Bio-based carbon-TiFe composite material, its preparation process and its use for hydrogen storage

Abstract

The present invention relates to a bio-based carbon-TiFe composite material comprising a carbonaceous material and TiFe particles dispersed within said carbonaceous material, its preparation process, and its use for hydrogen storage. Figure to be published: Figure 1

Description

Title of the invention: Bio-based carbon-TiFe composite material, its preparation process and its use for hydrogen storage

[0001] The present invention relates to a bio-based carbon-TiFe composite material comprising a carbon material and TiFe particles dispersed in said carbon material, its preparation process and its use for hydrogen storage.

[0002] For several decades, the fear of dwindling fossil fuel reserves (e.g., coal, crude oil, natural gas) combined with climate change has paved the way for the research and / or use of new, cleaner energy sources. These energies can be renewable, such as wind turbines or solar panels, and / or non-emitting of greenhouse gases. Hydrogen is both sustainable and environmentally friendly, and it constitutes a promising alternative energy carrier to crude oil due to its high intrinsic energy density and clean combustion products (i.e., water). However, because of its lightness and gaseous nature, it presents storage challenges. The storage of gaseous hydrogen under high pressure is primarily hampered by the low specific gravity and volumetric capacity of this system.In addition to these risks, the use of high pressures presents significant challenges. Therefore, this solution is generally not recommended for use in vehicles. Several technologies already exist to improve hydrogen storage. These include physical methods such as cryogenics or compression, which induce hydrogen liquefaction or pressurization, and / or chemical methods that promote physisorption or chemisorption, such as the use of an organic liquid carrying hydrogen or a metal hydride. In the latter case, the hydrogen is chemically bonded to the metal hydrides. These bonds are much stronger than the physical bonds involved in metal hydrides. Consequently, more energy is required to release the chemically bound hydrogen. On the other hand, the stronger bond allows hydrogen to be stored at high density, even under ambient conditions.As an example, intermetallic hydrides have been proposed for hydrogen storage. These can be alloys conforming to the formula AxByHz, in which element A binds hydrogen strongly, while element B binds hydrogen weakly, resulting in hydrogen storage properties intermediate between those of its constituent elements. In practice, these are variants of a relatively limited number of metal hydride structures. Intermetallic compounds are used in hydrogen storage applications, specifically those with AB5, AB2, and AB crystal structures. TiFe is an example of an intermetallic compound. However, the main drawback of TiFe is its high activation energy requirement. This energy is generated under challenging thermodynamic conditions of temperature and hydrogen pressure (i.e., up to 400°C and several tens of bars of hydrogen pressure), where activation occurs through multiple absorption / desorption cycles. This high-energy and time-consuming activation method necessitates the design of specialized reactors, which is not feasible on an industrial scale.

[0003] To improve the activation properties of TiFe, various strategies have been implemented over the past few decades. These include the partial substitution of Ti or Fe with different metals to improve the thermodynamic properties (i.e., entropy and enthalpy) of the alloys. Partial substitutions using transition metals such as zirconium, chromium, or copper, as well as manganese, have already been implemented. Another method used to improve the properties of the TiFe alloy involves modifying the stoichiometric ratio between Ti and Fe, for example, by adding more titanium to the initial 1:1 ratio, with or without the addition of another element by partial substitution or doping with another metal. Another strategy involves attempting to supply TiFe in the form of nano-objects. For example, Kobayashi et al.[Nanoscale Advances, 2021, 3, 18, 5125-5432] used two distinct methods to generate TiFe nanostructures: one with FeTiO3 and the other using iron nitrate in water combined with TiO2 nanoparticles. Both methods were followed by heat treatment with molten salts to obtain the desired structures. No examples of hydrogen storage using these nanostructures are described.

[0004] Thus, the object of the present invention is to overcome the drawbacks of the prior art, and more particularly, to provide an economical material with improved hydrogen storage properties. Another object of the invention is to provide a simple and economical process for producing a material with improved hydrogen storage properties, said process being implemented with abundant and / or inexpensive raw materials and / or renewable raw materials; and limiting or at least reducing the use of toxic reagents. In particular, it is necessary to promote a sustainable development approach by valorizing industrial waste, without negatively impacting other priority uses of these resources, such as human or animal food, and without further impact on the environment.

[0005] Bio-based carbon-TiFe composite material

[0006] The invention has as its first object a bio-based carbon-TiFe composite material, characterized in that it is a porous monolithic material and in that it comprises a carbon material and TiFe particles dispersed in said carbon material.

[0007] The bio-based carbon-TiFe composite material of the invention is a porous monolithic material.

[0008] In the present invention, the term "monolithic" refers to a solid object having an average dimension of at least 1 mm, and preferably of at least 3 mm.

[0009] In the present invention, the term "porous" refers to a material comprising pores.

[0010] Preferably, the bio-based carbon-TiFe composite material according to the invention is an essentially microporous material comprising micropores, mesopores and optionally macropores.

[0011] The bio-based carbon-TiFe composite material of the invention comprises a hierarchical mesoporous / microporous structure. In other words, the bio-based carbon-TiFe composite material has a cellular structure exhibiting at least dual porosity.

[0012] In the present invention, the term "essentially microporous" means that the material exhibits a nitrogen sorption isotherm of type I or a mixture of types I and IV.

[0013] In the present invention, "micropores" means pores whose size is less than 2 nm.

[0014] In a particularly preferred embodiment, the micropores of the bio-based carbon-TiFe composite material have a size between 0.4 and less than about 2 nm.

[0015] In the present invention, "mesopores" means pores whose size varies from 2 to 50 nm.

[0016] In a preferred embodiment, the mesopores of the bio-based carbon-TiFe composite material have a size ranging from approximately 2 to 50 nm, particularly preferably from approximately 2 to 40 nm, and more particularly preferably from approximately 2 to 30 nm.

[0017] In a preferred embodiment, the bio-based carbon-TiFe composite material comprises interconnected micropores and mesopores. In other words, the micropores are interconnected with each other, the mesopores are interconnected with each other, and the micropores are interconnected with the mesopores.

[0018] In the invention, mesoporosity and microporosity can be quantified and / or measured by a nitrogen adsorption-desorption technique using the BET calculation method (Brunauer, Emmett and Teller model or BET method) which aggregates mesoporosity and microporosity (S. Brunauer, PH Emmet, E. Teller, Journal of the American Chemical Society, 1938, 60, 2, 309-319); and by the BJH calculation method (Barrett, Joyner and Halenda, Journal of the American Chemical Society, 1951, 73, 373-380), according to which the segregation between microporosity and mesoporosity becomes effective, the BJH method considering only pores greater than 1.5 angstroms.

[0019] The bio-based carbon-TiFe composite material may further comprise macropores.

[0020] In the present invention, the term "macropores" refers to pores whose size is greater than 50 nm.

[0021] In a preferred embodiment, the macropores of the bio-based carbon-TiFe composite material have a size ranging from approximately 0.5 to 300 pm, particularly preferably from approximately 0.5 to 200 pm, and even more particularly preferred from approximately 1 to 100 pm.

[0022] Macropores can be identified by scanning electron microscopy (SEM) and / or by mercury intrusion measurements.

[0023] In a preferred embodiment, the bio-based carbon-TiFe composite material has a porosity ranging from approximately 50 to 75%.

[0024] In the invention, porosity is measured by mercury intrusion porosimetry.

[0025] In a preferred embodiment, the bio-based carbon-TiFe composite material has a specific surface area ranging from approximately 500 to 1500 m2 / g, particularly preferably from approximately 800 to 1400 m2 / g, and more particularly preferred from approximately 1000 to 1300 m2 / g.

[0026] In the invention, the specific surface area can be measured by nitrogen adsorption and data processing using the BET (Brunauer-Emmet-Teller) method. This is referred to as BET specific surface area.

[0027] In a preferred embodiment, the bio-based carbon-TiFe composite material has an apparent skeleton density of approximately 0.15 to 0.25 g.ml1, and particularly preferably of approximately 0.17 to 0.20 g.ml1.

[0028] In the invention, the apparent skeleton density is measured by mercury intrusion porosimetry.

[0029] The composite material of the invention comprises a carbonaceous material and TiFe particles dispersed within said porous monolithic carbonaceous material. The porous monolithic carbonaceous material imparts to the composite material the porosity characteristics defined above. Furthermore, it acts as a support to accommodate the TiFe particles and promote their heterogeneous dispersion within said composite material.

[0030] The carbon material is preferably a porous monolithic material.

[0031] The composite material of the invention is a bio-based carbon-TiFe material. In other words, the carbon in the composite material comes from biomass or raw materials of plant and / or animal origin, preferably plant-based (and not from fossil or petrochemical sources). Specifically, it is obtained by extracting biomass or raw materials of plant and / or animal origin, preferably plant-based; or obtained through reactions applied to biomass or raw materials of plant and / or animal origin, preferably plant-based. In contrast, a product "of fossil or petrochemical origin" refers to any product manufactured at least partially from organic compounds derived from petroleum or coal, or petroleum or coal derivatives.

[0032] In a particular embodiment, the bio-based carbon-TiFe composite material of the invention is a self-supporting material. It therefore does not require support and can be used directly as a material in applications such as hydrogen storage.

[0033] TiFe particles are particles comprising at least one TiFe alloy (i.e. molar ratio Ti / Fe = 1 / 1).

[0034] The TiFe particles preferably have at least one dimension of at most about 20 pm, particularly preferably of at most about 10 pm, more particularly preferred of at most about 1 pm, and even more particularly preferred of at most about 500 nm.

[0035] In the invention, the size or dimensions of the particles are determined by scanning electron microscopy or by image analysis.

[0036] According to a preferred embodiment of the invention, the composite material comprises two types of TiFe particle populations, preferably a first population of TiFe particles in the form of elongated particles such as, for example, rods, wires, or needles, and a second population of TiFe particles in the form of isotropic particles such as, for example, spheres.

[0037] The elongated TiFe particles (first population) preferably have: - a length (L1), extending along a principal elongation direction, - two dimensions (D1) and (D2), called orthogonal dimensions, extending along two transverse directions orthogonal to each other and orthogonal to said principal elongation direction, said orthogonal dimensions (D1, D2) being smaller than said length (L1), and - two ratios (Fl) and (F2), called aspect ratios, between said length (Ll) and each of the two orthogonal dimensions (Dl) and (D2).

[0038] The expression "aspect ratio" means the ratio between the length (Ll) of an elongated particle, and one of the two orthogonal dimensions (Dl, D2) of said elongated particle.

[0039] According to a preferred embodiment, the elongated particles are such that: - Dl ranges from approximately 0.2 to 1 pm, and particularly preferably from approximately 0.5 to 0.7 pm, - D2 ranges from approximately 0.2 to 1 pm, and particularly preferentially from approximately 0.5 to 0.7 pm, - It is greater than or equal to approximately 5 pm, and particularly preferably goes from approximately 5 to 100 pm.

[0040] According to a preferred embodiment, said aspect ratios (Fl, F2) are greater than or equal to 5, and preferably ranging from 5 to 500.

[0041] When the two orthogonal dimensions (D1, D2) of a particle are the diameter (D) of its transverse cross-section. We then speak of a "rod" or a "wire".

[0042] When the diameter (D) varies as a function of the length Ll of the particle, we then speak of a “needle”.

[0043] According to a preferred embodiment, the isotropic particles (second population) have a size ranging from about 500 nm to about 20 pm, and particularly preferably from about 100 nm to about 10 pm.

[0044] Such particles may have an aspect ratio less than or equal to 1, and preferably of 0.95.

[0045] The composite material of the invention preferably comprises approximately 70 to 98 mole percent of carbon, and particularly preferably approximately 90 to 97 mole percent of carbon, relative to the total number of moles of said composite material.

[0046] The composite material of the invention preferably comprises approximately 1 to 8% by mole of titanium, particularly preferably approximately 1 to 3% by mole of titanium, and more particularly preferably approximately 1.5 to 2.5% by mole of titanium, relative to the total number of moles of said composite material.

[0047] The composite material of the invention preferably comprises about 1 to 8 mole percent of iron, particularly preferably about 1 to 3 mole percent of iron, and more particularly preferably about 1 to 2 mole percent of iron, relative to the total number of moles of said composite material.

[0048] The TiFe particles of the composite material of the invention are preferably in the form of particles having a TiFe (zerovalent) core and a shell or coating comprising at least one iron oxide, at least one titanium oxide, and / or at least one mixed iron and titanium oxide.

[0049] The oxides can be chosen from Fe2Ti2O7, TiFe2O4, and / or Fe2Ti2O7.

[0050] The shell or coating represents a passivation layer.

[0051] The carbon material of the bio-based carbon-TiFe composite material advantageously comprises an amorphous carbon skeleton associated with randomly dispersed graphitized domains.

[0052] Graphitic domains optimize the delocalization of phonons within the material, thereby optimizing thermal conductivity, and de facto minimizing thermal gradients within the material (between the external surface and the core of the material) in the event of external heating.

[0053] The graphitic character (sp2 organized character of carbon) controls the transport of phonons, associated with heat transport, this heat playing an important role for the desorption of H2. Thus, in the event of external heating of the material of the invention, the graphitic character facilitates the propagation of phonons (heat), minimizing the thermal gradients from the outside to the inside of the material.

[0054] Furthermore, the graphitic character associated with the amorphous carbon skeleton makes it possible to obtain a good compromise between sp2 and sp3 carbons within the material of the invention. The amorphous character (sp3 carbon) makes it possible to obtain a high microporous specific surface area and to promote H2 storage.

[0055] In a particularly preferred embodiment of the invention, the carbon material of the bio-based carbon-TiFe composite material has a disorder parameter ID / (ID+IG), ID being the intensity of the D band and IG the intensity of the G band respectively, less than or equal to 51%, preferably from 45% to 50%, and particularly preferably from 48% to 49%, the intensities of the G band and the D band being measured on a Raman spectrum and the D band corresponding to a first principal band centered on 1337 cm1, and the G band corresponding to a second principal band centered on 1584 cm1.

[0056] Band D corresponds to disordered sp2 carbon, and band G corresponds to the two-dimensional movement in the plane of strongly coupled sp2 carbons (i.e., E2g symmetry) in the honeycomb structure of the graphite lattice. The width of band G and band D can provide information about graphitization.

[0057] In a preferred embodiment, the carbon material of the bio-based carbon-TiFe composite material has an electrical conductivity ranging from approximately 25 to 50 Sm1, and more preferably from approximately 28 to 32 S.m1.

[0058] The process

[0059] The invention has as a second object a method for preparing a composite material according to the first object of the invention, characterized in that it comprises at least the following steps: (i) prepare a hydrophilic alkaline phase comprising at least one monomer, oligomer or polymerizable prepolymer derived from industrial lignin, at least one surfactant, and at least one crosslinking agent, (ii) to contact and mix said hydrophilic alkaline phase with a hydrophobic oily phase comprising at least one organic solvent or at least one oil, so as to form an emulsion, iii) polymerize the emulsion to form a solid, iv) carbonize the solid to form a porous monolithic carbon material by subjecting the solid obtained in step iii) to a heating step from an initial temperature Ti to a final temperature Tf, in which the initial temperature Ti ranges from approximately 15°C to 30°C, and the final temperature Tf is greater than or equal to approximately 850°C, v) impregnate the porous monolithic carbon material obtained in step iv) with a solution comprising at least one titanium precursor and at least one iron precursor, vi) add a reducing agent and recover a reduced solid, and vii) carbonize the reduced solid at a temperature of at least approximately 850°C.

[0060] The process is simple, economical, and uses a polymerizable precursor that is a renewable material. Furthermore, it leads to an intermediate carbon material (a porous monolithic carbon material) with porosity properties suitable for receiving TiFe particles and allowing their heterogeneous dispersion within the porous network. Finally, the combination of the electronic properties of the intermediate porous carbon material and the TiFe nanoparticles results in a composite material suitable for hydrogen storage.

[0061] Step i)

[0062] The hydrophilic alkaline phase corresponds to an external dispersion phase and represents the continuous phase.

[0063] Step i) is preferably carried out at room temperature.

[0064] The monomer, oligomer or polymerizable prepolymer derived from industrial lignin.

[0065] In the present invention, the term "polymerizable monomer, oligomer or prepolymer derived from industrial lignin" refers to a polymerizable monomer, oligomer or prepolymer derived from industrial lignins.

[0066] Indeed, the monomer, oligomer or polymerizable prepolymer used in the hydrophilic alkaline phase comes from lignocellulosic biomass.

[0067] Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. Generally speaking, lignin results from the oxidative polymerization of at least three types of phenolic alcohols: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. Its structure depends on the origin botany, the age of the plant, the type of tissue, the cells and cell walls in which it is found. This strong natural variation, combined with variations due to analytical methods, makes it difficult to present the structure of lignins.

[0068] Thus, the term "lignin" is a generic name which designates a group of high molecular weight polyphenolic polymers of variable and complex composition and structure.

[0069] In chemical methods of pulp manufacturing, lignins are separated from cellulose by chemical processes that significantly alter their structure. The residual lignins, then called "industrial lignins," are present in dissolved form in the cooking liquors, which may also contain hemicellulose monomers. These cooking liquors are highly basic in the Kraft process, also known as the "Kraft process." Industrial lignins can be extracted and constitute a by-product representing a significant amount of waste, exceeding 50,000 tons per year worldwide.

[0070] Several types of industrial lignins are available and can be used in the context of the invention as raw material to provide the polymerizable monomer, oligomer or prepolymer, and preferably Kraft lignin which comes from the papermaking process of the same name and represents more than 80% of the world's paper production.

[0071] Kraft lignin is one of the main by-products of the paper industry, currently available in very large quantities and utilized to a very small extent, as "black liquor". Black liquor, also called Kraft black liquor, is the cooking liquor resulting from the manufacture of paper according to the Kraft process. It is in the form of a highly basic aqueous solution composed mainly of Kraft lignin residues and hemicellulose dissolved from the paper pulp, as well as other inorganic chemical compounds used in the dissolution method.

[0072] In one embodiment, the polymerizable monomer, oligomer, or prepolymer derived from industrial lignin is supplied in the hydrophilic alkaline phase as a solution comprising said polymerizable monomer, oligomer, or prepolymer derived from industrial lignin. In this embodiment, the solution comprising said polymerizable monomer, oligomer, or prepolymer derived from industrial lignin is preferably a cooking liquor, and more preferably a black liquor.

[0073] In fact, Kraft lignin is the main constituent of black liquor, which allows its preferential use as the main constituent of the hydrophilic alkaline phase, without prior modification.

[0074] In the case where the solution is a cooking liquor, in particular black liquor, the solution further comprises a solvent derived from this liquor.

[0075] The solvent can be chosen from polar solvents such as water, Ci-C5 alcohols, DMSO or THF, and preferably water. In other words, the solution comprising the polymerizable monomer, oligomer or prepolymer is preferably an aqueous solution.

[0076] The black liquor may contain from about 20% to about 80% by mass of dry matter, and preferably from about 40% to about 60% by mass of dry matter.

[0077] The hydrophilic alkaline phase preferably comprises 40 to 60% by weight of said solution comprising said polymerizable monomer, oligomer or prepolymer, and more preferably 50 to 60% by weight of said solution comprising said polymerizable monomer, oligomer or prepolymer, relative to the total weight of the hydrophilic alkaline phase.

[0078] The hydrophilic alkaline phase preferably has a pH between 12 and 14, and more preferably between 13 and 14.

[0079] The solution comprising said polymerizable monomer, oligomer or prepolymer derived from industrial lignin (cooking liquor such as black liquor) preferably has a density between 1.2 and 1.4 g / cm3.

[0080] In a particular embodiment, step i) is carried out such that the solution comprising the monomer, oligomer, or polymerizable prepolymer and the surfactant are mixed together until the surfactant is completely dissolved to form a resulting composition, and the crosslinking agent is added to the resulting composition, preferably dropwise, to form the hydrophilic alkaline phase. Further mixing may be carried out to promote the formation of a homogeneous hydrophilic alkaline phase.

[0081] The surfactant

[0082] In order to form a stable oil-in-water emulsion in step ii), a highly hydrophilic surfactant is added to the hydrophilic alkaline phase.

[0083] The surfactant is preferably chosen from anionic and nonionic surfactants. Cationic surfactants may precipitate.

[0084] The anionic surfactant may comprise a hydrophilic head selected from a carboxylate, sulfate and sulfonate group, and a nonpolar part selected from a linear alkyl chain, a branched alkyl chain, said alkyl chain being optionally functionalized, a linear alkylbenzene chain, and a branched alkylbenzene chain.

[0085] In a preferred embodiment, the anionic surfactant is chosen from sodium dodecyl sulfate (SDS), sodium dodecylsulfonate, sulfasuccinate of dioctyl and sodium (AOT), triethanolamine stearate, sodium lauryl sulfate and triethanolamine lauryl sulfate, and more preferably SDS.

[0086] Non-ionic surfactants may be selected from alkyl polyethoxylates, ethoxylated alkylphenols, polyethylene oxide and polypropylene oxide polymer complexes, polyethylene oxide octylphenols, polyethylene oxide nonylphenols, polyethylene oxide and polypropylene oxide block copolymers (also known as ethylene glycol and propylene glycol block copolymers), sorbitan fatty acid monoesters and polyesters, glycerol fatty acid monoesters and polyesters, and mixtures thereof.

[0087] Examples of ethylene glycol and propylene glycol block copolymers are those sold, for example, under the trade names Pluronic® P123, Pluronic® P108 and Pluronic® F127 by BASF.

[0088] The hydrophilic alkaline phase preferably comprises 1 to 10% by weight of said surfactant, and more preferably 3 to 5% by weight of said surfactant, relative to the total weight of the hydrophilic alkaline phase.

[0089] The crosslinking agent

[0090] The hydrophilic alkaline phase includes a crosslinking agent.

[0091] This crosslinking agent is preferably chosen from epichlorohydrin and cyanuric chloride.

[0092] The hydrophilic alkaline phase preferably comprises 5 to 15% by weight of said crosslinking agent, and more preferably 7 to 12% by weight of said crosslinking agent, relative to the total weight of the hydrophilic alkaline phase.

[0093] The polymerizable monomer(s), oligomer(s), or prepolymer(s) contained in the hydrophilic alkaline phase is / are crosslinked by the crosslinking agent to obtain a rigid solid. Crosslinking creates covalent bonds between the polymer chains using the reactive chemical groups present on the lignin chains (aliphatic alcohols and phenols) as well as on any hemicellulose chains present (aliphatic alcohols only), in an aqueous basic medium and at moderate temperature. Under these conditions, the preferred crosslinking agent is epichlorohydrin. The reaction of epichlorohydrin with Kraft lignin from black liquor has the advantage of being catalyzed in a highly basic medium at a moderate temperature of 60°C.

[0094] In a particularly preferred embodiment, the hydrophilic alkaline phase is a hydrophilic alkaline aqueous phase.

[0095] Step ii)

[0096] The hydrophobic oily phase corresponds to a dispersed internal phase.

[0097] The emulsion obtained in step ii) is of the "oil-in-water" type, i.e., comprising an aqueous phase and an organic phase, the aqueous phase being an aqueous phase hydrophilic or external dispersion phase and the organic phase being a hydrophobic oily phase or internal dispersed phase.

[0098] The hydrophobic oily phase comprises an organic solvent or an oil, and preferably an organic solvent.

[0099] The hydrophobic oily phase is preferably made up of an organic solvent or an oil, and more preferably of an organic solvent.

[0100] The organic solvent (respectively the oil) preferably has a density close to that of the solution comprising the monomer, oligomer or polymerizable prepolymer or of the hydrophilic alkaline phase, such as a density greater than 1.0 g / cm3, and more preferably between 1.2 and 1.4 g / cm3. This allows the formation of a stable emulsion.

[0101] In order to provide an emulsion during step ii) of contacting and mixing, the hydrophobic oily phase is immiscible with the hydrophilic alkaline phase or with at least one component of said hydrophilic alkaline phase.

[0102] The organic solvent can be chosen from linear or branched alkanes, and preferably linear or branched halogenated alkanes such as 1,2-dichloroethane.

[0103] The oil can be chosen from natural oils such as castor oil or turpentine oil.

[0104] The oil can have a melting point ranging from about 10°C to about 40°C, and preferably close to room temperature.

[0105] An organic solvent, in particular 1,2-dichloroethane, is preferred.

[0106] Step ii) of contacting and mixing is preferably such that a volume Vo of the hydrophobic oily phase is contacted and mixed with a volume V of the hydrophilic alkaline phase so as to form an emulsion having a volume Ve = Va + Vo, Vo being greater than Va.

[0107] In particular Vo / Ve > 0.51, and preferably Vo / Ve > 0.55.

[0108] In one embodiment, Vo / Ve < 0.70, and preferably Vo / Ve < 0.65.

[0109] Step ii) is preferably carried out at room temperature (i.e. 18-25°C).

[0110] Step ii) is preferably carried out for 70 to 90 min.

[0111] Step ii) is preferably carried out with a double syringe system.

[0112] The emulsion is preferably monodisperse.

[0113] Step iii)

[0114] The process of the invention in particular involves the polymerization of a highly concentrated emulsion.

[0115] Step iii) of polymerization allows the reaction of the crosslinking agent with the polymerizable monomer(s), oligomer(s) or prepolymer(s) derived from industrial lignin.

[0116] Step iii) can be carried out at a temperature below 100°C, and preferably at a temperature ranging from about 40°C to about 80°C. Step iii) of polymerization allows the formation of a solid which can then be carbonized.

[0117] Step iii) is preferably carried out over 24 to 48 hours.

[0118] Before step iii), the process may include a step ii') in which emulsion from step ii) is placed in a container such as a mold, preferably a closed container. Then, the container is heated to a temperature as defined above during polymerization step iii).

[0119] The process may further include a washing step iii-1), for example by washing the solid obtained in step iii) with a solvent such as a Ci-C5 alcohol, or diethyl ether, in particular by means of a soxhlet apparatus.

[0120] The washing step iii-1) can be followed by a drying step iii-2) at a temperature below 100°C, and preferably at a temperature ranging from about 50°C to about 90°C, preferably under vacuum.

[0121] Step iv)

[0122] By means of step iv), an intermediate porous carbon material is obtained which has a size, shape and chemical composition of pores which simultaneously offer a high surface area and good electron transport properties.

[0123] According to a preferred embodiment of step iv), said heating step is characterized by: * a heating speed greater than 1°C / min, * a first plate at a TPI temperature ranging from 250 to 350°C, * a second plate at a TP2 temperature ranging from 550 to 750°C, and * a third tray at the final temperature Tf, each tray being completed for less than 120 minutes.

[0124] Such a heat treatment makes it possible to obtain enough graphitized domains to have good H2 adsorption / desorption performance.

[0125] In a preferred embodiment, the final temperature Tf ranges from approximately 850°C to 1700°C, more preferably from approximately 860°C to 1400°C, particularly preferred from approximately 875°C to 1200°C, and most particularly preferred from approximately 875°C to 1000°C.

[0126] The heating step iv) may have a heating rate greater than 2°C / min, preferably from 3°C / min to about 10°C / min, and particularly preferably from about 4°C / min to 7°C / min.

[0127] The first platform preferably has a TPI temperature ranging from approximately 275 to 325°C.

[0128] The second plate preferably has a temperature TP2 ranging from approximately 575 to 700°C, and particularly preferably ranging from approximately 575 to 675°C.

[0129] Each tray is preferably made for a duration less than or equal to about 100 min, more preferably for about 30 min to 90 min, and even more preferably for about 45 min to 75 min.

[0130] Step iv) is generally carried out under an inert atmosphere such as argon, or nitrogen (when the temperature is less than or equal to 1200°C and preferably less than or equal to 1000°C).

[0131] Step iv) is preferably carried out with an inert atmosphere flow rate of approximately 0.05 l / min to 0.5 l / min.

[0132] Step iv) can be followed by an uncontrolled cooling step to ambient temperature of the carbonized solid.

[0133] Step iv')

[0134] The process may further include after step iv), a step iv') of washing the carbonized solid.

[0135] The washing step iv') can allow the removal of residual salts; this step is optional in that the following step v) indirectly allows the washing of the carbonized solid material obtained in step iv).

[0136] The washing step iv') can be carried out with at least one solvent such as water.

[0137] The monolithic porous carbonaceous material obtained at the end of step iv) or iv') is a monolith.

[0138] The monolithic porous carbon material is a porous material. The porosity arises from the imprint of the internal dispersed phase or from the removal of water possibly contained in the external dispersed phase.

[0139] Preferably, the monolithic porous carbon material obtained at the end of step iv) or iv') is an essentially microporous material comprising micropores, mesopores and possibly macropores.

[0140] The monolithic porous carbon material obtained at the end of step iv) or iv') comprises a hierarchical mesoporous / microporous structure. In other words, the monolithic porous carbon material obtained at the end of step iv) or iv') has a cellular structure exhibiting at least double porosity.

[0141] In a particularly preferred embodiment, the micropores of the monolithic porous carbon material obtained at the end of step iv) or iv') have a size ranging from 0.1 to less than about 2 nm.

[0142] In a particularly preferred embodiment, the mesopores of the monolithic porous carbonaceous material obtained at the end of step iv) or iv') have a size ranging from approximately 2.0 to 10.0 nm, and more preferably from approximately 2.0 to 5.0 nm.

[0143] In a preferred embodiment, the monolithic porous carbonaceous material obtained at the end of step iv) or iv') comprises interconnected micropores and mesopores. In other words, the micropores are interconnected to each other. In other cases, the mesopores are interconnected with each other and the micropores are interconnected with the mesopores.

[0144] The monolithic porous carbon material obtained at the end of step iv) or iv') may further comprise macropores.

[0145] In a particularly preferred embodiment, the macropores of the monolithic porous carbon material obtained at the end of step iv) or iv') have a size ranging from approximately 0.2 pm to 200 pm.

[0146] In a preferred embodiment, the monolithic porous carbon material obtained at the end of step iv) or iv') has a specific surface area of ​​between 1200 and 1900 m2 / g approximately, and more preferably between 1350 and 1750 m2 / g approximately.

[0147] In a preferred embodiment, the monolithic porous carbon material obtained at the end of step iv) or iv') has an apparent skeleton density ranging from approximately 0.5 to 0.8 g.ml1.

[0148] In a preferred embodiment, the monolithic porous carbon material obtained at the end of step iv) or iv') has a porosity ranging from approximately 60% to 80%.

[0149] The monolithic porous carbonaceous material obtained at the end of step iv) or iv') advantageously comprises an amorphous carbon skeleton associated with randomly dispersed graphitized domains. The graphitized domains confer electron transport properties to this material.

[0150] In the material obtained at the end of step iv) or iv'), a compromise is found between a high specific surface area and good electronic transport properties (i.e. high graphitization).

[0151] In a particularly preferred embodiment of the invention, the monolithic porous carbon material obtained at the end of step iv) or iv') has a disorder parameter ID / (ID+IG), ID being the intensity of the D band and IG the intensity of the G band respectively, less than or equal to about 50.0%, preferably from about 48.0% to 49.5%, and particularly preferably from about 48.5% to 49.0%, the intensities of the G band and the D band being measured on a Raman spectrum and the D band corresponding to a first principal band centered on 1337 cm4, and the G band corresponding to a second principal band centered on 1584 cm4.

[0152] The D band corresponds to disordered sp2 carbon, and the G band corresponds to the two-dimensional in-plane movement of strongly coupled sp2 carbons (i.e., E2g symmetry) in the honeycomb structure of the graphite lattice. The width of the G and D bands can provide information about graphitization.

[0153] In a preferred embodiment, the monolithic porous carbon material obtained at the end of step iv) or iv') has an electrical conductivity ranging from approximately 20 to 40 S.m1, and more preferably from approximately 25 to 35 Sm'.

[0154] The following steps v), vi) and vii) allow TiFe particles to be deposited by heterogeneous nucleation using an impregnation and reduction method involving the use of a titanium and iron precursor solution, followed by a key heat treatment.

[0155] Step v)

[0156] Step v) consists of impregnating the porous monolithic carbon obtained in step iv) or iv') with a solution comprising at least one titanium precursor and at least one iron precursor.

[0157] The titanium precursor may be a titanium alkoxide such as titanium ethoxide (IV), a titanium oxychloride, or a titanium chloride.

[0158] Alkoxides, and more particularly titanium(IV) ethoxide, are preferred.

[0159] The iron precursor may be an iron chloride or an iron nitrate.

[0160] The iron from the iron precursor can be in the form of iron (II) or (III).

[0161] Iron nitrate is preferred.

[0162] The solution preferably further comprises a solvent, preferably a protic polar solvent.

[0163] The solvent may be chosen from ethanol, isopropanol, or any other Cr C5 alcohol.

[0164] The iron and titanium precursors are advantageously chosen so as to be soluble in the same solvent in order to form said solution.

[0165] During step v), the iron precursor preferably represents about 1% to 10% by mass, and particularly preferably about 2% to 6% by mass, relative to the total mass of the solution.

[0166] During step v), the titanium precursor preferably represents about 1% to 10% by mass, and particularly preferably about 2% to 6% by mass, relative to the total mass of the solution.

[0167] During step v), the Ti / Fe atomic ratio in said implemented solution preferably goes from about 0.5 to 2.

[0168] The precursor solution is added to the porous monolithic carbon in step v) so as to impregnate the monolithic carbon with the iron and titanium ions required for the generation of TiFe.

[0169] Step v) is preferably carried out under vacuum.

[0170] Step v) of impregnation can last from 1 to 12 hours.

[0171] Step vi)

[0172] Step vi) consists of adding a reducing agent and then recovering a reduced solid.

[0173] The reducing agent is preferably a solid borohydride of formula MBH4 or MBH3CN, in which M represents an atom of sodium, lithium, potassium, magnesium, or calcium.

[0174] Sodium borohydride is preferred.

[0175] The reducing agent may be pre-dissolved in a solvent such as water. In this embodiment, step vi) consists of adding a solution comprising the reducing agent.

[0176] The reducing agent may represent from 0.5% to 10% by mass approximately, and particularly preferably from 1% to 5% by mass approximately, relative to the total mass of the solution.

[0177] The molar quantity of reducing agent is preferably chosen in excess of the molar quantity of iron and titanium precursors impregnating the monolith.

[0178] Step vi) is preferably carried out under vacuum.

[0179] Step vi) of reduction can last from 1 to 12 hours.

[0180] At the end of the reduction, a reduced solid is recovered.

[0181] The process may further include after step vi) a step vi') of drying the reduced solid, preferably at a temperature of at least 50°C, and preferably from 90 to 120°C.

[0182] Step vi') can be carried out in an oven.

[0183] Step vi') is preferably carried out under vacuum.

[0184] Step vii)

[0185] Step vii) includes after step vi) or vi') the carbonization of the reduced solid at a temperature of at least 850°C, preferably at a temperature ranging from about 890°C to 1000°C.

[0186] This step vii) enables the formation of TiFe particles. This step enables the carboreduction necessary to obtain a cooperative carbon-TiFe effect during hydrogen storage.

[0187] Step vii) is preferably carried out under vacuum.

[0188] Step vii) can last from 12 to 100h.

[0189] The invention has as its third object the use of a composite material conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention for the storage of hydrogen.

[0190] The cooperative effect of a bio-based carbon porous material and TiFe leads to a composite material with good performance for hydrogen storage.

[0191] The invention has as its fourth object a method for storing hydrogen in a bio-based carbon-TiFe composite material conforming to the first object of the invention or obtained according to a process conforming to the second object of the invention, said process being characterized in that it comprises at least the following steps: a) a vacuum degassing step of said bio-based carbon-TiFe composite material, preferably at a temperature ranging from approximately 10 to 250°C; b) a contacting step, preferably at a temperature ranging from approximately 10 to 250°C and / or preferably at a pressure ranging from approximately 1 to 50 bars, of said bio-based carbon-TiFe composite material degassed by the addition of dihydrogen; c) a vacuum drying step of the dihydrogen-impregnated material, preferably at a temperature of approximately 10 to 250°C; and optionally d) the repetition, once or several times, of steps b) and c) above.

[0192] At the end of step c) or d), a composite material is obtained characterized in that the micropores contain hydrogen in gaseous form.

[0193] Step a) (respectively step c)) under vacuum is preferably carried out under secondary vacuum (e.g. 0.1 bar).

[0194] The hydrogen content present in gaseous form in the composite material according to the invention will vary depending on the microporous volume and specific surface area of ​​the bio-based carbon-TiFe composite material used during step b) of impregnation and the hydrogen concentration during the impregnation of said bio-based carbon-TiFe composite material.

[0195] Generally, the hydrogen content varies from approximately 0.1 to 0.7 moles of dihydrogen per gram of bio-based carbon-TiFe composite material. This molar quantity corresponds to a mass capacity of approximately 0.1 to 0.7% (mass of dihydrogen stored relative to the total mass of the composite material).

[0196] This process, unlike prior art processes, does not include a pre-activation step.

[0197] It is a reliable process, which avoids problems of non-repeatability, and which can be implemented at low temperature.

[0198] The invention is illustrated in more detail in the following examples, but is not limited to them. Brief description of the figures

[0199] The invention is illustrated by the figures and examples that follow.

[0200] Figure [1] represents a SEM image of a composite material according to the invention.

[0201] Figure [Fig.2] represents a SEM image of a composite material according to the invention.

[0202] Figure [Fig.3] represents adsorption-desorption isotherms of a composite material according to the invention.

[0203] Figure 4 represents the amount of dihydrogen absorbed by a composite material according to the invention.

[0204] Figure [Fig. 5] represents an X-ray diffractogram of a composite material according to the invention before and after absorption of H2.

[0205] EXAMPLES

[0206] The raw materials used in the following examples are listed below: * Kraft black liquor (KBL), average residual dry mass of about 45% by mass, supplied by Smurfit Kappa Pine Cellulose; * (±)-Epichlorohydrin, purity > 99%, Sigma-Aldrich / Merck; * Pluronic® F-108, Sigma-Aldrich / Merck; * 1,2-dichloroethane (DCE), purity > 99.0%, Sigma-Aldrich / Merck; * Sodium borohydride NaBH4, purity > 98.0%, Sigma-Aldrich / Merck; * Titanium ethoxide (IV), Sigma-Aldrich / Merck; * Isopropanol, purity >98%, VWR; * Absolute ethanol, purity >99.8%, NORMAPUR®, VWR; * Diethyl ether, purity > 99.7%, VWR; * Iron (III) nitrate monohydrate, purity > 99%, Acros organics.

[0207] All reagents were used without further purification.

[0208] Kraft black liquor as received is in the form of a viscous black liquid. Its main physicochemical properties are as follows: dynamic viscosity p = 7000 mPa.s at 23°C; pH = 14; density p = 1.3 g.ml1; dry matter content ~ 50% by weight. The phenol group content and the total hydroxyl group content of the black liquor are 0.5 mmol.g1 and 0.8 mmol.g2, respectively.

[0209] Measuring instruments

[0210] Scanning electron microscopy (SEM) was performed using a Tescan “Tescan Vega3 SB” microscope, equipped with a secondary electron (SE) detector, a backscattered electron (BSE) detector, and an energy-dispersive X-ray spectrometer (EDS, “Ametek EDAX-TSL” instrument) for analyzing the elemental composition of the surface. The material samples were mounted on a carbon strip to ensure good conductivity.

[0211] The macroporosity of the samples was studied by mercury intrusion porosimetry (MIP) using a Micromeritics Autopore IV 9500 porosimeter with the following parameters: contact angle = 130°, surface tension of Hg = 485 mN.m1 and maximum intrusion pressure set at 124 MPa. The determination of the The porosity characteristics of the pore size distribution were based on the Washburn equation relating the applied pressure to the size of the pores into which the mercury penetrated.

[0212] The specific surface area was determined by recording the nitrogen sorption isotherms at 77 K with a Micromeritics “3Flex” gas sorption analyzer after degassing the sample at 250°C under vacuum. The specific surface areas were calculated using the Brunauer, Emmett, and Teller (BET) method from a limited range of pressures in the adsorption curves.

[0213] X-ray diffraction was performed and recorded on a Philips PANalytical X'Pert Pro equipped with a copper source (XKal = 0.15405 nm and XKa2 = 0.15443 nm). The powder was recorded over the angular range 10-80° (20), with a step size of 0.02° (20) and an active width of 2.022° (20) in the detector.

[0214] X-ray photoelectron spectroscopy (XPS) was performed using a Thermo Fisher Scientific K-Alpha photoelectron spectrometer equipped with a monochromatic AlKa source (hv = 1486.6 eV). Full-spectrum (0-1350 eV) and high-resolution spectra were recorded with constant pass-through energies of 200 eV and 40 eV, respectively. Ar+ sputtering was used for depth profiles, and the high-resolution spectra were processed using AVANTAGE software. The etching rate was set at 0.3 nm·s (calibrated on the SiO2 layer). All scans were corrected using C(ls) as the reference (285.0 eV).

[0215] Raman spectra can be recorded in backscatter geometry using a Labram HR microspectrometer (Horiba Group, France) equipped with a confocal microscope. In particular, the experiments can be performed by exciting the samples at a wavelength of 514.5 nm (2.41 eV) with an Ar-ion laser. The spectral resolution can be 6 cm⁻¹ with a confocal hole aperture of 150 pm and a diffraction grating of 600 grooves / mm. The laser can be focused onto the sample using a 50x objective (numerical aperture of 0.75). The beam power at the sample can be approximately 200 pW to avoid overheating effects due to laser irradiation. The spectra can be recorded with an acquisition time of 60 s and 4 accumulations. Manual baseline corrections of spectra can be performed using LabSpec 5 software prior to deconvolutions.Deconvolutions can be performed using a simple 2-point fit for 500-2000 cm1 (D & G) and a 4-point fit for 2500-3250 cm4, corresponding to bands SI-, S2-, S3- & S4.

[0216] Example 1: preparation of the composite material according to the invention

[0217] Step i)

[0218] 20 g of KBL and 0.9 g of Pluronic® F-108 (non-ionic surfactant) have were gently mixed (100 revolutions per minute) at room temperature until the non-ionic surfactant Pluronic® F-108 was completely dissolved. Then, 2.2 g of epichlorohydrin were added dropwise and mixed for 10 minutes to prepare a hydrophilic alkaline phase.

[0219] Step ii)

[0220] Direct emulsification was achieved using a laboratory homogenization system consisting of two polyethylene syringes (60 ml, internal diameter 29.2 mm) connected by a small-diameter nylon tube (ID = 11 mm; OD = 4 mm; length = 15 mm). The prepared hydrophilic alkaline phase (20 g, or approximately 16 ml) was introduced into one of the syringes, while a hydrophobic oily phase composed of 1,2-dichloroethane (15 ml) was added to the second syringe. Direct emulsification was achieved by successive back-and-forth passes through the connecting tubing. The flow rate for generating the emulsion was set at 10 back-and-forth movements per minute, and the emulsification time was set at 80 minutes. After the emulsification process, the emulsion was removed from the syringes and poured into a cylindrical PTFE mold (diameter of 45 mm, height of 15 mm) pinched between two Teflon plates.

[0221] Steps ii') and iii)

[0222] The mold was placed in an oven (“Thermo Scientific Heraeus Vacutherm VT6060”) and heated to 80°C for 24 hours to allow epichlorohydrin to react with lignin and hemicellulose.

[0223] Crosslinking occurs through the chemical reaction between the alcohol groups present in lignin and / or hemicellulose and the chlorine and oxirane functions of epichlorohydrin, thus creating glycerol bridges between the oligomers.

[0224] Steps iii-1) and iii-2)

[0225] After crosslinking, the monolith was washed in a Soxhlet apparatus for two days with isopropanol and one day with diethyl ether before being dried for 2 days at 85°C under vacuum.

[0226] Step iv)

[0227] Approximately 200 mg of the solid obtained in step iii-2) was carbonized in an alumina tube furnace to obtain an intermediate porous monolithic carbonaceous material. In particular, the solid obtained in step iii-2) was degassed under an Argon flow (0.3 l.min-1) for 30 minutes, then (still under the Ar flow) the temperature was increased to 900°C at a heating rate of 5°C / min with plateaus at 300°C, 600°C, and 900°C for 1 h each. Cooling is uncontrolled and governed by the inertia of the furnace. The resulting carbonized solid was labeled Carbo(HIPE). This solid exhibits a porosity of ~70% and an apparent skeleton density of 0.67 g / ml

[0228] Step v)

[0229] After carbonization, 150 mg of the Carbo(HIPE) material were placed under dynamic vacuum in a Schlenk tube for 30 minutes. During this time, two solutions were prepared simultaneously. The first consisted of 1.18 g of iron nitrate dissolved in 25 mL of absolute ethanol. The second consisted of 1.11 g of titanium(IV) ethoxide dissolved in 24 mL of absolute ethanol. 3 mL of each solution were collected and mixed. After 30 minutes of vacuum, the TiFe precursor solution was injected into the Schlenk tube while maintaining a static vacuum. The Carbo(HIPE) material was thus impregnated for 6 hours.

[0230] Step vi)

[0231] The impregnated Carbo(HIPE) material was collected and placed again under dynamic vacuum for 30 min. Meanwhile, an aqueous sodium borohydride solution was prepared using 75 mg of NaBH4 dissolved in 5 mL of deionized water. This sodium borohydride solution was injected into the Schlenk tube under static vacuum and left to react overnight. When the reduction began, dihydrogen was produced, so the Schlenk tube was opened to reduce the pressure. Once the reaction was complete, the impregnated and reduced Carbo(HIPE) material was collected and dried in an oven at 110°C under vacuum for 24 hours.

[0232] Step vii)

[0233] Finally, the material was placed in a vacuum-sealed quartz bulb and heated to 900°C for 72 hours, generating a composite material according to the invention called TiFe@CarboHIPE.

[0234] Fig. 1 shows the composite material according to the invention by SEM.

[0235] In this [Fig. 1], the TiFe particles appear to cover the entire surface of the carbonaceous material ([Fig. 1] A), indicating persistent coverage of the metallic species. A random distribution of both particle swath and particle size is observed. Two types of particle morphologies (populations) are observed: needle-shaped particles and isotropic faceted particles (Figures 1 B and C). The needle-shaped particles exhibit a high aspect ratio with lengths of several micrometers for a cross-section of 0.7–0.5 micrometers. The isotropic faceted particles, while having a low aspect ratio, are more polydisperse in terms of size, ranging from hundreds of nanometers to sizes on the order of micrometers.

[0236] Figure 2 shows an SEM image of the composite material according to the invention acquired in electron backscatter mode (Fig. 2A) coupled with an energy-dispersive X-ray spectroscopy analysis (Fig. 2B) focusing on the Atomic distribution between iron and titanium of the TiFe particles obtained on the carbon of the composite material according to the invention. EDX measurements on these particles demonstrate the presence of the expected TiFe stoichiometry, thus confirming the presence of the desired intermetallic compound.

[0237] [Fig.3] shows adsorption-desorption isotherms (physisorption of N2) concerning the composite material according to the invention TiFe@Carbo(HIPE) ([Fig.3] A, adsorption-desorption curves in dashed lines) and a non-inventory material Carbo(HIPE)-TT obtained by heat treatment of the Carbo(HIPE) material of step iv), said heat treatment being identical to that of TiFe@Carbo(HIPE) according to step vii) ([Fig.3] A, adsorption-desorption curves filled) [i.e. material obtained according to the process of the invention without steps v) and vi), or in other words carbon material from the same process without TiFe particles]; and the pore size distribution, calculated by DFT (Density Functional Theory) for the composite material according to the invention TiFe@Carbo(HIPE) ([Fig.3] B, dotted curve) and the material not according to the invention Carbo(HIPE)-TT ([Fig.3] B, solid curve).

[0238] The isotherms obtained give profiles typical of activated carbons exhibiting both micro- and mesoporosity ([Fig. 3] A). Nitrogen absorption at low relative pressure is higher for the material according to the invention, TiFe@Carbo(HIPE), than for the non-material according to the invention, Carbo(HIPE)-TT, indicating that the composite material according to the invention has intrinsically higher microporosity than the carbon support free of TiFe intermetallic particles. Furthermore, the hysteresis loops between the adsorption and desorption curves occurring at a medium relative pressure (induced by capillary condensation of N2) are more pronounced, but still small, for the material according to the invention, TiFe@Carbo(HIPE), indicating a higher degree of mesoporosity. For both materials, N2 absorption at high relative pressure is present, indicating macroporosity.As a direct consequence, the BET specific surface area of ​​the non-inventory material Carbo(HIPE)-TT can be estimated at 1030 m2.g*, and that of the invention-compliant material TiFe@Carbo(HIPE) at 1230 m2.g*, for a similar mesoporous surface area of ​​120 m2.g', which allows us to consider that the increase in specific surface area comes from an increase in microporosity, in agreement with the N2 sorption curves at low relative pressures P / P° and with the higher sp3 XPS contribution (data not reported).

[0239] The apparent density of the material according to the invention TiFe@Carbo(HIPE) is 0.1910 g.cm³ and that of the material not according to the invention Carbo(HIPE)-TT is 0.1717 g.cm³. The volumetric specific surface area of ​​the material according to the invention TiFe@Carbo(HIPE) is 22.9 m².cm³ and that of the material not according to the invention Carbo(HIPE)-TT is less than 20.6 m².cm³. This increase in volumetric surface area, arising essentially from microporosity, is mainly induced by an intrinsic carbon activation process (oxidation of the carbon skeleton) which is additional and clearly more significant than the external specific surface area of ​​the TiFe particles.

[0240] DFT calculations extrapolated from nitrogen sorption curves indicate the presence of micropores and small mesopores smaller than 2 nm and shoulders larger than 100 nm, foreshadowing macroporosity ([Fig. 3] B). The presence of TiFe particles does not radically alter the distribution of micro- and mesoporous pore sizes, but the overall population envelope is higher for the material according to the invention, TiFe@Carbo(HIPE). These enhanced microporous characteristics, which address pores smaller than 5.0 nm, are of particular interest for hydrogen storage applications. With the addition of dihydrogen-absorbing TiFe particles, the material according to the invention, TiFe@Carbo(HIPE), is of crucial interest for hydrogen sorption, where the microporous framework of the carbonaceous material and the TiFe particles can act cooperatively.

[0241] Example 2: Use of the composite material according to the invention for hydrogen storage

[0242] The material as prepared in Example 1 TiFe@Carbo(HIPE) was tested for hydrogen sorption according to a known method called "de Sievert" [Panella et al., Carbon, 2005, 43, 2209; and Serrano et al., J. Alloys Compd., 2023, 945, 169289].

[0243] 100 mg of TiFe@Carbo(HIPE) composite material are placed in the carrier- The sample was degassed using vacuum / argon cycles of 5, 10, and 20 minutes. Then, the desired hydrogen pressure (40 bar) was pre-charged and expanded in the sample holder at room temperature. After gas expansion, a 1000-second rest period was imposed to ensure thermodynamic equilibrium. After each adsorption, the sample was degassed for 10 minutes at room temperature. The same experiment was performed at 150°C. This yielded a dihydrogen-charged composite material, TiFe@Carbo(HIPE)*H₂.

[0244] Fig. 4 shows the amount of dihydrogen absorbed by the composite material according to the invention TiFe@Carbo(HIPE) as a function of time at two different temperatures: 25°C (solid curve) and 150°C (curve with dotted lines).

[0245] TiFe is known to absorb dihydrogen under thermodynamically challenging conditions for first absorption, typically at over 400°C and 50 bars.

[0246] The composite material according to the invention, TiFe@Carbo(HIPE), exhibits a sorption of 0.5 wt% at 25°C with a plateau reached after 300 s, and a sorption of 0.2 wt% at 150°C with a plateau reached after 100 s. It is important to emphasize that no pre-activation step was applied in this example. The difference in the mass of dihydrogen retained can be explained by carbon adsorption. The adsorption carried out at 150°C eliminates the adsorption of dihydrogen by carbon and characterizes only the inherent absorption of the TiFe particles. This therefore means that the TiFe particles absorb up to 0.2–0.3 wt% of dihydrogen without any activation and under normal conditions.

[0247] Fig. 5 shows an X-ray diffractogram of the composite material according to the invention TiFe@Carbo(HIPE) (Fig. 5 A) and of the composite material according to the invention after absorption of H2 TiFe@Carbo(HIPE)*H2 (Fig. 5 B).

[0248] Fig. 5 A reveals the presence of the intermetallic TiFe (diamonds) with certain oxides such as Fe2Ti2O7 (stars), TiFe2O4 (triangles) and Fe2O3 (circles).

[0249] Figure 5 B reveals, after hydrogenation, new peaks corresponding to the TiFeH2 hydride (cross) even though no activation process has been implemented. Furthermore, the adsorption of hydrogen on the carbon surface can create a proximity (equivalent to a path) that promotes the diffusion of adsorbed dihydrogen towards the immobilized TiFe particles.

[0250] By means of the process of the invention, heterogeneous nucleation and growth of intermetallic TiFe particles are achieved within a self-supporting porous carbon monolith. This carbon is generated from a waste product of the paper industry (black liquor) and shaped by a direct emulsification process. The reduction step vi) alone leads to continuous sheets of mixed iron and titanium oxides. The heat treatment of step vii) then enables the formation of new anisotropic core-shell particles composed of a titanium-iron oxide shell and a metallic TiFe core. In synergy with this "in-the-core" reduction, the surrounding carbonaceous material is oxidized or activated, thereby increasing its specific surface area through enhanced microporosity. Finally, the composite material of the invention can store dihydrogen without any pre-activation process and at relatively low temperatures.Thanks to the combination of TiFe particles and the carbonaceous host matrix which act cooperatively, hydrogen is efficiently absorbed to achieve a capacity of 0.5% by weight at 25 °C.

Claims

Demands

1. Bio-based carbon-TiFe composite material, characterized in that it is a porous monolithic material and in that it comprises a carbon material and TiFe particles dispersed in said carbon material.

2. Material according to claim 1, characterized in that it is an essentially microporous material comprising micropores, mesopores and optionally macropores.

3. Material according to claim 1 or 2, characterized in that it has a specific surface area ranging from 500 to 1500 m2 / g.

4. Material according to any one of the preceding claims, characterized in that it comprises two types of TiFe particle populations, a first population of TiFe particles in the form of elongated particles, and a second population of TiFe particles in the form of isotropic particles.

5. Material according to any one of the preceding claims, characterized in that the TiFe particles have at least one dimension of at most 20 pm.

6. Material according to any one of the preceding claims, characterized in that the TiFe particles of the composite material are in the form of particles having a TiFe core and a coating comprising at least one iron oxide, at least one titanium oxide, and / or at least one mixed iron and titanium oxide.

7. Material according to any one of the preceding claims, characterized in that it comprises 1 to 8 mole percent of titanium, and 1 to 8 mole percent of iron, relative to the total number of moles of said composite material.

8. A method for preparing a material as defined in any one of the preceding claims, characterized in that it comprises at least the following steps: i) preparing a hydrophilic alkaline phase comprising at least one polymerizable monomer, oligomer, or prepolymer derived from industrial lignin, at least one surfactant, and at least one crosslinking agent; ii) contacting and mixing said hydrophilic alkaline phase with a hydrophobic oily phase comprising at least one an organic solvent or at least an oil, so as to form an emulsion, iii) polymerize the emulsion so as to form a solid, iv) carbonize the solid to form a porous monolithic carbon material by subjecting the solid obtained in step iii) to a heating step from an initial temperature Ti to a final temperature Tf, in which the initial temperature Ti is from 15°C to 30°C, and the final temperature Tf is greater than or equal to 850°C, v) impregnate the porous monolithic carbon material obtained in step iv) with a solution comprising at least one titanium precursor and at least one iron precursor, vi) add a reducing agent and recover a reduced solid, and vii) carbonize the reduced solid at a temperature of at least 850°C.

9. A process according to claim 8, characterized in that the reducing agent is a solid borohydride of formula MBH4 or MBH3 CN in which M represents an atom of sodium, lithium, potassium, magnesium or calcium.

10. Use of a composite material as defined in any one of claims 1 to 7 or obtained according to a process as defined in claim 8 or 9, for the storage of hydrogen.

11. A method for storing hydrogen in a composite material as defined in any one of claims 1 to 7 or obtained according to a method as defined in claim 8 or 9, said method being characterized in that it comprises at least the following steps: a) a vacuum degassing step of said composite material; b) a step of bringing said degassed composite material into contact by adding dihydrogen; c) a vacuum drying step of the material impregnated with dihydrogen; and optionally d) the repetition, once or several times, of steps b) and c) above.

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