Graphene-based precursor structures

Abstract

A method for improving the catalytic accessibility of carbon precursors is provided to inhibit degradation of components such as catalysts and membranes. [Solution] A method for improving catalytic accessibility of a carbon precursor includes exposing a graphene-based multilayer precursor structure to a plurality of electrocatalyst clusters by applying a voltage, accelerating the clusters toward the graphene-based multilayer precursor structure, and producing mechanical defects at the surface of the graphene-based multilayer precursor structure and a substantially uniform size population of deposited electrocatalysts at a substantially uniform depth within the graphene-based multilayer precursor structure, respectively.

Description

[Technical Field]

[0001] The present disclosure relates to graphite-based precursor structures for the fabrication of catalyst support components, such as for fuel cells, and methods for their modification to alter one or more properties.

[0002] background Hydrogen technologies, such as fuel cells and electrolyzers, have become increasingly popular in recent years due to their ability to convert chemical energy into electricity and vice versa using water and hydrogen as a medium. However, many challenges remain, hindering their large-scale production. The harsh environments of fuel cells and electrolyzers not only pose challenges for material selection, but also require solutions to the degradation of components such as catalysts and membranes, which impacts the efficiency of hydrogen devices. Similarly, functional reliability and fabrication economics need to be improved.

[0003] overview In one embodiment, a method for improving catalytic accessibility of a carbon precursor is disclosed. The method may include exposing a graphene-based multilayer precursor structure to a plurality of electrocatalyst clusters by applying a voltage and accelerating the clusters toward the graphene-based multilayer precursor structure, thereby producing mechanical defects at the surface of the graphene-based multilayer precursor structure and a substantially uniform size population of deposited electrocatalysts at a substantially uniform depth within the graphene-based multilayer precursor structure. The electrocatalyst clusters may be monodisperse, produced by an isoenergetic beam. The electrocatalyst clusters may be monodisperse, produced by an isovelocity beam. The electrocatalyst clusters may be polydisperse, produced by an isoenergetic beam. The method may also include selecting a plurality of electrocatalysts based on a target cluster size of less than 100 atoms. The method may also include selecting a plurality of electrocatalysts based on a target cluster diameter of about 2-5 nm. The voltage may be in the range of about 1-10 MV and several tens of keV / atom to several tens of MeV / atom. The mechanical defects may include exposed lattice portions, which result in increased porosity of the graphene-based multilayer precursor structure.

[0004] In another embodiment, a method for improving catalytic accessibility of a carbon precursor is disclosed. The method may include repeatedly bombarding a graphene-based multilayer precursor structure with a population of electrocatalyst clusters selected based on at least one predetermined value to deposit electrocatalyst clusters within the structure while gradually increasing the porosity of the structure, wherein the repeated bombardment includes application of a constant ionization energy. The at least one predetermined value may include a target cluster size of less than 100 atoms. The at least one predetermined value may include a target cluster diameter of about 2-5 nm. The constant ionization energy may include an energy constant per atom. The constant ionization energy may include an energy constant regardless of cluster size. The electrocatalyst clusters may be monodisperse clusters.

[0005] In an alternative embodiment, a method for depositing an electrocatalyst on a carbon precursor is disclosed. The method may include providing clusters of electrocatalyst particles based on cluster size uniformity. The method may further include accelerating the clusters of electrocatalyst particles toward a graphene-based multilayer precursor structure by applying a voltage field ranging from about 1 to 10 MV and from several tens of keV / atom to several tens of MeV / atom. The method may also include impacting the accelerated clusters of electrocatalyst particles on the graphene-based multilayer precursor structure to deposit the clusters of electrocatalyst particles based on a depth deposition criterion. The cluster size uniformity may include substantially uniformly sized clusters having a deviation of about ±1 to 5% from the average cluster size. The depth deposition criterion may include a substantially uniform size population of deposited catalyst at a substantially uniform depth within the carbon structure. The depth deposition criterion may include a heterogeneous size population of deposited catalyst at a plurality of non-uniform depths. The clusters may be monodisperse. The method may also include increasing the number of mechanical defects in the carbon precursor. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram illustrating a non-limiting example proton exchange membrane fuel cell. [Figure 2A] FIG. 1 illustrates a non-limiting example of a complex graphitic structure according to one embodiment disclosed herein. [Figure 2B] FIG. 1 illustrates a non-limiting example of a complex graphitic structure according to one embodiment disclosed herein. [Figure 2C] FIG. 1 illustrates a non-limiting example of a complex graphitic structure according to one embodiment disclosed herein.

[0007] Detailed Description Embodiments of the present disclosure are described below. However, it should be understood that the disclosed embodiments are merely exemplary and that other embodiments may take various alternative forms. The drawings are not necessarily to scale, and some features may be exaggerated or reduced in size to show details of particular components. Therefore, specific structural or functional details disclosed herein should not be interpreted as limiting, but merely as representative references to teach those skilled in the art how to employ the present embodiments in various forms. As those skilled in the art will understand, various features illustrated and described with reference to any one figure can be combined with features illustrated in one or more other figures to provide embodiments not explicitly shown or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of this disclosure may be desirable depending on the particular application or implementation.

[0008] Except in the examples or where expressly stated otherwise, all numerical amounts herein indicating amounts of materials or conditions of reaction and / or use are understood to be modified by the word "about" in describing the broadest scope of the disclosure. Practice within the stated numerical limits is generally preferred. Also, unless expressly stated to the contrary, "percent," "parts," and "ratio" values ​​are by weight; in the context of this disclosure, the description of a group or class of materials as suitable or preferred for a given purpose implies that mixtures of any two or more members of that group or class are similarly suitable or preferred; the description of components in chemical terms refers to the components at the time of addition to any combination specified herein and does not necessarily exclude chemical interactions between the components of the mixture after mixing. Unless otherwise specified, weight percent is based on the total weight of the substrate, and volume percent is based on the total volume of the substrate.

[0009] The initial definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and applies mutatis mutandis to normal grammatical variations of the originally defined abbreviation. Unless expressly stated to the contrary, measurements of a property are ascertained by the same technique as previously or subsequently referenced for the same property.

[0010] It should also be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, when an element is referred to in the singular, it is intended to include plural elements.

[0011] As used herein, the terms "substantially," "generally," or "about" mean that the subject amount or value may be the specified value or some other value nearby. Generally, the term "about" used when referring to a certain value is intended to indicate a range of ±5% of that value. As an example, the expression "about 100" indicates 100 ± 5, i.e., a range of 95 to 105. Generally, when the term "about" is used, similar results or effects according to the present disclosure can be expected to be obtained within ±5% of the specified value. The term "substantially" may refer to a value or relative property disclosed or claimed in the present disclosure. In such cases, "substantially" may indicate that the value or relative property it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10%.

[0012] It should also be noted that integer ranges explicitly include all intermediate integers. For example, the integer range 1 to 10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, the range 1 to 100 includes 1, 2, 3, 4, ..., 97, 98, 99, and 100. Similarly, when any range is sought, intermediate numbers that are increments of 10 that represent the difference between the upper and lower limits can be employed as alternative upper or lower limits. For example, if the range is 1.1 to 2.1, the numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as the lower or upper limit. Similarly, it should be noted that whenever a list of integers is provided herein, this list of integers also explicitly includes the range of any two integers in the list.

[0013] In the examples provided herein, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be practiced within ±50% of the values ​​rounded or truncated to two significant digits provided in the examples. In a refinement, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be practiced within ±30% of the values ​​rounded or truncated to two significant digits provided in the examples. In another refinement, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be practiced within ±10% of the values ​​rounded or truncated to two significant digits provided in the examples.

[0014] As used herein, the term "and / or" means that either all or only one of the elements of the aforementioned group may be present. For example, "A and / or B" means "only A, or only B, or both A and B." In the case of "only A," the term also encompasses the possibility that B is not present, i.e., "only A and no B."

[0015] It is also to be understood that this disclosure is not limited to the specific embodiments and methods described below, as specific components and / or conditions may, of course, vary. Further, the terminology used herein is used only for the purpose of describing particular embodiments of the disclosure and is not intended to be limiting in any way.

[0016] The term "comprising" is synonymous with "including," "having," "containing," or "characterized by." These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps. The terms "including" or "includes" can encompass the terms "comprise," "consist of," or "essentially consist of."

[0017] The phrase "consisting of" excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause within the body of a claim rather than immediately following the preamble, it limits only the elements specified in that clause; it does not exclude other elements from the claim as a whole.

[0018] The phrase "consisting essentially of" limits the scope of a claim to those materials or steps specified in addition to those that do not materially affect the basic and novel characteristics of the claimed subject matter.

[0019] With respect to "comprising," "consisting of," and "consisting essentially of," when one of these three terms is used herein, the presently disclosed subject matter may include the use of either of the other two terms.

[0020] The term "one or more" means "at least one," and "at least one" means "one or more." The terms "one or more" and "at least one" include "plurality" as a subset.

[0021] The description of a group or class of materials as being suitable for a given purpose, in connection with one or more embodiments, implies that mixtures of any two or more members of that group or class are suitable. The description of a group or class of materials as being suitable for a given purpose, in connection with one or more embodiments, implies that the group or class of materials "comprises," "consists of," and / or "consists essentially of" all or any members of that group or class of materials. The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurements of properties are ascertained by the same method as previously or subsequently referenced for the same property.

[0022] Chemical and electrochemical systems that utilize hydrogen as a fuel source, either in direct hydrogen combustion engines or fuel cells, are considered the energy systems of the future. These hydrogen-generation devices are becoming increasingly popular due to their ability to generate clean energy. These systems may include fuel cells, electrolysis cells, and battery cells. Fuel cells, or electrochemical cells, convert the chemical energy of a fuel (e.g., H2) and an oxidant into electricity through a pair of electrochemical half-reactions (redox reactions). They are an increasingly popular hydrogen fuel generation technology. Fuel cells are currently a promising alternative transportation technology that can operate without emitting either toxins or greenhouse gases. Electrolyzers are electrochemical devices designed to convert electricity and water into hydrogen and oxygen, which can themselves be used for energy storage. Electrolyzers use electrolysis to generate hydrogen. In addition to fuel cells, electrolyzers can be used in other applications, including industrial, residential, and military applications, as well as energy storage-focused technologies such as power grid stabilization and local hydrogen generation from dynamic power sources, including wind turbines and solar cells.

[0023] A non-limiting example of a fuel cell is the proton exchange membrane fuel cell (PEMFC). PEMFCs utilize the electrochemical reaction of H2 and O2 gases to provide practical energy efficiencies of over 60%, with H2O as the only product. The fast diffusion of H ions allows PEMFCs to function at relatively low temperatures of approximately 100°C. In contrast, solid oxide fuel cells and molten carbonate fuel cells operate at temperatures above approximately 600°C.

[0024] A non-limiting example of a fuel cell, a PEMFC, is shown in FIG. 1A. As shown in FIG. 1, the PEMFC 110 includes an anode catalyst support 112 coated with an anode catalyst layer 114 formed from an anode catalyst material, and a cathode catalyst support 16 coated with a cathode catalyst layer 118 formed from a cathode catalyst material. A polymer electrolyte material (PEM) 120 extends between the anode catalyst support 112 and the cathode catalyst support 116. The cathode catalyst material may be dispersed at the interface between the PEM 120 and a current collector (not shown) supported by the cathode catalyst support 118. The current collector may be a porous carbon current collector. The anode catalyst layer 114 is disposed between the anode catalyst support 112 and the PEM 120. The cathode catalyst layer 118 is disposed between the cathode catalyst support 116 and the PEM 120. The anode 122 generally refers to the anode catalyst support 112 and the anode catalyst layer 114. The cathode 124 generally refers to the cathode catalyst support 116, the cathode catalyst layer 118, and a current collector (not shown). The PEMFC 110 also includes first and second gas diffusion layers (GDLs) (not shown). The first GDL is adjacent to an outer surface 126 of the anode catalyst support 112, and the second GDL is adjacent to an outer surface 128 of the cathode catalyst support 116.

[0025] Despite the advantages of PEMFCs, their high manufacturing costs and relatively low durability limit their application in energy plants and more affordable transportation technologies. For example, the platinum (Pt) / carbon (C) electrocatalyst in the PEMFC cathode accounts for at least half of the manufacturing cost of the PEMFC, while the electrochemically active surface area (ECSA) of the Pt catalyst deteriorates significantly (e.g., more than 50%) during cycling.

[0026] Optimizing the microstructure of catalyst supports is a promising step toward improving the durability and reducing the cost of PEMFCs. Various forms of carbon have been investigated and tested for PEMFC applications, including as catalyst support materials. While many types of supports are carbon-based, research has confirmed that differences in carbon structure, morphology, and allotropic forms affect the properties and performance of the support. Therefore, not only the type of carbon but also its manufacturing conditions and variations affect its applicability in specific applications. For example, numerous graphene- and graphite-like structures have been identified, which can vary significantly in their properties, such as electrical conductivity, elasticity, tensile strength, and thermal conductivity.

[0027] Optimizing carbon supports for Pt catalysts is a promising step toward improving the durability of PEMFCs and reducing the cost of other electrochemical devices that utilize carbon-based electrocatalyst supports. This optimization step can consider the correlation between the surface area of ​​the carbon support and the ECSA of the Pt catalyst supported on the carbon support. For example, given the same weight percentage of Pt loading, the larger the surface area of ​​the carbon support, the higher the ECSA of the Pt catalyst supported on the carbon unit. This trend can be attributed to the uniformly small size (e.g., average diameter of approximately 3 nm) and uniform dispersion of Pt nanoparticles on the carbon support with a relatively high surface area. Although Pt / C electrocatalysts using high-surface-area carbon (HSAC) can achieve relatively high ECSA with lower Pt loadings, they still suffer from severe cycling degradation with ECSAs comparable to or similar to those of Pt / C electrocatalysts using low-surface-area carbon (LSAC). One proposal to improve the cycling stability of Pt / C is to replace the oxidizable amorphous carbon with less reactive graphitized carbon.

[0028] One proposal for producing graphitic carbon with relatively high surface area involves the silver templating method. This method synthesizes mesoporous carbon nanodendrite (MCND) structures with hollow, cellular graphitic carbon nanoparticles (HGCN) with surface pores as primary particles. Typical HGCNs have wall thicknesses greater than 5 nm (e.g., greater than 10 graphite layers), while MCND structures may have single-layer graphene walls, resulting in very high surface areas (e.g., 1,610 m). 2 / g).

[0029] However, preparing carbon precursors for producing high-surface-area, low-reactivity graphitized carbon, such as amorphous carbon nanoclusters with diameters less than 2 nm, has proven challenging. The difficulties in graphene production are typically related to the requirement for scalable and defect-free graphene materials. Specifically, utilizing scalable, basic mechanical and chemical methods to produce graphene with a variety of configurations remains a challenge.

[0030] In one or more embodiments, a method for producing a carbon precursor for making a graphitized carbon catalyst support is disclosed. In a non-limiting embodiment, the process, described in detail below, includes utilizing defective graphene flakes, modifying the graphene flakes with additional carbon structures, optionally introducing additional defects, and crumpling the modified graphene flakes into a carbon precursor.

[0031] The resulting carbon precursor may include a wrinkled modified graphene structure. The resulting carbon precursor may include graphitic carbon nanoparticles with a single-layer graphitic structure, such as a shell or wall. The precursor may include a single-layer structure. The precursor may include two-dimensional materials, quasi-two-dimensional materials, or both. The precursor may include graphitic nanoparticles with one or more graphitic materials, such as crystalline forms of carbon atoms formed in hexagonal structures, amorphous carbon structures, nanoclusters or carbon materials with one or more dimensions in the nanoscale range of 1 to 100 nanometers, onion-shaped graphitic carbon mesostructures, hollow irregularly shaped mesostructures, or combinations thereof. The carbon precursor may include crystalline structures, amorphous materials, or combinations thereof. The carbon structures may include complex geometries, such as serpentine geometries, i.e., with multiple twists and turns within an undulating surface topology, resulting in the presence of pockets, cavities, bends, and diverse orientations of the internal and external surfaces.

[0032] The carbon precursor is -9 meters) to micrometers (10 -6 The structures may include nanoscale, mesoscale, microscale structures, or combinations thereof, ranging in size from 100 to 1500 mm (up to 1000 mm). These structures may be irregular, asymmetric, curved, and have one or more bends, undulations, holes, voids, defects, or combinations thereof. These structures may include irregular amounts of pentagons and heptagons throughout the structure or at the structure edges. Non-limiting example structures disclosed herein are shown in Figures 2A, 2B, and 2C.

[0033] The carbon precursor may be about 500-3000, about 800-2500, or about 1000-1400 m 2The very high surface area may be in the range of about 500, about 600, about 700, about 800, about 900, about 1000, about 1100, about 1200, about 1300, about 1400, about 1500, about 1600, about 1700, about 1800, about 1900, about 2000, about 2100, about 2200, about 2300, about 2400, about 2500, about 2600, about 2700, about 2800, about 2900, or about 3000 m / g. 2 / g, or at least about 500, at least about 600, at least about 700, at least about 800, at least about 900, at least about 1000, at least about 1100, at least about 1200, at least about 1300, at least about 1400, at least about 1500, at least about 1600, at least about 1700, at least about 1800, at least about 1900, at least about 2000, at least about 2100, at least about 2200, at least about 2300, at least about 2400, at least about 2500, at least about 2600, at least about 2700, at least about 2800, at least about 2900, or at least about 3000 m 2 / g.

[0034] The carbon precursor is about 0.7 to 3.5, about 0.9 to 3.2, or about 1.2 to 3.0 g / cm 3 The density may be about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, or about 3.0 g / cm. 3, at least about 0.7, at least about 0.8, at least about 0.9, at least about 1.0, at least about 1.1, at least about 1.2, at least about 1.3, at least about 1.4, at least about 1.5, at least about 1.6, at least about 1.7, at least about 1.8, at least about 1.9, at least about 2.0, at least about 2.1, at least about 2.2, at least about 2.3, at least about 2.4, at least about 2.5, at least about 2.6, at least about 2.7, at least about 2.8, at least about 2.9, or at least about 3.0 g / cm 3 , or at most about 0.7, at most about 0.8, at most about 0.9, at most about 1.0, at most about 1.1, at most about 1.2, at most about 1.3, at most about 1.4, at most about 1.5, at most about 1.6, at most about 1.7, at most about 1.8, at most about 1.9, at most about 2.0, at most about 2.1, at most about 2.2, at most about 2.3, at most about 2.4, at most about 2.5, at most about 2.6, at most about 2.7, at most about 2.8, at most about 2.9, or at most about 3.0 g / cm 3 It may be.

[0035] The carbon precursors may be utilized for the fabrication of one or more components of chemical or electrochemical devices, such as a PEMFC, as shown schematically in Figure 1. Non-limiting examples of uses for the carbon precursors made according to one or more embodiments disclosed herein include high surface area carbon applications, carbon supports for electrocatalysts in fuel cell cathodes, anode materials, carbon materials for supercapacitors, lithium-ion batteries, lithium-air batteries, CO2 reduction cells, and the like.

[0036] Unlike many of the applications discussed so far, the carbon structures may have defects that are intentionally utilized as part of the manufacturing process disclosed herein.

[0037] The process may include multiple steps. The first step may involve obtaining graphene as a two-dimensional material of single-layer atomic carbon, a low-layer multi-layer graphene material containing graphene sheets with a few layers, not exceeding 10, or a combination thereof. Graphene is a two-dimensional carbon material in which each carbon atom is bonded to its three nearest neighbors, and is characterized by 2s, 2p, and 3s bonds. x , and 2p y orbitals, and 2p z Orbital sp 2 Hybridization results in the formation of delocalized π and π* bands perpendicular to the graphene plane. Graphene is a two-dimensional crystal, a solid material containing a single layer of atoms arranged in a regular pattern. Due to its two-dimensional nature, graphene has strong bending fluctuations characterized by "ripples" and "corrugations." Pristine graphene is nonmagnetic and has a zero band gap.

[0038] The process may include exfoliating graphite to obtain a plurality of graphene flakes, which may be by mechanical exfoliation, liquid-phase exfoliation, layer-engineered exfoliation, large-scale chemical vapor deposition, or the like.

[0039] Graphene flakes may contain one or more structural defects such as topological defects, single vacancies, multiple vacancies, multilayer flaking, foreign atoms, substitutional impurities such as B, N, etc., line defects, grain boundaries, stacking faults, lattice discontinuities, crystallographic defects including Stone-Wales defects or rotations of two-bonded carbon atoms that result in distortion of the hexagonal network, lattice irregularities, edge defects, edge reconstructions, grain boundaries, dislocations, strain, dangling bonds, etc., or combinations thereof. The defects may be two-dimensional, three-dimensional, or both. The defects may be intrinsic, extrinsic, or both.

[0040] The process can utilize defective and / or defect-free exfoliated graphene flakes. This utilization does not involve discrimination, and thus any or all of the graphene flakes obtained in the exfoliation step can be utilized. Alternatively, the process can utilize more than 25%, more than 50%, or more than 75% defective graphene flakes, with the remainder being defect-free graphene flakes. The process can utilize only defect-free, pristine graphene flakes. However, defective graphene flakes are preferred. The process can utilize only graphene flakes with the specific types of defects listed above.

[0041] The process may be performed by adjusting one or more parameters, such as the final target density of the precursor (e.g., 1 to 3.5 g / cm). 3 In a non-limiting example, when the target precursor structure is an onion-shaped graphitic carbon mesostructure, the graphene flakes may be selected based on a density of 3.5 g / cm. 3 In another non-limiting example, if the target precursor structure is a single-layer graphitic carbon mesostructure, one may select exfoliated graphene sheets with a higher density, closer to 1 g / cm. 3 Another parameter may be the size of the graphene flakes, which influences the final size of the precursor structure. The dimensions of the graphene flakes range from about 0.005 to 500 × 10 4 μm 2 , 0.05 to 500 × 10 3 μm 2 , or 0.5 to 500 × 10 2 μm 2 It may be.

[0042] In a subsequent step, the process may include modifying the graphene flakes. This process may include decorating the graphene flakes with one or more deposition structures. "Decoration" refers to the deposition of materials. This decoration may be performed to ensure a specific length scale, to avoid stacking of graphene and graphene-like flakes into higher layers that do not anneal to the desired structure, to target a specific amorphous structure density as disclosed above, or a combination thereof. The deposition material may aggregate on the surface of the graphene flakes. This deposition step introduces heterogeneity in the pore size distribution of the graphene flakes and ultimately the graphitic precursor structures. This heterogeneity in the pore size distribution may also provide preferential pathways for water and gas transport in the catalyst layer of a PEMFC. For example, large pores are favorable for water accumulation, while nanopores are available for gas transport.

[0043] The deposited structures may include non-graphene carbon structures, non-limiting examples of which include nanostructures, C 60 (Soccer ball-shaped molecule consisting of 60 carbon atoms)~C 80 Examples of fullerenes include fullerene-like carbon balls, such as buckminsterfullerenes, linked ball-and-chain dimers, heterofullerenes, endohedral metallofullerenes, fullerenols, buckyball clusters, carbon nanorods, carbon nanotubes (both single- and multi-walled in armchair or zigzag configurations), spherical nanocarbons, or combinations thereof. Fullerenes are carbon allotropes whose molecules consist of carbon atoms linked by single and double bonds to form fused rings or closed or partially closed meshes with 5-7 atoms. Carbon nanorods are elongated particles ranging from about 10 to 120 nm in size with specific surface areas of about 30-70 m. 2 / g. Carbon nanotubes are carbon allotropes, tubes made of carbon with nanoscale diameters and a regular hexagonal lattice. The non-graphene carbon structures may contain one or more defects as disclosed herein. Based on the total amount of non-graphene carbon structures deposited, at least about 1, at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, or at least about 100% may contain at least one defect.

[0044] Because graphene and graphene-like structures typically exhibit a high degree of stiffness, the process may include a secondary modification step. The secondary modification step may be performed to enhance the effectiveness of a subsequent wrinkling step. The secondary modification step may include introducing or inducing additional defects in the graphene and graphene-like structures. The additional defects are intended to enable bending of the graphene sheets. The secondary modification step may include etching the graphene structures with acid, water vapor, plasma, or a combination thereof. The process may include controlling the density of the additional defects to control the shape of the carbon nanostructures. For example, introducing a high defect density can result in small primary structures, while introducing a low defect density can result in large primary structures. The additional defects can also serve as catalyst attachment sites, improve the ionomer interaction of the catalyst, and thereby improve the quality of the catalyst layer, or both.

[0045] The process may then include a step of crumpling the modified graphene flakes disclosed above. Crumbling refers to a process of deforming the structure of graphene, which may result in the formation of wrinkles within the graphene structure, a transformation from a two-dimensional to a three-dimensional structure, a wrinkled shape, creases, or the like. Crumple graphene comprises graphene flakes held together by weak van der Waals forces.

[0046] The crumpling step may involve decorated graphene flakes with or without defects, undecorated graphene flakes with or without defects, or a mixture thereof. Wrinkling can be induced by the presence of polar solvents, i.e., water, alcohols, or acetone (because polar interactions between the solvent and graphene induce wrinkling in unsupported graphene), charging of the graphene layers, modifying the polarity / interactions of the solvent with additives such as organic or inorganic salts, mechanical means, i.e., ball milling or wet / dry mixing, or a combination thereof. The crumpling step results in wrinkled modified graphene or graphene-like precursor materials as disclosed herein.

[0047] As described herein, the presence of primary and additional defects can provide additional sites susceptible to deformation during the wrinkling step. Because the presence of defects can cause the graphene hexagonal lattice to have structural deviations that reduce its strength, the defect locations can exhibit different deformation than the rest of the lattice, potentially contributing to further bends, folds, or deformations within the wrinkled structure.

[0048] The wrinkled structure can then be annealed. Annealing is a post-treatment performed for various reasons, such as to remove residues from solvent applications. The annealing can be thermal annealing, rapid thermal annealing, current annealing, or the like. Annealing can be performed at temperatures of about 200-2800°C, about 500-1500°C, or about 800-1200°C. Annealing can be performed under high vacuum or under a reducing gas atmosphere such as Ar, H2, or N2, or a combination thereof.

[0049] The process may include one or more steps of verifying the defect density in the unmodified graphene flakes, the defect density in the modified graphene flakes, the defect density in the resulting wrinkled precursor structure, the density of the carbon precursor, the porosity of the carbon precursor, etc., or a combination thereof. This verification may be performed, for example, by transmission electron microscopy, Raman spectroscopy, or electron energy loss spectroscopy.

[0050] The process may include steps of altering, adjusting, increasing, maintaining, or preserving the density, defect density, porosity, surface area, or combinations thereof, of the graphene flakes or resulting carbon precursor. Thus, the process may include setting a predetermined target value for the density, defect density, surface area, porosity, or combinations thereof of the graphene flakes or resulting carbon precursor, measuring or evaluating the target value during and / or after the fabrication process, monitoring whether the predetermined target value is being achieved during the process, and correcting the target value by adjusting the process, e.g., repeating one or more steps, taking corrective action to meet the predetermined value, or a combination thereof.

[0051] The process may include introducing a predetermined amount of defects and / or additional defects into the graphene flakes. The predetermined amount may relate to a percentage of the flakes that are affected by the defects and / or additional defects, where the percentage is about 1, about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, about 65, about 70, about 75, about 80, about 85, about 90, about 95, or about 100%, or at least about 1, at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about at most about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, or at least about 100%, or at most about 1, at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, at most about 50, at most about 55, at most about 60, at most about 65, at most about 70, at most about 75, at most about 80, at most about 85, at most about 90, at most about 95, or at most about 100%. This predetermined amount can relate to any amount of defective graphene flakes that results from an intentional step of including defective graphene flakes or an intentional step of not removing or excluding defective graphene flakes from graphene flakes that are decorated, wrinkled, or both.

[0052] The process steps described above can be performed before any catalyst deposition. Thus, the resulting carbon precursor can be free of any catalytic material, such as a noble metal, specifically Pt, Pd, their oxides, or combinations thereof. The catalyst can be deposited on the precursor in a later stage of processing.

[0053] The graphene modifications disclosed herein affect the arrangement, structure, and properties of the resulting precursor structure. The wrinkled modified graphene precursors disclosed herein may contain undulations, pockets, cavities, shapes, and folds configured to trap and retain electrocatalysts as a result of the processes disclosed herein. For example, the precursors may contain wrinkled, partially closed fused carbon rings, pentagonal and heptagonal rings within a hexagonal lattice, undulating, primarily hexagonal networks with discontinuities such as grooves throughout the network, variations on a primarily flat graphene lattice, such as spherical bulges, ridges, waves, pores, holes, etc., or combinations thereof.

[0054] The amount of such catalyst-retention sites in the precursor structures is increased compared to unmodified wrinkled graphene and planar graphene sheets. Thus, the wrinkled structures disclosed herein may contain multiple sites with high affinity for electrocatalysts.

[0055] Typically, structures that serve as precursors for the fabrication of carbon-based building blocks are characterized by relatively low accessibility of their interior surfaces to catalysts, for example. While the methods for their preparation described above contribute to increased phase deviations, resulting in more than the usual amount of sites with high affinity for electrocatalysts, there is a need to develop methods for increasing the interior surface accessibility of carbon precursors prepared by alternative or conventional methods.

[0056] Additionally, the lack of site accessibility problem is exacerbated in structures with multilayer architectures, such as onion-layered mesostructures, which can occur when multilayer graphene is used in the precursor fabrication process instead of single-layer graphene.

[0057] Additionally, the overall activity of the electrochemical cell can be affected by depositing an insufficient amount of catalyst and / or by confining the catalyst to a higher concentration on a smaller support area, making the catalyst particles more susceptible to coalescence and forming undesirably larger catalyst aggregates or agglomerates with lower electrochemically active surface area per volume.

[0058] Therefore, there is a need to develop methods that result in a better distribution of the catalyst within the available surface of the carbon precursor.

[0059] In at least one embodiment, a method for increasing the accessibility of the interior surfaces of graphitic carbon precursor structures is disclosed. The graphitic structures may be those described above or may be any graphitic or graphene-based structure that serves as a precursor for the production of carbon components in electrochemical or chemical devices such as PEMFCs. These structures may be defect-free, contain defects, lattice topological anomalies, have an amorphous configuration, be irregular, asymmetric, curved, have one or more bends, undulations, holes, voids, etc. These structures may be nanometer (10 -9 meters) to micrometers (10 -6 The structures may have nanoscale, mesoscale, or microscale dimensions ranging from 100 microns to 100 microns (up to 100 microns). These structures may have high surface area, density, and other properties as disclosed herein.

[0060] The method may include one or more steps described herein. At least some steps may be repeated one or more times. The method may include one or more cycles. The method may include 1 to 10, 2 to 8, or 3 to 6 cycles.

[0061] The method may involve taking advantage of water's unique volume-temperature properties, specifically its anomalous expansion. Above 4°C, water's volume increases with increasing temperature, but below 4°C, water's volume increases with decreasing temperature. Thus, as the temperature drops below 4°C and approaches 0°C, water expands rather than contracts. This behavior decreases the density of water, and at 0°C, water reaches its maximum volume as ice. In other words, in the temperature range of -10 to ±10°C, water's minimum volume (or maximum density) is achieved at 4°C. Therefore, below 4°C, water trapped in a space expands, potentially damaging the boundaries of the enclosed space that holds the water.

[0062] In an initial step, the method may include wetting the precursor or providing water to a space containing the low-access precursor. The space may be fully or partially enclosed within a container. Providing may include immersing with water, filling with liquid water, providing water vapor, steam, spraying, or a combination thereof. Providing may mean accumulating water until at least some or all of the precursor is submerged in water. Providing may be performed at approximately 4°C, which is the maximum density point of water. Providing may include adapting and selecting predetermined areas of the precursor to open them up or make them more accessible to catalysts, electrolytes, etc., or combinations thereof. Wetting may include wetting the interior surface, exterior surface, or both of the structure.

[0063] The method may include one or more methods for reducing the surface tension of water. For example, the method may include using water having a temperature greater than 4°C, since higher temperatures lead to lower surface tension. In another example, the method may include using one or more additives selected for this purpose, such as one or more surfactants. Yet another example may include electrowetting, or applying a voltage to a system to change the wettability of water with applied electricity.

[0064] In a subsequent step, the method may include rapidly freezing the wetted precursor. This step may also include melting, dissolving, or sublimation without melting or dissolving. The temperature fluctuation may range from about -200°C to about 10°C, about -195°C to about 4°C, or about -150°C to about 0°C. The freeze and thaw temperatures to which the system is subjected may be about -200, about -190, about -180, about -175, about -170, about -165, about -160, about -150, about -145, about -140, about -135, about -130, about -125, about -120, about -115, about -110, about -105, about -100, about -95, about -90, about -85, about -80, about -75, about -70, about -65, about -60, about -55, about -50, about -45, about -40, about -35, about -30, about -25, about -20, about -15, about −10, about −5, about 0, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10° C., at least about −200, at least about −190, at least about −180, at least about −175, at least about −170, at least about −165, at least about −160, at least about −150, at least about −145, at least about −140, at least about −135, at least about −130, at least about −125, at least about −120, at least about −115, at least about -110, at least about -105, at least about -100, at least about -95, at least about -90, at least about -85, at least about -80, at least about -75, at least about -70, at least about -65, at least about -60, at least about -55, at least about -50, at least about -45, at least about -40, at least about -35, at least about -30, at least about -25, at least about -20, at least about -15, at least about -10, at least about -5, at least about 0, at least about 1, at least about 2, at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, or at least about 10, or at most about -200, at most about -190, at most about -180, at most about -175, at most about -170, at most about -165, at most about -160, at most about -150, at most about -145, at most about -140, at most about -135,Maximum about -130, Maximum about -125, Maximum about -120, Maximum about -115, Maximum about -110, Maximum about -105, Maximum about -100, Maximum about -95, Maximum about -90, Maximum about -85, Maximum about -80, Maximum about -75, Maximum about -70, Maximum about -65, Maximum about -60, Maximum about -55, Maximum about -50, Maximum The temperature may be about -45, at most about -40, at most about -35, at most about -30, at most about -25, at most about -20, at most about -15, at most about -10, at most about -5, at most about 0, at most about 1, at most about 2, at most about 3, at most about 4, at most about 5, at most about 6, at most about 7, at most about 8, at most about 9, or at most about 10. The method may include rapid freezing, flash freezing, external freezing, use of liquid nitrogen, or another method for rapidly freezing the wetted precursor. Flash freezing refers to rapid freezing via direct contact with cryogenic or -196°C liquid nitrogen. Rapid freezing may involve instantaneous freezing within a time frame of a few seconds to about 30-60 seconds. Thus, rapid freezing may be about 1-90, about 10-60, or about 20-30 seconds. The quick freezing is performed at about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30, about 31, about 32, about 33, about 34, about 35, about 36, about 37, about 38, about 39, about 40, about 41, about 42, about 43, about 44, about 45, about 46, about 47, about 48, about 49, about 50, about 51, about 52, about 53, about 54, about 55, about 56, about 57, about 58, about 59, about 60, about 61, about 62, about 63, about 64, about 65, about 66, about 67, about 68, about 69, about 70, about 71, about 72, about 73, about 74, about 75, about 76, about 77, about 78, about 79, about 80, about 81, about 82, about 83, about 84, about 85, about 86, about 87, about 88, about 89, or about 90 seconds, or at most about 1, at most about 2, at most about 3, at most about 4, at most about 5, at most about 6, at most about 7, at most about 8, at most about 9, at most about 10, at most about 11, at most about 12, at most about 13, at most about 14, at most about 15, at most about 16,At most about 17, At most about 18, At most about 19, At most about 20, At most about 21, At most about 22, At most about 23, At most about 24, At most about 25, At most about 26, At most about 27, At most about 28, At most about 29, At most about 30, At most about 31, At most about 32, At most about 33, At most about 34, At most about 35, At most about 36, At most about 37, At most about 38, At most about 39, At most about 40, At most about 41, At most about 42, At most about 43, At most about 44, At most about 45, At most about 46, At most about 47, At most about 48, At most about 49, At most about 50, At most about 51, At most about 52, At most about 53, At most about The time may be up to about 54, up to about 55, up to about 56, up to about 57, up to about 58, up to about 59, up to about 60, up to about 61, up to about 62, up to about 63, up to about 64, up to about 65, up to about 66, up to about 67, up to about 68, up to about 69, up to about 70, up to about 71, up to about 72, up to about 73, up to about 74, up to about 75, up to about 76, up to about 77, up to about 78, up to about 79, up to about 80, up to about 81, up to about 82, up to about 83, up to about 84, up to about 85, up to about 86, up to about 87, up to about 88, up to about 89, or up to about 90 seconds.

[0065] Freezing causes the water present in and around the precursor to expand. The size of the ice crystals formed is a function of the freezing rate. Faster freezing can produce smaller ice crystals, which is desirable for creating small cracks in the precursor material. Rapid freezing therefore results in ice crystal growth throughout the structure, including inaccessible areas, which is the primary goal of the disclosed process. In contrast, slower freezing processes can result in macrocrystalline growth and ice crystal growth outside the pores and cavities of the precursor structure, which is undesirable.

[0066] Thus, the method may include adjusting, maintaining, regulating or varying the rate of freezing to obtain ice crystals having a predetermined or target size, which may be nanoscale, microscale, or both.

[0067] The method may then include melting or warming the frozen precursor. The melting may be rapid, slow, all at once, stepwise, continuous, incremental, or about 25, 50, 60, 70, 80, or 90% slower than freezing. Preferably, the melting is continuous and slow. Alternatively, the method may include sublimation, i.e., converting the frozen liquid to a gaseous state without the fluid becoming a liquid.

[0068] The volume change of water, caused by the change in temperature, can be used to damage or break down structures that are less accessible, making them more open or accessible, and creating mechanical defects. The cracks and fractures caused by flash freezing can expose previously inaccessible areas. These cracks and fractures can change the structure's shape, including changing the number and / or size of pores, changing the angles between structural sites, breaking the lattice, forming channels and holes within the lattice, increasing the interlayer distance in multilayer structures, etc., or a combination thereof. This process can increase porosity, decrease density, or both.

[0069] The rapid freezing and warming can be repeated several times. For example, the freezing and thawing cycle can be repeated one, two, three, four, five, six, seven, eight, nine, ten, or more times. This repetition can be particularly useful for precursors such as multilayered, onion-like graphite shells that would be difficult to access with a single flash-freezing procedure. Repeated cycles can make the graphitic carbon structure progressively more accessible. The final warming step can be continued for an extended period of time to facilitate draining water from the system.

[0070] The method may include removing water from the structure. Removing may include draining, drying, etc., or a combination thereof. Removal may be rapid or gradual.

[0071] There are several reasons why water is a suitable fluid for implementing this method. First, the expansion anomaly of water discussed above. Second, water is normally present during fuel cell operation, thus minimizing the risk of contamination. Other fluids whose volume expands upon freezing, such as gallium, may also be contemplated. However, some materials may not be suitable for the fuel cell environment.

[0072] The type of water used in this method can be adapted based on the desired results. For example, pure water or deionized bulk water can be used to immerse the structure in water, resulting in the formation of crystals on the order of a few microns. The water can be tap water, filtered water, or other relatively mineral-free water. Water containing minerals is also contemplated, although the presence of minerals can lower the freezing point. The water can also contain additional ingredients, such as glycerol, glycerin, or the like, or combinations thereof.

[0073] Freezing and thawing can cause the crystals to develop microscale cracks. Alternatively, water mixed with glycerol can form smaller nanoscale crystals, which in turn can induce smaller cracks in the nanoscale carbon structure. Additionally, the structure can be first exposed to steam and then only partially wetted with pure water, thereby creating cracks in only a portion of the structure. Thus, the method can include selecting and determining which portions of the structure should be made open or more accessible, what size cracks are desired, or both. Thus, the method allows for tailoring of results based on specific applications.

[0074] Additionally, the method may include selecting, measuring, evaluating, confirming, controlling, or modifying the porosity of the structure based on a predetermined value. The method may include repeatedly checking the porosity distribution, density, or both throughout the process. The method may include adding another freeze / thaw cycle if necessary to increase the porosity to a predetermined target value. The method may include assessing an initial porosity and increasing the porosity of the structure based on the initial value.

[0075] As disclosed above, because the precursor graphene-like structure is very rigid, the method may include introducing defects. A structure with more defects may be better wettable. Thus, the method may include increasing the incidence of defects in the structure by one or more steps disclosed herein.

[0076] The accessibility of the structures described above can be increased by an alternative method described herein. This alternative method can be used instead of or in addition to the freeze-thaw method. The method can include one or more steps described herein. The method can include voltage-induced platinum ion bombardment of the structures.

[0077] The method may include preparing the electrocatalyst atoms. The electrocatalyst may be Pt, Pd, an oxide thereof, an alloy thereof, or a combination thereof. This preparing may include depositing or growing the catalyst atoms into agglomerates or aggregates, including nanoclusters, clusters, small nanoparticles with dimensions less than about 250 atoms, or combinations thereof. While the term "aggregates" is used herein, agglomerates, clusters, nanoclusters, and small nanoparticles with dimensions less than about 250 atoms, or combinations thereof, are also within the scope of the disclosure. The aggregates or clusters may be monodisperse or quasi-monodisperse, which refers to relatively little size variation between aggregates. This size distribution may vary from about tens to hundreds of atoms. In a non-limiting example, the size distribution may include aggregates or clusters with fewer than 25 atoms to more than 100 atoms. The aggregates or clusters may also be polydisperse, such that the size distribution of the aggregates or clusters is broader than that of a monodisperse population.

[0078] After the aggregates or clusters are formed, the method may include sorting or selecting the aggregates or clusters based on one or more criteria. The criteria may include the goals disclosed herein. In addition, the criteria may include considerations such as efficiency. For example, smaller aggregates or clusters, such as those of tens of atomic units, may be easier to sort due to their smaller mass and easier to accelerate due to their lower voltage requirements.

[0079] The method may include applying a voltage to the agglomerates or clusters to accelerate the catalyst agglomerates or clusters toward the precursor structure. In a non-limiting example, this voltage may be provided by an electrostatic Van de Graaff accelerator. This acceleration may result in the agglomerates or clusters impinging on the structure. This impingement may result in at least a portion of the agglomerates or clusters penetrating the surface and mass of the structure. This penetration may reach a certain depth, as described below. This impingement may result in significant mechanical deformation and defects in the structure, thereby distorting the lattice, forming pores, channels, increasing the interlayer distance of the structure, etc., and increasing the accessibility of the surface to the catalyst.

[0080] The energy imparted to the aggregates or clusters may be either constant regardless of the size of the aggregates or clusters, or constant per atom. The method may include ionizing the structures. Thus, the method may include generating an isoenergetic ion beam to produce constant energy regardless of the size of the aggregates or clusters, or generating an isovelocity beam to produce constant energy per atom. For nearly monodisperse aggregates or clusters, they are composed of approximately the same number of atoms, so isoenergetics equals isovelocity. For polydisperse aggregates or clusters, isoenergetics does not equal isovelocity. The term "equi" is related to the term equal, which comes from the Latin "aequi." Alternatively, the aggregates or clusters may be monodispersed by a high-voltage glow discharge or arc discharge as disclosed herein.

[0081] Non-limiting example voltage and energy / atom ranges can be about 1-10, about 2-8, or about 3-7 MV, and tens of keV to tens of MeV / atom, e.g., 10 keV-99 MeV / atom, 30 keV-70 MeV / atom, or 40 keV / atom-60 MeV / atom. The voltage and energy per atom may be about 1, about 1.5, about 2, about 2.5, about 3, about 3.5, about 4, about 4.5, about 5, about 5.5, about 6, about 6.5, about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, or about 10 MV, and about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, about 65, about 70, about 75, about 80, about 85, about 90, about 100, about 150, about 200, about 250, about 350, about 400, about 450, about 550, about 600, about 650, about 700, about 750, about 800, about 850, about 900, about 1000, about 1500, about 2000, about 3500, about 4000, about 4500, about 5500, about 6000, about 6500, about 7000, about 7500, about 8000, about 8500, about 9000, about 1000, about 1500, about 2000, about 3500, about 4000, about 4500, about 5000, about 5500, about 6000, about 6500, about 7000, about 7500, about 8000, about 8500, about 9000, about 1000, about 1500, about 2000, about 350 00, about 250, about 300, about 350, about 400, about 450, about 500, about 550, about 600, about 650, about 700, about 750, about 800, about 850, about 900, about 950, about 1000, about 1050, about 1100, about 1150, about 1200, about 1250, about 1300, about 1350, about 1400, about 1450, about 1500, about 1550, about 1600, about 1650, about 1700, about 1750, about 1800, about 1850, approximately 1900, approximately 1950, approximately 2000, approximately 3000, approximately 4000, approximately 5000, approximately 6000, approximately 7000, approximately 8000, approximately 9000, approximately 10000, approximately 15000, approximately 20000, approximately 30000, approximately 35000, approximately 40000, approximately 45000, approximately 50000, approximately 55000, approximately 60000, approximately 65000, approximately 70000, approximately 75000, approximately 80000, approximately 85000, approximately 90000, approximately 95 000, or about 99000 keV / atom, at least about 1, at least about 1.5, at least about 2, at least about 2.5, at least about 3, at least about 3.5, at least about 4, at least about 4.5, at least about 5, at least about 5.5, at least about 6, at least about 6.5, at least about 7, at least about 7.5, at least about 8, at least about 8.5, at least about 9, at least about 9.5, or at least about 10 MV, and at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 100, at least about 150, at least about 200, at least about 250, at least about 300, at least about 350, at least about 400, at least about 450, 50, at least about 500, at least about 550, at least about 600, at least about 650, at least about 700, at least about 750, at least about 800, at least about 850, at least about 900, at least about 950, at least about 1000, at least about 1050, at least about 1100, at least about 1150, at least about 1200, at least about 1250, at least about 1300, at least about 1350, at least about 1400, at least about 1450, at least about 1500, at least about 1550, at least about 1600, at least about Also about 1650, at least about 1700, at least about 1750, at least about 1800, at least about 1850, at least about 1900, at least about 1950, at least about 2000, at least about 3000, at least about 4000, at least about 5000, at least about 6000, at least about 7000, at least about 8000, at least about 9000, at least about 10000, at least about 15000, at least about 20000, at least about 30000, at least about 35000, at least about 40000, at least about 45000, about 50,000, at least about 55,000, at least about 60,000, at least about 65,000, at least about 70,000, at least about 75,000, at least about 80,000, at least about 85,000, at least about 90,000, at least about 95,000, or at least about 99,000 keV / atom, or at most about 1, at most about 1.5, at most about 2, at most about 2.5, at most about 3, at most about 3.5, at most about 4, at most about 4.5, at most about 5, at most about 5.5, at most about 6, at most about 6.5, at most about 7, or at most about 7.5, at most about 8, at most about 8.5, at most about 9, at most about 9.5, or at most about 10MV, and at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, at most about 50, at most about 55, at most about 60, at most about 65, at most about 70, at most about 75, at most about 80, at most about 85, at most about 90, at most about 100, at most about 150, at most about 200, maximum about 250, maximum about 300, maximum about 350, maximum about 400, maximum about 450, maximum about 500, maximum about 550, maximum about 600, maximum about 650, maximum about 700, maximum about 750, maximum about 800, maximum about 850, maximum about 900, maximum about 950, maximum about 1000, maximum about 1050, maximum about 1100, maximum about 1150, maximum about 1200, maximum about 1250, maximum about 1300, maximum At most about 1350, at most about 1400, at most about 1450, at most about 1500, at most about 1550, at most about 1600, at most about 1650, at most about 1700, at most about 1750, at most about 1800, at most about 1850, at most about 1900, at most about 1950, at most about 2000, at most about 3000, at most about 4000, at most about 5000, at most about 6000, at most about 7000, at most about 8000, at most about 9000, at most At most about 10,000, at most about 15,000, at most about 20,000, at most about 30,000, at most about 35,000, at most about 40,000, at most about 45,000, at most about 50,000, at most about 55,000, at most about 60,000, at most about 65,000, at most about 70,000, at most about 75,000, at most about 80,000, at most about 85,000, at most about 90,000, at most about 95,000, or at most about 99,000 keV / atom.

[0082] The depth to which an aggregate or cluster travels through the carbon structure and stops is a function of the energy of this aggregate or cluster. Thus, the following cases are relevant:

[0083] (A) Isoenergetic (or isokinetic) with monodisperse aggregates or clusters. In this case, the collision of the aggregates or clusters generates a nearly uniform size population of deposited catalyst at a nearly uniform depth in the carbon structure.

[0084] (B) Isoenergetic with polydisperse aggregates or clusters, where the deposited catalyst is deposited in heterogeneous size populations at approximately uniform depths in the carbon structure.

[0085] (C) Polydisperse and isokinetic, where a heterogeneous size population of deposited catalyst is deposited at a heterogeneous depth within the carbon structure.

[0086] The term "substantially uniform" can relate to a deviation of about ±1-5% from the mean value. For example, a substantially uniform size population can relate to an average size being ±1-5% of the average size. For example, a substantially uniform depth can relate to an average depth of deposited aggregates being ±1-5% of the average depth, thus including additional aggregates or clusters within that deviation range.

[0087] The method may include providing or selecting a predetermined depth or depths at which the aggregates or clusters should be deposited. This predetermined target may be set based on a desired degree, amount, or location of mechanical defects, a target porosity value for the carbon structure, a target amount and location of catalyst within the carbon structure, a distribution of catalyst within the carbon structure, or the like, or a combination thereof. As a non-limiting example, the target size of the deposited aggregates or clusters may range from several hundred to several thousand atoms, e.g., 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, or 9500 atoms. As non-limiting examples, the target diameter of the deposited aggregates or clusters may be about 2-5 nm, 2.2-4.8 nm, or 2.5-4.5 nm.The diameter may be about 2, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3, about 3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6, about 3.7, about 3.8, about 3.9, about 4, about 4.1, about 4.2, about 4.3, about 4.4, about 4.5, about 4.6, about 4.7, about 4.8, about 4.9, or about 5 nm, at least about 2, at least about 2.1, at least about 2.2, at least about at least about 2.3, at least about 2.4, at least about 2.5, at least about 2.6, at least about 2.7, at least about 2.8, at least about 2.9, at least about 3, at least about 3.1, at least about 3.2, at least about 3.3, at least about 3.4, at least about 3.5, at least about 3.6, at least about 3.7, at least about 3.8, at least about 3.9, at least about 4, at least about 4.1, at least about 4.2, at least about 4.3, at least about 4.4, at least about 4.5, at least about 4.6, at least about 4.7, at least about 4.8, at least about 4.9, or at least about 5 nm, or at most about 2, at most about 2.1, at most about 2.2, at most about 2.3, at most about 2.4, at most about 2.5, at most about 2.6, at most about 2.7, at most about 2.8, at most about 2.9, at most about 3, It may be at most about 3.1, at most about 3.2, at most about 3.3, at most about 3.4, at most about 3.5, at most about 3.6, at most about 3.7, at most about 3.8, at most about 3.9, at most about 4, at most about 4.1, at most about 4.2, at most about 4.3, at most about 4.4, at most about 4.5, at most about 4.6, at most about 4.7, at most about 4.8, at most about 4.9, or at most about 5 nm.

[0088] The method may further include assessing, measuring, and scanning the quality, quantity, and depth of penetration. If uniform depth penetration into the structure results, voltage scanning can be used to progressively access deeper / more robust regions of the structure. The term "more robust" refers to more difficult to access regions in a multi-layer configuration.

[0089] The application of voltage and the impact of the aggregates or clusters on the carbon structure can be repeated, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times. These repetitions can be performed using the same or different aggregates or clusters with different particle distributions, chemical compositions, or average sizes. These repetitions can be performed at the same or different energy and velocity as the previous round of application. These repetitions can be performed until one or more predetermined goals are achieved.

[0090] This repetition may include bombarding a carbon precursor and forming a layer of electrocatalyst on the precursor. The method may further include depositing additional carbon precursors followed by additional bombardment of electrocatalyst. This process may be repeated until a desired number of layers and / or electrocatalyst loading is achieved.

[0091] The method may include annealing to increase the mobility of the deposited catalyst aggregates or clusters, to encourage the fusion of small aggregates or clusters into larger ones until a desired target size is achieved, to repair any damage to the crystalline structure of the aggregates or clusters, etc., or combinations thereof.

[0092] While exemplary embodiments have been described above, it is not intended that these embodiments describe every possible form of the present invention. Rather, the terms used in the specification are terms of description rather than limitation, and it will be understood that various changes may be made without departing from the spirit and scope of the present invention. Additionally, features of various embodiments may be combined to form further embodiments of the present invention.

Claims

1. 1. A method for improving catalytic accessibility of a carbon precursor, comprising: exposing a graphene-based multilayer precursor structure to a plurality of electrocatalytic clusters by applying a voltage to accelerate the clusters toward the graphene-based multilayer precursor structure; The surface of the graphene-based multilayer precursor structure is provided with mechanical defects, A substantially uniform size population of deposited electrocatalysts is deposited at a substantially uniform depth within the graphene-based multilayer precursor structure. To generate each A method comprising:

2. 10. The method of claim 1, wherein the electrocatalytic clusters are monodisperse produced by an isoenergetic beam.

3. The method of claim 1 , wherein the electrocatalytic clusters are monodisperse, produced by a constant velocity beam.

4. The method of claim 1 , wherein the electrocatalytic clusters are polydisperse, produced by an isoenergetic beam.

5. The method of claim 1 , further comprising selecting a plurality of electrocatalysts based on a target cluster size of less than 100 atoms.

6. The method of claim 1 , further comprising selecting a plurality of electrocatalysts based on a target cluster diameter of about 2 to 5 nm.

7. 2. The method of claim 1, wherein the voltage is in the range of about 1 to 10 MV and several tens of keV / atom to several tens of MeV / atom.

8. 10. The method of claim 1, wherein the mechanical defects comprise exposed lattice portions that result in increased porosity of the graphene-based multilayer precursor structure.

9. 1. A method for improving catalytic accessibility of a carbon precursor, comprising: repeatedly bombarding a graphene-based multilayer precursor structure with a population of electrocatalytic clusters selected based on at least one predetermined value to gradually increase the porosity of the structure while depositing the electrocatalytic clusters within the structure, wherein the repeated bombardment comprises application of a constant ionization energy; A method comprising:

10. The method of claim 9 , wherein the at least one predetermined value comprises a target cluster size of less than 100 atoms.

11. The method of claim 9, wherein the at least one predetermined value comprises a target cluster diameter of about 2-5 nm.

12. The method of claim 9 , wherein the constant ionization energy comprises a constant energy per atom.

13. The method of claim 9 , wherein the constant ionization energy comprises a constant energy regardless of the size of the clusters.

14. The method of claim 9 , wherein the electrocatalytic clusters are monodisperse clusters.

15. 1. A method for depositing an electrocatalyst onto a carbon precursor, comprising: providing clusters of electrocatalyst particles based on cluster size uniformity; accelerating the clusters of electrocatalyst particles towards a graphene-based multilayer precursor structure by applying a voltage field in the range of about 1-10 MV and tens of keV / atom to tens of MeV / atom; impinging the accelerated clusters of electrocatalyst particles onto the graphene-based multilayer precursor structure to deposit the clusters of electrocatalyst particles based on a depth deposition criteria; A method comprising:

16. 16. The method of claim 15, wherein the uniformity of cluster sizes comprises approximately uniformly sized clusters having a deviation of about ±1-5% from an average cluster size.

17. The method of claim 15 , wherein the depth deposition standard comprises a substantially uniform size population of deposited catalyst at a substantially uniform depth within the carbon structure.

18. The method of claim 15 , wherein the depth deposition criteria comprises a non-uniform size population of deposited catalyst at a plurality of non-uniform depths.

19. The method of claim 15 , wherein the clusters are monodisperse.

20. The method of claim 15, further comprising increasing the number of mechanical defects in the carbon precursor.

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