Hydrogen storage composite for low purity hydrogen storage and manufacturing method thereof

Abstract

The present invention relates to a hydrogen storage composite and a manufacturing method thereof. More specifically, the hydrogen storage composite of the present invention has a form in which a hydrogen permeation and oxidation prevention film for selectively separating only hydrogen molecules surrounds hydrogen storage particles, and is a composite in which an existing hydrogen purification process and a storage process are unified. The hydrogen storage composite can prevent oxidation and performance deterioration of the hydrogen storage particles due to oxidizing species gas, and can delay oxidation of the hydrogen storage particles and continuously store hydrogen even under a low-purity hydrogen environment.

Description

Hydrogen storage complex for low-purity hydrogen storage and method for manufacturing the same

[0001] The present invention relates to a hydrogen storage complex for low-purity hydrogen storage and a method for manufacturing the same.

[0002] Hydrogen has a chemical energy density approximately three times higher than that of typical hydrocarbons and is considered a highly efficient, clean energy source, producing no gases other than water during its production. However, because hydrogen is typically bound to water or hydrocarbons rather than in a gaseous state, an additional purification process is essential to obtain pure hydrogen gas. Conventionally, hydrogen has been purified using two main methods: pressure swing adsorption (PSA) and palladium-based hydrogen membranes. However, PSA requires large facilities for complex separation processes and consumes significant energy during operation. Furthermore, even when palladium-based hydrogen membranes are used, maintaining high-temperature and high-pressure environments requires significant energy consumption, and the expensive palladium membranes require periodic replacement. Improving the accessibility of hydrogen energy requires improvements not only in the aforementioned purification process but also in current hydrogen storage methods. Existing physical hydrogen storage methods involve compression and liquefaction. Compression requires pressures of up to 700 bar, while liquefaction requires harsh conditions of -253°C or lower, resulting in significant energy consumption for storage. Therefore, to accelerate the commercialization of hydrogen energy, the limitations of existing purification and storage methods must be addressed to enhance its utility.

[0003] According to one aspect of the present invention, there is provided a hydrogen storage composite comprising a metal hydride hydrogen storage particle and a hydrogen permeation and oxidation prevention film that exhibits selective permeation performance for hydrogen and prevents oxidation of the hydrogen storage particle.

[0004] In addition, we aim to provide a novel hydrogen storage complex that alleviates the need for conventional ultra-high purity purification processes and simultaneously solves the problems of existing physical storage methods.

[0005] In addition, by directly using hydrogen that has not gone through an ultra-high purity purification process for hydrogen storage, the purification process is simplified and integrated with the storage process, thereby solving the problems of conventional hydrogen purification and storage technologies.

[0006] According to another aspect of the present invention, a method for manufacturing the hydrogen storage complex is provided.

[0007] The inventors of the present invention have conducted research to overcome limitations in conventional hydrogen purification and storage processes, and as a result, have developed a new hydrogen storage complex in which the surface of a metal-based hydrogen storage material is covered with a material capable of acting as a hydrogen separation membrane. They have also discovered that such a hydrogen storage complex can improve the problems of conventional technologies by integrating the purification and storage processes, thereby completing the present invention.

[0008] The present invention provides a hydrogen storage composite comprising: a hydrogen storage particle which is a single molecular particle or an aggregate of single molecular particles made of a metal hydride; and a hydrogen permeation and oxidation prevention film formed on a part or all of the surface of the hydrogen storage particle to selectively allow hydrogen permeation and prevent oxidation of the hydrogen storage particle.

[0009] In one embodiment, the hydrogen permeation and oxidation prevention film may be selected from a graphene derivative including one or a mixture thereof selected from the group consisting of graphene oxide (GO), reduced graphene oxide (rGO); graphitic carbon nitride; and one or two or more metal compounds selected from the group consisting of metal oxides, metal nitrides, and pure metals.

[0010] In one embodiment, the hydrogen permeation and oxidation prevention membrane may be included in the hydrogen storage complex at 2 to 50 wt%.

[0011] In one aspect, the metal hydride may be a compound of one or more metals selected from the group consisting of alkali metals, alkaline earth metals, and transition metals.

[0012] In one aspect, the hydrogen storage particles may have an average diameter of 2 nm to 50 μm.

[0013] In one aspect, the hydrogen storage complex may have a capacity retention rate of 23% or more when absorbing hydrogen in a low-purity hydrogen environment.

[0014] In one aspect, the low-purity hydrogen environment may be one in which the composition of hydrogen in the mixed gas is 90% or more.

[0015] Another object of the present invention is to provide a hydrogen storage complex composition comprising the hydrogen storage complex.

[0016] Another object of the present invention is to provide a hydrogen storage method characterized by storing hydrogen in the hydrogen storage complex.

[0017] In one aspect, another object is to provide a method for manufacturing a hydrogen storage composite, comprising the steps of: manufacturing a hydrogen storage particle from a metal hydride precursor solution including a precursor material of the hydrogen storage particle; and mixing the hydrogen storage particle with a hydrogen permeability and oxidation prevention film solution to form a hydrogen permeability and oxidation prevention film on part or all of the surface of the hydrogen storage particle.

[0018] In one embodiment, the metal hydride precursor solution may be a metal hydride or organometallic compound containing one or more metal compounds selected from the group consisting of alkali metals, alkaline earth metals, and transition metals dissolved in a solvent.

[0019] In one embodiment, the hydrogen permeation and oxidation prevention membrane solution may be a mixture of one or more of a graphene derivative selected from the group consisting of graphene oxide (GO), reduced graphene oxide (rGO), or a mixture thereof, graphitic carbon nitride, and a metal precursor, mixed in a solvent.

[0020] In one embodiment, the method may further include a step of adding a reducing agent to cause co-reduction after stirring the metal hydride precursor solution and the hydrogen permeation and oxidation prevention membrane solution.

[0021] Another object of the present invention is to provide a method for manufacturing a hydrogen storage composite, comprising the steps of: manufacturing a powdered alloy-type hydrogen storage particle; and heating the hydrogen storage particle in an oxygen or nitrogen atmosphere to form a hydrogen permeation and oxidation prevention film on part or all of the surface of the hydrogen storage particle.

[0022] In one embodiment, the alloy form is an alloy having a structure of AB5, AB2, AB, A2B, or A, wherein A is any one selected from magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr) capable of forming a hydride, and the metal B may be a transition metal.

[0023] In one aspect, the method for manufacturing the hydrogen storage composite may be to form a hydrogen permeation and oxidation prevention film on a hydrogen storage particle using a metal oxide or a metal nitride.

[0024] A hydrogen storage complex according to one aspect of the present invention can delay oxidation and performance deterioration of hydrogen storage particles due to oxidizing gas by selectively separating only hydrogen molecules through a hydrogen permeation and oxidation prevention membrane.

[0025] A hydrogen storage complex according to one aspect of the present invention can delay oxidation of hydrogen storage particles and enable continuous hydrogen storage even in a low-purity hydrogen environment.

[0026] In addition, the hydrogen permeability and oxidation prevention membrane acts as a barrier against impurity gases present in low-purity hydrogen, thereby delaying oxidation of the metal-based hydrogen storage material, thereby preserving storage performance so that continuous hydrogen storage is possible even in a low-purity hydrogen environment.

[0027] FIG. 1 is a schematic diagram of a hydrogen storage complex according to one embodiment of the present invention.

[0028] Figure 2 illustrates examples 1 to 6 according to one aspect of the present invention observed using an electron transmission microscope.

[0029] Figure 3 is a graph showing the hydrogen absorption performance of Example 1 according to one aspect of the present invention.

[0030] Figure 4 is a graph showing the hydrogen absorption performance of Example 2 according to one aspect of the present invention.

[0031] Figure 5 is a graph showing the hydrogen absorption performance of Example 3 according to one aspect of the present invention.

[0032] Figure 6 is a graph showing the hydrogen absorption performance of Example 4 according to one aspect of the present invention.

[0033] Figure 7 is a graph showing the hydrogen absorption performance of Example 5 according to one aspect of the present invention.

[0034] Figure 8 is a graph showing the hydrogen absorption performance of Example 6 according to one aspect of the present invention.

[0035] Figure 9 shows the results of observing Example 7 according to one aspect of the present invention using a scanning electron microscope, TiN x Showing the layer.

[0036] Figure 10 is a graph showing the hydrogen absorption performance of Example 7 according to one aspect of the present invention.

[0037] Figure 11 is a graph showing the hydrogen absorption performance of Example 8 according to one aspect of the present invention.

[0038] FIG. 12 is an X-ray photoelectron spectroscopy (XPS) image of a hydrogen storage composite manufactured by changing the temperature condition of the heating furnace to 500°C in Example 7 according to one aspect of the present invention.

[0039] FIG. 13 is an X-ray photoelectron spectroscopy (XPS) image of a hydrogen storage composite manufactured by changing the temperature condition of the heating furnace to 550°C in Example 7 according to one aspect of the present invention.

[0040] FIG. 14 is an X-ray photoelectron spectroscopy (XPS) image of a hydrogen storage composite manufactured by changing the temperature condition of the heating furnace to 600°C in Example 7 according to one aspect of the present invention.

[0041] The present invention will be described in more detail below. However, the following specific examples or examples are merely references for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

[0042] Additionally, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0043] Additionally, the singular forms used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0044] Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0045] Additionally, unless otherwise specifically defined in the present invention, when a layer or member is said to be “located on” another layer or member, this includes not only cases where a layer or member is in contact with another layer or member, but also cases where another layer or another member exists between the two layers or two members.

[0046] In addition, the terms “about,” “substantially,” etc. used in this specification are used in a meaning close to or at the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute values ​​are mentioned to aid in the understanding of the present invention.

[0047] Conventional hydrogen purification and storage processes have been criticized for their high energy consumption, high facility costs, and unstable storage environments. To overcome these limitations, the inventors of the present invention have developed a hydrogen storage complex that simplifies and integrates existing purification and storage processes.

[0048] The present invention provides a hydrogen storage composite comprising: a hydrogen storage particle which is a single molecular particle or an aggregate of single molecular particles made of a metal hydride; and a hydrogen permeation and oxidation prevention film formed on a part or all of the surface of the hydrogen storage particle to selectively allow hydrogen permeation and prevent oxidation of the hydrogen storage particle.

[0049] In one embodiment, the hydrogen storage particles may be single-molecule particles or aggregated particles of single-molecule particles, i.e., secondary particles, made of a metal hydride, and may have an average diameter of several nanometers (nm) to several tens of micrometers (μm). The average diameter is not limited thereto, but may be 2 to 50 μm, preferably 2 to 30 μm, and may vary depending on the type of hydrogen storage particles. For example, in the case of hydrogen storage particles of magnesium, the average diameter may be 2 to 20 nm, preferably 2 to 10 nm, and in the case of hydrogen storage particles using a TiFe-based alloy, the average diameter may be 5 to 30 μm, preferably 10 to 25 μm, but is not limited thereto. Hydrogen storage particles having the above average diameter range may have excellent hydrogen storage efficiency and may thus be preferred.

[0050] In one aspect, the metal hydride may be any metal that stably forms a hydride, such as an alkali metal, an alkaline earth metal, or a transition metal, or a metal compound composed of such metals.

[0051] The above metal hydride may include, but is not limited to, alkali metals, alkaline earth metals and transition metals that stably form hydrides, such as lithium (Li), magnesium (Mg), calcium (Ca), titanium (Ti), vanadium (V), niobium (Nb), nickel (Ni), and zirconium (Zr). In addition, the metal compound is not limited as long as it includes a metal-based hydrogen storage material, but may be an AB alloy of the TiFe series, an AB2 alloy of the TiMn2 series, an A2B alloy of the Mg2Ni series, an AB5 alloy of the LaNi5 series, etc., and examples thereof may include, but are not limited to, LaNi5, CaNi5, TiMn2, ZrMn2, ZrV2, TiFe, and Mg2Ni.

[0052] In one embodiment, the hydrogen permeation and oxidation prevention film may be made of any material that selectively allows hydrogen to pass through and prevents oxidation of the hydrogen storage particles. In addition, from the perspective of preventing oxidation of the hydrogen storage particles to enable continuous hydrogen storage, it is preferable that the surface of the hydrogen storage particles be covered with the hydrogen permeation and oxidation prevention film. That is, the “hydrogen permeation and oxidation prevention film” may be a coating layer that partially or completely covers the surface of the hydrogen storage particles and serves to selectively allow hydrogen to pass through and prevent oxidation of the hydrogen storage particles.

[0053] At this time, covering the surface of the hydrogen storage particle with the hydrogen permeability and oxidation prevention film may mean, in one embodiment, that the hydrogen storage particle is fixed between hydrogen permeability and oxidation prevention films having a layered structure, as illustrated in FIG. 1. That is, it may be preferable that the surface of the hydrogen storage particle is completely wrapped with the hydrogen permeability film. Examples of such a hydrogen permeability film may be, but are not limited to, one or a mixture of two or more selected from the group consisting of graphene derivatives including graphene oxide (GO) and reduced graphene oxide (rGO), and graphitic carbon nitride.

[0054] Another aspect of covering the surface of the hydrogen storage particle with the hydrogen permeation and oxidation prevention film may be to form a coating layer of one or more metal compounds selected from pure metals, metal oxides, and metal nitrides on the entire or part of the surface of the hydrogen storage particle.

[0055] Forming a hydrogen permeation and oxidation prevention film on “a portion” of the surface of the hydrogen storage particle may mean that 50% or more, for example, 50% or more and 99% or less of the surface area of ​​the hydrogen storage particle is formed with a coating layer of a metal compound. In addition, forming a coating layer on “all” or “entire” of the surface of the hydrogen storage particle may mean that the entire surface of the hydrogen storage particle, i.e., 100%, is formed with a hydrogen permeation and oxidation prevention film material.

[0056] The above-mentioned "hydrogen permeability and oxidation prevention membrane" can act as a selective permeability membrane for hydrogen while blocking oxidation caused by reaction with oxidizing gases. In addition, it can exhibit catalytic activity throughout the hydrogen storage process, thereby enhancing overall hydrogen storage activity. At the same time, even if a portion of the surface of the hydrogen storage particle is not coated and is oxidized by impure gases, the surrounding coating layer area can function as a channel for hydrogenation and dehydrogenation, allowing continuous hydrogen storage.

[0057] The above pure metal is not limited to any metal that can react with hydrogen, but may be, for example, palladium.

[0058] The formation of the coating layer with the above palladium may utilize a “galvanic replacement reaction.” The “galvanic replacement reaction” is a solution-based synthesis method, which is one of the oxidation / reduction reactions that occurs between solid particles in a solution and dissolved metal ions. In the process where an atom of an element with a low reduction potential donates electrons to an ion of a high element, the atom that loses an electron becomes an ion and dissolves, and the ion that received an electron is reduced to an atomic state and deposited on the metal surface. It may be a method of replacing the surface of a hydrogen storage particle with a desired material by exposing a highly reactive hydrogen storage particle to a precursor solution of a relatively low-reactivity element.

[0059] Forming a coating layer with the above metal oxide may be, for example, but is not limited to, intentionally exposing the metal-based hydrogen storage particle to an oxidizing gas environment at high temperature to form an oxide film on the surface to inhibit further oxidation.

[0060] Forming a coating layer with the above metal nitride may be, for example, but is not limited to, forming a metal-based hydrogen storage particle by heating and reacting it in a nitrogen environment to improve oxidation resistance.

[0061] In one embodiment, the hydrogen permeation and oxidation prevention membrane may be included in the hydrogen storage complex in an amount of 2 to 50 wt%, more preferably 10 to 30 wt%, but is not limited thereto, and in the above range, the hydrogen permeation membrane may be preferred because it can delay deterioration of the storage performance of hydrogen storage particles in a low-purity hydrogen environment, prevent oxidation, and improve selectivity for hydrogen permeation.

[0062] In one aspect, the hydrogen storage complex may have a capacity retention rate of 23 to 99%, or even better, 50 to 98% or more when absorbing hydrogen in a low-purity hydrogen environment.

[0063] In one aspect, the low-purity hydrogen environment may be a mixed gas having a hydrogen composition of 90% or more, for example, but not limited to, a mixed gas having a hydrogen to carbon dioxide ratio of 9:1.

[0064] Another aspect of the present invention provides a hydrogen storage complex composition comprising the hydrogen storage complex.

[0065] The above hydrogen storage complex composition may be manufactured in the form of a thin film or powder, depending on the intended use, but is not limited thereto.

[0066] Another aspect of the present invention provides a hydrogen storage method characterized by storing hydrogen in a hydrogen storage complex.

[0067] The above hydrogen storage method may include a step of physically adsorbing hydrogen onto a hydrogen storage particle, storing hydrogen by allowing the adsorbed hydrogen to be absorbed into a metal lattice structure of the hydrogen storage particle to form a compound, and releasing the stored hydrogen when needed.

[0068] In another aspect of the present invention, a method for manufacturing the hydrogen storage composite is described. The first aspect of the manufacturing method is a method for manufacturing the hydrogen storage composite using a solution reaction method, and the second aspect may be a method for manufacturing the hydrogen storage composite using a method for forming an oxide or nitride on the surface of a hydrogen storage particle. The following describes the methods for manufacturing the hydrogen storage composite of the first and second aspects, but is not limited thereto.

[0069] A first aspect of a method for manufacturing a hydrogen storage composite of the present invention provides a method for manufacturing a hydrogen storage composite, comprising: a step of manufacturing a hydrogen storage particle from a metal hydride precursor solution containing a precursor material of the hydrogen storage particle; and a step of mixing the hydrogen storage particle with a hydrogen permeation and oxidation prevention film solution to form a hydrogen permeation and oxidation prevention film on part or all of the surface of the hydrogen storage particle.

[0070] In one embodiment, the metal hydride precursor solution may be a metal hydride or an organometallic compound including a metal compound composed of all metals that stably form hydrides, such as alkali metals, alkaline earth metals, and transition metals, and transition metals that do not form hydrides. Examples thereof include, but are not limited to, biscyclopentadienyl magnesium (Bis(cyclopentadienyl) Magnesium, Mg(Cp)2), LaNi5H6, CaNi5H6, Ti 1.2 Mn 1.8 H3, ZrMn2H3, ZrV2H 4.5 , TiFeH2, Mg2NiH4, MgH2, and VH2 may be prepared by dissolving one or more compounds selected from the group consisting of in an appropriate solvent or prepared in a solid phase.

[0071] The step of manufacturing the above hydrogen storage particles may be obtained by stirring a substrate material solution in the metal precursor solution so that the metal ions are stabilized through electrostatic interaction with functional groups existing in the substrate material, and then bonding and growing the metal particles to the substrate material in the process of reducing them.

[0072] In one embodiment, the hydrogen permeation and oxidation prevention membrane solution may be prepared by mixing one or more mixtures selected from the group consisting of graphene oxide (GO), reduced graphene oxide (rGO), partially reduced graphene oxide (prGO), and graphitic carbon nitride in a solvent, and dispersing them through simple dissolution or ultrasonic treatment.

[0073] In addition, the hydrogen permeation and oxidation prevention membrane solution may be a solution in which a metal precursor is dissolved. For example, it may be a palladium precursor, and the method for forming the coating layer with palladium may be to perform a “galvanic replacement reaction” on the manufactured hydrogen storage composite using a palladium precursor solution to replace the surface of the metal compound particles of the existing hydrogen storage particles with palladium, thereby forming a coating layer.

[0074] The solvent is not limited to a solution capable of dissolving or dispersing the hydrogen permeation and oxidation prevention film material, but may be, for example, an organic solvent such as tetrahydrofuran (THF), hexane, dimethylformamide (DMF), dimethylsulfoxide (DMSO), or an ionic liquid such as butylmethylpyridinium dicyanamide (BMP-DCA).

[0075] In one embodiment, the method may further include a step of mixing the metal precursor solution and the hydrogen permeable and oxidation-preventing film solution and then adding a reducing agent to perform co-reduction.

[0076] The above reduction may be a reaction in which a metal precursor and a hydrogen permeable membrane material are simultaneously reduced by a reducing agent.

[0077] The reducing agent may be a metal ion solution, an alkali metal solution, a hydride metal ion solution, etc., and examples thereof include, but are not limited to, lithium aluminum hydride (LiAlH4), lithium naphthalenide (LiNaph), and sodium borohydride (NaBH4).

[0078] A second aspect of the method for manufacturing a hydrogen storage composite of the present invention provides a method for manufacturing a hydrogen storage composite, comprising: a step of manufacturing a hydrogen storage particle in a powdered alloy form; and a step of heating the hydrogen storage particle in an oxygen or nitrogen atmosphere to form a hydrogen permeation and oxidation prevention film on part or all of the surface of the hydrogen storage particle.

[0079] In one embodiment, the alloy form is an alloy form having a structure of AB5, AB2, AB, A2B, A, wherein A may be a metal such as Mg, Ca, Ti, Zr, etc. capable of forming a hydride, and B may be a transition metal, and examples thereof may include, but are not limited to, alloys such as LaNi5, CaNi5, TiMn2, ZrMn2, ZrV2, TiFe, Mg2Ni, etc.

[0080] In one aspect, the method for manufacturing the hydrogen storage composite may be to form a hydrogen permeation and oxidation prevention film, i.e., a coating layer, on the surface of a hydrogen storage particle using a metal oxide or a metal nitride.

[0081] The method for forming a coating layer with the above metal oxide and metal nitride may be a method for forming a coating layer by heating the manufactured hydrogen storage particle at a very high temperature under an oxidizing gas or nitrogen gas, and for example, a “high-temperature impact method” may be used, which can heat to a very high temperature in a short period of time by utilizing a phenomenon in which Joule heating occurs due to the resistance of a material in a process in which a strong current is momentarily applied.

[0082] For example, the method for forming the metal nitride film may be to heat a hydrogen storage material including titanium (Ti) to a high temperature to form a titanium nitride (TiNx) layer on the surface, which functions as a hydrogen permeation and oxidation prevention film. At this time, the pressure of nitrogen during heating may be adjusted to 0.05 to 1 bar, the heating temperature to 300 to 1000°C, and the heating time to 30 minutes to 5 hours, thereby forming titanium nitride layers of various thicknesses, but is not limited thereto. For example, a titanium nitride layer formed by heating for 30 minutes under conditions of 0.1 bar pressure and 600°C heating temperature may be formed to a thickness of 300 to 350 nm, and a titanium nitride layer formed by heating for 30 minutes under conditions of 0.1 bar pressure and 550°C heating temperature may be formed to have an even thinner thickness. The thickness of the above titanium nitride layer can generally be formed to be several nanometers to several hundred nanometers thick, and can be formed to be 10 to 800 nm, 50 to 500 nm, or 100 to 400 nm depending on the heating conditions, but is not limited thereto.

[0083] The above “galvanic replacement reaction” and “high-temperature impact method” are preferred because they can form a hydrogen permeable and oxidation-preventing film relatively simply, but are not limited thereto.

[0084] The present invention will be described in more detail based on the following examples. However, the following examples are merely illustrative examples for further explaining the present invention, and the present invention is not limited to the following examples.

[0085] [measurement method]

[0086] 1. Measurement of the average diameter of hydrogen storage particles

[0087] The manufactured hydrogen storage particles were dispersed in THF, applied to Lacey / Carbon 300 Mesh Cu, and dried to prepare grids. The average diameter size was measured by observing transmission electron images using a transmission electron microscope (Tecnai G2 F20, FEI company) with an accelerating voltage of 300 kV.

[0088] 2. Evaluation of hydrogen absorption performance of hydrogen storage complexes

[0089] To evaluate hydrogen absorption performance in pure hydrogen and mixed gas environments, we first performed a hydrogen performance evaluation in a pure hydrogen environment, followed by measurements in a mixed gas environment with a hydrogen to carbon dioxide ratio of 9:1. Measurements were performed using a Sievert-type volume-based gas storage capacity measuring device, as detailed below. First, 80 mg of a powdered hydrogen storage complex was placed in a 2 ml cylindrical stainless steel cell and connected to a high-pressure volumetric analyzer (HPVA, Micromeritics). The sample cell was placed in a furnace connected to the device to control temperature. After connection, vacuum and helium (He) gas purges were repeated to remove impurities from the gas lines within the device. The lines and cell were then filled with He gas, and pressure changes within the lines and cell were checked to ensure no gas leaks at each connection point. Volume calibration was then performed to measure the apparent volume within the cell at the measurement temperature. For the hydrogen absorption performance evaluation, in the case of pure hydrogen, gas was injected so that the pressure applied to the sample at the start of the measurement was 15 bar under temperature conditions of 200 °C, and in the case of mixed gas (H2: CO2= 9:1), a mixed gas of approximately 16.7 bar was injected so that the partial pressure of pure hydrogen was 15 bar. Afterwards, the sample was exposed for at least 6 hours in a closed system, and the hydrogen absorption amount was calculated based on the change in gas pressure inside the cell. Afterwards, the hydrogen release was performed by heating the cell to 300 °C and exposing the sample to an environment of 0.02 bar for at least 12 hours, and the release amount was calculated by measuring the change in pressure as in the absorption process.The hydrogen storage capacity was measured by calculating the number of moles of hydrogen absorbed by substituting the pressure change during measurement, the volume of the cell and reservoir, and the measured temperature values ​​into the ideal gas equation of state.

[0090] The hydrogen storage capacity preservation rate in a low-purity hydrogen environment compared to a pure hydrogen environment can be calculated as (hydrogen storage capacity after 6 hours of starting hydrogen storage in a mixed gas environment) / (hydrogen storage capacity after 6 hours of starting hydrogen storage in a pure hydrogen environment) * 100 (%). By comparing the results from the first mixed gas environment measurement after the pure hydrogen environment measurement, the value of 'Hydrogen storage capacity preservation rate (%) in a low-purity hydrogen environment compared to a pure hydrogen environment (first step)' can be obtained. After dehydrogenation is performed, the results of the re-measurement of storage performance in a mixed gas environment can be calculated as above, and the value of 'Hydrogen storage capacity preservation rate (%) in a low-purity hydrogen environment compared to a pure hydrogen environment (second step)' can be obtained. This is used as a measure of hydrogen storage performance preservation in a mixed gas environment.

[0091] [Example 1]

[0092] 1. Manufacturing of hydrogen storage complexes

[0093] Lithium naphthalenide reducing agent is prepared by adding 1.152 g (8.99 mmol) of naphthalene and 0.0864 g (12.4 mmol) of lithium foil in metallic form to 57.6 ml of THF and stirring at 300 rpm for 2 hours. A magnesium (Mg) precursor solution was prepared by dissolving 0.664 M (0.924 g (5.98 mmol) of MgCp2 / 9 ml of THF) of biscyclopentadienyl magnesium (Bis(cyclopentadienyl) Magnesium, Mg(Cp)2) in tetrahydrofuran (THF) with stirring at 300 rpm for 30 minutes, and a single-layer graphene oxide (GO) powder was ultrasonically dispersed in a THF solvent at a concentration of 36.3 mg GO / 36.3 ml of THF for 1 hour and 30 minutes to prepare a graphene oxide dispersion. The magnesium precursor solution and graphene oxide dispersion were stirred at 300 rpm for 30 minutes to form electrostatic interactions between the oxygen functional groups of the graphene oxide layer and magnesium ions, and then the graphene oxide-magnesium (GO-Mg) precursor solution was added to the prepared lithium naphthalenide solution to perform co-reduction. The obtained material was washed three or more times with a THF solvent and centrifuged to remove impurities or unreacted substances, and then dried in a vacuum environment to produce a hydrogen storage composite (rGO / Mg).

[0094] 2. Formation of hydrogen storage particle coating layer

[0095] The hydrogen storage composite manufactured above was added to a palladium precursor solution containing 2.23 mM Pd(OAc)2 dissolved in THF, and then sufficiently stirred at 500 rpm for 30 minutes. At this time, the concentration of the palladium precursor solution was such that the mass ratio of the hydrogen storage composite: Pd(OAc)2 was 2:1, and the volume of the THF solvent was 1 ml per 1 mg of the hydrogen storage composite. Specifically, 70 mg of hydrogen storage composite (rGO20 / Mg) powder and 35 mg of Pd(OAc)2 powder were dissolved in 70 ml of THF solvent. Afterwards, the obtained material was washed and centrifuged three or more times with THF to remove impurities or unreacted substances, and then dried to manufacture a hydrogen storage composite in which a palladium (Pd) coating layer was formed on the surface of magnesium particles in an rGO / Mg composite containing 20 wt% of reduced graphene oxide.

[0096] [Example 2]

[0097] A hydrogen storage composite was prepared in the same manner as in Example 1, except that graphene oxide was dispersed in a THF solvent at 16.3 mg GO / 16.3 ml THF. A hydrogen storage composite was prepared in which a palladium (Pd) coating layer was formed on the surface of the Mg particles in the rGO / Mg composite containing 10 wt% of reduced graphene oxide.

[0098] [Example 3]

[0099] The same procedure as in Example 1 was followed, except that graphene oxide was dispersed in a THF solvent at a concentration of 2.5 mg GO / 5 ml THF, the concentration of the lithium naphthalenide solution was not changed, and the volume was reduced to 5 / 6. A hydrogen storage composite was prepared in which a palladium (Pd) coating layer was formed on the surface of the Mg particles in the rGO / Mg composite containing 2 wt% of reduced graphene oxide.

[0100] [Example 4]

[0101] A hydrogen storage composite was manufactured in the same manner as in Example 1 above, except that the coating layer formation step was not performed. A hydrogen storage composite was manufactured in which a palladium (Pd) coating layer was not formed on the surface of the Mg particles in the rGO / Mg composite containing 20 wt% of reduced graphene oxide.

[0102] [Example 5]

[0103] In the above Example 1, the coating layer formation step was not performed, and the graphene oxide was dispersed in a THF solvent at 16.3 mg GO / 16.3 ml THF, and the same procedure was followed, except that a hydrogen storage composite was prepared in which a palladium (Pd) coating layer was not formed on the surface of the Mg particles in the rGO / Mg nanocomposite containing 10 wt% of reduced graphene oxide.

[0104] [Example 6]

[0105] In the above Example 1, the coating layer formation step was not performed, and the same procedure was followed except that the graphene oxide was dispersed in a THF solvent (2.5 mg GO / 5 ml THF) and the concentration of the lithium naphthalenide solution was not changed but the volume was reduced to 5 / 6. A hydrogen storage composite was prepared in which a palladium (Pd) coating layer was not formed on the surface of the Mg particles in the rGO / Mg composite including 2 wt% of reduced graphene oxide.

[0106] [Example 7]

[0107] Fabrication of a hydrogen storage composite with a metal nitride coating layer

[0108] TiFe, an AB hydrogen storage alloy containing titanium 0.8 Cr 0.2The alloy particles are powdered by repeating a total of five cycles, with one cycle of hydrogen absorption in a room temperature hydrogen 40 bar environment and one cycle of hydrogen release in a 150 degree 0 bar environment. The hydrogen storage particles in the form of an alloy powdered by the above method have an average diameter of 10 μm. The alloy powder is put into a quartz tube with a nitrogen pressure of 0.1 bar, placed in a furnace heated to 650°C, heated for 30 minutes, and then the nitrogen is removed and cooled to room temperature in a vacuum atmosphere to obtain TiFe with a surface coated with titanium nitride. 0.8 Cr 0.2 A hydrogen storage complex was manufactured.

[0109] At this time, the temperature conditions of the above-mentioned heating furnace were changed to 500 ℃, 550 ℃, and 600 ℃, and hydrogen storage composites were manufactured respectively, and the thickness of the titanium nitride layer on the surface of the hydrogen storage composite was comparatively analyzed using X-ray photoelectron spectroscopy (XPS) images, as shown in FIGS. 12 to 14.

[0110] [Example 8]

[0111] A hydrogen storage composite was manufactured in the same manner as in Example 7, except that the alloy powder was heated in a furnace heated to 550°C. TiFe coated with titanium nitride having a thinner thickness than that of Example 7 0.8 Cr 0.2 A hydrogen storage complex was manufactured.

[0112] Table 1 below shows the measured values ​​of the physical properties of Examples 1 to 8.

[0113] Average diameter Hydrogen storage capacity preservation rate (%) in low-purity hydrogen environment compared to pure hydrogen environment (first stage) Hydrogen storage capacity preservation rate (%) in low-purity hydrogen environment compared to pure hydrogen environment (second stage) Example 15 nm 98.0% 39.9% Example 25 nm 90.4% 37.4% Example 35 nm 80.6% 25.9% Example 45 nm 75.1% 20.2% Example 55 nm 76.3% 5.21% Example 65 nm 23.0% 1.11% Example 710 μm 94.4% 77.3% Example 810 μm 103% 98.9%

[0114] Figure 2 shows transmission electron microscopy (TEM) images of Examples 1 to 6, confirming that magnesium crystals, which are hydrogen storage particles, were formed with a size of 3 to 5 nm on the reduced graphene oxide layer. In addition, the TEM observation results of Examples 1 to 3 show that darker particles were formed compared to the hydrogen storage complex crystals of Examples 4 to 6. This may be a phenomenon resulting from the formation of a coating layer of palladium, which has a higher electron density than magnesium.

[0115] As seen in FIGS. 3 to 5, it was confirmed that the hydrogen storage composites of Examples 1 to 3 continuously stored hydrogen even when exposed to a low-purity hydrogen environment. This may be due to the formation of a palladium coating layer on the hydrogen storage particles, thereby forming hydrogenation and dehydrogenation channels and simultaneously improving the oxidation resistance of the hydrogen storage particles. Accordingly, the palladium coating layer may also function as a selective permeable membrane for hydrogen.

[0116] As shown in Figures 6 to 8, it was confirmed that the degree of performance preservation of the hydrogen storage composite further increased as the content of reduced graphene oxide (rGO) included in the hydrogen storage composite increased. This may be because the structure of the layered rGO extends the diffusion distance of impurity gases such as carbon dioxide and further enhances hydrogen permeation selectivity, thereby delaying oxidation of the hydrogen storage particles and enabling sustained hydrogen storage.

[0117] Figure 9 is a scanning electron microscope (SEM) image of the hydrogen storage composite of Example 7, confirming that a titanium nitride layer (dark portion) was evenly formed on the particle surface after heating.

[0118] Referring to Figure 10, it was confirmed that the hydrogen storage composite of Example 7 maintained approximately 80% of its storage capacity despite being exposed to a low-purity hydrogen environment. This phenomenon may be due to the titanium nitride layer uniformly coated on the surface selectively permeating only hydrogen.

[0119] In Fig. 11, the results of the repeated storage performance evaluation of the hydrogen storage composite of Example 8 in a low-purity hydrogen environment show that even after four repetitions, a storage capacity of 98.9%, which is higher than that of the hydrogen storage composite of Example 7 of Fig. 10, is continuously maintained, and it is confirmed that the storage speed does not continuously deteriorate and reaches a certain threshold. This may be because a titanium nitride layer of a certain thickness has optimized hydrogen selectivity in a low-purity environment.

[0120] Figures 12 to 14 are X-ray photoelectron spectroscopy (XPS) images of hydrogen storage composites synthesized by changing only the heating temperature to 500, 550, and 600°C in Example 7, respectively, and it was confirmed that the titanium nitride layer on the surface increased as the heating temperature increased.

[0121] As described above, the present invention has been described through specific matters and limited examples, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0122] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the following claims as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. Hydrogen storage particles which are single molecular particles or aggregated particles of single molecular particles made of metal hydride; and A hydrogen storage composite comprising a hydrogen permeable and oxidation-preventing film formed on part or all of the surface of the hydrogen storage particle to selectively allow hydrogen permeation and prevent oxidation of the hydrogen storage particle.

2. In paragraph 1, A hydrogen storage composite wherein the above hydrogen permeation and oxidation prevention film is selected from the group consisting of graphene oxide (GO), reduced graphene oxide (rGO), a graphene derivative including one or a mixture thereof; graphitic carbon nitride; and one or more metal compounds selected from the group consisting of metal oxides, metal nitrides, and pure metals.

3. In paragraph 1, A hydrogen storage complex wherein the hydrogen permeation and oxidation prevention film is included in the hydrogen storage complex at 2 to 50 wt%.

4. In paragraph 1, A hydrogen storage complex wherein the above metal hydride is one or more metal compounds selected from the group consisting of alkali metals, alkaline earth metals, and transition metals.

5. In paragraph 1, A hydrogen storage composite wherein the above hydrogen storage particles have an average diameter of 2 nm to 50 μm.

6. In paragraph 1, The above hydrogen storage complex is a hydrogen storage complex having a capacity retention rate of 23% or more when absorbing hydrogen in a low-purity hydrogen environment.

7. In paragraph 6, The above low-purity hydrogen environment is a hydrogen storage complex in which the composition of hydrogen in the mixed gas is 90% or more.

8. A hydrogen storage complex composition comprising a hydrogen storage complex selected from any one of claims 1 to 7.

9. A hydrogen storage method characterized by storing hydrogen in a hydrogen storage complex selected from any one of claims 1 to 7.

10. A step of manufacturing a hydrogen storage particle from a metal hydride precursor solution containing a precursor material of a hydrogen storage particle; and A method for manufacturing a hydrogen storage complex, comprising: a step of mixing the hydrogen storage particles with a hydrogen permeability and oxidation prevention film solution to form a hydrogen permeability and oxidation prevention film on part or all of the surface of the hydrogen storage particles.

11. In paragraph 10, A method for manufacturing a hydrogen storage complex, wherein the metal hydride precursor solution is a metal hydride or organometallic compound containing one or more metal compounds selected from the group consisting of alkali metals, alkaline earth metals, and transition metals, dissolved in a solvent.

12. In paragraph 10, A method for manufacturing a hydrogen storage composite, wherein the above hydrogen permeation and oxidation prevention membrane solution is a mixture of one or more of a graphene derivative selected from the group consisting of graphene oxide (GO), reduced graphene oxide (rGO), or a mixture thereof, graphitic carbon nitride, and a metal precursor, mixed in a solvent.

13. In paragraph 10, A method for manufacturing a hydrogen storage complex, further comprising a step of adding a reducing agent to cause co-reduction after stirring the metal hydride precursor solution and the hydrogen permeability and oxidation prevention membrane solution.

14. A step for manufacturing hydrogen storage particles in the form of a powdered alloy; and A method for manufacturing a hydrogen storage composite, comprising: a step of heating the hydrogen storage particles in an oxygen or nitrogen atmosphere to form a hydrogen permeation and oxidation prevention film on part or all of the surface of the hydrogen storage particles.

15. In paragraph 14, The above alloy form is AB 5 , AB 2 , AB, A 2 A method for manufacturing a hydrogen storage composite, wherein the alloy has a B, A structure, wherein A is any one selected from magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr) capable of forming a hydride, and metal B is a transition metal.

16. In paragraph 14, The above method for manufacturing a hydrogen storage composite is a method for manufacturing a hydrogen storage composite, which forms a hydrogen permeation and oxidation prevention film on a hydrogen storage particle using a metal oxide or a metal nitride.

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