Amorphous carbon precursors for graphitic structures

Abstract

Carbon precursor for use in the production of carbon substrates with a graphitic structure. The carbon precursor can comprise defective amorphous carbon spheres that exhibit a percentage mass loss compared to defect-free amorphous carbon spheres. The defective amorphous carbon spheres are capable of forming a single-layer graphitic structure for use as a carbon substrate. The carbon precursor for a graphitic structure can comprise amorphous carbon nanoclusters with a nominal nanocluster diameter of less than 3 nanometers. The amorphous carbon nanoclusters are capable of forming a single-layer graphitic structure for use as a carbon substrate.

Description

Technical area

[0001] The present disclosure relates to amorphous carbon precursors for graphitic structures (e.g., amorphous carbon precursors for single-layer graphitic structures). The amorphous carbon precursors for graphitic structures can be used to form single-layer graphitic structures for use as catalyst supports in proton exchange membrane fuel cells (PEMFCs) and other electrochemical cells. BACKGROUND

[0002] Proton exchange membrane fuel cells (PEMFCs) are an environmentally friendly energy conversion device. PEMFCs utilize an electrochemical reaction of the gases H2 and O2, delivering an actual energy efficiency of over 60%, producing only H2O as a product. The rapid diffusion of H ions allows PEMFCs to operate effectively at a relatively low temperature of approximately 100 °C. In contrast, solid oxide fuel cells and molten carbonate fuel cells operate at approximately 600 °C and above.

[0003] Despite the advantages of PEMFCs, their application in energy systems and lower-cost transportation technologies is limited by their high production costs and relatively poor durability. For example, the cost of manufacturing platinum (Pt) / carbon (C) electrocatalysts in PEMFC cathodes is at least half the price of a PEMFC, while the electrochemically active surface area (ECSA) of a Pt catalyst decreases significantly (e.g., 50% or more) during cycling. SUMMARY

[0004] In one embodiment, a carbon precursor for use in producing a carbon substrate having a graphitic structure is disclosed. The carbon precursor comprises defective amorphous carbon spheres that exhibit a percentage mass loss compared to defect-free amorphous carbon spheres. The defective amorphous carbon spheres are capable of forming a single-layer graphitic structure for use as a carbon substrate.

[0005] If the density of the defect-free amorphous carbon spheres is less than 2.5 g / cm 3 , the percentage mass loss can be over 70%. If the density of the defect-free amorphous carbon spheres is more than 2.5 g / cm 3, the percentage mass loss can be over 80%. The defective amorphous carbon spheres can have defects (e.g., cylindrical defects). The defective amorphous carbon spheres can be defective amorphous carbon spheres. The defect-free amorphous carbon spheres can include hollow spheres. The defective amorphous carbon spheres can have micropores of less than 2 nanometers in a range of 0.5 to 2.0 cm 3 / g.

[0006] In another embodiment, a carbon precursor for use in producing a carbon substrate with a graphitic structure is disclosed. The carbon precursor comprises amorphous carbon nanoclusters with a nominal nanocluster diameter of less than 3 nanometers. The amorphous carbon nanoclusters may be capable of forming a single-layer graphitic structure for use as a carbon substrate.

[0007] The amorphous carbon nanoclusters can have a density of 1 to 1.6 g / cm 3 If the amorphous carbon nanoclusters have a density of 1.6 to 2.4 g / cm 3 , the nominal nanocluster diameter can be less than 2 nanometers. If the amorphous carbon nanoclusters have a density of 2.4 to 3.0 g / cm 3 The nominal nanocluster diameter can be less than 1.6 nanometers. The amorphous carbon nanoclusters can contain defects.

[0008] In yet another embodiment, a method for producing a single-layer graphitic structure for use as a carbon substrate is disclosed. The method may include heat-treating amorphous carbon spheres to form a single-layer graphitic structure and forming the single-layer graphitic structure into the carbon substrate.

[0009] If the amorphous carbon spheres are defective amorphous carbon spheres, the method may further comprise forming the defective amorphous carbon spheres from starting amorphous carbon spheres. The forming step may comprise reducing the mass of the starting carbon spheres by a percentage mass loss to obtain the defective amorphous carbon spheres. The step may comprise bombarding the starting carbon spheres with ions. The forming step may comprise corroding the starting carbon spheres. The single-layer graphitic structure may be a single-layer graphitic shell. The carbon substrate may be configured to support an electrocatalyst. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a simplified side view of certain components of a proton exchange membrane fuel cell (PEMFC) according to one embodiment. Fig. Figure 2A shows a simplified view of a solid sphere of amorphous carbon graphitized into a graphitic carbon nano-onion. Fig. Figure 2B shows a simplified view of a hollow sphere of amorphous carbon graphitized into a single-layer graphitic hollow carbon shell. Fig. Figure 3A is a graph showing a distribution of the number of carbon per volume versus the distance to the center of the graphitic carbon nano-onion prepared in Fig. 2A, at different initial radii (ie approximately 6Å and approximately 10Å) and an initial density of 2.97 g / cm 3 is shown. Fig. Figure 3B is a diagram showing the evolution of the surface area of solid spherical nano-onions and hollow spheres at different initial radii and an initial density of 2.97 g / cm 3 is shown. Fig. Figure 4A is a graph showing the surface area of solid spherical nano-onions and hollow spheres as a function of the initial radius of the sphere at a density of 1.55 g / cm 3 is shown. Fig. Figure 4B is a graph showing the surface area of solid spherical nano-onions and hollow spheres as a function of the initial radius of the sphere at a density of 2.44 g / cm 3 is shown. Fig. Figure 5 shows a diagram of the surface of graphitized carbon spheres with different mass loss. Fig. Figure 6 shows a simplified view of amorphous carbon spheres with cylindrical defects with a mass reduction of over 70%, graphitized into single-layer graphitic carbon nanoclusters. Fig. Figure 7A shows a simplified view of amorphous carbon spheres with a radius of approximately 0.8 nm graphitized into single-layer graphitic carbon nanoclusters. Fig. Figure 7B shows a simplified view of amorphous carbon spheres with a radius of approximately 1.0 nm graphitized into bilayer graphitic carbon nanoclusters. DETAILED DESCRIPTION

[0010] Embodiments of the present disclosure are described herein. It should be understood, however, that the disclosed embodiments are merely examples, and further embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. Specific details of structure and function disclosed herein are therefore not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously utilize the present embodiments.Those of ordinary skill in the art will understand that various features illustrated and described with respect to any of the figures may be combined with features illustrated in one or more additional figures to create embodiments not explicitly illustrated or described. The illustrated feature combinations provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0011] Except in the examples or where otherwise expressly stated, all numerical quantities in this specification indicating amounts of material or reaction and / or usage conditions are to be understood as being modified by the word "approximately," thus describing the scope of the invention to the broadest extent possible. In general, practice within the specified numerical limits is preferred.In addition, unless expressly stated otherwise, percent, "parts of," and ratios are by weight; the description of a group or class of materials as suitable or preferred for a particular purpose in connection with the invention means that mixtures of any two or more of the elements of the group or class are equally suitable or preferred; the description of ingredients chemically refers to the ingredients at the time of addition to any combination specified in the description and does not necessarily preclude chemical interactions among the ingredients of a mixture once mixed.

[0012] The initial definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation in this document and applies accordingly to regular grammatical variants of the abbreviation defined at the beginning. Unless explicitly stated otherwise, the measured value of a property is determined using the same method as previously or subsequently specified for the same property.

[0013] It should also be noted that the singular form "a," "an," and "the," when used in the description and the appended claims, includes plural referents unless the context clearly indicates otherwise. For example, when referring to a component in the singular, a plurality of components is considered included.

[0014] The term "substantially," "generally," or "about," when used herein, means that the amount or value involved may be the specific stated value or some other value nearby. The term "about," when used to indicate a particular value, is generally intended to indicate a range within ± 5% of the value. As an example, the term "about 100" indicates a range of 100 ± 5, i.e., the range from 95 to 105. When the term "about" is used, it can generally be expected that similar inventive results or effects can be achieved within a range of ± 5% of the stated value. The term "substantially" may modify a value or relative property disclosed or claimed in the present disclosure.In these cases, "substantially" may mean that the value or relative characteristic it modifies is within ± 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or relative characteristic.

[0015] It should also be recognized that ranges of integers explicitly include all integers between them. For example, the range of integers 1 to 10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Likewise, the range 1 to 100 includes 1, 2, 3, 4, .... 97, 98, 99, 100. Likewise, if any range is claimed, intermediate digits that are increments of 10 divided by the difference between the upper and lower bounds may be used as alternative upper or lower bounds. For example, if the range is 1.1 to 2.1, the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 may be chosen as lower or upper bounds.

[0016] In the examples given in this document, concentrations, temperature and reaction conditions (e.g. pressure, pH, flow rates, etc.) can be applied with plus or minus 50 percent of the specified values, rounded or truncated to two significant figures of the value given in the examples. In a further development, concentrations, temperature and reaction conditions (e.g. pressure, pH, flow rates, etc.) can be applied with plus or minus 30 percent of the specified values, rounded or truncated to two significant figures of the value given in the examples. In a further development, concentrations, temperature and reaction conditions (e.g. pressure, pH, flow rates, etc.) can be applied with plus or minus 10 percent of the specified values, rounded or truncated to two significant figures of the value given in the examples.

[0017] For all compounds expressed as an empirical chemical formula with multiple letters and subscripts (e.g., CH2O), values for the subscripts may be plus or minus 50 percent of the stated values, rounded or truncated to two significant figures. For example, if CH2O is given, it is a compound with the formula C (0,8bis1,2) H (1,6bis2,4) O (0,8bis1,2) . In one further development, values for the subscripts may be plus or minus 30 percent of the stated values, rounded or truncated to two significant figures. In yet another further development, values for the subscripts may be plus or minus 20 percent of the stated values, rounded or truncated to two significant figures.

[0018] The term "and / or," as used in this document, means that either all or only one of the elements of the group may be present. For example, "A and / or B" means "only A, or only B, or both A and B." For "only A," the term also covers the possibility of B being absent, i.e., "only A but no B."

[0019] It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may, of course, vary. Furthermore, the terminology used herein is for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way.

[0020] The term "comprising" is synonymous with "having," "with," "containing," or "characterized by." These terms are inclusive and open-ended and do not exclude additional, unspecified elements or process steps.

[0021] The phrase "consisting of" excludes any element, step, or ingredient not recited in the claim. When this phrase appears in a paragraph in the body of a claim and does not immediately follow the preamble, it limits only the element recited in the paragraph; it does not exclude other elements from the claim as a whole.

[0022] The phrase “consisting essentially of” limits the scope of a claim to the specific materials or steps recited, in addition to those that do not substantially impair the basic and novel characteristic(s) of the claimed subject matter.

[0023] With respect to the terms "comprising," "consisting of," and "consisting essentially of," when any of these three terms are used herein, the subject matter disclosed and claimed herein may include the use of any of the other two terms.

[0024] The term "one or more" means "at least one," and the term "at least one" means "one or more." The terms "one or more" and "at least one" include "plural" as a subset.

[0025] The description of a group or class of materials as suitable for a particular purpose in conjunction with one or more embodiments means that mixtures of any two or more of the members of the group or class are suitable. The description of components chemically refers to the components at the time of addition to any combination specified in the description and does not necessarily preclude chemical interactions among components of a mixture once mixed. The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation in this document and applies accordingly to regular grammatical variants of the abbreviation defined at the outset.Unless explicitly stated otherwise, the measured value of a property is determined using the same method as previously or subsequently stated for the same property.

[0026] For example, platinum (Pt) / carbon (C) electrocatalysts can cost half as much to manufacture as a commercial proton exchange membrane fuel cell (PEMFC), and their aging over cycles shortens the lifetime of PEMFCs. The cost can be reduced by using high-surface-area carbon as the substrate while maintaining a large electrochemically active surface area of the Pt catalyst.

[0027] Optimizing the microstructure of a carbon substrate for a Pt catalyst is a promising step toward improving the durability and reducing the cost of a PEMFC. During the optimization step, a correlation between the surface area of a carbon substrate and the ECSA of a Pt catalyst deposited on a carbon substrate can be considered. For example, the larger the surface area of the carbon substrate, the higher the ECSA of Pt catalysts deposited on the carbon substrate when the same weight percentage of Pt loading is used. This trend can be attributed to the uniformly small size (e.g., an average diameter of approximately 3 nm) and uniform distribution of Pt nanoparticles on the carbon substrate with a relatively large surface area.Although a Pt / C electrocatalyst with high surface area carbon (HSAC) achieves a relatively high ECSA with a lower Pt loading, Pt / C electrocatalysts with HSAC still exhibit the same or similar reduction in ECSA during cycling as Pt / C electrocatalysts with low surface area carbon (LSAC). One proposal to improve the cycling stability of Pt / C is to replace oxygen-reactive amorphous carbon with less reactive graphitized carbon.

[0028] One proposal for producing graphitic carbon with a very high surface area involves a process using silver stencils. According to this process, a mesoporous nanodendritic carbon (MCND) structure is synthesized, resulting in primary particles containing bubble-like hollow graphitic carbon nanoparticles (HGCN) with surface pores. While typical HGCNs have a wall thickness of over 5 nm (e.g., over 10 graphite layers), an MCND structure can have a single-layer graphene wall, thus achieving a very high surface area (e.g., 1,610 m 2 / g) is reached.

[0029] While the MCND structure has proven promising for a very high-surface-area carbon substrate, there is still a need to produce graphitic carbon nanoparticles with a very high surface area. Durability can also be improved by replacing amorphous carbon with graphitic carbon, which is less reactive with oxygen.

[0030] In one or more embodiments, carbon precursors are disclosed from which graphitic carbon nanoparticles having a single-layer graphitic structure (e.g., graphitic shell or wall) and a very high surface area are prepared. Single-layer may refer to a layer of a two-dimensional material (e.g., graphite). Shells or walls may refer to a single-layer structure extending in three dimensions. Graphitic carbon nanoparticles may refer to carbon nanoparticles in which one or more graphite materials (e.g., a crystalline form of carbon atoms formed as hexagonal structures) are present. The one or more graphite materials may be formed from one or more graphene materials.In one or more embodiments, the carbon nanoparticles may be completely graphitic, meaning that 100% of the carbon nanoparticles comprise the one or more graphite materials. The high surface area may be in a range of 500 to 3,000 m². 2 / g, and in other embodiments in a range of 1,400 m 2 / g and beyond (e.g. 1,400 to 3,000 m 2 / g).

[0031] In one or more embodiments, carbon precursor structures are disclosed from which single-layer graphitic carbon mesostructures can be prepared that both possess desirable characteristics and mitigate the aging and cost problems of Pt / C electrocatalysts in PEMFCs. Carbon mesostructures can refer to structures in the mesoscale range between a microscopic range and a macroscopic range. The mesoscale range can range from nanometers (10 -9meters) and micrometers (10 -6 meters). The carbon precursor structures can have an amorphous carbon structure. Amorphous carbon structures can refer to a disordered or random arrangement of carbon atoms (e.g., having no defined crystalline structure). The carbon structure can be completely amorphous. The single-layer graphitic material can comprise carbon nanoclusters. Carbon nanostructures can refer to carbon materials with one or more dimensions in a nanoscale range (e.g., a range from 1 to 100 nanometers). These structures can also be used to synthesize carbon structures for other applications where a high surface area and good durability are specified, for example, as anode materials for alkaline-ion batteries.

[0032] Fig. 1 shows a simplified side view of certain components of a PEMFC 110 according to one embodiment. As shown in Fig. As shown in Figure 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 116 coated with a cathode catalyst layer 118 formed from a cathode catalyst material. Polymer electrolyte material (PEM) 120 extends between the anode catalyst support 112 and the cathode catalyst support 116. The cathode catalyst material may be distributed at an 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 located between the anode catalyst support 112 and the PEM 120. The cathode catalyst layer 118 is located between the cathode catalyst support 116 and the PEM 120.Anode 122 can generally refer to the anode catalyst support 112 and the anode catalyst layer 114. Cathode 124 can generally refer to the cathode catalyst support 116, the cathode catalyst layer 118, and the current collector (not shown). The PEMFC 110 also includes first and second gas diffusion layers (GDLs) (not shown). The first GDL is adjacent to the outer surface 126 of the anode catalyst support 112, and the second GDL is adjacent to the outer surface 128 of the cathode catalyst support 116.

[0033] In one or more embodiments, carbon precursor structures are disclosed in which graphitization occurs at a higher temperature (e.g., 3,000 K), thus forming carbon nanoparticles with single-layer graphitic walls. These carbon precursor structures can be confirmed using molecular dynamics simulations of the graphitization of amorphous carbon nanoparticles at the higher temperature.

[0034] Fig. Figure 2A shows a simplified view of a solid sphere of amorphous carbon 200 being graphitized into a graphitic carbon nano-onion 202 by heat treatment at approximately 3,000 K. The term nano-onion can be understood to refer to nested (e.g., concentric) graphitic carbon structures. Fig. Figure 2B shows a simplified view of a hollow amorphous carbon sphere 204 being graphitized into a single-layer graphitic hollow carbon shell 206 by heat treatment at approximately 3,000 K. The graphitization of the solid nanosphere and the hollow amorphous carbon nanosphere occurs in a carbon environment comparable to that of amorphous carbon with a density of 2.97 g / cm 3 and an average coordination number (CN) of 3.85. As in Fig. As shown in Figure 2A, starting carbons with a solid sphere result in a graphitic, yet onion-like shape, which can be undesirable because the onion shape reduces the available surface area of the carbon. For example, with an average KZ close to 3 at approximately 3,000 K, the inner layers of the graphitic carbon nano-onion 202 may be unattainable for certain applications (e.g., platinum deposition).

[0035] Fig. Figure 3A is a diagram showing a distribution of the number of carbon per volume to the distance to the center of the graphitic carbon nano-onion prepared in Fig. 2A, at different initial radii (ie approximately 6Å and approximately 10Å) and an initial density of 2.97 g / cm 3is shown. If smaller radii are used (e.g., approximately 6Å), the structure after heat treatment is made up of a single layer of carbon. Larger radii (e.g., approximately 10Å) result in a multi-layer graphitic structure. As shown in Fig. As shown in Figure 3A, the distances between peaks of the number of carbon per volume and the distance to the center of the sphere are between approximately 0.3 and 0.4 nm. This range corresponds to an experimentally measured interlayer distance between graphite layers (0.335 nm). In contrast, as shown in Fig. As shown in Figure 2B, hollow spheres of amorphous carbon are graphitized into single-walled graphitic shells. The differences in the properties of solid graphitic spheres and hollow graphitic spheres can lead to significant differences in the surface area.

[0036] Fig. Figure 3B is a diagram showing the evolution of the surface area of solid spherical nano-onions and hollow spheres at different initial radii and an initial density of 2.97 g / cm 3 is shown. Fig. Figure 3B demonstrates that any dimension (e.g., about 6Å to about 30Å) shown for a hollow carbon yields a carbon precursor according to one or more embodiments. Fig. Figure 3B also demonstrates that a non-hollow carbon cluster with a radius below a certain radius (e.g., approximately 6Å) yields a carbon precursor according to one or more embodiments. As in Fig. As shown in Figure 3B, the surface area of massive graphitic spheres decreases at 3,000 K inversely proportional to the radius of the spherical amorphous carbon precursors, whereas the surface area of graphitic spheres remains unchanged above 1,400 m 2 / g remains.

[0037] The graphitization of amorphous carbon nanoparticles can also be observed in simulations using two other models with experimentally determined densities and respective average concentrations. In the first model, 1.55 g / cm 3 and a concentration of 2.97. Fig. Figure 4A is a graph showing the surface area of solid spherical nano-onions and hollow spheres as a function of the initial radius of the sphere at a density of 1.55 g / cm 3 The second model can be used with 2.44 g / cm 3 and a concentration of 3.33. Fig. Figure 4B is a graph showing the surface area of solid spherical nano-onions and hollow spheres as a function of the initial radius of the sphere at a density of 2.44 g / cm 3 For both densities of these models, a similar development is observed, that hollow spheres have a constant surface area of over 1,400 m 2 / g, whereas the surface area of massive spherical nano-onions decreases with increasing spherical radius. Fig. 4A and Fig. 4B provide confirmation of the results of Fig. 3B, starting with different initial carbon densities. The previous observations on the graphitization of amorphous carbon nanoparticles can provide a basis for the development of one or more structures from amorphous carbon precursors that can be heat-treated at 3,000 K to yield a single-layer graphitic structure.

[0038] In one or more embodiments, the amorphous carbon precursor is a multi-defect amorphous carbon nanocluster. The multi-defect amorphous carbon nanocluster may have a high number of micropores (e.g., pores with a diameter of less than 2 nanometers). The high number of micropores may be in a range of 0.5 to 2.0 cm 3 / g. A percentage of the removed mass of the amorphous carbon nanoparticles can be used for amorphous carbon nanoparticles with a density of less than 2.5 g / cm 3 at least 70%. The percentage mass removed may be any of the following percentages or in a range between any two of the following percentages: 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, and 90%. For amorphous carbon nanoparticles with a density above 2.5 g / cm 3The mass can be reduced by at least 80%. The percentage mass removed can be any of the following percentages or a range between any two of the following percentages: 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, and 90%. For example, if the mass reduction is 80%, 80% of the atoms can be knocked out of the amorphous carbon structure in one knockout step using a process such as ion bombardment or corrosion.

[0039] Fig. Figure 5 shows a diagram of the surface of graphitized carbon spheres with different mass loss. Fig. Figure 5 shows that a lower initial carbon mass results in a larger surface area and more clearly graphitic carbon mesostructures. As in Fig. 5, the greater the percentage mass loss, the larger the surface area after heat treatment at 3,000 K. In one or more embodiments, heat treatment of structures with a mass loss of more than 70% for amorphous carbon nanoparticles with a density of less than 2.5 g / cm 3 Structures with a single graphitic wall and thus a large surface area of over 1,400 m 2 / g, comparable to that of single-walled graphitic hollow spheres.

[0040] Fig. Figure 6 shows a simplified view of amorphous carbon spheres 600 with cylindrical defects 602 with a mass reduction of over 70%, graphitized into single-layer graphitic carbon nanoclusters 604. In this embodiment, the carbon mesostructure is primarily single-layer and completely graphitic. Using sophisticated experimental characterization techniques, the mesostructured carbon structure can be determined. Non-limiting examples include transmission electron microscopy, Raman spectroscopy, and electron energy loss spectroscopy.

[0041] In one or more embodiments, the amorphous carbon precursors are amorphous carbon nanoclusters having an equivalent diameter of less than 3 nanometers (e.g., less than 2 nanometers). Fig. Figure 7A shows a simplified view of amorphous carbon spheres 700 with a radius of approximately 0.8 nanometers graphitized into single-layer graphitic carbon nanoclusters 702. Fig. Figure 7B shows a simplified view of amorphous carbon spheres 704 with a radius of approximately 1.0 nm, which are graphitized into bilayer graphitic carbon nanoclusters 706. The amorphous carbon spheres 700 and the amorphous carbon spheres 704 can have an initial density of 2.44 g / cm 3at 2,500 K to 4,000 K (e.g., 3,000 K). In one or more embodiments, below a certain initial size (e.g., a radius of less than approximately 0.9 nanometers), a heat treatment step results in predominantly single-layer graphitic carbon mesostructures. This has been observed even when no mass loss is induced. In one or more embodiments, at larger initial radii (e.g., a radius of greater than approximately 0.9 nanometers), the carbon mesostructure is graphitic but onion-shaped.

[0042] As in Fig.As shown in Figure 7B, amorphous carbon spheres 704 with a radius of approximately 1.0 nanometer are graphitized into two-layer graphitic carbon nanoclusters 706. In one or more embodiments, the diameter of the amorphous carbon nanoparticle to obtain a single-layer wall may be less than 2.0 nm, depending on the initial density. For amorphous carbon nanoparticles with an initial density of 1.55 g / cm 3 and 2.97 g / cm 3 A radius of less than 1.5 nanometers or 0.8 nanometers can be used to obtain carbon nanoclusters with a single-layer wall after heat treatment at 2,500 K to 4,000 K (e.g., 3,000 K). The amorphous carbon nanoclusters can have a density of 1 to 1.6 g / cm 3 If the amorphous carbon nanoclusters have a density of 1.6 to 2.4 g / cm 3The nominal nanocluster diameter can be less than 2 nanometers. If the amorphous carbon nanoclusters have a density of 2.4 to 3.0 g / cm 3 The nominal nanocluster diameter can be less than 1.6 nanometers. The amorphous carbon nanoclusters can contain defects.

[0043] The acts, methods, or algorithms disclosed herein may be transferred to or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Likewise, the acts, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media such as read-only memory (ROM) devices, and information modifiably stored on writable storage media such as floppy disks, magnetic tapes, compact discs, random access memory (RAM) devices, and other magnetic and optical media. The acts, methods, or algorithms may also be implemented in a software-executable object.Alternatively, the operations, methods, or algorithms may be performed in whole or in part using suitable hardware components, such as application-specific integrated circuits (ASICs), field-programmable logic gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or a combination of hardware, software, and firmware components.

[0044] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The terms used in the specification are for the purpose of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As described above, the features of various embodiments may be combined to form further embodiments of the invention that may not be expressly described or illustrated.While various embodiments may have been described as providing advantages or being preferred over other prior art embodiments or designs with respect to one or more desired characteristics, one of ordinary skill in the art will recognize that one or more features or characteristics may be omitted to achieve the desired system attributes overall, depending on the particular application and design. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, usability, weight, manufacturability, ease of assembly, etc.Thus, to the extent that embodiments are described as less desirable than other embodiments or prior art embodiments with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] A carbon precursor for use in producing a carbon substrate having a graphitic structure, the carbon precursor for a graphitic structure comprising: Defective amorphous carbon spheres exhibiting a percentage mass loss compared to defect-free amorphous carbon spheres, wherein the defective amorphous carbon spheres are capable of producing a single-layer graphitic structure for use as a carbon substrate. [2] A carbon precursor for a graphitic structure according to claim 1, wherein the density of the defect-free amorphous carbon spheres is less than 2.5 g / cm 3 and the percentage mass loss is over 70%. [3] A carbon precursor for a graphitic structure according to claim 1, wherein the density of the defect-free amorphous carbon spheres is more than 2.5 g / cm 3 and the percentage mass loss is over 80%. [4] The carbon precursor for a graphitic structure according to claim 1, wherein the defective amorphous carbon spheres have defects. [5] A carbon precursor for a graphitic structure according to claim 4, wherein the defects are cylindrical defects. [6] The carbon precursor for a graphitic structure according to claim 1, wherein the defective amorphous carbon spheres are defective amorphous carbon nanospheres. [7] The carbon precursor for a graphitic structure according to claim 1, wherein the defect-free amorphous carbon spheres comprise hollow spheres. [8] A carbon precursor for a graphitic structure according to claim 1, wherein the defective amorphous carbon spheres have micropores of less than 2 nanometers in a range of 0.5 to 2.0 cm 3 / g. [9] A carbon precursor for use in the production of a carbon substrate having a graphitic structure, the carbon precursor for a graphitic structure comprising: amorphous carbon nanoclusters with a nominal nanocluster diameter of less than 3 nanometers, wherein the amorphous carbon nanoclusters are capable of producing a single-layer graphitic structure for use as a carbon substrate. [10] The carbon precursor for a graphitic structure according to claim 9, wherein the amorphous carbon nanoclusters have an amorphous carbon nanocluster density of 1 to 1.6 g / cm 3 have. [11] The carbon precursor for a graphitic structure according to claim 9, wherein the amorphous carbon nanoclusters have an amorphous carbon nanocluster density of 1.6 to 2.4 g / cm 3 and the nominal nanocluster diameter is less than 2 nanometers. [12] The carbon precursor for a graphitic structure according to claim 9, wherein the amorphous carbon nanoclusters have an amorphous carbon nanocluster density of 2.4 to 3.0 g / cm 3 and the nominal nanocluster diameter is less than 1.6 nanometers. [13] A carbon precursor for a graphitic structure according to claim 9, wherein the amorphous carbon nanoclusters have defects. [14] A method of producing a single-layer graphitic structure for use as a carbon substrate, the method comprising: Heat treatment of amorphous carbon spheres and thus formation of a single-layer graphitic structure and Forming the single-layer graphitic structure to the carbon substrate. [15] The method of claim 14, wherein the amorphous carbon spheres are defective amorphous carbon spheres, and further comprising forming the defective amorphous carbon spheres from starting amorphous carbon spheres. [16] The method of claim 15, wherein the forming step comprises reducing the mass of the initial carbon spheres by a percentage mass loss to obtain the defective amorphous carbon spheres. [17] The method of claim 16, wherein the forming step comprises bombarding the carbon starting spheres with ions. [18] The method of claim 16, wherein the forming step comprises corroding the carbon seed spheres. [19] The method of claim 14, wherein the single-layer graphitic structure is a single-layer graphitic shell. [20] The method of claim 14, wherein the carbon substrate is adapted to support an electrocatalyst.

Images