Aluminum alloy for low-temperature hydrogen production and preparation method thereof

Abstract

The application discloses an aluminum alloy for low-temperature hydrogen production and a preparation method thereof. The aluminum alloy can efficiently produce hydrogen in ice water without the addition of expensive and dangerous additives such as lithium hydride (LiH), without the need for a customized solution and without the need for ball milling. The molten alloy is rapidly solidified by liquid nitrogen cooling mold, thereby realizing the rapid activation of the hydrolysis reaction under low-temperature conditions. The cast Al-Ga-In-Sn alloy has good hydrogen production performance, and the reaction yield can reach 100% when reacting with ice water, which can be used for on-line hydrolysis hydrogen supply under low-temperature conditions, has high hydrogen production conversion rate, and has no environmental pollution of reaction products, thereby providing a safe and feasible technical scheme for on-site hydrogen supply, and meeting the hydrogen supply demand of portable hydrogen energy equipment.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production technology by water electrolysis, specifically relating to an aluminum alloy hydrogen production material with high conversion efficiency under low temperature conditions and its preparation method. Background Technology

[0002] Hydrogen energy, due to its pollution-free nature, high calorific value, and good compatibility with fuel cell technology, is considered an important component of the future sustainable energy system. Among numerous application scenarios, on-demand hydrogen supply in low-temperature and even extremely low-temperature environments is particularly noteworthy, such as polar scientific expeditions, high-altitude regions, aerospace, and off-grid combined heat and power (CHP). These scenarios often lack reliable energy infrastructure and require both heating and power generation; therefore, developing technologies that can safely and efficiently produce hydrogen and heat under low-temperature conditions is of great significance.

[0003] Traditional hydrogen storage methods, such as high-pressure gaseous hydrogen storage and cryogenic liquid hydrogen storage, face significant technical and safety challenges in harsh environments. In contrast, the reaction between metals and water can generate hydrogen and heat in situ without external energy input, and is considered a more suitable on-demand energy supply method for extreme environments. Among the metal materials that can be used for hydrogen production by water electrolysis, aluminum has attracted much attention due to its high theoretical hydrogen yield (approximately 1240 mL / g), abundant resources, low cost, and safety. However, a dense and stable oxide film exists on the surface of aluminum, which severely inhibits its reactivity with water, especially below 0 °C, where the oxide film is even more stable, making it difficult to initiate the hydrolysis reaction.

[0004] AO Dudoladov et al. tested the hydrogen production performance of activated aluminum powder in frigid environments. The results showed that the conversion efficiency was less than 2% in high-concentration calcium chloride and zinc chloride salt solutions; and only 17% in potassium hydroxide solution at -40 °C. Furthermore, at this temperature, the reaction induction times in the salt solutions and potassium hydroxide solutions were as long as 80 minutes and 20 minutes, respectively. Liu et al. determined the hydrolysis kinetics and conversion efficiency of Al-31.9%Li alloy in ethanol solutions at -10 °C to -30 °C. This alloy required no induction time and achieved a conversion efficiency exceeding 70%. However, the high lithium content significantly increased the material cost. These studies indicate that the hydrolysis reaction of aluminum with water in frigid environments generally suffers from slow kinetics, low conversion efficiency, and long induction times; even some solutions (such as high-lithium alloys) exhibit excellent performance but are constrained by high costs. Therefore, how to activate the low-temperature hydrolysis activity of aluminum under economically feasible conditions has become an urgent technical challenge.

[0005] Currently, the main pathways to improve the hydrolysis activity of aluminum include alloying, adding inorganic salts, oxides, hydrides, and carbon materials to disrupt the dense oxide film on the aluminum surface. Various additives can synergistically enhance reactivity through different mechanisms. However, when the temperature drops below 0 °C, the aluminum-water reaction still generally exhibits prolonged induction time and decreased conversion efficiency. Theoretically, by controlling the type and content of the active phase, achieving real-time reaction initiation, and fully utilizing the heat of reaction to increase the micro-region temperature, its low-temperature kinetics can be effectively improved. Based on this principle, researchers have attempted to utilize hydride hydrolysis to provide local alkalinity and additional heat. For example, adding NaMgH3 can significantly improve the hydrolysis performance of Al-NaMgH3 materials; after doping with Bi and Li3AlH6, the conversion efficiency can reach 100%. In an ammonium chloride solution at 0 °C, materials containing 30 wt% Ca-Mg-based hydrides can achieve a conversion efficiency of 88%; however, when the temperature drops to -20 °C, the efficiency decreases by about 15 percentage points. This indicates that the hydride-assisted strategy still suffers from performance degradation at very low temperatures. Another strategy involves introducing low-melting-point metal additives (such as gallium, indium, tin, bismuth, and lithium), which enhance the hydrolytic activity of aluminum by disrupting the continuity of the alumina film or forming micropores in the aluminum matrix. Based on this, researchers have developed aluminum alloy / sodium chloride / γ-C3N4 composites and aluminum alloy / sodium chloride / lithium hydride / γ-C3N4 composites. The lithium hydride additive can shorten the induction time of aluminum-based materials in a 23wt% sodium chloride solution at -20 °C from 90 s to 0 s and significantly improve the hydrogen generation rate.

[0006] While the aforementioned methods have achieved low-temperature hydrolysis hydrogen production from aluminum-based materials to some extent, they generally suffer from the following drawbacks: reliance on highly corrosive media such as strong acids / bases, the need for energy-intensive ball milling pretreatment, the use of flammable and explosive metal hydrides, and the requirement for customized formulation of reaction solutions. These problems result in complex preparation processes, high production costs, and poor material storage safety, making it difficult to meet the requirements of simplicity, safety, and low cost in practical applications.

[0007] On the other hand, controlling the grain size of alloys has been proven to be an effective way to influence the hydrogen production performance of aluminum hydrolysis. Wang et al. used a water-cooled copper mold to cast Al-Ga-In-Sn alloys and found that when the grain size decreased from 258 μm to 23 μm, the activation energy of the reaction decreased by about 30%, and the hydrogen production performance was significantly improved. However, this study mainly focused on the influence of grain size on hydrogen production at room temperature and did not systematically explore strategies for achieving low-temperature hydrogen production through alloy hydrolysis by controlling the casting process (especially the mold temperature). In the field of traditional structural aluminum alloy casting, the mold temperature is a key parameter for controlling the cooling rate, which in turn affects the grain size and mechanical properties. However, the hydrogen production field focuses on the hydrogen production performance of hydrolysis rather than mechanical properties, and existing research has not established a direct correlation between mold temperature and low-temperature hydrogen production performance. Therefore, there is an urgent need to develop an aluminum alloy material and its preparation method that is simple to process, requires no additives, strong acids or bases, and no ball milling pretreatment, and can efficiently produce hydrogen in low-temperature (below 0 °C) environments to meet the practical needs of extreme cold regions, emergency hydrogen supply, and mobile energy scenarios. Summary of the Invention

[0008] This paper aims to invent an Al-Ga-In-Sn alloy with rapid hydrogen production at low temperatures and proposes a method for preparing this alloy.

[0009] To achieve the above objectives, the preparation method of the hydrogen production alloy is as follows:

[0010] Step 1: Polish the pure aluminum to remove the surface oxide layer and weigh it. Simultaneously, weigh a certain mass of three low-melting-point metals (Ga, In, and Sn) and place them together with the pure aluminum in a crucible. The aluminum content is 85 wt%, and the total content of the low-melting-point metals gallium, indium, and tin is 15 wt%, with an indium to tin mass ratio of 1.5:1. Specifically, the gallium content varies from 10-14 wt%, the indium content from 0.6-3 wt%, and the tin content from 0.4-2 wt%.

[0011] Step 2: Place the crucible containing the metal in a box-type atmosphere stirring furnace, and fill the furnace with inert gas (nitrogen, argon, etc.) by evacuation and ventilation. Heat the metal to a molten state at a temperature range of 800-850 °C and hold it at that temperature for at least 0.5 h.

[0012] Step 3: After the heat treatment is completed, stir the molten metal for 10-15 minutes to ensure the uniform distribution of each element. Then, pour the molten metal into a pre-treated cryogenic mold with residual liquid nitrogen for casting (a. the mold is cooled in liquid nitrogen for 10-15 minutes, b. the cooling time in a custom mold is 10-30 minutes, which can obtain a mold in the range of -30 °C to -196 °C; the amount of residual liquid nitrogen in the mold accounts for 1 / 10 to 1 / 2 of the mold volume). After the prepared alloy returns to room temperature, seal and store it.

[0013] Step 4: Take a certain mass of the above alloy and put it into the hydrogen production device. Pour ice water into the bottle at a flow rate of 1.2-1.8 mL / min and collect the hydrogen gas generated by the reaction.

[0014] Furthermore, the average hydrogen production rate was calculated based on hydrogen production data corresponding to the range of 10% to 90% of the maximum hydrogen production.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0016] (1) This invention employs two methods to process the mold: a. The mold is directly immersed in liquid nitrogen until temperature equilibrium is reached; b. The mold is placed in a custom-made cooling mold for different times to achieve different temperatures. By utilizing the ultra-low temperature characteristics of liquid nitrogen, the aluminum alloy melt achieves an extremely high cooling rate, the grain size is significantly refined, and the number of grain boundaries is greatly increased, making it easier for the aluminum alloy to initiate the hydrolysis and hydrogen production reaction under low temperature conditions. This overcomes the defect of existing technologies that require a long induction time due to the obstruction of the aluminum surface oxide film.

[0017] (2) The aluminum alloy of the present invention exhibits excellent hydrogen production performance in low-temperature aqueous solution (0 °C). Compared with traditional cast alloys, the present invention significantly shortens the low-temperature hydrogen production induction time to only 6-12 s, eliminating the delayed phenomenon of low-temperature hydrogen production and realizing instantaneous hydrogen production under low-temperature conditions. At the same time, it significantly improves the hydrogen production rate and hydrogen production conversion rate at low temperatures, with a hydrogen production conversion rate of over 99% and an average hydrogen production rate of 482-2121 mL·min. -1 ·g -1 This technology meets the rapid hydrogen supply requirements of hydrogen fuel cells in low-temperature environments, expands the applicable temperature range for hydrogen production by aluminum alloy hydrolysis, and enables aluminum alloys to effectively produce hydrogen in a wide range of temperatures, including near freezing point and even below zero. This provides a reliable technical solution for the use of hydrogen energy equipment in extremely cold regions and low-temperature environments.

[0018] (3) The present invention can achieve rapid solidification of alloy by simply cooling the casting mold, without the need for a complicated ball milling process. The process is simple and easy to implement, and it is easy to mass-produce in the industrial sector. The prepared aluminum alloy is easy to transport and store, and can be used immediately. It overcomes the safety hazards and cost problems of traditional high-pressure hydrogen storage and liquid hydrogen storage. Attached Figure Description

[0019] Figure 1 The X-ray diffraction patterns of the Al-Ga-In-Sn alloys in Examples 1-3 are shown below.

[0020] Figure 2 (ac) are scanning electron microscope images of the Al-Ga-In-Sn alloys of Examples 1-3, respectively;

[0021] Figure 3 This is a scanning electron microscope image of the corrosion of the Al-Ga-In-Sn alloy sample from Example 2;

[0022] Figure 4 The diagram shows the low-temperature hydrogen production of the alloys under pretreatment 1 in Examples 1-3;

[0023] Figure 5 The diagram shows the low-temperature hydrogen production of the alloys under pretreatment 2 in Examples 1-3;

[0024] Figure 6 The graph shows the average hydrogen production rate of Examples 1-3. Detailed Implementation

[0025] The present invention will be described in detail below with reference to the embodiments.

[0026] Weigh Al, Ga, In, and Sn according to Table 1. Place the weighed metal raw materials in an alumina crucible, then place it in a box-type atmosphere stirred furnace. After filling the furnace with nitrogen, heat the furnace to 800 °C at a heating rate of 11 °C / min, and then hold it at this temperature for 1 hour to ensure that all metal and alloy raw materials are in a molten state. After holding at this temperature, stir the molten alloy for 10 minutes, and finally pour the alloy into a mold pre-cooled by liquid nitrogen. After the alloy returns to room temperature, seal and store it.

[0027] (1) The alloy composition is shown in Table 1.

[0028] Table 1. Composition of Al-Ga-In-Sn Quaternary Alloy

[0029] Example 1 85 10 3 2 Example 2 85 11 2.4 1.6 Example 3 85 12 1.8 1.2

[0030] (2) Phase characterization

[0031] The X-ray diffraction patterns of the prepared alloys (Examples 1-3) are attached. Figure 1 As shown, the scanning electron microscope images are attached. Figure 2 (ac) and appendix Figure 3 As shown in (ab);

[0032] from Figure 1 The XRD patterns show that characteristic peaks of Al(Ga) solid solution were detected in samples of Examples 1-3, and characteristic peaks of In3Sn were detected in Examples 1 and 2 with In contents of 3% and 2.4%, respectively, indicating that In and Sn underwent a eutectic reaction during solidification, and this phase has a β-In3Sn type structure. Figure 2 (ac) It can be seen that the addition of Ga, In, and Sn resulted in a large number of defects inside the alloy, including fissures and cracks, as well as granular second phases dispersed in the matrix. Furthermore, the liquid nitrogen remaining in the mold rapidly vaporized during the casting process, and the resulting gas failed to escape from the melt in time, thus forming porosity defects inside the alloy ingot. Figure 3 (a) and (b) show equiaxed crystals with an average grain size of about 10 μm, which is due to the rapid solidification effect brought about by liquid nitrogen quenching.

[0033] (3) Hydrogen production performance

[0034] To simulate a low-temperature environment, two pretreatment methods were used for the samples: (1) Liquid nitrogen treatment (-196 °C): 0.34 g of the alloy was weighed and placed in liquid nitrogen for 1 min. (2) Refrigeration treatment (-16 °C): 0.34 g of the alloy was weighed and placed in a refrigerator for 10 min. As shown in Table 1, the hydrogen production efficiency of the alloy in Example 2 using pretreatment 1 reached 100%, and the hydrogen production rate reached 2121.79 mL·min. -1 ·g -1 The hydrogen production efficiency and rate of the alloy under pretreatment 2 are lower than those under pretreatment 1, but the reaction starts faster and reacts instantly upon contact with ice water.

[0035] Table 1 Hydrogen production performance of Examples 1-3 under pretreatment method 1

[0036] Example 1 99.77 882.59 Example 2 100.00 2121.79 Example 3 96.67 1202.17

[0037] Table 2 Hydrogen production performance of Examples 1-3 under pretreatment method 2

[0038] Example 1 99.36 769.05 Example 2 97.53 732.46 Example 3 83.33 482.53

Claims

1. An aluminum alloy for low-temperature hydrogen production, characterized in that: The molten alloy is rapidly solidified by cooling the mold with liquid nitrogen, and the alloy, after pre-cooling treatment, can react rapidly with ice water. The aluminum alloy comprises 85-95 wt% aluminum, 5-14 wt% gallium, 0.6-5 wt% indium, and 0.4-5 wt% tin. The aluminum alloy is prepared through the following steps: (1) Weigh each raw material into a container according to the proportion, and place the container in an atmosphere resistance furnace under nitrogen protection. The heating rate is 10-15 °C / min, and the termination temperature is set to 800-850 °C. After keeping the molten alloy liquid in the furnace at a temperature of 0.5 h, stir it with a mechanical paddle for 10-15 min. (2) Cool the mold; (3) The stirred alloy liquid is quickly poured into the mold and solidified. After the prepared alloy returns to room temperature, it is sealed and stored.

2. The aluminum alloy according to claim 1, characterized in that: In step (1), the alloy melting time is 1-2 h, the stirring time is 5-15 min, and the stirring rate is controlled within 100 r / min.

3. The aluminum alloy according to claim 1, characterized in that: In step (2), the cooling process can be any of the following: a. Immerse the mold directly in liquid nitrogen until the temperature reaches equilibrium. The cooling time of the mold in liquid nitrogen is 10-15 minutes. b. Place the mold in a custom cooling mold for cooling. The cooling time in the custom mold is 10-30 minutes, which can produce a mold in the range of -30 °C to -196 °C. Both cooling methods leave a small amount of liquid nitrogen in the mold, which accounts for 1 / 10 to 1 / 2 of the mold's volume.

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