temperature is required to achieve a stable structure and performance.

[0113] Comparative Example 6 Adding excessive scandium under high-temperature pyrolysis

[0114] Change the mass fraction of the ScCl3·H2O dispersion prepared in Step 2 of Example 1 to 2.5 wt%, and change the temperature in the tubular furnace in Step S5 from 200 °C in Example 1 to 600 °C. Other steps are the same as in Example 1 to obtain a solid hydrogen storage material of three-dimensional porous carbon loaded with excessive transition metal single-atom scandium by high-temperature pyrolysis.

[0115] For the solid hydrogen storage material of three-dimensional porous carbon loaded with excessive transition metal single-atom scandium by high-temperature pyrolysis in Comparative Example 6, the hydrogen absorption and desorption amount at liquid nitrogen temperature reached 5 wt%. Its hydrogen absorption reached 50 Pa at 4.5 hours, and dehydrogenation took 4 hours. The content of scandium is too high. Although under the condition of high pyrolysis temperature, some excessive scandium accumulates in the pores, eventually leading to pore blockage, and there are problems of over-crystallization and structural damage of the material caused by high-temperature pyrolysis, making the performance of the material unstable, thus reducing the hydrogen adsorption capacity of the scandium-loaded porous carbon material.

[0116] I. Structural and performance analysis of Example 1 of the present invention and Comparative Examples 1 and 2 of its parallel tests

[0117] From Figure 5 、 Figure 6 it can be seen that when the diffraction angle is about 32°, Figure 6 the porous carbon loaded with scandium has one more diffraction peak than the Figure 5 porous carbon, which indicates that highly pure scandium with good crystallinity is formed in the porous carbon. And there is no existence of other impurity peaks because the composite material has a very high purity.

[0118] Figure 7 When the pressure of the porous carbon powder treated by low-temperature calcination is 40 Pa, the porous carbon reaches a hydrogen absorption and desorption amount of 4.4 wt%, and the hydrogen absorption and dehydrogenation curves basically coincide. Figure 8 For the solid hydrogen storage material of three-dimensional porous carbon loaded with transition metal single-atom scandium added with the dispersant Pluronic F127, the hydrogen absorption and desorption amount is 1.12 wt%. Combining the characterization analysis of the material, it is speculated that the dispersant is added in excess, and its effect is not completely volatilized during the drying process, blocking some pores of the scandium-loaded porous carbon material. Figure 8 The hysteresis curve in Figure 9 also further illustrates the capillary condensation phenomenon caused by the remaining dispersant in the mesopores.

[0119] Figure 10 For the porous carbon powder treated by low-temperature calcination in Figure 11The solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon with the dispersant Pluronic F127 added shows that the porous carbon material loaded with scandium atoms and added with the dispersant absorbs hydrogen. At 4 hours, the pressure reaches 50.3 Pa, and dehydrogenation only takes 3 hours, which is faster than the hydrogen absorption and desorption rate of the porous carbon powder treated by low-temperature calcination. And Figure 12 The solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon reaches the same pressure as that during hydrogen absorption of porous carbon in less than 4 hours, and dehydrogenation only takes 2.57 hours, which further proves that the addition of scandium atoms improves the hydrogen absorption and dehydrogenation performance. The reason why the hydrogen absorption and dehydrogenation rate of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon with the dispersant Pluronic F127 added is slower than that of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon may be that the excessive addition of the dispersant does not completely volatilize and occupies the pores of the porous carbon.

[0120] II. Effect analysis of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon in Example 1 of the present invention

[0121] Comparing the test results of BET, XRD, and SEM of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon in Example 1 with the porous carbon powder treated by low-temperature calcination in Comparative Example 1, it can be seen that the hydrogen storage performance of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon in Example 1 is more excellent than that of the porous carbon powder treated by low-temperature calcination in Comparative Example 1. Analyzing the reason, it may be that the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon in Example 1 provides more active sites for hydrogen storage; the hydrogen storage performance of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon with the dispersant added as the control group is not as good as that of the solid-state hydrogen storage material of scandium single atoms of transition metals supported on three-dimensional porous carbon in Example 1 of the parallel test. First of all, the amount of the dispersant added is difficult to control. Excessive addition of the dispersant will occupy the pores of the scandium-loaded porous carbon, while a small amount of the dispersant added does not play a very positive role in the process of preparing the material for scandium atoms.

Claims

1. A method for preparing a three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material, characterized in that: Specific steps as follows: S1: Preparation of porous carbon material dispersion The porous carbon powder is dispersed in deionized water according to the mass ratio of porous carbon powder to deionized water (0.8-1.5):500 to obtain a porous carbon material dispersion; S2: Preparation of Scandium Chloride Dispersion Dissolve ScCl3·H2O in deionized water according to the mass ratio of ScCl3·H2O to deionized water (0.6-1):50 to obtain a scandium chloride dispersion; S3: Preparation of porous carbon material-scandium chloride (ScCl3·H2O) precursor dispersion The porous carbon material dispersion liquid and the scandium chloride dispersion liquid are mixed in a volume ratio of 10:1 and stirred evenly to obtain a porous carbon material-scandium chloride precursor dispersion liquid; S4: Centrifugation The porous carbon material-scandium chloride precursor dispersion is allowed to stand, and then centrifuged to retain the filter cake to obtain a porous carbon material-scandium chloride precursor material; S5: Preparation of three-dimensional porous carbon-supported transition metal single-atom scandium solid-state hydrogen storage materials The porous carbon material-scandium chloride precursor material is placed in a vacuum oven for drying, then placed in a tubular furnace, heated to 200°C in an argon atmosphere and calcined for 2 hours, and then cooled to room temperature to obtain a three-dimensional porous carbon-loaded transition metal single atom scandium solid hydrogen storage material.

2. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: When the S1 porous carbon powder is dispersed in deionized water, the porous carbon material is first added to the deionized water while being stirred with a magnetic stirrer, and then ultrasonically treated for 15 minutes under ultrasonic conditions, and then stirred with a magnetic stirrer.

3. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 2, characterized in that: During the stirring in step S1, the stirring speed is 500 r / min, the first stirring time is 30 min, and the second stirring time is 60-75 min.

4. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: When ScCl3·H2O is dispersed in deionized water in step S2, ScCl3·H2O is first added to the deionized water while being stirred for the first time using a magnetic stirrer, then ultrasonically treated for 10 minutes under ultrasonic conditions, and then stirred for the second time using a magnetic stirrer.

5. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 4, characterized in that: During the stirring in step S2, the stirring speed is 500 r / min, the first stirring time is 30 min, and the second stirring time is 30 to 50 min.

6. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: In step S3, the mixture is stirred at 50 r / min for 30 min using a magnetic stirrer, and then stirred at 200 r / min for 8 h in a 50° C. water bath.

7. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: During the centrifugal treatment, the centrifugal speed was 12000 r / min and the centrifugal time was 10 min.

8. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: During drying, the drying temperature is 100°C and the drying time is 10 hours.

9. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: The specific surface area of ​​the porous carbon is 2000-2100m 2 g -1 .

10. The method for preparing the three-dimensional porous carbon-supported transition metal single-atom scandium solid hydrogen storage material according to claim 1, characterized in that: The heating rate of the tube furnace was 10°C / min.

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