WO2024000963A1

WO2024000963A1 - Aluminum/carbon composite for hydrogen production by means of reaction with alkaline water, and preparation method therefor and use thereof

Info

Publication number: WO2024000963A1
Application number: PCT/CN2022/128472
Authority: WO
Inventors: 王平; 玄登晖
Original assignee: 华南理工大学
Priority date: 2022-06-28
Filing date: 2022-10-30
Publication date: 2024-01-04
Also published as: CN115057409B; CN115057409A

Abstract

Disclosed in the present invention are an aluminum/carbon composite for hydrogen production by means of reaction with alkaline water, and a preparation method therefor and the use thereof. The aluminum/carbon composite is composed of an aluminum matrix and a carbon material, wherein the carbon material is dispersively distributed on the surface and inside the aluminum matrix in the form of submicron or nanoscale particles, thereby forming a continuous or quasi-continuous network. In the present invention, by subjecting a carbon material to a heat treatment in a protective atmosphere and carrying out ball milling, in a protective atmosphere, on an aluminum powder and the carbon material, which has been subjected to the heat treatment, an aluminum/carbon composite for hydrogen production by means of reaction with alkaline water is prepared. In the preparation method provided in the present invention, the raw materials are easy to obtain, the operation is simple, and mass production is facilitated, such that the hydrogen production dynamics of an aluminum-water system can be significantly improved, a rapid reaction with alkaline water can be carried out in a room-temperature environment to produce hydrogen, and the highest hydrogen production rate thereof is located at the top level in the current reports.

Description

An aluminum/carbon composite that reacts with alkaline water to produce hydrogen and its preparation method and application

Technical field

The invention belongs to the technical field of hydrogen production materials, and specifically relates to an aluminum/carbon composite that reacts with alkaline water to produce hydrogen and its preparation method and application.

Background technique

Hydrogen is a clean and efficient energy carrier. Its large-scale industrial application is expected to fundamentally solve global problems such as energy shortage and environmental pollution. However, safe and efficient storage and transportation of hydrogen are still huge challenges facing the widespread application of hydrogen energy technology. challenge. Since around 2000, the use of hydrogen-rich materials/systems combined with spent fuel regeneration to produce hydrogen on demand has become a chemical hydrogen storage method for mobile or portable devices. Among the many candidate materials/systems, the aluminum-water system has attracted much attention due to its abundant resources, low reaction temperature, the generated hydrogen does not require purification, and the mature aluminum recycling technology.

However, the formation of a continuous dense passivation layer on the aluminum surface restricts the application potential of the aluminum-water system as a hydrogen source. To address this problem, a variety of modification methods have been developed at home and abroad, but none of them can meet the performance and performance of hydrogen production in practical applications. cost requirements. Adding high-concentration alkaline additives, such as sodium hydroxide, potassium hydroxide, etc., can react with alumina and aluminum to form soluble metaaluminates, thereby effectively destroying the formation of the passivation layer, but high alkali concentrations It is easy to cause stress corrosion of the container, which imposes strict corrosion resistance requirements on the hydrogen generator. The use of low melting point metals such as gallium, indium, tin, and bismuth to alloy aluminum can achieve rapid hydrogen production performance in neutral water by weakening the strength of the matrix and changing the density of the passivation film (Studies on microstructure of activated aluminum and its hydrogen generation properties in aluminum/water reaction); however, the sharp increase in material and modification costs limits the practical application of this type of aluminum-based alloy. In addition, ball milling of aluminum with metal oxides such as Al2O3 and MgO or water-soluble inorganic salts such as NaCl and KCl can also improve its reactivity in neutral water. However, according to published literature, after long-term ball milling, the oxide /Salt has a rather limited effect on improving the reaction kinetics of the aluminum-water system. Therefore, it is still urgent to explore advanced methods to solve the passivation problem of aluminum-water systems without excessively increasing the preparation cost.

In view of this situation, the present invention proposes a method of using carbon materials as modifiers to compound with aluminum, thereby improving its hydrogen production performance in alkaline water.

Technical solutions

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an aluminum/carbon composite suitable for mobile equipment that reacts with alkaline water to produce hydrogen and its preparation method and application (hydrogen production method of water reaction hydrogen production system ). The preparation method has readily available raw materials, simple operation, and is convenient for mass production. The modified aluminum-based composite has excellent hydrogen production performance at low alkali concentration, and can solve the problems of high preparation cost and hydrogen production rate in the existing technology. Low question.

The invention adopts a hydrogen production system and a hydrogen production method by reacting an aluminum/carbon composite with alkaline water. The hydrogen production system consists of a solid composite and an alkaline liquid. The weight ratio of the solid composite and the alkaline liquid is 1:5. ~1:1000; among them, the solid composite is an aluminum/carbon material composite. The aluminum/carbon composite is prepared by mechanical ball milling. The carbon is finely dispersed in the interior and surface of the aluminum matrix at micro-nano scale. The composite has super affinity. Water-based, good antioxidant properties.

The object of the present invention is achieved through the following technical solutions.

An aluminum/carbon composite that reacts with alkaline water to produce hydrogen. The aluminum/carbon composite is composed of an aluminum matrix and a carbon material; the carbon material is dispersed and distributed on the surface of the aluminum matrix in the form of submicron or nanoscale particles. and internally, forming a continuous or quasi-continuous network. The aluminum/carbon composite exhibits super hydrophilicity and good oxidation resistance.

Preferably, the purity of the aluminum matrix is above 99%, and the carbon material is one or a combination of one or more of carbon nanotubes, graphene, activated carbon, carbon fiber, graphite powder or conductive carbon black.

Preferably, the aluminum/carbon composite has a porous structure with a pore size of 100 nm to 10 μm.

The above-mentioned preparation method of the aluminum/carbon composite for reacting with alkaline water to produce hydrogen includes the following steps:

(1) Heat-treat the carbon material under a protective atmosphere; remove adsorbed impurity gases and moisture; after heat treatment, the carbon material will have two phase structures: graphite carbon and amorphous carbon;

(2) Ball-mill the aluminum powder and the carbon material heat-treated in step (1) under a protective atmosphere to prepare an aluminum/carbon composite that reacts with alkaline water to produce hydrogen.

Preferably, the protective atmosphere in step (1) is argon.

Preferably, the heat treatment temperature in step (1) is 200-550°C, the time is 1-10 hours, and the heating rate is 10°C/min.

Preferably, the carbon material in step (1) is one or a combination of one or more of carbon nanotubes, graphene, activated carbon, carbon fiber, graphite powder or conductive carbon black.

Preferably, the mass ratio of the aluminum powder and the heat-treated carbon material in step (2) is 1:1~100:1.

Further preferably, the mass ratio of the aluminum powder and the heat-treated carbon material in step (2) is 1:1~95:5.

Preferably, the particle size of the aluminum powder in step (2) is 1 to 1000 μm.

Further preferably, the particle size of the aluminum powder in step (2) is 10~200 μm; the purity is 99.9%.

Preferably, the diameter of the grinding ball used in the ball milling in step (2) is 5 mm-15 mm; the ball-to-material mass ratio of the grinding ball is 5:1~100:1.

Further preferably, the diameter of the grinding balls used in the ball milling in step (2) is 5, 10, or 15 mm;

Preferably, the ball milling speed in step (2) is 100 to 2000 rpm, and the ball milling time is 1 minute to 50 hours.

Preferably, the grinding jar and grinding balls of the ball mill in step (2) are agate, zirconia, cemented carbide, polyurethane or stainless steel; the protective atmosphere is argon.

The application of the above-mentioned aluminum/carbon composite that reacts with alkaline water to produce hydrogen is used in reacting with alkaline water to produce hydrogen.

Preferably, the alkali in the alkaline water is one or a combination of sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) ₂ ) or lithium hydroxide (LiOH). , the concentration of alkali is 0.1~10 M.

Further preferably, the concentration of the base is 0.5~5 M.

Preferably, the weight ratio of the aluminum/carbon composite and alkaline water is 1:5~1:1000.

Preferably, the hydrogen production reaction is carried out in a room temperature environment; the system temperature is not controlled during the hydrogen production reaction.

The design principle of the present invention is:

For the aluminum-water reaction hydrogen production modification method, the key point is to have fast hydrogen production kinetics in a relatively mild solution without excessive modification costs. Previous studies often only considered the former and ignored the cost issue. However, the aluminum/carbon composite provided by the present invention simultaneously solves these two problems to a certain extent. First, the aluminum powder and carbon material are mechanically ball milled under the protection of an argon atmosphere. In this process, the carbon material not only acts as a modifier, but also acts as a grinding aid to prevent the aluminum powder from adhering to each other due to cold welding during the ball milling process. ; In addition, the carbon material is fully in contact with the aluminum matrix, which also creates a large number of interfaces, giving the aluminum/carbon composite a fluffy structure, providing a channel for moisture diffusion in the capillary effect, thereby increasing the contact area for the reaction. When exposed to an alkali solution, the passivation film on the aluminum surface is destroyed and the following reaction occurs (1):

Al ₂ O ₃ + 3H ₂ O + 2OH ^- → 2[Al(OH) ₄ ] ^- (1)

The alkaline aqueous solution that then penetrates into the aluminum/carbon composite contacts the aluminum matrix and reacts (2)

2Al + 6H ₂ O + 2OH ^- → 2[Al(OH) ₄ ] ^- + 3H ₂ ↑ (2)

beneficial effects

The advantages and beneficial effects of the present invention are:

(1) The present invention provides a modified new method suitable for hydrogen production from aluminum/water. The key difference between this method and the traditional method is that the method is simple, easy to implement, fast and can be mass-produced. It significantly provides hydrogen production power. While learning, it also has low modification cost. The physical mixing ability of the mechanical ball milling method is used to evenly distribute the carbon material on the surface and interior of the aluminum matrix, providing a large interface area and creating a channel for moisture diffusion, which is conducive to increasing the contact area of the reaction; in addition, by regulating the carbon material The proportion and ball milling time further strengthen the interaction between carbon and aluminum matrix, further improving the hydrogen production performance of the aluminum/carbon composite.

(2) The aluminum/carbon composite material provided by the present invention and suitable for instant hydrogen production by mobile equipment uses cheap and easily available raw materials, has a simple preparation process, is pollution-free in the entire process, and is convenient for mass production.

(3) The present invention provides an aluminum/carbon material-water composite system with high hydrogen production performance, which can achieve rapid hydrogen production kinetics at low alkali concentrations and has excellent oxidation resistance. The comprehensive hydrogen production performance is currently at the top. level.

Description of the drawings

Figure 1a is a scanning electron microscope and the corresponding energy spectrum of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes: Al: carbon material = 5.

Figure 1b is a scanning electron microscope and the corresponding energy spectrum of the aluminum/carbon composite prepared in Example 1 after reacting in an alkali solution for 10 seconds.

Figure 2a is a high-leg annular dark field transmission electron microscope and the corresponding energy spectrum analysis chart of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes with Al:carbon material = 5.

Figure 2b is a transmission electron microscope and electron diffraction picture of the corresponding area of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes with Al:carbon material = 5.

Figure 2c is a high-resolution transmission electron microscope result of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes with Al:carbon material = 5.

Figure 3 is the XRD pattern of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes with Al:carbon material = 5.

Figure 4 is the Raman spectrum of the aluminum/carbon composite prepared in Example 1 after ball milling for 15 minutes with Al:carbon material = 5.

Figure 5a is a hydrogen production kinetic curve of the aluminum/carbon composite prepared in Example 1 and pure aluminum powder in an alkaline solution.

Figure 5b is a hydrogen production rate curve over time of the aluminum/carbon composite prepared in Example 1 and pure aluminum powder in an alkaline solution.

Figure 6a is the hydrogen production kinetic curve of the aluminum/carbon composite prepared in Example 2 with different ball milling times of Al: carbon material = 5 in an alkaline solution.

Figure 6b shows the hydrogen production rate curve of the aluminum/carbon composite prepared in Example 2 with different ball milling times of Al: carbon material = 5 in an alkaline solution as a function of time.

Figure 7a is a scanning electron microscope and corresponding energy spectrum analysis chart of the aluminum/carbon composite of Al: carbon material = 5 that was ball-milled for 10 minutes prepared in Example 2.

Figure 7b is a scanning electron microscope and corresponding energy spectrum analysis chart of the aluminum/carbon composite of Al: carbon material = 5 that was ball-milled for 20 minutes prepared in Example 2.

Figure 7c is a scanning electron microscope and corresponding energy spectrum analysis chart of the aluminum/carbon composite of Al: carbon material = 5 that was ball-milled for 1 hour prepared in Example 2.

Figure 8a is a kinetic curve of hydrogen production in an alkaline solution as the proportion of carbon material decreases in the ball-milled aluminum/carbon composite prepared in Example 3 for 15 minutes.

Figure 8b is a hydrogen production rate curve as time changes in an alkali solution as the proportion of carbon material decreases in the aluminum/carbon composite prepared in Example 3 after ball milling for 15 minutes.

Figure 9a shows the hydrogen production kinetic curve of the aluminum/carbon composite prepared in Example 4 after ball milling for 15 minutes with Al:carbon material = 5 as the time left in the air increases in an alkali solution.

Figure 9b shows the hydrogen production rate curve of the aluminum/carbon composite prepared in Example 4 that was ball-milled for 15 minutes with Al:carbon material = 5 and placed in the air for longer in an alkaline solution.

Figure 10a is a graph showing the change of the contact angle with time on the surface of the aluminum powder compact prepared in Example 5.

Figure 10b is a graph showing the change of contact angle with time on the surface of the Al/carbon composite tablet prepared in Example 5.

Embodiments of the invention

The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be pointed out that any process that is not specifically described in detail below can be implemented or understood by those skilled in the art with reference to the existing technology. If the manufacturer of the reagents or instruments used is not indicated, they are regarded as conventional products that can be purchased commercially.

实施例Example 11

Synthesis, structure and hydrogen production performance of Al/carbon composites

Al/carbon composite preparation

Select the carbon material (activated carbon) to be used and heat it to 400°C under an argon atmosphere. ℃, the heating rate is 10 ℃/min, and after 3 hours of constant temperature treatment, it is cooled to room temperature in the furnace. Then, put aluminum powder with a particle size of 25 μm, heat-treated carbon materials and grinding balls (5mm, 10mm, and 15mm grinding balls are mixed at a mass ratio of 5:2:1) into the glove box at a mass ratio of 1:30. In the ball milling tank, the mass ratio of aluminum powder to carbon material is 5:1, and the ball is milled at 1000 rpm for 15 minutes to obtain the target aluminum/carbon composite.

Phase/structural characterization of aluminum/carbon composites:

Scanning electron microscopy observation and corresponding energy spectrum analysis (Figure 1a and Figure 1b) found that after mechanical ball milling, a large number of carbon particles of different sizes were embedded in the aluminum matrix. However, the sample was observed again after 10 seconds of reaction and carbon particles were found. A large amount of chips fell off the aluminum base, and pits formed by de-embedding appeared on the aluminum base.

High-leg annular dark field transmission electron microscopy observation and corresponding energy spectrum analysis (Figure 2a) further confirmed the uniform composite of aluminum and carbon at the submicron to nanometer scale, and the carbon material formed a continuous or quasi-continuous network in the aluminum matrix. Electron diffraction (Figure 2b) was selected to confirm the diffraction ring of aluminum, and high-resolution transmission electron microscopy (Figure 2c) observed the characteristic amorphous carbon morphology in carbon materials.

XRD analysis (Figure 3) shows clearly identified sharp diffraction peaks of aluminum and corresponding amorphous peaks of carbon materials.

The D and G peaks and I _D /I _G =1.06 appearing in the Raman spectrum (Figure 4) also prove the existence of carbon materials with amorphous carbon as the main component phase.

Hydrogen production method:

Place 1 g of aluminum/carbon composite into a two-necked flask at room temperature (25°C), and inject 100 mL of 1 M NaOH solution into the two-necked flask through a constant pressure funnel. The system temperature is not controlled during the reaction. (Using aluminum powder as a comparative experiment)

Hydrogen production performance test:

The generated hydrogen is cooled to room temperature through the condenser tube, and then collected in a gas collection bottle. The amount of hydrogen produced is measured by the drainage method, and the hydrogen production volume-time curve is measured. The measured hydrogen production volume is differentiated with time to obtain Hydrogen production rate-time curve.

Figure 5a and Figure 5b show the hydrogen production performance (including hydrogen production amount-time curve and hydrogen production rate-time curve) of aluminum/carbon composite and unmodified aluminum powder in alkaline solution. The test results show that: It takes 8 minutes for the modified aluminum powder to achieve complete hydrogen production, and the maximum hydrogen production rate is only 251 mL min ^-1 g ^-1 ; while the modified aluminum/carbon composite can achieve complete hydrogen production within 1 minute. , the maximum hydrogen production rate reaches 4556 mL min ^-1 g ^-1 (based on the mass of aluminum/carbon composite), which is 18 times that of unmodified aluminum powder.

Performance test results show that after the aluminum powder and carbon materials are modified by mechanical ball milling, the hydrogen production kinetics in a low alkali concentration environment has been significantly improved.

实施例Example 22

The effect of ball milling time on the hydrogen production performance of aluminum/carbon material composites, and the changes in the microstructure of aluminum/carbon material composites with ball milling time.

The preparation of the Al/carbon composite was the same as in Example 1, the only difference being that the ball milling time was different.

The hydrogen production method and hydrogen production performance test method are the same as in Example 1.

Figure 6a and Figure 6b show the comparison of hydrogen production performance of aluminum/carbon material composites in alkaline solution with different ball milling times. The results show that the hydrogen production kinetics of the aluminum/carbon material composite increases as the ball milling time increases, reaching a maximum at 15 minutes; when the ball milling time continues to be extended, the hydrogen production kinetics decrease.

Morphological characterization of aluminum/carbon composites at different ball milling times

According to scanning electron microscopy combined with energy spectroscopy analysis (Figure 7a, Figure 7b and Figure 7c), it was found that the carbon particles gradually fragmented as the ball milling time increased and were embedded in the aluminum matrix, preventing the formation of a passivation film on the aluminum surface and at the same time providing water Windows and diffusion channels are provided for molecules to enter the interior of the aluminum matrix; however, due to the good plasticity and deformation ability of pure aluminum, the carbon particles are quickly coated inside the matrix during the process of welding and adhering the aluminum to each other. (The carbon signal in the energy spectrum gradually weakens or even disappears)

实施例Example 33

Effect of carbon material ratio on hydrogen production performance of aluminum/carbon composites.

The preparation of the Al/carbon composite is the same as in Example 1, except that the mass ratio of aluminum powder to carbon material is different.

Figure 8a and Figure 8b show the law of the hydrogen production performance curve (including hydrogen production amount-time curve and hydrogen production rate-time curve) when the proportion of carbon material in the aluminum/carbon composite in the alkaline solution continues to decrease: as the carbon material The proportion of carbon materials gradually decreases, and the hydrogen production kinetics gradually deteriorates, indicating that the higher the proportion of carbon materials, the better the modification effect on the aluminum matrix.

实施例Example 44

Effect of exposure to air on hydrogen production performance of aluminum/carbon composites.

The Al/carbon composite preparation was the same as in Example 1.

Figure 9a and Figure 9b show the changes in hydrogen production performance of the aluminum/carbon composite with Al:carbon material = 5 in alkaline solution as the time left in the air increases (including hydrogen production amount-time curve and hydrogen production rate -time curve). The hydrogen production kinetics slowed down with the extension of storage time, and the maximum hydrogen production rate also decreased. However, after the storage time reached 12 hours, the hydrogen production kinetics and the maximum hydrogen production rate remained stable, and the sample still showed good performance. The hydrogen production performance shows that the sample has certain antioxidant properties.

实施例Example 55

Hydrophilicity test of Al/carbon composites

The Al/carbon composite preparation was the same as in Example 1.

Use a tablet press to press the same quality of untreated aluminum powder and Al/carbon composite into circular tablets with a diameter of 10 mm and a thickness of 1 mm, and conduct surface contact angle tests.

Figure 10a and Figure 10b show the surface contact angle changes with time of aluminum powder tablets and Al/carbon composite tablets. The surface contact angle of aluminum powder tablets is stable at 93°, showing hydrophobic characteristics; while water droplets After contacting the Al/carbon composite tablet, it is quickly absorbed and disappears within 0.05 seconds, showing super hydrophilicity.

The results of the examples show that the present invention adopts a modification method of mechanical ball milling of aluminum powder and carbon materials to promote hydrogen production from aluminum-water, which can solve the problems of low hydrogen production rate and high modification cost in the prior art. The hydrogen system and hydrogen production method have the technical advantages of simple process, high efficiency, safety and low hydrogen production cost, and can provide a mobile hydrogen source for fuel cells of mobile or portable equipment.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, etc. may be made without departing from the spirit and principles of the present invention. All simplifications should be equivalent substitutions, and are all included in the protection scope of the present invention.

Claims

An aluminum/carbon composite that reacts with alkaline water to produce hydrogen, characterized in that the aluminum/carbon composite is composed of an aluminum matrix and a carbon material; the carbon material is dispersed in the form of submicron or nanoscale particles. On the surface and inside of the aluminum matrix, a continuous or quasi-continuous network is formed.
The aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 1, wherein the purity of the aluminum matrix is more than 99%, and the carbon material is carbon nanotubes, graphene, activated carbon, carbon fiber, One or a combination of graphite powder or conductive carbon black.
The preparation method of an aluminum/carbon composite for reacting with alkaline water to produce hydrogen according to claim 1 or 2, characterized in that it includes the following steps:

(1) Heat treatment of carbon materials in a protective atmosphere;

(2) Ball-mill the aluminum powder and the carbon material heat-treated in step (1) under a protective atmosphere to prepare an aluminum/carbon composite that reacts with alkaline water to produce hydrogen.
The method for preparing an aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 3, characterized in that: the protective atmosphere in step (1) is argon; the temperature of the heat treatment is 200~550 ℃, time is 1~10 hours.
The method for preparing an aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 3, characterized in that: the mass ratio of the aluminum powder in step (2) to the heat-treated carbon material is 1:1~ 100:1; the particle size of the aluminum powder is 1~1000 μm.
The method for preparing an aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 3, characterized in that: the diameter of the grinding ball used in the ball milling in step (2) is 5 mm-15 mm; The ball-to-material mass ratio of the grinding ball is 5:1~100:1;

The rotation speed of the ball mill is 100 to 2000 rpm, and the ball milling time is 1 minute to 50 hours.
The method for preparing an aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 3, characterized in that: the grinding jar and the grinding ball of the ball mill in step (2) are agate, zirconia, cemented carbide , polyurethane or stainless steel; the protective atmosphere is argon.
Application of the aluminum/carbon composite that reacts with alkaline water to produce hydrogen according to claim 1 or 2 in reacting with alkaline water to produce hydrogen.
The application according to claim 8, characterized in that: the alkali in the alkaline water is one or more combinations of sodium hydroxide, potassium hydroxide, calcium hydroxide or lithium hydroxide, and the concentration of the alkali is 0.1 ~10M;

The weight ratio of the aluminum/carbon composite and alkaline water is 1:5~1:1000.
The application according to claim 8, characterized in that: the hydrogen production reaction is carried out in a room temperature environment; the system temperature is not controlled during the hydrogen production reaction.