Regenerable system for solid-state hydrogen storage

Abstract

The present invention relates to a regenerable system for the storage of hydrogen in the solid state comprising a layered composite material comprising at least five layers, wherein the two outermost layers of the layered composite material comprise microcrystalline cellulose, the innermost layer of the layered composite material comprises at least one hydrogenated chemical compound of boron and nitrogen and between each outermost layer of the layered composite material and the innermost layer of the layered composite material there is an intermediate layer comprising a metal catalyst for hydrogenation and dehydrogenation. A method for obtaining hydrogen by means of such a system is further described.

Description

[0001] Regenerable system for solid-state hydrogen storage

[0002] Field of the invention

[0003] The present invention relates to a regenerable system for the storage of hydrogen in the solid state, a process for the regeneration thereof, and a process for the production of hydrogen (H2) involving said system.

[0004] Background art

[0005] The storage of hydrogen is a key element in the use of the latter as a fuel. For this reason, the approach selected to achieve said storage must be as safe and efficient as possible. Numerous different technologies are currently available, each with strengths and weaknesses.

[0006] As demonstrated by the definition of the SAE J2600 standard on the connection devices for the refueling of compressed-hydrogen vehicles by the Society of Automotive Engineers, compressed gas is currently the most widely used hydrogen storage technology. In 2011, both cost and performance of hydrogen storage tank systems for the automotive sector were evaluated and compared; these tanks were designed to operate at 350 bar and 700 bar, and they were capable of storing 5.6 kg of hydrogen. The conclusion of this study showed that none of the tanks met the automotive system targets for volumetric capacity or cost. Since then, compressed hydrogen has not yet made a real breakthrough. At present, in the automotive sector, a maximum volumetric energy density of up to 4.9 MJ / 1 has been reported by the Toyota Motor Corporation for the 700 1 Mirai tank. Furthermore, the tank for compressed hydrogen exhibits various problems during the refueling step: losing up to 4% by weight of the gas. Finally, the materials used for producing these compressed hydrogen tanks must meet certain mechanical requirements to avoid brittleness, cracks, and leaks, and they must have a geometry and a weight, which do not compromise the performance of the vehicle.

[0007] The storage of liquid hydrogen is a well-established technology and it is the key technologyused, to date, by the existing industrial infrastructure network for delivery and storage. The technical requirement for keeping hydrogen in the liquid state is maintaining a tank temperature not exceeding -253 °C, a temperature, which corresponds to the boiling point of hydrogen. Liquid hydrogen tanks are not typically designed to withstand elevated internal pressure, therefore they must be suitably insulated to reduce the transfer of heat from the environment to the liquid contained therein. As seen, since liquid hydrogen tanks are not usually designed to withstand high internal pressure, hydrogen is generally let out through a safety valve, referred to as a "boil-off". Large cryogenic tanks for liquid hydrogen are generally sphere- shaped and built to minimize the ratio between the mass and volume of the insulation, with respect to the volume of hydrogen stored. Furthermore, the liquid hydrogen tanks have extremely thick walls to ensure appropriate insulation. The sum of these technical requirements increases the production cost of this technology by up to 1 € / kg of stored hydrogen, with an efficiency of up to 70% for the large tanks. If we then consider the automotive sector, the costs of the liquid hydrogen tanks for this field are even higher: in fact, they may reach 386 € / kg for a tank having an inner volume of 100 L (excluding use thereof for transportation).

[0008] An interesting combination of pressurized and liquid storage methods is shown by the so-called cold cryogenic compression. This technique is based on the storage of hydrogen at cryogenic temperatures ranging from -233°C to 193°C and at a pressure between 250 bar and 300 bar. The cold cryogenic compression tanks are highly insulated tanks, designed to withstand high internal pressure. The storage cost is relatively high, indeed reaching 395 € / kg; however, these tanks are capable of retaining hydrogen for 7 days without loss when the latter are filled to 85% of the maximum capacity thereof.

[0009] Pure hydrogen may further be stored by physisorption in different classes of materials. Due to the properties thereof, the interaction of hydrogen with adsorbent materials is mainly due to Van der Waals forces. The first class of materials used is represented by carbonaceous materials, such as carbon nanotubes (CNTs). The hydrogen adsorption mechanism on these carbon materials has been extensively studied, showing that the adsorbed hydrogen is arranged on the surface of the carbon in a single layer. Consequently, the capacity to store hydrogen depends exclusively on the surface area of the carbon, which follows Chahine'srule, which establishes the limit of 1% by weight of adsorbed hydrogen for each 500 m2 / g of surface area. If the only existing interactions between hydrogen and the solid surface of the material are of the Van der Waals-force type, the aforesaid rule also applies to other organic / inorganic materials. It follows that the CNTs have a maximum capacity to adsorb hydrogen of up to 1.85% by weight at -193°C when subjected to a hydrogen pressure of up to 35 bar, while the activated ultramicroporous carbon could reach a maximum capacity of up to 2.94% by weight at -193°C at atmospheric pressure. Ideally, carbon replicas produced using zeolite as a template could reach a hydrogen uptake of 7.3% by weight at 20 bar and -193°C. The wide range of inorganic templates having adjustable pore sizes and distributions makes this a promising route. For the same reason the so-called inorganic frameworks might also be a good choice for hydrogen physisorption. Hydrogen adsorption by inorganic materials is regulated by the pore size of the inorganic material; in order to obtain a high level of hydrogen adsorption the pore size must be large, and this represents a challenge. Studies have reported a decrease in the isosteric heats of adsorption, suggesting saturation of strong adsorption sites. This behavior is characteristic of materials with a high volume of pores since the adsorption of hydrogen at low pressure and at -193°C occurs with greater frequency when there are pockets on the material or when the surface of the material is corrugated, rather than on materials having smooth surfaces or on edges. An alternative is represented by metal-organic frameworks (MOFs), which operate relatively well at -193°C but with considerably lower performance at ambient temperature and under moderate pressure. The hydrogen storage mechanism inside the MOFs is hydrogen diffusivity inside the structure of the MOFs, depending on the size of the crystals. All the physisorption techniques considered involve a relatively high cost, which, together with the need to use cryogenic temperatures, result in low efficiency due to economic factors and energy consumption.

[0010] Hydrogen could further be stored as hydrogen chemically bound to organic, metal-organic, and inorganic compounds. This storage strategy is referred to as chemical hydrogen and represents a vast field in the sector. For example, the hydrogen could be trapped in simple molecules, such as methane or ammonia, however, the release thereof would not be so easy. In fact, the production of hydrogen from the cracking of methane is rather costly and requires temperatures exceeding 500°C. Furthermore, due to the thermodynamics of the process, oneof the by-products obtained is carbon. An alternative way of producing hydrogen is methane steam reforming, which, however, presents the same problems related to the use of a high temperature and a high pressure. For this reason, the diffusion thereof is limited outside refinery plants. As an alternative to methane, ammonia is another possible chemical hydrogen storage molecule; however, it entails similar problems. An easier and more promising type of chemical hydrogen storage provides for the use of organic species, such as aminoboranes as hydrogen carriers. Aminoboranes (and, in particular, ammonia borane) have been widely used for the hydrogen release process, both through thermolysis and hydrolysis. The theoretical gravimetric hydrogen storage (GHS) capacity reaches the significant value of 19.6% by weight, but the hydrogen release mechanism is relatively complex and entails the release of boron and nitrogen compounds. This is a significant disadvantage considering the high level of hydrogen purity required for applications, such as fuel cells and considering the scarce regenerability of the process. Alternatively, liquid organic hydrogen carriers, such as N-ethylcarbazole derivatives, represent a class of compounds characterized by high regenerability and a high GHS of up to 22.1% by weight. However, the use of liquid organic hydrogen carriers requires massive use of noble metals to release / incorporate the hydrogen and they are also relatively risky for human safety. Hydrogen could further be chemically stored in inorganic hydrides, such as LiBH4 or magnesium hydrides, achieving a GHS ranging from 14.9% by weight to 18.5% by weight, with a volumetric energy density of up to 17.6 MJ / 1. Despite these interesting properties, inorganic hydrides are difficult to regenerate and sensitive to water. In fact, to date, all means of chemical hydrogen storage are still rather costly, but despite this, they represent the most promising options, especially for the small-scale applications in the mobility sector and everyday life.

[0011] Consequently, the need is therefore felt in the market to develop a solution having high gravimetric density, high volumetric density and high energy density to store hydrogen in a wide temperature range under the highest safety standards required by the mobility sector.

[0012] Summary of the invention

[0013] It is therefore the object of the present invention to provide a system for storing hydrogen inthe solid state, which is regenerable, has high gravimetric density, high volumetric density, and high energy density, so as to store hydrogen over a wide temperature range under the highest safety standards required by the mobility sector.

[0014] Such objective is achieved by a regenerable system for the storage of hydrogen in the solid state as outlined in the appended claims, the definitions of which form an integral part of the present description.

[0015] Detailed description of the invention

[0016] Ammonia borane has attracted considerable interest as a promising material for solid-state hydrogen storage by virtue of the elevated hydrogen content thereof, indeed, it may reach a percentage of 19.6% by weight. Ammonia borane is also a chemical compound, which is relatively easy to produce and store in low-humidity environments, without undergoing a significant process of deterioration. The decomposition process of ammonia borane starts at temperatures above 100°C, simultaneously resulting in both the release of hydrogen and the formation of complex by-products containing nitrogen and boron atoms. The formation of these by-products is therefore an undesired thermal reactivity, which limits the field of application thereof. Furthermore, to date, the regeneration of ammonia borane in the solid state presents numerous challenges, which require complex reprocessing procedures. Advantageously, the present invention solves all these problems by means of a layered composite material comprising ammonia borane, wherein the layers have been designed to finely regulate the reactivity of the material, suppressing the formation of by-products and enabling regeneration of the spent hydrogen carrier.

[0017] A first object of the present invention is a regenerable system for the storage of hydrogen in the solid state comprising a layered composite material comprising at least five layers, wherein the two outermost layers of the layered composite material comprise microcrystalline cellulose, the innermost layer of the layered composite material comprises at least one hydrogenated chemical compound of boron and nitrogen, and between each outermost layer of the layered composite material and the innermost layer of the layered composite material there is an intermediate layer comprising a metal catalyst forhydrogenation and dehydrogenation.

[0018] With reference to the present description and the appended claims, the term “composite material” means a heterogeneous material, i.e., consisting of two or more steps having different physical properties, the overall properties of which are better than those of the individual steps forming it.

[0019] With reference to the present description and the appended claims, the term “microcrystalline cellulose” means a purified and partially depolymerized form of cellulose obtained from material of plant origin. It is, therefore, a carbohydrate.

[0020] With reference to the present description and the appended claims, the term “catalyst” means a chemical species, which intervenes during the course of a chemical reaction and which, by modifying the activated complex of the reaction, allows a lowering or an increase of the activation energy, thus increasing (positive catalysis) or decreasing (negative catalysis), the reaction rate, respectively, while remaining unaltered at the end thereof (unlike reagents, which are consumed as the reaction proceeds).

[0021] As known to those skilled in the art, the term “hydrogenation” means a chemical reaction, in which hydrogen is added to a substrate, which may be an element or a compound, normally in the presence of a catalyst. The reverse reaction is called dehydrogenation. Therefore, as known to those skilled in the art, the term “dehydrogenation” means a chemical reaction, in which composites lose hydrogen, with the formation of double bonds between atoms.

[0022] According to a preferred embodiment of the system according to the present invention, the hydrogenated chemical compound of boron and nitrogen is preferably ammonia borane (BNH6).

[0023] According to a preferred embodiment of the system according to the present invention, the metal catalyst for hydrogenation and dehydrogenation is preferably palladium, wherein said palladium has preferably been deposited on each intermediate layer using the plasmacathodic atomization technique sputtering). As known to those skilled in the art, sputtering is a process whereby atoms, ions, or molecular fragments are emitted from a solid material, said target, which is bombarded with a beam of energy particles (generally ions).

[0024] According to a preferred embodiment of the system according to the present invention, the innermost layer of the layered composite material preferably has a weight comprised between 20% and 50% of the total weight of the layered composite material.

[0025] According to a preferred embodiment of the system according to the present invention, the two outermost layers of the layered composite material preferably have a combined weight comprised between 50% and 80% of the total weight of the layered composite material.

[0026] According to a preferred embodiment of the system according to the present invention, each intermediate layer of the layered composite material preferably has a negligible weight relative to the total weight of the layered composite material, preferably having a concentration comprised between 1 ppm and 30 ppm.

[0027] According to a preferred embodiment of the system according to the present invention, the thickness of each intermediate layer of the layered composite material is preferably 30 nm.

[0028] A second object of the present invention is a process for the production of hydrogen (H2) comprising the steps of:

[0029] a) providing a regenerable system for the storage of hydrogen in the solid state, as described above;

[0030] b) heating the system up to a temperature of approximately 155°C so as to destabilize the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material so as to allow the release of pure hydrogen from the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), thereby producing hydrogen (H2) while avoiding the production of partially hydrogenated volatile boron and nitrogen compounds.

[0031] According to a preferred embodiment of the process according to the present invention, theH2 produced in step b) is preferably equal to from 1.1% by weight to 10% by weight of the overall weight of the layered composite material.

[0032] A third object of the present invention is a process for the regeneration of the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material of the regenerable system for the storage of hydrogen in the solid state, as described above, comprising the steps of:

[0033] a) providing a regenerable system for the storage of hydrogen in the solid state, as described above;

[0034] b) heating the system to a temperature of approximately 155°C so as to destabilize the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material so as to allow the release of pure hydrogen from the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), thereby producing hydrogen (H2);

[0035] c) while maintaining the temperature of approximately 155°C, bringing the system to a pressure not exceeding 30 atm, thereby allowing the regeneration and hence the re-formation of the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNH6).

[0036] According to a preferred embodiment of the process according to the present invention, the regeneration rate in step c) is preferably up to 95%.

[0037] As discussed previously, the hydrogen market is a matter of great complexity. The use of hydrogen as an energy carrier is closely linked to three factors. The first relates to the balance between the cost and processes used for the production thereof. This is an aspect of great relevance, which affects the feasibility of producing black and gray hydrogen, due to the lack of robust infrastructure capable of producing green hydrogen at an affordable cost. The second problem is related to the distribution and use of the hydrogen. To date, the commonly used gas distribution infrastructure has not been designed for the use of hydrogen. Similarly, the use of hydrogen as an energy carrier is extremely limited. The third critical point is safety. Hydrogen-based technologies are currently very limited, and the automotive sector is a perfect example thereof. The first hydrogen vehicle was released in 1976, however, thistechnology has not yet reached a significant breakthrough to date. This is due to the limited safety of hydrogen tanks and the low efficiency thereof. However, the substantial economic effort imposed on hydrogen ecosystems by the European Community has considerably enhanced the application of hydrogen in a sector, such as the automotive sector, particularly in conventional fuel cells. The market for hydrogen-powered fuel cells for vehicles reached a value of 1.5 billion dollars in both 2023 and 2024. Furthermore, in the same year the first type IV hydrogen tank for the automotive sector was released. The great interest in hydrogen in the automotive sector has driven research to new, more efficient and safer storage solutions. The present invention aims to be a solution for producing chemical hydrogen storage tanks for automotive applications, wherein one of the objects is to produce tanks offering greater safety with respect to those using the hydrogen compression technique.

[0038] According to a preferred embodiment of the system according to the present invention, the microcrystalline cellulose used is preferably produced from rice husk via acid hydrolysis mediated by sulfuric acid and neutralized using potassium hydroxide. Potassium hydroxide is also used to remove silica. The final step preferably provides for a treatment with hydrogen peroxide and acetic acid. The prepared microcrystalline cellulose is preferably pressed to produce thin layers, which are subsequently coated on one side with sputered palladium. These layers are then preferably assembled by pressing two of the aforesaid layers with two layers comprising the metal catalyst, which are pressed, in turn, onto the innermost layer, comprising the hydrogenated chemical compound of boron and nitrogen. The pressing procedure is preferably carried out using a hydraulic press with a pressure of 10 tons applied to the microcrystalline cellulose powder or to the ammonia borane powder. Advantageously, the use of microcrystalline cellulose allows exploiting the formation of a network of hydrogen bonds between the fibers of the microcrystalline cellulose, which strengthens the entire structure. Advantageously, the self-assembly process avoids the use of all additives, which may alter or reduce the release of hydrogen during the process. Advantageously, the materials composing the system according to the present invention favor the specific destabilization of ammonia borane at 155°C, allowing pure hydrogen to be released in an amount ranging from 1.1% to 10% by weight. The intermediates produced during this step are trapped between the intermediate layer and the outermost layer due to the reactions between the boron species and the surface rich in hydroxyl-groups of the outermostmicrocrystalline cellulose layer, as well as the formation of adducts on the surface of the intermediate layers due to the presence of amine terminations, interacting with the hydroxyl terminations. Furthermore, advantageously, each intermediate layer acts as a catalyst for the regeneration of the innermost layer when the system is subjected to a pressure below 30 atm at 155°C, achieving a regeneration rate of up to 95%. The selection of the regeneration conditions was advantageously selected to exploit on-off behavior of the system. Advantageously, the layered composite material is capable of releasing hydrogen at 155°C (which can be collected for subsequent uses) and, when closed and pressurized at a pressure compatible with commercial hydrogen tanks, undergoes an almost complete regeneration process by chemically binding the hydrogen. Regeneration under the conditions adopted by the system according to the present invention is advantageously capable of meeting the high-cycling requirements typical of the automotive sector. Advantageously, the material itself is also self-extinguishing and withstands mechanical stress.

[0039] The most advantageous features of the system according to the present invention are:

[0040] • adjustability of the thermal degradation of ammonia borane for the release of hydrogen, preventing the release of partially hydrogenated volatile boron and nitrogen compounds thereby reducing the gravimetric capacity of the hydrogen;

[0041] mechanical integrity of the system;

[0042] release of pure hydrogen at 155 °C up to 10% by weight;

[0043] regenerability over 95% by weight under 30 atm at 155°C;

[0044] storability in environments with air and humidity;

[0045] resistant to fire and combustion;

[0046] reduction of the amount of catalyst required for the regeneration process; volumetric energy density up to 14.1 kWh / L;

[0047] gravimetric energy density up to 1.1 kWh / L.

[0048] The aforesaid advantages may therefore be described thus:

[0049] - controlled reactivity: the system according to the present invention allows finely regulating the thermal decomposition of ammonia borane. Incorporating layers, which may interact with the decomposition products, the system effectively suppresses undesired side reactions. This leads to a release of cleaner hydrogen at arelatively low temperature of 155°C, without the formation of complex by-products containing nitrogen and boron, which typically limit the applicability of ammonia borane. Release at 155°C allows this system to be used under safe conditions, which exceed the maximum temperature of a vehicle’s non-engine environment (130°C). The use of a thin layer of metal catalyst (preferably palladium) is necessary to maximize performance, however, the amount used is negligible and may be applied by 30 seconds of sputering with a current of 50 mA in an Ar atmosphere. The controlled reactivity obtained only allows hydrogen to be produced up to 10% by weight without releasing borazine and high-molecular-weight azaborane, which damage the ability of similar systems to be reused due to the gravimetric storage capacity loss;

[0050] - improved regeneration: the presence of the metal catalyst layer (preferably palladium) significantly improves the regeneration efficiency of ammonia borane. Under controlled conditions (30 atm at 155°C), the system may achieve a regeneration rate of up to 95%. This high efficiency addresses one of the main limitations of conventional ammonia borane systems, which often require complex and less effective regeneration processes. Regeneration at 155°C allows the same release condition to be used without requiring different systems. The pressure used is compatible both with future distribution networks and the pressurized tests currently found on the market;

[0051] - mechanical integrity: the layered design ensures that the composite material maintains the structural integrity thereof during the hydrogen release and regeneration cycles. The use of microcrystalline cellulose provides a robust and stable structure, preventing degradation or breakage of the composite material, which is essential for repeated cycles and long-term use;

[0052] - storage stability: the composite material may be stored in environments with air and low humidity without significant degradation. This improves the practicality thereof for applications in the real world, where environmental control is often less stringent with respect to laboratory environments;

[0053] - reduction in the need for catalyst: the design of the system reduces the amount of catalyst required for the regeneration process, making it cheaper and more environmentally friendly with respect to the traditional methods, which require largeamounts of catalytic material. The intermediate layer comprising a metal catalyst (preferably Pd) used ranges from 5 to 10 nm, and therefore only accounts for a few nanograms of the overall thickness;

[0054] - high energy density: the system offers impressive energy densities, with a volumetric energy density of up to 14.1 kWh / L and a gravimetric energy density of up to 1.1 kWh / L. This makes it highly competitive with the current hydrogen storage technologies, which often struggle to achieve such densities;

[0055] - scalability: the described manufacturing process, including the production of microcrystalline cellulose from rice husks and the use of sputered palladium, indicates a potential for large-scale production. This is crucial for commercial feasibility and widespread adoption in industries such as the automotive industry, where cost and scalability are critical factors. Unlike other works in the field, the present invention is based on materials such as microcrystalline cellulose and ammonia borane, which could be readily produced on a ton / year scale with simple plants, even using waste sources, such as waste biomass, for producing the microcrystalline cellulose. All the methods applied may be transferred to large productions on a relevant industrial scale with little effort;

[0056] - regeneration: an important problem linked to the practical application of ammonia borane in hydrogen storage is the incomplete regeneration observed in many systems. The present invention addresses this problem by incorporating a system comprising a layered composite material, which facilitates the effective release and regeneration of hydrogen. Regeneration takes place in particularly favorable conditions, which correspond both to the release temperature used for the release of pure hydrogen: 155°C, and to the pressure in the commercial hydrogen tanks. The regeneration, which takes place under these conditions is compatible with current hydrogen technology and allows regeneration to be obtained using pure hydrogen instead of hazardous compounds, such as hydrides, hydrazine or liquid ammonia.

[0057] Some preferred embodiments of the present invention are now set out, given by way of indication and not of limitation..The systems according to the present invention have been produced on a laboratory scale. The hydrogen release tests were repeatedly carried out to ensure the reliability of the collected data. Analyses of the composite materials were carried out using thermogravimetric analysis coupled with an infrared spectroscopic detector to accurately evaluate the products resulting from the thermal decomposition. Both the individual layers and the composite material were subjected to different analyses using various techniques, including infrared and Raman spectroscopy, field-emission scanning microscopy, X-ray diffraction, and differential scanning calorimetry, to comprehensively investigate the morphological and chemical structure thereof. The need of using an intermediate layer was demonstrated by testing simple composite materials composed of the two outer layers containing the inner layer therebetween. This test showed that the absence of a sputered metal catalyst (preferably palladium) favored the formation of stable compounds of boron-microcrystalline cellulose, which released ammonia instead of hydrogen. Regeneration tests were carried out in a pressurized batch reactor, and the regenerated composites were characterized in the same way as the original ones evaluating both the morphological and chemical changes.

Claims

CLAIMS1. A regenerable system for the storage of hydrogen in a solid state, comprising a layered composite material comprising at least five layers, wherein the two outermost layers of the layered composite material comprise microcrystalline cellulose, the innermost layer of the layered composite material comprises at least one hydrogenated chemical compound of boron and nitrogen and between each outermost layer of the layered composite material and the innermost layer of the layered composite material there is an intermediate layer comprising a metal catalyst for hydrogenation and dehydrogenation.

2. The system according to claim 1, wherein the hydrogenated chemical compound of boron and nitrogen is ammonia borane (BNtL).

3. The system according to claim 1 or 2, wherein the metal catalyst for hydrogenation and dehydrogenation is palladium, wherein said palladium has been deposited on each intermediate layer by means of the plasma cathodic atomization technique sputering).

4. The system according to any one of claims 1 to 3, wherein the innermost layer of the layered composite material has a weight comprised between 20% and 50% of the total weight of the layered composite material.

5. The system according to any one of claims 1 to 4, wherein the two outermost layers of the layered composite material have a combined weight comprised between 50% and 80% of the total weight of the layered composite material.

6. The system according to any one of claims 1 to 5, wherein each intermediate layer of the layered composite material has a negligible weight relative to the total weight of the layered composite material, with a concentration comprised between 1 ppm and 30 ppm.

7. The system according to any one of claims 1 to 6, wherein the thickness of each intermediate layer of the layered composite material is 30 nm.

8. A process for the production of hydrogen (H2) comprising the steps of:a) providing a regenerable system for the storage of hydrogen in a solid state, according to any one of claims 1 to 7 ;b) heating the system to a temperature of approximately 155°C so as to destabilize the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material so as to allow the release of pure hydrogen from the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), thereby producing hydrogen (H2)) while avoiding the production of partially hydrogenated volatile boron and nitrogen compounds.

9. The process according to claim 8, wherein the H2 produced in step b) is equal to from 1.1% by weight to 10% by weight of the total weight of the layered composite material.

10. A process for the regeneration of the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material of the regenerable system for the storage of hydrogen in the solid state, according to any one of claims 1 to 7, comprising the steps of:a) providing a regenerable system for the storage of hydrogen in a solid state, according to any one of claims 1 to 7 ;b) heating the system to a temperature of approximately 155°C so as to destabilize the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), of the innermost layer of the layered composite material so as to allow the release of pure hydrogen from the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNHe), thereby producing hydrogen (H2);c) while maintaining the temperature of approximately 155°C, bringing the system to a pressure not exceeding 30 atm, thereby allowing the regeneration and hence the reformation of the hydrogenated chemical compound of boron and nitrogen, preferably ammonia borane (BNH6).

11. The process according to claim 10, wherein the regeneration rate in step c) is up to 95%.