A magnesium-based composite solid-state hydrogen storage material, hydrogen fuel cell system and hydrogen-powered electric bicycle

Abstract

The present invention discloses a magnesium-based composite solid-state hydrogen storage material, a hydrogen fuel cell system, and a hydrogen-powered electric bicycle. The solid-state hydrogen storage material is prepared by mixing MgH2 powder and a composite doped catalytic material and ball milling, wherein the composite doped catalytic material is prepared by the following method: S1, preparing titanium-cerium co-doped carbon dots; S2, preparing Ni-doped mesoporous ferric oxide@carbon nanotube composite materials; S3, grafting TiCe-CDs onto NiFeO@MWCNTs to prepare the composite doped catalytic material. The hydrogen-powered electric bicycle of the present invention uses solid hydrogen as an energy source, has the advantages of safety, high efficiency, energy saving, and environmental protection, and can meet market demand. By adding the composite doped catalytic material to the MgH2 hydrogen storage alloy, the present invention can significantly improve the hydrogen desorption performance of the MgH2 hydrogen storage alloy, significantly reduce the hydrogen desorption temperature, and improve its cycle stability.

Description

Technical Field

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

[0002] Bicycles, especially electric bicycles, hold an irreplaceable and unique position in the existing public transportation system due to their flexibility. They serve as a vital link between destinations and major transportation hubs like subway stations and bus stops. Currently, most electric bicycles on the market are powered by lithium batteries. However, these batteries have long charging times and limited capacity, limiting their range. Furthermore, the initial and subsequent pollution from lithium batteries is a long-term environmental concern.

[0003] Hydrogen is considered an ideal clean energy source, boasting advantages such as light weight, abundant reserves, and environmental friendliness. Solid-state hydrogen storage technology, with its high volumetric hydrogen storage density, low hydrogen storage pressure, and high safety, has garnered widespread attention and holds great potential for application in electric bicycles. For example, patent CN110606160B describes a hydrogen-powered bicycle using low-pressure solid-state hydrogen storage as its hydrogen source.

[0004] Among various solid-state hydrogen storage materials, MgH2 has attracted much attention due to its high hydrogen storage capacity (7.6wt%), wide availability (Mg content in the earth's crust reaches 2.3wt%), low cost and non-toxicity. However, the high thermodynamic stability of MgH2 (ΔH = -74.7kJ / mol H2) and slow kinetics of hydrogen absorption and desorption lead to a relatively high desorption temperature (>300°C), and the hydrogen absorption and desorption reaction rate is very slow, and the cyclic stability is poor, which seriously limits its wide application. Patent CN114955990B provides a magnesium hydride composite hydrogen storage material doped with aluminum carbonitride and a preparation method thereof, which has the advantages of excellent hydrogen storage performance, environmental protection, easy preparation, low cost, etc., and the use of aluminum carbonitride doped magnesium hydride can achieve an improvement effect comparable to MXene. However, its initial hydrogen desorption temperature is still relatively high (around 195°C), and it is necessary to further reduce its initial hydrogen desorption temperature.

[0005] Therefore, it is necessary to improve the existing technology 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-state hydrogen storage material, a hydrogen fuel cell system and a hydrogen-powered electric bicycle in response to the above-mentioned deficiencies in the prior art.

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

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

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

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

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

[0012] Preferably, the preparation method of the magnesium-based composite solid hydrogen storage material is: mixing MgH2 powder and the composite doped catalytic material, and ball milling, the ball milling process is: argon atmosphere, rotation speed 300-550r / min, ball-to-material ratio 30:1-45:1, and ball milling time 4-16h.

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

[0014] 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 milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 25 min, and cycle.

[0015] Preferably, step S1 is specifically:

[0016] 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 ultrasonically disperse for 15-60 min. Transfer the resulting precursor solution to a polytetrafluoroethylene-lined reactor and react at 170-210° C. for 4-12 h.

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

[0018] Preferably, step S2 is specifically:

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

[0020] S2-2, adding 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 dispersing for 30-90 min; then adding 0.081-0.324 g of FeCl3 and 0.032-0.13 g of NiCl2, and ultrasonically dispersing for 5-30 min, adjusting the pH value of the solution to 8-10 with ammonia water, and transferring the resulting mixture to a polytetrafluoroethylene-lined reactor, and reacting at 150-185° C. for 6-24 h;

[0021] 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 1-4 hours to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs.

[0022] Preferably, step S3 is specifically:

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

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

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

[0026] S1. Preparation of 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0028] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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.

[0029] S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials:

[0030] S2-1. 0.5 g of multi-walled carbon nanotubes was added to 150 mL of a mixed acid solution consisting of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. The mixture was heated under reflux at 80° C. for 6 h, cooled to room temperature, filtered, and the solid product was washed with deionized water until neutral, and vacuum dried at 90° C. for 12 h to obtain carboxylated carbon nanotubes.

[0031] S2-2, 0.15g of carboxylated carbon nanotubes and 0.5g of triblock copolymer P123 were added to 150mL of deionized water and ultrasonically dispersed for 60min; then 0.162g of FeCl3 and 0.065g of NiCl2 were added and ultrasonically dispersed for 15min. The pH value of the solution was adjusted to 10 with 20% ammonia water. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 170°C for 12h;

[0032] 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 vacuum at 100°C for 8 h, and then calcined at 400°C in an air atmosphere for 2 h to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs;

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

[0034] S3-1, taking 0.18g of TiCe-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min to obtain a carbon dot dispersion;

[0035] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours to obtain a composite doped catalytic material.

[0036] In a second aspect, the present invention provides a hydrogen fuel cell system comprising a hydrogen supply module for providing hydrogen and a fuel cell module for generating electricity using hydrogen, wherein the hydrogen supply module uses the magnesium-based composite solid hydrogen storage material as described above to provide hydrogen.

[0037] The third aspect of the present invention provides a hydrogen electric bicycle, comprising a vehicle body, the hydrogen fuel cell system as described above, and a drive system, wherein 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.

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

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

[0040] The present invention prepares a composite doped catalytic material, TiCe-CDs@NiFeO@MWCNTs, which is constructed by a three-step hydrothermal reaction and is composed of titanium-cerium co-doped carbon dots, Ni-doped mesoporous ferric oxide, and carboxylated carbon nanotubes. The composite doped catalytic material has a significant effect on improving the hydrogen absorption and desorption performance and cyclic stability of MgH2 hydrogen storage alloys. By adding the composite doped catalytic material to the MgH2 hydrogen storage alloy, the hydrogen desorption performance of the MgH2 hydrogen storage alloy can be significantly improved, the hydrogen desorption temperature can be greatly reduced, and the cyclic stability can be improved. BRIEF 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 This is the infrared absorption spectrum of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1;

[0043] Figure 3 The antioxidant performance test results of the titanium-cerium co-doped carbon dots TiCe-CDs prepared in Example 1 are as follows;

[0044] Figure 4 The test results of the initial hydrogen desorption temperature of the hydrogen storage materials prepared in Examples and Comparative Examples are as follows;

[0045] Figure 5 The test results of hydrogen storage density of hydrogen storage materials prepared in Examples and Comparative Examples are as follows;

[0046] Figure 6 The test results of the capacity retention rate of the hydrogen storage materials prepared in the examples and comparative examples are as follows;

[0047] Figure 7 The hydrogen release curves of the hydrogen storage materials of Example 3 and Comparative Examples 1-6 are as follows:

[0048] Figure 8 is the hydrogen release curve of the hydrogen storage material of Example 1; DETAILED DESCRIPTION

[0049] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0050] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0051] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Materials and reagents used in the following examples are commercially available unless otherwise specified. In the following examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0052] The present invention provides a magnesium-based composite solid-state hydrogen storage material, which is prepared by mixing MgH2 powder and a composite doped catalytic material and ball milling, wherein the composite doped catalytic material is prepared by the following method:

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

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

[0055] S3. Grafting TiCe-CDs onto NiFeO@MWCNTs to prepare a composite doped catalytic material.

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

[0057] In a preferred embodiment, the preparation method of the magnesium-based composite solid hydrogen storage material is: mixing MgH2 powder and the composite doped catalytic material, and ball milling, the ball milling process is: argon atmosphere, rotation speed 300-550r / min, ball-to-material ratio 30:1-45:1, and ball milling time 4-16h.

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

[0059] S1. Preparation of Titanium-Cerium Co-doped Carbon Dots:

[0060] S1-1. Add 375-1500 mg of tartaric acid, 90-360 mg of urea, 156-624 mg of bipyridine (2,2'-bipyridine is used in the present invention), 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 ultrasonically disperse for 15-60 min. Transfer the resulting precursor solution to a polytetrafluoroethylene-lined reactor and react at 170-210° C. for 4-12 h.

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

[0062] S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials:

[0063] S2-1. Add multi-walled carbon nanotubes to a mixed acid of sulfuric acid and nitric acid, heat under reflux for 3-12 hours, 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, adding 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 dispersing for 30-90 min; then adding 0.081-0.324 g of FeCl3 and 0.032-0.13 g of NiCl2, and ultrasonically dispersing for 5-30 min, adjusting the pH value of the solution to 8-10 with ammonia water, and transferring the resulting mixture to a polytetrafluoroethylene-lined reactor, and reacting at 150-185° C. for 6-24 h;

[0065] 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 1-4 hours to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs.

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

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

[0068] This invention uses a three-step hydrothermal reaction to prepare a composite doped catalytic material composed of titanium-cerium co-doped carbon dots, Ni-doped mesoporous ferric oxide, and carboxylated carbon nanotubes. This material significantly improves the hydrogen absorption and desorption performance and cyclic stability of MgH2 hydrogen storage alloys. The addition of the composite doped catalytic material to the MgH2 hydrogen storage alloy significantly improves the alloy's desorption performance, significantly reduces its desorption temperature, and enhances its cyclic stability. The following details the preparation principle and mechanism of action to facilitate understanding of the invention.

[0069] 1. Preparation Principle

[0070] Firstly, titanium and cerium co-doped reduced carbon dots TiCe-CDs were prepared by hydrothermal reaction using tartaric acid, urea, and bipyridine as carbon sources and titanium chloride and cerium trichloride as doping components.

[0071] The carbon nanotubes were then modified with strong acid to introduce abundant carboxyl functional groups, resulting in carboxylated carbon nanotubes. Using the triblock copolymer P123 as a soft template, Ni-doped mesoporous ferric oxide particles were in situ synthesized on the carboxylated carbon nanotubes via a one-pot hydrothermal method combined with high-temperature calcination, yielding the Ni-doped mesoporous ferric oxide@carbon nanotube composite material, 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 yielding a composite doped catalytic material. In this step, NiFeO@MWCNTs are first soaked in dilute acid to generate a large amount of metal ions (Fe3+, Ni2+) on their surface. The materials are then mixed with TiCe-CDs, which are rich in functional groups such as carboxyl and hydroxyl groups. Through coordination, complexation, and electrostatic adsorption between the carboxyl and hydroxyl functional groups and the metal ions, the TiCe-CDs are uniformly bonded to the NiFeO@MWCNTs. Finally, a hydrothermal reaction forms stable chemical bonds, achieving a strong grafting. This results in a ternary grafted composite structure system of titanium-cerium co-doped carbon dots, Ni-doped mesoporous ferric oxide, and carboxylated carbon nanotubes: TiCe-CDs@NiFeO@MWCNTs, the final composite doped catalytic material.

[0073] 2. Mechanism of Action

[0074] 1. The role of titanium-cerium doped carbon dots

[0075] The carbon dots inherit the reducing properties of tartaric acid and bipyridine, have good antioxidant properties, can effectively prevent the oxidation of MgH2, and ensure the cyclic stability of magnesium-based hydrogen storage materials. During the ball milling process, the milling action will destroy the oxide layer on the surface of the alloy. As a nano-carbon material, carbon dots have good reducing properties, which enable them to react with the oxide layer and / or prevent the formation of new oxide layers, thereby 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 the carbon dots exists in an oxidized state, and cerium oxide has excellent catalytic properties for the absorption and desorption of hydrogen in hydrogen storage materials. The catalytic performance mainly depends on the valence change characteristics of cerium ions and the oxygen vacancy concentration that changes with the valence change of cerium ions (Zhang Guofang, Zhai Tingting, Hou Zhonghui, et al. Study on the influence of spectral characteristics of nano-CeO2-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] Titanium doped into carbon dots can enter the CeO2 lattice, partially replacing cerium and causing lattice distortion / defects, thus improving catalytic performance. High oxygen vacancy concentrations and high lattice distortion can enhance surface electron transfer activity and increase the diffusion rate of H. Furthermore, titanium doping can reduce the dissociation barrier of the Mg-H bond, lowering the activation energy of MgH2 and extending the material's service life.

[0078] Titanium-cerium doped carbon dots can act as defect centers or nucleation sites, facilitating the movement of surrounding atoms and increasing the driving force of the hydrogen desorption reaction. Furthermore, the small size, high specific surface area, and rich surface functional groups of carbon dots that can interact with hydrogen molecules provide a large number of active sites for hydrogen adsorption, thereby enhancing physical hydrogen storage capacity. Furthermore, carbon dots have excellent electron transfer properties and can increase electron density, which is beneficial for catalyzing and promoting hydrogen absorption and desorption reactions. Titanium-cerium doping can enhance the carbon dots' improvement on hydrogen absorption and desorption. Therefore, in the titanium-cerium doped carbon dot system, titanium, cerium, and carbon dots work together to achieve a synergistic enhancement effect.

[0079] 2. The role of multi-walled carbon nanotubes

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

[0081] Multi-walled carbon nanotubes have a hollow structure and can be used as a "container" for hydrogen storage. When properly heated, hydrogen can be slowly released, thereby giving the hydrogen storage material certain physical adsorption hydrogen storage properties.

[0082] 3. Effect of nickel-doped ferric oxide mesoporous microspheres

[0083] Nickel-doped ferric oxide mesoporous microspheres have a rich mesoporous structure, which can enhance the material's ability to physically adsorb and store hydrogen; and their high specific surface area allows the material surface to expose more active sites, providing more channels for hydrogen diffusion, thereby helping to improve hydrogen absorption and desorption performance; during the ball milling process, nickel-doped ferric oxide mesoporous microspheres can also serve as a grinding aid to increase the new surface of MgH2 particles.

[0084] As a transition metal oxide, nickel-doped ferric oxide can reduce the hydrogen absorption and desorption temperature of MgH2 and improve the hydrogen absorption and desorption kinetics (Zhang Yao, Li Shouquan, Ying Tiao, et al. Effect of ball-milled surface coating on the electrochemical properties of magnesium-based hydrogen storage alloys [J]. Journal of Nonferrous Metals, 2001, 11(004): 582-586. DOI: 10.3321 / j.issn: 1004-0609.2001.04.010.); Ni doping can facilitate the activation of hydrogen molecules and enhance 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 magnesium-based hydrogen storage alloys and promote the uniform mixing of composite doped catalytic materials with MgH2 during ball milling.

[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 MgH2 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 electricity using hydrogen. The hydrogen supply module uses the above magnesium-based composite solid hydrogen storage material to provide hydrogen.

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

[0089] The magnesium-based composite solid-state hydrogen storage material prepared by the present invention can also be used in many scenarios such as hydrogen fuel cell vehicles, distributed energy supply, large batteries, and backup power supplies. It should be understood that when the magnesium-based composite solid-state hydrogen storage material is applied to scenarios such as hydrogen-powered electric bicycles and hydrogen fuel cell vehicles, a corresponding thermal management system is required to provide the temperature environment required for hydrogen desorption. However, since the hydrogen desorption temperature of the material in the present invention is significantly reduced, 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. Detailed examples and comparative examples are provided below to further illustrate the present invention.

[0091] Sources of main raw materials:

[0092] MgH2, purity 99%, Jiangsu Bosite Chemical Technology Co., Ltd.;

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

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

[0095] Titanium chloride, ferric 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 is prepared by mixing MgH2 powder passed through a 200-mesh sieve and a composite doped catalytic material in a mass ratio of 100:18, and ball milling.

[0100] 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 milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 25 min, and cycle.

[0101] The composite doped catalytic material is prepared by the following method:

[0102] S1. Preparation of Titanium-Cerium Co-doped Carbon Dots:

[0103] 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0104] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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.

[0105] S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials:

[0106] S2-1. 0.5 g of multi-walled carbon nanotubes was added to 150 mL of a mixed acid solution consisting of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. The mixture was heated under reflux at 80° C. for 6 h, cooled to room temperature, filtered, and the solid product was washed with deionized water until neutral, and vacuum dried at 90° C. for 12 h to obtain carboxylated carbon nanotubes.

[0107] S2-2, 0.15g of carboxylated carbon nanotubes and 0.5g of triblock copolymer P123 were added to 150mL of deionized water and ultrasonically dispersed for 60min; then 0.162g of FeCl3 and 0.065g of NiCl2 were added and ultrasonically dispersed for 15min. The pH value of the solution was adjusted to 10 with 20% ammonia water. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 170°C for 12h;

[0108] 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 vacuum at 100°C for 8 h, and then calcined at 400°C in an air atmosphere for 2 h to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs;

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

[0110] S3-1, taking 0.18g of TiCe-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min to obtain a carbon dot dispersion;

[0111] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours to obtain a composite doped catalytic material.

[0112] Example 2

[0113] A magnesium-based composite solid hydrogen storage material is prepared by mixing MgH2 powder passed through a 200-mesh sieve and a composite doped catalytic material in a mass ratio of 100:17, and ball milling;

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

[0115] The composite doped catalytic material is prepared by the following method:

[0116] S1. Preparation of 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0118] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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.

[0119] S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials:

[0120] S2-1. 0.5 g of multi-walled carbon nanotubes was added to 150 mL of a mixed acid solution consisting of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. The mixture was heated under reflux at 80° C. for 6 h, cooled to room temperature, filtered, and the solid product was washed with deionized water until neutral, and vacuum dried at 90° C. for 12 h to obtain carboxylated carbon nanotubes.

[0121] S2-2, 0.15g of carboxylated carbon nanotubes and 0.5g of triblock copolymer P123 were added to 150mL of deionized water and ultrasonically dispersed for 60min; then 0.162g of FeCl3 and 0.065g of NiCl2 were added and ultrasonically dispersed for 15min. The pH value of the solution was adjusted to 10 with 20% ammonia water. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 170°C for 12h;

[0122] 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 vacuum at 100°C for 8 h, and then calcined at 400°C in an air atmosphere for 2 h to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs;

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

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

[0125] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours to obtain a composite doped catalytic material.

[0126] Example 3

[0127] A magnesium-based composite solid hydrogen storage material is prepared by mixing MgH2 powder passed through a 200-mesh sieve and a composite doped catalytic material in a mass ratio of 100:16.5, and ball milling.

[0128] The ball milling process is as follows: argon atmosphere, rotation speed 480 r / min, ball-to-material ratio 40:1, ball milling time 10 h, and ball milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 25 min, and cycle.

[0129] The composite doped catalytic material is prepared by the following method:

[0130] S1. Preparation of 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0132] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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.

[0133] S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials:

[0134] S2-1. 0.5 g of multi-walled carbon nanotubes was added to 150 mL of a mixed acid solution consisting of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:1. The mixture was heated under reflux at 80° C. for 6 h, cooled to room temperature, filtered, and the solid product was washed with deionized water until neutral, and vacuum dried at 90° C. for 12 h to obtain carboxylated carbon nanotubes.

[0135] S2-2, 0.15g of carboxylated carbon nanotubes and 0.5g of triblock copolymer P123 were added to 150mL of deionized water and ultrasonically dispersed for 60min; then 0.162g of FeCl3 and 0.065g of NiCl2 were added and ultrasonically dispersed for 15min. The pH value of the solution was adjusted to 10 with 20% ammonia water. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 170°C for 12h;

[0136] 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 vacuum at 100°C for 8 h, and then calcined at 400°C in an air atmosphere for 2 h to obtain a Ni-doped mesoporous iron oxide@carbon nanotube composite material: NiFeO@MWCNTs;

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

[0138] S3-1, taking 0.18g of TiCe-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min to obtain a carbon dot dispersion;

[0139] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours 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 electricity using hydrogen. The hydrogen supply module uses the magnesium-based composite solid-state hydrogen storage material of Example 1 to provide hydrogen.

[0142] Example 5

[0143] A hydrogen-powered electric bicycle comprises 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 provides driving force for the vehicle body using the electrical energy provided by the hydrogen fuel cell system.

[0144] Comparative Example 1

[0145] The MgH2 powder passed through a 200-mesh sieve was ball-milled according to the same process as in Example 1 to obtain an undoped MgH2 hydrogen storage alloy for comparative analysis.

[0146] Comparative Example 2

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

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

[0149] Comparative Example 3

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

[0151] In this example, the composite doped catalytic material is 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0154] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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 cerium-doped carbon dots: Ce-CDs.

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

[0156] S3. Grafting Ce-CDs onto NiFeO@MWCNTs to prepare a composite doped catalytic material:

[0157] S3-1, taking 0.18g of Ce-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min to obtain a carbon dot dispersion;

[0158] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours to obtain a composite doped catalytic material.

[0159] Comparative Example 4

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

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

[0162] S1. Preparation of 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours;

[0164] S1-2. After the reaction is completed, cool to room temperature, centrifuge at 2500 rpm for 10 min, collect the supernatant, and 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 cerium-doped carbon dots: Ti-CDs.

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

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

[0167] S3-1, taking 0.18g of Ti-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min to obtain a carbon dot dispersion;

[0168] S3-2. Take 0.5 g of NiFeO@MWCNTs prepared in step S2 and add it to 100 mL of 5% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 at 80°C for 12 hours to obtain a composite doped catalytic material.

[0169] Comparative Example 5

[0170] A magnesium-based composite solid hydrogen storage material is prepared by mixing MgH2 powder passed through a 200-mesh sieve, titanium-cerium co-doped carbon dots, and carboxylated carbon nanotubes in a mass ratio of 100:4.8:13.2, and ball milling.

[0171] 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 milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 25 min, and cycle.

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

[0173] Comparative Example 6

[0174] A magnesium-based composite solid hydrogen storage material is prepared by mixing MgH2 powder passed through a 200-mesh sieve, titanium-cerium co-doped carbon dots, and Ni-doped mesoporous ferric oxide@carbon nanotube composite material in a mass ratio of 100:4.8:13.2, and ball milling the mixture.

[0175] 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 milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 25 min, and cycle.

[0176] The preparation methods of the titanium-cerium co-doped carbon dots and the Ni-doped mesoporous ferric oxide@carbon nanotube composite materials are the same as those in Example 1.

[0177] 1. Performance Characterization

[0178] 1. Reference Figure 1 , which is the XRD pattern of the composite doped catalytic material TiCe-CDs@NiFeO@MWCNTs prepared in Example 1. The pattern can illustrate the successful synthesis of the composite doped catalytic material.

[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 analyzer 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, the 1590 cm -1 The absorption peak is derived 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 oxidation resistance 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 the antioxidant properties of the dispersion were tested at different times using a DPPH free radical scavenging ability test kit (Hefei Lyle 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 , which 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 were measured using the H-Sorb 2600 fully automatic PCT hydrogen storage material tester.

[0187] 2. Cyclic stability test: 30 complete hydrogen absorption / desorption cycles are performed at 300°C (hydrogen desorption pressure 0.2 MPa, hydrogen absorption pressure 5 MPa), the hydrogen storage capacity (hydrogen storage density) is measured, and then the capacity retention rate is calculated. Capacity retention rate = (hydrogen storage capacity after multiple cycles / initial hydrogen storage capacity) × 100%.

[0188] The test results are shown in Table 1 and Figure 4-8 As shown, Figure 4-Figure 6 The following are the test results of initial hydrogen release temperature, hydrogen storage density, and capacity retention rate; Figure 7 The heating hydrogen release curves of Example 3 and Comparative Examples 1-6 at 5 MPa are shown below. Figure 8 This is the hydrogen desorption curve of Example 1 at 300°C and 0.2 MPa.

[0189] Table 1

[0190] Initial hydrogen release temperature (℃) 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] The above test results show that the magnesium-based composite solid-state hydrogen storage materials prepared in Examples 1-3 exhibit significantly lower initial dehydrogenation temperatures than the MgH2 hydrogen storage alloy prepared in Comparative Example 1. Furthermore, Examples 1-3 exhibit higher hydrogen storage densities and excellent cyclic stability, with significantly improved cyclic stability compared to the MgH2 hydrogen storage alloy prepared in Comparative Example 1. The increase in initial dehydrogenation temperature in Comparative Example 2 is attributed to the lack of titanium-cerium co-doped carbon dots in the hydrogen storage material system. Furthermore, due to the reduced oxidation resistance, the cyclic stability performance also significantly decreased. The increase in initial dehydrogenation temperature in Comparative Examples 3 and 4 demonstrates that titanium and cerium doping promotes the dehydrogenation performance of the hydrogen storage material. The overall performance degradation in Comparative Example 5 is primarily due to the lack of Ni-doped mesoporous ferric oxide in the hydrogen storage material system. The overall performance degradation in Comparative Example 6 is attributed to the failure to construct the composite doped catalytic material system TiCe-CDs@NiFeO@MWCNTs with TiCe-CDs and NiFeO@MWCNTs as described in Example 1.

[0192] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A magnesium-based composite solid hydrogen storage material, characterized in that: The composite doped catalytic material is prepared by mixing MgH2 powder and a composite doped catalytic material and ball milling, 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 comprises the following steps: mixing MgH2 powder and composite doped catalytic material, and ball milling. The ball milling process comprises the following steps: argon atmosphere, rotation speed of 300-550 r / min, ball-to-material ratio of 30:1-45:1, and ball milling time of 4-16 hours.

4. The magnesium-based composite solid hydrogen storage material according to claim 3, characterized in that: The preparation method comprises the following steps: mixing MgH2 powder passed through a 200-mesh sieve and a composite doped catalytic material in a mass ratio of 100:18, and ball milling; 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 milling in forward and reverse intermittent mode: forward rotation 25 min, stop 5 min, reverse rotation 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 ultrasonically disperse for 15-60 min. Transfer the resulting 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 using a dialysis bag for 12-36 hours, collect the product in the dialysis bag, and freeze-dry to 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. Add multi-walled carbon nanotubes to a mixed acid of sulfuric acid and nitric acid, heat under reflux for 3-12 hours, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry to obtain carboxylated carbon nanotubes; S2-2, adding 0.075-0.3g of carboxylated carbon nanotubes and 0.25-1g of triblock copolymer P123 to 75-300mL of deionized water, and ultrasonically dispersing for 30-90min; then adding 0.081-0.324g of FeCl3 and 0.032-0.13g of NiCl2, and ultrasonically dispersing for 5-30min, adjusting the pH value of the solution to 8-10 with ammonia water, and transferring the resulting mixture to a polytetrafluoroethylene-lined reactor, and reacting 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 1-4 hours 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 0.09-0.36g of TiCe-CDs prepared in step S1, adding it to 50-200mL of deionized water, and ultrasonically dispersing it for 15-60min to obtain a carbon dot dispersion; S3-2. Take 0.25-1 g of NiFeO@MWCNTs prepared in step S2 and add it to 50-200 mL of citric acid aqueous solution with a mass concentration of 2.5-8%. After soaking for 2-10 minutes, filter and remove it. Add it to the carbon dot dispersion under stirring, ultrasonically disperse it for 30-90 minutes, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 110-140°C for 3-8 hours, 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, 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, add them to a mixed solvent consisting of 120 mL of deionized water and 80 mL of ethanol, and ultrasonically disperse them for 30 minutes. The resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 6 hours; S1-2. After the reaction, the mixture was cooled to room temperature and centrifuged at 2500 rpm for 10 min. The supernatant was collected and dialyzed in deionized water using a dialysis bag with a molecular weight cutoff of 1500 Da for 24 h. The water was changed every 8 h. The product in the dialysis bag was collected and freeze-dried to obtain titanium-cerium co-doped carbon dots: TiCe-CDs. S2. Preparation of Ni-doped mesoporous Fe2O3@CNT composite materials: S2-1. 0.5 g of multi-walled carbon nanotubes was added to 150 mL of a mixed acid solution consisting of 95 wt% sulfuric acid and 60 wt% nitric acid in a volume ratio of 2:

1. The mixture was heated under reflux at 80° C. for 6 h, cooled to room temperature, filtered, and the solid product was washed with deionized water until neutral, and vacuum dried at 90° C. for 12 h to obtain carboxylated carbon nanotubes. S2-2, 0.15g of carboxylated carbon nanotubes and 0.5g of triblock copolymer P123 were added to 150mL of deionized water and ultrasonically dispersed for 60min; then 0.162g of FeCl3 and 0.065g of NiCl2 were added and ultrasonically dispersed for 15min. The pH value of the solution was adjusted to 10 with 20% ammonia water. The resulting 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 and filtered. The solid product is washed with deionized water, dried in vacuum at 100°C for 8 h, and then calcined at 400°C in an air atmosphere for 2 h 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 0.18g of TiCe-CDs prepared in step S1, adding it to 100mL of deionized water, and ultrasonically dispersing it for 30min 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% mass concentration of citric acid aqueous solution. After soaking for 5 minutes, filter and take out, add it to the carbon dot dispersion under stirring, ultrasonically disperse for 60 minutes, transfer the resulting 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 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 according to 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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