KR20220046029A - A transition metal boride composite, a method for manufacturing the same, and a catalyst for hydrogen generation reaction comprising the transition metal boride composite - Google Patents

Abstract

The present invention relates to a transition metal boride composite, a method for preparing the same, and a catalyst for a hydrogenation evolution reaction including the transition metal boride composite. Particularly, a large amount of grain boundaries as catalytic active sites in a transition metal boride composite is formed with ease through nano-structuring by a simple process using hydrothermal synthesis and heat treatment. When applying the transition metal boride composite as a catalyst, it is possible to significantly improve the performance of a hydrogen evolution reaction. In addition, when using the transition metal boride composite according to the present invention as a catalyst, a non-noble metal is used instead of an expensive platinum catalyst to reduce the production cost. Further, the transition metal boride composite according to the present invention has excellent catalytic activity capable of substituting for the existing platinum catalyst, and thus can significantly improve the electrochemical performance.

Description

A transition metal boride composite, a method for manufacturing the same, and a catalyst for hydrogen generation reaction comprising the transition metal boride complex composite}

The present invention relates to a transition metal boride complex, a method for preparing the same, and a catalyst for hydrogen evolution comprising the transition metal boride complex.

Environmental problems due to global warming are getting serious, and policies to reduce emissions of harmful exhaust gases such as nitric oxide, sulfide, and carbon dioxide generated during the combustion of fossil fuels, the main cause, are being implemented globally. In addition, it is inevitable to break away from the fossil fuel-based energy structure, which is a finite resource. Among various energies that are spotlighted as an alternative energy system for fossil fuels, hydrogen energy, which has no harmful exhaust gas and has a higher weight energy density than other fuels as energy storage and fuel, is attracting attention as an alternative energy. Recently, as the 'hydrogen economy revitalization roadmap' was announced in Korea, huge investments are being made in the overall development and commercialization of hydrogen energy such as hydrogen production, storage, transportation, and utilization, and the interest in the hydrogen market of companies and governments is increasing.

Currently, 97% of hydrogen production comes from natural gas steam reforming. Compared to the petrochemical process, the water electrolysis method requires relatively high-cost electric energy and has not been industrialized due to its inferior price competitiveness. The reason that the economic feasibility of water electrolysis technology has deteriorated is the high catalyst price. Platinum is known as the best Hydrogen Evolution Reaction (HER) catalyst material. It is a metal with a high price and scarcity, but has a disadvantage in that it has a small amount of reserves and is expensive. Therefore, it is urgent to develop a low-cost, high-performance catalyst that can replace platinum.

As a material for replacing precious metals such as platinum, most research has been focused on phosphide, sulfide, and carbide. It is still unclear.

On the other hand, the electronic structure of the catalyst is deformed at the grain boundary generated through nano-structuring and acts as an active site. Recently, studies have been published that the concentration of grain boundaries is proportional to the performance of CO ₂ RR, and consequently, the grain boundaries help to improve the performance.

Korean Patent Publication No. 2019-0055673

In order to solve the above problems, the present invention is to provide a method for producing a transition metal boride composite in which a large amount of crystal grain boundaries are formed efficiently for hydrogen generation reaction through nano-structuring in a simple process using hydrothermal synthesis and heat treatment. do.

Another object of the present invention is to provide a transition metal boride composite in which a large amount of grain boundaries are formed.

Another object of the present invention is to provide a catalyst for hydrogen generation reaction with significantly improved catalytic activity, including the transition metal boride complex.

Another object of the present invention is to provide an electrode including the catalyst for hydrogen evolution.

Another object of the present invention is to provide a hydrogen generator including the electrode, the counter electrode, and an electrolyte or ionized liquid.

The present invention puts a substrate, a first transition metal precursor, and a second transition metal precursor in a hydrothermal synthesis reactor, and hydrothermal synthesis to grow a transition metal composite oxide nanostructure including a first transition metal and a second transition metal on the substrate making; and a step of forming a transition metal boride composite having a plurality of grain boundaries formed by injecting a boron precursor on the substrate on which the transition metal composite oxide nanostructure is grown, and heat-treating it in an inert gas atmosphere. It provides a manufacturing method of

The first transition metal precursor may be a compound including at least one transition metal selected from the group consisting of nickel, tungsten, iron, copper and tin.

The first transition metal precursor is a nickel precursor, and the nickel precursor is nickel nitrate hexahydrate (NiNO ₃ o 6H ₂ O), nickel acetate (Nickel acetate, Ni(OCOCH ₃ ) ₂ o 4H ₂ O) and nickel chloride (Nickel chloride, NiCl ₂ o 6H ₂ O) may be at least one selected from the group consisting of.

The second transition metal precursor may be a compound including one or more transition metals selected from the group consisting of molybdenum, palladium, ruthenium, cobalt, iridium and titanium.

The second transition metal precursor is a molybdenum precursor, and the molybdenum precursor is sodium molybdate (NaMoO ₄ ), ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ ㅇH ₂ O), lithium molybdate (Li) ₂ MoO ₄ ), calcium molybdate (CaMoO ₄ ), potassium molybdate (K ₂ MoO ₄ ), and molybdenum oxytetrachlorite (MoOCl ₄ ) It may be at least one selected from the group consisting of.

The transition metal composite oxide nanostructure may be a mixture of a first transition metal precursor and a second transition metal precursor in a weight ratio of 1:9 to 9:1.

The transition metal composite oxide nanostructure may be grown in any one form selected from the group consisting of nanorods, nanoparticles, nanowalls and nanocubes.

In the step of growing the transition metal composite oxide nanostructure, the hydrothermal synthesis may be performed at a temperature of 110 to 230 °C for 2 to 8 hours.

The boron precursor may be at least one selected from the group consisting of elemental boron, boron nitride, and boron trihalide.

The inert gas may be any one selected from the group consisting of argon, nitrogen, hydrogen, helium, xenon, krypton, and neon.

In the step of preparing the transition metal boride composite, the heat treatment may be performed at a temperature of 700 to 1200 °C for 1 to 5 hours by increasing the temperature at a rate of 5 °C/min.

In the forming of the transition metal boride composite, the transition metal composite oxide nanostructure is converted into a transition metal composite nanosheet by heat treatment, and a transition metal boride composite is formed by bonding the transition metal composite nanosheet with boron. may be doing

The transition metal boride composite may include: a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are bonded; and a second boride crystal particle in which a second transition metal and a second boron of the transition metal composite nanosheet are bonded, and a plurality of crystals between the first boride crystal particle and the second boride crystal particle. A grain boundary may be formed.

The transition metal boride composite may include 5 to 15 wt% of boron particles based on the total weight of the transition metal boride composite.

The first transition metal precursor is nickel nitrate hexahydrate (nickel nitrate hexahydrate, NiNO ₃ ·6H ₂ O), the second transition metal precursor is sodium molybdate (NaMoO ₄ ), the transition metal composite oxide The nanostructure is a mixture of the first transition metal precursor and the second transition metal precursor in a weight ratio of 5:5 to 7:3, and the transition metal composite oxide nanostructure is grown in the form of a nanorod, and the transition metal composite oxide nano In the step of growing the structure, hydrothermal synthesis is performed at a temperature of 150 to 170 ° C. for 5.5 to 6.5 hours, the boron precursor is elemental boron, the inert gas is argon, and the transition metal boride complex is Ni ₃ B / It is a MoB composite, and the transition metal boride composite includes 8 to 13 wt% of boron particles based on the total weight of the transition metal boride composite, and the heat treatment in the step of preparing the transition metal boride composite is 5 ° C./min. It can be carried out for 2.5 to 3.5 hours at a temperature of 880 to 920 °C by increasing the temperature at a rate.

In addition, the present invention is a transition metal composite nanosheet comprising a first transition metal and a second transition metal; a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are combined; and a second boride crystal particle in which a second transition metal and a second boron of the transition metal composite nanosheet are bonded; as a transition metal boride complex comprising, the transition metal boride composite is the first boride crystal particle And it provides a transition metal boride composite that a plurality of grain boundaries are formed between the second boride crystal grains.

The transition metal composite nanosheet may be a mixture in which the first transition metal and the second transition metal are mixed in a weight ratio of 1:9 to 9:1.

The first transition metal may be at least one selected from the group consisting of nickel, tungsten, iron, copper, and tin.

The second transition metal may be at least one selected from the group consisting of molybdenum, palladium, ruthenium, cobalt, iridium and titanium.

The transition metal composite nanosheet may be a nickel molybdenum composite nanosheet.

The first boride crystal grains may be Ni ₃ B, and the second boride crystal grains may be MoB.

The boron particles may include 5 to 15% by weight based on the total weight of the transition metal boride composite.

The present invention also provides a catalyst for hydrogen evolution comprising the transition metal boride complex.

In addition, the present invention provides an electrode comprising the catalyst for the hydrogen generation reaction.

The present invention also provides a hydrogen generator including the electrode, the counter electrode, and an electrolyte or ionized liquid.

The transition metal boride composite of the present invention is a simple process using hydrothermal synthesis and heat treatment, and through nano-structuring, it easily forms a large amount of crystal grain boundaries, which are catalyst active points in the transition metal boride composite, so that when applied as a catalyst, the hydrogen generation reaction performance is significantly improved. can be improved

In addition, when applied as a catalyst, the transition metal boride composite of the present invention can reduce manufacturing cost by using a non-noble metal-based metal instead of an expensive platinum catalyst, and has excellent catalytic activity that can replace the existing platinum catalyst, thereby significantly improving electrochemical performance can be improved

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a schematic view schematically showing a method for manufacturing a transition metal boride composite according to the present invention.
2 is a TEM image (a) of the Ni ₃ B/MoB composite prepared in Example 2.
Figure 3 shows the STEM image of the Ni ₃ B / MoB composite prepared in Example 2 and the corresponding EDX element mapping (element mapping) (b) results.
4 is a HR-TEM image (c) of the Ni ₃ B/MoB composite prepared in Example 2.
5 is a polarization curve showing the HER performance results measured in 0.5MH ₂ SO ₄ when the transition metal boride composite prepared in Example 1 and Comparative Examples 1 and 2 and platinum foil were used as catalysts ( a) and Tafel slope(b).
6 is an EIS plot (a) and charging current for scan speed at an overvoltage of 150 mV when the transition metal boride composite and Pt foil prepared in Example 1 and Comparative Examples 1 and 2 were used as catalysts; FIG. The density difference (b) is shown.
7 shows a stability curve at a constant 10mA cm ^-2 current density when the transition metal boride composites prepared in Example 1 and Comparative Examples 1 and 2 were used as catalysts.

Hereinafter, the present invention will be described in more detail by way of one embodiment.

The present invention relates to a transition metal boride complex, a method for preparing the same, and a catalyst for hydrogen evolution comprising the transition metal boride complex.

In the present invention, a grain boundary refers to an interface existing between crystals having different crystal directions.

Although platinum shows the best performance in the hydrogen evolution reaction, it has a disadvantage of small reserves and high price. .

Accordingly, in the present invention, as a new material with improved catalytic performance while replacing the expensive platinum catalyst, a transition metal composite oxide nanostructure is grown by hydrothermal synthesis of two transition metal precursors, and a boron precursor is introduced on the grown nanostructure. After heat treatment to prepare a transition metal boride composite, the two transition metals each form boride crystal grains, and between these crystal grains, a large amount of grain boundaries acting as catalyst active sites are formed to improve the performance of the non-noble metal catalyst. significantly improved.

The transition metal boride composite of the present invention is a simple process using hydrothermal synthesis and heat treatment to easily form large amounts of crystal grain boundaries, which are catalyst active points in the transition metal boride composite, through nano-structuring, and when applied as a catalyst, hydrogen generation reaction performance is improved. can be significantly improved. In addition, by using a non-noble metal-based metal instead of an expensive platinum catalyst, the manufacturing cost can be reduced, and the electrochemical performance can be significantly improved by having excellent catalytic activity that can replace the existing platinum catalyst.

Specifically, in one aspect of the present invention, a substrate, a first transition metal precursor, and a second transition metal precursor are put in a hydrothermal synthesis reactor, and the transition metal containing the first transition metal and the second transition metal is performed on the substrate by hydrothermal synthesis. Growing a composite oxide nanostructure (S1); and a step (S2) of forming a transition metal boride composite having a plurality of grain boundaries formed by injecting a boron precursor on the substrate on which the transition metal composite oxide nanostructure is grown, and heat-treating it under an inert gas atmosphere. A method for preparing a boride composite is provided.

1 is a schematic view schematically showing a method for manufacturing a transition metal boride composite according to the present invention. 1, a transition metal composite nanosheet and a transition metal composite nanosheet by growing a transition metal composite oxide nanostructure including two transition metals on a substrate by a hydrothermal synthesis method, adding boron powder on the nanostructure, and then heat-treating the nanostructure It shows that a transition metal boride complex is formed by bonding of boron particles. In the transition metal boride composite, it can be seen that two types of transition metals form boride crystal grains, respectively, and a plurality of grain boundaries acting as active points are formed between these crystal grains.

Hereinafter, each step will be described in detail with reference to FIG. 1 .

(S1) growing a transition metal composite oxide nanostructure

In the step (S1), the substrate, the first transition metal precursor and the second transition metal precursor are put in a hydrothermal synthesis reactor, and the transition metal composite oxide nano containing the first transition metal and the second transition metal is synthesized on the substrate by hydrothermal synthesis. structures can be grown.

The substrate may be nickel foam, but is not limited thereto. When the substrate is nickel foam, a process of removing nickel oxide present on the surface may be performed by immersing the nickel foam in hydrochloric acid (HCl). This creates an inactive nickel oxide film on the surface of nickel foam exposed to air for a long time, and impurities may adhere to it. Accordingly, when the nickel foam is etched with hydrochloric acid, the inactive oxide film and impurities on the surface are removed, and the surface is roughened so that a transition metal composite oxide nanostructure can be formed more easily, and corners and corners can be created.

It is preferable to use a metal having excellent catalytic activity and bonding strength with the boron precursor as the first transition metal precursor, and specifically, it may be a compound containing at least one transition metal selected from the group consisting of nickel, tungsten, iron, copper and tin. and preferably a nickel precursor, a tungsten precursor, a tin precursor, or a mixture thereof. Most preferably, it may be a nickel precursor.

The nickel precursor is nickel nitrate hexahydrate (nickel nitrate hexahydrate, NiNO ₃ o 6H ₂ O), nickel acetate (Nickel acetate, Ni(OCOCH ₃ ) ₂ o 4H ₂ O) and nickel chloride (Nickel chloride, NiCl ₂ It may be at least one selected from the group consisting of ㅇ6H ₂ O). Preferably, nickel(II) nitrate hexahydrate, nickel acetate, or a mixture thereof may be used, and most preferably, nickel(II) nitrate hexahydrate may be used. When nickel(II) nitrate hexahydrate is used as the nickel precursor, a transition metal complex oxide nanostructure is formed better than other nickel precursors, and thus a transition metal boride maintaining a high surface area can be generated.

It is preferable to use a metal having excellent catalytic activity and bonding strength with the boron precursor as the second transition metal precursor, and specifically, a compound containing at least one transition metal selected from the group consisting of molybdenum, palladium, ruthenium, cobalt, iridium and titanium may be, preferably a molybdenum precursor, a cobalt precursor, or a mixture thereof, and most preferably a molybdenum precursor.

The molybdenum precursor is sodium molybdate (NaMoO ₄ ), ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ ㅇH ₂ O), lithium molybdate (Li ₂ MoO ₄ ), calcium molybdate (CaMoO) ₄ ), potassium molybdate (K ₂ MoO ₄ ), and molybdenum oxytetrachlorite (MoOCl ₄ ) It may be at least one selected from the group consisting of. Preferably it may be sodium molybdate (NaMoO ₄ ), ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ oH ₂ O) or a mixture thereof, most preferably sodium molybdate (NaMoO ₄ ) ) can be used.

As described above, the first transition metal precursor and the second transition metal precursor are respectively combined with the boron precursor to form two kinds of boride crystal grains, and each boride crystal grains grow into their own crystal phases to each other. By having different grain boundaries, an excellent synergistic effect of catalytic activity can be obtained during catalysis. If only one type of transition metal precursor is used alone, since only one type of boride crystal grain and the grain boundary grow, the synergistic effect of the catalytic activity of the two types of boride crystal grains may not be sufficiently exhibited.

In the transition metal composite oxide nanostructure, the first transition metal precursor and the second transition metal precursor are in a weight ratio of 3:7 to 8:2, more preferably 5:5 to 7:3 by weight, most preferably 6:4 by weight. may be mixed with At this time, if the mixing ratio is not satisfied, the transition metal composite oxide nanostructure may grow irregularly, and the shape is not uniform, and consequently, the transition metal boride composite may not be properly formed.

The transition metal composite oxide nanostructure may be one grown in a 0-dimensional to 3-dimensional structure by being regularly arranged at regular intervals and at a predetermined size on the substrate in order to increase the specific surface area to improve the catalytic active region, but is limited thereto not.

As a specific form of the transition metal composite oxide nanostructure, it may be grown in any one form selected from the group consisting of nanorods, nanoparticles, nanowalls, and nanocubes. Preferably, the transition metal composite oxide nanostructure may grow in the form of nanorods or nanosheets, and most preferably grow in the form of nanorods. For example, the 0-dimensional structure may mean the form of the nanoparticle, the one-dimensional structure may mean the form of the nanorod, and the two-dimensional structure may mean the form of the nanosheet or nanowall. and the three-dimensional structure may mean a nanocube shape, but is not limited thereto.

In the step of growing the transition metal composite oxide nanostructure, the hydrothermal synthesis may be performed at a temperature of 110 to 230 °C for 2 to 8 hours. Preferably, it may be carried out at a temperature of 130 to 190 °C for 4 to 7 hours, and most preferably at a temperature of 150 to 170 °C for 5.5 to 6.5 hours. At this time, if the temperature and time conditions of the hydrothermal synthesis do not satisfy the above ranges, the interval, size, and shape of the transition metal composite oxide nanostructure may not be constant and may be irregular, and the synthesis may not sufficiently occur and thus may not grow into a nanostructure. there is.

(S2) preparing a transition metal boride composite

In the step (S2), a boron precursor is added on the substrate on which the transition metal composite oxide nanostructure is grown, and the transition metal composite oxide nanostructure is transformed into a transition metal composite nanosheet by heat treatment in an inert gas atmosphere, and the transition The metal composite nanosheet may be combined with boron to form a transition metal boride composite in which a plurality of grain boundaries are formed. In particular, in the above step, in the process of boring of the transition metal composite oxide nanostructure, the existing nanostructure form is broken, and the first transition metal and the second transition metal evenly distributed are converted to boride, respectively, and the rate of boronization is different, and the crystal structure is different. is different, so a nanosheet having a shape completely different from that of the nanostructure in step (S1) may be generated.

The boron precursor may be at least one selected from the group consisting of elemental boron, boron nitride and boron trihalide, preferably elemental boron, boron nitride, or a mixture thereof, and most preferably elemental boron.

When elemental boron is used as the boron precursor, the unit cost is lower than that of other boron precursors, so that the manufacturing cost can be further reduced, and electrical conductivity and durability can be further improved. In the present invention, the catalytic active point is improved by bonding the boron element to the transition metal composite nanosheet to form a transition metal boride complex, and thus, there is an advantage that can be applied as a substitute for a platinum catalyst.

The inert gas may be any one selected from the group consisting of argon, nitrogen, hydrogen, helium, xenon, krypton and neon, preferably argon, nitrogen, or a mixture thereof, and most preferably argon. .

In the step of preparing the transition metal boride composite, the heat treatment may be performed at a temperature of 700 to 1200 °C for 1 to 5 hours by raising the temperature at a rate of 5 °C/min. Preferably, it may be carried out at a temperature of 850 to 950 °C for 2 to 4 hours, and most preferably at a temperature of 880 to 920 °C for 2.5 to 3.5 hours. At this time, if the heat treatment temperature is less than 700 ° C or the heat treatment time is less than 1 hour, the heat treatment may not be sufficiently performed and the transition metal boride composite may not be properly formed. If this time exceeds 5 hours, some of the boride crystal grains are lost due to deterioration due to excessive heat treatment, or the grain boundaries are reduced, so that the catalyst performance may be deteriorated.

In the forming of the transition metal boride composite, the transition metal composite oxide nanostructure is converted into a transition metal composite nanosheet by heat treatment, and a transition metal boride composite is formed by bonding the transition metal composite nanosheet with boron. can do.

The transition metal boride composite may include: a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are bonded; and a second boride crystal particle in which a second transition metal and a second boron of the transition metal composite nanosheet are bonded, and a plurality of crystals between the first boride crystal particle and the second boride crystal particle. A grain boundary may be formed.

In the transition metal boride composite, two types of transition metals contained in the transition metal composite nanosheet form boride crystal grains by bonding with boron particles, respectively, and a plurality of grain boundaries are formed in large quantities between the crystal grains. can have a structure. In particular, since grain boundaries can act as catalyst active sites, catalyst performance can be greatly increased when a large amount of grain boundaries are used even with the same material.

The transition metal composite nanosheet may be a nickel molybdenum composite nanosheet, but is not limited thereto.

The first boride crystal grains may be Ni ₃ B or W ₃ B, and the second boride crystal grains may be MoB. That is, the transition metal boride composite reacts with nickel valence boron of the nickel molybdenum composite nanosheet to form Ni ₃ B crystal grains, and the adjacent molybdenum valence reacts with boron to form MoB crystal grains synthesized Ni ₃ B / It may be a MoB complex or a W ₃ B/MoB complex. The Ni ₃ B/MoB composite or W ₃ B/MoB composite may have a structure in which a plurality of grain boundaries acting as catalyst active points are formed between Ni ₃ B or W ₃ B crystal grains and MoB crystal grains.

The transition metal boride composite may include 5 to 15% by weight of boron particles, preferably 8 to 13% by weight, and most preferably 10% by weight based on the total weight of the transition metal boride composite. At this time, if the content of the boron atoms is less than 5% by weight, the hydrogen generation reaction catalytic activity may be significantly reduced due to reduction of grain boundaries, which are catalyst active points, and, conversely, if it exceeds 15% by weight, improved catalytic performance can no longer be expected.

The transition metal boride composite may have a structure in which a Ni ₃ B/MoB composite is grown in the form of a nanosheet on a surface of a Ni foam skeleton.

In particular, although not explicitly described in the following Examples or Comparative Examples, in the method for producing a transition metal boride composite according to the present invention, the type and mixing ratio of each component, the heat treatment temperature for each step, and the molybdenum carbide nanoparticles A complex was prepared under different types of conditions, and using it as a catalyst for a hydrogen generation reaction, a hydrogen generator was formed, and then the amount of hydrogen generated and the rate of hydrogen generation were measured by a conventional method.

As a result, unlike in other conditions and other numerical ranges, when all of the following conditions were satisfied, both the hydrogen generation amount and the hydrogen generation rate measured for 10 to 30 minutes were remarkably improved, unlike the conventional platinum catalyst, and the activation of the catalyst It was confirmed that the catalytic performance was remarkably improved due to the low energy.

① The first transition metal precursor is nickel (II) nitrate hexahydrate (nickel nitrate hexahydrate, NiNO ₃ o 6H ₂ O), ② the second transition metal precursor is sodium molybdate (NaMoO ₄ ), ③ the transition The metal composite oxide nanostructure is a mixture of the first transition metal precursor and the second transition metal precursor in a weight ratio of 5:5 to 7:3, ④ the transition metal composite oxide nanostructure is to grow in the form of a nanorod, ⑤ the above In the step of growing the transition metal composite oxide nanostructure, hydrothermal synthesis is performed at a temperature of 150 to 170 ° C. for 5.5 to 6.5 hours, ⑥ the boron precursor is boron element, ⑦ the inert gas is argon, ⑧ the transition metal The boride composite is a Ni ₃ B/MoB composite, ⑨ the transition metal boride composite includes 8 to 13 wt% of boron particles based on the total weight of the transition metal boride composite, and ⑩ preparing the transition metal boride composite The heat treatment in the step may be performed at a temperature of 880 to 920 °C for 2.5 to 3.5 hours by raising the temperature at a rate of 5 °C / min.

However, when any one of the ten conditions was not satisfied, the amount of hydrogen generated and the rate of hydrogen generation were low, so that the catalyst performance was poor, and thus the effect of improving the electrochemical performance could not be expected.

In addition, another aspect of the present invention, a transition metal composite nanosheet comprising a first transition metal and a second transition metal; a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are combined; and a second boride crystal particle in which a second transition metal and a second boron of the transition metal composite nanosheet are bonded; as a transition metal boride complex comprising, the transition metal boride composite is the first boride crystal particle And it provides a transition metal boride composite that a plurality of grain boundaries are formed between the second boride crystal grains.

In the transition metal composite nanosheet, the first transition metal and the second transition metal are mixed in a weight ratio of 1:9 to 9:1, more preferably 5:5 to 7:3, and most preferably 6:4. it could be

The first transition metal may be at least one selected from the group consisting of nickel, tungsten, iron, copper and tin, preferably nickel, tungsten, tin, or a mixture thereof, and most preferably nickel .

The second transition metal may be at least one selected from the group consisting of molybdenum, palladium, ruthenium, cobalt, iridium and titanium, preferably molybdenum, cobalt, or a mixture thereof, and most preferably molybdenum. .

The transition metal composite nanosheet may be a nickel molybdenum composite nanosheet.

The first boride crystal grains may be Ni ₃ B, and the second boride crystal grains may be MoB. That is, the transition metal boride composite may be a Ni ₃ B/MoB composite.

The transition metal boride composite may include 5 to 15% by weight of boron particles, preferably 8 to 13% by weight, and most preferably 10% by weight based on the total weight of the transition metal boride composite.

In addition, another aspect of the present invention provides a catalyst for hydrogen evolution comprising the transition metal boride complex.

In addition, another aspect of the present invention provides an electrode comprising the catalyst for the hydrogen generation reaction.

Another aspect of the present invention provides a hydrogen generator including the electrode, the counter electrode, and an electrolyte or ionized liquid.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by the following examples.

Example 1: Transition metal boride (Ni) ₃ B/MoB) complex synthesis

ingredients

The substrate was nickel foam (Nickel Foam, NF) (Kunshan Guangjiayuan new materials Co. Ltd.), and nickel (II) nitrate hexahydrate (Ni(NO ₃ ) ₂ ㅇ 6H ₂ O) as the first transition metal precursor (Ni(NO 3 ) 2 o 6H 2 O) ( Sigma-Aldrich, 98%) and sodium molybdate (Sigma-Aldrich, 98%) were used as the second transition metal precursor, and boron powder (Sigma-Aldrich, 95%) was used as the boron precursor.

(1) Transition metal composite oxide (NiMoO ₄ ) nanorod synthesis

First, commercial nickel foam was immersed in 6 M HCl at room temperature for 30 minutes to remove nickel oxide present on the surface. Nickel foam from which nickel oxide has been removed, nickel (II) nitrate hexahydrate, and sodium molybdate were put into a 100 mL Teflon-lined hydrothermal synthesis reactor in a weight ratio of 6:4, and hydrothermally synthesized at 160 ° C. for 6 hours. One side of the nickel foam NiMoO ₄ nanorods were grown on the The grown NiMoO ₄ nanorods were washed with distilled water and then dried in an oven at 85 °C.

(2) Transition metal boride (Ni ₃ B/MoB) composite synthesis

After putting boron powder on the substrate on which the dried NiMoO ₄ nanorods were grown, it was put in an electric furnace, the temperature was raised to 900 °C in an argon atmosphere at a rate of 5 °C/min, and then heat-treated for 3 hours. The particles were combined to form a Ni ₃ B/MoB composite.

Comparative Example 1: Nickel boride (Ni) ₃ B)

Commercial nickel boride (Ni ₃ B) was prepared by a conventional method.

Comparative Example 2: Molybdenum Boride (MoB)

Commercial molybdenum boride (MoB) was prepared by a conventional method.

Experimental Example 1: TEM, EDX element mapping and HR-TEM analysis

The Ni ₃ B/MoB composite prepared in Example 1 was analyzed using TEM, EDX element mapping, and HR-TEM to confirm the surface, crystal structure, and grain boundary. The results are shown in FIGS. 2 to 4 .

2 is a TEM image (a) of the Ni ₃ B/MoB composite prepared in Example 2.

Figure 3 shows the STEM image of the Ni ₃ B / MoB composite prepared in Example 2 and the corresponding EDX element mapping (element mapping) (b) results.

4 is a HR-TEM image (c) of the Ni ₃ B/MoB composite prepared in Example 2.

2 to 4, it can be seen that the structure of the Ni ₃ B/MoB composite is in the form of a nanosheet, and it was confirmed that B, Mo, and Ni elements are evenly distributed. In particular, when examining the Ni ₃ B/MoB composite in detail with the HR-TEM image, it was found that the Ni ₃ B and MoB nanocrystals were evenly distributed to have many grain boundaries. The lattice distances of crystals indicated by numbers ①, ④ and ⑤ are Ni ₃ B with exposed surfaces of (111), (200), and (031), respectively, and the lattice distances of crystals with numbers ②, ③, and ⑥ are respectively (111) with exposed surfaces. , (200), (031), which is consistent with MoB.

The mechanism by which abundant grain boundaries are formed in the Ni ₃ B/MoB composite is as follows. First, in NiMoO ₄ nanosheets in which Ni and Mo atoms are uniformly distributed, Ni atoms react with boron to form Ni ₃ B, and adjacent Mo atoms are converted into MoB. As a result, a large number of adjacent Ni ₃ B and MoB nanocrystal grains are formed, and a large number of grain boundaries are formed in the synthesized Ni ₃ B/MoB composite, providing an active region that greatly contributes to the improvement of electrochemical performance. And it was found.

Experimental Example 2: TEM, EDX element mapping and HR-TEM analysis

By applying the transition metal boride complex prepared in Example 1 and Comparative Examples 1 and 2 as a catalyst for hydrogen evolution, hydrogen evolution (HER) performance in 0.5MH ₂ SO ₄ and EIS and charging current at 150 mV overvoltage Density was analyzed. Platinum foil (Pt foil) was additionally analyzed for hydrogen evolution performance comparison. The results are shown in FIGS. 5 to 7 .

5 is a polarization curve showing the HER performance results measured in 0.5MH ₂ SO ₄ when the transition metal boride composite prepared in Example 1 and Comparative Examples 1 and 2 and platinum foil were used as catalysts ( a) and Tafel slope(b).

6 is an EIS plot (a) and charging current for scan speed at an overvoltage of 150 mV when the transition metal boride composite and platinum foil prepared in Example 1 and Comparative Examples 1 and 2 were used as catalysts; FIG. The density difference (b) is shown.

5 and 6, the overvoltage required to achieve a current density of 10 mA cm ^-2 is 167 mV in Comparative Example 1 (Ni ₃ B), Comparative Example 2 (MoB), 124 mV, the Example 1 (Ni ₃ B/MoB) was confirmed to be 61 mV. Through this, in the case of Example 1 (Ni ₃ B / MoB), the hydrogen generation reaction performance has an overvoltage that is more than twice that of Comparative Example 1 (Ni ₃ B) and Comparative Example 2 (MoB) synthesized, respectively. was found to represent In addition, it was confirmed that Example 1 (Ni ₃ B/MoB) had a high current density, low Tafel slope, charge transfer resistance, and a large electrochemical surface area.

7 shows a stability curve at a constant 10mA cm ^-2 current density when the transition metal boride composites prepared in Example 1 and Comparative Examples 1 and 2 were used as catalysts. Referring to FIG. 7 , it can be seen that the current density is maintained constant even after 15 hours have elapsed, indicating that the durability is excellent.

Claims (24)

Putting the substrate, the first transition metal precursor, and the second transition metal precursor into a hydrothermal synthesis reactor, hydrothermal synthesis to grow a transition metal composite oxide nanostructure including the first transition metal and the second transition metal on the substrate; and
Forming a transition metal boride composite having a plurality of grain boundaries formed by injecting a boron precursor on the substrate on which the transition metal composite oxide nanostructure is grown, and heat-treating it under an inert gas atmosphere; manufacturing method.
According to claim 1,
The first transition metal precursor is nickel, tungsten, iron, a method of producing a transition metal boride complex of a compound containing one or more transition metals selected from the group consisting of copper and tin.
3. The method of claim 2,
The first transition metal precursor is a nickel precursor,
The nickel precursor is nickel nitrate hexahydrate (nickel nitrate hexahydrate, NiNO ₃ o 6H ₂ O), nickel acetate (Nickel acetate, Ni(OCOCH ₃ ) ₂ o 4H ₂ O) and nickel chloride (Nickel chloride, NiCl ₂ ㅇ 6H ₂ O) of at least one selected from the group consisting of a method for producing a transition metal boride composite.
According to claim 1,
The second transition metal precursor is molybdenum, palladium, ruthenium, cobalt, iridium and a method for producing a transition metal boride complex of a compound containing one or more transition metals selected from the group consisting of titanium.
5. The method of claim 4,
The second transition metal precursor is a molybdenum precursor,
The molybdenum precursor is sodium molybdate (NaMoO ₄ ), ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ ㅇH ₂ O), lithium molybdate (Li ₂ MoO ₄ ), calcium molybdate (CaMoO) ₄ ), potassium molybdate (K ₂ MoO ₄ ), and molybdenum oxytetrachlorite (MoOCl ₄ ) A method for producing a transition metal boride complex that is at least one selected from the group consisting of.
According to claim 1,
The transition metal composite oxide nanostructure is a method of producing a transition metal boride composite in which the first transition metal precursor and the second transition metal precursor are mixed in a weight ratio of 1:9 to 9:1.
According to claim 1,
The transition metal composite oxide nanostructure is a method for producing a transition metal boride composite that is grown in any one form selected from the group consisting of nanorods, nanoparticles, nanowalls and nanocubes.
According to claim 1,
In the step of growing the transition metal composite oxide nanostructure, the hydrothermal synthesis is performed at a temperature of 110 to 230 °C for 2 to 8 hours.
According to claim 1,
The boron precursor is a method for producing a transition metal boride complex of at least one selected from the group consisting of elemental boron, boron nitride, and boron trihalide.
According to claim 1,
In the step of preparing the transition metal boride composite, the heat treatment is performed at a temperature of 700 to 1200° C. for 1 to 5 hours by increasing the temperature at a rate of 5° C./min.
According to claim 1,
The step of forming the transition metal boride composite converts the transition metal composite oxide nanostructure into a transition metal composite nanosheet by heat treatment,
A method for producing a transition metal boride composite to form a transition metal boride composite by bonding the transition metal composite nanosheet and boron.
12. The method of claim 11,
The transition metal boride composite is,
a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are combined; and
Including;
A method of manufacturing a transition metal boride composite in which a plurality of grain boundaries are formed between the first boride crystal grains and the second boride crystal grains.
According to claim 1,
The transition metal boride composite is a method for producing a transition metal boride composite comprising 5 to 15% by weight of boron particles based on the total weight of the transition metal boride composite.
According to claim 1,
The first transition metal precursor is nickel (II) nitrate hexahydrate (nickel nitrate hexahydrate, NiNO ₃ o 6H ₂ O),
The second transition metal precursor is sodium molybdate (NaMoO ₄ ),
The transition metal composite oxide nanostructure is a mixture of a first transition metal precursor and a second transition metal precursor in a weight ratio of 5:5 to 7:3,
The transition metal composite oxide nanostructure is to grow in the form of a nanorod,
In the step of growing the transition metal composite oxide nanostructure, hydrothermal synthesis is performed at a temperature of 150 to 170 ° C. for 5.5 to 6.5 hours,
The boron precursor is elemental boron,
The inert gas is argon,
The transition metal boride composite is a Ni ₃ B / MoB composite,
The transition metal boride composite includes 8 to 13% by weight of boron particles based on the total weight of the transition metal boride composite,
In the step of preparing the transition metal boride composite, the heat treatment is performed at a temperature of 880 to 920° C. for 2.5 to 3.5 hours by increasing the temperature at a rate of 5° C./min.
A transition metal composite nanosheet comprising a first transition metal and a second transition metal;
a first boride crystal particle in which a first transition metal and a first boron of the transition metal composite nanosheet are combined; and
A transition metal boride composite comprising a; second boride crystal particles in which a second transition metal and a second boron of the transition metal composite nanosheet are combined,
The transition metal boride composite is a transition metal boride composite in which a plurality of grain boundaries are formed between the first boride crystal grains and the second boride crystal grains.
16. The method of claim 15,
The transition metal composite nanosheet is a transition metal boride composite in which the first transition metal and the second transition metal are mixed in a weight ratio of 1:9 to 9:1.
16. The method of claim 15,
The first transition metal is a transition metal boride composite of at least one selected from the group consisting of nickel, tungsten, iron, copper and tin.
16. The method of claim 15,
The second transition metal is a transition metal boride complex of at least one selected from the group consisting of molybdenum, palladium, ruthenium, cobalt, iridium and titanium.
16. The method of claim 15,
The transition metal composite nanosheet is a nickel molybdenum composite nanosheet, the transition metal boride composite.
16. The method of claim 15,
The first boride crystal grains are Ni ₃ B, and the second boride crystal grains are MoB transition metal boride composite.
16. The method of claim 15,
The boron particles are transition metal boride composite comprising 5 to 15% by weight based on the total weight of the transition metal boride composite.
A catalyst for hydrogen evolution comprising the transition metal boride complex of any one of claims 15 to 21.
An electrode comprising the catalyst for hydrogen evolution of claim 22.
A hydrogen generator comprising the electrode of claim 23, a counter electrode, and an electrolyte or ionized liquid.

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