CN111661816B - MgH2-ternary metal oxide-graphite composite hydrogen storage material and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of hydrogen storage materials, and in particular relates to a MgH ₂ ternary metal oxide-graphite composite hydrogen storage material and a preparation method thereof. The composite hydrogen storage material is formed by mixing ternary metal oxide and graphite with _MgH2 as the base material through magnetic grinding. The present invention adds ternary metal oxide and graphite particles, and the ternary metal oxide coats MgH ₂ crystal particles form an excellent core-shell structure, which has good catalytic effect and remarkable kinetic performance, and the porosity of graphite is also conducive to the adsorption of hydrogen and improves the efficiency of hydrogen absorption; the ternary metal oxide and graphite Addition can effectively eliminate the agglomeration of hydrogen storage materials, and then achieve the purpose of reducing the particle size of the material. Compared with the existing single binary metal oxide, it has better kinetic properties and has good hydrogen absorption and desorption reversibility. , can still exhibit good hydrogen storage performance after multiple cycles at a specific temperature.

Description

MgH2-ternary metal oxide-graphite composite hydrogen storage material and preparation method thereof

technical field

The invention belongs to the technical field of hydrogen storage materials, and in particular relates to a MgH ₂ -ternary metal oxide-graphite composite hydrogen storage material and a preparation method thereof.

Background technique

With the continuous development of global population and economic scale, the global energy and environment are facing a severe situation. The environmental problems caused by energy use and their causes are constantly being recognized by people. Not only the hazards of smog, photochemical smog and acid rain, but also the global climate change caused by the increase of carbon dioxide concentration in the atmosphere has also been confirmed as an indisputable fact. Therefore, there is an urgent need to develop new energy sources, how to efficiently utilize hydrogen energy, and solving the storage of hydrogen energy is the key link for its promotion and application.

As a hydrogen storage material, magnesium metal has the advantages of low density, high hydrogen storage capacity, abundant resources, and low price. Therefore, magnesium-based hydrogen storage alloys are the most promising hydrogen storage materials. Alloying is a simple and effective method to improve Mg-based hydrogen storage alloys, and the material system design and phase structure regulation are directly related to the hydrogen storage performance.

However, the existing hydrogen storage materials have the problems of difficult hydrogen absorption and desorption activation, slow hydrogen absorption and desorption speed (that is, poor hydrogen absorption and desorption kinetics), and poor hydrogen absorption and desorption thermodynamic properties. Usually, it needs to be around 350°C to effectively absorb and desorb. hydrogen.

Contents of the invention

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, to provide a MgH ₂ -ternary metal oxide-graphite composite hydrogen storage material, while maintaining its high hydrogen storage capacity and excellent hydrogen storage kinetic performance At the same time, it can also significantly improve its cyclic hydrogen storage performance, and effectively reduce the degradation of its material properties after repeated hydrogen absorption and desorption; at the same time, the invention also provides its preparation method, which adopts a magnetic grinding method, which has good grinding effect and high work efficiency.

The MgH ₂ -ternary metal oxide-graphite composite hydrogen storage material of the present invention is formed by mixing ternary metal oxide and graphite with MgH ₂ as the base material.

The ternary metal oxide is one of VNbO ₅ , CuCo ₂ O ₄ , MnFe ₂ O ₄ or Co ₂ NiO.

The particle size of the MgH ₂ is 50-100nm.

The mass percent content of the ternary metal oxide in the composite hydrogen storage material is 10-15 wt%, and the particle size is 5-50 μm.

The mass percentage of graphite in the composite hydrogen storage material is 2-3 wt%, and the particle size is 10-30nm.

The preparation method of the _MgH2 -ternary metal oxide-graphite composite hydrogen storage material of the present invention comprises the following steps:

(1) Under the protective atmosphere of inert gas, add the mixture of MgH ₂ , ternary metal oxide and graphite powder into the grinding tank of the electromagnetic grinder, the grinding tank is provided with a magnetic grinding needle, and the grinding chamber is sealed;

(2) Introduce hydrogen gas at a pressure of 5-15MPa, turn on the electromagnetic grinder, and drive the magnetic grinding needle to perform high-speed 360-degree rotating motion after power-on, and perform high-speed collision grinding with the material;

(3) After grinding, the magnetic grinding needles are separated to obtain a composite hydrogen storage material.

The mass ratio of the mixed material described in step (1) to the magnetic grinding needle is 1:10-50, preferably 1:20.

In step (2), the grinding frequency of the electromagnetic grinder is 1800-3600 rpm, the interval between forward and reverse running is 0.5 h, and the total grinding time is 0.5-30 h.

An electromagnet is installed around the grinding tank of the electromagnetic grinding machine. The electromagnet is composed of an electromagnetic coil and an iron core. It uses an electric current to generate an alternating magnetic field, which drives the magnetic grinding needle in the tank to produce shear collision with the material to achieve a better grinding effect. The electromagnet is connected with the voltage and current controller, and is connected with the AC frequency converter to control the grinding condition in the grinding tank.

The composite hydrogen storage material prepared by the present invention is characterized by XRD to contain VNbO ₅ , βMgH ₂ and γMgH ₂ , and the MgH ₂ is converted into βMgH ₂ after hydrogen absorption and desorption once.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. In the present invention, by adding ternary metal oxide and graphite particles, the ternary metal oxide coats MgH ₂ crystal particles to form an excellent core-shell structure, which has good catalytic effect and remarkable kinetic performance, and the porous properties of graphite It is also beneficial to the adsorption of hydrogen and improves the efficiency of hydrogen absorption; the addition of ternary metal oxides and graphite can effectively eliminate the agglomeration of hydrogen storage materials, thereby achieving the purpose of reducing the particle size of the material. The composition of the invention is reasonable, and the preparation process Simple, low-cost, efficient hydrogen storage performance and remarkable kinetic performance.

2. Compared with the existing single binary metal oxides, the present invention has better kinetic properties, and has good hydrogen absorption and desorption reversibility, and can still show better storage capacity after multiple cycles at a specific temperature. Hydrogen properties.

3. The present invention adopts a magnetic grinding method, which is completed by a magnetic grinding machine. The alternating magnetic field made by the current makes the mixed material rotate around the grinding medium at a high speed and violently at 360 degrees, and achieves a high-speed and perfect grinding effect through severe impact, which is different from the traditional Compared with ball milling, the grinding time can be greatly shortened, thereby improving work efficiency.

Detailed ways

Below in conjunction with embodiment the present invention will be further described.

All raw materials used in the examples are commercially available unless otherwise specified.

Comparative example 1

(1) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 10nm;

(2) Under the protective atmosphere of the inert gas argon, after mixing MgH _with a particle size of 50nm and graphite powder with a particle size of 10nm, the mixed material is added to the grinding tank of the electromagnetic grinder, and the grinding tank is equipped with Magnetic grinding needle, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(3) Set the parameters of the grinding machine, the grinding frequency is set to 1800rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(4) After grinding for 30 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of graphite in the prepared composite hydrogen storage material is 2wt%

Comparative example 2

(1) Mix V ₂ O ₅ and Nb ₂ O ₅ at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize VNbO ₅ with a particle size of 5 μm;

(2) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 10nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 50nm, VNbO ₅ with a particle size of 5μm and graphite powder with a particle size of 10nm, the mixed material is added to the grinding of the electromagnetic grinder In the tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 1800rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(5) After grinding for 30 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percent composition of VNbO in the composite hydrogen storage material made is _5wt %, and the mass percent composition of graphite is 2wt%

Example 1

(1) Mix V ₂ O ₅ and Nb ₂ O ₅ at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize VNbO ₅ with a particle size of 5 μm;

(2) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 10nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 50nm, VNbO ₅ with a particle size of 5μm and graphite powder with a particle size of 10nm, the mixed material is added to the grinding of the electromagnetic grinder In the tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 1800rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(5) After grinding for 30 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of VNbO ₅ in the prepared composite hydrogen storage material is 10 wt%, and the mass percentage of graphite is 2 wt%.

Example 2

(1) Mix V ₂ O ₅ and Nb ₂ O ₅ at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize VNbO ₅ with a particle size of 5 μm;

(2) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 10nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 50nm, VNbO ₅ with a particle size of 5μm and graphite powder with a particle size of 10nm, the mixed material is added to the grinding of the electromagnetic grinder In the tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 1800rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(5) After grinding for 30 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of VNbO ₅ in the prepared composite hydrogen storage material was 15 wt%, and the mass percentage of graphite was 2 wt%.

Example 3

(1) Mix CuO and CoO at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize CuCo ₂ O ₄ with a particle size of 10 μm;

(2) drying the scaly graphite after being ground in an electromagnetic grinder, making a particle diameter of graphite powder of 15nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 50nm, CuCo ₂ O ₄ with a particle size of 10μm and graphite powder with a particle size of 15nm, the mixture is added to the electromagnetic mill In the grinding tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 2500rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(5) After grinding for 20 hours, turn off the grinder, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of CuCo ₂ O ₄ in the prepared composite hydrogen storage material is 10 wt%, and the mass percentage of graphite is 2 wt%.

Example 4

(1) Mix MnO and Fe ₂ O ₃ at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize MnFe ₂ O ₄ with a particle size of 25 μm;

(2) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 20nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 60nm, MnFe ₂ O ₄ with a particle size of 25μm and graphite powder with a particle size of 20nm, add the mixed material to the electromagnetic mill In the grinding tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 3000rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform high-speed 360-degree rotation. High-speed collision grinding with materials;

(5) After grinding for 15 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of MnFe ₂ O ₄ in the prepared composite hydrogen storage material is 12 wt%, and the mass percentage of graphite is 2 wt%.

Example 5

(1) Mix CoO and NiO at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize Co ₂ NiO with a particle size of 45 μm;

(2) drying the scaly graphite after being ground in an electromagnetic mill to make a graphite powder with a particle diameter of 30nm;

(3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 100nm, Co ₂ NiO with a particle size of 45μm and graphite powder with a particle size of 30nm, add the mixed material to the electromagnetic mill In the grinding tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed;

(4) Set the parameters of the grinding machine, the grinding frequency is set to 3600rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials;

(5) After grinding for 3 hours, turn off the grinding machine, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.

The mass percentage of Co ₂ NiO in the prepared composite hydrogen storage material was 15 wt%, and the mass percentage of graphite was 3 wt%.

Performance Testing

The composite hydrogen storage material of Comparative Example 1 without adding ternary metal oxides, and the composite hydrogen storage materials of Comparative Example 2, Example 1 and Example 2 with the addition of ternary metal oxides were tested for the amount of hydrogen released at different temperatures , the test results are shown in Table 1. The hydrogen storage capacity was tested at 160°C and 20bar H ₂ , and the test results are shown in Table 2.

Table 1 Comparative Example 1-2 and Example 1-2 The amount of hydrogen released at different temperatures of the composite hydrogen storage material

Table 2 Comparative Example 1-2 and Example 1-2 Composite hydrogen storage material hydrogen storage capacity

The composite hydrogen storage material prepared in Example 2 was cycled 10-50 times, and the hydrogen storage/discharge capacity was tested at 300°C and 275°C. The test results are shown in Table 3.

Table 3 The hydrogen storage/discharge capacity of the composite hydrogen storage material prepared in Example 2 after 10-50 cycles

Cycles 10 20 30 40 50 Hydrogen storage capacity at 300℃(wt.%) 6 5.8 5.7 5.8 5.8 Hydrogen released at 300℃(wt.%) 5.7 5.6 4.9 5.1 5.5 Hydrogen storage capacity at 275°C (wt.%) 5.2 5.4 5.3 5.2 5.1 Hydrogen released at 275℃(wt.%) 5.2 5.2 4.9 5.1 5.0

Of course, the above content is only a preferred embodiment of the present invention, and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is not limited to the above-mentioned examples, and equal changes and improvements made by those skilled in the art within the essential scope of the present invention shall all belong to the scope covered by the patent of the present invention.

Claims (1)

1. A preparation method of MgH ₂ -ternary metal oxide-graphite composite hydrogen storage material, comprising the following steps: (1) Mix CuO and CoO at a molar ratio of 1:1, grind for 12 hours, and anneal at 500°C to synthesize CuCo ₂ O ₄ with a particle size of 10 μm; (2) drying the scaly graphite after being ground in an electromagnetic grinder, making a particle diameter of graphite powder of 15nm; (3) Under the protective atmosphere of inert gas argon, after mixing MgH ₂ with a particle size of 50nm, CuCo ₂ O ₄ with a particle size of 10μm and graphite powder with a particle size of 15nm, the mixture is added to the electromagnetic mill In the grinding tank, there is a magnetic grinding needle in the grinding tank, the mass ratio of the mixed material to the magnetic grinding needle is 1:20, and the grinding chamber is sealed; (4) Set the parameters of the grinding machine, the grinding frequency is set to 2500rpm, the interval between forward and reverse operation is 0.5h, and then hydrogen gas with a pressure of 10MPa is introduced to turn on the electromagnetic grinder. After power on, the magnetic grinding needle is driven to perform a high-speed 360-degree rotation High-speed collision grinding with materials; (5) After grinding for 20 hours, turn off the grinder, separate the material in the grinding chamber with a magnetic object, and extract the product to obtain a composite hydrogen storage material.