Production of dihydrogen from metallurgical-grade silicon

Abstract

The present invention relates to a process for the production of dihydrogen, comprising a step of bringing into contact: - hydrogenated silicon obtained by bringing a silicon substrate into contact with an acid, the silicon substrate having a purity of less than or equal to 99.99%, and - an alkaline solution, whereby dihydrogen is produced.

Description

[0001] Production of dihydrogen from metallurgical silicon

[0002] The present invention relates to the use of hydrogenated silicon, in particular hydrogenated metallurgical silicon, to produce dihydrogen.

[0003] The present invention also relates to a process for the production of dihydrogen from hydrogenated silicon, in particular hydrogenated metallurgical silicon.

[0004] Dihydrogen is a raw material widely used in industry (synthesis of basic molecules such as ammonia, hydrocracking reactions etc...), and is also a source of hydrogen, particularly for fuel cells and hydrogen cars.

[0005] Traditionally, the formation of dihydrogen relies on the catalytic reforming reaction, involving fossil resources. However, the development of renewable energies (wind and photovoltaic energy, for example) has made it possible to consider methods of producing green hydrogen by water electrolysis, and dihydrogen is now one of the most promising renewable energy carriers.

[0006] However, these methods are contingent upon the presence of a system for capturing this renewable energy (typically solar or wind), and on the inherent power variability of these energy sources. Therefore, hydrogen production generally involves a preliminary storage step, either direct or indirect.

[0007] Thus, it is known to store dihydrogen directly in cryogenic or pressurized tanks. This storage system requires the use of storage equipment that is not suitable for applications requiring the use of portable (or mobile) devices, such as mobile phones. Furthermore, cryogenic tanks are hampered by the low efficiency of the dihydrogen liquefaction process. Pressurized tanks, for their part, pose a safety problem.

[0008] Therefore, the storage of dihydrogen as an energy carrier is one of the limitations to the development or miniaturization of fuel cells.

[0009] As described in FR 2 915 742, the inventors previously proposed an alternative source of dihydrogen, using hydrogenated silicon in contact with an alkaline solution to produce dihydrogen. While a technically suitable alternative for dihydrogen production, particularly for portable applications, this solution is not very inexpensive. This is because the silicon substrate used to prepare hydrogenated silicon is, in particular, a bulk silicon substrate with a high degree of purity, and therefore a high production cost. Furthermore, the preparation of hydrogenated silicon requires an electrochemical treatment, typically an anodizing step, to generate porosity within the substrate, which is advantageous for increasing the dihydrogen production rate, and this electrochemical treatment step also has a cost.Furthermore, these requirements regarding silicon quality and processing steps complicate the process and increase its environmental footprint.

[0010] One aim of the invention is therefore to propose a source of dihydrogen enabling the efficient production of dihydrogen as needed, without implementing a storage or restitution step of the aforementioned type, and in particular according to a process presenting a reduced financial and / or environmental cost.

[0011] To this end, the invention relates to a process for the production of dihydrogen, comprising a contacting step:

[0012] - of hydrogenated silicon having a purity less than or equal to 99.99% and a median particle size D50 greater than or equal to 1 pm,

[0013] - with an alkaline solution, which is how dihydrogen is generated.

[0014] The present invention also relates to the use of hydrogenated silicon to provide dihydrogen intended to be recovered and / or valorized, where the hydrogenated silicon is brought into contact with an alkaline solution, said hydrogenated silicon having a purity less than or equal to 99.99% and a median particle size D50 greater than or equal to 1 pm.

[0015] Preferably, hydrogenated silicon is obtained by contacting a silicon substrate with an acid, the silicon substrate having a purity of 99.99% or less.

[0016] Thus, the invention also relates to a process for the production of dihydrogen, comprising a contacting step:

[0017] - of hydrogenated silicon obtained by contacting a silicon substrate with an acid, the silicon substrate having a purity less than or equal to 99.99%,

[0018] - with an alkaline solution, by which dihydrogen is generated. The present invention also relates to the use of hydrogenated silicon to provide dihydrogen intended to be recovered and / or valorized, wherein the hydrogenated silicon is brought into contact with an alkaline solution, said hydrogenated silicon being obtained by contacting a silicon substrate having a purity less than or equal to 99.99% with an acid.

[0019] The entirety of this description applies equally to the process according to the invention and to the use according to the invention.

[0020] Preferably, hydrogenated silicon has a purity of less than or equal to 99.99%, preferably less than or equal to 99.9%, preferably less than or equal to 99.5%, preferably less than or equal to 99%, preferably between 90% and 99.99%, preferably between 98% and 99%.

[0021] Preferably, hydrogenated silicon has a median D50 particle size between 1 pm and 30 mm, preferably between 1 pm and 20 mm, preferably between 1 pm and 15 mm, preferably between 1 pm and 10 mm, preferably between 1 pm and 5 mm.

[0022] The median particle size D50 corresponds to the median equivalent diameter of hydrogenated silicon, preferably hydrogenated silicon particles.

[0023] The median D50 particle size is determined by wet particle size analysis using laser diffraction (ISO 13320:2020) and image analysis (ISO 13322-1:2014) for particles having a D50 of 2000 pm or less, or by sieving particle size analysis if the particles have a median D50 particle size strictly greater than 2000 pm (for example according to ISO 13320).

[0024] As mentioned above, the hydrogenated silicon of the process or use is preferably obtained by contacting a silicon substrate with an acid; preferably with: the silicon substrate having a purity less than or equal to 99.99%; and / or the silicon substrate being in powder form, and preferably having a median particle size D50 between 1 pm and 300 pm.

[0025] Thus, preferably, the process according to the invention comprises a step of preparing hydrogenated silicon including contacting a silicon substrate with an acid, said step of preparing hydrogenated silicon being devoid of electrochemical treatment; preferably with;

[0026] - the silicon substrate has a purity less than or equal to 99.99%; and / or - the silicon substrate is in powder form, and preferably has a median particle size D50 between 1 pm and 300 pm.

[0027] Preferably, the silicon substrate has a purity of less than or equal to 99.9%, preferably less than or equal to 99.5%, preferably less than or equal to 99%, preferably between 90% and 99.99%, preferably between 98% and 99%.

[0028] The purity of the silicon (or hydrogenated silicon) substrate indicates the molar content of silicon atoms relative to all the atoms in the substrate (or hydrogenated silicon), and is therefore related to the amount of impurities. Typically, a silicon (or hydrogenated silicon) substrate containing at most 10 19 crrr 3 atomic impurities (which is not according to the invention) have a purity of at least 99.999%, this purity being superior to the purity of a silicon substrate (or hydrogenated silicon) (according to the invention) having a purity less than or equal to 99.99%.

[0029] Specifically, the silicon substrate can be a metallurgical-grade silicon substrate, or metallurgical silicon. Metallurgical silicon is sometimes denoted MG-silicon, MG meaning "metal grade".

[0030] Preferably, hydrogenated silicon is in powder form.

[0031] Preferably, the hydrogenated silicon powder has a median particle size D50 between 0.050 pm and 300 pm, preferably between 1 pm and 300 pm, preferably between 1 pm and 50 pm, preferably between 1 pm and 15 pm.

[0032] Preferably, the silicon substrate is in powder form.

[0033] Preferably, the silicon powder has a median particle size D50 between 0.050 pm and 300 pm, preferably between 1 pm and 300 pm, preferably between 1 pm and 50 pm, preferably between 1 pm and 15 pm.

[0034] The median particle size D50 is determined by wet particle size analysis using laser diffraction (ISO 13320:2020 standard) and image analysis (ISO 13322-1:2014 standard).

[0035] This specific particle size distribution of hydrogenated silicon and the silicon substrate distinguishes them from nanoparticles. Indeed, nanoparticles are objects whose dimensions are typically between 1 nm and 100 nm, and in particular whose D50 is between 1 nm and 100 nm.

[0036] The use of powder allows, among other things, an increase in the specific surface area of ​​the silicon substrate and, for a given volume, results in a greater quantity of hydrogen atoms present on the surface of the hydrogenated silicon powder, and therefore a higher hydrogen production rate. However, the smaller the particle size of the silicon substrate, the greater the specific surface area, and therefore the greater the amount of silica that must be removed by acid treatment, which reduces the final yield. The amount of acid required to prepare the hydrogenated silicon powder is also greater. The median particle size of the powders is therefore a compromise between, on the one hand, the hydrogen production rate and, on the other hand, the gross yield for the same quantity of silicon substrate and the quantities of acid to be used and resulting by-products to be treated after the hydrogenated silicon preparation.

[0037] According to another embodiment, hydrogenated silicon is in the form of granules, and has a median D50 particle size between 0.5 mm and 30 mm, preferably between 1 mm and 20 mm, preferably between 2 mm and 15 mm, preferably between 2 mm and 10 mm, preferably between 2 mm and 5 mm.

[0038] Hydrogenated silicon in granular form improves the compactness of hydrogenated silicon and therefore improves the amount of dihydrogen produced per volume of hydrogenated silicon involved in the process or use.

[0039] Aggregates may also contain a binder, or be binderless. Preferably, aggregates are binderless.

[0040] Examples of binders suitable for the invention are: cellulose (in particular microcrystalline), cellulose derivatives (such as methylcellulose, carboxymethylcellulose and its salts, hydroxypropylcellulose and hydroxypropylmethylcellulose), starches (in particular pre-gel), molasses, lime (Ca(OH)2), sodium silicate, polymer binders.

[0041] Thus, preferably according to this embodiment, hydrogenated silicon is obtained by: a / contacting a silicon substrate in powder form with an acid, to obtain a hydrogenated silicon powder, preferably with;

[0042] - the silicon substrate has a purity of 99.99% or less, preferably 99.5% or less, preferably between 90% and 99.99%; and / or

[0043] - the silicon substrate has a median particle size D50 between 1 pm and 300 pm, and

[0044] - b / compaction of hydrogenated silicon powder.

[0045] Thus, according to this embodiment, the process of the invention preferably includes a step of preparing hydrogenated silicon comprising: a / contacting a silicon substrate in powder form with an acid, said step of preparing hydrogenated silicon being devoid of electrochemical treatment to obtain a hydrogenated silicon powder, preferably with;

[0046] - the silicon substrate has a purity of 99.99% or less, preferably 99.5% or less, preferably between 90% and 99.99%; and / or

[0047] - the silicon substrate has a median particle size D50 between 1 pm and 300 pm, and

[0048] - b / the compaction of hydrogenated silicon powder to obtain hydrogenated silicon in the form of granules.

[0049] The compaction of hydrogenated powder typically involves compressing the hydrogenated silicon powder to obtain, for example, hydrogenated silicon ribbons or sheets, which are then broken or granulated to produce granules. The granules may have a homogeneous or non-homogeneous morphology.

[0050] The compaction of hydrogenated silicon powder can, for example, be carried out by a roller compactor.

[0051] Between step a / of contacting a silicon substrate in powder form with an acid and step b / of compaction, the process may further include a step a' / of mixing the hydrogenated silicon powder with a binder. Step b / then corresponds to the compaction of the mixture obtained in step a' / of mixing.

[0052] The possible binder is preferably as defined above.

[0053] According to the invention, a reaction of an alkaline solution on hydrogenated silicon is implemented.

[0054] The alkaline solution reacts on the silicon-hydrogen layer on the surface of the hydrogenated silicon, releasing dihydrogen while forming a new silicon-hydrogen layer.

[0055] The production of dihydrogen according to the invention can be schematically summarized by the following reaction (I):

[0056] -Si-Si-H + 4H2O -> -Si-H + Si(OH)4+ 2H2(I)

[0057] One advantage of using the aforementioned reaction is that it allows for the production of dihydrogen in a single step, resulting in a lower production cost than devices requiring two or more steps, which generally use often expensive intermediate compounds. Furthermore, reaction (I) simultaneously induces silicon reactivation by reforming silicon-hydrogen bonds on the surface. Based on this, dihydrogen can be produced again on demand by repeating reaction (I).

[0058] Furthermore, thanks to the use of reaction (I), dihydrogen is supplied without having to resort to a storage step prior to release.

[0059] One advantage of the process and use of the invention is that all of the hydrogenated silicon is available to react with the alkaline solution and thus generate dihydrogen, unlike some prior art alternatives in which only the surface of the material is used to store dihydrogen. Therefore, in the process and use of the invention, the amount of dihydrogen available per unit of time depends, in particular, on the amount of silicon present. The amount of dihydrogen is approximately two moles of dihydrogen per mole of hydrogenated silicon, or about 1.6 L of dihydrogen per gram of hydrogenated silicon at atmospheric pressure and room temperature.

[0060] The rate of dihydrogen production is primarily related to the pH and temperature of the alkaline solution, as well as the particle size of the hydrogenated silicon.

[0061] The process preferably includes a step of recovery and / or valorization of the dihydrogen formed, for example the use of dihydrogen as fuel.

[0062] Preferably, the alkaline solution is an aqueous alkaline solution having a pH greater than or equal to 10, preferably between 10 and 14, preferably between 11 and 14.

[0063] Preferably, the alkaline solution is an aqueous solution of NaOH and / or KOH and / or NH4OH.

[0064] Preferably, the water in the alkaline solution can be mineral water, salt water, or distilled water.

[0065] In the process and use of the invention, the contact temperature of the alkaline solution and the hydrogenated silicon is generally between approximately 0°C and approximately 80°C, preferably between 15°C and 65°C. According to one embodiment, the contact temperature of the alkaline solution and the hydrogenated silicon is between 10°C and 45°C, preferably between 15°C and 30°C, and preferably between 15°C and 25°C. According to another embodiment, the contact temperature of the alkaline solution and the hydrogenated silicon is between 40°C and 80°C, preferably between 50°C and 65°C. The reaction preferably takes place at atmospheric pressure or at slightly higher pressures, generally less than or equal to 3 bar, and preferably between 1 bar and 2 bar.

[0066] Preferably, the acid in the hydrogenated silicon preparation step is hydrofluoric acid.

[0067] After contact with the acid, all or part of the surface of the silicon substrate, in particular the silicon powder, contains silicon atoms linked to hydrogens, (surface -Si-H groups), suitable for carrying out the aforementioned reaction (I).

[0068] Preferably, the process according to the invention includes a step for preparing hydrogenated silicon comprising contacting the silicon substrate with an acid. Preferably, this step for preparing hydrogenated silicon is free of electrochemical treatment, such as electrochemical anodizing.

[0069] Electrochemical anodizing performed on a silicon substrate (e.g. monocrystalline, polycrystalline or amorphous) typically allows obtaining a silicon substrate that is both mesoporous and / or microporous and hydrogenated, which increases the specific surface area of ​​the substrate and therefore its hydrogen storage capacity.

[0070] Preferably, the process according to the invention further comprises a step of grinding a silicon substrate with a particle size strictly greater than 300 µm until a powder is obtained with a median particle size D50 between 0.050 µm and 300 µm, preferably between 1 µm and 50 µm, and preferably between 1 µm and 15 µm. This grinding step precedes the step of preparing the hydrogenated silicon. This step can be carried out by any technique known to those skilled in the art.

[0071] Once all the hydrogenated silicon has reacted, a solution including Si(OH)4 is obtained.

[0072] The Si(OH)4 formed can advantageously be recycled and / or dehydrated or diluted to serve, for example, as a fertilizer.

[0073] The dihydrogen produced by the process according to the invention is intended to be used in any application requiring the use of dihydrogen.

[0074] For example, it can be used: - to power fuel cells and produce electricity, particularly for mobile applications,

[0075] - as fuel, particularly in internal combustion engines, burners (camping stoves),

[0076] - as a reagent, for example for decarbonizing internal combustion engines.

[0077] The present invention therefore also relates to the use of the process according to the invention to produce dihydrogen for (or the invention relates to the use of the dihydrogen produced by the process according to the invention to) produce electricity, in particular for (or to) power a fuel cell, the fuel cell preferably being used for a mobile application such as a portable electronic device or a vehicle (car, bicycle, for example) or used in a stationary installation, for example for supplying buildings with electricity.

[0078] The process or use of hydrogenated silicon according to the invention is therefore in particular for producing dihydrogen intended for the production of electricity, in particular intended to power a fuel cell, preferably used for a nomadic application such as a portable electronic device or a vehicle (car, bicycle, for example) or used in a stationary installation, for example for supplying buildings with electricity.

[0079] The invention therefore also relates to a method of electricity production, comprising a stage of producing dihydrogen by implementing the dihydrogen production method according to the invention, and a stage of bringing this dihydrogen into contact with dioxygen, for example by means of a fuel cell.

[0080] The present invention also relates to the use of the process according to the invention to produce dihydrogen as (or the invention relates to the use of the dihydrogen produced by the process according to the invention as) a reagent, in particular as a reagent in a chemical synthesis reaction, for example for the production of ammonia, methane or methanol, or in a catalytic cracking reaction or in a hydrogenation reaction, or as a reagent in a process for descaling a heat engine.

[0081] The process or use of hydrogenated silicon according to the invention is therefore particularly for producing dihydrogen as a reagent, in particular as a reagent in a chemical synthesis reaction, for example for the production of ammonia, methane or methanol, in a catalytic cracking reaction or in a hydrogenation reaction, or as a reagent in a thermal engine decarbonizing process.

[0082] The invention therefore also relates to a chemical synthesis process for a product, comprising a step of producing dihydrogen by implementing the dihydrogen production process according to the invention, and a step of contacting the dihydrogen produced with a second reagent intended to react with the dihydrogen to form the product

[0083] The present invention also relates to the use of the process according to the invention to produce dihydrogen as (or the invention relates to the use of the dihydrogen produced by the process according to the invention as) fuel, to produce energy and in particular heat, particularly in internal combustion engines or burners.

[0084] The process or use of hydrogenated silicon according to the invention is therefore particularly for producing dihydrogen as a fuel, especially in internal combustion engines or burners.

[0085] The invention therefore also relates to a process for producing energy, in particular heat, comprising a stage of producing dihydrogen by implementing the process of producing dihydrogen according to the invention, and a stage of burning this dihydrogen.

[0086] According to another aspect, the invention relates to a fuel cell comprising a dihydrogen-operating anode associated with a dihydrogen supply device, this device comprising hydrogenated silicon brought into contact with an alkaline solution to generate dihydrogen by implementing the process according to the invention.

[0087] Hydrogenated silicon, when brought into contact with the alkaline solution, allows, as illustrated in equation (I), the generation of two equivalents of dihydrogen by regenerating a silicon-hydrogen bond on the surface of the silicon.

[0088] An advantage of the process according to the invention is the in-situ regeneration of hydrogenated silicon during fuel cell operation. Consequently, for the same quantity of silicon, the amount of available dihydrogen is greater than that of a device containing only chemisorbed dihydrogen on the surface of the silicon substrate, particularly a porous silicon substrate. The fuel cell operating time therefore depends on the initial quantity of silicon substrate. Preferably, the dihydrogen supply device for feeding the anode of the fuel cell according to the invention comprises a reservoir with a first compartment partially or completely filled with hydrogenated silicon. Preferably, this first compartment includes a first zone containing the hydrogenated silicon and a second zone in contact with the anode, designed to receive the formed dihydrogen.

[0089] According to a preferred mode, the reservoir is of the interchangeable type and therefore plays the role of both a hydrogenated silicon loading system and a recovery system for by-products (in particular Si(OH)4) from reaction (I)).

[0090] In one embodiment, the fuel cell's hydrogen supply system includes a hydrogenated silicon loading system. This system allows for the initial introduction of hydrogenated silicon. Furthermore, additional hydrogenated silicon can be reintroduced into the fuel cell's hydrogen supply system via this loading system when the initially present hydrogenated silicon is completely consumed or when it is consumed beyond a certain threshold, for example, beyond 75%, or even 85%, or ideally 95% of the initially present hydrogenated silicon. The hydrogenated silicon loading system can be an external loading system or a system allowing the exchange of a cartridge containing the hydrogenated silicon.

[0091] Hydrogenated silicon can be contained in a removable container, for example a cartridge that can be hermetically snapped onto the fuel cell.

[0092] Most often, the cathode of the fuel cell operates with dioxygen. According to this embodiment, the anode and cathode preferably comprise a medium diffusing dihydrogen and dioxygen, as well as a catalyst and a proton conductor.

[0093] The diffusing medium is also an electronic conductor and is, for example, made of woven carbon fibers containing porous graphite particles. In this case, gas molecules pass through the woven fibers, and electrons are carried by the carbon fibers. In another embodiment, it is also made of a gas-permeable crosslinked polymer such as PDMS (polydimethylsiloxane) loaded with porous graphite particles.

[0094] The catalyst consists of finely divided platinum incorporated into porous graphite particles.

[0095] According to one embodiment, the catalyst consists of platinum nanoparticles (typically with dimensions between 2 and 50 nm) coated with proton-conducting molecules by chemical grafting and dispersed in a matrix, such as PDMS, permeable to water and gases at a concentration above the percolation threshold to allow electronic and proton conductivity.

[0096] The proton conductor is, for example, an ionomer such as Nation® or consists of molecules bearing groups identical to those used to create the membrane and grafted onto the surface of the catalyst grains. The proton conductor is a molecule or macromolecule containing at least one group capable of capturing and then releasing a proton so that it circulates within the generator. The proton-capturing group is chosen from among the sulfonate (-SCh') or carboxylate (-COO-) groups. In particular, it is advantageous to use a molecule or macromolecule with a fluorinated backbone, which notably increases proton mobility.

[0097] Oxygen is supplied, for example, from a reservoir of air, preferably enriched air, a reservoir containing pure oxygen, or ambient air. The oxygen is transported, for example, via a pipe or equivalent from the reservoir to the cathode. The cathode is equipped with an opening through which the pipe or equivalent is attached.

[0098] The overall functioning of the battery is summarized by the following reaction:

[0099] 2H2 + O2 -> 2H2O (II)

[0100] The battery may include a membrane, for example a porous silicon membrane whose internal surface is chemically grafted with proton conductors, in particular molecules bearing at least one sulfonate (-SOa') or carboxylate (-COO-) group.

[0101] In another embodiment, the membrane is made of porous silicon whose pores are filled with an ionomer such as Nation®. The membrane conducts the protons resulting from the operation of the fuel cell but is impermeable to hydrogen and oxygen gas.

[0102] According to an advantageous embodiment, the membrane is an anionic membrane as described in application EP 3050145, or an anionic membrane as described in application EP 4052316, or an ionic conducting membrane as described in application FR 3146240.

[0103] The invention will be further illustrated by reading the examples that follow, given only as a non-limiting example.

[0104] EXAMPLES Example 1: Preparation and characterization of hydrogenated silicon powders

[0105] When in contact with atmospheric oxygen, silicon forms silica SiO2. Therefore, all silicon powder includes a layer of SiO2 on the surface of each particle, which must be removed in favor of Si-SiH bonds, for example by treating the metallurgical silicon powder in a hydrofluoric acid bath.

[0106] In this example, four metallurgical-grade silicon powders were treated with hydrofluoric acid according to the following protocol: the powder is weighed in a polypropylene beaker and then covered with an excess of hydrofluoric acid (40 wt%) in deionized water. The silica is removed according to the reactions below:

[0107] SiO2+ 4ffl* — * SiF^ + 2H2O (1) 1619 - 2 * 285 + 910 I 4 * 273 = -187 kj / mol

[0108] SiF4+ 2HF H2SiF6+ 2H2O (2) 2114 - 2 ® 285 I 1615 + 2 * 273 = -525 kJ / mol which gives overall:

[0109] SiO2+ 6HF H2SiF6+ 2H2O (3)

[0110] AAF = -2114 - 2 * 285 + 910 + 6 * 273 = -137 kj / mol

[0111] Initially, the powder and bubbles swell, corresponding to the formation of SiF4 gas in reaction (1). This reaction is exothermic, as the beaker heats up. The silica then dissolves according to reaction (2). The metallurgical silicon powder grains are thus freed from their oxidation layer and react with hydrofluoric acid to form a Si-Si-H passivation layer. The hydrogenated powder is then dried on a hot plate to remove the excess hydrofluoric acid solution and is stored protected from moisture and oxygen.

[0112] The hydrogenated powders are then characterized by determining their median particle size D50 according to the method described in the description. Their bulk density is also determined by calculating the ratio between the mass of a given quantity of powder and the volume that this powder occupies in a graduated container.

[0113] The results obtained are presented in the following table:

[0114] [Table 1]

[0115] Example 2: Generation of dihydrogen from hydrogenated silicon powders

[0116] The hydrogenated silicon powders of Example 1 were used to generate dihydrogen according to the process of the present invention, according to the following reaction:

[0117] Si - SiH + 4H2O Si - H + Si(OH)4+ 2H2

[0118] = 0 + (-1342) - 4 » (-285)

[0119] = -198 kJ / mol

[0120] The process was implemented according to the following protocol:

[0121] 0.30 g of hydrogenated silicon powder is weighed into a flask. This flask is stoppered and connected to an inverted graduated tube filled with water. Approximately 100 mL of a potassium hydroxide solution with a pH between 11 and 14 is added, and the flask is then sealed. The KOH solution may or may not be heated, and its pH is more or less basic (between 11 and 14). The solution is stirred, and hydrogen gas gradually fills the graduated tube, allowing the total volume of hydrogen produced to be measured. The hydrogen gas flow rate over time was also measured by filming the graduated tube during the reaction (as it gradually filled with gas) and analyzing the images.

[0122] This protocol was implemented on the four powders of Example 1, at different temperatures. The reaction yield was calculated based on a complete reaction with excess water, according to the following calculation:

[0123] The results obtained are presented in the following table: [Table 2]

[0124] These results illustrate that the smaller the median particle size of the hydrogenated silicon powder, the higher the maximum flow rate. The particle size of the hydrogenated silicon powder therefore influences the kinetics of the dihydrogen production reaction. Temperature also affects the flow rate, which increases by at least a factor of 10 when rising from approximately 16°C to approximately 58°C. However, the total amount of dihydrogen formed depends primarily on the amount of silicon and is therefore similar for each trial (within measurement uncertainties).

Claims

DEMANDS 1. Process for the production of dihydrogen, comprising a contacting step: - of hydrogenated silicon having a purity less than or equal to 99.99% and a median particle size D50 greater than or equal to 1 pm, - with an alkaline solution, which is how dihydrogen is generated.

2. Use of hydrogenated silicon to provide dihydrogen intended for recovery and / or valorization, wherein the hydrogenated silicon is brought into contact with an alkaline solution, said hydrogenated silicon having a purity less than or equal to 99.99% and a median particle size D50 greater than or equal to 1 pm.

3. A method according to claim 1, or a use according to claim 2, wherein the hydrogenated silicon has a purity of less than or equal to 99.9%, preferably less than or equal to 99.5%, preferably between 90% and 99.99%.

4. Method according to claim 1 or 3, or use according to claim 2 or 3, wherein the hydrogenated silicon has a median particle size D50 of between 1 pm and 30 mm, preferably between 1 pm and 20 mm, preferably between 1 pm and 15 mm, preferably between 1 pm and 10 mm, preferably between 1 pm and 5 mm.

5. A process according to claim 1 or 3 or 4, or a use according to any one of claims 2 to 4, wherein hydrogenated silicon is obtained by contacting a silicon substrate with an acid; preferably with: the silicon substrate having a purity less than or equal to 99.99%; and / or the silicon substrate is in powder form, and preferably has a median particle size D50 between 1 pm and 300 pm.

6. A process according to any one of claims 1 or 3 to 5, comprising a step of preparing hydrogenated silicon including contacting a silicon substrate with an acid, said step of preparing hydrogenated silicon being devoid of electrochemical treatment; preferably with; - the silicon substrate has a purity of 99.99% or less; and / or - the silicon substrate is in powder form, and preferably has a median particle size D50 between 1 pm and 300 pm.

7. A method according to any one of claims 1 or 3 to 6, or a use according to any one of claims 2 to 5, wherein the hydrogenated silicon is in powder form, and has a median particle size D50 of between 1 pm and 300 pm, preferably between 1 pm and 50 pm, preferably between 1 pm and 15 pm.

8. A method according to any one of claims 1 or 3 to 7, or a use according to any one of claims 2 to 5 or 7, wherein the hydrogenated silicon is in the form of granules, and has a median particle size D50 of between 0.5 mm and 30 mm, preferably between 1 mm and 20 mm, preferably between 2 mm and 15 mm, preferably between 2 mm and 10 mm, preferably between 2 mm and 5 mm.

9. A process or use according to claim 8, wherein hydrogenated silicon is obtained by: a / contacting a silicon substrate in powder form with an acid, to obtain hydrogenated silicon powder, preferably with; - the silicon substrate has a purity of 99.99% or less, preferably 99.5% or less, preferably between 90% and 99.99%; and / or - the silicon substrate has a median particle size D50 between 1 pm and 300 pm, and - b / compaction of hydrogenated silicon powder.

10. A process according to claim 8 or 9, comprising a step of preparing hydrogenated silicon comprising: a / contacting a silicon substrate in powder form with an acid, said step of preparing hydrogenated silicon being devoid of electrochemical treatment to obtain a hydrogenated silicon powder, preferably with; - the silicon substrate has a purity of 99.99% or less, preferably 99.5% or less, preferably between 90% and 99.99%; and / or - the silicon substrate has a median particle size D50 between 1 pm and 300 pm, and - b / the compaction of hydrogenated silicon powder to obtain hydrogenated silicon in the form of granules.

11. Method according to claim 5 or 6 or 9 or 10, or use according to claim 5 or 9, wherein the acid is hydrofluoric acid.

12. A method according to any one of claims 1 or 3 to 11 or a use according to any one of claims 2 to 5 or 7 to 9, wherein the alkaline solution is an aqueous alkaline solution having a pH greater than or equal to 10, preferably is an aqueous solution of NaOH and / or KOH and / or NH4OH.

13. Use of the process according to any one of claims 1 or 3 to 12 to produce dihydrogen for the production of electricity, in particular for powering a fuel cell, preferably a fuel cell used for a mobile application or in a stationary installation.

14. Use of the process according to any one of claims 1 or 3 to 12 to produce dihydrogen as a reactant, in particular as a reactant in a chemical synthesis reaction.

15. Use of the process according to any one of claims 1 or 3 to 12 to produce dihydrogen as a fuel, to produce energy and in particular heat.

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