KR20250081665A - Hydrogen storage composite and its manufacturing method for low-purity hydrogen storage - Google Patents

Abstract

The present invention relates to a hydrogen storage complex and a method for manufacturing the same. More specifically, the hydrogen storage complex of the present invention is a complex in which a hydrogen-permeable and oxidation-preventing membrane, which selectively separates only hydrogen molecules, surrounds a hydrogen storage particle, and a conventional hydrogen purification process and a storage process are integrated. The hydrogen storage complex can prevent oxidation and performance deterioration of the hydrogen storage particle due to an oxidizing gas, and even in a low-purity hydrogen environment, the oxidation of the hydrogen storage particle is delayed and hydrogen can be continuously stored.

Description

Hydrogen storage composite and its manufacturing method for low-purity hydrogen storage

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

Hydrogen has a chemical energy density that is about three times higher than that of general hydrocarbons, and is considered a highly efficient clean energy source that does not generate any other gases except water during the energy production stage. Since this hydrogen is generally combined with 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 in two major ways: using the pressure-swing adsorption method or the palladium-based hydrogen separation membrane. However, the pressure-swing adsorption method requires large facilities to perform a complex separation process, and consumes a lot of energy during the operation process. In addition, even when using a palladium-based hydrogen separation membrane, there is a problem that the energy consumption is very high to maintain a high temperature and high pressure environment, and the palladium separation membrane, which is a high-cost material, must be replaced periodically. In order to improve the accessibility of hydrogen energy, not only the above-mentioned purification process but also the current hydrogen storage method needs to be improved. The existing physical hydrogen storage method is a compression and liquefaction method. The compression method requires harsh conditions of up to 700 bar and the liquefaction method requires harsh conditions of -253℃ or lower, so the energy consumed for storage is very large. Therefore, in order to advance the commercialization of hydrogen energy, the limitations of the existing purification and storage methods must be improved to increase the utility of hydrogen energy.

Korean Patent Publication No. 10-2023-0168497 (2023.12.14)

According to one aspect of the present invention, it is an object to provide a hydrogen storage composite comprising hydrogen storage particles of metal hydride and a hydrogen-permeable and oxidation-preventing film covering the hydrogen storage particles, which exhibits selective hydrogen permeability and prevents oxidation of the hydrogen storage particles.

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 problems with conventional physical storage methods.

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 problems with conventional hydrogen purification and storage technologies.

According to another aspect of the present invention, an object is to provide a method for manufacturing the hydrogen storage complex.

The inventors of the present invention have conducted research to overcome the limitations of conventional hydrogen purification and storage processes, and as a result, have developed a new hydrogen storage composite 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 composite can improve the problems of conventional technologies by allowing the purification and storage processes to be integrated, thereby completing the present invention.

The present invention provides a hydrogen storage composite including: 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 which is formed on part or all of the surface of the hydrogen storage particle to selectively allow hydrogen to pass through and prevent oxidation of the hydrogen storage particle.

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.

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

In one embodiment, 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.

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

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.

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.

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

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

In one aspect, another object is to provide a method for producing a hydrogen storage composite, comprising: a step of producing a hydrogen storage particle from a metal hydride precursor solution including a precursor material of the hydrogen storage particle; and a step of 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.

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.

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.

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

Another object of the present invention is to provide a method for manufacturing a hydrogen storage composite, including the steps of manufacturing a powdered alloy-type hydrogen storage particle; and the 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.

In one embodiment, the alloy form is an alloy having a structure of AB ₅ , AB ₂ , AB, A ₂ B, 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.

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.

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

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.

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.

FIG. 1 is a schematic diagram of a hydrogen storage complex according to one embodiment of the present invention.
FIG. 2 illustrates examples 1 to 6 according to one aspect of the present invention observed using an electron transmission microscope.
Figure 3 is a graph showing the hydrogen absorption performance of Example 1 according to one aspect of the present invention.
Figure 4 is a graph showing the hydrogen absorption performance of Example 2 according to one aspect of the present invention.
Figure 5 is a graph showing the hydrogen absorption performance of Example 3 according to one aspect of the present invention.
Figure 6 is a graph showing the hydrogen absorption performance of Example 4 according to one aspect of the present invention.
Figure 7 is a graph showing the hydrogen absorption performance of Example 5 according to one aspect of the present invention.
Figure 8 is a graph showing the hydrogen absorption performance of Example 6 according to one aspect of the present invention.
Figure 9 is a diagram illustrating Example 7 according to one aspect of the present invention observed using a scanning electron microscope.
Figure 10 is a graph showing the hydrogen absorption performance of Example 7 according to one aspect of the present invention.

Hereinafter, the present invention will be described in more detail. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of this invention is only for the purpose of effectively describing particular embodiments and is not intended to be limiting of the invention.

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.

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.

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 member exists between the two layers or two members.

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

The conventional hydrogen purification and storage process has been criticized for its high energy consumption, high cost of facilities, and instability of the storage environment. In order to overcome the limitations of the above hydrogen purification and storage process, the inventors of the present invention have invented a hydrogen storage complex in which the conventional purification and storage process is simplified and integrated.

The present invention provides a hydrogen storage composite including: 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 which is formed on part or all of the surface of the hydrogen storage particle to selectively allow hydrogen to pass through and prevent oxidation of the hydrogen storage particle.

In one embodiment, the hydrogen storage particles may be single molecular particles or aggregated particles of single molecular particles, i.e. secondary particles, made of a metal hydride, and may have an average diameter of several nanometers (nm) to tens of micrometers (μm). The average diameter is not limited thereto, but may be 2 nm to 50 μm, more preferably 2 nm to 30 μm, and may vary depending on the type of the hydrogen storage particles. For example, in the case of hydrogen storage particles made 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 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 thus may be preferred.

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, and a metal compound composed of such metals.

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), 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 AB ₂ alloy of the TiMn ₂ series, an A ₂ B alloy of the Mg ₂ Ni series, an AB ₅ alloy of the LaNi ₅ series, etc., and examples thereof may include, but are not limited to, LaNi ₅ , CaNi ₅ , TiMn ₂ , ZrMn ₂ , ZrV ₂ , TiFe, Mg ₂ Ni, etc.

In one embodiment, the hydrogen permeation and oxidation prevention film may be used without limitation as long as it is a material that selectively allows hydrogen to pass through and prevents oxidation of the hydrogen storage particle. In addition, from the viewpoint of preventing oxidation of the hydrogen storage particle to enable continuous hydrogen storage, it is preferable that the surface of the hydrogen storage particle 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 particle and plays a role in selectively allowing hydrogen to pass through and preventing oxidation of the hydrogen storage particle.

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 hydrogen permeability films may include, 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.

Another aspect of covering the surface of the hydrogen storage particle with the hydrogen permeability 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 all or part of the surface of the hydrogen storage particle.

Forming a hydrogen permeable and oxidation-preventing 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 permeable and oxidation-preventing film material.

The above “hydrogen permeation and oxidation prevention film” can block oxidation caused by reaction with oxidizing gas while performing the role of a selective permeation film for hydrogen. In addition, since it can exhibit catalytic activity throughout the hydrogen storage process, it can improve the overall hydrogen storage activity, and at the same time, even if a part of the surface of the hydrogen storage particle is not formed with a coating layer and is oxidized by an impure gas, the surrounding coating layer area can perform the role of a channel for hydrogenation and dehydrogenation, so that continuous hydrogen storage can proceed.

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

The formation of the coating layer with the above palladium may utilize a “galvanic substitution reaction.” The above “galvanic substitution reaction” is a solution-based synthetic method, which is one of the oxidation/reduction reactions that occurs between solid particles in a solution and dissolved metal ions. In the process in which 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 the electron is reduced to an atomic state and deposited on the metal surface. It may be a method to replace 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.

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 conditions to form an oxide film on the surface to inhibit further oxidation.

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

In one embodiment, the hydrogen permeation and oxidation prevention membrane may be included in the hydrogen storage composite in an amount of, but not limited to, 2 to 50 wt%, more preferably 10 to 30 wt%, 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.

In one embodiment, 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.

In one embodiment, 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 ratio of hydrogen to carbon dioxide of 9:1.

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

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.

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

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.

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 methods for manufacturing the hydrogen storage composite of the first aspect and the second aspect are described below, but are not limited thereto.

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 including a precursor material of the hydrogen storage particle; and a step of 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.

In one embodiment, the metal hydride precursor solution may be a metal hydride or 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. For example, but not limited to, dicyclopentadienyl magnesium (Mg(Cp) ₂ ), LaNi ₅ H ₆ , CaNi ₅ H ₆ , Ti _{1.2 Mn 1.8 H 3} , ZrMn 2 H ₃ , ZrV _{2 H 4.5} , TiFeH ₂ , Mg ₂ NiH ₄ , MgH ₂ , and VH _{2 ,} may be prepared by dissolving any one or two or more compounds selected from the group consisting of, in an appropriate solvent, or prepared in a solid phase.

The step of manufacturing the above hydrogen storage particles may be achieved 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 the metal ions.

In one embodiment, the hydrogen permeation and oxidation prevention membrane solution is prepared by mixing one or more 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 the mixture through simple dissolution or ultrasonic treatment.

In addition, the hydrogen permeation and oxidation prevention film 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 a coating layer with palladium may be to form a coating layer by performing a “galvanic substitution 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.

The solvent is not limited to any solution capable of dissolving or dispersing the hydrogen permeable and oxidation-preventing membrane material, but may be, for example, an organic solvent such as tetrahydrofuran (THF), hexane, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or an ionic liquid such as butylmethylpyridinium dicyanamide (BMP-DCA).

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 cause reduction.

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.

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 (LiAlH ₄ ), lithium naphthalenide (LiNaph), and sodium borohydride (NaBH ₄ ).

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 powdered alloy-type hydrogen storage particle; 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.

In one embodiment, the alloy form is an alloy form having a structure of AB ₅ , AB ₂ , AB, A ₂ B, A, wherein A may be a metal such as Mg, Ca, Ti, or Zr 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 LaNi ₅ , CaNi ₅ , TiMn ₂ , ZrMn ₂ , ZrV ₂ , TiFe, and Mg ₂ Ni.

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.

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 that can heat to a very high temperature for a short period of time by utilizing a phenomenon in which Joule heating is generated due to the resistance of a material in a process in which a strong current is momentarily passed.

For example, a method for forming the metal nitride film may be to heat a hydrogen storage material including titanium (Ti) at a high temperature to form a titanium nitride (TiNx) layer on the surface, thereby functioning as a hydrogen permeation and oxidation prevention film.

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.

The present invention will be described in more detail based on the following examples. However, the following examples are only examples for describing the present invention in more detail, and the present invention is not limited to the following examples.

[measurement method]

1. Measurement of the average diameter size of hydrogen storage particles

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

2. Evaluation of hydrogen absorption performance of hydrogen storage complex

In order to evaluate the hydrogen absorption performance in pure hydrogen and mixed gas environments, the hydrogen performance evaluation in the pure hydrogen environment was conducted, and then measurements were also conducted in the mixed gas environment where the ratio of hydrogen and carbon dioxide was 9:1. The measurements were conducted using a Sievert type volume-based gas storage capacity measuring device, and the detailed method is as follows. First, 80 mg of a powdered hydrogen storage complex is placed in a cylindrical stainless steel cell with a volume of 2 ml, and then connected to a high pressure volumetric analyzer (HPVA, Micromeritics) device. At this time, the sample cell part can be placed in a furnace connected to the device to control the temperature. After connection, vacuum and helium (He) gas purge are repeated to remove impure gases in the gas line inside the device. After that, helium gas is filled in the line and cell, and the absence of gas leakage at each connecting part is checked through the pressure change in the line and cell. After that, volume calibration is performed to measure the apparent volume in the cell at the measurement temperature. For the evaluation of hydrogen absorption performance, gas was injected so that the pressure applied to the sample at the start of the measurement was 15 bar at a temperature condition of 200 °C for pure hydrogen, and the mixed gas (H ₂ : CO ₂ = 9 : 1) was injected so that the partial pressure of pure hydrogen was 15 bar. After that, 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. Thereafter, the hydrogen release was performed by heating the cell to 300 °C and exposing the sample to an environment of 0.02 bar for 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 moles (mol) of hydrogen absorbed by substituting the pressure change during the measurement, the volume of the cell and reservoir, and the measurement temperature values into the ideal gas state equation.

The hydrogen storage capacity preservation rate in a low-purity hydrogen environment compared to a pure hydrogen environment was calculated as (hydrogen storage capacity after 6 hours from the start of hydrogen storage in a mixed gas environment)/(hydrogen storage capacity after 6 hours from the start of hydrogen storage in a pure hydrogen environment)*100(%). The results of the first mixed gas environment measurement after the pure hydrogen environment measurement were compared to obtain the 'Hydrogen storage capacity preservation rate (%) in a low-purity hydrogen environment compared to a pure hydrogen environment (first stage)' value. After dehydrogenation was performed, each result of the re-measurement of storage performance in a mixed gas environment was calculated as above to obtain the 'Hydrogen storage capacity preservation rate (%) in a low-purity hydrogen environment compared to a pure hydrogen environment (second stage)' value. This was used as a measure of hydrogen storage performance preservation in a mixed gas environment.

[Example 1]

1. Manufacturing of hydrogen storage complex

Lithium naphthalenide reducing agent was 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. Dicyclopentadienyl magnesium (Mg(Cp) ₂ ) was dissolved in tetrahydrofuran (THF) at a concentration of 0.664 M (0.924 g (5.98 mmol) of MgCp2 _/ 9 ml of THF) with stirring at 300 rpm for 30 minutes to prepare a magnesium (Mg) precursor solution, and single layer graphene oxide (GO) powder was ultrasonically dispersed in THF solvent at a concentration of 36.3 mg GO/36.3 ml THF for 1 hour and 30 minutes to prepare a graphene oxide dispersion. The magnesium precursor solution and the graphene oxide dispersion were stirred at 300 rpm for 30 minutes to form an electrostatic interaction between the oxygen functional groups of the graphene oxide layer and the 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).

2. Formation of hydrogen storage particle coating layer

After the above-mentioned manufactured hydrogen storage composite was added to a palladium precursor solution containing 2.23 mM Pd(OAc) ₂ dissolved in THF, the mixture was 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.

[Example 2]

The same procedure as in Example 1 was followed, except that graphene oxide was dispersed in a THF solvent of 16.3 mg GO/16.3 ml THF. A hydrogen storage composite was prepared in which a palladium coating layer was formed on the surface of the magnesium particles in the rGO/Mg composite containing 10 wt% of reduced graphene oxide.

[Example 3]

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

[Example 4]

A hydrogen storage composite was manufactured in the same manner as in Example 1 except that the coating layer formation step was not performed. A hydrogen storage composite was manufactured in which a palladium coating layer was not formed on the surface of the magnesium particles in the rGO/Mg composite including 20 wt% of reduced graphene oxide.

[Example 5]

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

[Example 6]

In the above Example 1, the coating layer formation step was not performed, and 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 capacity was reduced to 5/6, and the same procedure was followed, except that the hydrogen storage composite was produced in which a palladium coating layer was not formed on the surface of the magnesium particles in the rGO/Mg composite including 2 wt% of reduced graphene oxide.

[Example 7]

Fabrication of hydrogen storage composite with metal nitride coating layer formed

TiFe _0.8 Cr _0.2 , an AB hydrogen storage alloy containing titanium, is powdered into alloy particles by repeating five cycles of hydrogen absorption in a room temperature and hydrogen 40 bar environment and hydrogen release in a 150 degree and 0 bar environment as one cycle. The hydrogen storage particles in the form of an alloy powdered by the above method have an average diameter of 20 μm. The alloy powder is put into a quartz tube with a nitrogen pressure of 0.1 bar, placed in a heating 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 produce a TiFe _0.8 Cr _0.2 hydrogen storage composite having a surface coated with titanium nitride. At this time, by controlling the nitrogen pressure during heating between 0.1 and 1 bar, the temperature between 650 and 800 °C, and the heating time between 1 and 3 hours, it is possible to produce titanium nitride layers of various thicknesses.

Table 1 below shows the measured values of the physical properties of Examples 1 to 7.

Average diameter Low purity hydrogen environment compared to pure hydrogen environment
Hydrogen storage capacity preservation rate (%)
(First step) Hydrogen storage capacity preservation rate (%) in low-purity hydrogen environment compared to pure hydrogen environment
(Second step) Example 1 5 nm 98.0% 39.9% Example 2 5 nm 90.4% 37.4% Example 3 5 nm 80.6% 25.9% Example 4 5 nm 75.1% 20.2% Example 5 5 nm 76.3% 5.21% Example 6 5 nm 23.0% 1.11% Example 7 20 μm 94.4% 77.3%

Figure 2 shows the results of observing Examples 1 to 6 using a transmission electron microscope (TEM), and it was confirmed 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 showed that darker particles were formed compared to the hydrogen storage complex crystals of Examples 4 to 6. This may be a phenomenon caused by the formation of a coating layer of palladium, which has a higher electron density than magnesium.

As seen in FIGS. 3 to 5, it was confirmed that hydrogen storage was continuously performed even when the hydrogen storage composites of Examples 1 to 3 were exposed to a low-purity hydrogen environment. This may be because hydrogenation and dehydrogenation channels were formed by forming a palladium coating layer on the hydrogen storage particles, while at the same time improving the oxidation resistance of the hydrogen storage particles. Accordingly, the palladium coating layer may also function as a selective permeable membrane for hydrogen.

As seen in FIGS. 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 impure gases such as carbon dioxide and further improves hydrogen permeation selectivity, thereby delaying the oxidation of the hydrogen storage particles and enabling continuous hydrogen storage.

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.

As shown in Fig. 10, it was confirmed that the hydrogen storage composite of Example 7 continuously maintained about 80% of the storage capacity even when exposed to a low-purity hydrogen environment. This may be a phenomenon that occurred because the titanium nitride layer uniformly coated on the surface selectively allowed only hydrogen to pass through.

Although the present invention has been described through specific matters and limited examples as described above, these have been 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 from this description.

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 claims described below as well as the claims are included in the scope of the idea of the present invention.

Claims (16)

Hydrogen storage particles which are single molecular particles or aggregates 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. 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 two or more metal compounds selected from the group consisting of metal oxides, metal nitrides, and pure metals. 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%. In paragraph 1,
A hydrogen storage complex wherein the metal hydride is one or more metal compounds selected from the group consisting of alkali metals, alkaline earth metals, and transition metals. In paragraph 1,
A hydrogen storage composite wherein the above hydrogen storage particles have an average diameter of 2 nm to 50 μm. 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. 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. A hydrogen storage complex composition comprising a hydrogen storage complex selected from any one of claims 1 to 7. A hydrogen storage method characterized by storing hydrogen in a hydrogen storage complex selected from any one of claims 1 to 7. 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 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. In Article 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. In Article 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. In Article 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. A step for manufacturing hydrogen storage particles in the form of a powdered alloy; and
A method for manufacturing a hydrogen storage complex, 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. In Article 14,
A method for manufacturing a hydrogen storage complex, wherein the above alloy form is an alloy having a structure of AB ₅ , AB ₂ , AB, A ₂ B, A, wherein A is one selected from magnesium (Mg), calcium (Ca), titanium (Ti), and zirconium (Zr) capable of forming a hydride, and metal B is a transition metal. In Article 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.