Multimetallic compounds and methods for making and using the same

Abstract

For renewable energy technology to become ubiquitous, it is imperative to develop catalysts useful reactions such as, for example, efficient oxygen evolution reaction (OER) and hydrogen evolution (HER). In accordance with the purpose(s) of the present disclosure, described herein are compounds having one of the following the formula: ABX, ABCX, ABCDX, ABCDEX, ABCDEFX, or ABCDEFGX, wherein (1) A, B, C, D, E, F, and G are, independently, Cr, Mn, Fe, Co, Ni, Cu, and Zn, (2) A, B, C, D, E, F, and G are not the same element, and (3) X is absent or X is C, O, S, P, N, Te, Se, or As. The compounds described herein possess unique electrochemical properties.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to co-pending U.S. Provisional Patent Application No. 63 / 749,745, filed on January 27, 2025, the contents of which are incorporated by reference herein in their entireties.BACKGROUND

[0002] The rapid advancement of renewable energy technologies and the persistent demand for efficient, sustainable chemical processes have necessitated the development of novel materials with exceptional catalytic properties. The traditional catalytic materials, while effective, often suffer from limitations such as high cost, limited availability, and suboptimal stability under operational conditions. Noble metals like platinum, iridium, and ruthenium, for instance, are excellent catalysts for reactions like the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) but are neither cost-effective nor sustainable for large-scale deployment. Therefore, is a need for new compounds that can offer comparable or superior catalytic performance while being economically viable and sustainable.SUMMARY

[0003] For renewable energy technology to become ubiquitous, it is imperative to develop catalysts useful reactions such as, for example, efficient oxygen evolution reaction (OER) and hydrogen evolution (HER). In accordance with the purpose(s) of the present disclosure, described herein are compounds having one of the following the formula: ABX, ABCX, ABCDX, ABCDEX, ABCDEFX, or ABCDEFGX, wherein (1) A, B, C, D, E, F, and G are, independently, Cr, Mn, Fe, Co, Ni, Cu, and Zn, (2) A, B, C, D, E, F, and G are not the same element, and (3) X is absent or X is C, O, S, P, N, Te, Se, or As. The compounds described herein possess unique electrochemical properties.

[0004] Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described embodiments are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.

[0006] FIG. 1 shows the pXRD of PBA – derived monometallic sulfide: Co9S8. Reference pattern shown in blue (COD:1011005)

[0007] FIG. 2 shows the pXRD of PBA – derived monometallic phosphides: CoP and Ni2P. Reference pattern for CoP in pink (COD: 9008928) and Ni2P shown in light blue (ICSD: 646102).

[0008] FIG. 3 shows the pXRD of PBA – derived monometallic oxides, Fe3O4, Co3O4, NiO2. Reference pattern for Fe3O4 in green (ICSD: 75627) Co3O4 in pink (ICSD: 24210) and NiO2 shown in light be (COD: 1522025).

[0009] FIG. 4 shows the pXRD of PBA – derived FeCo bimetallic phosphides containing 95%, 60% and 20% Fe. Reference pattern for FeP in light blue (ICSD: 94379), Fe2P in green (COD: 1008826), CoP in pink (COD: 9008928), and Co3O4 in grey (ICSD: 24210).

[0010] FIG. 5 shows the pXRD of PBA – derived FeCo and FeNi bimetallic oxides, Fe3O4, Co3O4, NiO2. Reference pattern for Fe2O3 in dark green (ICSD: 15840), Fe3O4 in light green (ICSD: 75627) Co3O4 in pink (ICSD: 24210) and NiO2 shown in light be (COD: 1522025).

[0011] FIG. 6 shows pXRD of PBA – derived CrMnFeCoNi pentametallic high entropy materials, CrMnFeCoNiC, CrMnFeCoNiO, CrMnFeCoNiP, CrMnFeCoNiS, and CrMnFeCoNi alloy. Reference pattern for Fe2.4C in red (COD: 1545252), Ni3C in orange (ICSD: 17005), MnO2 in light green (COD:1514232), Co3O4 in dark green (ICSD: 24210), FeP in light blue (ICSD: 94379), CoP in dark blue (COD: 9008928), Co3S4 in purple (COD:1011005), MnO in light pink (COD: 9006660), Fe FCC (ICSD: 44862).

[0012] The drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope described herein, as other equally effective embodiments are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the embodiments. Additionally, certain dimensions may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements.DETAILED DESCRIPTION

[0013] Before the present compounds, compositions, articles, devices, and / or methods are disclosed and described, it is to be understood that the aspects described below are not limited to specific compounds, synthetic methods, or uses as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0014] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0015] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure.

[0016] Any recited method can be carried out in the order of events recited or in any other order that is logically possible. That is, unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

[0017] All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein can be different from the actual publication dates, which can require independent confirmation.

[0018] While aspects of the present disclosure can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present disclosure can be described and claimed in any statutory class.

[0019] It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed compositions and methods belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0020] Prior to describing the various aspects of the present disclosure, the following definitions are provided and should be used unless otherwise indicated. Additional terms may be defined elsewhere in the present disclosure.Definitions and abbreviations

[0021] In describing and claiming the disclosed subject matter, the following terminology will be used in accordance with the definitions set forth below.

[0022] As used herein, “comprising” is to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps, or components, or groups thereof. Moreover, each of the terms “by”, “comprising,”“comprises”, “comprised of,”“including,”“includes,”“included,”“involving,”“involves,”“involved,” and “such as” are used in their open, non-limiting sense and may be used interchangeably. Further, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of” and “consisting of.” Similarly, the term “consisting essentially of” is intended to include examples encompassed by the term “consisting of.

[0023] 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. Thus, for example, reference to “a solvent” includes, but are not limited to, mixtures or combinations of two or more such solvents, and the like.

[0024] It should be noted that ratios, concentrations, amounts, rates, and other numerical data can be expressed herein in a range format. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms a further aspect. For example, if the value “about 10” is disclosed, then “10” is also disclosed and “about 5 to about 15” is also disclosed.

[0025] When a range is expressed, a further aspect includes from the one particular value and / or to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g. the phrase “x to y” includes the range from ‘x’ to ‘y’ as well as the range greater than ‘x’ and less than ‘y’. The range can also be expressed as an upper limit, e.g. ‘about x, y, z, or less’ and should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, less than y’, and ‘less than z’. Likewise, the phrase ‘about x, y, z, or greater’ should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’, greater than y’, and ‘greater than z’. In addition, the phrase “about ‘x’ to ‘y’”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’ to about ‘y’”.

[0026] It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “about 0.1% to 5%” should be interpreted to include not only the explicitly recited values of about 0.1% to about 5%, but also include individual values (e.g., about 1%, about 2%, about 3%, and about 4%) and the sub-ranges (e.g., about 0.5% to about 1.1%; about 5% to about 2.4%; about 0.5% to about 3.2%, and about 0.5% to about 4.4%, and other possible sub-ranges) within the indicated range.

[0027] As used herein, the terms “about,”“approximate,”“at or about,” and “substantially” mean that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstances, the value that provides equivalent results or effects cannot be reasonably determined. In such cases, it is generally understood, as used herein, that “about” and “at or about” mean the nominal value indicated ±10% variation unless otherwise indicated or inferred. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about,”“approximate,” or “at or about” whether or not expressly stated to be such. It is understood that where “about,”“approximate,” or “at or about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0028] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; and the number or type of embodiments described in the specification.

[0029] Disclosed are the components to be used to prepare the compositions of the invention as well as the compositions themselves to be used within the methods disclosed herein. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds cannot be explicitly disclosed, each is specifically contemplated and described herein. For example, if a particular compound is disclosed and discussed and a number of modifications that can be made to a number of molecules including the compounds are discussed, specifically contemplated is each and every combination and permutation of the compound and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations, A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using the compositions of the invention. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the methods of the invention.

[0030] It is understood that the compositions disclosed herein have certain functions. Disclosed herein are certain structural requirements for performing the disclosed functions, and it is understood that there are a variety of structures that can perform the same function that are related to the disclosed structures, and that these structures will typically achieve the same result.

[0031] As used herein, the terms “optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance and instances where it does not.

[0032] The term “alkyl” as used herein is a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, s-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkyl group can be cyclic or acyclic. The alkyl group can be branched or unbranched. The alkyl group can also be substituted or unsubstituted. For example, the alkyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, amino, ether, halide, hydroxy, nitro, silyl, sulfo-oxo, or thiol, as described herein. A “lower alkyl” group is an alkyl group containing from one to six (e.g., from one to four) carbon atoms. The term alkyl group can also be a C1 alkyl, C1-C2 alkyl, C1-C3 alkyl, C1-C4 alkyl, C1-C5 alkyl, C1-C6 alkyl, C1-C7 alkyl, C1-C8 alkyl, C1-C9 alkyl, C1-C10 alkyl, and the like up to and including a C1-C24 alkyl.

[0033] The term “alkyl amine” is a compound represented by the formula R-NH2, where R is an alkyl group as defined herein.

[0034] The term “alkyl thiol” is a compound represented by the formula R-SH, where R is an alkyl group as defined herein.

[0035] The term “alkyl phosphine” is a compound represented by the formula (R)3P, where at least one of R is an alkyl group as defined herein. The term “trialkyl phosphine” is a compound represented by the formula (R)3P, where each R is an alkyl group as defined herein.Multimetallic Compounds and Applications Thereof

[0036] In accordance with the purpose(s) of the present disclosure, described herein are compounds having one of the following the formula: ABX, ABCX, ABCDX, ABCDEX, ABCDEFX, or ABCDEFGX, wherein (1) A, B, C, D, E, F, and G are, independently, Cr, Mn, Fe, Co, Ni, Cu, and Zn, (2) A, B, C, D, E, F, and G are not the same element, and (3) X is absent or X is C, O, S, P, N, Te, Se, or As.

[0037] Depending upon the reaction conditions and reactants used, a variety of different multimetallic compounds can be prepared. The compounds described herein can be produced from a Prussian blue analog (PBA). In one aspect, the Prussian blue analog is produced by mixing salts of any of the metals described herein in specified amounts in a solvent. The Examples provide non-limiting procedures for making the Prussian blue analogs.

[0038] In one aspect, cyanometallate salts are used to produce the Prussian blue analog. In one aspect, the cyanometallate salt is Y3Fe(CN)6, Y2Ni(CN)4, Y3Cr(CN)6, Y3Mn(CN)6, Y3Co(CN)6, Y2Zn(CN)4, or YCu(CN)2, where Y is Li, Na, or K. In one aspect, the cyanometallate salts are mixed in water, where the relative molar amount of the salts is varied. Additional salts can be added to form the Prussian blue analog (PBA). In one aspect, metal halide salts can be added in addition to the cyanometallate salt. For example, when the multimetallic compound includes iron, K3Fe(CN)6 and FeCl2, can be used to produce the Prussian blue analog. The Prussian blue analog is produced as crystals that can subsequently be isolated. The Examples provide non-limiting procedures for isolating the Prussian blue analog.

[0039] In one aspect, the relative amount of each metal used to produce the Prussian blue analog and ultimately the multimetallic compounds described herein can vary in order to fine tune the electrocatalytic activity of the compounds. In one aspect, the molar ratio (e.g., A to B, A to C, B to C, c to D, etc.) of each metal salt and ultimately the metal present in the compounds described herein is from about 0.1:1 to about 99:1, or about 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 95:1, or 99:1, where any value can be a lower and upper endpoint of a range (e.g., 0.5:1 to 1.5:1). In another aspect, the molar ratio of each element relative to the other elements is from 0.8:1 to 1.2:1. In another aspect, the compounds described herein have stoichiometric amounts of each metal.

[0040] In one aspect, the compounds described herein are carbides (i.e., X is C). In one aspect, the carbide is produced by heating the Prussian blue analog with an alkyl amine under an inert atmosphere to produce the compound. In one aspect, the alkyl amine is a C10 to C20 alkyl amine such as, for example, octadecyl amine. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of an alkyl amine. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 300 oC to 350 oC). The Examples provide non-limiting procedures for making and isolating the carbide compounds described herein.

[0041] In one aspect, the compounds described herein are sulfides (i.e., X is S). In one aspect, the sulfide is produced by heating the Prussian blue analog under an inert atmosphere with an alkyl thiol to produce the compound. In one aspect, the alkyl thiol is a C10 to C20 alkyl thiol such as, for example, dodecanethiol. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of an alkyl thiol. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the sulfide compounds described herein.

[0042] In one aspect, the compounds described herein are phosphides (i.e., X is P). In one aspect, the phosphide is produced by heating the Prussian blue analog under an inert atmosphere with an alkyl phosphine to produce the compound. In one aspect, the alkyl phosphine is a trialkyl phosphine, wherein each alkyl group is a C5 to C15 alkyl group. In one aspect, the trialkyl phosphine is trioctyl phosphine. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of an alkyl phosphine. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the phosphide compounds described herein.

[0043] In one aspect, the compounds described herein are oxides(i.e., X is O). In one aspect, the oxide is produced by heating the Prussian blue analog in the presence of oxygen (e.g., open air) to produce the compound. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of air. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the oxide compounds described herein.

[0044] In one aspect, the compounds described herein are an alloy (i.e., X is not present). In one aspect, the oxide is produced by heating the Prussian blue analog or any of the compounds described herein where X is present for a sufficient time and temperature such that the remaining compound only includes metallic elements. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC).

[0045] In one aspect, the compounds described herein, are nitrides (i.e., X is N). In one aspect, the nitride is produced by heating the Prussian blue analog under an inert atmosphere with a nitrogenous compound to produce the compound. In one aspect, the nitrogenous compound is urea or ammonia. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of a nitrogenous compound. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the nitride compounds described herein.

[0046] In one aspect, the compounds described herein, are selenides (i.e., X is Se). In one aspect, the selenide is produced by heating the Prussian blue analog under an inert atmosphere with an organoselenium compound to produce the compound. In one aspect, the organoselenium compound is diphenyl diselenide. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of diphenyl diselenide. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the nitride compounds described herein.

[0047] In one aspect, the compounds described herein, are tellurides (i.e., X is Te). In one aspect, the telluride is produced by heating the Prussian blue analog under an inert atmosphere with an organotellurium compound to produce the compound. In one aspect, the organotellurium compound is diphenyl ditelluride. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of diphenyl ditelluride. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the nitride compounds described herein.

[0048] In one aspect, the compounds described herein, are arsenides (i.e., X is As). In one aspect, the arsenide is produced by heating the Prussian blue analog under an inert atmosphere with an organoarsenide compound to produce the material. In one aspect, the organoarsenide compound is lithium arsanylalanate. In one aspect, Prussian blue analog is heated at a temperature of from about 250 oC to about 500 oC in the presence of lithium arsanylalanate. In another aspect, PBA is heated at a temperature at about 250 oC, 300 oC, 350 oC, 400 oC, 450 oC, or 500 oC, where any value can be a lower and upper endpoint of a range (e.g., 250 oC to 300 oC). The Examples provide non-limiting procedures for making and isolating the nitride compounds described herein.

[0049] In one aspect, the multimetallic compound has the following structure: CrMnX, CrFeX, CrCoX, CrNiX, CrCuX, CrZnX, MnFeX, MnCoX, MnNiX, MnCuX, MnZnX, FeCoX, FeCuX, FeZnX, CoNiX, CoCuX, CoZnX, NiCuX, CuZnX, CrMnFeX, CrMnCoX, CrMnNiX, CrMnCuX, CrMnZXn, CrFeCoX, CrFeNiX, CrFeCuX, CrFeCuX, CrFeZnX, CrCoNiX, CrCoCuX, CrCoZnX, CrNiCuX, CrNiZnX, CrCuZnX, MnFeCoX, MnFeNiX, MnFeCuX, MnFeZnX, MnCoNiX, MnCoCuX, MnCoZnX, MnNiCuX, MnNiZnX, MnCuZnX, FeCoCuX, FeCoZnX, CoNiCuX, CoNiZnX, NiCuZnX, CrMnFeCoX, CrMnFeNiX, CrMnFeCoX, CrMnFeCuX, CrMnFeZnX, CrMnCoNiX, CrMnCoCuX, CrMnCoZnX, CrMnNiCuX, CrMnNiZnX, CrMnCuZnX, CrFeCoNiX, CrFeCoCuX, CrFeCoZnX, CrFeNiCuX, CrFeNiZnX, CrCoNiCuX, CrCoNiZnX, CrNiCuZnX, MnFeCoNiX, MnFeCoCuX, MnFeCoZnX, MnFeNiCuX, MnFeNiZnX, MnCoNiCuX, MnCoNiZnX, MnNiCuZnX, FeCoNiCuX, FeCoNiZnX, CoNiCuZnX, CrMnFeCoNiX, CrMnFeCoCuX, CrMnFeCoZnX, CrMnFeNiCuX, CrMnFeNiZnX, CrMnCoNiCuX, CrMnCoNiZnX, CrFeCoNiCuX, CrFeCoNiZnX, CrCoNiCuZnX, MnFeCoNiCuX, MnFeCoNiZnX, FeCoNiCuZnX, CrMnFeCoNiCuX, CrMnFeCoNiZnX, CrFeCoNiCuZnX, CrMnCoNiCuZnX, CrMnFeNiCuZnX, MnFeCoNiCuZnX, or CrMnFeCoNiCuZnX, where X is absent or C, O, S, P, N, Te, Se, or As.

[0050] The multimetallic compounds described herein possess several properties that make them suitable for the oxygen evolution reaction (OER). In one aspect, the compounds have an overpotential of from about 0.35 V to about 0.40 V at 1 mA cm-2, or about 0.35 V, 0.36 V, 0.37 V, 0.38 V, 0.39 V, or 0.40 V, where any value can be a lower and upper endpoint of a range (e.g., 0.36 V to 0.39 V). In another aspect, the compounds described herein have a particle size from about 5 nm to about 100 nm.

[0051] In certain aspects, mixtures of two or more different multimetallic compounds described herein, which is referred to herein as a composite, can be produced and used in any of the applications described herein. Depending upon the application of the compounds, the selection and amount of each compound used to produce the composite can vary. The compounds can be mixed using techniques known in the art.

[0052] The multimetallic compounds described herein have enhanced thermal stability and electrical conductivity, making them useful in numerous applications. In one aspect, the compounds described herein can be used in energy storage and conversion applications such as, for example, electrodes in batteries and supercapacitors, where the compounds can enhance energy density and cycling stability. In another aspect, the compounds described herein can be used as catalysts for reactions such as, for example, hydrogen evolution and oxygen reduction, which can benefit chemical manufacturing and environmental remediation. In another aspect, compounds described herein can be used in electronics and spintronics, where the compounds possess unique electronic and magnetic properties for use in data storage, sensors, and spintronic devices. In another aspect, the compounds described herein can be used in aerospace and defense applications, where the compounds possess thermal stability and corrosion resistance and are ideal for components exposed to extreme environments. In another aspect, the compounds described herein can be used in healthcare applications such as, for example, medical implants and diagnostic devices.

[0053] In one aspect, the compounds described herein can be applied to one or more electrodes employed in an oxygen evolution system. Examples of these systems include, but are not limited to, water electrolysis systems, solar fuels generators, electrowinning systems, electrolytic hydrogen generators, reversible fuel cells, and reversible air batteries.  The compounds can be deposited or applied to the electrode surface using techniques known in the art. In one aspect, a solution of the compound can be prepared and the electrode can be inserted into the solution. Aspects

[0054] The present disclosure can be described in accordance with the following numbered Aspects, which should not be confused with the claims.

[0055] Aspect 1. A compound having one of the following the formula: ABX, ABCX, ABCDX, ABCDEX, ABCDEFX, or ABCDEFGX, wherein

[0056] A, B, C, D, E, F, and G are, independently, Cr, Mn, Fe, Co, Ni, Cu, and Zn, wherein A, B, C, D, E, F, and G are not the same element, and

[0057] X is absent or X is C, O, S, P, N, Te, Se, or As,

[0058] wherein the compound is not FeNiC and FeCoNiC.

[0059] Aspect 2. The compound of Aspect 1, wherein compound has the formula ABX, wherein

[0060] A is Fe and B is Cr, Mn, Co, Ni, Cu, or Zn;

[0061] A is Cr and B is Fe, Mn, Co, Ni, Cu, or Zn;

[0062] A is Mn and B is Cr, Fe, Co, Ni, Cu, or Zn;

[0063] A is Co and B is Cr, Mn, Fe, Ni, Cu, or Zn;

[0064] A is Ni and B is Cr, Mn, Co, Fe, Cu, or Zn; or

[0065] A is Cu and B is Cr, Mn, Co, Ni, Fe, or Zn.

[0066] Aspect 3. The compound of Aspect 1, wherein compound has the formula ABCX, wherein

[0067] A is Fe and B and C are Cr, Mn, Co, Ni, Cu, or Zn;

[0068] A is Cr and B and C are Fe, Mn, Co, Ni, Cu, or Zn;

[0069] A is Mn and B and C are Fe, Cr, Co, Ni, Cu, or Zn;

[0070] A is Fe and B and C are Mn, Cr, Co, Ni, Cu, or Zn;

[0071] A is Ni and B and C are Fe, Cr, Co, Mn, Cu, or Zn; or

[0072] A is Cu and B and C are Cr, Mn, Co, Fe, Ni, or Zn.

[0073] Aspect 4. The compound of Aspect 1, wherein compound has the formula ABCDX, wherein

[0074] A is Fe and B, C, and D are Cr, Mn, Co, Ni, Cu, or Zn;

[0075] A is Cr and B, C, and D are Fe, Mn, Co, Ni, Cu, or Zn;

[0076] A is Mn and B, C, and D are Fe, Cr, Co, Ni, Cu, or Zn;

[0077] A is Fe and B, C, and D are Mn, Cr, Co, Ni, Cu, or Zn;

[0078] A is Ni and B, C, and D are Fe, Cr, Co, Mn, Cu, or Zn; or

[0079] A is Cu and B, C, and D are Cr, Mn, Co, Fe, Ni, or Zn.

[0080] Aspect 5. The compound of Aspect 1, wherein compound has the formula ABCDEX, wherein

[0081] A is Fe and B, C, D, and E are Cr, Mn, Co, Ni, Cu, or Zn;

[0082] A is Cr and B, C, D, and E are Fe, Mn, Co, Ni, Cu, or Zn;

[0083] A is Mn and B, C, D, and E are Fe, Cr, Co, Ni, Cu, or Zn;

[0084] A is Fe and B, C, D, and E are Mn, Cr, Co, Ni, Cu, or Zn;

[0085] A is Ni and B, C, D, and E are Fe, Cr, Co, Mn, Cu, or Zn; or

[0086] A is Cu and B, C, D, and E are Cr, Mn, Co, Fe, Ni, or Zn.

[0087] Aspect 6. The compound of Aspect 5, wherein A is Cr and B is Mn.

[0088] Aspect 7. The compound of Aspect 5, wherein A is Cr, B is Mn, and C is Fe.

[0089] Aspect 8. The compound of Aspect 5, wherein A is Cr, B is Mn, C is Fe, and D is Co.

[0090] Aspect 9. The compound of Aspect 5, wherein A is Cr, B is Mn, C is Fe, D is Co, and E is Ni.

[0091] Aspect 10. The compound of Aspect 1, wherein compound has the formula ABCDEFX, wherein

[0092] A is Fe and B, C, D, E, and F are Cr, Mn, Co, Ni, Cu, or Zn;

[0093] A is Cr and B, C, D, E, and F are Fe, Mn, Co, Ni, Cu, or Zn;

[0094] A is Mn and B, C, D, E, and F are Fe, Cr, Co, Ni, Cu, or Zn;

[0095] A is Fe and B, C, D, E, and F are Mn, Cr, Co, Ni, Cu, or Zn;

[0096] A is Ni and B, C, D, E, and F are Fe, Cr, Co, Mn, Cu, or Zn; or

[0097] A is Cu and B, C, D, E, and F are Cr, Mn, Co, Fe, Ni, or Zn.

[0098] Aspect 11. The compound of Aspect 1, wherein compound has the formula ABCDEFGX, wherein

[0099] A is Fe and B, C, D, E, F, and G are Cr, Mn, Co, Ni, Cu, or Zn;

[0100] A is Cr and B, C, D, E, F, and G are Fe, Mn, Co, Ni, Cu, or Zn;

[0101] A is Mn and B, C, D, E, F, and G are Fe, Cr, Co, Ni, Cu, or Zn;

[0102] A is Fe and B, C, D, E, F, and G are Mn, Cr, Co, Ni, Cu, or Zn;

[0103] A is Ni and B, C, D, E, F, and G are Fe, Cr, Co, Mn, Cu, or Zn; or

[0104] A is Cu and B, C, D, E, F, and G are Cr, Mn, Co, Fe, Ni, or Zn.

[0105] Aspect 12. The compound of any one of Aspects 1 to 11, wherein X is C, O, S, or P.

[0106] Aspect 13. The compound of Aspect 1, wherein the compound has the following structure: CrMnX, CrFeX, CrCoX, CrNiX, CrCuX, CrZnX, MnFeX, MnCoX, MnNiX, MnCuX, MnZnX, FeCoX, FeCuX, FeZnX, CoNXi, CoCuX, CoZnX, NiCuX, CuZnX, CrMnFeX, CrMnCoX, CrMnNiX, CrMnCuX, CrMnZnX, CrFeCoX, CrFeNiX, CrFeCuX, CrFeCuX, CrFeZnX, CrCoNiX, CrCoCuX, CrCoZnX, CrNiCuX, CrNiZnX, CrCuZnX, MnFeCoX, MnFeNiX, MnFeCuX, MnFeZnX, MnCoNiX, MnCoCuX, MnCoZnX, MnNiCuX, MnNiZnX, MnCuZnX, FeCoCuX, FeCoZnX, CoNiCuX, CoNiZnX, NiCuZnX, CrMnFeCoX, CrMnFeNiX, CrMnFeCoX, CrMnFeCuX, CrMnFeZnX, CrMnCoNiX, CrMnCoCuX, CrMnCoZnX, CrMnNiCuX, CrMnNiZnX, CrMnCuZnX, CrFeCoNiX, CrFeCoCuX, CrFeCoZnX, CrFeNiCuX, CrFeNiZnX, CrCoNiCuX, CrCoNiZnX, CrNiCuZnX, MnFeCoNiX, MnFeCoCuX, MnFeCoZnX, MnFeNiCuX, MnFeNiZnX, MnCoNiCuX, MnCoNiZnX, MnNiCuZnX, FeCoNiCuX, FeCoNiZnX, CoNiCuZnX, CrMnFeCoNiX, CrMnFeCoCuX, CrMnFeCoZnX, CrMnFeNiCuX, CrMnFeNiZnX, CrMnCoNiCuX, CrMnCoNiZnX, CrFeCoNiCuX, CrFeCoNiZnX, CrCoNiCuZnX, MnFeCoNiCuX, MnFeCoNiZnX, FeCoNiCuZnX, CrMnFeCoNiCuX, CrMnFeCoNiZnX, CrFeCoNiCuZnX, CrMnCoNiCuZnX, CrMnFeNiCuZnX, MnFeCoNiCuZnX, or CrMnFeCoNiCuZnX.

[0107] Aspect 14. The compound of Aspect 12, wherein X is C, O, S, or P.

[0108] Aspect 15. The compound of any one of Aspects 1 to 14, wherein the molar ratio of A, B, C, D, E, F, and G relative to each element is from about 0.1:1 to about 99:1.

[0109] Aspect 16. The compound of any one of Aspects 1 to 14, wherein the molar ratio of A, B, C, D, E, F, and G relative to each element is from about 0.8:1 to about 1.2:1.

[0110] Aspect 17. The compound of any one of Aspects 1 to 16, wherein when X is C, the compound is produced by the process comprising

[0111] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0112] heating PBA with a solvent comprising an alkyl amine under an inert atmosphere to produce the compound.

[0113] Aspect 18. The compound of Aspect 17, wherein the alkyl amine is a C10 to C20 alkyl amine.

[0114] Aspect 19. The compound of any one of Aspects 1 to 16, wherein when X is S, the compound is produced by the process comprising

[0115] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0116] heating PBA with a solvent comprising an alkyl thiol under an inert atmosphere to produce the compound.

[0117] Aspect 20. The compound of Aspect 19, wherein the alkyl thiol is a C10 to C20 alkyl thiol.

[0118] Aspect 21. The compound of any one of Aspects 1 to 16, wherein when X is P, the compound is produced by the process comprising

[0119] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0120] heating PBA with a solvent comprising an alkyl phosphine under an inert atmosphere to produce the compound.

[0121] Aspect 22. The compound of Aspect 21, wherein the alkyl phosphine is a trialkyl phosphine, wherein each alkyl group is a C5 to C15 alkyl group.

[0122] Aspect 23. The compound of any one of Aspects 17 to 22, wherein in step (b), PBA is heated at a temperature of the boiling point of the solvent.

[0123] Aspect 24. The compound of any one of Aspects 1 to 16, wherein when X is O, the compound is produced by the process comprising

[0124] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0125] heating PBA as a solid to produce the compound.

[0126] Aspect 25. The compound of Aspect 24, wherein in step (b), PBA is heated at a temperature of about 300 oC to about 500 oC.

[0127] Aspect 26. The compound of any one of Aspects 1 to 16, wherein when X is Se, the compound is produced by the process comprising

[0128] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0129] heating PBA with a solvent comprising an organoselenium compound under an inert atmosphere to produce the compound.

[0130] Aspect 27. The compound of any one of Aspects 1 to 16, wherein when X is Te, the compound is produced by the process comprising

[0131] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0132] heating PBA with a solvent comprising an organotellurium compound under an inert atmosphere to produce the compound.

[0133] Aspect 28. The compound of any one of Aspects 1 to 16, wherein when X is Te, the compound is produced by the process comprising

[0134] mixing a salt of A, B, C, D, E, F, and G in water to produce a Prussian blue analog (PBA); and

[0135] heating PBA with a solvent comprising an organoarsenide compound under an inert atmosphere to produce the compound.

[0136] Aspect 29. The compound of any one of Aspects 17 to 28, wherein the salt comprises K3Fe(CN)6, K2Ni(CN)4, K3Cr(CN)6, K3Mn(CN)6, K3Co(CN)6, K2Zn(CN)4, or KCu(CN)2.

[0137] Aspect 30. The compound of any one of Aspects 18 to 27, wherein the Prussian blue analog has the following structure: CrMn, CrFe, CrCo, CrNi, CrCu, CrZn, MnFe, MnCo, MnNi, MnCu, MnZn, FeCo, FeCu, FeZn, CoNi, CoCu, CoZn, NiCu, CuZn, CrMnFe, CrMnCo, CrMnNi, CrMnCu, CrMnZn, CrFeCo, CrFeNi, CrFeCu, CrFeCu, CrFeZn, CrCoNi, CrCoCu, CrCoZn, CrNiCu, CrNiZn, CrCuZn, MnFeCo, MnFeNi, MnFeCu, MnFeZn, MnCoNi, MnCoCu, MnCoZn, MnNiCu, MnNiZn, MnCuZn, FeCoCu, FeCoZn, CoNiCu, CoNiZn, NiCuZn, CrMnFeCo, CrMnFeNi, CrMnFeCo, CrMnFeCu, CrMnFeZn, CrMnCoNi, CrMnCoCu, CrMnCoZn, CrMnNiCu, CrMnNiZn, CrMnCuZn, CrFeCoNi, CrFeCoCu, CrFeCoZn, CrFeNiCu, CrFeNiZn, CrCoNiCu, CrCoNiZn, CrNiCuZn, MnFeCoNi, MnFeCoCu, MnFeCoZn, MnFeNiCu, MnFeNiZn, MnCoNiCu, MnCoNiZn, MnNiCuZn, FeCoNiCu, FeCoNiZn, CoNiCuZn, CrMnFeCoNi, CrMnFeCoCu, CrMnFeCoZn, CrMnFeNiCu, CrMnFeNiZn, CrMnCoNiCu, CrMnCoNiZn, CrFeCoNiCu, CrFeCoNiZn, CrCoNiCuZn, MnFeCoNiCu, MnFeCoNiZn, FeCoNiCuZn, CrMnFeCoNiCu, CrMnFeCoNiZn, CrFeCoNiCuZn, CrMnCoNiCuZn, CrMnFeNiCuZn, MnFeCoNiCuZn, or CrMnFeCoNiCuZn.

[0138] Aspect 31. The compound of any one of Aspects 1-30, wherein the compound has a particle size from about 10 nm to about 100 nm.

[0139] Aspect 32. The compound of any one of Aspects 1-31, wherein the compound has an overpotential of about 0.350 V to about 0.400 V.

[0140] Aspect 33. A composite comprising two or more compounds of any one of Aspects 1-32.

[0141] Aspect 34. An electrode comprising the compound or composite of any one of Aspects 1-33.

[0142] Aspect 35. The electrode of Aspect 34, wherein the compound comprises a film on the surface of the electrode.

[0143] Aspect 36. An oxygen evolution system or a hydrogen evolution system comprising one or more electrodes of Aspects 34 or 35.

[0144] Aspect 37. The system of Aspect 36, wherein the system comprises a water electrolysis system, a solar fuel generator, an electrowinning system, an electrolytic hydrogen generator, a reversible fuel cell, or a reversible air battery.

[0145] Aspect 38. An energy storage device comprising the compound or composite of any one of Aspects 1-33.

[0146] Aspect 39. The use of the compound or composite of any one of Aspects 1-33 as a catalyst.

[0147] Aspect 40. The use of Aspect 39, wherein the catalyst is a electrocatalyst, a photocatalyst, or a catalyst for splitting water.

[0148] Aspect 41. An article comprising at least one surface coated with the compound or composite of any one of Aspects 1-33.EXAMPLES

[0149] Now having described the embodiments of the disclosure, in general, the examples describe some additional embodiments. While embodiments of the present disclosure are described in connection with the example and the corresponding text and figures, there is no intent to limit embodiments of the disclosure to these descriptions. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of embodiments of the present disclosure.EXPERIMENTAL SECTIONSynthesis of High-Entropy Prussian Blue Analogues HEPBAs

[0150] The synthesis of HEPBAs involves combining aqueous solutions of multiple metal salts with a coordinating ligand, such as hexacyanoferrate, under controlled conditions. The resulting precipitate is collected, washed, and dried to obtain the HEPBA precursor. This method allows for precise control over the metal cation ratios, enabling the design of precursors with specific compositions.General synthesis of PBA containing Cr, Mn, Fe, Co, Ni, Zn, or Cu

[0151] All PBA precursors (from monometallic to pentametallic) are synthesized through a precipitation method adapted from Hardy et al. Two solutions are prepared, a 5mM solution of all cyanometallate salts in equimolar ratios which sum to 1 mmol, as well as a 10mM solution of all metal chloride salts in equimolar ratios which sum to 1 mmol with an additional 5 mmol KCl used as a chelating agent for the PBA formation. For monometallic solution one has 1 mmol cyanometallate salt and solution two has 1 mmol of metal chloride salt and 5 mmol of KCl, for equimolar bimetallic there are 0.5 mmol of each cyanometallate salt in solution 1 and 0.5 mmol of metal chloride salts with the added 5 mmol KCl. The same method is used for equimolar trimetallic, tetrametallic, and pentametallic PBAs. Similarly, if a non-equimolar precursor is desired, the relative amounts of cyanometallate and metal chloride salts may be stoichiometrically adjusted to any ratio. We have previously published the FeCo system with varying Fe content from 0 to 100% at 5% increments highlighting the versatility of the synthetic method.2,4 Once solutions are prepared, solution 2 is slowly added to solution 1 and the resultant reaction mixture is stirred at room temperature for at least 2 hours to ensure PBA formation. The reaction mixture is centrifuged, the PBA is collected and then washed thrice with ultrapure H2O. The PBAs are dried at 120 °C for approximately 30 minutes or until completely dry. The PBAs are then characterized by pXRD, SEM, EDX, XRF, SDT, and FT-IR.Specific syntheses of Equimolar Monometallic PBA

[0152] Preparation of Cr PBA Precursors: Two solutions are prepared and combined to form the CrCr PBA through a precipitation reaction: Solution One: 5 mmol KCl, 1 mmol K3Cr(CN)6, 10 mL ultrapure water, and a magnetic stir bar are added to a 100 mL round-bottom flask. Solution Two: 1 mmol CrCl3· 6H2O and 20 mL ultrapure water are added to a 50 mL beaker. Solution two is dropwise added to solution one at a rate of 5 mL / min while stirring vigorously. The reaction solution is stirred for at 18 h, then the precipitate is collected via centrifugation, washed with 30 mL ultrapure water, and dried in a furnace at 120 °C for 30 min or until dry. Characterized using pXRD, SEM, and XRF.

[0153] Preparation of Mn PBA Precursors: Solution One: 5 mmol KCl, 1 mmol K3Mn(CN)6, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine, wash, dry, and characterize as described.

[0154] Preparation of Fe (Prussian Blue) Precursors: Solution One: 5 mmol KCl, 1 mmol K3Fe(CN)6, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine, wash, dry, and characterize as described.

[0155] Preparation of Co PBA Precursors: Solution One: 5 mmol KCl, 1 mmol K3Co(CN)6, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0156] Preparation of Ni PBA Precursors: Solution One: 5 mmol KCl, 1 mmol K2Ni(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol NiCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine, wash, dry, and characterize as described.

[0157] Preparation of Cu PBA Precursors: Solution One: 5 mmol KCl, 1 mmol KCu(CN)2, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine, wash, dry, and characterize as described.

[0158] Preparation of Zn PBA Precursors: Solution One: 5 mmol KCl, 1 mmol K2Zn(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 1 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine, wash, dry, and characterize as described.Specific syntheses of Equimolar Bimetallic PBA

[0159] Preparation of CrMn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol K3Mn(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0160] Preparation of CrFe PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0161] Preparation of CrCo PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0162] Preparation of CrNi PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol K2Ni(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol NiCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0163] Preparation of CrCu PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol KCu(CN)210 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0164] Preparation of CrZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Cr(CN)6, 0.5 mmol K2Zn(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CrCl3· 6H2O, 0.5 mmol ZnCl2and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0165] Preparation of MnFe PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Mn(CN)6, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol MnCl2· 4H2O, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0166] Preparation of MnCo PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Mn(CN)6, 0.5 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol MnCl2· 4H2O, 0.5 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0167] Preparation of MnNi PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Mn(CN)6,0.5 mmol K2Ni(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol MnCl2· 4H2O, 0.5 mmol NiCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0168] Preparation of MnCu PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Mn(CN)6, 0.5 mmol KCu(CN)210 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol MnCl2· 4H2O, 0.5 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0169] Preparation of MnZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Mn(CN)6, 0.5 mmol K2Zn(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol MnCl2· 4H2O, 0.5 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0170] Preparation of FeCo PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K3Co(CN)6, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CoCl2· 6H2O, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0171] Preparation of FeNi PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Ni(CN)4, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol NiCl2, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0172] Preparation of FeCu PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol KCu(CN)2, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CuCl2· 2H2O, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0173] Preparation of FeZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Zn(CN)4, 0.5 mmol K3Fe(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol ZnCl2, 0.5 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0174] Preparation of CoNi PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Ni(CN)4, 0.5 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol NiCl2, 0.5 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0175] Preparation of CoCu PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol KCu(CN)2, 0.5 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol CuCl2· 2H2O, 0.5 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0176] Preparation of CoZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Zn(CN)4, 0.5 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol ZnCl2, 0.5 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0177] Preparation of NiCu PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Ni(CN)4, 0.5 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol NiCl2, 0.5 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0178] Preparation of NiZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol K2Ni(CN)4, 0.5 mmol K2Zn(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol NiCl2, 0.5 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0179] Preparation of CuZn PBA Precursors: Solution One: 5 mmol KCl, 0.5 mmol KCu(CN)2, 0.5 mmol K2Zn(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.5 mmol ZnCl2, 0.5 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Specific syntheses of Equimolar Trimetallic PBA

[0180] Preparation of CrMnFe PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K3Fe(CN)6, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol FeCl2 , and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0181] Preparation of CrMnCo PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K3Co(CN)6, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol CoCl2· 6H2O, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0182] Preparation of CrMnNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0183] Preparation of CrMnCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol CuCl2· 2H2O, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0184] Preparation of CrMnZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol ZnCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0185] Preparation of CrFeCo PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K3Fe(CN)6, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol FeCl2, and 0.33 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0186] Preparation of CrFeNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Fe(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0187] Preparation of CrFeCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Fe(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol FeCl2, and 0.33 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0188] Preparation of CrFeZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3FeCN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol FeCl2, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0189] Preparation of CrCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0190] Preparation of CrCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol CuCl2· 2H2O, and 0.33 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0191] Preparation of CrCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol ZnCl2, and 0.33 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0192] Preparation of CrNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol KCu(CN)210 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0193] Preparation of CrNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0194] Preparation of CrCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Cr(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CrCl3· 6H2O, 0.33 mmol CuCl2· 2H2O, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0195] Preparation of MnFeCo PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol K3Co(CN)6, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol FeCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0196] Preparation of MnFeNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol FeCl2, 0.33 mmol NiCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0197] Preparation of MnFeCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CuCl2· 2H2O, 0.33 mmol FeCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0198] Preparation of MnFeZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol FeCl2, 0.33 mmol ZnCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0199] Preparation of MnCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Co(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0200] Preparation of MnCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Co(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol CuCl2· 2H2O, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0201] Preparation of MnCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Co(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol ZnCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0202] Preparation of MnNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol KCu(CN)2, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CuCl2· 2H2O, 0.33 mmol NiCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0203] Preparation of MnNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K2Zn(CN)4, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol ZnCl2, 0.33 mmol NiCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0204] Preparation of MnCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol KCu(CN)2, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Mn(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CuCl2· 2H2O, 0.33 mmol ZnCl2, and 0.33 mmol MnCl2· 4H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0205] Preparation of FeCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0206] Preparation of FeCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol KCu(CN)2, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CuCl2· 2H2O, 0.33 mmol FeCl2, and 0.33 mmol CoCl2· 6H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0207] Preparation of FeCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Fe(CN)6, 0.33 mmol K2Zn(CN)4, and 0.33 mmol K3Co(CN)610 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol FeCl2, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0208] Preparation of CoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Co(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol KCu(CN)210 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0209] Preparation of CoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol K3Co(CN)6, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CoCl2· 6H2O, 0.33 mmol NiCl2, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0210] Preparation of NiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.33 mmol KCu(CN)2, 0.33 mmol K2Ni(CN)4, and 0.33 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.33 mmol CuCl2· 2H2O, 0.33 mmol NiCl2, and 0.33 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Specific syntheses of Equimolar Tetrametallic PBA

[0211] Preparation of CrMnFeCo PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0212] Preparation of CrMnFeNi PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0213] Preparation of CrMnFeCo PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0214] Preparation of CrMnFeCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K3Fe(CN)6, and 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0215] Preparation of CrMnFeZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0216] Preparation of CrMnCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Ni(CN)4and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol NiCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0217] Preparation of CrMnCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol KCu(CN)2, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol CuCl2· 2H2O, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0218] Preparation of CrMnCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Zn(CN)4, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol ZnCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0219] Preparation of CrMnNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Ni(CN)4, and 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol NiCl2, and 0.25 mmol CuCl2· 2H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0220] Preparation of CrMnNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Ni(CN)4, and 0.25 mmol K2Zn(CN)4 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol NiCl2, and 0.25 mmol ZnCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0221] Preparation of CrMnCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Zn(CN)4, and 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol ZnCl2, and 0.25 mmol CuCl2· 2H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0222] Preparation of CrFeCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol NiCl2, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0223] Preparation of CrFeCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol KCu(CN)2, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol CuCl2· 2H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0224] Preparation of CrFeCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Zn(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol ZnCl2, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0225] Preparation of CrFeNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol CuCl2· 2H2O, 0.25 mmol FeCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0226] Preparation of CrFeNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol ZnCl2, 0.25 mmol FeCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0227] Preparation of CrCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Co(CN)6, and 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol CuCl2· 2H2O, 0.25 mmol CoCl2· 6H2O, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0228] Preparation of CrCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Co(CN)6, and 0.25 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol ZnCl2, 0.25 mmol CoCl2· 6H2O, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0229] Preparation of CrNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Cr(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol KCu(CN)2, and 0.25 mmol K2Zn(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CrCl3· 6H2O, 0.25 mmol ZnCl2, 0.25 mmol CuCl2· 2H2O, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0230] Preparation of MnFeCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol NiCl2, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0231] Preparation of MnFeCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol KCu(CN)2, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CuCl2· 2H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0232] Preparation of MnFeCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol K2Zn(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol ZnCl2, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0233] Preparation of MnFeNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol KCu(CN)2, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K2Ni(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CuCl2· 2H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0234] Preparation of MnFeNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol K2Zn(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K2Ni(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol ZnCl2, 0.25 mmol MnCl2· 4H2O, 0.25 mmol FeCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0235] Preparation of MnCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol KCu(CN)2, 0.25 mmol K3Co(CN)6, and 0.25 mmol K2Ni(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CuCl2· 2H2O, 0.25 mmol MnCl2· 4H2O, 0.25 mmol CoCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0236] Preparation of MnCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)2, 0.25 mmol K2Zn(CN)4, 0.25 mmol K3Co(CN)6, and 0.25 mmol K2Ni(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol ZnCl2, 0.25 mmol MnCl2· 4H2O, 0.25 mmol CoCl2, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0237] Preparation of MnNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Mn(CN)6, 0.25 mmol K2Ni(CN)4, 0.25 mmol KCu(CN)2, and 0.25 mmol K2Zn(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol MnCl2· 4H2O, 0.25 mmol ZnCl2, 0.25 mmol CuCl2· 2H2O, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0238] Preparation of FeCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6, 0.25 mmol KCu(CN)2 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol NiCl2, 0.25 mmol CuCl2· 2H2O, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0239] Preparation of FeCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K2Ni(CN)4, 0.25 mmol K3Fe(CN)6, and 0.25 mmol K3Co(CN)6, 0.25 mmol K2Zn(CN)410 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol NiCl2, 0.25 mmol ZnCl2, 0.25 mmol FeCl2, and 0.25 mmol CoCl2· 6H2O, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0240] Preparation of CoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.25 mmol K3Co(CN)6, 0.25 mmol K2Ni(CN)4, 0.25 mmol KCu(CN)2, and 0.25 mmol K2Zn(CN)4, 10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.25 mmol CoCl2· 6H2O, 0.25 mmol ZnCl2, 0.25 mmol CuCl2· 2H2O, and 0.25 mmol NiCl2, and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Specific syntheses of Equimolar Pentametallic PBA

[0241] Preparation of CrMnFeCoNi PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2,and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0242] Preparation of CrMnFeCoCu PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0243] Preparation of CrMnFeCoZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0244] Preparation of CrMnFeNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol NiCl2, 0.2 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0245] Preparation of CrMnFeNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0246] Preparation of CrMnCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0247] Preparation of CrMnCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol MnCl2· 4H2O, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0248] Preparation of CrFeCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0249] Preparation of CrFeCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0250] Preparation of CrCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Cr(CN)6, 0.2 mmol KCu(CN)2, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol CrCl3· 6H2O, 0.2 mmol CuCl2· 2H2O, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0251] Preparation of MnFeCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0252] Preparation of MnFeCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Mn(CN)6, 0.2 mmol K3Fe(CN)6, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol MnCl2· 4H2O, 0.2 mmol FeCl2, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0253] Preparation of FeCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.2 mmol K3Fe(CN)6, 0.2 mmol KCu(CN)2, 0.2 mmol K3Co(CN)6, 0.2 mmol K2Ni(CN)4, 0.2 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.2 mmol FeCl2, 0.2 mmol CuCl2· 2H2O, 0.2 mmol CoCl2· 6H2O, 0.2 mmol NiCl2, 0.2 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Specific syntheses of Equimolar Hexametallic PBA

[0254] Preparation of CrMnFeCoNiCu PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Cr(CN)6, 0.166 mmol K3Mn(CN)6, 0.166 mmol K3Fe(CN)6, 0.166 mmol K3Co(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CrCl3· 6H2O, 0.166 mmol MnCl2· 4H2O, 0.166 mmol FeCl2, 0.166 mmol CoCl2· 6H2O, 0.166 mmol NiCl2, 0.166 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0255] Preparation of CrMnFeCoNiZn PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Cr(CN)6, 0.166 mmol K3Mn(CN)6, 0.166 mmol K3Fe(CN)6, 0.166 mmol K3Co(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol K2Zn(CN)4,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CrCl3· 6H2O, 0.166 mmol MnCl2· 4H2O, 0.166 mmol FeCl2, 0.166 mmol CoCl2· 6H2O, 0.166 mmol NiCl2, 0.166 mmol ZnCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0256] Preparation of CrFeCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Cr(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol K3Fe(CN)6, 0.166 mmol K3Co(CN)6, 0.166 mmol K2Zn(CN)4, 0.166 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CrCl3· 6H2O, 0.166 mmol ZnCl2, 0.166 mmol FeCl2, 0.166 mmol CoCl2· 6H2O, 0.166 mmol NiCl2, 0.166 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0257] Preparation of CrMnCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Cr(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol K3Mn(CN)6, 0.166 mmol K3Co(CN)6, 0.166 mmol K2Zn(CN)4, 0.166 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CrCl3· 6H2O, 0.166 mmol ZnCl2, 0.166 mmol MnCl2· 4H2O, 0.166 mmol CoCl2· 6H2O, 0.166 mmol NiCl2, 0.166 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0258] Preparation of CrMnFeNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Cr(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol K3Mn(CN)6, 0.166 mmol K3Fe(CN)6, 0.166 mmol K2Zn(CN)4, 0.166 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CrCl3· 6H2O, 0.166 mmol ZnCl2, 0.166 mmol MnCl2· 4H2O, 0.166 mmol FeCl2, 0.166 mmol NiCl2, 0.166 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.

[0259] Preparation of MnFeCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.166 mmol K3Mn(CN)6, 0.166 mmol K2Ni(CN)4, 0.166 mmol K3Co(CN)6, 0.166 mmol K3Fe(CN)6, 0.166 mmol K2Zn(CN)4, 0.166 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.166 mmol CoCl2· 6H2O, 0.166 mmol ZnCl2, 0.166 mmol MnCl2· 4H2O, 0.166 mmol FeCl2, 0.166 mmol NiCl2, 0.166 mmol CuCl2· 2H2O and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Specific syntheses of Equimolar Heptametallic PBA

[0260] Preparation of CrMnFeCoNiCuZn PBA Precursors: Solution One: 5 mmol KCl, 0.143 mmol K3Cr(CN)6, 0.143 mmol K3Mn(CN)6, 0.143 mmol K3Co(CN)6, 0.143 mmol K3Fe(CN)6, 0.143 mmol K2Ni(CN)4, 0.143 mmol KCu(CN)2,10 mL ultrapure water, and a magnetic stir bar in a 100 mL round-bottom flask. Solution Two: 0.143 mmol K3Co(CN)6,0.143 mmol CoCl2, 0.143 mmol FeCl2 and 20 mL ultrapure water in a 50 mL beaker. Combine as described above, ensuring thorough washing and drying. Characterization methods remain the same.Conversion to High-Entropy Ceramic Nanomaterials

[0261] The HEPBA precursors are subjected to thermal treatment under an inert or reactive atmosphere, depending on the desired ceramic phase. For example, annealing under nitrogen can yield high-entropy nitrides, while sulfurization processes can produce high-entropy sulfides. The thermal decomposition of the HEPBA framework facilitates the formation of homogeneous, multi-element ceramic nanomaterials.

[0262] General Synthesis of Nanocarbides: All nanocarbides (from monometallic to pentametallic) are synthesized through a high temperature organic synthesis method. In summary, 200mg of the PBA precursor and 17.24g (20mL) of octadecylamine are added to a three-neck round bottom flask equipped with a condenser. Under inert atmosphere the reaction mixture is heated to 350°C (BP of octadecylamine) for an hour and subsequently quenched with toluene. The resultant reaction mixture is centrifuged (hot ~ 150°C), the pellet is then washed thrice with toluene, once with acetone, thrice with ultrapure H2O, and once more with acetone. The resultant nanocarbides are dried @ 100°C for approximately 15 minutes or until dry. The nanocarbides are characterized by pXRD, XRF, SDT, and TEM.

[0263] General Synthesis of Nano-oxides: All nano-oxides (from monometallic to pentametallic) are synthesized through a solid-state decomposition reaction. Briefly, 200mg of the PBA precursor is loaded into a quartz boat and then into a tube furnace, open to air on both sides. The tube furnace is closed and heated up to 350°C for 10 minutes and subsequently cooled to room temperature. The nano-oxides are characterized by pXRD, XRF, SDT, and TEM.

[0264] General Synthesis of Nanosulfides: All nanosulfides (from monometallic to pentametallic) are synthesized through a high temperature organic synthesis method. In summary, 200mg of the PBA precursor and 20mL of dodecanethiol are added to a three-neck round bottom flask equipped with a condenser. Under inert atmosphere the reaction mixture is heated to 270°C (BP of dodecanethiol) for an hour and subsequently quenched with toluene. The resultant reaction mixture is centrifuged, the pellet is then washed thrice with toluene, once with acetone, thrice with ultrapure H2O, and once more with acetone. The resultant nanosulfides are dried @ 100°C for approximately 15 minutes or until dry. The nanosulfides are characterized by pXRD, XRF, SDT, and TEM.

[0265] General Synthesis of Nanophosphides: All nanophosphides (from monometallic to pentametallic) are synthesized through a high temperature organic synthesis method. In summary, 200mg of the PBA precursor and 20mL of trioctylphosphine are added to a three-neck round bottom flask equipped with a condenser. Under inert atmosphere the reaction mixture is heated to 270°C (BP of trioctylphosphine) for an hour and subsequently quenched with toluene. The resultant reaction mixture is centrifuged, the pellet is then washed thrice with toluene, once with acetone, thrice with ultrapure H2O, and once more with acetone. The resultant nanophosphides are dried @ 100°C for approximately 15 minutes or until dry. The nanophosphides are characterized by pXRD, XRF, SDT, and TEM.

[0266] Materials Characterization. pXRD patterns of PBAs and PBA derived nanomaterials were collected at room temperature on a Rigaku Miniflex powder diffractometer (Cu Ka source, A= 1.54 Å). Elemental ratios in both PBA and nanomaterials were confirmed using XRF on a Panalytical Epsilon XRF analyzer (Cu Ka source). Size, morphology, and elemental distribution of PBA precursors were investigated using SEM imaging on a Jeoul (15 keV, ) equipped with an energy dispersive x-ray spectrometer (EDX). Size, size dispersity, and morphology of the PBAs and nanomaterials were estimated using ImageJ software (sample size = 100 particles) using SEM andTEM images (collected on a Tecnai Osiris TEM, 200 kV). Scanning differential calorimetry was used to interrogate the thermal stability of PBA and nanocarbide materials, collected on a TA instruments Q600 ramp rate 10°C / min up to 700°C

[0267] Electrode Preparation. A catalyst slurry was prepared using 1mg of catalyst powder and 1mL of methanol. The slurry was sonicated until homogenized ~ 1 minute and then the suspension was dropcasted onto the carbon working electrode (5 mm x 4 mm) of a Pine instruments screen printed electrode (SPE). The mass loading onto the surface of the electrode is approximately 0.2 mg / cm2. The electrodes were dried at room temperature for about 30 minutes before electrochemical measurements were performed.

[0268] Electrochemical Measurements. All electrochemical measurements were performed using a Pine research 3 electrode screen printed electrode system, connected to a CH 660E potentiostat. The SPEs contain a carbon working and counter electrode as well as a Ag / AgCl reference electrode. For OER measurements, 1M KOH electrolyte was used and for HER, 1M H2SO4 electrolyte was used. All potentials were converted to the reversible hydrogen electrode potential using the Evs. RHE = Evs. Ag / AgCl + 1.009 V. The potentials vs RHE were then used to calculate the overpotentials for OER using η = Evs. RHE -1.23 V.RESULTS AND DISCUSSION

[0269] Monometallic PBA – Derived M-Xides. Several monometallic MX-ides were synthesized using our PBA thermal decomposition method. The motivation behind synthesizing these monometallic materials is to gain insight on pure phase compositions that can be used as a building block for fitting more complex systems. FIG. 1 shows the pXRD results of cobalt PBA - derived sulfide which matches the Co9S8 crystal phase. The reference pattern from the crystallography open database for the Co9S8 crystal phase is shown below as blue bars. The XRF results from this sample show less than 1% impurities. The sulfide was synthesized by boiling the Co PBA in dodecanethiol for an hour. The pXRD results for the synthesized cobalt and nickel PBA – derived monometallic phosphides are shown in FIG. 2. The cobalt PBA – derived phosphide matches the CoP crystal phase and the nickel PBA – derived phosphide matched to the Ni2P crystal phase. The XRF results also indicate less than 1% impurities for both materials. The phosphides were synthesized by boiling each PBA in trioctylphosphine for an hour. The pXRD results for the PBA – derived monometallic oxides are shown in FIG. 3. The iron variant produced the Fe3O4 crystal phase, the cobalt variant produced the Co3O4 crystal phase, and the nickel variant produced the NiO2 crystal phase. The iron and cobalt were both pure phase materials, however the nickel variant has an impurity phase of the FeNi3 alloy. The oxides were synthesized via a solid-state route by heating each PBA to 350°C, held at temperature for 10 minutes, and cooling back to room temperature. We believe the isolation of the FeNi3 impurity is due to the lack of solvent present in this method. Our previous work has shown that solvent influences the thermodynamic barrier for the formation of alloy.163 The XRF values also show less than 1% impurities in the oxide materials.

[0270] Bimetallic PBA – Derived M-Xides. Several bimetallic MX-ides were synthesized using our PBA thermal decomposition method. The motivation behind synthesizing these bimetallic materials was to gain insight on the dependence of phase on metal compositions. The materials were synthesized in the same manner as the monometallic materials. The pXRD of bimetallic FeCo and FeNi phosphides are shown in FIG. 4. The results show that 95% Fe FeCo produces a mixture of iron and cobalt phosphide phases with the major phase being Fe2P and minor phase CoP. When the amount of Fe decreases to 60% the only phosphide phase isolated is CoP, however this sample is contaminated with a minor amount of Co3O4. Notably, as the amount of Fe is further decreased, a new FeP phase is isolated rather than the maintenance of the CoP phase.

[0271] There was an oxide impurity in this sample as well. Which is not surprising based on literature reports of phosphides being prone to oxidation under ambient conditions. The XRF results show the maintenance of metal ratios from PBA to phosphide, similar to carbide results. This suggests that PBA is a practical precursor for the synthesis of ratio controlled phosphides, which also agrees with results in literature. FIG. 5 shows the pXRD results for the 15% Fe FeCo, 15 % Fe FeNi and 65% Fe FeNi PBA – derived oxides. The 15% Fe FeCo oxide matches the Co3O4 phase, the 15% Fe FeNi primarily matches the NiO2 phase and the 65% Fe FeNi has a mixed oxide composition of Fe3O4 and Fe2O3.

[0272] Pentametallic PBA – Derived M-Xides. Pentametallic materials were synthesized as previously stated. FIG. 6 shows the pXRD results of each pentametallic material synthesized. The pentametallic carbide (CrMnFeCoNiC) reveals a mixed carbide containing the Fe2.4.C and the Ni3C structure types. The pentametallic oxide (CrMnFeCoNiO) produced a mixed oxide containing both MnO2 and Co3O4 structure types. The pentametallic phosphide (CrMnFeCoNiP) produced a mixed phosphide containing both FeP and CoP structure types. The pentametallic sulfide (CrMnFeCoNiS) produced a pure phase sulfide matching the Co3S4 structure type. The pentametallic alloy produced an alloy matching the Fe face centered cubic structure type, however there was a large impurity of MnO in this sample. The oxide impurity was unsurprising as Mn based materials tend to oxidize easily under ambient conditions, and many metal alloys are not air stable as well.

[0273] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations and are set forth only for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure.

Claims

1. A compound having one of the following the formula: ABX, ABCX, ABCDX, ABCDEX, ABCDEFX, or ABCDEFGX, whereinA, B, C, D, E, F, and G are, independently, Cr, Mn, Fe, Co, Ni, Cu, and Zn, wherein A, B, C, D, E, F, and G are not the same element, andX is absent or X is C, O, S, P, N, Te, Se, or As,wherein the compound is not FeNiC and FeCoNiC.

2. The compound of claim 1, wherein compound has the formula ABX, wherein (a) A is Fe and B is Cr, Mn, Co, Ni, Cu, or Zn;(b) A is Cr and B is Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B is Cr, Fe, Co, Ni, Cu, or Zn;(d) A is Co and B is Cr, Mn, Fe, Ni, Cu, or Zn;(e) A is Ni and B is Cr, Mn, Co, Fe, Cu, or Zn; or(f) A is Cu and B is Cr, Mn, Co, Ni, Fe, or Zn.

3. The compound of claim 1, wherein compound has the formula ABCX, wherein (a) A is Fe and B and C are Cr, Mn, Co, Ni, Cu, or Zn;(b) A is Cr and B and C are Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B and C are Fe, Cr, Co, Ni, Cu, or Zn;(d) A is Fe and B and C are Mn, Cr, Co, Ni, Cu, or Zn;(e) A is Ni and B and C are Fe, Cr, Co, Mn, Cu, or Zn; or(f) A is Cu and B and C are Cr, Mn, Co, Fe, Ni, or Zn.

4. The compound of claim 1, wherein compound has the formula ABCDX, wherein (a) A is Fe and B, C, and D are Cr, Mn, Co, Ni, Cu, or Zn;(b) A is Cr and B, C, and D are Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B, C, and D are Fe, Cr, Co, Ni, Cu, or Zn;(d) A is Fe and B, C, and D are Mn, Cr, Co, Ni, Cu, or Zn;(e) A is Ni and B, C, and D are Fe, Cr, Co, Mn, Cu, or Zn; or(f) A is Cu and B, C, and D are Cr, Mn, Co, Fe, Ni, or Zn.

5. The compound of claim 1, wherein compound has the formula ABCDEX, wherein (b) A is Cr and B, C, D, and E are Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B, C, D, and E are Fe, Cr, Co, Ni, Cu, or Zn;(d) A is Fe and B, C, D, and E are Mn, Cr, Co, Ni, Cu, or Zn;(e) A is Ni and B, C, D, and E are Fe, Cr, Co, Mn, Cu, or Zn; or(f) A is Cu and B, C, D, and E are Cr, Mn, Co, Fe, Ni, or Zn.

6. The compound of claim 5, wherein A is Cr and B is Mn.

7. The compound of claim 5, wherein A is Cr, B is Mn, and C is Fe.

8. The compound of claim 5, wherein A is Cr, B is Mn, C is Fe, and D is Co.

9. The compound of claim 5, wherein A is Cr, B is Mn, C is Fe, D is Co, and E is Ni.

10. The compound of claim 1, wherein compound has the formula ABCDEFX, wherein (a) A is Fe and B, C, D, E, and F are Cr, Mn, Co, Ni, Cu, or Zn;(b) A is Cr and B, C, D, E, and F are Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B, C, D, E, and F are Fe, Cr, Co, Ni, Cu, or Zn;(d) A is Fe and B, C, D, E, and F are Mn, Cr, Co, Ni, Cu, or Zn;(e) A is Ni and B, C, D, E, and F are Fe, Cr, Co, Mn, Cu, or Zn; or(f) A is Cu and B, C, D, E, and F are Cr, Mn, Co, Fe, Ni, or Zn.

11. The compound of claim 1, wherein compound has the formula ABCDEFGX, wherein (a) A is Fe and B, C, D, E, F, and G are Cr, Mn, Co, Ni, Cu, or Zn;(b) A is Cr and B, C, D, E, F, and G are Fe, Mn, Co, Ni, Cu, or Zn;(c) A is Mn and B, C, D, E, F, and G are Fe, Cr, Co, Ni, Cu, or Zn;(d) A is Fe and B, C, D, E, F, and G are Mn, Cr, Co, Ni, Cu, or Zn;(e) A is Ni and B, C, D, E, F, and G are Fe, Cr, Co, Mn, Cu, or Zn; or(f) A is Cu and B, C, D, E, F, and G are Cr, Mn, Co, Fe, Ni, or Zn.

12. The compound of claim 1, wherein X is C, O, S, or P.

13. The compound of claim 1, wherein the compound has the following structure: CrMnX, CrFeX, CrCoX, CrNiX, CrCuX, CrZnX, MnFeX, MnCoX, MnNiX, MnCuX, MnZnX, FeCoX, FeCuX, FeZnX, CoNXi, CoCuX, CoZnX, NiCuX, CuZnX, CrMnFeX, CrMnCoX, CrMnNiX, CrMnCuX, CrMnZnX, CrFeCoX, CrFeNiX, CrFeCuX, CrFeCuX, CrFeZnX, CrCoNiX, CrCoCuX, CrCoZnX, CrNiCuX, CrNiZnX, CrCuZnX, MnFeCoX, MnFeNiX, MnFeCuX, MnFeZnX, MnCoNiX, MnCoCuX, MnCoZnX, MnNiCuX, MnNiZnX, MnCuZnX, FeCoCuX, FeCoZnX, CoNiCuX, CoNiZnX, NiCuZnX, CrMnFeCoX, CrMnFeNiX, CrMnFeCoX, CrMnFeCuX, CrMnFeZnX, CrMnCoNiX, CrMnCoCuX, CrMnCoZnX, CrMnNiCuX, CrMnNiZnX, CrMnCuZnX, CrFeCoNiX, CrFeCoCuX, CrFeCoZnX, CrFeNiCuX, CrFeNiZnX, CrCoNiCuX, CrCoNiZnX, CrNiCuZnX, MnFeCoNiX, MnFeCoCuX, MnFeCoZnX, MnFeNiCuX, MnFeNiZnX, MnCoNiCuX, MnCoNiZnX, MnNiCuZnX, FeCoNiCuX, FeCoNiZnX, CoNiCuZnX, CrMnFeCoNiX, CrMnFeCoCuX, CrMnFeCoZnX, CrMnFeNiCuX, CrMnFeNiZnX, CrMnCoNiCuX, CrMnCoNiZnX, CrFeCoNiCuX, CrFeCoNiZnX, CrCoNiCuZnX, MnFeCoNiCuX, MnFeCoNiZnX, FeCoNiCuZnX, CrMnFeCoNiCuX, CrMnFeCoNiZnX, CrFeCoNiCuZnX, CrMnCoNiCuZnX, CrMnFeNiCuZnX, MnFeCoNiCuZnX, or CrMnFeCoNiCuZnX.

14. The compound of claim 13, wherein X is C, O, S, or P.

15. The compound of claim 1, wherein the molar ratio of A, B, C, D, E, F, and G relative to each element is from about 0.1:1 to about 99:1.

16. The compound of claim 1, wherein the molar ratio of A, B, C, D, E, F, and G relative to each element is from about 0.8:1 to about 1.2:1.

17. A composite comprising two or more compounds of claim 1.

18. An electrode comprising one or more compounds of claim 1.

19. An oxygen evolution system or a hydrogen evolution system comprising one or more electrodes of claim 18.

20. An energy storage device comprising one or more compounds of claim 1.

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