Silicon-based solid high-density hydrogen storage material, synthesis method, and method for hydrogen adsorption on silicon

Abstract

The application discloses a silicon-based solid high-density hydrogen storage material, a synthesis method and a hydrogen adsorption silicon method, wherein the synthesis method of the silicon-based solid high-density hydrogen storage material comprises the following steps: taking silicon chip cutting discarded silicon dust powder / silicon mud as a basic raw material, and obtaining silicon micro powder with nanometer size after cleaning and drying; the purity of the silicon micro powder is set to be 4.8N or more, the size is 50-200nm, and D50=80-130nm; the silicon micro powder is synthesized with calcium metal to form layered calcium silicide, specifically, the silicon micro powder is synthesized with calcium micro powder to form layered calcium silicide, then calcium ions existing between the layered calcium silicide layers are removed, and layered siliconene is obtained, and the density of the layered siliconene is 1.5g / cm 3 The silicon-based solid high-density hydrogen storage material, the synthesis method and the hydrogen adsorption silicon method provided by the application modify the basic crystal lattice structure of silicon material into a layered stacked siliconene structure, form a quasi-two-dimensional substance arranged in a honeycomb lattice plane, and have a wave mesoscopic / microscopic structure, and a large amount of hydrogen atoms can be adsorbed between the layers.

Description

Technical Field

[0001] This invention relates to the field of silicon-based solid-state hydrogen storage technology, and more particularly to silicon-based solid-state high-density hydrogen storage materials, synthesis methods, and methods for hydrogen adsorption on silicon. Background Technology

[0002] For nearly 300 years, human research and development on the application of hydrogen has continued, yet large-scale commercialization has not yet achieved safe, low-cost, and convenient practical applications of green hydrogen. Silicon accounts for 28% of the elements in nature, is chemically stable and safe, and has been widely used in human production and daily life. However, because hydrogen molecules are difficult to adsorb onto the surface of silicon materials, practical methods for using high concentrations of silicon to adsorb hydrogen have not yet been industrialized.

[0003] The main reasons why silicon, as a stable compound or monomeric substance that exists in nature, is difficult to adsorb hydrogen atoms are as follows:

[0004] 1. Influence of crystal structure: The crystal structure of silicon is diamond, which is different from the crystal structure of metals. The interatomic gaps in silicon are small, making it difficult for hydrogen atoms to enter. It also does not have a crystal structure similar to that of metal hydrides, which is not conducive to silicon's hydrogen storage.

[0005] 2. Binding with hydrogen: To achieve hydrogen storage with silicon, covalent bonds must be formed between them, which creates a significant obstacle to the adsorption / release cycle. Hydrogen storage metals or alloys have suitable chemical bonds that facilitate adsorption / release cycles, while silicon forms a strong bond with hydrogen, making hydrogen release very difficult.

[0006] 3. Difficulty in forming hydrogen compounds: Some metals react with hydrogen to form metal hydrides, which form stable hydrogen-adsorbed substances. However, silicon is difficult to combine with hydrogen and cannot form stable hydrides, which greatly limits the possibility of silicon as a hydrogen storage material. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is that existing silicon is difficult to adsorb hydrogen atoms. The present invention provides a silicon-based solid-state high-density hydrogen storage material, a synthesis method, and a method for hydrogen adsorption on silicon. The basic lattice structure of silicon is modified into a layered silicene structure, forming a quasi-two-dimensional material with a honeycomb lattice planar arrangement, which has a buckled mesoscopic / microscopic shape and can adsorb a large number of hydrogen atoms between its layers.

[0008] To achieve the above objectives, the present invention provides a method for synthesizing silicon-based solid-state high-density hydrogen storage materials, comprising the following steps:

[0009] Using silicon dust (silicon sludge) discarded during the dicing process of silicon wafers used in the photovoltaic / semiconductor industries as a base material, silicon micropowder with nanoscale dimensions is obtained after cleaning, processing, and drying. The purity of the silicon micropowder is set to be above 4.8N, with a size of 50-200 nm and a D50 of 80-130 nm. The silicon sludge raw material involved in this patent has natural characteristics such as low cost, high purity, and extremely low radioactivity.

[0010] The nano-silicon powder is synthesized with calcium metal to form layered calcium silicide. Specifically, the silicon powder and calcium powder are synthesized into layered calcium silicide, and then calcium ions present between the layers of the layered calcium silicide are removed to obtain layered silane. The density of the layered silane is approximately 1.5 g / cm³. 3 .

[0011] Furthermore, the silicon micro powder is configured to have a silicon content >99.998%, and the radioactive elements U and Th must be <0.001ppbWt, and its shape shown in the micrograph is a quasi-two-dimensional Q2D shape; the calcium micro powder is configured to be a dry white micro powder with a particle size of φ0.5~10μm, and the shape shown in the micrograph is a quasi-spherical or blocky shape.

[0012] Further, the silicon micro powder and the calcium micro powder are thoroughly mixed in a molar weight ratio of 2:1, and then subjected to high temperature and vacuum. After that, argon gas is injected into the cavity to maintain the high temperature and then de-temperature, to obtain a pure white or pure white slightly gray blocky solid CaSi2.

[0013] Further, after stirring and fully reacting the CaSi2 with dilute sulfuric acid or dilute hydrochloric acid at room temperature, Kautsky-type Si6O3H3 with the perhydroxyl group removed is obtained.

[0014] Further, the CaSi2 was stirred with concentrated sulfuric acid at low temperature and reacted fully to obtain Weiss-type siloxane Si6H3(OH)3.

[0015] Furthermore, the CaSi2 is reacted thoroughly with dilute sulfuric acid or dilute hydrochloric acid at a temperature near the freezing point to obtain silicene Si6.

[0016] Furthermore, the purity of the silicon micropowder is set to be 5.0N or higher.

[0017] Furthermore, the silicon micropowder is configured to have a silicon content of ≥99.999%.

[0018] In a preferred embodiment of the present invention, a silicon-based solid-state high-density hydrogen storage material is provided, which is synthesized by the above method and includes Si6 with a silane structure obtained based on Si6H6, Si6O3H3, and Si6H3(OH)3 silane series substances.

[0019] In another preferred embodiment of the present invention, a method for hydrogen adsorption of silicon is provided.

[0020] Specifically, the following steps are included:

[0021] Layered polysiloxane, Weiss-type siloxane, and Kautsky-type siloxane are prepared, and hydrogen is released from the layered polysiloxane. The Weiss-type siloxane and Kautsky-type siloxane are then transformed into layered stacked siloxane at high temperature.

[0022] Hydrogen is adsorbed between the layers of this layered silicene structure, and the low-density, loose lattice structure facilitates the absorption / release of hydrogen atoms and molecules.

[0023] Technical effect

[0024] The silicon-based solid-state high-density hydrogen storage material, its synthesis method, and its method for hydrogen adsorption on silicon provided by this invention have a density of 1.4~1.8 g / cm³ under the conditions of room temperature, dryness, and one atmosphere of pressure. 3 Between; at room temperature, hydrogen storage of 4~9 wt% can be achieved by filling a closed pipe with hydrogen; under room temperature conditions and with the quartz container sealed, the density remains unchanged after repeated heating and cooling, and the shape and color of the hydrogen storage material show almost no change under visual observation and microscopy; after repeated filling / discharging of hydrogen, the filling / discharging data curves of the hydrogen storage material show a slight lag phenomenon (similar to magnetic hysteresis), but the filling / discharging curves basically overlap.

[0025] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0026] Figure 1 These are microscopic images of silica mud after cleaning, showing it as feathery or scaly powder.

[0027] Figure 2 This is a schematic diagram of the crystal structure of silicene, where a) is the Q2D structure of layered silicene, b) is the crystal structure of layered polysilicene Si6H6, c) is the crystal structure of Kautsky-type siloxene Si6O3H3, d) is the crystal structure of Weiss-type siloxene Si6H3(OH)3, e) is the crystal structure of CaSi2, and f) is the XRD measurement results of the crystal structures of CaSi2 and layered silicene.

[0028] Figure 3 This is a simplified flowchart illustrating the preparation process of silicene, a hydrogen storage material.

[0029] Figure 4 A simplified diagram of the MA process for hydrogen storage materials according to an example of the present invention;

[0030] Figure 5 This is a schematic diagram of hydrogen molecules or hydrogen atoms being adsorbed onto layered stacked silene in an embodiment of the present invention: a) The square dashed frames between the layered stacked silene structures represent the positions where hydrogen atoms can be adsorbed; b) The adsorption of hydrogen is simply described as a quasi-parallel plane spatial relationship between the plane of hydrogen adsorption and the silene; c) A schematic diagram of hydrogen atoms or molecules adsorbed onto the quasi-two-dimensional structure of silene.

[0031] Figure 6 In this embodiment of the invention, hydrogen storage catalytic sites are formed using the liquid-phase MA method;

[0032] Figure 7 A simplified schematic diagram of the apparatus used in this experiment;

[0033] Figure 8 These are the measured hydrogen adsorption data results using Sample (A) in this embodiment of the invention;

[0034] Figure 9 These are the measured hydrogen adsorption data results using Sample (B) in this embodiment of the invention;

[0035] Figure 10 These are the measured hydrogen adsorption data results using Sample (C) in this embodiment of the invention;

[0036] Figure 11 These are the measured results of hydrogen release tests in embodiments of the present invention. Detailed Implementation

[0037] Calcium silicide (CaSi2) was prepared as an intermediate medium using high-purity calcium powder and high-purity silicon powder as raw materials, and then ground into powder. Following this process... Figure 3 The process forms layered polysiloxane Si6H6 and siloxane Si6. These two products are then used as raw materials to form the final GP-H hydrogen storage material using the MA method invented in this patent. This patent presents measured data for three types of GP-H hydrogen storage materials, named (A), (B), and (C). The detailed process is described below.

[0038] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0039] In the following description, specific details, such as particular internal procedures and techniques, are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will appreciate that the invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of the invention with unnecessary detail.

[0040] Silicon, with a relatively small atomic weight of 28.085 g / mol, is the second most abundant element in the Earth's crust. If this element could be made into a hydrogen-adsorbing material, it would greatly promote the development of green hydrogen. However, silicon has a crystal structure known as the "diamond structure," making it difficult for hydrogen to be adsorbed into the crystal compared to hydrogen-adsorbing metals with fcc or bcc structures. Transforming this material into one capable of adsorbing hydrogen requires a groundbreaking new material design framework. The atomic shell of Si is [Ne]3S. 2 3P 2 The atomic shell of Ca is [Ar]4S. 2 .

[0041] This invention designs a process using calcium (Ca) as a non-silicon medium that can be completely extracted during the process. Calcium has an abundance of 4.1% in nature, making it a widely available and low-cost raw material, eliminating concerns about raw material scarcity or increased environmental impact.

[0042] This invention provides a method for synthesizing silicon-based solid-state high-density hydrogen storage materials, comprising the following steps:

[0043] Step 1: Using silicon dust / silicon sludge discarded from silicon wafer cutting (semiconductor, photovoltaic, and MEMS wafer slicing are all acceptable) as the base material, after cleaning, processing, and drying, silicon micropowder with nanoscale dimensions is obtained. The purity of the silicon micropowder is set to 4.8N, with an optimal purity of 5N or higher (purity higher than 99.999%), a size of 50–200 nm, and a D50 of 80–130 nm. Extensive basic research and production practice have proven that this silicon micropowder possesses a nanoscale and quasi-two-dimensional (Q2D) particle structure. Figure 1 As shown. Compared to spherical silicon micropowder, this silicon micropowder has a larger specific surface area and is shaped like feathers, scales, and pine needles. The surface of this silicon micropowder retains micro-marks left by mechanical extrusion and chips generated during silicon wafer wire cutting, which further increases its surface area and ability to adhere to other atoms / molecules.

[0044] Step 2 involves synthesizing layered calcium silicide from the processed silicon micropowder and calcium metal. Specifically, this involves synthesizing layered calcium silicide from silicon micropowder and calcium micropowder, then removing calcium ions between the layers of the layered calcium silicide to obtain layered silene. Layered silene exhibits a quasi-two-dimensional network-like stacked hydrogen storage structure (referred to as GP-H hydrogen storage material: Green Perovskite Hydrogen). The density of layered silene is 1.5 g / cm³. 3 This invention constructs a silicon material with a basic lattice structure of silicene, a quasi-two-dimensional material in which silicon atoms are arranged in a honeycomb lattice planar pattern, exhibiting a buckled mesoscopic / microscopic shape. The silicene of this invention is a layered stack of multiple quasi-two-dimensional honeycomb silicon lattices, a honeycomb quasi-two-dimensional (Q2D) structure formed by replacing graphite atoms with silicon atoms in a graphene-structured form. Because there are very few covalent bonds between the layers of the layered silicon lattice, a large number of hydrogen atoms can be adsorbed between the layers. The interaction between hydrogen molecules and silicene layers weakens, greatly increasing the possibility of them embedding atoms and molecules of other materials between the layers, thus solving the problem of the difficulty in bonding silicon and hydrogen. While this type of silicene structure has been theoretically studied, no stable real-world examples have been reported. Similar substances to laminated siloxenes include layered polysilane (Si6H6), Kautsky-type siloxene (Si6O3H3), and Weiss-type siloxene (Si6H3(OH)3) type laminated siloxenes. These three types of laminated siloxenes are actually pre-existing groups of similar substances, with basic structures as follows: Figure 2 .

[0045] Silicon is difficult to combine with hydrogen to form stable hydrides, which greatly limits its potential as a hydrogen storage material. This invention uses a metal alloying (MA) method, a process that involves thoroughly mixing powdered materials in a high-precision ball mill with moderate mechanical strength or assisted by heating to alloy them. This solves the problem of difficult silicon-hydrogen combination by introducing a non-silicon medium to create a cyclical hydrogen adsorption / release process. In the embodiments of this invention, the MA method shows significant effects, especially during hydrogen release, where the ambient temperature for hydrogen release can be adjusted. The MA process adds TiCl4 (hereinafter referred to as TC additive) and / or metal hydride-based storage and release aids while homogenizing the hydrogen storage base material, ensuring thorough mixing and achieving higher efficiency in hydrogen storage and release.

[0046] Step 2 involves first synthesizing layered calcium silicide from silicon and calcium metals, and then using acid to remove calcium atoms present between the layers of the layered calcium silicide CaSi2. This process specifically includes the following steps:

[0047] Using waste silicon sludge from photovoltaic or semiconductor slicing processes as raw material, the silicon micropowder, after washing and drying, and particle size classification, is high-purity silicon micropowder with a size of 50-200 nm and a water content of less than 0.1%. This is used as the basic raw material for this invention, with a purity of 4.8N or higher (this invention requires a purity higher than 5N; 4.8N can also be used in experiments, but this will cause some data fluctuation). Specifically, the required Si content is 99.998%, and the radioactive elements U and Th must be <0.001 ppbWt (subsequent hydrogen storage container system patents will have more specific requirements). The silicon micropowder used as a hydrogen storage raw material needs to be cleaned to remove residual cutting fluid from wire cutting and material impurities from the wire cutting wire. Microscopic images show that most silicon micropowder particles are scaly or dendritic in shape, preferably in a quasi-two-dimensional (Q2D) shape. The size refers to the maximum shape dimension of the surface surrounding a single silicon micropowder particle. For example, if the silicon micropowder particles are shaped like snowflakes, the size refers to the maximum distance between two points on the front of the snowflake. High-purity Ca micro powder has a purity ≥99.99%, uniform particle size, and a particle size scale of 50–200 nm with a D50 of 80–130 nm. It must also be non-radioactive and free of residual impurities. Microscopic images of high-purity Ca micro powder show it as quasi-spherical or blocky; in addition to size, it must also meet the D50 size requirement.

[0048] The prepared qualified Si and Ca micro powders are mixed in a molar weight ratio of 2:1 (e.g., 28×2g:40g) at room temperature under argon purging conditions using a mixer to form a dark gray micro powder. The mixer must operate in an argon atmosphere of 1 atmosphere throughout the process. After mixing, the powder is directly transferred to a quartz container for the next process in an argon atmosphere. After cooling to room temperature, the powder is removed and placed in a covered, sealed polytetrafluoroethylene container.

[0049] The quartz container containing the thoroughly mixed micro-powder is pushed into a high-temperature furnace (resistance furnace or electromagnetic carbon plate furnace, furnace temperature 20-900℃, maintaining a vacuum of ≤1000 Pa; if using inert gas protection, after placing the quartz container into the working chamber, close the door and evacuate to 1000 Pa, then slowly fill the chamber with argon gas, maintaining a pressure of 1000 Pa, and raise the temperature to 900-1200℃. For small-scale samples, maintain this temperature for 2 hours (depending on the capacity of the quartz container; 2 hours for a single quartz transfer container with a volume of 20L; 2.5 hours for 30L). Then, the temperature is reduced in three stages, maintaining a constant pressure of 1000 Pa during the cooling process: 900℃ (2-2.5 hours) → 30 minutes to 600℃ (1 hour) → 60 minutes to 300℃ → 2 hours to 25℃. Argon gas is then added to one atmosphere, the door is opened, and the generated CaSi2 is removed. The intermediate product CaSi2 at this point... It is a pure white, slightly grayish, blocky solid. Calcium silicide has a layered structure, such as... Figure 2As shown in e), calcium atoms (represented by solid black circles "●") are sandwiched between graphene-like silane monolayer structures (zigzag sheet structures composed of silicon atoms "○"). The calcium atoms in this lattice structure can be removed by the method described below. Therefore, it can be transformed into a hydrogen-adsorbing material that silicon itself cannot achieve with a "diamond structure".

[0050] Under normal pressure, the CaSi2 solid block is fully pulverized by a precisely controlled pulverizer. The solid block is brittle and easy to process into powder. After two sieving and pulverizing processes, D50 powder with a size of less than 1μm can be obtained. After multiple cycles of pulverization, the yield can reach more than 90%.

[0051] Layered polysiloxane Si6 was obtained. Figure 3 The process is as follows: Concentrated sulfuric acid (analytical grade, not less than 38%) is cooled to -30°C, and CaSi2 is poured in evenly and steadily with stirring to allow for complete reaction, yielding Weiss-type siloxane Si6H3(OH)3, which further (described below) yields siloxane Si6; dilute sulfuric acid or dilute hydrochloric acid (concentration 10–30%) is poured into CaSi2 micropowder and stirred to allow for complete reaction, yielding Kautsky-type siloxane Si6O3H3, which further (described below) yields siloxane Si6H6; dilute sulfuric acid or dilute hydrochloric acid (concentration 10–30%) is cooled to 0°C, poured into CaSi2, and stirred to allow for complete reaction, yielding siloxane Si6. Occasionally, heat generation may occur during the above reaction process. In such cases, the reaction vessel is slowly cooled to ensure that only a controllable amount of heat is released during the reaction.

[0052] The above three processes yield three types of "silicene" substrates suitable for hydrogen storage. All subsequent acid solutions must be tested and recovered, and then recycled to reduce costs and environmental impact. The acids used in the embodiments of this invention are all of analytical grade.

[0053] The above-mentioned hydrogen storage substrates (CaSi2, Si6H6, Si6, and Si6O3H3) must be processed using their respective dedicated equipment and cannot be used interchangeably. Qualified particle sizes are obtained using mature and commonly used processes such as filtration, washing, drying, grading, and recycling / reprocessing of intermediate products. Furthermore, these hydrogen storage substrates differ in density and manufacturing process, catering to diverse customer needs and covering the main basic materials usable for hydrogen storage: GP-H(A), GP-H(B), and GP-H(C). GP-H(A) is Si6H6; GP-H(B) is silane Si6 derived from Weiss-type siloxane Si6H3(OH)3; and GP-H(C) is polysilane Si6H6 derived from Kautsky-type Si6O3H3.

[0054] The three major categories (Si6H6, Si6O3H3, Si6H3(OH)3) of silicene series substances obtained through the above steps yield silicene structures Si6 ( Figure 2 a)). Polysiloxane Si6H6 is heat-treated at 900–1100 °C under vacuum (~100 Pa) for 1 hour to obtain a gray-black siloxane structure Si6 in powder and block form. This step is crucial; 100 Pa is a key pressure value. The purpose of preparing the three types of siloxane is to obtain high-quality Si6.

[0055] The obtained layered siliceous materials (three types with differences in micro-lattice structure and corresponding physicochemical properties) were thoroughly stirred with LiH, MgH2, and TiH2 respectively to form three GP-H hydrogen storage materials. Nanoscale powder materials can be achieved using the MA method. If nano-sizing is insufficient, larger micron-sized particles can be repeatedly processed through fractionation. Figure 4 The purpose of this process is to: use trace amounts of LiH as an important medium to promote the adsorption of hydrogen molecules on the surface of Si nanostructures when storing hydrogen in silicon-based nanoparticles; and to use MgH2 to gradually release the adsorbed hydrogen when the silicon-based nanogroups release hydrogen under the application of an external triggering mechanism (like the accelerator pedal of a gasoline car), and to immediately stop the triggering mechanism when the accelerator pedal is released, thereby instantly stopping the release of hydrogen.

[0056] To achieve complete nano-sizing, the following processes can also be included: alloying nano-silicon with germanium (Ge) and tin (Sn) to obtain the following material: Si 1-x Mx (M = Ge, Sn) is used, and the final component X is determined based on the effectiveness of GP-H(B) or GP-H(C) hydrogen storage materials. Different values ​​of X between 0 and 1 result in different hydrogen storage effects. Ge and Sn are both group 14 elements. Experimental data show that different choices of X have a certain impact on the three types of hydrogen storage materials. The experimental data also indicate that group 14 elements can maintain valence bond stability and increase the number of charge-discharge cycles.

[0057] After removing the calcium atoms present in the interlayer of layered calcium silicide CaSi2 using acid, the substances shown in Table 1 were obtained. The simple physical properties of these substances are listed in Table 1.

[0058] Table 1: Density measurements of various layered silicon compounds

[0059]

[0060] The blocky CaSi2 crystals obtained in the experimental process have a thin, black, seaweed-like coating around their edges. This is due to a trace reaction between Ca and quartz in the high-temperature region. All experimental verifications were conducted in a double quartz tube structure. A high-purity graphite layer, formed into a paste with acetone solvent, was coated on the inner wall of the inner quartz tube to weaken the reaction between quartz and high-purity calcium powder, resulting in a sushi-like seaweed coating on the sample. This coating was completely removed before XRD analysis. The physicochemical densities of the verification samples related to this invention are shown in Table 1. Si6H6 is sample (A); Weiss-type and Kautsky-type samples, after being heated to 1000℃ and slowly cooled, yielded silicene Si6 with slightly different properties, defined as samples (B) and (C), respectively. Because these samples are all Q2D materials, their texture is relatively loose, with a density greater than that of crystalline silicon (2.33 g / cm³). 3 The density is significantly lower, by 23-40%. As shown in the synthesis method, different acid concentrations and processing temperatures result in different layered silicon compounds. Their density is approximately 1.4. 1.8g / cm 3 This indicates that there is a loose interlayer structure in the silicene lattice, which has enough space to accommodate hydrogen. Please see the specific examples below for details.

[0061] This invention provides a method for hydrogen adsorption of silicon, specifically including the following steps:

[0062] Step one involves preparing layered polysiloxane, Weiss-type siloxane, and Kautsky-type siloxane, releasing the hydrogen contained in the layered polysiloxane, and transforming the Weiss-type and Kautsky-type siloxane into layered stacked siloxane at high temperature. This invention uses cleaned, dried, and particle-graded nano-silica powder as the base material. To verify key process products in a transparent quartz container, a qualitative visual experiment was employed to observe the preparation process of CaSi2 single crystals. Pure Ca blocks with a purity of 99.99% were prepared. The raw materials were mixed in a Si:Ca ratio of (2.0:1), and the mixture underwent crushing, coarse classification, cyclic classification, and sample preparation. The test tube was then sealed in a quartz tube container (~1000 Pa), and the temperature was gradually and uniformly increased to 900~1100 °C, maintained for 1 hour (while uniformly rotating the quartz container). After the reaction was observed to be complete, the sample was cooled and removed. The mixture was then subjected to secondary crushing and classification, followed by cyclic re-classification. After cooling to room temperature, it was resealed in a quartz container (500 Pa) to crystallize CaSi2. The container was then uniformly heated to 1200℃ and maintained at that temperature for 1 hour, with the quartz tube rotated uniformly to ensure complete reaction. Afterward, it was slowly cooled to room temperature. This gradient cooling was used to promote the crystallization of CaSi2.

[0063] Step two involves allowing hydrogen to adsorb into the interlayer space of this layered silicene (creating a microenvironment where hydrogen atoms readily combine with Si atoms in Si6). For example... Figure 5 As shown in a), this is a stacked layered silicene structure. If high-density hydrogen adsorption can be achieved between the layers of this stacked silicene, such as at the location indicated by the dashed box, a lattice structure environment for hydrogen adsorption can be created. Due to its layered structure, unlike magnesium hydride (MgH2), which is difficult to release hydrogen at low temperatures, it can release the hydrogen stored in the interlayer of the stacked silicene lattice at a relatively low design temperature. Figure 5 As shown in c), the state in which hydrogen molecules (two dark cyan ●) or atoms (dashed lines representing light cyan ● weakly bonded to silicon atoms on the silicene sheet) are adsorbed onto the stacked silicene. Its composition is Si6H6(H2)y, and under chemically stable conditions, a larger value of y in the chemical formula is better.

[0064] like Figure 4 As shown, this invention employs the mechanical alloying (MA) method as a technique to increase the hydrogen adsorption capacity of hydrogen-adsorbing materials. The MA method, by nano-sizing the material, aims to achieve the following effects: (i) significantly increasing the specific surface area, making it easier for hydrogen to adsorb onto the surface of the nanomaterial, thereby increasing the hydrogen adsorption capacity; (ii) enabling hydrogen adsorption and release at lower temperatures through nano-sizing. There are several types of traditional MA methods, including those performed in a vacuum, in an inert gas, in hydrogen, or in a liquid. From the perspective of developing high-performance hydrogen-adsorbing silicon, the MA method in a hydrogen atmosphere is the most suitable.

[0065] Furthermore, this invention employs a liquid-phase MA method. Catalytic molecules capable of dissociating hydrogen molecules into hydrogen atoms, such as titanium tetrachloride (TiCl4), are added to solvents like acetone to perform a mechanical alloying operation. Figure 6 As shown, hydrogen dissociation catalytic sites, indicated by asterisks, are formed on the surface of nanoscale layered polysiloxane or stacked siloxane, establishing a method to improve the hydrogen adsorption and hydrogen release rates.

[0066] The following specific embodiments will illustrate the silicon-based solid-state high-density hydrogen storage material, its synthesis method, and its method for hydrogen adsorption on silicon according to the present invention.

[0067] Example 1

[0068] The synthesis method of layered polysiloxane (Si6H6) is as follows: Figure 3As shown. Silicon and calcium metals are mixed in a stoichiometric ratio and reacted at approximately 1000°C to synthesize layered calcium silicide (CaSi2). This layered calcium silicide is then reacted with dilute hydrochloric acid or dilute sulfuric acid cooled to its freezing point (0°C) to obtain layered silicene. Specifically, silicon and calcium powders are ground and thoroughly mixed in a mortar. This mixture is then placed in a double-walled quartz tube and reacted at 900°C for 1 hour. The upper part of the product contains small or trace amounts of impurities, which need to be removed. The product is then ground and mixed again, and placed in the double-walled quartz tube and reacted at 1000°C for 2 hours to ensure complete reaction. Even smaller amounts of impurities remain on the upper part of the reacted product and need to be removed. The thoroughly reacted product is then ground and mixed to ensure homogeneity. XRD analysis confirms the product as layered CaSi2. Figure 2 f), where, Figure 2 f) The horizontal axis is 2 q The black line represents the result of CaSi2. ； The red line represents the results for the powder sample after heat treatment at 1000°C. The XRD spectra of the two materials match at the 2q position indicated by the red dashed line, indicating that the XRD spectra reflect the monolayer silane structure of layered calcium silicide. In other words, the powder sample is a "stacked silane" formed by stacking monolayer silane structural frameworks. The product powder is added to dilute hydrochloric acid or dilute sulfuric acid cooled with ice water while stirring to react and obtain layered polysilane Si6.

[0069] Example 2

[0070] The synthesis method of Weiss-type siloxanes is similar to that of layered polysiloxanes (see [link]). Figure 3 The difference lies in the use of concentrated sulfuric acid (concentration not less than 38%) and a temperature of -30°C. Specifically, layered calcium silicide powder can be obtained using the same method as in Example 1. The product powder is added to low-temperature sulfuric acid while stirring to react and obtain Weiss-type siloxane Si6H3(OH)3. A small amount of fine bubbles may appear during the operation; it is necessary to stir continuously to eliminate the foam.

[0071] Example 3

[0072] The synthesis method for Kautsky-type siloxanes is the same as that for Weiss-type siloxanes. Layered calcium silicide powder was obtained using the same method as in Example 1. The product powder was then added to dilute sulfuric acid or dilute hydrochloric acid while stirring to react and obtain Kautsky-type siloxane Si6O3H3.

[0073] The three layered silicon compounds obtained in Examples 1-3 were subjected to heat treatment at approximately 1000°C. This removed the bound hydrogen or hydroxyl groups, transforming them into layered, stacked siloxanes. XRD measurements confirmed that the treated products retained the lattice structure of siloxanes. Figure 2 f).

[0074] The synthesis methods of the layered silicides in Examples 1-3 are industrially feasible. Calcium silicide can be used in an industrial crucible under an inert gas atmosphere. The reaction is carried out in an industrial electric furnace at 1000°C. After thoroughly removing floating impurities from the surface of the reactants, they are pulverized. The calcium silicide powder is reacted with acid in a glass container to obtain various layered silicon compound powders. However, for layered polysilene, a cooled container must be used. Finally, heat treatment is performed at approximately 1000°C to obtain stacked polysilene powder. The layered polysilene can be used directly.

[0075] Stacked silicene or layered polysilicene powders are mixed with lithium hydride powder in organic solvents such as acetone, acetonitrile, and tetrahydrofuran, and then nanoparticles are formed using a mechanical alloying device. After reaching a certain degree of nanoparticle size, a hydrogen separation and dissociation catalyst, such as titanium tetrachloride (TC), is added for final nanoparticle formation. During this process, with titanium tetrachloride (TC), titanium atoms bind to the surface of the stacked silicene or layered polysilicene nanoparticles, forming... Figure 6 The catalytic sites are shown. TC is highly hygroscopic and should be handled in a sealed glove box; dissolve it in organic solvents such as acetone, acetonitrile, or tetrahydrofuran. After removing the nanoparticle-sized stacked siliceous or layered polysiliceous samples, store them in a dry environment.

[0076] Next, hydrogen adsorption experiments will be conducted using the three layered silicon compounds obtained in Examples 1-3.

[0077] The density measurements and pretreatment conditions of the samples used in the hydrogen adsorption experiment are shown in Table 2. The synthesized layered polysiloxane sample is designated Sample (A); the samples obtained by heating Weiss-type siloxane and Kautsky-type siloxane at 1000°C for 1 hour are designated Sample (B) and Sample (C), respectively. Furthermore, since these stacked silicon compounds are composed of microscopic sheet-like siloxanes or similar compounds, their density is 2.33 g / cm³ relative to silicon. 3 It is significantly smaller, and its density is approximately 60-77% of that of silicon.

[0078] Table 2: Density determination and treatment conditions of Smple1~3 layered silicon compounds

[0079]

[0080] Note: The density of crystalline silicon is 2.33 g / cm³. 3

[0081] Nanoparticles were prepared using the mechanical alloying (MA) method. Samples (A) to (C) were nanoparticle-sized using an experimental mechanical alloying apparatus manufactured by Nissin Giken Co., with the following parameters set: room temperature (25±5℃), and a rotation speed of 1600 rpm (higher end of the 500-1600 rpm range). The MA process theoretically had no upper limit, but 20 hours of testing showed that the target value was essentially achieved, thus this was determined as the standard operating time. Practice has shown that higher rotation speed and longer duration are highly beneficial for the MA nanoparticle-sized process, resulting in a higher degree of nanoparticle formation; however, the above conditions were used in this experiment. Before preparation, the material's size distribution was 5-10 mm; after nano-M(A) formation, samples with particle sizes of 10-200 nm were obtained. The particle size of the samples after the experiment was measured by an industrial technology center, and the average particle size was approximately 100 nm, basically satisfying D50=100 nm, indicating that the sample particle size significantly decreased and became more uniform after MA treatment.

[0082] Next, various metal hydrides were mixed with layered silicon compound samples (A) to (C) under the following conditions to achieve nanocomposite formation. Since titanium tetrachloride (TiCl4) was required as a hydrogen dissociation catalyst, the nanocomposite formation experiments were conducted in methanol. Furthermore, due to the extremely hygroscopic nature of titanium tetrachloride, it was necessary to dissolve it in methanol under an argon atmosphere for homogenization.

[0083] 1. Layered silicon compounds: Sample (A)~(C);

[0084] 2. Metal hydrides: Lithium hydride (LiH), titanium hydride (TiH2), magnesium hydride (MgH2), abbreviated as MH;

[0085] 3. Mixing conditions: All metal hydrides mentioned above are in a weight ratio of 10% or 20%;

[0086] 4. Hydrogen dissociation catalyst (TiCl4): No addition or 5% addition.

[0087] After the above ingredients were prepared, the hydrogen adsorption experiment of the nanocomposite layered silicide was carried out.

[0088] Hydrogen adsorption experiments on nanocomposite layered silicon compounds were conducted using a 20L hydrogen cylinder manufactured by Scitem. This cylinder has a hydrogen pressure below 1 MPa, and its advantage is that it can be used without special equipment or industrial permits. The hydrogen adsorption experiments used a self-made [equipment / system]. Figure 7The simplified apparatus shown is connected to an existing vacuum degassing system. A stainless steel container equipped with a heater holds a quartz tube filled with the powdered sample. To prevent powder scattering, the opening of the quartz tube is covered with high-purity glass wool. The entire container can be heated to 400°C. While heating, the sample in the quartz tube is degassed using a vacuum device, and then hydrogen gas is introduced into the stainless steel container. Hydrogen gas generated by the hydrogen adsorption alloy canister is pressurized to 1-3 atmospheres via a pressure regulating valve before being introduced into the stainless steel container. Each powder sample contains 10 grams.

[0089] Before conducting the hydrogen adsorption experiment of the nanocomposite layered silicon compound, the following preliminary experiments were carried out to determine the experimental conditions and which of the three metal hydrides was superior.

[0090] Sample (A) is layered polysiloxane, which is itself a hydride. Therefore, stacked siloxane Si6 (actually Sample (B)) was chosen as a substitute comparative sample for the preliminary experiment. The results are shown in Table 3. The experiments were conducted at room temperature and 300°C, respectively, with a hydrogen supply pressure of 3 atm in both cases. The metal hydride mixing ratio was 10%, and the hydrogen dissociation catalyst TC was not used.

[0091] The preliminary hydrogen adsorption results for Sample (B) are summarized in Table 3, providing a clear view of the details. First, for the stacked siliceous olefins (sample number (B)-00) that underwent heat treatment at 1000℃ but were not nanoparticle-based, the mass gain rate was ±0% within the error range after 3 hours at room temperature, and no hydrogen adsorption was observed. In contrast, the nanoparticle-based sample (sample number (B)-01) without metal hydride mixture showed a mass gain rate of 0.6% after 2 hours at room temperature, which, although small, confirmed hydrogen adsorption. The composition at this time was Si6H. 1.0 This is equivalent to 1 hydrogen atom being adsorbed for every 6 silicon atoms.

[0092] Table 3: Results of hydrogen adsorption preparatory experiments using Sample (B)

[0093]

[0094] Note: The mass of stacked silicene is 168.54 g / mol, used to calculate the number of hydrogen atoms.

[0095] When 10% metal hydride was mixed (samples (B)-02~04), the mass gain rate after 3 hours at room temperature was significantly higher than that without metal hydride. This indicates that mixing with metal hydrides is crucial for improving hydrogen adsorption when nanoparticle-forming stacked silicon compounds. Among the metal hydrides, magnesium hydride (MgH2) showed a particularly significant effect, while lithium hydride (LiH) had a less pronounced effect. Considering the decomposition temperatures of metal hydrides (self-tested: magnesium hydride MgH2 is 300~400℃, titanium hydride TiH2 is 500~650℃, and lithium hydride LiH is approximately 720℃), when mixed with stacked silicon compounds and nanoparticle-forming via the MA method, it was confirmed that the lower the decomposition temperature of the metal hydride, the higher the hydrogen adsorption characteristics.

[0096] The hydrogen adsorption characteristics of Sample (B) are more pronounced at 300°C. In particular, when mixed with 10% magnesium hydride (MgH2), the mass gain rate reached 3.2% after 3 hours, achieving excellent results. This is equivalent to Si6H... 5.4 Its hydrogen content is almost comparable to that of layered polysiloxane Si6H6, but its hydrogen adsorption properties still need further improvement.

[0097] Therefore, magnesium hydride MgH2 (abbreviated as "MH") was used as a metal hydride to conduct formal hydrogen adsorption experiments on three samples (A) to (C).

[0098] The following are the formal experimental results of hydrogen adsorption of nanocomposite layered silicon compounds.

[0099] 1. Case of Sample(A)

[0100] Hydrogen adsorption experiments on the nanocomposite layered silicon compounds were conducted under the same conditions as the preliminary experiments, and the results are shown in Table 4. Note that the original chemical formula of Sample (A) is Si6H6 of layered polysiloxane, while Sample (B) and Sample (C) are Si6H6 of stacked siloxane and layered Si6, respectively. In other words, the layered polysiloxane is a compound that already contains 3.6% hydrogen. This is taken into account when discussing the results.

[0101] The results of hydrogen adsorption experiments using Sample (A) are summarized in Table 4, and these results are illustrated in the figure below. Figure 8 Combining Table 4 and Figure 8The details are now clear. Even without metal hydrides and hydrogen dissociation agents (samples (A)-1 (room temperature) and (A)-6 (300℃)), hydrogen was slightly adsorbed, with greater adsorption at 300℃. Mixing 10% metal hydride MH (samples (A)-2 (room temperature) and (A)-7 (300℃)) significantly increased hydrogen adsorption, further increasing with the addition of 2% hydrogen dissociation agent TC (samples (A)-4 (room temperature) and (A)-9 (300℃)). Mixing 20% ​​metal hydride MH (samples (A)-3 (room temperature) and (A)-8 (300℃)) further increased hydrogen adsorption, but the increase did not double with the mixed amount. Adsorption was greater at 300℃, but the increase was not significant relative to the higher temperature. The addition of hydrogen dissociation agent TC (samples (A)-5 (room temperature) and (A)-10 (300℃)) also had a significant effect.

[0102] Table 4: Results of hydrogen adsorption experiments using Sample (A)

[0103]

[0104] Note: Molar mass of layered polysiloxane Si6H6: 174.54 g / mol (for calculation).

[0105] 2. Case of Sample (B)

[0106] The results of hydrogen adsorption experiments using Sample (B) are summarized in Table 5. These results are shown in... Figure 9 Combining Table 5 and Figure 9 The details are now clear. The results for Sample (B) differ significantly from those for Sample (A) in that Sample (A) starts with 3.6% hydrogen adsorption, while Sample (B) starts with zero (due to the formation of a stacked silicene Si6 structure after 1000℃ heat treatment). Furthermore, the hydrogen adsorption in Sample (B) changes more significantly over time. The increase in hydrogen adsorption due to the addition of TC is quite substantial. In this case, the hydrogen adsorption rate is also relatively high. The maximum hydrogen adsorption after 3 hours is 7.0% for Sample (A) (equivalent to the composition Si6H). 12.0 Sample (B) is 5.6% (equivalent to the composition Si6H). 9.0 ), relatively small.

[0107] Table 5: Results of hydrogen adsorption experiments using Sample (B)

[0108]

[0109] Note: Molar mass of stacked silicene Si6: 168.54 g / mol (for calculation)

[0110] 3. Case of Sample (C)

[0111] The results of hydrogen adsorption experiments using Sample (C) are summarized in Table 6, and these results are illustrated in the figure below. Figure 10 Combining Table 6 and Figure 10 You can see the details clearly. Please note, Figure 10 The vertical axis of the results at room temperature and 300°C is magnified by 2 times. In the case of Sample (C), the amount of hydrogen adsorption is reduced by about 60% compared with Sample (B).

[0112] Table 6: Results of hydrogen adsorption experiments using Sample (C)

[0113]

[0114] Note: The molar mass of Si6O3, a compound similar to stacked silicene, is 216.54 g / mol (for calculation purposes, assuming Si6O3 matrix).

[0115] 4. Hydrogen adsorption release test

[0116] Hydrogen release experiments were conducted in the atmosphere at room temperature and 150°C with and without a hydrogen dissociation agent, using MH concentrations of 20%. The results are shown in... Figure 11 In all cases, whether at room temperature or 150°C, the initial hydrogen release rate is higher with the addition of TC, while it gradually approaches the level of the hydrogen dissociation agent without addition, decreasing exponentially. Particularly noteworthy is the case of Sample (A), which appears to gradually approach the hydrogen content of Si6H6 (3.6%). This trend is particularly evident at 150°C. In this sense, Sample (A) is best pretreated at 1000°C. Additionally, Sample (C) exhibits a slower hydrogen release rate.

[0117] Figure 11 Preliminary qualitative results show the hydrogen release properties of layered, multilayered siliceous powder.

[0118] Figure 11 The results show that under room temperature conditions (room temperature ~ 20℃), there is a lower limit to the natural release of H2: 2%. In other words, under conditions without external triggering, there is residual hydrogen in the hydrogen storage container or it is not easy to prevent it from being released, which is very unfavorable for productization. Figure 11The right figure shows that under a temperature increase of 150°C, the stored hydrogen can be reduced to near zero, but this takes time and is not conducive to practical application after productization (in fact, the temperature of natural hydrogen release should not be controlled too low. For example, in summer, when parking in a dry and hot open-air parking lot, the temperature of the whole vehicle or other hydrogen storage products can reach close to 100°C, which will significantly increase the natural release of hydrogen and bring additional pressure to the hydrogen storage container and pressure buffer system).

[0119] Finally, the present invention measured the natural hydrogen release of the hydrogen-adsorbing material (GP-H). The test container was a sealed single-layer quartz container. 5 kg of samples (A)10 and (B)10 were placed at stable temperatures of 5°C and 30°C for 5 days and 10 days, respectively. The measured pressure data of the hydrogen storage container (GP-H materials (A)10 and (B)10) showed an increase of less than 5%, which indirectly showed that the natural hydrogen release rate of all groups was ≤5%, and the release rate at 30°C was slightly higher than that at 5°C. The release rate after 10 days of placement was slightly higher than that after 5 days, which is consistent with the conventional rule that "increased temperature and extended time may slightly promote hydrogen release".

[0120] This patent only discusses the effect of measured temperature on hydrogen release when describing the conditions for hydrogen release from GP-H hydrogen storage materials. In reality, a hydrogen release device assisted by an electric pulse with a suitable ultrasonic frequency and appropriate wavelength can be added to the hydrogen storage container to meet the needs of customers who require rapid hydrogen release response. This will not be described in detail here.

[0121] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for synthesizing silicon-based solid-state high-density hydrogen storage materials, characterized in that, Includes the following steps: Using silicon dust / silicon sludge discarded from silicon wafer cutting as the base material, silicon micro powder with nanoscale size is obtained after cleaning and drying. The purity of the silicon micro powder is set to be above 4.8N, the size is 50~200 nm, and D50 = 80~130 nm. The silicon micro powder is synthesized with calcium metal to form layered calcium silicide. Specifically, the silicon micro powder and calcium micro powder are synthesized to form layered calcium silicide. Then, the calcium ions present between the layers of the layered calcium silicide are removed. The calcium silicide is then fully pulverized by a precision-controlled pulverizer. The solid block of CaSi2 is brittle and easy to pulverize. After two sieving and pulverizing processes, D50 powder with a size of less than 1 μm can be obtained. The powder is then pulverized repeatedly. Concentrated sulfuric acid is cooled to -30°C, then poured into CaSi₂ in a uniform and stable amount and stirred to allow for complete reaction. Alternatively, dilute sulfuric acid or dilute hydrochloric acid at room temperature is poured into CaSi₂ powder and stirred to allow for complete reaction. Or, dilute sulfuric acid or dilute hydrochloric acid is cooled to 0°C, poured into CaSi₂ and stirred to allow for complete reaction, yielding layered silicene. Layered silicene has a quasi-two-dimensional network-like stacked hydrogen storage structure. The basic lattice structure of the silicon micropowder is a silicene structure, that is, a quasi-two-dimensional material in which silicon atoms are arranged in a honeycomb lattice planar pattern and have a wavy mesoscopic / microscopic shape; the layered silicene is a layered stack of multiple quasi-two-dimensional honeycomb silicon lattices, which is a honeycomb quasi-two-dimensional Q2D structure after graphene atoms are replaced by silicon atoms. The density of the obtained hydrogen storage material is 1.4~1.8 g / cm³. 3 The hydrogen storage capacity is 4~9wt%.

2. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 1, characterized in that, The radioactive elements U and Th in the silicon micropowder must be < 0.001 ppbWt, and its shape as shown in the micrograph is a quasi-two-dimensional Q2D shape; the calcium micropowder is set as a dry white micro powder with a particle size of φ0.5~10μm, and its shape as shown in the micrograph is quasi-spherical or blocky.

3. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 2, characterized in that, The silicon micro powder and the calcium micro powder were thoroughly mixed in a molar weight ratio of 2:1, and then subjected to high temperature and vacuum. After that, argon gas was injected into the cavity to maintain the high temperature and then cooled down to obtain a pure white, slightly gray blocky solid CaSi2.

4. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 3, characterized in that, The CaSi2 was stirred with dilute sulfuric acid or dilute hydrochloric acid at room temperature and allowed to react fully to obtain Kautsky-type Si6O3H3.

5. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 3, characterized in that, The CaSi2 was stirred with concentrated sulfuric acid under freezing conditions and reacted fully to obtain Weiss-type siloxane Si6H3(OH)3 with the perhydroxyl group removed.

6. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 3, characterized in that, The CaSi2 was reacted with dilute sulfuric acid at a temperature near the freezing point to obtain silicene Si6.

7. The method for synthesizing silicon-based solid-state high-density hydrogen storage material as described in claim 1, characterized in that, The purity of the silicon micropowder is set to be above 5.0N.

8. A silicon-based solid-state high-density hydrogen storage material, characterized in that, The hydrogen storage material, synthesized by the method described in any one of claims 1-7, comprises a polysiloxane structure Si6 based on Si6H6, Si6O3H3, and Si6H3(OH)3 siloxane series materials, with a hydrogen storage capacity of 4-9 wt%. The hydrogen storage material is a quasi-two-dimensional network stacked hydrogen storage structure, consisting of multiple layers of quasi-two-dimensional honeycomb silicon lattices stacked together. This honeycomb quasi-two-dimensional Q2D structure is formed by replacing graphite atoms with silicon atoms in a graphene structure, and has a density of 1.4-1.8 g / cm³. 3 .

9. A method for hydrogen adsorption of silicon using the silicon-based solid-state high-density hydrogen storage material as described in claim 8, characterized in that, Specifically, the following steps are included: Layered polysiloxane, Weiss-type polysiloxane, and Kautsky-type polysiloxane are prepared, and hydrogen is released from the layered polysiloxane. The Weiss-type polysiloxane and Kautsky-type polysiloxane are then converted into layered stacked polysiloxane at high temperature. The liquid-phase MA method is used, which involves adding titanium tetrachloride (TiCl4) to acetone solvent to dissociate hydrogen molecules into hydrogen atoms and perform mechanical alloying to form hydrogen dissociation catalytic sites on the surface of nano-sized layered polysiloxane or stacked siloxane, thereby improving the hydrogen absorption / desorption rate. Hydrogen is adsorbed between the layers of this layered silicene structure, and the low-density, loose lattice structure facilitates the absorption / release of hydrogen atoms and molecules.

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