Hydrogen storage material and fuel cell containing hydrogen storage material

Abstract

The present disclosure relates to a fuel cell comprising a fuel storage material made of a mesoporous N-doped carbon material. The fuel storage material comprises a proton conducting polymeric material and a composite material comprising an agglomerated (N-doped) carbon nanofoam particle scaffold and a coating on the scaffold, the coating comprising N-doped graphitic carbon. The fuel storage material allows for storage of a fuel reserve inside the fuel cell, and is generally incorporated adjacent an electrode to provide fuel to the electrode when the fuel cell is operating in a redox mode.

Description

Technical Field

[0001] The present disclosure relates to a hydrogen storage material for a fuel cell unit, and in particular to a fuel cell unit comprising the hydrogen storage material. Specifically, the present disclosure relates to a fuel cell unit configured to operate in both a redox mode and a regeneration mode. The present disclosure also relates to a fuel cell unit having a fuel storage material, the fuel storage material being integral to the fuel cell unit and thus comprising a fuel cell unit / fuel cell unit-based energy storage device. The present disclosure also relates to a method of forming the fuel storage material. Background Art

[0002] Conventional electrochemical fuel cell units convert fuel and oxidant into electrical energy and reaction products. The typical layout of a conventional fuel cell unit includes a solid polymer ion transfer membrane sandwiched between an anode and a cathode. The polymer membrane allows protons to pass through the membrane, but blocks the passage of electrons. Typically, both the anode and cathode are formed from a conductive porous material (such as porous carbon), and small particles of platinum and / or other precious metal catalysts are bonded to the conductive porous material.

[0003] The anode and cathode are typically formed at respective adjacent surfaces of the membrane. This combination is often referred to as a membrane electrode assembly or MEA.

[0004] Typically, a polymer membrane and a porous electrode layer are sandwiched between flow plates. In conventional fuel cell cells, the flow plates provide the functions of delivering reactants to the anode and cathode and removing reaction products. Fuel cell cells may include porous gas diffusion layers, which are manufactured to ensure efficient diffusion of gases to and from the anode and cathode surfaces and facilitate the management of water vapor and liquid water.

[0005] Because the voltage produced by a single fuel cell cell is very low, multiple cells are conventionally connected in series with a conductive flow plate on the cathode side of one cell placed in electrical contact with an adjacent flow plate on the anode side of the immediately adjacent cell.

[0006] The present invention is directed to providing improvements in the design of fuel cell units and fuel cell stacks formed from such fuel cell units. Summary of the Invention

[0007] The present disclosure relates to a composite material comprising a superstructure of agglomerated (N-doped) carbon nanofoam particles coated with an N-doped graphitic carbon material, particularly useful as a fuel storage material.

[0008] A composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0009] agglomerated carbon nanofoam particle scaffolds; and

[0010] a coating on the stent, the coating comprising N-doped graphitic carbon;

[0011] The carbon nanofoam particles may be optionally N-doped.

[0012] According to a second aspect of the present disclosure, there is provided a fuel storage material comprising the composite material according to the first aspect of the present disclosure and a proton-conducting polymer material.

[0013] According to a third aspect of the present disclosure, a fuel cell unit is provided, comprising a fuel storage material according to the second aspect of the present disclosure, the fuel storage material being part of or adjacent to an electrode to at least partially provide the fuel to the electrode when operating in a redox mode.

[0014] While the present disclosure is susceptible to various modifications and alternative forms, details of the disclosure have been shown by way of example in the drawings and will be described in detail. However, it should be understood that other embodiments besides the specific ones described are possible. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are also covered.

[0015] The above discussion is not intended to represent every example embodiment or every implementation within the scope of the current or future claim groups. The following figures and detailed description also illustrate various example embodiments. The various example embodiments can be more fully understood by considering the following detailed description in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0017] Figure 1 An example embodiment of a fuel cell unit is shown and a fuel cell unit stack formed from such fuel cell units is schematically shown; and

[0018] Figure 2a and Figure 2b An SEM micrograph of the N-doped carbon nanofoam material formed in Example 1 is shown.

[0019] Figure 3a and 3b TEM micrographs of the composite materials are shown. DETAILED DESCRIPTION

[0020] The present disclosure provides a composite material and a fuel cell unit containing the composite material in various arrangements. The composite material comprises a composite particle superstructure, wherein the superstructure comprises a condensed (N-doped) carbon nano foam particle support and a coating on the support, and the coating comprises N-doped graphite carbon. The carbon nano foam particle support itself is optionally N-doped (also referred to as (N-doped) carbon nano foam). The present disclosure also provides various examples of composite materials in different arrangements, and the composite material has various uses, in particular, can be used as a fuel storage material in a fuel cell unit, especially a fuel cell unit that can be operated in a conventional redox mode and a regeneration mode. The particularly preferred type of (N-doped) carbon nano foam material used in the examples of the present disclosure will be described in more detail below.

[0021] Example embodiments of a fuel cell unit will be described.

[0022] In one or more embodiments, the fuel cell unit can be configured to operate in both a conventional redox mode and a regeneration mode, wherein the fuel and oxidant are consumed to produce an electric current and one or more reaction products, and in the regeneration mode, a potential difference is applied to the fuel cell unit, and at least one of the one or more reaction products is electrolyzed to form the fuel. Thus, one or more example embodiments of the fuel cell unit include a reversible fuel cell unit. In one or more instances, one or more catalyst layers are provided to enable operation in the redox mode and the regeneration mode.

[0023] In one or more embodiments, a fuel cell unit may include a fuel storage material as a structure or layer with an electrode of the fuel cell unit, i.e., the fuel storage material is arranged alongside or forms part of the electrode, thereby providing the ability to store fuel within the fuel cell unit. In one or more examples, the fuel storage material is provided between a first plate and a second plate, the first plate and the second plate containing the active area of ​​the fuel cell unit.

[0024] In one or more embodiments, the fuel is protons, and the fuel storage material is configured to store the fuel.

[0025] In one or more embodiments, the fuel storage material is electrically connected to the electrode.

[0026] In one or more embodiments, the fuel storage material comprises a composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0027] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0028] a coating on the stent, the coating comprising N-doped graphitic carbon;

[0029] and proton-conducting polymer materials, as will be described below.

[0030] It should also be understood that a fuel cell unit can be configured to include the fuel storage material without being configured to operate in both the redox mode and the regeneration mode. For example, a fuel cell unit can be configured to operate only in the regeneration mode and thereby function to store fuel in the fuel storage material for extraction.

[0031] It will be appreciated that references to a "fuel cell unit" may also be understood to refer to a stack of fuel cell units, given that the form of the fuel cell unit is typically replicated throughout the stack.

[0032] Figure 1 An example fuel cell unit 100 is shown according to an aspect of the present disclosure. The fuel cell unit 100 includes a polymer electrolyte membrane 101 or “PEM.” The PEM 101 includes a semi-permeable membrane and can be configured to conduct protons while acting as an electrical insulator and a reactant barrier.

[0033] The first plate 104 is disposed adjacent to, such as directly adjacent to, the first electrode 102. The second plate 105 is disposed adjacent to, such as directly adjacent to, the second electrode 103. In one or more embodiments, the first plate includes a flow channel ( Figure 1 The flow channel may be configured to receive a fluid, such as an oxidant, from one or more fluid inlets (schematically shown at 107 ) and distribute the fluid over the surface of the first electrode 102 .

[0034] Each plate 104 , 105 may include current connection tabs 112 , 113 through which current may flow during use.

[0035] The fuel cell unit 100 may include one or more first catalyst layers 114, 115, located between the first plate 104 and the polymer electrolyte membrane 101. The one or more first catalyst layers may be configured to provide active sites for catalytic activity of one or both of an oxygen reduction reaction (ORR) and an oxygen evolution reaction (OER). Suitable catalytic materials for the catalyst layers are described in more detail below.

[0036] In one or more examples, an OER catalyst layer can be provided at a side 114 of the first electrode facing the first plate 104. In one or more examples, an ORR catalyst layer can be provided at a side 115 of the first electrode facing the PEM 101.

[0037] In this and one or more examples, the first electrode 102 is porous and allows fluid to pass through the electrode to the PEM 101 .

[0038] The fuel cell unit 100 may include one or more second catalyst layers 116, 117 located between the second plate 105 and the polymer electrolyte membrane 101. The one or more second catalyst layers may be configured to provide active sites for catalytic activity of one or both of a hydrogen reduction reaction (HRR) and a hydrogen evolution reaction (HER).

[0039] In one or more examples, a HER catalyst layer can be provided at a side 116 of the second electrode facing the second plate 105. In one or more examples, a HRR catalyst layer can be provided at a side 117 of the second electrode facing the PEM 101.

[0040] Suitable catalytic materials for use as HER catalysts and HRR catalysts are described in more detail below.

[0041] In this example and one or more examples, the fuel cell unit 100 is configured to operate in a redox mode and a regeneration mode. In the redox mode, the fuel cell unit 100 is configured to be supplied with fuel to the second electrode 103 and with an oxidant (such as oxygen from air) to the first electrode 102 to generate an electric current between the first electrode 102 and the second electrode 103 and to generate reaction products at the first electrode 102.

[0042] In a hydrogen-based fuel cell, the fuel comprises hydrogen, the oxidant comprises oxygen or a source of oxygen from air, and the reaction products comprise water.

[0043] In regeneration mode, the fuel cell unit is configured to be provided with a reaction product, such as water in the case of a hydrogen-based fuel cell unit, to the first electrode 102. A potential difference should be provided between the first electrode 102 and the second electrode 103 by a power source (not shown), thereby producing the fuel, such as hydrogen, at the second electrode 103.

[0044] The fuel cell unit 100 may include a fuel storage material as part of or adjacent to the second electrode 103 to at least partially provide the fuel to the second electrode 103 in redox mode and / or at least partially store the fuel generated at the second electrode 103 in regeneration mode.

[0045] In this example and one or more examples, the second electrode 103 is formed of the fuel storage material. Therefore, the fuel storage material can be an integral part of the second electrode 103.

[0046] In other examples, the fuel storage material may be included in a different layer within the fuel cell unit 100 that is separate from the second electrode 103 but is disposed adjacent to the second electrode 103 (ie, at least partially between the first plate 104 and the second plate 105 ).

[0047] In one or more embodiments, the PEM is bonded to a gas diffusion layer (e.g., a carbon-based conductor, such as carbon paper, carbon cloth, or carbon fiber, preferably carbon paper), with the other side of the gas diffusion layer coated with a HER catalyst. This catalytic layer is adjacent to the anode, allowing easy electron transfer.

[0048] It has been found that this configuration is particularly advantageous when the anode acts as a fuel storage material (e.g., the N-doped graphite-coated (N-doped) carbon nanofoam and proton-conducting polymer materials described herein). In such a configuration, hydrogen evolved by the HER is also captured. When the HER is directly coated on the anode, it has been found that hot spots may occur, resulting in inefficient hydrogen storage.

[0049] In one or more embodiments, the fuel cell unit 100 includes a peripheral gasket 120, which is configured to be sandwiched between the first plate 104 and the second plate 105 and to contain at least the polymer electrolyte membrane 101, the first electrode 102, the second electrode 103, one or more first catalyst layers, and one or more second catalyst layers. The gasket 120 may be silicone rubber or vulcanized rubber. In other examples, the fuel cell unit 100 may be surrounded by a housing to contain the layers, the reactants, and the reaction products.

[0050] In one or more examples, the fuel cell unit 100 can be part of a fuel cell unit stack 121 that includes a plurality of fuel cell units arranged in series with each other. Figure 1 1 , a block 122 schematically represents a fuel cell unit adjacent to the fuel cell unit 100 in the fuel cell unit stack 121. The adjacent fuel cell unit 122 is substantially identical to the fuel cell unit 100.

[0051] Figure 1 A fuel cell unit is shown having the ability to operate in both redox mode and regeneration mode by providing appropriate catalyst layers, and having the necessary fuel storage materials. However, in one or more examples, only some of the above structures may be provided.

[0052] In one example, the fuel cell unit 100 can be configured to include the fuel storage material, but operate only in redox mode. Thus, in one or more examples, only the catalyst for promoting the redox reaction can be provided. In another example, one or more first catalysts may not be provided, and one or more second catalysts may be provided. In this example, the fuel storage material of the second electrode 103 can be "recharged" by an external fuel source, rather than being recharged by operating in regeneration mode. Thus, during "recharging", gaseous hydrogen can be provided to the second electrode 105 through the flow channels of the second plate 105, and one or more second catalyst layers 117, 116 can provide the ability to reduce the gaseous hydrogen to protons for storage in the fuel storage material.

[0053] In another example, the fuel cell unit 100 can be configured to include the fuel storage material but operate only in a redox mode. It should be understood that the first catalyst layer and the second catalyst layer are used to increase the reaction rate of the fuel cell unit, but in some applications, this may not be necessary. Therefore, in one or more examples, the fuel cell unit 100 can include the fuel storage material but not include one or more of the first catalyst layer 114, 115 and the second catalyst layer 116, 117.

[0054] In another example, the fuel cell unit 100 may be configured to operate only in a regeneration mode. Thus, one or more first catalyst layers 114 may be provided, but one or more second catalyst layers 116, 117 may not be present.

[0055] Some specific materials that may be used in fuel cell elements are described in more detail below.

[0056] (N-doped) carbon nanofoam materials

[0057] The present disclosure provides (N-doped) carbon nanofoam materials having excellent properties as components in composite materials and fuel storage materials in fuel cell units.

[0058] As used herein, the term "(N-doped)" (ie, bracketed) means that the material is optionally N-doped. Thus, "(N-doped) carbon nanofoam material" means a carbon nanofoam material that can be optionally N-doped.

[0059] As used herein, “C nf " can be used to represent carbon nanofoam materials.

[0060] As used herein, “C nf -N x " can be used to represent N-doped carbon nanofoam materials.

[0061] Carbon materials provide useful electrocatalysts due to their high surface area, high conductivity, and cost. Various types of carbon materials suitable for use as electrocatalysts are disclosed in X. Wang et al., Advanced Energy Mater., 2017, 7, 1700544.

[0062] Non-metallic atoms such as nitrogen, phosphorus, sulfur, and boron can be doped into carbon structures, resulting in a variety of possible configurations of doped carbon materials. These heteroatoms are more electronegative than carbon, which makes the neighboring carbon atoms electron-deficient, thereby promoting the adsorption of oxygen on the carbon nanostructures. Doped carbon structures can take various forms, including nanotubes, sheets, or particulate carbon materials.

[0063] Among these doped atoms, nitrogen is advantageous because it provides a stable material with a desired balance of properties. Furthermore, nitrogen doping improves the hydrogen storage properties of fuel storage materials comprising the carbon nanofoams of the present disclosure. In contrast, doping with sulfur and phosphorus typically results in carbonation, thereby producing materials with higher pH sensitivity.

[0064] The (N-doped) carbon nanofoam materials of the present disclosure may be characterized by a scaffold of agglomerated (N-doped) carbon nanofoam particles, the particles having a diameter of 0.005 μm to 25 μm.

[0065] Preferably, the diameter of the nano foam particles is 0.01 μm to 15 μm, preferably 0.01 μm to 5 μm, more preferably 0.01 μm to 2 μm.

[0066] The diameter of the nanofoam particles can be measured by SEM. Typically, in this process, the largest dimension of the particles is measured.

[0067] The average diameter can be calculated by taking the average of the measurements of the largest dimension of ten individual nanofoam particles.

[0068] The (N-doped) carbon nanofoam material disclosed herein is a continuous or semi-continuous interconnected superstructure composed of agglomerated (N-doped) carbon nanofoam particles. This superstructure can be used as a scaffold or support for the N-doped graphitic carbon in the composite material disclosed herein.

[0069] In one example, the tortuous path of the open pores of the scaffold is at least 3 times the average diameter of the nanofoam particles, preferably at least 5 times the average diameter of the nanofoam particles, such as 5 to 100 times, preferably 5 to 50 times the average diameter of the nanofoam particles.

[0070] Open pores usually have irregular shapes, e.g. Figure 2bThe pore size can be determined by SEM, where the average size of any given pore is defined as the average of the largest and smallest dimensions of the pore as determined by SEM.

[0071] The average size of the pores of the scaffold will vary depending on the particle size of the nanofoam particles and is typically 10 μm to 100 μm, such as for nanofoam particles of approximately 1 μm.

[0072] In an alternative embodiment, the average size of the pores of the scaffold is typically 0.2 μm to 2 μm.

[0073] The average pore size can be determined by averaging 10 average pore sizes as determined by SEM.

[0074] In one embodiment, the density of the (N-doped) carbon nanofoam material is 300 mg / cm 3 Below, typically 50 mg / cm 3 Up to 200mg / cm 3 , and preferably 50 mg / cm 3 Up to 150mg / cm 3 .

[0075] The density of the (N-doped) carbon nanofoam material can be measured by weighing the bulk material and then correlating the mass against the average elemental density.

[0076] Methods for preparing carbon nanofoams are known in the art, for example in Sattler et al., Carbon 95 (2015), pp. 434-441.

[0077] An example method of forming a (N-doped) carbon nanofoam material comprises:

[0078] i. forming a mixture of sugar, water and hydrocarbon mediator;

[0079] ii. heating the mixture to form carbon nanofoam; and

[0080] iii. optionally heating the carbon nanofoam in the presence of an acidic nitrogen source (eg, nitric acid) to form N-doped carbon nanofoam.

[0081] Sugars suitable for use include monosaccharides, disaccharides and trisaccharides, such as sucrose, glucose or fructose, with sucrose being preferred.

[0082] The mixture of sugar and water is highly concentrated, i.e. at least 3 molar, typically at least 4 molar, such as about 5 molar. Such a high concentration will usually require heating and vigorous stirring to completely dissolve the sugar, typically from 50°C to 85°C, for example 60°C to 80°C.

[0083] Typically, the concentrated sugar solution is cooled, for example to below 50°C, before the hydrocarbon mediator is added.

[0084] Suitable hydrocarbon mediators include aromatic hydrocarbons such as pyrene, (chrysene), benz[a]anthracene, fluoranthene, anthracene, naphthalene, benzene and hexane, of which anthracene, naphthalene and benzene are preferred, and naphthalene is most preferred.

[0085] Typically, only a small amount of hydrocarbon mediator (eg, naphthalene) is required. For example, the ratio of hydrocarbon mediator (eg, naphthalene) to sugar (eg, sucrose) is typically 1:25,000 to 1:75,000 or 1:50,000 to 1:65,000.

[0086] Step ii entails heating the mixture to form the nanofoam.The mixture is heated at a temperature and for a time sufficient to carbonize the sugar to form the particulate material.

[0087] Suitably, the mixture is heated at a temperature of 100°C to 600°C for a period of 30 minutes to 24 hours. Heating to higher temperatures generally requires shorter heating times. For example, the mixture may be heated to 500°C for 1 hour. Alternatively, the mixture may be heated to 155°C for 5 hours. It is of course possible to heat the mixture for longer periods of time, but this is generally not necessary.

[0088] Preferably, the mixture is heated at a temperature of 350° C. to 600° C. for 30 minutes to 3 hours. Alternatively, the mixture is heated at a temperature of 100° C. to 300° C. for 4 hours to 12 hours.

[0089] The heating step carbonizes the material, forming the nanofoam. Therefore, the heating is typically performed in a suitable inert container (e.g., a Teflon-coated hydrothermal reactor).

[0090] The heating step is preferably performed in a sealed reactor.

[0091] The produced nanofoam can optionally be comminuted, for example by grinding. Grinding can be performed in a ball mill.

[0092] The resulting material is a scaffold of agglomerated (N-doped) carbon nanofoam particles. The (N-doped) carbon nanofoam particles are typically mesoporous, i.e., have pores ranging from 2 nm to 50 nm. The nanofoam particles are bound together by covalent interactions, resulting in a scaffold that surprisingly remains even under mechanical stress, such as during grinding.

[0093] The pore size of mesopores can be determined by tunnel electron microscopy. In this process, the material can be coated by sputtering with metals such as titanium. After coating, the pore structure can be observed using a tunnel electron microscope, where the pore size can be determined based on the image produced. Although the method provides an image on the surface, it is apparent from the bulk reactivity of the material that the pores extend into the carbon structure below the surface. Therefore, the material is best described as mesoporous (N-doped) carbon nanofoam.

[0094] The shape of the nanofoam particles can vary and may depend on the sugar and hydrocarbon mediators used. For example, glucose and naphthalene form cube-like structures.

[0095] Sucrose and naphthalene are preferred and produce approximately spherical particles.

[0096] The diameter of the nano foam particles is generally 0.01 μm to 15 μm, preferably 0.01 μm to 5 μm, more preferably 0.01 μm to 2 μm.

[0097] Step iii comprises N-doping by heating the carbon nanofoam with an acidic nitrogen source such as nitric acid (HNO 3 ), nitrous acid (HNO 3 ), hyponitrous acid (H 2 N 2 O) or a mixture thereof, wherein nitric acid is preferred.

[0098] Typically, the carbon nanofoam is heated to at least 80°C for at least 2 hours, such as to at least 90°C for at least 4 hours, preferably to 95 to 115°C for at least 4 hours.

[0099] Heating is typically performed in a suitable acid-resistant pressure vessel (eg, a Teflon hydrothermal reactor).

[0100] The acidic nitrogen source (eg, nitric acid) should be sufficiently concentrated to ensure sufficient N-doping levels. Suitable concentrations (eg, nitric acid concentration) include 3 molar to 10 molar, preferably 4 molar to 8 molar.

[0101] Treatment of carbon nanofoam particles with nitric acid or alternative acidic nitrogen sources introduces nitrogen doping into the structure, forming a mixture of pyridinic, pyrrolic, and graphitic nitrogen sites. However, when using nitric acid or alternative acidic nitrogen sources, the acidic conditions also form carboxylate groups at the surface of the material. In addition, surface pitting may occur, resulting in some loss of mesoporous structure. Therefore, it is necessary to control the conditions to provide the desired amount of doping while avoiding excessive degradation of the mesoporous structure. However, the process is gentle enough to ensure that the condensed particle scaffold is retained.

[0102] Typically, the surface pore size is approximately 2% to 10% larger after treatment with nitric acid or an alternative acidic nitrogen source.

[0103] Typically, the N content of the resulting material is 0.1 wt% to 8 wt%, such as 0.5 wt% to 6 wt% or 1 wt% to 5 wt%. Preferably, the N content of the resulting material is 2 wt% or greater.

[0104] The surface area of ​​the material produced is typically 200m 2 / g to 3500m 2 / g, preferably 400m 2 / g to 3000m 2 / g, preferably 800m 2 / g to 2500m 2 / g, preferably 800-2000m 2 / g. For example, 900m 2 / g to 2000m 2 / g, preferably 900m 2 / g to 1500m 2 / g.

[0105] The surface area can be measured, for example, by the BET isotherm at 77 K using nitrogen.

[0106] The above process is an exemplary method for forming N-doped carbon nanofoam. Alternative methods are possible. For example, a mesoporous structure can be obtained by heating a mixture of sugar, water, and a hydrocarbon mediator. If a nitrogen source is included in the mixture, this can form N-doped carbon nanofoam without the need for step iii (treatment with an acidic nitrogen source).

[0107] Composite materials

[0108] The present disclosure further provides a composite material comprising a composite particle superstructure, wherein the superstructure comprises a condensed (N-doped) carbon nanofoam particle scaffold and a coating on the scaffold, the coating comprising N-doped graphitic carbon. The condensed (N-doped) carbon nanofoam particle scaffold is as described above and can itself be optionally N-doped, for example, by treatment with an acidic nitrogen source (such as nitric acid).

[0109] The N-doped graphitic carbon coating can be formed by treating a coagulated nanofoam particle scaffold with a structural protein to coat the (N-doped) carbon nanofoam scaffold with N-doped graphitic carbon. This step can be performed on a (N-doped) carbon nanofoam particle scaffold (e.g., formed after treatment with an acidic nitrogen source) or a coagulated (N-doped) carbon nanofoam particle scaffold (i.e., the scaffold material is not N-doped).

[0110] During formation, the (N-doped) carbon nanofoam scaffold provides a template for the growth of the N-doped graphite phase. The N-doped graphite phase is typically located on the surface of the (N-doped) carbon nanofoam scaffold, such as on the outer and inner surfaces, such as within the open pores.

[0111] Prior to coating with the N-doped graphitic carbon phase, the composite material generally retains the same overall structure as that of the agglomerated particles of the (N-doped) carbon nanofoam scaffold used as a template.

[0112] Composite materials can therefore be described as comprising composite particles.

[0113] Thus, the composite particles comprise a continuous or semi-continuous (N-doped) carbon nanofoam scaffold coated with N-doped graphitic carbon. The N-doped graphitic phase is typically located on the surface of the (N-doped) carbon nanofoam scaffold, such as on the outer and inner surfaces, such as within the open pores.

[0114] The composite particles are agglomerated by the (N-doped) carbon nanofoam scaffold to form a composite material superstructure. That is, the (N-doped) carbon nanofoam scaffold interconnects the composite particles to form a superstructure.

[0115] The agglomerated composite particle superstructure may also contain N-doped graphitic carbon located on the available surfaces.

[0116] In the context of this disclosure, "N-doped graphitic carbon" refers to graphitic carbon with nitrogen atoms pinned to the graphite plane. These nitrogen atoms form graphitic sites (i.e., replacing carbon and having three bonds), pyridinic sites (i.e., replacing carbon and having two bonds, thereby forming a six-membered ring), and pyrrolic sites (i.e., replacing carbon and having two bonds, thereby forming a five-membered ring) within the graphite plane. Due to the reduced number of atoms, the pyridinic and pyrrolic sites within the graphite plane can lead to defects or open sites within the plane.

[0117] Preferably, the diameter of the composite particles is from 0.005 μm to 25 μm. For example, the diameter of the composite particles is from 0.01 μm to 15 μm, such as from 0.01 μm to 5 μm or from 0.01 μm to 2 μm.

[0118] Smaller particles have a much higher surface area and are generally preferred.

[0119] Preferably, the composite particles have a diameter of 100 nm or less, such as 50 nm or less, or 30 nm or less, for example 25 nm or less or 20 nm or less.Preferably, the composite particles have a diameter of 10 nm to 30 nm.

[0120] The composite particles tend to aggregate and form clusters. Typically, the clusters have a diameter of 1 μm to 10 μm, for example, 2 μm to 8 μm or 3 μm to 6 μm.

[0121] For example, when the composite particles are about 20 nm, the diameter of the aggregate clusters may be about 3 μm to 6 μm.

[0122] The diameter of composite particles and clusters can be measured by TEM. Typically, in this process, the largest dimension of the particles / clusters is measured.

[0123] The formation of composite materials typically involves:

[0124] - Heating (N-doped) carbon nanofoam materials together with structural proteins in an oxygen-reduced environment.

[0125] Thus, an exemplary method of forming a composite material comprises:

[0126] a. forming a mixture of sugar, water and hydrocarbon mediator;

[0127] b. heating the mixture to form a carbon nanofoam material;

[0128] c. optionally heating the carbon nanofoam in an acidic nitrogen source (eg, nitric acid) to form N-doped carbon nanofoam;

[0129] d. optionally crushing the (N-doped) carbon nanofoam material;

[0130] e. heating the (N-doped) carbon nanofoam material together with the structural protein in an oxygen-reduced environment to form a composite material;

[0131] f. optionally treating the composite material with a pitting agent to form an activated composite material; and

[0132] g. Optionally comminuting the composite material.

[0133] Steps e. to g. can be repeated as needed until the desired amount of N-doped graphite regions is obtained and the desired active surface area is achieved.

[0134] Steps a., b., and c. are identical to steps i., ii., and iii. of the exemplary method for forming (N-doped) carbon nanofoam materials.

[0135] Step d. is optional but is typically performed to ensure that a more consistent material is used as a scaffold for forming the N-doped graphitic carbon. Suitable comminution methods include grinding, such as ball milling.

[0136] Step e. involves heating the produced nanofoam together with the structural protein in an oxygen-reduced environment to form an N-doped graphite coating on the (N-doped) carbon nanofoam.

[0137] The reduced oxygen environment can be achieved by any means, but preferably an inert atmosphere (such as argon) or a vacuum is used.

[0138] The mixture is heated to an elevated temperature for a relatively short period of time. Extended heating at the temperature required to achieve N-doping is possible, but generally not necessary.

[0139] Typically, step e. involves heating at a temperature of at least 400°C for at least 10 minutes, such as from 450°C to 900°C for from 10 minutes to 3 hours, preferably from 500°C to 600°C for from 30 minutes to 90 minutes.

[0140] Heating at high temperatures, such as above 1000° C., graphitizes the structural protein, resulting in the formation of bulk graphite. The temperatures used in step e. involve lower temperatures, resulting in partial graphitization.

[0141] The resulting material contains N-doped graphitic carbon coated on the (N-doped) carbon nanofoam, for example on the exterior and interior surfaces, such as within the open pores.

[0142] Optional step f. involves treating the resulting material with a pitting agent to form an activated composite material. In the context of this disclosure, a "pitting agent" refers to a substance that activates the composite material, for example, by increasing the surface area. For example, step f. can produce pits or indentations on the surface of the composite material, thereby providing a larger active surface area.

[0143] A composite material that has undergone pitting corrosion may be described as an "activated composite material."

[0144] Suitable pitting agents include alkali or alkaline earth carbonates, alkali or alkaline earth hydroxides, such as NaOH, KOH, Na2CO3, K2CO3, or mixtures thereof.

[0145] Alternatively, acidic pitting agents such as H2SO4, HCl, HNO3, H3PO4 and mixtures thereof may be used.

[0146] Preferably, the pitting agent is an alkali or alkaline earth carbonate. When using an alkali or alkaline earth carbonate pitting agent, regular and consistent pitting is achieved. Typically, alkali or alkaline earth carbonate pitting agents increase the number of mesopores within the material, wherein the mesopores have smooth or rounded edges. Rounded mesopores are particularly advantageous for hydrogen storage by physical adsorption.

[0147] In contrast, when acidic pitting agents are used, pitting is more random, and the newly formed indentations may have jagged edges and irregular shapes.

[0148] Preferably, the pitting agent is K2CO3.

[0149] The pitting agent should be included in an amount sufficient to increase the activated surface area, which generally requires an excess of the pitting agent (by weight). For example, the weight ratio of the composite material to the pitting agent can be 1:1.5 or greater, such as 1:2 to 1:10, 1:2.5 to 1:8, or 1:3 to 1:5. Preferably, the weight ratio of the composite material to the pitting agent is 1:3.

[0150] Step f. should be performed at elevated temperature in an oxygen-reduced environment. Typically, step f. is performed at a temperature of at least 600° C. for at least 10 minutes, such as at 650-1000° C. for 10 minutes to 3 hours, and preferably at 750-850° C. for 1 hour.

[0151] Optional step g. can be performed by grinding. This step breaks away any loosely bound graphite material, leaving behind a composite particle superstructure comprising a condensed (N-doped) carbon nanofoam scaffold and an N-doped graphite coating.

[0152] The N-doped graphite material is preferably covalently bonded to the scaffold.

[0153] Typically, the N content of the resulting material is 0.1 wt% to 8 wt%, such as 0.5 wt% to 6 wt% or 1 wt% to 5 wt%. Preferably, the N content of the resulting material is 2 wt% or greater.

[0154] The surface area of ​​the material produced is typically 200m 2 / g to 3500m 2 / g, preferably 400m 2 / g to 3000m 2 / g, preferably 800m 2 / g to 2500m 2 / g, preferably 800-2000m 2 / g. For example, 900m 2 / g to 2000m 2 / g, preferably 900m 2 / g to 1500m 2 / g.

[0155] When using pitting agents, the surface area of ​​the material produced can be 25% to 50% higher than the surface area of ​​the same material before pitting. The amount of surface area increase will depend on the volume / concentration of the pitting agent, the temperature at which the pitting is performed, the length of the pitting step, and the type of pitting agent used.

[0156] Any suitable structural protein may be used, such as keratin or collagen, with keratin being preferred. The structural protein should preferably be dried and in a form that allows intimate mixing with the carbon particles, such as a powdered form.

[0157] Suitable collagen materials that may be used include gelatin.

[0158] Any source of keratin may be used, including hair, nails, feathers, horns, claws, whiskers, or hooves.

[0159] Preferably, the structural protein is avian feathers. Avian feathers are highly porous and it has been found that after carbonization to form the N-doped graphite coating, the resulting material retains its porosity.

[0160] Any suitable poultry feathers may be used, with farmed birds such as chickens, turkeys, ducks and geese being particularly suitable due to their availability.

[0161] Down feathers are preferred, particularly goose and duck down.

[0162] Typically, avian feathers are mixed with (N-doped) carbon nanofoam in a weight ratio of nanofoam to feathers of 2:1 to 1:4, preferably in a weight ratio of 3:2 to 1:3.

[0163] After formation of the coating, the resulting material may optionally be comminuted, for example by grinding.

[0164] OER, ORR, HER, HRR catalytic materials

[0165] Various types of catalytic materials for fuel cell cells are known. For example, X. Wang et al., Advanced Energy Materials, 2017, 7, 1700544, C. Zhang et al., Frontiers in Energy, 2017, 11, 268-285, and N. Alonso-Vante et al., Catalysts, 2018, 8, 559 provide overviews.

[0166] In some embodiments, a bifunctional catalyst may be used in a fuel cell unit. A bifunctional catalyst is a catalyst that can catalyze two different types of reactions.

[0167] In some cases, ORR and OER can be catalyzed by the same bifunctional catalyst.

[0168] In some cases, OER and HER can be catalyzed by the same bifunctional catalyst.

[0169] In the case of bifunctional catalysts, heterojunctions can be employed to separate the positive and negative charges in the organic material.

[0170] It is well known that noble metal-based electrocatalysts (Pt, Ir, and Ru-based) catalyze ORR, OER, and HER reactions.

[0171] Platinum group metals are known to be used as electrocatalysts, with platinum being the most commonly used for electrocatalysis. However, due to concerns about the durability of platinum use worldwide, research has been conducted on new platinum group metal alloy nanoparticles supported on conductive substrates such as carbon, carbon black, oxides, single-walled carbon nanotubes, and carbon nanofibers.

[0172] Such platinum group metal alloys can be described as Pt-M (where M = 3d transition metal) alloy nanoparticles. For example, where M is one or more of Ni, Co, Fe, Cu, Pd, Rh, Ti, V, Cr, Mo, W, and Re. For example, PtNi3, Pt x Co (where x = 2, 3, 5, 7 and 9), Pt3Cu, PtCu and PtCu3.

[0173] In some cases, ternary Pt-based systems may also be suitable catalysts. For example, a catalyst may be described as Pt-MN, where M is as defined above and N is Fe, Cu, Ni, or Co. For example, Pt2CuNi, Pt3CoNi, Pt3FeNi, and Pt3FeCo.

[0174] Transition metal-based catalysts are also known to be suitable electrocatalysts for ORR, OER, and HER, for example, catalysts based on Ti, V, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, or mixtures thereof, such as Mn, Co, Ni, and Fe oxides.

[0175] Preferably, the transition metal is selected from Co, Fe, Ni or mixtures thereof.

[0176] Preferably, the transition metal is Co.

[0177] Suitable cobalt-based catalysts include, but are not limited to, cobalt oxide, cobalt phosphide, cobalt halide, cobalt nitrate, cobalt chalcogenides (sulfides and selenides), Co-containing layered double hydroxides, Co-NC, Co-based single atoms, Co-MOF (metal-organic framework), cobalt carboxylates, Co-Nx / C, and composites thereof.

[0178] Fuel storage materials

[0179] The present disclosure further provides a fuel storage material, particularly for use in a fuel cell unit, comprising a proton conducting polymer material and a composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0180] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0181] A coating on the bracket comprises N-doped graphitic carbon.

[0182] The (N-doped) carbon nanofoam material coated with N-doped graphitic carbon is preferably as described herein.

[0183] Proton conducting polymer materials are typically capable of conducting protons at room temperature (ie, at 25°C).

[0184] "Proton-conducting" means a proton conductivity greater than 10 -3 S / cm, preferably greater than 10 -2 S / cm. Of course, the proton conductivity of the polymer itself in its dry form may be very poor. The proton conductivity of the polymer material is measured on the hydrated and (if necessary) acidified polymer.

[0185] The proton conducting polymer material may be an acid-doped hydrogel.

[0186] When the hydrogel is doped with a suitable acid, such as phosphoric acid or sulfuric acid, the resulting polymer material exhibits very high proton conductivity.

[0187] Suitable levels of acid dopant in the hydrogel are from 5 wt% to 25 wt%, preferably from 10 wt% to 20 wt%.

[0188] Suitable hydrogels are selected from polyvinyl alcohol, poly(meth)acrylates, collagen, gelatin and fibrin.

[0189] Preferred hydrogel polymers are selected from poly(meth)acrylates and gelatin, with polyacrylates being particularly preferred.

[0190] The fuel storage material typically contains less than 15 wt% acid-doped hydrogel, preferably 0.1 wt% to 12 wt%, more preferably 0.2 wt% to 10 wt%, more preferably 0.5 wt% to 8 wt% acid-doped hydrogel.

[0191] The proton conducting polymer material may be a fluorinated acid polymer, preferably a fluorinated acid polymer as described herein.

[0192] Preferably, the fluorinated acid polymer in the fuel storage material has the formula X:

[0193]

[0194] in

[0195] Each c is independently 0 or an integer from 1 to 3;

[0196] N is at least 4;

[0197] R f 3 and R f 4 independently selected from F, Cl or a highly fluorinated alkyl group having 1 to 10 carbon atoms,

[0198] a = 0, 1, or 2, and

[0199] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0200] Preferably, the fluorinated acid polymer in the fuel storage material comprises a perfluorocarbon backbone and side chains represented by the formula

[0201] -O-CF2CF(CF3)-O-CF2CF2SO3E 5

[0202] in

[0203] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0204] Preferably, the fluorinated acid polymer in the fuel storage material has the formula XI:

[0205]

[0206] in

[0207] Each c is independently 0 or an integer from 1 to 3;

[0208] n is at least 4; and

[0209] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0210] The fuel storage material typically contains less than 5 wt% fluorinated acid polymer, for example 0.05 to 5 wt%, preferably 0.1 to 4 wt%, more preferably 0.1 to 3 wt%, more preferably 0.2 to 2 wt% fluorinated acid polymer.

[0211] In one example, a method of preparing a fuel storage material includes:

[0212] A paste is formed of a composite material comprising a proton-conducting polymer material and a dispersant.

[0213] A composite particle superstructure, wherein the superstructure comprises a scaffold of agglomerated (N-doped) carbon nanofoam particles and a coating on the scaffold, the coating comprising N-doped graphitic carbon;

[0214] Compressing the paste into a compacted form; and

[0215] The compacted form is allowed to dry.

[0216] Typically, pastes are formed using water as a dispersant.

[0217] When the proton-conducting polymer material is an acid-doped hydrogel, the forming step may comprise:

[0218] forming a mixture of a hydrogel-forming polymer, an acid dopant, and a composite material;

[0219] lyophilizing the mixture; and

[0220] Water is added to form a paste composed of the freeze-dried conductive polymer material and the composite material.

[0221] The freeze-drying step improves the structural integrity of the hydrogel, allowing it to maintain better proton conductivity when incorporated into fuel storage materials.

[0222] Typically, the drying step involves heating the compacted form at a temperature high enough to facilitate removal of the dispersant but low enough not to damage the proton-conducting polymeric material.

[0223] When a fluorinated acid polymer is used as the proton conducting material, suitable temperatures include 50° C. to 250° C., such as 100° C. to 200° C. Heating can be performed in a flowing gas stream to facilitate removal of the dispersant.

[0224] When using acid-doped hydrogels as the proton conducting material, it is generally preferred to avoid heating to high temperatures during the drying step, as these hydrogels tend to be less stable at high temperatures. Preferably, the drying step comprises drying at a temperature not greater than 75°C.

[0225] Optionally, after drying, the material may be degassed, for example in a vacuum oven.

[0226] The fuel storage material may further comprise an Arrhenius acid to facilitate the uptake and storage of protons. Any Arrhenius acid may be used, with suitable acids including sulfuric acid, phosphoric acid, and nitric acid. The Arrhenius acid added to the fuel cell unit is also referred to as a "polymer activator."

[0227] For hydrogel-based proton conducting materials, the acid is preferably phosphoric acid.

[0228] For proton-conducting materials based on fluorinated polymeric sulfonic acids, the acid is preferably sulfuric acid.

[0229] The material can be loaded with an Arrhenius acid by soaking the material in a solution of the acid for a sufficient period of time (eg, at least 4 hours).

[0230] After loading with acid, the material can be dried to remove most of the water, however, it is beneficial to retain a low degree of hydration to ensure adequate proton conductivity. Residual water within the material aids in the transport and retention of hydrogen ions, which interact with water to form hydronium ions.

[0231] Typically, the fuel storage material contains at least 0.01 wt% water, preferably at least 0.1 wt% water, for example 0.01 to 5 wt% water, preferably 0.1 to 2 wt% water.

[0232] Without wishing to be bound by theory, the N-doped graphitic carbon phase promotes chemisorption of hydronium ions within the fuel storage material, where nitrogen sites (particularly pyridinic and pyrrolic sites) are able to hydrogen bond with the ions, thereby securing them on the surface of the material.

[0233] "Hydroxy ion" means protonated water, i.e. H3O + The fuel storage material of the present disclosure can store hydronium ions themselves, or solvated forms of hydronium ions, such as H5O2 + 、H7O3 + 、H9O4 + or a mixture thereof.

[0234] It is believed that charge balance is achieved by storing negative charges within the graphitic material, which is further facilitated and stabilized by the electronegativity of the nitrogen atoms and the overall high electrical conductivity of the material.

[0235] In an operating fuel cell cell, the released hydronium ions migrate to the PEM, where the protons pass through the PEM to the counter electrode where they react with oxygen to form water.

[0236] Without wishing to be bound by theory, the fuel storage material also stores hydrogen by physical adsorption within the mesopores of the (N-doped) carbon nanofoam. Therefore, as the concentration of hydronium ions increases, storing additional hydrogen in the form of hydronium ions becomes less preferred, as the charge balance in the case of hydronium ions resides within the graphite material. Instead, dihydrogen is formed, and after the pressure increases to a sufficient level (e.g., greater than about 5 bar), this dihydrogen condenses within the mesopores of the (N-doped) carbon nanofoam. Within the mesopores, the hydrogen is in a quasi-liquid state. The liquefied hydrogen adheres to the fuel storage material by physical adsorption to the surfaces of the mesopores. Typically, hydrogen liquefaction occurs at high pressure (e.g., 300 bar), however, confined liquefaction occurs within the mesopores of the (N-doped) carbon nanofoam, which promotes liquefaction at much lower pressures (e.g., about 5 bar).

[0237] Nitrogen doping of carbon nanofoams further promotes physical adsorption due to the electronegativity of nitrogen atoms, thereby promoting the formation of van der Waals interactions between hydrogen and the nitrogen-doped carbon nanofoam. To improve the hydrogen storage properties of fuel storage materials, increasing the number of mesopores within the carbon nanofoam and increasing the nitrogen doping level are both beneficial.

[0238] The dominant hydrogen storage mechanism within a fuel storage material depends on the temperature and pressure of the system. Typically, chemisorption dominates at pressures below 5 bar and temperatures typically below 80°C, and physisorption dominates at pressures of 5 bar and above and temperatures typically 80°C and above. However, it is common to store hydrogen by both chemisorption and physisorption simultaneously.

[0239] Surprisingly, the fuel storage material is capable of storing hydrogen at levels above 1 wt%, such as above 1.5 wt%, or above 1.8 wt%, or even above 2 wt%.

[0240] Measurement plan

[0241] Calculate pore size

[0242] To calculate the pore diameters at the micropore level and smaller levels, the inventors used the protocol described in Kawazoe et al., J. Chem. Eng. Japan, 16(6), 1983, 470-475.

[0243] The above scheme describes a method for calculating the effective pore size distribution from the adsorption isotherm. The pore size distribution is calculated based on the N2 isotherm at 77K.

[0244] To measure the N2 isotherm at liquid N2 temperature, a sample (about 0.3 g) was placed in a sample holder and heated at 200 °C and 10 -5 Pallet (1.33 x 10 -3 The samples were degassed at a pressure of 1.33 × 10 Pa for at least 48 hours. A Cahn electronic balance provided highly accurate mass measurements. To measure pressure, an ULVAC ionization vacuum gauge and an MKS Baratron sensor (pressure range 1.33 × 10 -6 –6.65x 10 -1 Pa; 1.33x 10 -1 -10 5 Pa).

[0245] To calculate the volume of pores larger than 1.5 nm, the inventors used the following protocol: Dollimore, D. and GR Heal et al., J. AppL Chem., 14, 1964, 109-114.

[0246] The above protocol describes a method for calculating pore size distribution on porous solids from adsorption isotherms.

[0247] Here, the total amount of nitrogen taken up at a pressure of 1 atmosphere and a temperature of 77 K gives the total pore volume. In the case of a model with cylindrical pores, the total pore volume is calculated using:

[0248] 1 / 4*pi*d*d*l,

[0249] in

[0250] d is the average pore diameter, and

[0251] l is the total length of the pore.

[0252] If the BET surface area measures the total surface area of ​​the pores, then BET surface area S(BET) = pi*d*l. I is eliminated from both equations, and the average diameter d is calculated.

[0253] The Barrett-Joiner-Halenda (BJH) code assumes that liquid nitrogen undergoes capillary condensation within pores. The calculation considers both the nitrogen adsorption layer and the pore size distribution of capillary condensed nitrogen at a given relative pressure based on relative pressure and adsorption isotherms. The adsorption and desorption branches result in different pore size distributions. Therefore, the desorption branch is typically used.

[0254] Surface area

[0255] The samples were treated at elevated temperature (120°C) and reduced pressure for at least 8 hours before nitrogen adsorption to remove any bound gases and adsorbed water from the material.

[0256] N2 adsorption analysis can be performed using a Belsorp Mini (Bel Japan, Inc.) apparatus at 77 K using liquid gas for each respective test, and the adsorption data is used to calculate the surface area using the Brunauer-Emmett-Teller (BET) theory.

[0257] Calculating the density of carbon nanofoam

[0258] The following methods were used:

[0259] Displacement density method: Density was calculated using water as the displacement medium at 22°C, 1 atm pressure and the equation D = m / v (mass divided by volume).

[0260] The tap density method is described as follows:

[0261] The International Pharmacopoeia, s.3.6. Bulk Density and Tapped Density of Powders, QAS11-450 FINAL (revised in March 2012). Tapped density is the increased bulk density obtained after mechanically tapping the container containing the powder sample.

[0262] Here, tap density is obtained by mechanically tapping a graduated cylinder containing the sample until almost no further volume change is observed. Different methods can be used to perform tapping. The tap density is calculated as the mass of the powder divided by the final volume.

[0263] The two measurements were then averaged.

[0264] Conductivity of crushed material samples

[0265] The material sample was prepared using spin coating. The material sample was prepared in the same manner as the electrode preparation steps. Specifically, the silver foil was placed in a solution containing the material sample and 5% of a binder.

[0266] If the resistance of the material sample is in the kilo-ohms or above, use a two-point probe.

[0267] The spin-coated film was mounted in a metal sample holder, and a vacuum was created inside to remove moisture.

[0268] Both 2-point and 4-point probe testing are available.

[0269] The measured conductivity of the samples ranged from 0.4 S / cm to 100 S / cm on average, depending on the layer thickness and conductivity of the carbon support used.

[0270] Unless the context indicates otherwise, preferences, options and embodiments of a given aspect, feature or parameter of the invention should be considered to have been disclosed in conjunction with any and all preferences, options and embodiments of all other aspects, features and parameters of the invention. Embodiments and features of the invention are also summarized in the following items.

[0271] A1. A (N-doped) carbon nanofoam material comprising a scaffold of agglomerated (N-doped) carbon nanofoam particles, preferably wherein the particles have a diameter of 0.005 μm to 25 μm.

[0272] A2. The (N-doped) carbon nanofoam material according to A1, wherein the diameter of the (N-doped) carbon nanofoam particles is 0.01 μm to 15 μm.

[0273] A3. The (N-doped) carbon nanofoam material according to item A1 or A2, wherein the diameter of the (N-doped) carbon nanofoam particles is 0.01 μm to 5 μm.

[0274] A4. The (N-doped) carbon nanofoam material according to any one of items A1 to A3, wherein the diameter of the (N-doped) carbon nanofoam particles is 0.01 μm to 2 μm.

[0275] A5. The (N-doped) carbon nanofoam material according to any one of items A1 to A4, wherein the (N-doped) carbon nanofoam particles are mesoporous.

[0276] A6. The (N-doped) carbon nanofoam material of any one of A1 to A5, wherein the material is a scaffold of agglomerated (N-doped) carbon nanofoam particles, the tortuous path of the open pores of the scaffold being at least 3 times the average diameter of the nanofoam particles.

[0277] A7. The (N-doped) carbon nanofoam material according to any one of items A1 to A6, wherein the average pore size of the open pores of the scaffold is 10 μm to 100 μm.

[0278] A8. The (N-doped) carbon nanofoam material according to A7, wherein the average pore size of the open pores of the scaffold is 0.2 μm to 2 μm.

[0279] A9. The (N-doped) carbon nanofoam material according to any one of A1 to A8, wherein the density of the material is 300 mg / cm 3 the following.

[0280] A10. The (N-doped) carbon nanofoam material according to item A9, wherein the density of the material is 50 mg / cm 3 Up to 200mg / cm 3 .

[0281] A11. The (N-doped) carbon nanofoam material according to item A10, wherein the density of the material is 50 mg / cm 3 Up to 150mg / cm 3 .

[0282] A12. The (N-doped) carbon nanofoam material according to any one of items A1 to A11, wherein the N content of the (N-doped) carbon nanofoam is 0.1 wt% to 8 wt%.

[0283] A13. The (N-doped) carbon nanofoam material according to any one of items A1 to A12, wherein the N content of the (N-doped) carbon nanofoam is 1 wt% to 5 wt%.

[0284] A14. The (N-doped) carbon nanofoam material according to any one of items A1 to A13, wherein the N content of the (N-doped) carbon nanofoam is 2 wt% or more.

[0285] A15. The (N-doped) carbon nanofoam material according to any one of A1 to A14, wherein the surface area of ​​the (N-doped) carbon nanofoam is 400 m 2 / g to 3000m 2 / g.

[0286] A16. The (N-doped) carbon nanofoam material according to any one of A1 to A14, wherein the surface area of ​​the (N-doped) carbon nanofoam is 900 m 2 / g to 2000m 2 / g.

[0287] A17. The (N-doped) carbon nanofoam material according to any one of A1 to A14, wherein the surface area of ​​the (N-doped) carbon nanofoam material is 900 m 2 / g to 1500m 2 / g.

[0288] A18. The (N-doped) carbon nanofoam material according to any one of items A1 to A17, wherein the (N-doped) carbon nanofoam is an N-doped carbon nanofoam material.

[0289] B1. A method for forming an (N-doped) carbon nanofoam material, the method comprising:

[0290] i. forming a mixture of sugar, water and hydrocarbon mediator;

[0291] ii. heating the mixture to form carbon nanofoam; and

[0292] iii. optionally heating the carbon nanofoam in the presence of an acidic nitrogen source to form N-doped carbon nanofoam.

[0293] B2. The method according to item B1, wherein the sugar is one or more monosaccharides, disaccharides and / or trisaccharides.

[0294] B3. The method according to item B2, wherein the sugar is one or more of sucrose, glucose or fructose.

[0295] B4. The method according to item B3, wherein the sugar is sucrose.

[0296] B5. A method according to any one of items B1 to B4, wherein the concentration of the sugar and water solution is at least 3 mol / dm 3 .

[0297] B6. A method according to any one of items B1 to B5, wherein the concentration of the sugar and water solution is at least 4 mol / dm 3 .

[0298] B7. A method according to any one of items B1 to B6, wherein the concentration of the sugar and water solution is at least 5 mol / dm 3 .

[0299] B8. The method according to any one of items B1 to B7, wherein the solution is completely dissolved in the water to form a mixture of sugar and water.

[0300] B9. The method according to item B8, wherein the sugar is dissolved in the water by heating and vigorous stirring.

[0301] B10. The method according to item B9, wherein the sugar is dissolved in water by heating the solution from 50°C to 85°C.

[0302] B11. The method according to item B9, wherein the sugar is dissolved in water by heating the solution from 60°C to 80°C.

[0303] B12. The method of any one of items B5 to B11, wherein the solution of sugar and water is cooled before adding the hydrocarbon mediator.

[0304] B13. The method according to item B12, wherein the solution of sugar and water is cooled to below 50°C before adding the hydrocarbon mediator.

[0305] B14. The method according to any one of items B1 to B13, wherein the hydrocarbon mediator is an aromatic hydrocarbon.

[0306] B15. The method according to item B14, wherein the aromatic hydrocarbon is pyrene.

[0307] B16. The method according to item B14, wherein the aromatic hydrocarbon is

[0308] B17. The method according to item B14, wherein the aromatic hydrocarbon is benz[a]anthracene.

[0309] B18. The method according to item B14, wherein the aromatic hydrocarbon is fluoranthene.

[0310] B19. The method according to item B14, wherein the aromatic hydrocarbon is anthracene.

[0311] B20. The method according to item B14, wherein the aromatic hydrocarbon is naphthalene.

[0312] B21. The method according to item B14, wherein the aromatic hydrocarbon is benzene.

[0313] B22. The method according to item B14, wherein the aromatic hydrocarbon is hexane.

[0314] B23. The method according to any one of items B1 to B13, wherein the hydrocarbon mediator is one or more of the aromatic hydrocarbons of items B15 to B22.

[0315] B24. The method of item B1, wherein the hydrocarbon mediator is naphthalene and the sugar is sucrose.

[0316] B25. The method according to any one of items B1 to B24, wherein the ratio of hydrocarbon mediator to sugar is 1:25,000 to 1:75,000.

[0317] B26. The method according to any one of items B1 to B25, wherein the ratio of hydrocarbon mediator to sugar is 1:50,000 to 1:65,000.

[0318] B27. The method of any one of items B1 to B26, wherein step ii is carried out at a temperature and for a time sufficient to carbonize the sugar to form the particulate material.

[0319] B28. The method according to item B27, wherein step ii is carried out at a temperature of 100°C to 600°C for 30 minutes to 24 hours.

[0320] B29. The method according to item B28, wherein step ii is carried out at a temperature of 350°C to 600°C for 30 minutes to 3 hours.

[0321] B30. The method according to item B29, wherein step ii is carried out at a temperature of 100°C to 300°C for 4 to 12 hours.

[0322] B31. The method according to any one of items B1 to B30, wherein step ii is carried out in an inert container.

[0323] B32. The method according to any one of items B1 to B31, wherein step ii is carried out in a sealed reactor.

[0324] B33. The method according to any one of items B1 to B32, wherein the nanofoam produced in step ii is crushed.

[0325] B34. A method according to item B33, wherein the (N-doped) carbon nanofoam particles condense to form a scaffold.

[0326] B35. A method according to B33 or B34, wherein the (N-doped) carbon nanofoam particles are mesoporous.

[0327] B36. The method according to any one of items B33 to B35, wherein the carbon nanofoam particles formed in step ii have a diameter of 0.1 μm to 25 μm.

[0328] B37. The method according to any one of items B33 to B36, wherein the carbon nanofoam particles formed in step ii have a diameter of 0.2 μm to 15 μm.

[0329] B38. The method according to any one of items B33 to B37, wherein the carbon nanofoam particles formed in step ii have a diameter of 0.5 μm to 5 μm.

[0330] B39. The method according to any one of items B33 to B38, wherein the carbon nanofoam particles formed in step ii have a diameter of 0.5 μm to 2 μm.

[0331] B40. The method according to any one of items B1 to B39, wherein the carbon nanofoam in step iii is heated to at least 80° C. for at least 2 hours.

[0332] B41. The method according to any one of items B1 to B40, wherein the carbon nanofoam in step iii is heated to at least 90° C. for at least 4 hours.

[0333] B42. The method according to any one of items B1 to B41, wherein the carbon nanofoam in step iii is heated to between 95° C. and 115° C. for at least 4 hours.

[0334] B43. A method according to any one of items B1 to B42, wherein step iii is carried out in a suitable acid-resistant pressure vessel.

[0335] B44. A method according to any one of items B1 to B43, wherein the acidic nitrogen source is nitric acid.

[0336] B45. The method according to item B44, wherein the nitric acid used in step iii is 3 mol / dm 3 to 10 mol / dm 3 .

[0337] B46. The method according to item B44, wherein nitric acid is used in step iii, and the concentration of the nitric acid is 4 mol / dm 3 to 8 mol / dm 3 .

[0338] B47. The method according to any one of items B1 to B46, wherein the N content of the (N-doped) carbon nanofoam is 0.1 wt% to 8 wt%.

[0339] B48. The method according to any one of items B1 to B47, wherein the N content of the (N-doped) carbon nanofoam is 1 wt% to 5 wt%.

[0340] B49. The method according to any one of items B1 to B48, wherein the N content of the (N-doped) carbon nanofoam is 2 wt% or greater.

[0341] B50. A method according to any one of items B1 to B49, wherein the surface area of ​​the (N-doped) carbon nanofoam is 400 m 2 / g to 3000m 2 / g.

[0342] B51. A method according to any one of items B1 to B50, wherein the surface area of ​​the (N-doped) carbon nanofoam is 900 m 2 / g to 2000m 2 / g.

[0343] B52. A method according to any one of items B1 to B51, wherein the surface area of ​​the (N-doped) carbon nanofoam is 900 m 2 / g to 1500m 2 / g.

[0344] B53. A (N-doped) carbon nanofoam material, which can be obtained by the method described in any one of items B1 to B52.

[0345] C1. A composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0346] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0347] A coating on the bracket comprises N-doped graphitic carbon.

[0348] C2. The composite material according to item C1, wherein the diameter of the composite particles is 0.005 μm to 25 μm.

[0349] C3. The composite material according to item C1 or C2, wherein the composite particles have a diameter of 0.01 μm to 15 μm.

[0350] C4. The composite material according to any one of items C1 to C3, wherein the diameter of the composite particles is 0.01 μm to 2 μm.

[0351] C5. The composite material according to any one of items C1 to C4, wherein the diameter of the composite particles is 100 nm or less.

[0352] C6. The composite material according to any one of items C1 to C5, wherein the diameter of the composite particles is 10 nm to 30 nm.

[0353] C7. The composite material according to any one of items C1 to C6, wherein the composite particles are aggregated into clusters of 1 μm to 10 μm.

[0354] C8. The composite material according to any one of items C1 to C7, wherein the composite particles are aggregated into clusters of 2 μm to 8 μm.

[0355] C9. The composite material according to any one of items C1 to C8, wherein the composite particles are aggregated into clusters of 3 μm to 6 μm.

[0356] C10. The composite material according to any one of C1 to C9, wherein the (N-doped) carbon nanofoam particles are mesoporous.

[0357] C11. The composite material according to any one of C1 to C10, wherein the (N-doped) carbon nanofoam particles are N-doped.

[0358] C12. The composite material according to any one of items C1 to C11, wherein the N-doped graphitic carbon coating is formed by treating (N-doped) carbon nanofoam with a structural protein to coat the nanofoam with N-doped graphitic carbon.

[0359] C13. A composite material according to any one of C1 to C12, wherein the material has N-doped graphitic regions located in the open pores of the agglomerated (N-doped) carbon nanofoam particle scaffold.

[0360] C14. The composite material according to any one of C1 to C13, wherein the N-doped graphitic carbon is covalently bonded to the (N-doped) carbon nanofoam scaffold.

[0361] C15. The composite material according to any one of items C1 to C14, wherein the N content of the material is from 0.1 wt% to 8 wt%.

[0362] C16. The composite material according to any one of C1 to C15, wherein the N content of the material is 1 wt% to 5 wt%.

[0363] C17. The composite material according to any one of items C1 to C16, wherein the N content of the material is 2 wt% or greater.

[0364] D1. A method for preparing a composite material by heating a (N-doped) carbon nanofoam material (preferably, a (N-doped) carbon nanofoam material according to any one of items A1 to A18) together with a structural protein in an oxygen-reduced environment.

[0365] D2. A method of forming the composite material, the method comprising:

[0366] a. forming a mixture of sugar, water and hydrocarbon mediator;

[0367] b. heating the mixture to form a carbon nanofoam material;

[0368] c. optionally heating the carbon nanofoam in the presence of an acidic nitrogen source (such as nitric acid) to form N-doped carbon nanofoam;

[0369] d. optionally crushing the (N-doped) carbon nanofoam material;

[0370] e. heating the (N-doped) carbon nanofoam material together with the structural protein in an oxygen-reduced environment to form a composite material;

[0371] f. optionally treating the composite material with a pitting agent to form an activated composite material; and

[0372] g. Optionally comminuting the material.

[0373] D3. The method according to item D2, wherein steps (e) to (g) can be repeated as needed until the desired amount of N-doped graphite regions is obtained.

[0374] D4. The method according to item D2 or item D3, wherein steps (a), (b) and (c) are the same as steps (i), (ii) and (iii) of any one of items B1 to B51.

[0375] D5. The method according to any one of items D2 to D4, wherein the comminution steps (d) and / or (f) are performed by grinding.

[0376] D6. The method according to any one of items D2 to D5, wherein step (e) forms N-doped graphitic carbon covalently bonded to the (N-doped) carbon nanofoam.

[0377] D7. The method of any one of items D1 to D6, wherein the oxygen-reduced environment is achieved by using an inert atmosphere (such as argon).

[0378] D8. The method of any one of items D1 to D7, wherein the reduced oxygen environment is achieved by using a vacuum.

[0379] D9. The method according to any one of items D1 to D8, wherein the step heats the (N-doped) carbon nanofoam material to a temperature of at least 400° C. for at least 10 minutes.

[0380] D10. The method according to any one of items D1 to D9, wherein the (N-doped) carbon nanofoam material is heated to a temperature of at least 450° C. to 900° C. for 10 minutes to 3 hours.

[0381] D11. The method according to any one of items D1 to D10, wherein the (N-doped) carbon nanofoam material is heated to a temperature of at least 500° C. to 600° C. for 30 minutes to 90 minutes.

[0382] D12. The method according to any one of items D9 to D11, wherein the produced material contains N-doped graphitic carbon.

[0383] D13. The method according to any one of items D1 to D12, wherein the structural protein is dried and in a form that allows intimate mixing with the carbon particles.

[0384] D14. The method according to item D13, wherein the structural protein is in powdered form.

[0385] D15. The method according to any one of items D1 to D14, wherein the structural protein is collagen.

[0386] D16. The method according to item D15, wherein the source of collagen is gelatin.

[0387] D17. The method according to any one of items D1 to D14, wherein the structural protein is keratin.

[0388] D18. The method according to item D17, wherein the source of keratin is from hair.

[0389] D19. The method according to item D17, wherein the source of keratin is from nails.

[0390] D20. The method according to item D17, wherein the source of keratin is from feathers.

[0391] D21. The method according to item D17, wherein the source of keratin is from horn.

[0392] D22. The method according to item D17, wherein the source of keratin is from the claw.

[0393] D23. The method according to item D17, wherein the source of keratin is from whiskers.

[0394] D24. The method according to item D17, wherein the source of keratin is from hoof.

[0395] D25. The method according to item D20, wherein the feather is a poultry feather.

[0396] D26. The method according to item D25, wherein the poultry feathers are feathers of farmed birds.

[0397] D27. The method according to item D25, wherein the poultry feathers are chicken feathers.

[0398] D28. The method according to item D25, wherein the poultry feathers are turkey feathers.

[0399] D29. The method according to item D25, wherein the poultry feathers are duck feathers.

[0400] D30. The method according to item D25, wherein the poultry feathers are goose feathers.

[0401] D31. The method according to item D25, wherein the poultry feathers are down feathers.

[0402] D32. The method according to item D31, wherein the down feathers are goose down feathers.

[0403] D33. The method according to item D31, wherein the down feathers are duck down feathers.

[0404] D34. The method of any one of items D25 to D33, wherein the ratio of avian feather to (N-doped) carbon nanofoam is from 2:1 to 1:4 nanofoam to feather weight ratio.

[0405] D35. The method of any one of items D25 to D33, wherein the ratio of avian feather to (N-doped) carbon nanofoam is from 3:2 to 1:3 nanofoam to feather weight ratio.

[0406] D36. The method of any one of items D1 to D35, wherein step f. is performed in an oxygen-reduced environment.

[0407] D37. The method according to any one of items D1 to D36, wherein step f. is performed at a temperature of at least 600° C. for at least 10 minutes.

[0408] D38. The method according to item D37, wherein step f. is carried out at 650-1000°C for 10 minutes to 3 hours.

[0409] D39. The method according to item D37 or D38, wherein step f. is carried out at 750-850°C for 1 hour.

[0410] D40. The method of any one of items D1 to D39, wherein the weight ratio of composite material:pitting agent is 1:1.5 or higher.

[0411] D41. The method of any one of items D1 to D40, wherein the weight ratio of composite material:pitting agent is 1:2 to 1:10, eg, 1:2.5 to 1:8 or 1:3 to 1:5.

[0412] D42. The method of any one of items D1 to D40, wherein the weight ratio of composite material:pitting agent is 1:3.

[0413] D43. The method according to any one of items D1 to D42, wherein the pitting agent is potassium carbonate (K2CO3).

[0414] D44. A composite material obtainable by the method according to any one of items D1 to D43.

[0415] E1. A fuel storage material comprising:

[0416] (i) a proton-conducting polymer material; and

[0417] (ii) a composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0418] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0419] A coating on the bracket comprises N-doped graphitic carbon.

[0420] E2. The fuel storage material according to item E1, wherein the composite material is as described in any one of items C1 to C17 or D44.

[0421] E3. The fuel storage material according to item E1 or E2, wherein the proton-conducting polymer material is capable of conducting protons at room temperature (ie, at 25°C).

[0422] E4. The fuel storage material according to any one of items E1 to E3, wherein the proton-conducting polymer material is an acid-doped hydrogel.

[0423] E5. The fuel storage material according to E4, wherein the hydrogel is doped with phosphoric acid.

[0424] E6. The fuel storage material according to E4, wherein the hydrogel is doped with sulfuric acid.

[0425] E7. The fuel storage material according to any one of items E4 to E6, wherein the acid dopant in the hydrogel accounts for 5-25 wt%.

[0426] E8. The fuel storage material according to any one of items E4 to E7, wherein the acid dopant in the hydrogel accounts for 10-20 wt%.

[0427] E9. The fuel storage material according to any one of items E4 to E8, wherein the hydrogel is polyvinyl alcohol.

[0428] E10. The fuel storage material according to any one of items E4 to E8, wherein the hydrogel is a poly(meth)acrylate.

[0429] E11. The fuel storage material according to any one of items E4 to E8, wherein the hydrogel is collagen.

[0430] E12. The fuel storage material according to any one of items E4 to E8, wherein the hydrogel is gelatin.

[0431] E13. The fuel storage material according to any one of items E4 to E8, wherein the hydrogel is fibrin.

[0432] E14. The fuel storage material according to any one of items E4 to E13, wherein the fuel storage material contains less than 15 wt% of acid-doped hydrogel.

[0433] E15. The fuel storage material according to any one of items E4 to E14, wherein the fuel storage material typically contains 4-12 wt% of the acid-doped hydrogel.

[0434] E16. The fuel storage material according to any one of items E4 to E15, wherein the fuel storage material typically contains 5-10 wt% of the acid-doped hydrogel.

[0435] E17. The fuel storage material according to any one of items E1 to E3, wherein the polymer material is a fluorinated acid polymer.

[0436] E18. The fuel storage material according to item E17, wherein the acidic group is directly attached to a side chain on the polymer backbone.

[0437] E19. The fuel storage material according to item E17 or E18, wherein the acidic group is selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a sulfonimide group, a phosphoric acid group, a phosphonic acid group, and combinations thereof.

[0438] E20. The fuel storage material according to any one of items E17 to E19, wherein the acidic group is selected from the group consisting of a sulfonic acid group, a sulfonimide group, and a combination thereof.

[0439] E21. The fuel storage material according to any one of items E17 to E20, wherein at least about 50% of the total number of halogen atoms and hydrogen atoms in the polymer are fluorine atoms.

[0440] E22. The fuel storage material according to any one of items E17 to E21, wherein at least about 75% of the total number of halogen atoms and hydrogen atoms in the polymer are fluorine atoms.

[0441] E23. The fuel storage material according to any one of items E17 to E22, wherein at least about 90% of the total number of halogen atoms and hydrogen atoms in the polymer are fluorine atoms.

[0442] E24. The fuel storage material according to any one of items E17 to E23, wherein the fluorinated acid polymer is perfluorinated.

[0443] E25. The fuel storage material according to any one of items E17 to E24, wherein the polymer backbone is selected from polyolefins, polyacrylates, polymethacrylates, polyimides, polyamides, polyaramids, polyacrylamides, polyacrylamides, polystyrenes, and copolymers thereof.

[0444] E26. The fuel storage material according to any one of items E17 to E25, wherein the acidic group is a sulfonic acid group.

[0445] E27. The fuel storage material according to any one of items E17 to E25, wherein the acidic group is a sulfonimide group.

[0446] E28. The fuel storage material according to item E27, wherein the sulfonimide group has the formula:

[0447] -SO2-NH-SO2-R

[0448] wherein R is an alkyl group.

[0449] E29. The fuel storage material according to item E17, wherein the acidic group is located on a fluorinated side chain.

[0450] E30. The fuel storage material according to item E29, wherein the fluorinated side chain is selected from the group consisting of an alkyl group, an alkoxy group, an amino group, an ether group, and combinations thereof.

[0451] E31. The fuel storage material according to any one of items E17 to E30, wherein the fluorinated acid polymer has a highly fluorinated olefin backbone with pendant highly fluorinated alkyl sulfonate, highly fluorinated ether sulfonate, highly fluorinated ester sulfonate, or highly fluorinated ether sulfonimide groups.

[0452] E32. The fuel storage material according to any one of items E17 to E31, wherein the fluorinated acid polymer is a perfluoroolefin having perfluoroether-sulfonic acid side chains.

[0453] E33. The fuel storage material according to item E17, wherein the polymer is a copolymer of 1,1-difluoroethylene and 2-(1,1-difluoro-2-(trifluoromethyl)allyloxy)-1,1,2,2-tetrafluoroethanesulfonic acid.

[0454] E34. The fuel storage material according to item E17, wherein the polymer is a copolymer of ethylene and 2-(2-(1,2,2-trifluoroethyleneoxy)-1,1,2,3,3,3-hexafluoropropoxy)-1,1,2,2-tetrafluoroethanesulfonic acid.

[0455] E35. The fuel storage material according to item E17, wherein the polymer is a homopolymer or copolymer of a fluorinated and partially sulfonated poly(arylene ether sulfone).

[0456] E36. The fuel storage material according to item E17, wherein the fluorinated acid polymer is a sulfonimide polymer having formula VII:

[0457]

[0458] in:

[0459] R f is selected from highly fluorinated alkylene, highly fluorinated heteroalkylene, highly fluorinated arylene, and highly fluorinated heteroarylene groups which may be substituted with one or more ether oxygens; and

[0460] n is at least 4.

[0461] E37. The fuel storage material according to E36, wherein n is greater than 10.

[0462] E38. The fuel storage material according to item E17, wherein the fluorinated acid polymer has the formula XI:

[0463]

[0464] in

[0465] Each c is independently 0 or an integer from 1 to 3;

[0466] n is at least 4; and

[0467] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0468] E39. The fuel storage material according to item E17, wherein the fluorinated acid polymer further comprises repeating units derived from at least one highly fluorinated ethylenically unsaturated compound.

[0469] E40. The fuel storage material according to E17, wherein the fluorinated acid polymer comprises a highly fluorinated carbon backbone and side chains represented by the following formula:

[0470] -(O-CF2CFR f 3 ) a -O-CF2CFR f 4 SO3E 5

[0471] in

[0472] Rf 3 and R f 4 independently selected from F, Cl or a highly fluorinated alkyl group having 1 to 10 carbon atoms,

[0473] a = 0, 1, or 2, and

[0474] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0475] E41. The fuel storage material according to item E17, wherein the fluorinated acid polymer comprises a perfluorocarbon backbone and a side chain represented by the formula

[0476] -O-CF2CF(CF3)-O-CF2CF2SO3E 5

[0477] in

[0478] E 5 is selected from hydrogen or a cation such as Li, Na or K.

[0479] E42. The fuel storage material according to any one of items E17 to E41, wherein the material contains less than 5 wt% of a fluorinated acid polymer.

[0480] E43. The fuel storage material according to any one of items E17 to E42, wherein the material contains 0.1 wt% to 5 wt% of the fluorinated acid polymer.

[0481] E44. The fuel storage material according to any one of items E17 to E43, wherein the material contains 0.3 wt% to 4 wt% of the fluorinated acid polymer.

[0482] E45. The fuel storage material according to any one of items E17 to E44, wherein the material contains 0.5 wt% to 3 wt% of the fluorinated acid polymer.

[0483] E46. The fuel storage material according to any one of items E1 to E45, wherein the material further comprises an Arrhenius acid.

[0484] E47. The fuel storage material according to item E46, wherein the Arrhenius acid is sulfuric acid, phosphoric acid or nitric acid.

[0485] E48. The fuel storage material according to item E46, wherein when the proton-conducting material is a hydrogel, the Arrhenius acid is phosphoric acid.

[0486] E49. The fuel storage material according to item E47, wherein when the proton-conducting material is a fluorinated polymeric sulfonic acid-based material, the Arrhenius acid is sulfuric acid.

[0487] E50. The fuel storage material according to any one of items E1 to E49, wherein the fuel storage material is capable of storing hydrogen at a level exceeding 1 wt%.

[0488] E51. A fuel storage material according to any one of items E1 to E50, wherein the fuel storage material is capable of storing hydrogen at a level exceeding 2 wt %.

[0489] F1. A method for preparing a fuel storage material, the method comprising:

[0490] (i) forming a paste comprised of a composite material comprising a composite particle superstructure, a proton conducting polymeric material, and a dispersant, wherein the superstructure comprises:

[0491] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0492] a coating on the stent, the coating comprising N-doped graphitic carbon;

[0493] (ii) compressing the paste into a compacted form; and

[0494] (iii) drying the compacted form.

[0495] F2. The method according to F1, wherein the paste is formed using water as the dispersant.

[0496] F3. The method according to item F1 or F2, wherein the polymer material is an acid-doped hydrogel.

[0497] F4. The method according to F3, wherein step (i) comprises:

[0498] (a) forming a mixture of a hydrogel-forming polymer, an acid dopant, and a composite material;

[0499] (b) lyophilizing the mixture; and

[0500] (c) adding water to form a paste composed of the freeze-dried conductive polymer material and the composite material.

[0501] F5. A method according to any one of items F1 to F4, wherein step (iii) comprises heating the compacted form at a temperature high enough to promote removal of the dispersant but low enough not to damage the proton-conducting polymer material.

[0502] F6. The method according to any one of items F1 to F5, wherein the proton-conducting material is a fluorinated acid polymer.

[0503] F7. The method according to item F6, wherein step (iii) comprises heating the compacted form at a temperature of 50°C to 250°C.

[0504] F8. The method according to item F7, wherein step (iii) comprises heating the compacted form at a temperature of 100°C to 200°C.

[0505] F9. A method according to F7 or F8, wherein the heating is performed in a flowing gas stream to facilitate removal of the dispersant.

[0506] F10. The method according to any one of items F1 to F5, wherein the proton-conducting material is an acid-doped hydrogel.

[0507] F11. The method according to F10, wherein step (iii) comprises heating the compacted form at a temperature not higher than 75°C.

[0508] F12. The method according to any one of items F1 to F11, wherein after step (iii), the material may be degassed.

[0509] F13. The method according to any one of items F1 to F12, wherein after step (iii), the material can be degassed in a vacuum furnace.

[0510] F14. The method according to any one of items F1 to F13, wherein the composite material is as described in any one of items C1 to C17 or D44.

[0511] F15. The method according to item F1, wherein the fuel storage material formed complies with any one of items E1 to E51.

[0512] F16. A fuel storage material obtainable by the method according to any one of items F1 to F15.

[0513] G1. A fuel cell unit comprising the fuel storage material according to any one of items E1 to E51 or F16.

[0514] G2. The fuel cell unit of G1, wherein the fuel storage material is part of or adjacent to an electrode to at least partially provide the fuel to the electrode when operating in a redox mode.

[0515] G3. A fuel cell unit (100), comprising:

[0516] a polymer electrolyte membrane (101) having a first electrode (102) on one side and a second electrode (103) on an opposite side, wherein the polymer electrolyte membrane (101), the first electrode (102) and the second electrode (103) are arranged between a first plate (104) and a second plate (105);

[0517] wherein the first plate (104) is arranged adjacent to the first electrode (102), and the second plate (105) is arranged adjacent to the second electrode (105), wherein the first plate optionally at least partially defines a flow channel facing the first electrode (102) and is configured to provide fluid to the first electrode (102) and receive fluid from the first electrode;

[0518] one or more first catalyst layers, the one or more first catalyst layers being located between the first plate (104) and the polymer electrolyte membrane (101);

[0519] one or more second catalyst layers, the one or more second catalyst layers being located between the second plate (105) and the polymer electrolyte membrane (101);

[0520] wherein the fuel cell unit is configured to operate in a redox mode and a regeneration mode, wherein

[0521] In the redox mode, the fuel cell unit is configured to be supplied with fuel to the second electrode (103) and with oxidant to the first electrode (102) to generate current between the first electrode and the second electrode and produce reaction products; and

[0522] In the regeneration mode, the fuel cell unit is configured to be supplied with the reaction product to the first electrode (102) and a potential difference between the first electrode and the second electrode, thereby producing the fuel at the second electrode (103);

[0523] And among them

[0524] The fuel cell unit comprises a fuel storage material as part of or adjacent to the second electrode (103) to at least partially provide the fuel to the second electrode (103) in the redox mode and / or to store the fuel in the regeneration mode,

[0525] The fuel storage material comprises

[0526] A composite material and a proton conducting polymer material, the composite material comprising a composite particle superstructure, wherein the superstructure comprises:

[0527] Agglomerated (N-doped) carbon nanofoam particle scaffolds; and

[0528] A coating on the bracket comprises N-doped graphitic carbon.

[0529] G4. The fuel cell unit of G1 to G3, wherein the proton-conducting polymer material is a fluorinated acid polymer.

[0530] G5. The fuel cell unit of G4, wherein the material contains 0.1 wt% to 5 wt% of a fluorinated acid polymer.

[0531] G6. The fuel cell unit of G1 to G3, wherein the proton-conducting polymer material is an acid-doped hydrogel.

[0532] G7. A fuel cell unit according to G6, wherein the fuel storage material typically contains 4-12 wt% of the acid-doped hydrogel.

[0533] G8. The fuel cell unit of any one of G1 to G7, wherein the material further comprises an Arrhenius acid.

[0534] G9. The fuel cell unit according to any one of G1 to G8, further comprising one or more gas diffusion layers, the one or more gas diffusion layers being configured to respectively facilitate one or more of the following:

[0535] Diffusion of fuel to and / or from the flow channels of the second plate;

[0536] Diffusion of oxygen (e.g., air) into and / or from the flow channels of the first plate;

[0537] diffusion of fuel or its derivatives to and / or from the membrane; and

[0538] The fuel or its derivatives diffuse to and / or from the membrane.

[0539] G10. The fuel cell unit of G9, wherein the gas diffusion layer has a hydrophobic coating.

[0540] G11. The fuel cell unit of any one of G1 to G10, wherein the first electrode comprises carbon cloth.

[0541] G12. The fuel cell unit of any one of G1 to G11, wherein the first electrode comprises carbon paper.

[0542] G13. The fuel cell unit of any one of G1 to G12, wherein the first electrode comprises a metal frit.

[0543] G14. A fuel cell unit according to G9, wherein the gas diffusion layer comprises a porous structure of fibers or open-cell foam.

[0544] G15. The fuel cell unit of any one of G1 to G14, wherein the first plate and the second plate are configured to at least partially confine the fuel, the oxygen, and the reaction products within the fuel cell unit, and without one or more of the following:

[0545] comprising a rigid element for providing structural support for the first electrode, the membrane, and the second electrode;

[0546] comprising a conductive element for electrically coupling to the first electrode and the second electrode and to a circuit for transporting electrons between the electrodes;

[0547] A structure is included that forms a first flow channel and a second flow channel.

[0548] G16. A fuel cell unit according to G1 to G15, wherein the fuel cell unit comprises a first electrode and a second electrode separated by a polymer electrolyte membrane, and wherein the fuel storage material is arranged adjacent to or as part of the second electrode.

[0549] G17. A fuel cell unit stack comprising a plurality of fuel cell units arranged in series, wherein the plurality of fuel cell units comprises at least one fuel cell unit according to any one of G1 to G16.

[0550] G18. The fuel cell stack of item G17, wherein the fuel cell stack does not include any cooling elements.

[0551] G19. The fuel cell unit according to G1 to G18, wherein the catalyst on the one or more first catalyst layers catalyzes an OER reaction and / or an ORR reaction.

[0552] G20. A fuel cell unit according to any one of items G1 to G19, wherein the second plate includes a flow channel formed in a surface of the second plate facing the second electrode and configured to provide fluid to the second electrode and receive fluid from the second electrode.

[0553] G21. A fuel cell unit according to any one of claims G1 to G20, wherein the fuel cell unit comprises a gas diffusion layer, the gas diffusion layer being located between the polymer electrolyte membrane (101) and the second electrode (103).

[0554] G22. The fuel cell unit of item G21, wherein the gas diffusion layer has a hydrophobic coating.

[0555] G23. A fuel cell unit according to G21 or G22, wherein the gas diffusion layer comprises a porous structure of fibers or open-cell foam.

[0556] G24. The fuel cell unit of any one of G1 to G23, wherein the fuel cell unit is configured to receive hydrogen as the fuel through the flow channels of the second plate.

[0557] G25. A fuel cell unit according to any one of G1 to G24, wherein the fuel cell unit comprises a hydrogen fuel cell unit, wherein the fuel comprises hydrogen, the oxidant comprises air, and the reaction product comprises water.

[0558] G26. A fuel cell unit according to any one of G1 to G25, wherein the first electrode comprises a woven layer of conductive fibers.

[0559] G27. A fuel cell unit according to G26, wherein the fibers of the textile layer comprise metal.

[0560] G28. A fuel cell unit according to items G26 to G27, wherein the textile layer comprises a non-platinum group metal.

[0561] G29. A fuel cell unit according to G28, wherein the textile layer comprises a non-woven fabric.

[0562] G30. The fuel cell unit of any one of G1 to G29, wherein the first plate and the second plate are configured to at least partially confine the fuel, the oxygen, and the reaction products within the fuel cell unit, and without one or more of the following:

[0563] comprising a rigid element for providing structural support for the first electrode, the membrane, and the second electrode;

[0564] comprising a conductive element for electrically coupling to the first electrode and the second electrode and to a circuit for transporting electrons between the electrodes;

[0565] A structure is included that forms a first flow channel and a second flow channel.

[0566] G31. A fuel cell unit according to any one of items G1 to G30, wherein the fuel cell unit includes a peripheral gasket, which is configured to be sandwiched between the first plate and the second plate and at least restrain the polymer electrolyte membrane, the first electrode, the second electrode, the one or more first catalyst layers and the one or more second catalyst layers.

[0567] G32. A fuel cell unit stack comprising a plurality of fuel cell units arranged in series, wherein the plurality of fuel cell units comprises at least one fuel cell unit according to any one of items G1 to G31.

[0568] H1. Use of the fuel storage material according to items E1 to E51 or F16 in a fuel cell unit.

[0569] H2. Use of the fuel storage material according to items E1 to E51 or F16 for storing hydrogen.

[0570] H3. The use according to item H2, wherein the hydrogen is in the form of hydronium ions.

[0571] H4. The use according to item H3, wherein the hydrogen is stored by chemical adsorption.

[0572] H5. The use according to item H2, wherein the hydrogen is in the form of liquefied hydrogen.

[0573] H6. The use according to item H5, wherein the hydrogen is stored by physical adsorption.

[0574] H7. The use according to item H2, wherein the hydrogen is in the form of hydronium ions and liquefied hydrogen.

[0575] H8. The use according to item H7, wherein the hydrogen is stored by physical adsorption and chemical adsorption.

[0576] Example 1 - Preparation of N-doped carbon nanofoam

[0577] Dissolve 171g of granulated sugar in 100ml of deionized (DI) water. Heat and stir the mixture to dissolve the sugar until it is completely dissolved. The final temperature is approximately 60-80°C when the sugar becomes completely dissolved.

[0578] The mixture was allowed to cool to approximately 45°C and 3 mg of naphthalene was added. The mixture was stirred to dissolve the naphthalene.

[0579] The resulting mixture was added to a Teflon-lined hydrothermal reactor. The reactor was sealed and placed in an oven at 155°C for 5 hours.

[0580] The resulting mixture was allowed to cool before removing the carbonaceous material and washing thoroughly using physical dissolution of the material, decantation, and DI filtration in the order described. The filtrate was dried in an oven at 50°C under vacuum for 6-12 hours.

[0581] The material is then ground in a ball mill using 5mm-10mm steel bearings (other bearings such as alumina or zirconium can also be used) for 24+ hours and then sieved through a 43–63 micron polyamide filter membrane.

[0582] The resulting material was nitrogen doped by treating it with 6M HNO3 at 100°C for 8 hours and then neutralized using a mild sodium bicarbonate solution and rinsing in DI water until a pH of 6.5-7 was reached. The material was then dried at 50°C under vacuum for 6-12 hours.

[0583] Figure 2a and 2b An SEM micrograph of the resulting material is shown in . The material is a scaffold of small particulate material approximately 1-2 μm in diameter that has coagulated to form a foam-like porous material.

[0584] Example 2 - Preparation of carbon nanofoam material (composite material) coated with N-doped graphitic carbon

[0585] Dissolve 171g of granulated sugar in 100ml of deionized (DI) water. Heat and stir the mixture to dissolve the sugar until it is completely dissolved. The final temperature is approximately 60-80°C when the sugar becomes completely dissolved.

[0586] The mixture was allowed to cool to approximately 45°C and 3 mg of naphthalene was added. The mixture was stirred to dissolve the naphthalene.

[0587] The mixture was added to a Teflon-lined hydrothermal reactor. The reactor was sealed and heated in an oven at 69°C for 5 hours.

[0588] The material was nitrogen doped by mixing it with avian feathers (goose down) at a ratio of 50:50 (carbon material to feathers).The mixture was heated at 550°C for 1 hour in an oxygen-reduced environment (under an argon flow).

[0589] After the composite material was formed, a pitting agent (K2CO3) was added to the mixture at a mass ratio of 1:3 composite material to pitting agent. The material was then dried and heated at 800°C for 1 hour in a nitrogen environment.

[0590] After completion, the mixture was cooled and the carbonaceous material was removed. The material was thoroughly washed using physical dissolution of the material, decantation and DI filtration in the order described. The filtrate was dried in a 50°C oven under vacuum for 6-12 hours.

[0591] The material was then ground in a ball mill using 5 mm to 10 mm steel bearings (other bearings such as alumina or zirconium can also be used) for 12 hours and then sieved through a 43–63 μm polyamide filter membrane.

[0592] Washing and grinding may optionally be repeated to provide the final product.

[0593] Figure 3a and 3b TEM micrographs of the resulting material are shown in FIG. The material is a superstructure composed of small particles of material with a diameter of about 10-30 nm, which aggregate to form clusters of about 4-5 μm, as shown in FIG. Figure 3a and 3b middle.

[0594] To disperse the aggregates and image the individual particles, an ionic solvent, such as isopropanol, is added to the sample.

[0595] Example 3 - Fuel Storage Materials

[0596] 20 ml of DI water was added to 100 g of the composite material from Example 2. 1 wt% of 60% EtOH was added. The 212 solution was added to the carbon nanofoam solution. The materials were paddle mixed to ensure uniform dispersion.

[0597] The solution was pressed into sheets with a thickness of 2–3 mm (depending on the active surface area of ​​the end cell model). The electrode sheets were then exposed to a dehumidified dry air stream at 150°C for a residence time of 2 minutes. Infrared radiant heating was used as the heating mechanism.

[0598] The preheated electrode sheet was then placed into a vacuum oven at 70°C and 101 kPa for 6 hours to degas the material.

[0599] After degassing the material, the sheet was soaked in 1M H2SO4 for 8-12 hours. After the soaking period, the material was dried at ambient temperature for 24 hours to evaporate excess water, but without removing all water content. Proton conductivity requires an estimated minimum water content of 5000 pm.

[0600] The material is then cut into the desired shape.

[0601] Example 4 - Estimating Storage Potential

[0602] The hydrogen storage potential of N-doped carbon nanofoam and N-doped graphitic carbon (composite) was estimated based on the discharge time of fuel cell cells containing the composite in the fuel storage electrode. The results were compared with other known carbon nanofoam materials.

[0603] Table 1. Details of fuel storage materials AE

[0604]

[0605]

[0606] To form electrodes, each material is mixed with The amount of fuel storage material in each test cell was standardized to 1 g.

[0607] ●Test battery cell size: 3cm x 3cm

[0608] Active surface area: 9cm 2

[0609] Catalyst: Pt-C, 20% platinum on carbon (available from fuelcellstore: 20% platinum on Vulcan XC 72, product code: 591278)%

[0610] ●Polymer activator: 1M H2SO4

[0611] PEM: 115

[0612] Fuel: 10mL water

[0613] ●Exact time: 1 minute

[0614] Load: 100mA

[0615] Table 2 shows the discharge time of each carbon nanofoam material. Storage materials D and E showed significantly longer discharge times than those of materials A, B, and C. This indicates that materials D and E have higher hydrogen storage capacities, with material E having the best performance.

[0616] Without wishing to be bound by theory, it is believed that materials D and E have better hydrogen storage capacity due to higher surface area and a certain degree of high N doping. High N doping allows for easy absorption of hydrogen in the form of hydronium ions. For example, hydrogen can be stored in the form of H3O + 、H5O2 + or H9O3 +in the form of a storage medium, where temporary ionic bonds are formed between the ions and the storage material.

[0617] Table 2. Discharge time of fuel storage materials AE

[0618]

[0619]

[0620] Based on the discharge time, samples D and E were estimated to store approximately 1-2% hydrogen.

Claims

1. A fuel cell unit comprising a fuel storage material, wherein the fuel storage material comprises: (i) a proton-conducting polymer material; and (ii) a composite material comprising a composite particle superstructure, wherein the superstructure comprises: agglomerated carbon nanofoam particle scaffolds; and a coating on the stent, the coating comprising N-doped graphitic carbon; The carbon nanofoam particles may be optionally N-doped.

2. The fuel cell unit according to claim 1, wherein the fuel storage material is part of or adjacent to an electrode to at least partially provide the fuel to the electrode when operating in a redox mode.

3. The fuel cell unit according to any one of the preceding claims, wherein the composite material comprises composite particles having a diameter of 0.005 μm to 25 μm.

4. The fuel cell unit according to any one of the preceding claims, wherein the N-doped graphitic carbon is covalently bonded to the (N-doped) carbon nanofoam scaffold. 5 . The fuel cell unit according to claim 1 , wherein the (N-doped) carbon nanofoam particles are N-doped carbon nanofoam particles.

6. The fuel cell unit according to any one of the preceding claims, wherein the N content of the composite material is 1 wt% to 5 wt%.

7. The fuel cell unit according to any one of the preceding claims, the tortuous path of the open pores of the agglomerated (N-doped) carbon nanofoam particle scaffold being at least 3 times the average diameter of the nanofoam particles.

8. The fuel cell unit of claim 7, wherein the composite material has N-doped graphite regions located within the open pores of the agglomerated (N-doped) carbon nanofoam particle scaffold.

9. A fuel cell unit according to any one of the preceding claims, wherein the surface area of ​​the composite material is 900 m 2 / g to 2000m 2 / g.

10. A fuel cell unit according to any preceding claim, wherein the proton-conducting polymer material is an acid-doped hydrogel.

11. The fuel cell unit according to any one of claims 1 to 9, wherein the polymer material is a fluorinated acid polymer. 12 . A fuel cell unit stack comprising a plurality of fuel cell units arranged in series, the plurality of fuel cell units comprising at least one fuel cell unit according to claim 1 .

13. A method for preparing the composite material used in any one of claims 1 to 11, the method comprising the steps of: a. forming a mixture of sugar, water and hydrocarbon mediator; b. heating the mixture to form a carbon nanofoam material; c. optionally heating the carbon nanofoam in the presence of an acidic nitrogen source (such as nitric acid) to form N-doped carbon nanofoam; d. optionally crushing the (N-doped) carbon nanofoam material; e. heating the (N-doped) carbon nanofoam material together with the structural protein in an oxygen-reduced environment to form a composite material; f. optionally treating the composite material with a pitting agent to form an activated composite material; and g. Optionally comminuting the material.

14. The method according to claim 13, wherein the structural protein is collagen, gelatin or keratin, preferably wherein the structural protein is feather, even more preferably wherein the structural protein is avian feather.

15. A composite material comprising a composite particle superstructure, wherein the superstructure comprises: Agglomerated (N-doped) carbon nanofoam particle scaffolds; and A coating on the bracket comprises N-doped graphitic carbon.

16. The composite material of claim 15, wherein the N-doped graphitic carbon is covalently bonded to the (N-doped) carbon nanofoam scaffold.

17. The composite material according to claim 15 or claim 16, wherein the (N-doped) carbon nanofoam particles are N-doped.

18. The composite material according to any one of claims 15 to 17, wherein the N content of the material is 2 wt% or more.

19. A fuel storage material comprising: (i) a proton-conducting polymer material; and (ii) The composite material according to any one of claims 15 to 18.

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