CALCIUM RUTHENATE COMPOSITION OF MATTER AND CALCIUM RUTHENATE CATALYSTS

Abstract

A calcium ruthenate composition of matter includes a compound of calcium, ruthenium and oxygen with a chemical formula of Ca.sub.aRu.sub.bO.sub.c and with ‘a’ greater than or equal to 2.75 and less than or equal to 3.25, ‘b’ greater than or equal to 0.75 and less than or equal to 1.25, and ‘c’ greater than or equal to 5.75 and less than or equal to 6.25. The Ca.sub.aRu.sub.bO.sub.c is an oxygen evolution reaction catalyst, an oxygen reduction reaction catalyst, and/or a catalyst for the hydrolysis of a hydrogen containing compound.

Claims

1. A calcium ruthenate composition of matter comprising: a compound of calcium, ruthenium and oxygen with a chemical formula of Ca.sub.aRu.sub.bO.sub.c, wherein: a is greater than or equal to 2.5 and less than or equal to 3.5; b is greater than or equal to 0.5 and less than or equal to 1.5; and c is greater than or equal to 5.5 and less than or equal to 6.5.

2. The calcium ruthenate composition of matter according to claim 1, wherein: a is greater than or equal to 2.75 and less than or equal to 3.25; b is greater than or equal to 0.75 and less than or equal to 1.25; and c is greater than or equal to 5.75 and less than or equal to 6.25.

3. The calcium ruthenate composition of matter according to claim 1, wherein: a is greater than or equal to 2.8 and less than or equal to 3.2; \b is greater than or equal to 0.8 and less than or equal to 1.2; and c is greater than or equal to 5.8 and less than or equal to 6.2.

4. The calcium ruthenate composition of matter according to claim 1, wherein: a is about 3.0; b is about 1.0; and c is about 6.0.

5. The calcium ruthenate composition of matter according to claim 1, wherein the compound of calcium, ruthenium, and oxygen is an oxygen catalyst.

6. The calcium ruthenate composition of matter according to claim 5, wherein the compound of calcium, ruthenium, and oxygen is an oxygen evolution reaction catalyst.

7. The calcium ruthenate composition of matter according to claim 5, wherein the compound of calcium, ruthenium, and oxygen is an oxygen reduction reaction catalyst.

8. The calcium ruthenate composition of matter according to claim 5, wherein the compound of calcium, ruthenium, and oxygen is a catalyst for hydrolysis of a hydrogen containing compound.

9. The calcium ruthenate composition of matter according to claim 5 further comprising a catalyst support, wherein the compound of calcium, ruthenium, and oxygen is bonded to a surface of the catalyst support.

10. The calcium ruthenate composition of matter according to claim 9, wherein the compound of calcium, ruthenium, and oxygen comprises particles of Ca.sub.aRu.sub.bO.sub.c bonded to the surface of the catalyst support.

11. The calcium ruthenate composition of matter according to claim 10, wherein the particles of Ca.sub.aRu.sub.bO.sub.c comprise at least one of microparticles of Ca.sub.aRu.sub.bO.sub.c and nanoparticles of Ca.sub.aRu.sub.bO.sub.c.

12. The calcium ruthenate composition of matter according to claim 10, wherein the particles of Ca.sub.aRu.sub.bO.sub.c comprise amorphous Ca.sub.aRu.sub.bO.sub.c.

13. The calcium ruthenate composition of matter according to claim 9, wherein the compound of calcium, ruthenium, and oxygen comprises a sputtered layer of Ca.sub.aRu.sub.bO.sub.c.

14. The calcium ruthenate composition of matter according to claim 13, wherein the sputtered layer of Ca.sub.aRu.sub.bO.sub.c comprises amorphous Ca.sub.aRu.sub.bO.sub.c.

15. A catalyst comprising: a compound of calcium, ruthenium and oxygen with a chemical formula of Ca.sub.aRu.sub.bO.sub.c, wherein: a is greater than or equal to 2.5 and less than or equal to 3.5; b is greater than or equal to 0.5 and less than or equal to 1.5; and c is greater than or equal to 5.5 and less than or equal to 6.5.

16. The catalyst according to claim 15 further comprising a catalyst support, wherein the compound of calcium, ruthenium and oxygen is bonded to a surface of the catalyst support.

17. The catalyst according to claim 16, wherein: a is greater than or equal to 2.75 and less than or equal to 3.25; b is greater than or equal to 0.75 and less than or equal to 1.25; and c is greater than or equal to 5.75 and less than or equal to 6.25.

18. The catalyst according to claim 17, wherein the compound of calcium, ruthenium and oxygen bonded to the surface of the catalyst support is at least one of microparticles of Ca.sub.aRu.sub.bO.sub.c, nanoparticles of Ca.sub.aRu.sub.bO.sub.c, a sputtered layer of Ca.sub.aRu.sub.bO.sub.c, and amorphous Ca.sub.aRu.sub.bO.sub.c.

19. A catalyst comprising: a catalyst support and a compound of calcium, ruthenium and oxygen disposed on a surface of the catalyst support, wherein the compound of calcium, ruthenium and oxygen is bonded to a surface of the catalyst support and has a chemical formula of Ca.sub.aRu.sub.bO.sub.c with ‘a’ greater than or equal to 2.5 and less than or equal to 3.5, ‘b’ greater than or equal to 0.5 and less than or equal to 1.5, and ‘c’ greater than or equal to 5.5 and less than or equal to 6.5.

20. The catalyst according to claim 19, wherein: a is greater than or equal to 2.85 and less than or equal to 3.15; b is greater than or equal to 0.85 and less than or equal to 1.15; c is greater than or equal to 5.85 and less than or equal to 6.15; and the compound of calcium, ruthenium and oxygen bonded to the surface of the catalyst support is at least one of microparticles of Ca.sub.aRu.sub.bO.sub.c, nanoparticles of Ca.sub.aRu.sub.bO.sub.c, a sputtered layer of Ca.sub.aRu.sub.bO.sub.c, and amorphous Ca.sub.aRu.sub.bO.sub.c.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0011] FIG. 1 shows a crystal structure model for the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0012] FIG. 2 is an x-ray diffraction (XRD) pattern of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0013] FIG. 3 is an image of XRD scans as a function of temperature for the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0014] FIG. 4 is a flow chart for a method of making the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0015] FIG. 5 is a flow chart for another method of making the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0016] FIG. 6 is a flow chart for still another method of making the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure;

[0017] FIG. 7A shows a technique for applying the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure to a catalyst support;

[0018] FIG. 7B shows another technique for applying the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure to a catalyst support;

[0019] FIG. 8A shows the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure being used as an oxygen evolution reaction (OER) catalyst;

[0020] FIG. 8B shows the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure being used as an oxygen reduction reaction (ORR) catalyst; and

[0021] FIG. 8C shows the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure being used a catalyst for cracking ammonia.

DETAILED DESCRIPTION

[0022] The present disclosure provides a calcium ruthenate composition of matter (calcium ruthenate). The calcium ruthenate has a chemical formula of Ca.sub.aRu.sub.bO.sub.c with the ‘a’ coefficient being greater than or equal to 2.5 and less than or equal to 3.5 (i.e., 2.5 ≤ a ≤ 3.5), the ‘b’ coefficient being greater than or equal to 0.5 and less than or equal to 1.5 (i.e., 0.5 ≤ b ≤ 1.5), and/or the ‘c’ coefficient being greater than or equal to 5.5 and less than or equal to 6.5 (i.e., 5.5 ≤ c ≤ 6.5). In some variations, ‘a’ is greater than or equal to 2.75 and less than or equal to 3.25, ‘b’ is greater than or equal to 0.75 and less than or equal to 1.25, and/or ‘c’ is greater than or equal to 5.75 and less than or equal to 6.25. And in at least one variation ‘a’ is greater than or equal to 2.8 and less than or equal to 3.2, ‘b’ is greater than or equal to 0.8 and less than or equal to 1.2, and/or ‘c’ is greater than or equal to 5.8 and less than or equal to 6.2. In such variations, ‘a’ can be greater than or equal to 2.85 and less than or equal to 3.15, ‘b’ can be greater than or equal to 0.85 and less than or equal to 1.15, and/or ‘c’ can be greater than or equal to 5.85 and less than or equal to 6.15. In at least one variation ‘a’ is about 3.0, ‘b’ is about 1.0, and/or ‘c’ is about 6.0.

[0023] The calcium ruthenate Ca.sub.aRu.sub.bO.sub.c can be used as an OER catalyst, for example, to enhance water electrolysis. In the alternative, or in addition to, the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c can be used as an ORR catalyst, for example, to enhance hydrogen fuel cell operation. And in another alternative, or in addition to, the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c can be used as a catalyst for the hydrolysis of hydrogen storing materials such as ammonia and ammonia borane, among others, to enhance to production of molecular hydrogen. The calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure was predicted using an agent-based sequential optimization approach to materials discovery as taught in Montoya, J. H., Winther, K. T., Flores, R. A., Bligaard, T., Hummelshøj, J. S., & Aykol, M. (2020), “Autonomous intelligent agents for accelerated materials discovery”, Chemical Science, 11(32), 8517-8532. In addition, the previously unknown compound (i.e., the Ca.sub.aRu.sub.bO.sub.c) was synthesized and formed as described in greater detail below. Not being bound by theory, it should be understood that the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c exhibits enhanced catalytic activity at least in part due to the presence of Ru, and given the Ca rich composition of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c compared to other Ru-containing catalytic materials (e.g., Ca.sub.3Ru.sub.2O.sub.7, CaRuO.sub.3, SrRuO.sub.3, Ca.sub.2LaRuO.sub.6, SrCoRuO.sub.6, and SrLaCoRuO.sub.6), the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure requires less Ru per gram of material and thus can cost less than other Ru-containing catalytic materials.

[0024] Referring to FIG. 1, a crystal structure model for the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is shown. The polygons ‘Ca’ represent a calcium atom (i.e., a calcium atom is at the center of each of the heavily shaded polygons identified as ‘Ca’), the polygons ‘Ru’ represent a ruthenium atom (i.e., a ruthenium atom is at the center of each of the lightly shaded polygons identified as ‘Ru’)), and the spheres represent oxygen atoms. The crystal structure is monoclinic.

[0025] Referring to FIG. 2 an XRD plot ‘A’ of powders comprising the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure is shown. In addition, FIG. 2 shows simulated XRD patterns generated from published crystallographic data for CaRuO.sub.3, CaCO.sub.3, and CaO, and calculated XRD peaks for Ca.sub.3RuO.sub.6 with a trigonal crystal structure, Ca.sub.3RuO.sub.6 with a monoclinic crystal structure, and Ca.sub.2RuO.sub.4 with an orthorhombic crystal structure. And as observed from comparing the XRD plot A with the known and calculated XRD peaks listed above, Ca.sub.3RuO.sub.6 with a monoclinic crystal structure was present in the powders.

[0026] Referring now to FIG. 3, additional confirmation of the presence of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure is shown. Particularly, FIG. 3 shows an image of XRD scans of precursor metal carbonate and/or oxide powders (precursor powders) as the precursor powders were heated from room temperature (about 22° C.) to 1100° C. and then cooled from 1100° C. to room temperature. Non-limiting examples of the precursor metal carbonate and oxide powders include RuO.sub.2, CaRuO.sub.3, CaCO.sub.3, CaO.sub.2, and CaO. For example, in some variations the precursor powders include RuO.sub.2 and CaCO.sub.3. And as observed by comparing FIGS. 2 and 3, the XRD peak for Ca.sub.3RuO.sub.6 at about 32-33° occurs or appears when the precursor powders reach about 800° C. and disappear when the precursor powders reach about 1100° C. Accordingly, it should be understood that in some variations of the present disclosure the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is formed by heating an appropriate mixture of metal carbonate and oxide powders to between about 800° C. and about 1000° C.

[0027] Referring now to FIGS. 4-6, flow charts for non-limiting examples of methods for making the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure are shown. In FIG. 4, a method 10 includes mixing precursor components at 100 and forming the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c via precipitation at 110. For example, appropriate metal salts are mixed with or dissolved in water to form a metal salt aqueous solution at 100 and the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is precipitated out of the solution by adding a precipitation agent (e.g., potassium hydroxide (KOH)) to the solution at 110. In some variations, precipitated particles of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c are disposed on and/or bonded to a surface of a catalyst support as described below. In FIG. 5, method 12 includes mixing or dissolving appropriate metal salts in water to form a metal salt aqueous solution at 100 and using the metal salt aqueous solution with the incipient wetness impregnation technique at 112 to deposit the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c within a porous catalyst support. And in FIG. 6, method 14 includes mixing powders of appropriate metal carbonates and/or oxides at 100 and heating the mixed powders at 114 such that bulk solid-state reactions result in the formation of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c. As mentioned above, non-limiting examples of the precursor metal carbonate and oxide powders include RuO.sub.2, CaRuO.sub.3, CaCO.sub.3, CaO.sub.2, and CaO. For example, and as mentioned above, in some variations the precursor powders were RuO.sub.2 and CaCO.sub.3, and in at least one variation, powders of RuO2 and CaCO3 with a molar ratio of 1:3 are mixed and heated such that bulk solid-state reactions result in the formation of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c.

[0028] In some variations the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is in the form of microparticles, while in other variations the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is in the form of nanoparticles. And in at least one variation the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c is the form of microparticles and nanoparticles. As used herein, the term “microparticles” refers to particles with an average outer dimension between 1 micrometer (.Math.m) and 999 .Math.m and the term “nanoparticles” refers to particles with an average outer dimension between 1 nanometer (nm) and 999 nm.

[0029] Referring to FIGS. 7A and 7B, two non-limiting examples of providing or forming a layer of the calcium ruthenate Ca.sub.aRu.sub.bO.sub.c according to the teachings of the present disclosure onto a surface of a substrate or support are shown. Particularly, in some variations particles 130 of Ca.sub.aRu.sub.bO.sub.c are used to form a layer 132 of the Ca.sub.aRu.sub.bO.sub.c on a surface 122 of a catalyst support 120 (FIG. 7A), while in other variations a Ca.sub.aRu.sub.bO.sub.c target 140 is used for sputtering and forming a layer 142 of the Ca.sub.aRu.sub.bO.sub.c on the surface 122 of the catalyst support 120 (FIG. 7B). In at least one variation, the layer 132 of the Ca.sub.aRu.sub.bO.sub.c on the surface 122 of the catalyst support 120 is a continuous layer, while in other variations the layer 132 of the Ca.sub.aRu.sub.bO.sub.c on the surface 122 of the catalyst support 120 is a non-continuous layer. Also, in some variations the layer 142 of the Ca.sub.aRu.sub.bO.sub.c on the surface 122 of the catalyst support 120 is a continuous layer, while in other variations the layer 142 of the Ca.sub.aRu.sub.bO.sub.c on the surface 122 of the catalyst support 120 is a non-continuous layer. As used herein, the term “continuous layer” refers to a layer providing complete coverage of a surface (i.e., 100% coverage) and the term “non-continuous layer” refers to a layer providing only partial coverage of a surface (i.e., < 100% coverage). In addition, in at least one variation the layer 132 and/or the layer 142 of the Ca.sub.aRu.sub.bO.sub.c includes amorphous Ca.sub.aRu.sub.bO.sub.c.

[0030] Referring to FIG. 8A, in some variations the Ca.sub.aRu.sub.bO.sub.c is used as an OER catalyst, e.g., for catalyzing hydroxide ions (OH.sup.-) to form molecular oxygen (O.sub.2) and water (H2O). In the alternative, or in addition to, the Ca.sub.aRu.sub.bO.sub.c is used as an ORR catalyst, e.g., for catalyzing molecular oxygen and hydrogen ions (H.sup.+) to form water as shown in FIG. 8B. And in the alternative, or in addition to, the Ca.sub.aRu.sub.bO.sub.c is used as a hydrolysis catalyst for the catalytic decomposition of ammonia as shown in FIG. 8C and/or the catalytic hydrolysis of other hydrogen storage materials.

[0031] Not being bound by theory, and with respect to Ca.sub.aRu.sub.bO.sub.c being used as an OER catalyst (FIG. 8A), in some variations the crystalline symmetry of the Ca.sub.aRu.sub.bO.sub.c and/or the electronic structure of the Ca.sub.aRu.sub.bO.sub.c, provide enhanced OER activity. For example, in some variations the Ca.sub.aRu.sub.bO.sub.c is a strongly correlated material with an incompletely filled d- orf-electron shell such that an increase in the unoccupied d- or ƒ-electron shell(s) results in crystallographic structure change that decreases the overpotential for the oxygen evolution reaction. Stated differently, and as a non-limiting example, electrons from OH.sup.- ions transfer to the unoccupied d-or ƒ-electron shell(s) of the Ca.sub.aRu.sub.bO.sub.c, which in turn results in a crystallographic structure change of the material that enhances the OER activity of the Ca.sub.aRu.sub.bO.sub.c.

[0032] Regarding Ca.sub.aRu.sub.bO.sub.c being used as an OER catalyst (FIG. 8B), and not being bound by theory, in some variations O.sub.2 activation occurs via electrons from the Ca.sub.aRu.sub.bO.sub.c being transferred directly from the Ca.sub.aRu.sub.bO.sub.c surface to excite the neutral O2 molecule to one of its two singlet states or by charging the O.sub.2 molecule to a superoxide ion

[00001]$\left({\text{O}}_2^{-}\right)$

or a peroxide ion

[00002]$\left({\text{O}}_2^{2-}\right).$

[0033] And regarding Ca.sub.aRu.sub.bO.sub.c being used as an OER catalyst (FIG. 8C), in some variations the Ca.sub.aRu.sub.bO.sub.c assists in cracking of the ammonia to form nitrogen gas and hydrogen gas.

[0034] It should be understood from the teachings of the present disclosure that a new calcium ruthenate composition of matter is provided. The calcium ruthenate has a chemical formula of Ca.sub.aRu.sub.bO.sub.c and the ‘a’ coefficient is greater than or equal to 2.5 and less than or equal to 3.5 (i.e., 2.5 ≤a ≤3.5), for example, greater than or equal to 2.75 and less than or equal to 3.25, greater than or equal to 2.8 and less than or equal to 3.2, or greater than or equal to 2.85 and less than or equal to 3.15. In at least one variation ‘a’ is about 3.0. The ‘b’ coefficient is greater than or equal to 0.5 and less than or equal to 1.5 (i.e., 0.5 ≤b ≤1.5), for example, greater than or equal to 0.75 and less than or equal to 1.25, greater than or equal to 0.8 and less than or equal to 1.2, or greater than or equal to 0.85 and less than or equal to 1.15. In at least one variation, ‘b’ is about 1.0. The ‘c’ coefficient is greater than or equal to 5.5 and less than or equal to 6.5 (i.e., 5.5 ≤c ≤ 6.5), for example, greater than or equal to 5.75 and less than or equal to 6.25, greater than or equal to 5.8 and less than or equal to 6.2, or greater than or equal to 5.85 and less than or equal to 6.15. In at least one variation ‘c’ is about 6.0. It should also be understood that in some variations the amounts (concentrations) of Ca, Ru, and O in the calcium ruthenate composition are independent of each other.

[0035] The preceding description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. Work of the presently named inventors, to the extent it may be described in the background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present technology.

[0036] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical “or.” It should be understood that the various steps within a method may be executed in different order without altering the principles of the present disclosure. Disclosure of ranges includes disclosure of all ranges and subdivided ranges within the entire range.

[0037] The headings (such as “Background” and “Summary”) and sub-headings used herein are intended only for general organization of topics within the present disclosure, and are not intended to limit the disclosure of the technology or any aspect thereof. The recitation of multiple variations or forms having stated features is not intended to exclude other variations or forms having additional features, or other variations or forms incorporating different combinations of the stated features.

[0038] As used herein the term “about” when related to numerical values herein refers to known commercial and/or experimental measurement variations or tolerances for the referenced quantity. In some variations, such known commercial and/or experimental measurement tolerances are +/- 10% of the measured value, while in other variations such known commercial and/or experimental measurement tolerances are +/- 5% of the measured value, while in still other variations such known commercial and/or experimental measurement tolerances are +/- 2.5% of the measured value. And in at least one variation, such known commercial and/or experimental measurement tolerances are +/- 1% of the measured value.

[0039] As used herein, the terms “comprise” and “include” and their variants are intended to be non-limiting, such that recitation of items in succession or a list is not to the exclusion of other like items that may also be useful in the devices and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that a form or variation can or may comprise certain elements or features does not exclude other forms or variations of the present technology that do not contain those elements or features.

[0040] The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the specification and the following claims. Reference herein to one variation, or various variations means that a particular feature, structure, or characteristic described in connection with a form or variation or particular system is included in at least one variation or form. The appearances of the phrase “in one variation” (or variations thereof) are not necessarily referring to the same variation or form. It should be also understood that the various method steps discussed herein do not have to be carried out in the same order as depicted, and not each method step is required in each variation or form.

[0041] The foregoing description of the forms and variations has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular form or variation are generally not limited to that particular form or variation, but, where applicable, are interchangeable and can be used in a selected form or variation, even if not specifically shown or described. The same may also be varied in many ways. Such variations should not be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.