WO2019212977A1 - Stable alloy of palladium hydride with high hydrogen content - Google Patents

Abstract

A palladium hydride nanomaterial includes nanostructures having chemical composition represented by the formula: PdFh, wherein x is at least about 0.43.

Description

STABLE ALLOY OF PALLADIUM HYDRIDE WITH HIGH HYDROGEN

CONTENT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/664,764, filed April 30, 2018, the contents of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

[0002] This disclosure generally relates to a palladium hydride nanomaterial.

BACKGROUND

[0003] Palladium hydride is desirable for use in catalytic applications. However, such use has been hampered by the difficulty of access to stable palladium hydride.

[0004] It is against this background that a need arose to develop the embodiments described herein.

SUMMARY

[0005] In some embodiments, a palladium hydride nanomaterial includes nanostructures having a chemical composition represented by the formula: PdEE, wherein x is at least about 0.43.

[0006] In additional embodiments, a solution phase synthesis method to form a palladium hydride nanomaterial includes reacting a palladium-containing precursor in the presence of a surface-modification reagent in a liquid medium to form palladium hydride nanostructures.

[0007] In further embodiments, a solution phase synthesis method to form a palladium hydride nanomaterial includes: (1) providing a dispersion of palladium nanostructures as seeds; and (2) reacting the seeds in the presence of a surface-modification reagent in a liquid medium to form palladium hydride nanostructures.

[0008] Other aspects and embodiments of this disclosure are also contemplated. The foregoing summary and the following detailed description are not meant to restrict this disclosure to any particular embodiment but are merely meant to describe some embodiments of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a better understanding of the nature and objects of some embodiments of this disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.

[0010] Figure 1. Scheme of the formation of b-PdEE using amines or thiols as capping agents for surface modification where“X” represents amine or thiol groups and“R” represents n-CnFhn+i.

[0011] Figure 2. X-Ray Diffraction (XRD) patterns of PdEE nanostructures: (a) Polycrystals, (b) Nanocubes, and (c) Nanotetrahedra.

[0012] Figure 3. Bragg’s equation for an explanation of XRD results.

[0013] Figure 4. Lattice expansion versus H/Pd ratio. Results based on XRD analysis of PdEE nanoparticles with surface modification.

[0014] Figure 5. (a) Palladium Nanocubes, (b) PdFE/butylamine nanocubes, (c) PdFE/octyl amine nanocubes, (d) PdFF/butanethiol nanocubes, (e) PdFF/hexanethiol nanocubes, (f) Palladium Nanotetrahedra, (g) PdFE/butyl amine nanotetrahedra, (h) PdFE/octyl amine nanotetrahedra, (i) PdEE/butanethiol nanotetrahedra, and (j) PdEE/hexanethiol nanotetrahedra.

[0015] Figure 6. X-ray Photoelectron Spectroscopy (XPS) analysis: (A) PdEE/butyl amine nanocubes and (B) PdEE/1 -butanethiol nanocubes.

[0016] Figure 7. XPS analysis: (A) PdFE/amine nanocubes compared with Pd nanocube seeds and (B) PdFE/thiol nanocubes compared with Pd nanocube seeds.

DETAILED DESCRIPTION

[0017] Embodiments of this disclosure are directed to a class of palladium-based hydride nanomaterials, including nanostructures of palladium hydride which can be synthesized through solution phase synthesis. The palladium hydride nanostructures can encompass a wide composition range, including beta-palladium hydride alloy (b-PdFE) with surface modification and a high molar hydrogen content or a high molar ratio of hydrogen to palladium. Advantageously, palladium hydride nanomaterials can be synthesized in the nanoscale via solution phase synthesis, which can be carried out under moderate conditions, can attain high yields, and can attain a high hydrogen content. Resulting palladium hydride nanomaterials can be stable over extended time periods, and without specifying a hydrogen- rich atmosphere or maintaining an external hydrogen pressure for such prolonged stability.

[0018] In some embodiments, a palladium hydride nanomaterial is an alloy of palladium and hydrogen having a chemical composition that can be represented by the formula PdFE, where (1) Pd represents palladium; (2) H represents hydrogen; and (3) x represents a molar content of hydrogen and has a non-zero value in a range of 0 to about 1, such as from about 0.43 to about 1, from about 0.5 to about 1, from about 0.6 to about 1, from about 0.7 to about 1, from about 0.8 to about 1, or from about 0.9 to about 1, although values of x greater than about 1 are also encompassed by this disclosure. Other embodiments are encompassed by this disclosure, such a ternary or a higher order alloy of palladium, hydrogen, and at least one additional metal different from palladium, such as a transition metal selected from Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11, and Group 12 of the Periodic Table.

[0019] In some embodiments, a palladium hydride nanomaterial includes multiple nanostructures having the above-noted chemical composition, where (1) the nanostructures have sizes (or have an average size) in a range of about 1 nm to about 200 nm, such as from about 1 nm to about 100 nm, from about 1 nm to about 80 nm, from about 1 nm to about 60 nm, from about 1 nm to about 40 nm, from about 1 nm to about 20 nm, from about 1 nm to about 18 nm, from about 10 nm to about 18 nm, or from about 15 nm to about 18 nm; (2) the nanostructures have aspect ratios (or have an average aspect ratio) in a range of up to about 3, such as from about 1 to about 3, from about 1 to about 2.5, from about 1 to about 2, or from about 1 to about 1.5, or in a range of greater than about 3, such as about 4 or greater, about 5 or greater, or about 10 or greater; and (3) the nanostructures are largely or substantially crystalline, such as with a percentage of crystallinity (by volume or weight) of at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 98%, or at least about 99% or more. A palladium hydride nanomaterial including nanostructures can have a high specific surface area to promote catalytic activity, such as a Brunauer-Emmett-Teller (BET) specific surface area of at least about 1 m²/g, at least about 5 m²/g, at least about 10 m²/g, at least about 15 m²/g, or at least about 20 m²/g, and up to about 40 m²/g or more, up to about 60 m²/g or more, up to about 80 m²/g or more, or up to about 100 m²/g or more. [0020] Palladium hydride nanomaterials can have a variety of morphologies. For example, a palladium hydride nanomaterial can be in the form of polycrystal nanoparticles having a spherical or spheroidal shape, and an aspect ratio in a range of up to about 3, such as from about 1 to about 3, from about 1 to about 2.5, from about 1 to about 2, or from about 1 to about 1.5. As another example, a palladium hydride nanomaterial can be in the form of nanoparticles shaped as nanocubes or nanotetrahedra. Other morphologies are encompassed by this disclosure, including nanobranches; nanorods, nanowires, or other elongated nanostructures having aspect ratios greater than about 3; core-shell structures; core-multi- shell structures; and nanoparticle-decorated cores, amongst others.

[0021] Advantageously, embodiments of a palladium hydride nanomaterial can be synthesized in solution phase and can remain stable for extended time periods, provided that the nanomaterial is not stored at elevated temperatures. In some embodiments, a solution phase synthesis is a one-stage synthesis and can be carried out by reacting a palladium- containing precursor in the presence of a surface-modification reagent (or capping agent) in a liquid medium to form palladium hydride nanostructures. Suitable palladium-containing precursors include an organometallic coordination complex of palladium with an organic anion, such as acetylacetonate. The liquid medium includes one or more solvents, such as one or more organic solvents selected from polar aprotic solvents, polar protic solvents, and non polar solvents. In some embodiments, a suitable solvent is a hydrogen-containing solvent that decomposes in situ to form hydrogen gas, which can be incorporated into palladium to form palladium hydride. An example of such a solvent is an amide, such as N,N- dimethylformamide. In some embodiments, a solvent included in the liquid medium also can serve as a reducing agent for reduction of palladium, although the inclusion of a separate reducing agent is also contemplated. In some embodiments, the solution phase synthesis can be carried out by including one or more short chain amines, such as n-butylamine, n- octylamine, or another suitable amine, diamine, or polyamine including 1-15, 1-10, 4-15, 4- 10, 2-15, 2-10, 1-5, or 2-5 carbon atoms per molecule, as a surface-modification reagent to control a morphology and a size of nanostructures, and to promote incorporation of hydrogen into palladium. Alternatively, or in conjunction, one or more short chain thiols, such as 1- butanethiol, l-hexanethiol, l-octanethiol, l-decanethiol, l-dodecanethiol, or another thiol including 1-15, 1-10, 4-15, 4-10, 2-15, 2-10, 1-5, or 2-5 carbon atoms per molecule, can be used as a surface-modification reagent. Reaction can be carried out under conditions of a temperature in a range of about l00°C to about 300°C or about l00°C to about 250°C, and a time duration in a range of about 1 hour to about 10 hours or about 2 hours to about 6 hours.

[0022] In additional embodiments, a solution phase synthesis is a two-stage synthesis and can be carried out by: (1) providing a dispersion of palladium nanostructures as seeds; and (2) reacting the seeds in the presence of a surface-modification reagent in a liquid medium to form palladium hydride nanostructures. The liquid medium in (2) includes one or more solvents, such as one or more organic solvents selected from polar aprotic solvents, polar protic solvents, and non-polar solvents. In some embodiments, a suitable solvent is a hydrogen-containing solvent that decomposes in situ to form hydrogen gas, which can be incorporated into the seeds to form palladium hydride. An example of such a solvent is an amide, such as N,N-dimethylformamide. In some embodiments, the reacting in (2) can be carried out by including one or more short chain amines, such as n-butylamine, n-octylamine, or another suitable amine, diamine, or polyamine including 1-15, 1-10, 4-15, 4-10, 2-15, 2- 10, 1-5, or 2-5 carbon atoms per molecule, as a surface-modification reagent to control a morphology and a size of nanostructures, and to promote incorporation of hydrogen into palladium. Alternatively, or in conjunction, one or more short chain thiols, such as 1- butanethiol, l-hexanethiol, l-octanethiol, l-decanethiol, l-dodecanethiol, or another thiol including 1-15, 1-10, 4-15, 4-10, 2-15, 2-10, 1-5, or 2-5 carbon atoms per molecule, can be used as a surface-modification reagent. Reaction can be carried out under conditions of a temperature in a range of about l00°C to about 300°C or about l00°C to about 250°C, and a time duration in a range of about 2 hours to about 24 hours or about 10 hours to about 20 hours.

[0023] Example applications of palladium hydride nanomaterials include: (1) catalysts for reactions such as refining, exhaust gas treatment, or for chemical synthesis and petrochemical applications; (2) use as chemical sensors, such as hydrogen sensors; and (3) use for hydrogen storage.

Example

[0024] The following example describes specific aspects of some embodiments of this disclosure to illustrate and provide a description for those of ordinary skill in the art. The example should not be construed as limiting this disclosure, as the example merely provides specific methodology useful in understanding and practicing some embodiments of this disclosure. [0025] Experimental Section

[0026] Chemicals and Materials.

[0027] Palladium (II) acetylacetonate [Pd(acac)2] (about 99%) and molybdenum hexacarbonyl [Mo(CO)₆] were purchased from Alfa Aesar. N,N-dimethylformamide (DMF) was purchased from Fisher Scientific. Sodium tetrachloropalladate [Na2PdCl₄], n-octylamine, n-butylamine, l-butanethiol, l-hexanethiol, l-octanethiol, l-decanethiol, l-dodecanethiol, formaldehyde (about 37% solution), L-ascorbic acid, potassium bromide, and poly(vinylpyrrolidinone) (PVP) were purchased from Sigma Aldrich.

[0028] Synthesis of Nanostructures

[0029] Synthesis of polycrystal palladium hydride particle.

[0030] About 8 mg of Pd(acac)2 is dispersed in about 10 mL of DMF, about 100 pL of amine (n-Butylamine or n-Octylamine) or thiol (l-Butanethiol, l-Hexanethiol, 1- Octanethiol, l-Decanethiol, or l-Dodecanethiol) was added, and the mixture was heated at about l40°C for about 4 hours.

[0031] Synthesis of nanocubes palladium hydride particle.

[0032] Two stages:

[0033] First, preparation of palladium nanocubes seeds was performed: about 60 mg of L-ascorbic acid, about 600 mg of KBr, about 80 mg of PVP, and about 57 mg of Na2PdCl₄ were dispersed in about 11 mL of water, and the mixture was heated at about 80°C for about 3 hours.

[0034] Second, preparation of palladium hydride nanocubes was performed: about 2 mg of palladium nanocubes seeds were dispersed in about 10 mL of DMF, about 100 pL of amine (n-Butylamine or n-Octylamine) or about 100 pL of thiol (l-Butanethiol, 1- Hexanethiol, l-Octanethiol, l-Decanethiol, or l-Dodecanethiol) was added, and the mixture was heated at about l40°C for about 16 hours.

[0035] Synthesis of nanotetrahedra palladium hydride particle.

[0036] Two stages:

[0037] First, preparation of palladium nanotetrahedra seeds was performed: about 30 mg of Pd(acac)2, about 50 mg of PVP, about 0.1 mL of formaldehyde solution (37%), and about 2 mg of Mo(CO)₆ were dispersed in about 10 mL of DMF, and the mixture was heated at about l60°C for about 4 hours. [0038] Second, preparation of palladium hydride nanotetrahedra was performed: about 2 mg of palladium nanotetrahedra seeds were dispersed in about 10 mL of DMF, about 100 pL of amine (n-Butylamine or n-Octylamine) or about 100 pL of thiol (l-Butanethiol, 1- Hexanethiol, l-Octanethiol, l-Decanethiol, or l-Dodecanethiol) was added, and the mixture was heated at about l40°C for about 16 hours.

[0039] The following Table 1 summarizes synthesis conditions to obtain palladium hydride nanoparticles with different hydrogen content.

Table 1. Synthesis conditions for PdH_x using different capping agents attached for surface modification of nanoparticles

[0040] Post Synthesis Treatment.

[0041] The resulting products were collected, washed and centrifuged about 3 times with Ethanol.

[0042] Result and Discussion

[0043] Figure 1 indicates a proposed scheme for the formation of stable palladium hydride nanostructures due to in situ production of hydrogen gas from catalytic decomposition of DMF. Attachment of capping agents as amines and thiols serve to modify a surface of palladium to contribute to the formation of palladium hydride.

[0044] After synthesis procedure, samples were characterized by Pan Powder XRD (X-Ray Diffraction), Titan S/TEM (FEI) (transmission electron microscope) with HR-TEM (High Resolution-TEM) mode, and XPS (X-ray Photoelectron Spectroscopy).

[0045] The following results show XRD patterns corresponding to the highest ratios of palladium hydride PdH_x nanomaterials synthesized for different shapes: polycrystals, nanocubes and nanotetrahedra (Refer to Table 1 for synthesis conditions).

[0046] Figure 2 also includes diffraction patterns for respective palladium seeds (Pd-dark lines).

[0047] From the XRD analysis data, the formation of palladium hydride can be confirmed since the XRD patterns show peaks shifted to a lower angle for all samples synthesized when compared with the diffraction pattern of Pd samples. These peak shifts indicate and confirm the formation of palladium hydride, which indicate a lattice expansion of the Face Centered Cubic (FCC) unit cell of palladium due to the incorporation of hydrogen atoms that occupy the octahedron sites within the palladium FCC packing.

[0048] Moreover, during the synthesis of the palladium hydride nanoparticles, the metal precursor used for the formation of palladium hydride was palladium (II) acetyl acetonate (refer to the Experimental Section). Therefore, the increase in lattice parameter is attributed to the formation of palladium hydride alloy and not to the formation of a palladium alloy with another metal that could also present a peak shift. This is also confirmed with the XPS analysis where the palladium peak is the sole metal peak presented.

[0049] Two distinctive phases can be present in the palladium hydride system: a- phase (poor in hydrogen) and b-phase (rich in hydrogen) at temperatures below about 298°C and pressures below about 2 MPa. The presence of a specific palladium hydride phase depends on the hydrogen concentration in the metal. Therefore, lattice parameter is an indicator of the phase and ratio of H:Pd obtained. For instance, a lattice parameter of about 3.89 A indicates the formation of a phase, and up to about 4.10 A corresponds to b phase. The lattice parameters of the two phases correspond to a specific H:Pd ratio value or x, where a pure a phase exists at x < about 0.017 whereas a pure b phase is present for x > about 0.58, and intermediate x values correspond to a-b mixtures. Table 2 below indicates lattice expansion percentages and H:Pd ratios.

[0050] XRD analysis provides values of an angle at which the characteristic palladium peaks are present. Therefore, referring to Figure 3, Bragg’s equation provides an explanation of the results:

2dsin0 = hl

where Q is the angle of incidence of an X-ray.

[0051] From this relation, it can be observed that the angle and d-spacing are inversely proportional. Therefore, as the angle decreases, the d-spacing is increased. The d- spacing is also related to the lattice parameter as is indicated in the following equation for a cubic system:

where“d” is the inter-planar distance and“a” is the lattice parameter

[0052] Consequently, as the angle of the peak in the XRD pattern decreases, the inter-planar distance increases as well as the lattice parameter. Thus, the formation of palladium hydride can be confirmed since the lattice has expanded due to the incorporation of hydrogen atoms into the palladium lattice.

[0053] Based on the lattice parameter values calculated from the XRD patterns, the ratios of the PdFF nanostructures are obtained with accuracy. For instance, a general difference in the lattice expansion can be observed for polycrystals, nanocubes and nanotetrahedra. Specifically, nanocubes and nanotetrahedra present higher lattice expansion than polycrystals. These results indicate that palladium hydride can be synthesized at different ratios of PdH_Y, which translates into the ability to tune its properties, and also indicates the highest ratios of H:Pd obtained.

[0054] In addition, Figure 2 also includes XRD patterns of each nanostructure obtained by attaching different thiols and amines to the surface of palladium nanoparticles to form stable palladium hydride with a high hydrogen content. From these results, it can be observed that the highest ratios of PdH_x are obtained when thiols groups are modifying its surface. The following Table 2 and Figure 4 summarize the stable highest ratios H/Pd obtained with the addition of amines or thiols as capping agents for surface modification.

Table 2. Summary of results based on XRD analysis showing lattice parameter, lattice expansion %, and highest ratios of PdHx nanoparticles with surface modification

*Palladium, theoretical value

a Palladium, experimental value

[0055] Nanostructures modified with thiol groups present higher hydrogen content, which may be explained by a thiol chain being adsorbed on a surface of Pd particles by stable bonding between Pd atoms and S atoms. This is further corroborated by XPS analysis discussed below.

[0056] In addition, TEM and HR-TEM analysis is performed. HR-TEM results corroborate the data from the XRD analysis by measuring the d-spacing between the atomic planes. TEM analysis allows observation of the shape and morphology of the nanostructures. Besides from TEM images of the nanostructures, their sizes were also calculated.

[0057] Figure 5 shows by way of example the shape, morphology, size and d- spacing obtained for palladium hydride samples synthesized using amines and thiols as capping agents. It is also shown in Figure 5 corresponding palladium nanoparticles for comparison purposes.

[0058] From the HR-TEM results, it is observed that the data related to the d- spacing is correlated with the XRD lattice parameter values, which confirms once again the expansion of lattice.

[0059] Moreover, analysis of the nanoparticles sizes was performed based on the TEM results since a proportion of activated atoms on a surface increases as the particle size decreases. Therefore, a greater hydrogen storage capacity and a higher hydrogen absorption/desorption rate can be present as the particle size decreases. The results show that the size of the palladium hydride nanoparticles is reduced when compared with other synthesis performed at a higher temperature (about l60°C versus about l40°C). The synthesized nanostructures present a size (diameter) in a range of about 16.8-17.8 nm whereas the nanoparticles synthesized at a higher temperature present larger sizes, in a range of about 19-20 nm.

[0060] Finally, XPS analysis is performed on the synthesized samples. Figure 6 shows two types of samples as examples for the XPS analysis: the first sample is surface decorated with amine group and the second is surface decorated with thiol group.

[0061] From the results, it can be observed that peaks at the binding energy of palladium and nitrogen are present when the nanoparticles are surface decorated with amines groups. Instead, when thiols groups are used as the capping agent, a sulfur peak at its binding energy is observed; also smaller peaks of nitrogen are observed when thiols are used due to the decomposition of DMF during the synthesis of the PdFF nanoparticles. Therefore, the binding of sulfur and nitrogen to the surface of the palladium hydride can be confirmed.

[0062] Furthermore, if the results of the palladium hydride decorated with amines and thiols are compared with their corresponding palladium seeds (Figure 7), a chemical shift of the palladium peaks 3ds/2 and 3d3/2 to a higher binding energy can be observed, which indicates and confirms the formation of the palladium hydride alloy (from Pd to PdFF).

[0063] Conclusions

[0064] This example demonstrates a streamlined and efficient synthesis of PdFF nanoparticles with controllable sizes and H:Pd ratios, thereby allowing tuning of properties. Stable b-PdFF with high ratios is attained, with up to x of about 1.0 utilizing in situ produced hydrogen gas from the catalytic decomposition of DMF and by using capping agents as amines and thiols which are attached to palladium surface of nanoparticles having different morphology to transform them into stable palladium hydride. The remarkable ratios for b- PdFF obtained demonstrate a coherent pathway for the understanding of b-PdFF, and for tailoring its properties for various technological applications.

[0065] As used herein, the singular terms“a,”“an,” and“the” may include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an object may include multiple objects unless the context clearly dictates otherwise.

[0066] As used herein, the term“set” refers to a collection of one or more objects. Thus, for example, a set of objects can include a single object or multiple objects. Objects of a set also can be referred to as members of the set. Objects of a set can be the same or different. In some instances, objects of a set can share one or more common characteristics. [0067] As used herein, the terms“substantially” and“about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, a first numerical value can be“substantially” or“about” the same as a second numerical value if the first numerical value is within a range of variation of less than or equal to ±10% of the second numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0068] As used herein, the term“size” refers to a characteristic dimension of an object. Thus, for example, a size of an object that is spherical can refer to a diameter of the object. In the case of an object that is non- spherical, a size of the non-spherical object can refer to a diameter of a corresponding spherical object, where the corresponding spherical object exhibits or has a particular set of derivable or measurable properties that are substantially the same as those of the non-spherical object. When referring to a set of objects as having a particular size, it is contemplated that the objects can have a distribution of sizes around the particular size. Thus, as used herein, a size of a set of objects can refer to a typical size of a distribution of sizes, such as an average size, a median size, or a peak size.

[0069] Additionally, concentrations, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. For example, a range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual values such as about 2, about 3, and about 4, and sub-ranges such as about 10 to about 50, about 20 to about 100, and so forth. [0070] While the disclosure has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the disclosure as defined by the appended claims. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, method, operation or operations, to the objective, spirit and scope of the disclosure. All such modifications are intended to be within the scope of the claims appended hereto. In particular, while certain methods may have been described with reference to particular operations performed in a particular order, it will be understood that these operations may be combined, sub-divided, or re-ordered to form an equivalent method without departing from the teachings of the disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations are not a limitation of the disclosure.

Claims

What is claimed is:

1. A palladium hydride nanomaterial, comprising:

nanostructures having a chemical composition represented by the formula: PdH_Y, wherein x is at least 0.43.

2. The palladium hydride nanomaterial of claim 1, wherein x is in a range of 0.43 to 1.

3. The palladium hydride nanomaterial of claim 2, wherein x is in a range of 0.5 to 1, 0.6 to 1, 0.7 to 1, 0.8 to 1, or 0.9 to 1.

4. The palladium hydride nanomaterial of any one of claims 1-3, wherein the nanostructures have sizes in a range of 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 80 nm, 1 nm to 60 nm, 1 nm to 40 nm, 1 nm to 20 nm, 1 nm to 18 nm, 10 nm to 18 nm, or 15 nm to 18 nm.

5. The palladium hydride nanomaterial of any one of claims 1-3, wherein the nanostructures are crystalline.

6. The palladium hydride nanomaterial of any one of claims 1-3, having a specific surface area of at least 1 m²/g, at least 5 m²/g, at least 10 m²/g, at least 15 m²/g, or at least 20 m²/g.

7. The palladium hydride nanomaterial of any one of claims 1-3, wherein the nanostructures include a beta-phase of palladium hydride.

8. A solution phase synthesis method to form a palladium hydride nanomaterial, comprising:

reacting a palladium-containing precursor in the presence of a surface-modification reagent in a liquid medium to form palladium hydride nanostructures.

9. The method of claim 8, wherein the liquid medium includes a hydrogen-containing solvent.

10. The method of claim 9, wherein the hydrogen-containing solvent is an amide.

11. The method of any one of claims 8-10, wherein the surface-modification reagent includes an amine.

12. The method of claim 11, wherein the amine includes 1-15, 1-10, 4-15, 4-10, 2-15, 2- 10, 1-5, or 2-5 carbon atoms per molecule.

13. The method of any one of claims 8-10, wherein the surface-modification reagent includes a thiol.

14. The method of claim 13, wherein the thiol includes 1-15, 1-10, 4-15, 4-10, 2-15, 2-10, 1-5, or 2-5 carbon atoms per molecule.

15. A solution phase synthesis method to form a palladium hydride nanomaterial, comprising:

providing a dispersion of palladium nanostructures as seeds; and

reacting the seeds in the presence of a surface-modification reagent in a liquid medium to form palladium hydride nanostructures.

16. The method of claim 15, wherein the liquid medium includes an amide.

17. The method of any one of claims 15-16, wherein the surface-modification reagent includes an amine.

18. The method of claim 17, wherein the amine includes 1-15, 1-10, 4-15, 4-10, 2-15, 2- 10, 1-5, or 2-5 carbon atoms per molecule.

19. The method of any one of claims 15-16, wherein the surface-modification reagent includes a thiol.

20. The method of claim 19, wherein the thiol includes 1-15, 1-10, 4-15, 4-10, 2-15, 2-10, 1-5, or 2-5 carbon atoms per molecule.