阅读说明：本技术 用于增加材料中的氢捕集空位的方法 (Method for increasing hydrogen trapping vacancies in materials ) 是由 D·R·伯吉斯 M·R·格林沃尔德 B·W·巴比 于 2018-03-28 设计创作，主要内容包括：本发明公开了用于增加金属结构中的空位和用于改善金属结构中的氢加载比率的方法和设备。所述金属结构包括一种或多种过渡金属或金属合金。所述金属结构通过形成金属有机前体,和将所述前体还原成金属结构来制备,其中金属原子的配位数减少并且所述金属结构中的所空位增加。(Methods and apparatus for increasing vacancies in metallic structures and for improving hydrogen loading ratios in metallic structures are disclosed. The metal structure includes one or more transition metals or metal alloys. The metal structure is prepared by forming a metal organic precursor, and reducing the precursor to a metal structure, wherein the coordination number of the metal atom decreases and the vacancies in the metal structure increase.)

1. A method of reducing the coordination number of a metal atom in the metallic structure of a transition metal or metal alloy, the method comprising:

forming a metal organic liquid phase precursor; and

reducing the metalorganic liquid phase precursor to a crystalline metal structure;

wherein the coordination number of the transition metal at the intersection of the crystal faces is reduced on the surface of the metal structure.

2. The method of claim 1, wherein the metal-organic liquid phase precursor comprises a metal acetylacetonate solution.

3. The method of claim 2, wherein the metal acetylacetonate solution is a mixture of a metal acetylacetonate, a formaldehyde solution, and a 1-octylamine solution, and wherein reducing the metal acetylacetonate solution to a metal structure comprises:

heating the metal acetylacetonate solution at a first temperature for a first period of time;

cooling the heated solution to room temperature;

centrifuging the solution to obtain a solid product of nanocrystals; and

the nanocrystals are washed with ethanol or acetone or a mixture of both.

4. The method of claim 3, wherein the first temperature is between 200 ℃ and 300 ℃.

5. The method of claim 3, wherein the first period of time is a minimum of five hours.

6. The method of claim 3, further comprising rinsing the nanocrystals two to five times with ethanol, acetone, or a mixture of both.

7. The method of claim 3, wherein the formaldehyde solution is 40%.

8. The method of claim 2, wherein reducing the metal acetylacetonate solution to a metal structure comprises:

heating a substrate made of borosilicate glass to a first temperature; and

depositing the metal acetylacetonate solution on the substrate using a pulse sequence.

9. The method of claim 8, wherein the pulse sequence comprises N₂、N₂Purge, air and N₂Purging the supported metal acetylacetonate solution.

10. The method of claim 8, wherein the first temperature is between 350 ℃ and 400 ℃.

11. The method of claim 1, wherein the transition metal or metal alloy comprises one or more of: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb.

12. A method of reducing the coordination number of a metal atom in a metal oxide film comprising a transition metal or metal alloy, the method comprising:

dissolving a metal organic solid phase precursor to form a solution;

injecting the solution into an inert carrier gas in a vaporization unit at a first temperature to produce a vaporized precursor;

depositing the vaporized precursor on a heated substrate, wherein the substrate is heated to a predetermined temperature required to remove the organic portion from the precursor; and

introducing oxygen to form a thin metal oxide film on the substrate;

wherein the metal atoms at the surface of the metal oxide film have a reduced coordination number.

13. The method of claim 12, wherein the metalorganic solid phase precursor comprises 2,2,6, 6-tetramethyl-3, 5-heptanedionato metal dissolved in n-butylhexane.

14. The method of claim 13, further comprising:

heating the metal oxide film in an inert gas atmosphere;

reducing the metal oxide to remove oxygen atoms; and

vacancies are formed to reduce the coordination number of the metal atoms in the metal oxide film.

15. The method of claim 12, wherein the substrate comprises sapphire.

16. The method of claim 12, wherein the first temperature is between 240 ℃ and 260 ℃.

17. The method of claim 12, wherein the predetermined temperature is between 275 ℃ and 325 ℃.

18. The method of claim 12, wherein the transition metal or metal alloy comprises one or more of: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb.

19. The method of claim 12, wherein the inert gas comprises argon.

20. A method of reducing the coordination number of a metal atom in a metal oxide film of a first transition metal, the method comprising:

sublimating a metal-organic precursor to produce a sublimated precursor at a first temperature, the sublimated precursor comprising a first transition metal;

depositing the sublimation precursor on a substrate to form a metal film;

introducing oxygen to form a metal oxide in the metal film; and

doping the metal film with a second transition metal;

wherein the second transition metal creates vacancies in the metal film and reduces the coordination number of the first transition metal.

21. The method of claim 20, wherein the metal precursor comprises a 2,2,6, 6-tetramethyl-3, 5-heptanedionato metal dissolved in butylhexane.

22. The method of claim 21, wherein the first transition metal comprises one or more of: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb.

Technical Field

The present invention relates generally to increasing defects or vacancies in transition metal structures, and more particularly, to reducing the coordination number of metal atoms in a metal structure to increase hydrogen trapping vacancies.

Background

Some transition metals are known to have good hydrogen absorption capacity and can be used for hydrogen storage. It is also well known that a few transition metals, when loaded with hydrogen/deuterium, can be used as catalysts in exothermic reactions. Studies have shown that the amount of abnormal heat generated in such exothermic reactions depends on the hydrogen loading ratio of the catalyst used in the reaction.

The hydrogen loading ratio measures the ratio of the number of hydrogen/deuterium atoms in the lattice (in a transition metal lattice loaded with hydrogen/deuterium) to the number of metal atoms. The hydrogen loading ratio reflects the amount of hydrogen/deuterium that has been loaded into the metal lattice. Under normal conditions, a hydrogen loading ratio of 0.8-0.9 can be achieved for the transition metal lattice. It is often difficult to achieve hydrogen loading ratios near or above 1.0. Various techniques can be used to increase the hydrogen loading ratio in the transition metal. However, these techniques typically require high pressure and high temperature exposure. In some cases, an excess time requirement of about several days may be required. In some cases, predictability and control is lacking.

Accordingly, there is a need in the art for improving the hydrogen loading capability of transition metal lattices.

The background section of this document is provided to place embodiments of the present invention in a technical and operational context to assist those of ordinary skill in the art in understanding its scope and utility. The approaches described in the background section are approaches that could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Accordingly, unless expressly stated otherwise, the statements herein are not to be construed as an admission that they are merely prior art to the inclusion of this background.

Disclosure of Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to those skilled in the art. This summary is not an extensive overview of the disclosure and is intended to neither identify key/critical elements of the embodiments nor delineate the scope of the embodiments. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

Exemplary methods and apparatus for increasing vacancies in metallic structures are disclosed. More vacancies in the metal structure improve the hydrogen loading capability of the metal structure.

In some embodiments, vacancies in the transition metal structure are increased by reducing the coordination number of the metal atoms located at the intersections of the crystal faces. The transition metal or metal alloy comprises one or more of the following metals: titanium (Ti), zirconium (Zr), hafnium (Hf), chromium (Cr), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), iron (Fe), ruthenium (Ru), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), aluminum (Al), indium (In), tin (Sn) and lead (Pb).

In one embodiment, a metal organic liquid phase precursor comprising a transition metal or metal alloy is prepared. For example, the metal organic liquid precursor may include a metal acetylacetonate, a formaldehyde solution, and a 1-octylamine solution. The metal-organic liquid phase precursor is then reduced to a metal structure. For example, the process of reducing the metal organic liquid precursor may include the following steps. First, a metal acetylacetonate solution is heated at a first temperature for a first period of time. The solution was heated and then cooled to room temperature, and the solution was centrifuged to obtain a solid product of nanocrystals. The solid product of the nanocrystals is washed with ethanol or acetone or a mixture of both. In some embodiments, the solid product of nanocrystals is washed multiple times, e.g., two to five times, with ethanol or acetone or a mixture of both.

In one embodiment, the process of reducing the metal acetylacetonate solution to a metal structure includes heating a substrate made of borosilicate glass to a first temperature and depositing metal acetylacetonate on the substrate using a pulse sequence. In one embodiment, the pulse sequence comprises N₂、N₂Purge, air and N₂Purging the supported metal acetylacetonate.

In some embodiments, the coordination number of the metal atoms in the metal oxide film is reduced. The metal oxide film includes a transition metal or a metal alloy. The metal oxide film can be prepared according to the following procedure. First, a metal organic solid phase precursor is dissolved to form a solution. The solution is then injected into an inert carrier gas in a vaporization cell (vaporizing cell) at a first temperature to prepare a vaporized precursor. The vaporized precursor is then deposited on a heated substrate. The substrate is heated to or above a predetermined temperature required for removing the organic portion of the precursor. Once the organic portion is removed from the precursor, a thin film of metal oxide is formed on the substrate. This is because oxidation occurs only on or near the substrate. The metal atoms in the metal oxide film have a reduced coordination number at the film surface. In one embodiment, the metal organic solid phase precursor comprises 2,2,6, 6-tetramethyl-3, 5-heptanedionato metal (metal 2,2,6, 6-tetramethylheptanate-3, 5-dionato) dissolved in n-butylhexane. In one embodiment, the process further comprises heating the metal oxide film in an inert gas atmosphere, reducing the metal oxide to remove oxygen atoms, and forming vacancies to reduce the coordination number of the metal atoms in the metal oxide film.

In some embodiments, the coordination number of metal atoms in the metal oxide film is reduced by subliming a metal-organic precursor to produce a sublimated precursor at a first temperature. The precursor includes a first transition metal. The sublimation precursor is deposited on a substrate to form a metal film. Oxygen is introduced to produce a metal oxide in the metal film. The metal film is then doped with a second transition metal. The second transition metal creates vacancies in the metal film, which vacancies reduce the coordination number of the first transition metal. Examples of the first or second transition metal include one or more of: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb. In one embodiment, the metal precursor comprises 2,2,6, 6-tetramethyl-3, 5-heptanedionato metal dissolved in butyl hexane.

Drawings

FIG. 1 illustrates an exemplary chromium crystal body-centered cubic structure;

FIG. 2 illustrates an exemplary rutile phase titanium oxide crystal structure;

FIG. 3 illustrates an exemplary palladium lattice structure comprising (100) planes and (111) planes;

FIG. 4 is a flow diagram illustrating an exemplary process for reducing the coordination number of a metal atom in a metal structure using a metalorganic liquid precursor;

FIG. 5 is a flow diagram illustrating an exemplary process for reducing the coordination number of a metal atom in a metal structure using a metal organic solid phase precursor;

FIG. 6 is a flow diagram illustrating an exemplary process for reducing the coordination number of metal atoms in a metal structure by subliming a metal organic precursor.

Detailed Description

For simplicity and illustrative purposes, the present invention is described by referring mainly to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without limitation to these specific details. In the description, well-known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.

Fig. 1 shows a body centered cubic crystal structure 100. Chromium is an exemplary transition metal having a bcc crystal structure. In a perfect bcc crystal structure 100, each atom (e.g., atoms 104, 106, 108, 110, etc.) on the corners of the lattice is adjacent to ten atoms, i.e., has a coordination number of 10. Each atom (e.g., atom 102) located at the center of the lattice is adjacent to eight atoms, with a coordination number of 8. In the example of chromium, the chromium atom 102 has eight nearest neighbor atoms: 104. 106, 108, 110, 114, 116, 118 and 120. Chromium atom 110 has ten nearest neighbor atoms: 102. 106, 108, 120 and six other adjacent atoms not shown. When a chromium atom is removed from the bcc crystal structure, a vacancy is created and the coordination number of any atom adjacent to the removed atom is reduced. For example, when the chromium atom 102 is removed from the bcc crystal structure, 104-120 each atom becomes nine coordinates reduced from ten coordinates. Thus, in a metal lattice structure, the creation of vacancies results in a reduction in the coordination number of the metal atoms in the lattice structure.

Fig. 2 shows a rutile phase metal oxide lattice structure 200. Titanium oxide is an exemplary metal oxide having a rutile phase lattice structure. In lattice structure 200, light-colored atoms 202, 204, 206, 208, 210, 212, 214, 216, and 218 are metal atoms. Dark atoms 222, 224, 226, 228, 230, and 232 are oxygen atoms. Each metal atom has six oxygen atoms as its nearest neighbor. If one or more oxygen atoms are removed from the lattice structure, each of its nearest metal atoms becomes pentacoordinated. The coordination number of the metal atom adjacent to the removed oxygen atom decreases from six to five.

Density functional theory calculations suggest that an inverse relationship exists between the ability of a host atom (host atom) to bind a hydrogen atom and the coordination number of the host atom. The present disclosure teaches methods and processes for creating vacancies in a metal lattice structure resulting in a reduced coordination number of the metal atoms in the crystal lattice structure. In lattice structures where the coordination number of the host atom is reduced, more hydrogen atoms may be taken up by the lattice structure, thereby increasing the hydrogen loading ratio of the lattice structure.

In some embodiments, the coordination number of a metal atom in the metal structure of a transition metal or metal alloy is reduced by dissolving the transition metal or metal alloy in a metal acetylacetonate to form a metalorganic liquid phase precursor. The metal organic liquid phase precursor is reduced to a crystalline metal structure. On the surface of the metal structure, the coordination number of the transition metal at the intersection of the two crystal faces decreases.

FIG. 3 shows an exemplary face-centered cubic structure in which the coordination number of atoms on certain crystal planes is reduced. Palladium is an exemplary metal having a face centered cubic structure. In FIG. 3, the nanocrystal structure has large area {411} planes. The 411 planes are faceted into 100 and 111 planes. For palladium, each palladium atom on the {411} plane is 12 coordinates. The palladium atom on the {100} plane is 8-coordinated, and the palladium atom on the {111} plane is 9-coordinated. The palladium atom at the intersection of the {100} and {111} planes is only 5 coordinates. The reduction in coordination number of atoms on the {100} and {111} planes increases the ability of the palladium nanocrystal structure to trap H atoms.

To prepare the palladium nanocrystalline structures described above, in some embodiments, the metal organic liquid phase precursor is prepared by mixing 4 to 5mg of palladium acetylacetonate with 0.04 to 0.05mL of a 40% formaldehyde solution and 8 to 10mL of 1-octylamine. The liquid phase precursor is placed in a teflon-lined metal pressure chamber (e.g., autoclave) and heated at a temperature between 200 ℃ and 300 ℃ for a minimum of five hours. After heating, the liquid phase precursor was cooled to room temperature. The solid product in the liquid phase precursor is centrifuged and then washed with ethanol, acetone or a mixture of both. In some embodiments, the solid product is washed two to five times. The final solid product comprises palladium nanocrystals in which the surface atoms have a reduced coordination number.

In another embodiment, the metal organic liquid precursor is iridium acetylacetonate. The precursor is deposited by atomic layer deposition on a substrate made of borosilicate glass using a pulse sequence. For example, the substrate temperature is maintained between 350 and 400 ℃, and the overall pressure is between 7.5 and 15 torr. The pulse train consists of nitrogen (N)₂)、N₂Blowing, air, N₂The supported iridium acetylacetonate was purged. The iridium precursor and air pulses remained equivalent in the range of 0.5 to 2.5 s. N is a radical of₂The purge pulse is maintained at about 0.5 s. N is a radical of₂In the range of 350 to 450 standard cubic centimeters per minute (sccm). The flow rate of air is in the range of 5 to 40 sccm. In an iridium film formed on a substrate, iridium atoms on the surface of the film have a reduced coordination number, for example, less than 9. The film has an enhanced ability to trap H atoms in a nearby surface layer due to the iridium atoms having a reduced coordination number.

Those skilled in the art can readily modify the ranges of temperatures and pressures described in the above examples and find ranges of conditions in which crystalline films and/or particles of various transition metals with reduced coordination can be produced. Exemplary transition metals include, but are not limited to: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb.

In some embodiments, vacancies in the metal oxide film can be enhanced by reducing oxygen in the metal oxide film. Removing oxygen from the metal oxide film reduces the coordination number of the metal atoms on the surface of the metal oxide film. In one embodiment, a ruthenium (Ru) oxide film is first formed by depositing a metal precursor on a substrate. Oxygen is then removed from the nearby surface layer. In a locally reduced ruthenium oxide film, the Ru atoms have a reduced coordination number due to the many vacancies created at the vacated oxygen lattice sites. For example, a ruthenium oxide film having a majority of (110) oriented grains is deposited using a metal organic solid phase precursor formed by dissolving 2,2,6, 6-tetramethyl-3, 5-heptanedionato ruthenium in n-butyl hexane. The precursor is then injected directly into the vaporization unit via a carrier (e.g., argon gas). The temperature of the cell was maintained between 240 and 260 ℃. The flow rate of the solution was maintained between 0.04ml/min and 0.08ml/min and the flow rate of the carrier gas was maintained between 100 and 150 sccm. In one embodiment, the substrate is made of sapphire and heated to 275 to 325 ℃. The film deposited on the substrate comprises RuO₂And (4) crystals. RuO₂The crystal structure is rutile (tetragonal), and RuO₂The Ru atom in the crystal structure has six nearest-neighbor oxygen atoms, i.e., a coordination number of 6. The nearby surface Ru atoms in the 110 plane are a mixture of 5 and 6 coordinates. The 5-coordinated Ru atoms in the nearby surface layer have an increased ability to trap hydrogen atoms. Furthermore, oxygen atoms in the nearby surface layer may be removed to reduce the coordination number of Ru atoms. The O-vacancy sites result in an increased ability of the membrane to trap hydrogen atoms.

One skilled in the art can apply the methods and processes of metal oxide film deposition described above within a range of conditions within which crystalline thin films of the following metals can produce metal atoms with reduced coordination on their respective surfaces: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb. The coordination number of the metal atoms may also be further reduced by removing oxygen atoms to create O vacancies, resulting in an increased ability to trap hydrogen/deuterium atoms in nearby surface layers.

In some embodiments, a method of reducing the coordination number of a metal atom in a metal oxide film comprises the following steps. First, a metal organic precursor is subjected to sublimation to produce a sublimated precursor at a first temperature. The sublimation precursor includes a first transition metal. Next, the sublimation precursor is deposited on the substrate to form a metal film. Then, oxygen is introduced to prepare a metal oxide in the metal film. The metal film is also doped with a second transition metal that creates vacancies in the metal film and reduces the coordination number of the first transition metal. In some embodiments, the metal precursor comprises a 2,2,6, 6-tetramethyl-3, 5-heptanedionato metal dissolved in butyl hexane. In some embodiments, the coordination number of the first transition metal atom may be further reduced by removing an oxygen atom in the metal film. For example, oxygen atoms in the metal film may be reduced by heating the metal oxide film in an inert gas atmosphere. In some embodiments, the first transition metal comprises one of the following metals or an alloy of two or more of the following metals: ti, Zr, Hf, Cr, V, Nb, Ta, Mo, W, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn and Pb.

In one embodiment, rutile titanium oxide (TiO) having a majority of (110) oriented grains₂) The film was deposited on (110) oriented sapphire using 2,2,6, 6-tetramethyl-3, 5-heptanedionato Ti, which was sublimed by a focused xenon-incandescent lamp at 350 to 375 ℃. The sublimation precursor is carried by helium. Oxygen was added to the reactor. Total pressure of 2 to 5 torr with O₂And equivalent partial pressures of the precursor and carrier gases. The precursor partial pressure is from 0.5 to 20 mtorr. The substrate temperature is 400 to 700 ℃. The film is doped with gallium (Ga) by physically mixing 2,2,6, 6-tetramethyl-3, 5-heptanedionato Ga (iii) into the Ti precursor at 0.1 wt% to 7 wt%. When thoroughly mixed, the weight percent of Ga precursor corresponds to the atomic doping percentage in the film with an error of +/-10%. When Ga atoms replace titanium (Ti) atoms on the rutile lattice, the Ga dopant atoms are compensated by O vacancies or Ti interstitials, respectively. The doping process is obtained by the following two defect formulas:

experimental data has shown that for TiO doped with Ga and other trivalent atoms, such as iron (Fe) and magnesium (Mn)₂O vacancies are the primary compensation mechanism at high temperature and oxygen partial pressure. The generation of O vacancies reduces the coordination number of the Ti atom. The reduced coordination of Ti atoms and O vacancy sites results in an increased ability of the film to trap hydrogen/deuterium atoms.

Fig. 4, 5, and 6 illustrate three exemplary methods for reducing the coordination number of a metal atom in a metal or metal alloy.

FIG. 4 illustrates a first exemplary method for reducing the coordination number of a metal atom. The method includes forming a metal organic liquid phase precursor (step 402), reducing the metal acetylacetonate precursor to a metallic structure (step 404), and reducing the coordination number of the transition metal (step 406), such as at the intersection of crystal faces.

FIG. 5 illustrates a second exemplary method for reducing the coordination number of a metal atom. The method comprises the following steps. First, a metal organic solid phase precursor is dissolved to form a solution (step 502). Next, the solution is then injected into an inert carrier gas (e.g., argon) in a vaporization unit at a first temperature to prepare a vaporized precursor (step 504). The vaporized precursor is then deposited on a heated substrate (step 506). The substrate is heated to or above a predetermined temperature required for removing the organic portion of the precursor. Once the organic portion is removed from the precursor, a thin film of metal oxide is formed on the substrate by introducing oxygen (step 508). This is because oxidation occurs only on or near the substrate.

FIG. 6 illustrates a third exemplary method for reducing the coordination number of a metal atom. The method includes subliming a metal organic precursor to produce a sublimated precursor at a first temperature (step 602). Sublimation precursors are used to create doped metal film structures. The sublimation precursor is deposited on the substrate to form a metal film (step 604), and oxygen is introduced to form a metal oxide in the metal film (step 606). The sublimation precursor is doped with a second transition metal, e.g., gallium (step 608).

The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.