Magnesium-based composite solid hydrogen storage material, hydrogen fuel cell system and hydrogen energy electric bicycle

Abstract

The invention discloses a magnesium-based composite solid hydrogen storage material, a hydrogen fuel cell system and a hydrogen energy electric bicycle, the solid hydrogen storage material is prepared by mixing and ball-milling MgH2 powder and a composite doped catalytic material, and the composite doped catalytic material is prepared by the following method: S1, preparing titanium-cerium co-doped carbon dots; s2, preparing a Ni-doped mesoporous ferric oxide and carbon nanotube composite material; s3, the TiCe-CDs are grafted to the NiFeO (at) MWCNTs, and the composite doped catalytic material is prepared and obtained. The hydrogen energy electric bicycle provided by the invention takes solid hydrogen as energy, has the advantages of safety, high efficiency, energy conservation, environmental protection and the like, and can meet market requirements. By adding the composite doped catalytic material into the MgH2 hydrogen storage alloy, the hydrogen desorption performance of the MgH2 hydrogen storage alloy can be remarkably improved, the hydrogen desorption temperature can be greatly reduced, and the cycle stability of the MgH2 hydrogen storage alloy can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen energy, and particularly to a magnesium-based composite solid hydrogen storage material, a hydrogen fuel cell system, and a hydrogen energy electric bicycle. Background Art

[0002] Bicycles, especially electric bicycles, have an irreplaceable special status in the existing public transportation system due to their flexibility, and play a role in connecting destinations with large transportation stations such as subway stations and bus stops. Most electric bicycles on the market currently use lithium battery power sources, but lithium batteries have a long charging time and limited capacity, which makes electric bicycles can only travel within a limited range; moreover, the pollution in the early and later stages of lithium batteries is also a long-term environmental problem.

[0003] Hydrogen energy is considered an ideal clean energy source, with advantages such as light mass, rich reserves, and environmental friendliness. Solid hydrogen storage technology has characteristics such as high volumetric hydrogen storage density, low hydrogen storage pressure, and high safety, and has received extensive attention and has great potential for application in electric bicycles. For example, a hydrogen energy bicycle using low-pressure solid hydrogen storage as the hydrogen source provided by Patent CN110606160B.

[0004] Among various solid hydrogen storage materials, MgH 2 has attracted much attention due to its high hydrogen storage capacity (7.6 wt%), wide source (Mg content in the earth's crust reaches 2.3 wt%), low cost, and non-toxicity. However, MgH 2 has relatively high thermodynamic stability (ΔH = -74.7 kJ / mol H2) and slow kinetics of hydrogen absorption / desorption, resulting in a relatively high desorption temperature (>300 °C), and the hydrogen absorption and desorption reaction rates are very slow, and the cycle stability is poor, which severely limits its wide application. Patent CN114955990B provides a magnesium hydride composite hydrogen storage material doped with aluminum carbonitride and its preparation method, which has advantages such as excellent hydrogen storage performance, environmental protection, easy preparation, and low cost, and doping magnesium hydride with aluminum carbonitride can obtain an improvement effect comparable to that of MXene. However, its initial hydrogen release temperature is still relatively high (about 195 °C), and it is necessary to further reduce its initial hydrogen release temperature.

[0005] Therefore, it is necessary to improve the existing technology now to provide a more reliable solution. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a magnesium-based composite solid hydrogen storage material, a hydrogen fuel cell system, and a hydrogen energy electric bicycle in view of the deficiencies in the above-mentioned existing technology.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: In the first aspect of the present invention, a magnesium-based composite solid hydrogen storage material is provided, which is obtained by mixing MgH2 It is prepared by mixing and ball-milling MgH₂ powder and a composite doped catalytic material, wherein the composite doped catalytic material is prepared by the following method:

[0008] S1. Prepare titanium-cerium co-doped carbon dots: TiCe-CDs;

[0009] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs;

[0010] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material.

[0011] Preferably, the mass ratio of MgH₂ powder to the composite doped catalytic material is 100:5 - 25. 2 The mass ratio of MgH₂ powder to the composite doped catalytic material is 100:5 - 25.

[0012] Preferably, the preparation method of the magnesium-based composite solid-state hydrogen storage material is as follows: Mix MgH₂ powder and the composite doped catalytic material, and ball-mill. The ball-milling process is as follows: argon atmosphere, rotation speed 300 - 550 r / min, ball-to-material ratio 30:1 - 45:1, ball-milling time 4 - 16 h. 2 The mass ratio of MgH₂ powder to the composite doped catalytic material is 100:5 - 25. The ball-milling process is as follows: argon atmosphere, rotation speed 300 - 550 r / min, ball-to-material ratio 30:1 - 45:1, ball-milling time 4 - 16 h.

[0013] Preferably, the preparation method of the magnesium-based composite solid-state hydrogen storage material is as follows: Mix MgH₂ powder passing through a 200-mesh sieve and the composite doped catalytic material in a mass ratio of 100:18, and ball-mill; 2 The mass ratio of MgH₂ powder passing through a 200-mesh sieve and the composite doped catalytic material is 100:18, and ball-mill;

[0014] Among them, the ball-milling process is as follows: argon atmosphere, rotation speed 450 r / min, ball-to-material ratio 40:1, ball-milling time 8 h, and ball-mill in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0015] Preferably, step S1 is specifically as follows:

[0016] S1-1. Take 375 - 1500 mg of tartaric acid, 90 - 360 mg of urea, 156 - 624 mg of bipyridine, 95 - 380 mg of titanium chloride, and 92.5 - 370 mg of cerium trichloride and add them to a mixed solvent composed of 60 - 240 mL of deionized water and 40 - 160 mL of ethanol, ultrasonically disperse for 15 - 60 min, transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 170 - 210 °C for 4 - 12 h;

[0017] S1-2. After the reaction, cool to room temperature, centrifuge, collect the supernatant, dialyze in deionized water with a dialysis bag for 12 - 36 h, collect the product inside the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0018] Preferably, step S2 is specifically as follows:

[0019] S2-1. Take multi-walled carbon nanotubes and add them to a mixed acid composed of sulfuric acid and nitric acid. Heat under reflux for 3 - 12 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and dry it under vacuum to obtain carboxylated carbon nanotubes;

[0020] S2-2. Add 0.075 - 0.3 g of carboxylated carbon nanotubes and 0.25 - 1 g of triblock copolymer P123 (polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer) to 75 - 300 mL of deionized water, and ultrasonically disperse for 30 - 90 min; then add 0.081 - 0.324 g of FeCl 3 、0.032 - 0.13 g of NiCl 2 , ultrasonically disperse for 5 - 30 min, adjust the pH value of the solution to 8 - 10 using ammonia water, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner lining, and react at 150 - 185 °C for 6 - 24 h;

[0021] S2-3. After the reaction, cool to room temperature, filter, wash the solid product with deionized water, dry it under vacuum, and then calcine it in an air atmosphere at 380 - 450 °C for 1 - 4 h to obtain a Ni-doped mesoporous iron oxide @ carbon nanotube composite: NiFeO@MWCNTs.

[0022] Preferably, step S3 is specifically as follows:

[0023] S3-1. Take 0.09 - 0.36 g of the TiCe-CDs prepared in step S1 and add it to 50 - 200 mL of deionized water, and ultrasonically disperse for 15 - 60 min to obtain a carbon dot dispersion;

[0024] S3-2. Take 0.25 - 1 g of the NiFeO@MWCNTs prepared in step S2 and add it to 50 - 200 mL of a citric acid aqueous solution with a mass concentration of 2.5 - 8%. After impregnation for 2 - 10 min, filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 30 - 90 min, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner lining, react at 110 - 140 °C for 3 - 8 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and dry it under vacuum to obtain a composite doped catalytic material.

[0025] Preferably, the composite doped catalytic material is prepared by the following method:

[0026] S1. Prepare titanium-cerium co-doped carbon dots:

[0027] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, 190 mg of titanium chloride, and 185 mg of cerium trichloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol. Ultrasonically disperse for 30 min, transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 190 °C for 6 h;

[0028] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water for 24 h using a dialysis bag with a molecular weight cut-off of 1500 Da, change the water every 8 h, collect the product inside the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0029] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite:

[0030] S2-1. Take 0.5 g of multi-walled carbon nanotubes and add them to 150 mL of a mixed acid composed of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. Heat and reflux at 80 °C for 6 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90 °C for 12 h to obtain carboxylated carbon nanotubes;

[0031] S2-2. Add 0.15 g of carboxylated carbon nanotubes and 0.5 g of triblock copolymer P123 to 150 mL of deionized water, and ultrasonically disperse for 60 min; then add 0.162 g of FeCl 3 、0.065 g of NiCl 2 , ultrasonically disperse for 15 min, adjust the pH value of the solution to 10 using 20% ammonia water by mass concentration, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 170 °C for 12 h;

[0032] S2-3. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water, vacuum dry at 100 °C for 8 h, and then calcine in an air atmosphere at 400 °C for 2 h to obtain Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs;

[0033] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material:

[0034] S3-1. Take 0.18 g of TiCe-CDs prepared in step S1 and add them to 100 mL of deionized water, ultrasonically disperse for 30 min to obtain a carbon dot dispersion;

[0035] S3-2. Take 0.5 g of the NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of a citric acid aqueous solution with a mass concentration of 5%. After impregnation for 5 min, filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the obtained mixture to a reaction kettle lined with polytetrafluoroethylene, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry at 80 °C for 12 h to obtain a composite doped catalytic material.

[0036] In the second aspect of the present invention, a hydrogen fuel cell system is provided, including a hydrogen supply module for providing hydrogen and a fuel cell module for generating electric energy using hydrogen. The hydrogen supply module uses the magnesium-based composite solid hydrogen storage material as described above to provide hydrogen.

[0037] In the third aspect of the present invention, a hydrogen energy electric bicycle is provided, including a vehicle body, the hydrogen fuel cell system as described above, and a drive system. The hydrogen fuel cell system generates electric energy using hydrogen, and the drive system uses the electric energy provided by the hydrogen fuel cell system to provide driving force for the vehicle body.

[0038] The beneficial effects of the present invention are as follows:

[0039] The present invention provides a magnesium-based composite solid hydrogen storage material and a hydrogen fuel cell system and a hydrogen energy electric bicycle based on it. The hydrogen energy electric bicycle of the present invention uses solid hydrogen as an energy source, has the advantages of safety, high efficiency, energy conservation and environmental protection, etc., and can meet the market demand.

[0040] The present invention prepares a composite doped catalytic material TiCe-CDs@NiFeO@MWCNTs constructed by titanium-cerium co-doped carbon dots, Ni-doped mesoporous iron oxide and carboxylated carbon nanotubes through three-step hydrothermal reaction, which has an obvious improvement effect on the hydrogen absorption and desorption performance and cycle stability of the MgH 2 hydrogen storage alloy; by adding this composite doped catalytic material to the MgH 2 hydrogen storage alloy, the desorption performance of the MgH 2 hydrogen storage alloy can be significantly improved, the desorption temperature can be greatly reduced, and its cycle stability can be improved. Description of the Drawings

[0041] Figure 1 XRD pattern of the composite doped catalytic material TiCe-CDs@NiFeO@MWCNTs prepared in Example 1;

[0042] Figure 2 Infrared absorption spectrum of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1;

[0043] Figure 3Test results of the antioxidant properties of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1;

[0044] Figure 4 Test results of the initial hydrogen desorption temperature of the hydrogen storage materials prepared in the examples and comparative examples;

[0045] Figure 5 Test results of the hydrogen storage density of the hydrogen storage materials prepared in the examples and comparative examples;

[0046] Figure 6 Test results of the capacity retention rate of the hydrogen storage materials prepared in the examples and comparative examples;

[0047] Figure 7 Hydrogen desorption curves of the hydrogen storage materials of Example 3 and Comparative Examples 1-6;

[0048] Figure 8 Hydrogen desorption curve of the hydrogen storage material of Example 1; Detailed implementation mode

[0049] The following examples are used to further elaborate the present invention in detail, so that those skilled in the art can implement it according to the text of the specification.

[0050] It should be understood that terms such as "having", "including", and "comprising" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0051] Unless otherwise specified, the test methods used in the following examples are all conventional methods. Unless otherwise specified, the materials and reagents used in the following examples can all be obtained through commercial channels. For those not specifying specific conditions in the following examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be purchased commercially.

[0052] The present invention provides a magnesium-based composite solid hydrogen storage material, which is prepared by mixing and ball-milling MgH 2 powder and a composite doping catalyst material, wherein the composite doping catalyst material is prepared by the following method:

[0053] S1. Prepare titanium-cerium co-doped carbon dots: TiCe-CDs;

[0054] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs;

[0055] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare a composite doping catalyst material.

[0056] In a preferred embodiment, MgH2 Powder: The mass ratio of the composite doped catalytic material is 100:5 - 25.

[0057] In a preferred embodiment, the preparation method of the magnesium-based composite solid-state hydrogen storage material is as follows: Mix MgH 2 powder and the composite doped catalytic material, and ball mill. The ball milling process is as follows: in an argon atmosphere, the rotation speed is 300 - 550 r / min, the ball-to-material ratio is 30:1 - 45:1, and the ball milling time is 4 - 16 h.

[0058] In a preferred embodiment, the composite doped catalytic material is prepared by the following method:

[0059] S1. Prepare titanium-cerium co-doped carbon dots:

[0060] S1-1. Take 375 - 1500 mg of tartaric acid, 90 - 360 mg of urea, 156 - 624 mg of bipyridine (in this invention, 2,2'-bipyridine is used), 95 - 380 mg of titanium chloride, and 92.5 - 370 mg of cerium trichloride, and add them to a mixed solvent composed of 60 - 240 mL of deionized water and 40 - 160 mL of ethanol. Ultrasonically disperse for 15 - 60 min, transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 170 - 210 °C for 4 - 12 h;

[0061] S1-2. After the reaction, cool to room temperature, centrifuge, collect the supernatant, dialyze in deionized water with a dialysis bag for 12 - 36 h, collect the product inside the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0062] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite material:

[0063] S2-1. Take multi-walled carbon nanotubes and add them to a mixed acid composed of sulfuric acid and nitric acid. Heat and reflux for 3 - 12 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry to obtain carboxylated carbon nanotubes;

[0064] S2-2. Add 0.075 - 0.3 g of carboxylated carbon nanotubes and 0.25 - 1 g of triblock copolymer P123 (polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer) to 75 - 300 mL of deionized water, and ultrasonically disperse for 30 - 90 min; then add 0.081 - 0.324 g of FeCl 3 and 0.032 - 0.13 g of NiCl 2 , ultrasonically disperse for 5 - 30 min, adjust the pH value of the solution to 8 - 10 with ammonia water, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 150 - 185 °C for 6 - 24 h;

[0065] S2-3. After the reaction, cool to room temperature, filter, wash the solid product with deionized water, dry it under vacuum, and then calcine it in an air atmosphere at 380 - 450 °C for 1 - 4 h to obtain the Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs.

[0066] S3-1. Take 0.09 - 0.36 g of the TiCe-CDs prepared in step S1 and add it to 50 - 200 mL of deionized water, and ultrasonically disperse it for 15 - 60 min to obtain a carbon dot dispersion;

[0067] S3-2. Take 0.25 - 1 g of the NiFeO@MWCNTs prepared in step S2 and add it to 50 - 200 mL of a citric acid aqueous solution with a mass concentration of 2.5 - 8%. After impregnation for 2 - 10 min, filter it out and add it to the carbon dot dispersion under stirring, ultrasonically disperse it for 30 - 90 min, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner liner, react at 110 - 140 °C for 3 - 8 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and dry it under vacuum to obtain the composite doped catalytic material.

[0068] The present invention prepares a composite doped catalytic material composed of titanium and cerium co-doped carbon dots, Ni-doped mesoporous iron oxide, and carboxylated carbon nanotubes through three-step hydrothermal reaction, which has an obvious improvement effect on the hydrogen absorption and desorption performance and cycle stability of the MgH 2 hydrogen storage alloy. In the present invention, by adding the composite doped catalytic material to the MgH 2 hydrogen storage alloy, the dehydrogenation performance of the MgH 2 hydrogen storage alloy can be significantly improved, the dehydrogenation temperature can be greatly reduced, and its cycle stability can be improved. The preparation principle and action mechanism are described in detail below for the understanding of the present invention.

[0069] I. Preparation Principle

[0070] First, using tartaric acid, urea, and bipyridine as carbon sources, and titanium chloride and cerium trichloride as doping components, a reduced carbon dot TiCe-CDs co-doped with titanium and cerium is prepared through hydrothermal reaction;

[0071] Then, the carbon nanotubes are modified with strong acid to introduce rich carboxyl functional groups to obtain carboxylated carbon nanotubes. Then, using the triblock copolymer P123 as a soft template, Ni-doped mesoporous iron oxide particles are in-situ synthesized on the carboxylated carbon nanotubes through a one-pot hydrothermal method combined with high-temperature calcination to obtain the Ni-doped mesoporous iron oxide@carbon nanotube composite NiFeO@MWCNTs;

[0072] Finally, NiFeO@MWCNTs and TiCe-CDs are subjected to a one-pot hydrothermal reaction to uniformly and firmly modify TiCe-CDs onto NiFeO@MWCNTs, ultimately obtaining a composite doped catalytic material. In this step, NiFeO@MWCNTs are first soaked in dilute acid to generate a large number of metal ions (Fe3+, Ni2+) on its surface, and then mixed with TiCe-CDs rich in functional groups such as carboxyl and hydroxyl groups on the surface. Through the coordination, complexation, electrostatic adsorption, etc. between the carboxyl, hydroxyl and other functional groups and metal ions, TiCe-CDs are uniformly bound to NiFeO@MWCNTs. Finally, through the hydrothermal reaction, stable chemical bonds are formed to achieve firm grafting, constructing a ternary grafted composite structure system of titanium and cerium co-doped carbon dots-Ni-doped mesoporous iron oxide-carboxylated carbon nanotubes: TiCe-CDs@NiFeO@MWCNTs, that is, the final composite doped catalytic material.

[0073] II. Mechanism of action

[0074] 1. Role of titanium and cerium doped carbon dots

[0075] This carbon dot well inherits the reduction properties of tartaric acid and bipyridine, has good antioxidant characteristics, and can effectively avoid the oxidation of MgH 2 to ensure the cycle stability of the magnesium-based hydrogen storage material. During the ball milling process, the ball milling action will damage the oxide layer on the surface of the alloy. As a nano-carbon material with good reducibility, the carbon dot can react with the oxide layer and / or prevent the formation of a new oxide layer, improving the activation performance of the alloy (Wu Junqing, Zhou Shixue, Yang Minjian, et al. Hydrogen storage effect of carbon materials [J]. Coal Science and Technology, 2006, 34(11): 4. DOI: 10.3969 / j.issn.0253-2336.2006.11.025.).

[0076] The cerium doped in this carbon dot exists in an oxidized state. Cerium oxide has excellent catalytic characteristics for the hydrogen absorption and desorption of hydrogen storage materials. This catalytic performance mainly depends on the variable valence characteristics of cerium ions and the concentration of oxygen vacancies that changes with the valence change of cerium ions (Zhang Guofang, Zhai Tingting, Hou Zhonghui, et al. Study on the influence of the spectral characteristics of nano-CeO 2 -xNx solid solution on its catalytic performance [J]. Spectroscopy and Spectral Analysis, 2018, 38(10): 7. DOI: 10.3964 / j.issn.1000-0593(2018)10-3192-07.).

[0077] The titanium doped in the carbon dot can enter CeO 2The lattice, with cerium partially replaced, causes lattice distortion / defects and improves catalytic performance. A high oxygen vacancy concentration and high lattice distortion can enhance the surface electron transfer activity and increase the diffusion rate of H. Meanwhile, the doping of titanium can reduce the dissociation energy barrier of the Mg-H bond, lower the activation energy of MgH 2 and improve the service life of the material.

[0078] Titanium and cerium doped carbon dots can serve as defect centers or nucleation points, facilitating the movement of surrounding atoms and increasing the driving force of the hydrogen release reaction. Additionally, the small size, high specific surface area of the carbon dots, and the abundant surface functional groups that can interact with hydrogen molecules can provide a large number of active sites for hydrogen adsorption, thus enhancing the physical hydrogen storage capacity. At the same time, the carbon dots have excellent electron transfer performance and can increase the electron density, which is conducive to catalyzing and promoting the hydrogen absorption and release reactions. The doping of titanium and cerium can enhance the improvement effect of the carbon dots on hydrogen absorption and release. Therefore, in the system of titanium and cerium doped carbon dots, titanium, cerium, and carbon dots play a role of mutual cooperation and synergistic enhancement.

[0079] 2. Role of multi-walled carbon nanotubes

[0080] Multi-walled carbon nanotubes have excellent mechanical strength and can act as a carrier to reduce the pulverization of the hydrogen storage alloy. At the same time, they have high thermal conductivity (the thermal conductivity can reach between 1000 and 3000 W / mK), which can significantly improve the thermal conductivity and thermal uniformity of the hydrogen storage material and improve its hydrogen absorption and release performance.

[0081] Multi-walled carbon nanotubes have a hollow structure and can be used as a "container" for hydrogen storage. When appropriately heated, hydrogen can be slowly released, thus endowing the hydrogen storage material with a certain physical adsorption hydrogen storage performance.

[0082] 3. Role of nickel-doped iron oxide mesoporous microspheres

[0083] Nickel-doped iron oxide mesoporous microspheres have a rich mesoporous structure, which can enhance the physical adsorption hydrogen storage capacity of the material. Moreover, their high specific surface area exposes more active sites on the material surface, providing a more abundant channel for the diffusion of hydrogen, thus facilitating the improvement of hydrogen absorption and release performance. During the ball milling process, nickel-doped iron oxide mesoporous microspheres can also act as a grinding aid to increase the new surface of MgH 2 particles.

[0084] As a transition metal oxide, nickel-doped iron oxide can play a role in reducing the hydrogen absorption and desorption temperature of MgH2 and improving the hydrogen absorption and desorption kinetic performance (Zhang Yao, Li Shouquan, Ying Tiao, et al. Effect of Ball Milling Surface Coating on Electrochemical Performance of Magnesium-Based Hydrogen Storage Alloys [J]. The Chinese Journal of Nonferrous Metals, 2001, 11(004): 582-586. DOI: 10.3321 / j.issn:1004-0609.2001.04.010.); The doping of Ni is beneficial to the activation of hydrogen molecules and enhances the catalytic effect.

[0085] On the other hand, the doping of nickel and iron metals and the doping of titanium and cerium in carbon dots can improve the dispersion performance of carbon nanotubes in the magnesium-based hydrogen storage alloy, and can promote the uniform mixing of the composite doped catalytic material with MgH 2 during the ball milling process.

[0086] The composite doped catalytic material system TiCe-CDs@NiFeO@MWCNTs constructed in the present invention can significantly improve the hydrogen absorption and desorption performance of MgH 2 and enhance its cycle stability through the formation of multiphase catalyst components.

[0087] The present invention also provides a hydrogen fuel cell system, including a hydrogen supply module for providing hydrogen and a fuel cell module for generating electric energy using hydrogen. The hydrogen supply module uses the magnesium-based composite solid hydrogen storage material as described above to provide hydrogen.

[0088] The present invention also provides a hydrogen-powered electric bicycle, including a vehicle body, the hydrogen fuel cell system as described above, and a drive system. The hydrogen fuel cell system generates electric energy using hydrogen, and the drive system uses the electric energy provided by the hydrogen fuel cell system to provide driving force for the vehicle body.

[0089] The magnesium-based composite solid hydrogen storage material prepared in the present invention can also be applied in many scenarios such as hydrogen fuel cell vehicles, distributed power supply, large batteries, standby power supplies, etc. It should be understood that when applying the magnesium-based composite solid hydrogen storage material to scenarios such as hydrogen-powered electric bicycles and hydrogen fuel cell vehicles, a corresponding thermal management system needs to be configured to provide the temperature environment required for hydrogen desorption. However, due to the significant decrease in the hydrogen desorption temperature of the material in the present invention, the requirements for the thermal management system are lower, which is more conducive to its application.

[0090] The above is the overall concept of the present invention. Hereinafter, detailed embodiments and comparative examples are provided on this basis to further illustrate the present invention.

[0091] Description of the sources of main raw materials:

[0092] MgH 2 , with a purity of 99%, Jiangsu Bost Chemical Technology Co., Ltd.;

[0093] Multi-walled carbon nanotubes, inner diameter 10 - 20 nm, tube length 10 - 15 μm, Shanghai Maoguo Nano Technology Co., Ltd.;

[0094] Tartaric acid, 2,2'-bipyridine, nickel chloride, Jiangsu Bost Chemical Technology Co., Ltd.;

[0095] Titanium chloride, iron chloride, Jiangsu Runfeng Synthetic Technology Co., Ltd.;

[0096] Cerium trichloride, Nantong Runfeng Petrochemical Co., Ltd.;

[0097] Triblock copolymer P123, Beijing Beike New Materials Technology Co., Ltd.

[0098] Example 1

[0099] A magnesium-based composite solid hydrogen storage material, and its preparation method is: Mix MgH powder passing through a 200-mesh sieve and a composite doping catalytic material in a mass ratio of 100:18, and ball mill; 2 Among them, the ball milling process is: argon atmosphere, rotation speed 450 r / min, ball-to-material ratio 40:1, ball milling time 8 h, and ball milling is carried out in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0100] Among them, the composite doping catalytic material is prepared by the following method:

[0101] S1. Prepare titanium-cerium co-doped carbon dots:

[0102] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, 190 mg of titanium chloride, and 185 mg of cerium trichloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol, ultrasonically disperse for 30 min, transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 190 °C for 6 h;

[0103] S1-2. After the reaction, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water with a dialysis bag with a molecular weight cut-off of 1500 Da for 24 h, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0104] S1-3. After the reaction, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water with a dialysis bag with a molecular weight cut-off of 1500 Da for 24 h, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0105] S2. Prepare Ni-doped mesoporous iron oxide @ carbon nanotube composite material:

[0106] S2-1. Take 0.5 g of multi-walled carbon nanotubes and add them to 150 mL of a mixed acid composed of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. Heat under reflux at 80 °C for 6 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90 °C for 12 h to obtain carboxylated carbon nanotubes;

[0107] S2-2. Add 0.15 g of carboxylated carbon nanotubes and 0.5 g of triblock copolymer P123 to 150 mL of deionized water, and ultrasonically disperse for 60 min; then add 0.162 g of FeCl 3 and 0.065 g of NiCl 2 , ultrasonically disperse for 15 min, adjust the pH value of the solution to 10 with 20% ammonia water by mass concentration, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner lining, and react at 170 °C for 12 h;

[0108] S2-3. After the reaction, cool to room temperature, filter, wash the solid product with deionized water, vacuum dry at 100 °C for 8 h, and then calcine in an air atmosphere at 400 °C for 2 h to obtain Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs;

[0109] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare a composite doped catalytic material:

[0110] S3-1. Take 0.18 g of TiCe-CDs prepared in step S1 and add them to 100 mL of deionized water, and ultrasonically disperse for 30 min to obtain a carbon dot dispersion;

[0111] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add them to 100 mL of a 5% citric acid aqueous solution by mass concentration. After impregnation for 5 min, filter and take out, add them to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner lining, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry at 80 °C for 12 h to obtain a composite doped catalytic material.

[0112] Example 2

[0113] A magnesium-based composite solid hydrogen storage material, and its preparation method is: mix MgH 2 powder that has passed through a 200-mesh sieve and the composite doped catalytic material in a mass ratio of 100:17, and ball mill;

[0114] Among them, the ball milling process is as follows: in an argon atmosphere, the rotation speed is 400 r / min, the ball-to-material ratio is 35:1, the ball milling time is 8 h, and the ball milling is carried out in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0115] Among them, the composite doped catalytic material is prepared by the following method:

[0116] S1. Prepare titanium-cerium co-doped carbon dots:

[0117] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, 190 mg of titanium chloride, and 185 mg of cerium trichloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol. Ultrasonically disperse for 30 min, transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner lining, and react at 190 °C for 6 h;

[0118] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water for 24 h using a dialysis bag with a cut-off molecular weight of 1500 Da, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0119] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite:

[0120] S2-1. Take 0.5 g of multi-walled carbon nanotubes and add them to 150 mL of a mixed acid composed of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. Heat and reflux at 80 °C for 6 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90 °C for 12 h to obtain carboxylated carbon nanotubes;

[0121] S2-2. Add 0.15 g of carboxylated carbon nanotubes and 0.5 g of triblock copolymer P123 to 150 mL of deionized water, and ultrasonically disperse for 60 min; then add 0.162 g of FeCl 3 、0.065 g of NiCl 2 , ultrasonically disperse for 15 min, adjust the pH value of the solution to 10 using 20% ammonia water by mass concentration, transfer the obtained mixture to a reaction kettle with a polytetrafluoroethylene inner lining, and react at 170 °C for 12 h;

[0122] S2-3. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water, vacuum dry at 100 °C for 8 h, and then calcine in an air atmosphere at 400 °C for 2 h to obtain Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs;

[0123] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare a composite doped catalytic material:

[0124] S3-1. Take 0.18 g of the TiCe-CDs prepared in step S1 and add it to 100 mL of deionized water, and ultrasonically disperse for 30 min to obtain a carbon dot dispersion;

[0125] S3-2. Take 0.5 g of the NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of a citric acid aqueous solution with a mass concentration of 5%, impregnate for 5 min, then filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the obtained mixture to a reaction kettle lined with polytetrafluoroethylene, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry at 80 °C for 12 h to obtain the composite doped catalytic material.

[0126] Example 3

[0127] A magnesium-based composite solid hydrogen storage material, and its preparation method is: Mix MgH powder passed through a 200-mesh sieve and the composite doped catalytic material in a mass ratio of 100:16.5, and ball mill; 2 The ball milling process is as follows: In an argon atmosphere, the rotation speed is 480 r / min, the ball-to-material ratio is 40:1, the ball milling time is 10 h, and the ball milling is carried out in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0128] Among them, the composite doped catalytic material is prepared by the following method:

[0129] Among them, the composite doped catalytic material is prepared by the following method:

[0130] S1. Prepare titanium-cerium co-doped carbon dots:

[0131] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, 190 mg of titanium chloride, and 185 mg of cerium trichloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol, ultrasonically disperse for 30 min, transfer the obtained precursor solution to a reaction kettle lined with polytetrafluoroethylene, and react at 190 °C for 6 h;

[0132] S1-2. After the reaction, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water with a dialysis bag with a molecular weight cut-off of 1500 Da for 24 h, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

[0133] S2. Prepare Ni-doped mesoporous iron oxide@carbon nanotube composite:

[0134] S2-1. Take 0.5 g of multi-walled carbon nanotubes and add them to 150 mL of a mixed acid composed of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. Heat under reflux at 80 °C for 6 h, cool to room temperature, filter, wash the solid product with deionized water until neutral, and dry it under vacuum at 90 °C for 12 h to obtain carboxylated carbon nanotubes;

[0135] S2-2. Add 0.15 g of carboxylated carbon nanotubes and 0.5 g of triblock copolymer P123 to 150 mL of deionized water and ultrasonically disperse for 60 min; then add 0.162 g of FeCl 3 , 0.065 g of NiCl 2 , ultrasonically disperse for 15 min, adjust the pH value of the solution to 10 using 20% by mass ammonia water, transfer the resulting mixture to a reaction kettle with a polytetrafluoroethylene inner liner, and react at 170 °C for 12 h;

[0136] S2-3. After the reaction, cool to room temperature, filter, wash the solid product with deionized water, dry it under vacuum at 100 °C for 8 h, and then calcine it in an air atmosphere at 400 °C for 2 h to obtain Ni-doped mesoporous iron oxide@carbon nanotube composite: NiFeO@MWCNTs;

[0137] S3. Graft TiCe-CDs onto NiFeO@MWCNTs to prepare a composite doped catalytic material:

[0138] S3-1. Take 0.18 g of TiCe-CDs prepared in step S1 and add them to 100 mL of deionized water, ultrasonically disperse for 30 min to obtain a carbon dot dispersion;

[0139] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add them to 100 mL of a 5% by mass citric acid aqueous solution. After impregnating for 5 min, filter and take out, add them to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the resulting mixture to a reaction kettle with a polytetrafluoroethylene inner liner, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and dry it under vacuum at 80 °C for 12 h to obtain a composite doped catalytic material.

[0140] Example 4

[0141] A hydrogen fuel cell system includes a hydrogen supply module for providing hydrogen and a fuel cell module for generating electric energy using hydrogen. The hydrogen supply module uses the magnesium-based composite solid hydrogen storage material of Example 1 to provide hydrogen.

[0142] Example 5

[0143] A hydrogen-powered electric bicycle, comprising a vehicle body, the hydrogen fuel cell system of Example 1, and a drive system. The hydrogen fuel cell system generates electrical energy using hydrogen, and the drive system uses the electrical energy provided by the hydrogen fuel cell system to provide driving force for the vehicle body.

[0144] Comparative Example 1

[0145] The MgH powder passed through a 200-mesh sieve was ball-milled according to the same process as in Example 1 to obtain undoped MgH 2 hydrogen storage alloy for comparative analysis. 2

[0146] Comparative Example 2

[0147] The difference between this example and Example 1 is only that:

[0148] In this example, the Ni-doped mesoporous iron oxide@carbon nanotube composite material prepared in Example 1 was used as the composite doping catalyst material.

[0149] Comparative Example 3

[0150] The difference between this example and Example 1 is only that:

[0151] In this example, the composite doping catalyst material was prepared by the following method:

[0152] S1. Preparation of cerium-doped carbon dots:

[0153] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, and 185 mg of cerium trichloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol. Ultrasonically disperse for 30 min, and transfer the obtained precursor solution to a reaction kettle with a polytetrafluoroethylene inner lining. React at 190 °C for 6 h;

[0154] S1-2. After the reaction, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water using a dialysis bag with a molecular weight cut-off of 1500 Da for 24 h, change the water every 8 h, collect the product inside the dialysis bag, and freeze-dry to obtain cerium-doped carbon dots: Ce-CDs.

[0155] S2. Preparation of Ni-doped mesoporous iron oxide@carbon nanotube composite material, the specific method is the same as in Example 1;

[0156] S3. Graft Ce-CDs onto NiFeO@MWCNTs to prepare a composite doping catalyst material:

[0157] S3-1. Take 0.18 g of the Ce-CDs prepared in step S1 and add it to 100 mL of deionized water. Ultrasonically disperse for 30 min to obtain a carbon dot dispersion;

[0158] S3-2. Take 0.5 g of the NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of a 5% citric acid aqueous solution. After impregnation for 5 min, filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the obtained mixture to a reaction kettle lined with polytetrafluoroethylene, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry at 80 °C for 12 h to obtain the composite doped catalytic material.

[0159] Comparative Example 4

[0160] The difference between this example and Example 1 is only that:

[0161] In this example, the composite doped catalytic material is prepared by the following method:

[0162] S1. Prepare cerium-doped carbon dots:

[0163] S1-1. Take 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, and 190 mg of titanium chloride and add them to a mixed solvent composed of 120 mL of deionized water and 80 mL of ethanol. Ultrasonically disperse for 30 min, transfer the obtained precursor solution to a reaction kettle lined with polytetrafluoroethylene, and react at 190 °C for 6 h;

[0164] S1-2. After the reaction, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water with a dialysis bag with a molecular weight cut-off of 1500 Da for 24 h, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain cerium-doped carbon dots: Ti-CDs.

[0165] S2. Prepare the Ni-doped mesoporous iron oxide@carbon nanotube composite material, and the specific method is the same as that in Example 1;

[0166] S3. Graft Ti-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material:

[0167] S3-1. Take 0.18 g of the Ti-CDs prepared in step S1 and add it to 100 mL of deionized water. Ultrasonically disperse for 30 min to obtain the carbon dot dispersion;

[0168] S3-2. Take 0.5 g of the NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of a 5% citric acid aqueous solution. After impregnation for 5 min, filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 min, transfer the obtained mixture to a reaction kettle lined with polytetrafluoroethylene, react at 120 °C for 6 h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry at 80 °C for 12 h to obtain a composite doped catalytic material.

[0169] Comparative Example 5

[0170] A magnesium-based composite solid hydrogen storage material, and its preparation method is as follows: Mix MgH 2 powder, titanium-cerium co-doped carbon dots, and carboxylated carbon nanotubes in a mass ratio of 100:4.8:13.2, and ball mill;

[0171] Among them, the ball milling process is: argon atmosphere, rotation speed 450 r / min, ball-to-material ratio 40:1, ball milling time 8 h, and ball milling is carried out in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0172] Among them, the preparation methods of the titanium-cerium co-doped carbon dots and the carboxylated carbon nanotubes are the same as those in Example 1.

[0173] Comparative Example 6

[0174] A magnesium-based composite solid hydrogen storage material, and its preparation method is as follows: Mix MgH 2 powder, titanium-cerium co-doped carbon dots, and Ni-doped mesoporous iron oxide@carbon nanotube composite material in a mass ratio of 100:4.8:13.2, and ball mill;

[0175] Among them, the ball milling process is: argon atmosphere, rotation speed 450 r / min, ball-to-material ratio 40:1, ball milling time 8 h, and ball milling is carried out in a forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

[0176] Among them, the preparation methods of the titanium-cerium co-doped carbon dots and the Ni-doped mesoporous iron oxide@carbon nanotube composite material are the same as those in Example 1.

[0177] I. Performance Characterization

[0178] 1. Refer to Figure 1 , which is the XRD pattern of the composite doped catalytic material TiCe-CDs@NiFeO@MWCNTs prepared in Example 1. It can be shown from the pattern that the composite doped catalytic material is successfully synthesized.

[0179] 2. The BET specific surface area of ​​the composite doped catalytic material prepared in Example 1 was measured using a BET specific surface area analysis tester and was 470 m 2 / g.

[0180] 3. Reference Figure 2 , is the infrared absorption spectrum of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1. It can be seen that the surface of the carbon dots has abundant functional groups such as carboxyl, hydroxyl, and amino groups. The appearance of the characteristic peaks of Ti-O bonds and Ce-O bonds indicates the successful doping of Ti and Ce. In addition, among them, 1590cm -1 The absorption peak comes from the stretching vibration of the aromatic ring, 785cm -1 The absorption peak originates from the out-of-plane bending vibration of aromatic hydrogen.

[0181] 4. The antioxidant performance of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1 was tested using the following method:

[0182] The TiCe-CDs prepared in Example 1 were prepared into a dispersion with a concentration of 0.5 mg / mL using ethanol, and then the antioxidant properties of the dispersion at different times were tested using a DPPH free radical scavenging ability test kit (Hefei Laier Biotechnology Co., Ltd.).

[0183] Determination principle: DPPH free radical has a single electron, its alcohol solution is purple, and has strong absorption at 515nm. When there is an antioxidant, the DPPH free radical is scavenged, the color becomes lighter, and the absorbance at 515nm decreases. Within a certain range, the change in absorbance is proportional to the degree of free radical scavenging, that is, the lower the absorbance at 515nm, the stronger the nitrogen free radical scavenging ability and the stronger the antioxidant performance.

[0184] Reference Figure 3 , is the test result, it can be seen that the TiCe-CDs has good reduction performance.

[0185] 2. Hydrogen storage material application performance test

[0186] 1. Hydrogen storage density and hydrogen absorption and desorption performance are measured using H-Sorb 2600 fully automatic PCT hydrogen storage material tester.

[0187] 2. Cycle stability test: perform 30 complete hydrogen absorption / desorption cycles at 300°C (hydrogen desorption pressure 0.2MPa, hydrogen absorption pressure 5MPa), measure the hydrogen storage capacity (hydrogen storage density), and then calculate the capacity retention rate, capacity retention rate = (hydrogen storage capacity after multiple cycles / initial hydrogen storage capacity) × 100%.

[0188] The test results are shown in Table 1 and Figures 4 - 8 As shown, Figures 4 - 6The test results of the initial hydrogen release temperature, hydrogen storage density, and capacity retention rate are as follows in sequence; Figure 7 It is the hydrogen release curve during heating at 5 MPa for Example 3 and Comparative Examples 1-6, Figure 8 It is the hydrogen release curve of Example 1 at 300 °C and 0.2 MPa.

[0189] Table 1

[0190] Initial hydrogen release temperature (°C) Hydrogen storage density (wt%) Capacity retention rate (%) Example 1 145 7.13 98.6 Example 2 147 7.11 98.5 Example 3 150 7.06 98.2 Comparative Example 1 330 6.45 86.4 Comparative Example 2 256 6.71 93.9 Comparative Example 3 177 7.04 98.2 Comparative Example 4 192 6.92 97.7 Comparative Example 5 241 6.90 94.4 Comparative Example 6 226 6.98 95.8

[0191] According to the above test results, it can be seen that the magnesium-based composite solid hydrogen storage materials prepared in Examples 1-3 are superior to MgH in Comparative Example 1 2 The initial hydrogen release temperature of the hydrogen storage alloy has been significantly reduced, and Examples 1-3 have a high hydrogen storage density and excellent cycle stability performance. Their cycle stability performance is also significantly improved compared to MgH in Comparative Example 1 2 The hydrogen storage alloy. The initial hydrogen release temperature in Comparative Example 2 has increased, which is attributed to the fact that titanium-cerium co-doped carbon dots are not added to the hydrogen storage material system. At the same time, due to the decrease in antioxidant performance, its cycle stability performance has also decreased significantly. The increase in the initial hydrogen release temperature in Comparative Examples 3 and 4 can prove that the doping of titanium and cerium has a promoting effect on the hydrogen release performance of this hydrogen storage material. The main reason for the overall performance decline in Comparative Example 5 is the lack of the component of Ni-doped mesoporous iron oxide in the hydrogen storage material system; the overall performance decline in Comparative Example 6 is attributed to the failure to construct the composite doping catalytic material system TiCe-CDs@NiFeO@MWCNTs in Example 1 with TiCe-CDs and NiFeO@MWCNTs.

[0192] Although the embodiments of the present invention have been disclosed as above, it is not limited to only the applications listed in the description and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A magnesium-based composite solid hydrogen storage material, characterized in that: The MgH2 powder and the composite doped catalytic material are mixed and ball-milled to prepare the composite doped catalytic material, wherein the composite doped catalytic material is prepared by the following method: S1. Preparation of titanium-cerium co-doped carbon dots: TiCe-CDs; S2. Preparation of Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs; S3, grafting TiCe-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material.

2. The magnesium-based composite solid hydrogen storage material according to claim 1, characterized in that: in, The mass ratio of MgH2 powder: composite doped catalytic material is 100:5-25.

3. The magnesium-based composite solid hydrogen storage material according to claim 2, characterized in that: The preparation method is as follows: MgH2 powder and composite doped catalytic material are mixed, and ball milled. The ball milling process is as follows: argon atmosphere, rotation speed 300-550r / min, ball-to-material ratio 30:1-45:1, and ball milling time 4-16h.

4. The magnesium-based composite solid hydrogen storage material according to claim 3, characterized in that: The preparation method is as follows: MgH2 powder passed through a 200-mesh sieve and a composite doped catalytic material are mixed in a mass ratio of 100:18, and ball milled; The ball milling process is as follows: argon atmosphere, rotation speed of 450 r / min, ball-to-material ratio of 40:1, ball milling time of 8 h, and ball milling in forward and reverse intermittent mode: forward rotation for 25 min, stop for 5 min, reverse rotation for 25 min, and cycle.

5. The magnesium-based composite solid hydrogen storage material according to claim 1, characterized in that: Step S1 is specifically as follows: S1-1, add 375-1500 mg of tartaric acid, 90-360 mg of urea, 156-624 mg of bipyridine, 95-380 mg of titanium chloride, and 92.5-370 mg of cerium trichloride to a mixed solvent consisting of 60-240 mL of deionized water and 40-160 mL of ethanol, and disperse by ultrasonic for 15-60 min. Transfer the obtained precursor solution to a polytetrafluoroethylene-lined reactor, and react at 170-210° C. for 4-12 h. S1-2. After the reaction is completed, cool to room temperature, centrifuge, collect the supernatant, dialyze in deionized water with a dialysis bag for 12-36 hours, collect the product in the dialysis bag, freeze-dry, and obtain titanium-cerium co-doped carbon dots: TiCe-CDs.

6. The magnesium-based composite solid hydrogen storage material according to claim 1, characterized in that: Step S2 is specifically as follows: S2-1, adding multi-walled carbon nanotubes to a mixed acid composed of sulfuric acid and nitric acid, heating and reflux for 3-12 hours, cooling to room temperature, filtering, washing the solid product with deionized water until neutral, and vacuum drying to obtain carboxylated carbon nanotubes; S2-2, add 0.075-0.3g carboxylated carbon nanotubes and 0.25-1g triblock copolymer P123 to 75-300mL deionized water, and ultrasonically disperse for 30-90min; then add 0.081-0.324g FeCl3 and 0.032-0.13g NiCl2, and ultrasonically disperse for 5-30min, and adjust the pH value of the solution to 8-10 with ammonia water, and transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, and react at 150-185°C for 6-24h; S2-3. After the reaction is completed, the mixture is cooled to room temperature and filtered. The solid product is washed with deionized water, dried in vacuo, and then calcined in an air atmosphere at 380-450°C for 1-4h to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs.

7. The magnesium-based composite solid hydrogen storage material according to claim 1, characterized in that: Step S3 is specifically as follows: S3-1, taking 0.09-0.36 g of TiCe-CDs prepared in step S1, adding it into 50-200 mL of deionized water, and ultrasonically dispersing it for 15-60 min to obtain a carbon dot dispersion; S3-2, take 0.25-1g of NiFeO@MWCNTs prepared in step S2, add it to 50-200mL of citric acid aqueous solution with a mass concentration of 2.5-8%, soak for 2-10min, filter and take it out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 30-90min, transfer the obtained mixture to a polytetrafluoroethylene-lined reactor, react at 110-140°C for 3-8h, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry to obtain a composite doped catalytic material.

8. The magnesium-based composite solid hydrogen storage material according to claim 1, characterized in that: The composite doped catalytic material is prepared by the following method: S1. Preparation of Titanium-Cerium Co-doped Carbon Dots: S1-1, add 750 mg of tartaric acid, 180 mg of urea, 312 mg of bipyridine, 190 mg of titanium chloride, and 185 mg of cerium trichloride into a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and disperse by ultrasonic for 30 min. Transfer the obtained precursor solution into a polytetrafluoroethylene-lined reactor and react at 190°C for 6 h. S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, dialyze in deionized water using a dialysis bag with a molecular weight cutoff of 1500 Da for 24 h, change the water every 8 h, collect the product in the dialysis bag, and freeze-dry to obtain titanium-cerium co-doped carbon dots: TiCe-CDs. S2. Preparation of Ni-doped mesoporous iron oxide@carbon nanotube composite materials: S2-1, taking 0.5 g of multi-walled carbon nanotubes, adding 150 mL of a mixed acid composed of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1, heating and reflux at 80°C for 6 h, cooling to room temperature, filtering, washing the solid product with deionized water until neutral, and vacuum drying at 90°C for 12 h to obtain carboxylated carbon nanotubes; S2-2, 0.15g carboxylated carbon nanotubes and 0.5g triblock copolymer P123 were added to 150mL deionized water, and ultrasonic dispersion was performed for 60min; then 0.162g FeCl3 and 0.065g NiCl2 were added, and ultrasonic dispersion was performed for 15min, and the pH value of the solution was adjusted to 10 with 20% ammonia water, and the obtained mixture was transferred to a polytetrafluoroethylene-lined reactor, and reacted at 170°C for 12h; S2-3, after the reaction is completed, the mixture is cooled to room temperature, filtered, and the solid product is washed with deionized water, vacuum dried at 100°C for 8 hours, and then calcined at 400°C in an air atmosphere for 2 hours to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs; S3, grafting TiCe-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material: S3-1, taking 0.18 g of TiCe-CDs prepared in step S1, adding it into 100 mL of deionized water, and ultrasonically dispersing it for 30 min to obtain a carbon dot dispersion; S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% citric acid aqueous solution. After soaking for 5 minutes, filter and take it out. Add it to the carbon dot dispersion under stirring, ultrasonically disperse it for 60 minutes, transfer the obtained mixture to a polytetrafluoroethylene-lined reactor, react at 120°C for 6 hours, cool to room temperature, centrifuge and filter, wash the solid product with deionized water, and vacuum dry it at 80°C for 12 hours to obtain a composite doped catalytic material.

9. A hydrogen fuel cell system, characterized in that: It comprises a hydrogen supply module for providing hydrogen and a fuel cell module for generating electric energy using hydrogen, wherein the hydrogen supply module uses the magnesium-based composite solid hydrogen storage material as described in any one of claims 1 to 8 to provide hydrogen.

10. A hydrogen-powered electric bicycle, characterized in that: It comprises a vehicle body, a hydrogen fuel cell system as claimed in claim 9, and a driving system, wherein the hydrogen fuel cell system generates electrical energy using hydrogen, and the driving system uses the electrical energy provided by the hydrogen fuel cell system to provide driving force for the vehicle body.

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