KR102224725B1 - Layered FeP, method for producing the same, layered FeP nanosheet exfoliated from the same and catalyst including the same nanosheet - Google Patents

Abstract

The present invention relates to a layered FeP, a method for producing the same, and a layered FeP nanosheet peeled therefrom, and a catalyst including the same, and more particularly, it has a two-dimensional crystal structure, unlike the conventional 3D bulk FeP, and has a peelability. It is excellent and is easy to peel in the form of nanosheets, and the surface area is significantly wider than that of 3D bulk FeP, so it has an activity as an electrochemical water decomposition catalyst. About.

Description

Layered FeP, method for producing the same, layered FeP nanosheet exfoliated therefrom, and a catalyst including the same TECHNICAL FIELD [Layered FeP, method for producing the same, layered FeP nanosheet exfoliated from the same and catalyst including the same nanosheet}

The present invention relates to a layered FeP, a method for producing the same, a layered FeP nanosheet peeled therefrom, and a catalyst including the same, and more particularly, it has a two-dimensional crystal structure unlike the conventional bulk FeP, and has excellent peelability. Thus, it is easy to peel in the form of nanosheets, and the surface area is significantly wider than that of bulk FeP, so that the layered FeP has an activity as an electrochemical water decomposition catalyst, and the FeP nanosheets peeled therefrom, and a method for preparing the same, and a catalyst comprising the same .

Various ultra-thin two-dimensional (2D) materials including graphene are being actively studied in various fields based on new physical, chemical, mechanical, and optical properties. Such low-dimensional materials are expected to have innovative new functions that existing bulk materials do not have, and have great potential as a next-generation future material that will replace existing materials.

Research on existing 2D materials is based on a top-down method that separates van der Waals bonds with weak interlayer bonding by physical and chemical methods, and a bottom-up method that grows a large-area thin film based on a vapor deposition method. Has become. In particular, in the top-down method, since the pristine of the material to be exfoliated must have a two-dimensional layered crystal structure, graphene without a band gap, layered metal oxide/nitride with low charge mobility, electron mobility/ There is a problem of very limited research targets such as transition metal chalcogen compounds having low electrical conductivity.

Due to the limitations of conventional research methods, 2D materials have been studied very limitedly for materials such as graphene and transition metal chalcogen compounds, and this is essentially the availability of low-dimensional materials depending on the type of element to be used. It has limitations in that it is limited accordingly, and is not suitable for the development of low-dimensional future materials for countless 3D bulk materials that are not layered.

The electrochemical water decomposition reaction is receiving a lot of attention as a reaction capable of obtaining hydrogen, which is emerging as an eco-friendly energy to replace fossil fuels. In the electrolysis reaction of water, a catalyst is used.Platinium (Pt) catalysts were mainly used in the past.However, platinum (Pt) catalysts were mainly used as a substitute for nickel phosphide (NiP) and cobalt phosphide (CoP) as substitutes for platinum due to its low reserves and high price. ) And iron phosphide (FeP) are attracting attention. Among them, iron phosphide is a catalyst material that is being developed intensively in that it is advantageous for mass production because iron is abundantly buried on the earth.

When such iron phosphide is made of a material having a two-dimensional crystal structure, it is expected that a catalyst having excellent activity can be prepared because it can have a significantly larger surface area than a material having a three-dimensional bulk crystal structure like conventional iron phosphide. As expected, there is a demand for the development of a technology capable of varying the crystal structure.

Korean Patent Application Publication No. 10-2018-01177679 (published on October 30, 2018)

The present invention has been conceived to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a layered FeP having a layered crystal structure and excellent peelability.

In addition, an object of the present invention is to provide a layered FeP having a two-dimensional crystal structure and excellent releasability.

In addition, the third problem to be solved of the present invention is to provide a FeP nanosheet that is peeled from the layered FeP of the present invention and has excellent activity as an electrochemical water decomposition catalyst.

In addition, the fourth problem to be solved of the present invention is to provide a catalyst comprising the FeP nanosheets of the present invention.

The present invention includes (1) lithium (Li) or sodium (Na) powder; It has a layered crystal structure in which the space group is P4/nmm and the crystal system is tetragonal by sequentially heat treatment and cooling after mixing iron (Fe) powder and phosphorus (P) powder. , Obtaining a layered compound represented by the formula LiFeP or NaFeP; And (2) preparing a layered FeP compound without changing the crystal structure of the layered compound by selectively removing Li or Na ions contained in the layered compound. to provide.

According to a preferred embodiment of the present invention, the heat treatment during step (1) is to heat treatment for 3 days to 5 days at a temperature of 750°C to 850°C after mixing Li powder, Fe powder, and P powder. I can.

According to a preferred embodiment of the present invention, the heat treatment during step (1) may be heat treatment at 800° C. to 900° C. for 3 to 5 days after mixing Na powder, Fe powder and P powder.

According to a preferred embodiment of the present invention, the cooling step in step (1) may be performed at a temperature reduction rate of 0.5°C/h to 2.0°C/h.

According to a preferred embodiment of the present invention, step (2) may be to selectively remove Li or Na ions by treating a solvent containing at least one selected from water, ethanol, and isopropanol.

According to a preferred embodiment of the present invention, the treatment of the solvent may be performed at a temperature of 20°C to 60°C.

According to a preferred embodiment of the present invention, the LiFeP or NaFeP compound obtained in step (1) may have a crystal structure in which Li ions or Na ions are intercalated between each layer in the crystal of the layered FeP compound. have.

In addition, the present invention provides a layered FeP compound having a layered crystal structure in which a space group is P4/nmm and a crystal system is tetragonal.

According to a preferred embodiment of the present invention, the layered FeP compound is 14.7±0.2, 28.4±0.2, 37.5±0.2, 46.0 in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It may have a peak at 2θ values of ±0.2, 48.8±0.2, 51.8±0.2, and 57.9±0.2, and may not have a peak at 2θ values of 34.2±0.2, 39.1±0.2, and 58.8±0.2.

According to a preferred embodiment of the present invention, the layered FeP compound may have a maximum value in a region of 650 nm to 670 nm in a region of a wavelength of 630 nm to 800 nm of a photoluminescence emission graph.

In addition, the present invention provides a FeP nanosheet having a layered crystal structure of a tetragonal crystal system, peeled from the layered FeP compound described above, the space group is P4/nmm.

According to a preferred embodiment of the present invention, the average thickness of the FeP nanosheets may be 30nm or less.

In addition, the present invention provides a catalyst comprising the above-described FeP nanosheets.

The present invention has been devised to solve the above-described problems, and according to the layered FeP manufacturing method of the present invention, it is possible to prepare a FeP compound having a two-dimensional crystal structure and excellent peelability unlike the conventional 3D bulk FeP. .

In addition, the layered FeP according to the present invention has a two-dimensional crystal structure compared to the conventional 3D bulk FeP and can be easily peeled off into FeP nanosheets.

In addition, the FeP nanosheet of the present invention has a two-dimensional crystal structure and a remarkably wide surface area compared to the conventional 3D bulk FeP, and thus has excellent properties as a catalyst.

In addition, the catalyst including the FeP nanosheet of the present invention may exhibit excellent activity due to its large surface area when used for an electrochemical water decomposition catalyst.

1 is a view schematically showing a crystal structure of a layered LiFeP compound and a layered FeP compound according to an embodiment of the present invention.
2 is a photograph of a powder of a layered FeP compound according to an embodiment of the present invention.
3 is a SEM image of a microstructure of a layered LiFeP compound and a layered FeP compound according to an embodiment of the present invention.
4 is a TEM photograph (left) and an EDS image (center and right) of the FeP nanosheet according to an embodiment of the present invention.
5 is a view showing the result of TEM diffraction pattern analysis of the FeP nanosheet according to an embodiment of the present invention.
6 is a graph comparing the XRD diffraction pattern of the samples of Preparation Example 1 and Example 1 of the present invention with the reference value of the XRD pattern of the LiFeP compound.
7 shows the AFM analysis results for the FeP nanosheets according to Example 3 of the present invention.
8A is an image showing a result of analyzing PL (Photoluminescence) data of a layered FeP according to an embodiment of the present invention.
8B is a graph analyzing PL data of a layered FeP according to an embodiment of the present invention according to a wavelength.
9A to 9C are STEM images of a layered FeP according to an embodiment of the present invention.
10 is an SEM image of a microstructure of a layered NaFeP according to an embodiment of the present invention.
11 is a TEM image of a layered FeP prepared from layered NaFeP according to an embodiment of the present invention.
12 is a view showing the TEM diffraction pattern analysis result of the layered FeP prepared from the layered NaFeP according to an embodiment of the present invention.
13 is a STEM image of a layered NaFeP according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms, and is not limited to the embodiments described herein.

Hereinafter, a method for preparing a layered FeP compound according to the present invention will be described.

As described above, the conventional FeP compound has a 3D crystal structure, does not peel off into nanosheets, and has a small surface area when used as a catalyst.

Thus, the present invention (1) lithium (Li) or sodium (Na) powder and; It has a layered crystal structure in which the space group is P4/nmm and the crystal system is tetragonal by sequentially heat treatment and cooling after mixing iron (Fe) powder and phosphorus (P) powder. , Obtaining a layered compound represented by the formula LiFeP or NaFeP; And (2) preparing a layered FeP compound without changing the crystal structure of the layered compound by selectively removing Li or Na ions contained in the layered compound. By providing, a solution to this problem was sought.

According to the method for preparing a layered FeP compound according to the present invention, a conventional 3D-structured bulk FeP can be prepared as a compound having a completely different crystal structure and a two-dimensional layered crystal structure, and specifically, the space group is P4 /nmm, and can be prepared as a compound having a layered crystal structure in which the crystal system is tetragonal.

First, as step (1), lithium (Li) or sodium (Na) powder; After mixing iron (Fe) powder and phosphorus (P) powder, heat treatment and cooling are performed sequentially to obtain a compound represented by LiFeP or NaFeP having a layered crystal structure.

The mixture may be heat-treated after being sealed in a reaction vessel, and the inside of the reaction vessel may be maintained in an inert gas or vacuum atmosphere. The inert gas may preferably be nitrogen (N ₂ ) or argon (Ar) gas.

In addition, the material of the reaction vessel may be, for example, alumina, molybdenum, tungsten, or quartz, but any material that does not react with the sample and does not break at high temperature may be used without limitation.

When the step (1) is performed on Li powder, Fe powder, and P powder, the layered compound has a formula of LiFeP. The compound has a crystal structure in which the space group is P4/nmm and the crystal system is tetragonal.

3 shows an SEM image of a layered LiFeP compound and a layered FeP compound according to a preferred embodiment of the present invention, and FIG. 6 is a layered LiFeP compound and a layered FeP according to a preferred embodiment of the present invention. It is a graph showing the XRD diffraction pattern of the compound together with the reference diffraction pattern of the LiFeP material.

Referring to FIG. 3, it can be seen that the LiFeP compound obtained in step (1) has a layered structure, and referring to FIG. 6, the crystal structure of the layered LiFeP compound of the present invention can be confirmed.

In addition, when step (1) is performed by mixing Na powder, Fe powder, and P powder, the layered compound has a formula of NaFeP. The compound also has a crystal structure in which the space group is P4/nmm and the hard crystal system is a tetragonal system.

10 is a SEM image of the layered NaFeP compound according to an embodiment of the present invention. Referring to FIG. 10, it can be seen that the LiFeP compound obtained in step (1) has a layered structure.

As can be seen in FIGS. 3 and 10, the LiFeP or NaFeP compound prepared through the step (1) has a 2D crystal structure, unlike the conventional FeP compound having a 3D bulk crystal structure. It can be seen that the rho also has a layered structure. The layered LiFeP or NaFeP compound can be prepared in a layered FeP compound by selectively removing Li ions in the LiFeP compound or Na ions in the NaFeP compound in step (2), which will be described later. There is no change of.

In the step (1), the heat treatment may be performed for 3 days to 5 days at a temperature of 750°C to 850°C for a mixture of Li powder, Fe powder, and P powder.

More preferably, the heat treatment may be performed at a temperature of 750°C to 800°C. If the heat treatment is performed at an excessively low temperature of less than 750°C, there may be a problem in that the sintering reaction of the mixture is not completed, so that unreacted raw materials remain, and accordingly, the yield of the layered LiFeP produced is lowered. There may be a problem such as becoming. In addition, when the heat treatment temperature is performed at an excessively high temperature exceeding 850° C., Li ions may be vaporized, and in this case, the reaction vessel used during the sintering reaction is damaged or the yield of the layered LiFeP to be manufactured decreases. There may be a problem.

In addition, if the heat treatment time is too short (less than 3 days), the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and there may be problems such as lowering the yield of the layered LiFeP produced accordingly. have. In addition, the progress of the reaction according to the heat treatment is sufficiently completed in about 5 days, and if the heat treatment time exceeds 5 days, the manufacturing process time may be unnecessarily extended.

The process of cooling after heat treatment in step (1) is necessary for the crystallization of LiFeP, and the size of a single crystal of the crystal may change depending on the cooling rate.

/시간의 감온 속도로 수행될 수 있으며, 이를 통해 열처리된 층상형 화합물을 단결정화할 수 있다. 상기 감온 속도로 냉각할 경우 제조되는 층상형 화합물 및 층상형 FeP의 단결정 크기가 커질 수 있다. 상기 층상형 FeP의 단결정 크기가 커질수록 입자의 그레인 바운더리(grain boundary)가 감소하여 전하 이동도가 증가할 수 있고, 층상형 FeP 화합물을 박리할 때 박리되는 FeP 나노시트의 종횡비(aspect ratio)가 증가할 수 있다.According to an embodiment of the present invention, the cooling is 0.5 ℃ / hour to 2

It can be carried out at a temperature reduction rate of / hour, through which the heat-treated layered compound can be single-crystallized. When cooling at the temperature reduction rate, the size of a single crystal of the layered compound and the layered FeP to be prepared may increase. As the size of the single crystal of the layered FeP increases, the grain boundary of the particles decreases, so that the charge mobility may increase, and the aspect ratio of the FeP nanosheets peeled off when the layered FeP compound is peeled off is increased. Can increase.

/시간 미만일 경우, Li 이온의 기화로 인해 제조되는 물질의 조성 변화가 발생할 수 있고, 상기 감온 속도가 2

/시간을 초과할 경우, 단결정이 충분히 성장하지 못하여 제조되는 LiFeP가 다결정화될 수 있다.If the above temperature reduction rate is 0.5

If it is less than / hour, a change in the composition of the manufactured material may occur due to vaporization of Li ions, and the temperature reduction rate is 2

If it exceeds /hour, the single crystal may not sufficiently grow, and thus the manufactured LiFeP may be polycrystallized.

In addition, when the step (1) is performed on Na powder, Fe powder, and P powder, the heat treatment may be performed at a temperature of 800°C to 900°C for 3 to 5 days.

More preferably, the heat treatment temperature may be 830°C to 870°C. If the heat treatment is performed at less than 800°C, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered NaFeP produced may be lowered. In addition, when the heat treatment temperature exceeds 900°C, Na ions may be vaporized, and thus the reaction vessel used during the sintering reaction may be damaged, or the yield of the layered NaFeP compound to be produced may be reduced. have.

In addition, if the heat treatment time is less than 3 days, the sintering reaction of the mixture may not be completed and unreacted raw materials may remain, thereby reducing the yield of the layered NaFeP. I can. In addition, the progress of the reaction according to the heat treatment is sufficiently completed in about 5 days, and if the heat treatment time exceeds 5 days, the manufacturing process time may be unnecessarily extended.

In addition, the cooling process after the heat treatment is necessary for crystallization of the layered NaFeP compound, and the size of a single crystal of the crystal may change depending on the cooling rate.

Preferably, the cooling step may be performed at a temperature reduction rate of 0.5°C/hour to 2°C/hour. Through this, the heat-treated layered compound can be single-crystallized. When cooling at the temperature reduction rate, the size of a single crystal of the layered compound and the layered FeP to be prepared may increase. As the single crystal size of the layered FeP increases, the grain boundary of the particles decreases, so that charge mobility may increase, and the aspect ratio of the FeP nanosheets that are peeled off when the layered FeP is peeled may increase. have.

If the temperature reduction rate is less than 0.5°C/hour, there may be a problem that the composition of the manufactured material is changed due to the vaporization of Na ions, and when the temperature reduction rate exceeds 2°C/hour, the NaFeP manufactured Can be polycrystallized.

According to a preferred embodiment of the present invention, the LiFeP or NaFeP compound obtained in step (1) may have a crystal structure in which Li ions or Na ions are intercalated between each layer in the crystal of the layered FeP compound. .

1 is a view schematically showing a crystal structure of a layered LiFeP compound according to a preferred embodiment of the present invention and a crystal structure of a layered FeP compound according to a preferred embodiment of the present invention.

Referring to FIG. 1, it can be seen that the crystal structure of the layered LiFeP compound is that FeP has a layered crystal structure, and Li ions are intercalated therebetween.

By having such a crystal structure, it is possible to prepare an FeP compound having a layered crystal structure without changing the crystal structure by selectively removing only Li ions or Na ions in step (2), which will be described later.

Next, as step (2), a layered FeP compound is prepared by selectively removing Li ions or Na ions contained in the layered compound prepared in step (1).

When the layered compound is LiFeP, Li ions contained in the LiFeP may be removed by treatment with at least one selected from water, ethanol, and isopropanol, preferably with a solvent containing water.

When the layered compound is NaFeP, Na ions included in the NaFeP may be removed by treatment with at least one selected from water, ethanol, and isopropanol, preferably with a solvent containing water.

이상의 온도, 더욱 바람직하게는 20℃ 내지 60

의 온도에서 수행될 수 있다. 만일 20

미만에서 수행될 경우, 알칼리 금속 이온이 목적하는 수준으로 제거되지 않거나 제조되는 층상형 화합물의 층상형 구조가 붕괴될 수 있고, 60

를 초과하는 온도에서 수행될 경우 제조되는 층상형 화합물의 층상형 구조가 붕괴될 수 있다. 또한, 20℃ 내지 60

의 온도에서 수행될 경우 제조되는 층상형 화합물의 층상형 구조를 유지하면서 알칼리 금속 이온 제거율이 우수할 수 있다.In addition, the step (2) may be performed at a temperature at which the removal reaction of the alkali metal ions can occur smoothly, and the temperature may vary depending on the composition of the mixed solution, but preferably 20

The above temperature, more preferably 20° C. to 60

It can be carried out at a temperature of. If 20

If carried out below, the alkali metal ions may not be removed to the desired level or the layered structure of the layered compound to be prepared may collapse, and 60

When carried out at a temperature exceeding the layered structure of the layered compound to be prepared may collapse. In addition, 20 ℃ to 60

When performed at a temperature of, alkali metal ion removal rate may be excellent while maintaining the layered structure of the layered compound to be prepared.

In addition, step (2) may be performed multiple times depending on the composition of the mixed solution and the removal rate of Li and Na ions, but is preferably performed once to maintain the layered structure of the layered FeP to be prepared.

1 is a view schematically showing a crystal structure of a layered LiFeP compound prepared by a method according to a preferred embodiment of the present invention and a crystal structure of a layered FeP compound according to a preferred embodiment of the present invention.

Referring to FIG. 1, when Li ions are removed by treating the layered LiFeP compound with the solvent, only Li ions are selectively removed without changing the crystal structure in the layered LiFeP, and the crystal structure of the prepared layered FeP compound It can be seen that is the same as the layered LiFeP.

Hereinafter, the layered FeP compound of the present invention will be described.

The present invention provides a layered FeP compound having a layered crystal structure in which a space group is P4/nmm and a crystal system is tetragonal, and the layered FeP compound is a conventional FeP compound Unlike having a 3D bulk crystal structure, it has a layered crystal structure, and can be easily peeled off with FeP nanosheets. Therefore, compared to the conventional FeP compound, it has a significantly larger surface area, and when used as a catalyst for electrochemical water decomposition, there is an advantage of realizing excellent activity.

According to a preferred embodiment of the present invention, the layered FeP compound is 14.7±0.2, 28.4±0.2, 37.5±0.2, 46.0 in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It can have peaks at 2θ values of ±0.2, 48.8±0.2, 51.8±0.2, and 57.9±0.2. This can be confirmed through the XRD analysis results of the layered FeP of FIG. 6.

In addition, the layered FeP compound may not have a peak at 2θ values of 34.2±0.2, 39.1±0.2, and 58.8±0.2 in an X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. , This can be confirmed through the XRD analysis results of the layered FeP of FIG. 6.

In addition, according to a preferred embodiment of the present invention, the layered FeP compound of the present invention may have a maximum value in a region of 650 nm to 670 nm in a region of a wavelength of 630 nm to 800 nm of a photoluminescence emission graph.

Next, the FeP nanosheet of the present invention will be described.

The FeP nanosheet according to the present invention can be obtained by peeling from the layered FeP compound according to the present invention, and has a crystal structure in which the space group is P4/nmm and the crystal system is tetragonal. Have.

The method of releasing the FeP nanosheets from the layered FeP may use a method of peeling a layered material known in the art, for example, a method of peeling with energy by ultrasonic waves, a method of peeling by intrusion of a solvent, and a tape. Any one of the used peeling method and the peeling method using a material having an adhesive surface may be used.

According to a preferred embodiment of the present invention, the FeP nanosheet may have a thickness of 30 nm or less. If the thickness exceeds 30 nm, the surface area of the FeP nanosheet decreases, and thus the activity when used as a catalyst may decrease.

Next, the catalyst of the present invention will be described.

The catalyst of the present invention includes the FeP nanosheet of the present invention as described above.

Therefore, it has a layered crystal structure in which the space group is P4/nmm and the crystal system is a tetragonal system, and has a large specific surface area due to its thin thickness, so that the catalytic activity is superior to that of a catalyst including a conventional 3D bulk type FeP.

Although an embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in the present specification, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same idea. It will be possible to easily propose other embodiments by changing, deleting, adding, etc., but it will be said that this is also within the spirit scope of the present invention.

[Example]

Preparation Example 1-Preparation of LiFeP compound

After mixing quantitative Fe powder, P powder, and Li powder, it was sealed in a quartz tube in an inert gas atmosphere. The quartz tube containing the sample was heat-treated at 760°C for 3 days. Thereafter, for recrystallization of LiFeP, a layered LiFeP single crystal compound having a crystal structure in which the space group was P4/nmm and the crystal system was tetragonal was obtained by slow cooling at a temperature reduction rate of 2°C/hour.

Preparation Example 2-Preparation of NaFeP compound

After mixing quantitative Fe powder, P powder, and Na powder, they were sealed in a quartz tube in an inert gas atmosphere. The quartz tube containing the sample was heat-treated at 850°C for 3 days. Thereafter, for recrystallization of NaFeP, a layered NaFeP single crystal compound having a crystal structure in which the space group was P4/nmm and the crystal system was tetragonal was obtained by slow cooling at a temperature reduction rate of 2°C/hour.

Example 1-Preparation of layered FeP compound

LiFeP prepared in Preparation Example 1 was mixed with deionized water and reacted for 3 days to remove Li ions from the LiFeP, through which a layered FeP compound having a space group of P4/nmm and a crystal system of a tetragonal system was prepared.

Example 2-Preparation of layered FeP compound

NaFeP prepared in Preparation Example 2 was washed with ethanol for 30 minutes, mixed with deionized water, and reacted for 3 days to remove Na ions from the NaFeP, through which the space group was P4/nmm and the crystal system was tetragonal. A layered FeP compound was prepared.

Example 3-Preparation of FeP nanosheets

The layered FeP prepared in Example 1 was peeled off with a scotch tape (3M) to prepare a FeP nanosheet.

Example 4-Preparation of FeP nanosheets

The layered FeP prepared in Example 2 was peeled off with a scotch tape (3M) to prepare a FeP nanosheet.

Comparative Example 1-Preparation of bulk type FeP compound

The Fe powder and P powder were heat-treated at 1200° C. for 24 hours and then cooled to prepare a 3D bulk FeP compound.

[Experimental Example]

Experimental Example 1-XRD analysis

XRD analysis was performed on the samples prepared according to Preparation Example 1 and Example 1, and the results are shown in FIG. 6. The results of the XRD analysis of LiFeP prepared according to the conventional technique are shown together as a reference.

Referring to Figure 6, it can be seen that the layered LiFeP and FeP compounds according to Preparation Example 1 and Example 1 differ in the XRD diffraction pattern from LiFeP prepared according to the prior art, so that the crystal structure is It can be seen that it is different from LiFeP prepared accordingly.

Specifically, in the XRD pattern of the LiFeP compound according to the prior art, the peak does not appear in the region of 2θ of 40.2±2, whereas the compounds according to Preparation Example 1 and Example 1 show sharp peaks in the corresponding region. It was confirmed that the layered LiFeP compound or the layered FeP compound according to the invention had a different crystal structure compared to the 3D bulk type LiFeP.

Experimental Example 2-SEM analysis

SEM images of samples prepared according to Preparation Example 1 and Example 1 were taken, and the results are shown in FIG. 3. In addition, a SEM image of the sample prepared according to Preparation Example 2 was taken and shown in FIG. 10.

3 (left) and 10, it can be seen that LiFeP of Preparation Example 1 and NaFeP of Preparation Example 2 have a layered structure. In addition, when checking FIG. 3 (right), it was confirmed that FeP prepared from Preparation Example 1 also has a layered structure.

Experimental Example 3-STEM analysis

STEM analysis was performed on the sample prepared according to Example 3, and the results are shown in FIGS. 9A to 9C, and STEM analysis was performed on the sample prepared according to Example 4, and the results are shown in FIG. 13.

Referring to FIGS. 9A to 9C and 13, it was confirmed that after the Li ions or Na ions of the LiFeP and NaFeP compounds were removed, only the tetragonal layer remained in the FeP compound to have a layer crystal structure.

Experimental Example 4-AFM analysis

AFM analysis was performed on the FeP nanosheets according to Example 3, and the results are shown in FIG. 7.

Referring to FIG. 7, it was confirmed that the FeP nanosheet according to Example 3 was peeled to a thickness of 30 nm or less.

Experimental Example 5-PL analysis

The sample of Example 1 was subjected to PL emission analysis, and the results are shown in Figs. 8A and 8B.

Referring to FIG. 8B, it can be seen that the layered FeP compound of Example 1 is a semiconductor material having a band gap through the PL phenomenon occurring at a specific wavelength. Accordingly, it was found that the FeP compound prepared according to Example 1, unlike the FeP material without the bonded band wrap, had significantly different electrochemical properties from the conventional 3D bulk FeP compound.

Claims (14)

(1) lithium (Li) or sodium (Na) powder; It has a layered crystal structure in which the space group is P4/nmm and the crystal system is tetragonal by sequentially heat treatment and cooling after mixing iron (Fe) powder and phosphorus (P) powder. , Obtaining a layered compound represented by the formula LiFeP or NaFeP; And
(2) preparing a layered FeP compound without changing the crystal structure of the layered compound by selectively removing Li or Na ions contained in the layered compound. The method of claim 1,
The heat treatment in step (1) is a method for producing a layered FeP compound, characterized in that after mixing Li powder, Fe powder, and P powder, heat treatment is performed at a temperature of 750°C to 850°C for 3 to 5 days. . The method of claim 1,
The heat treatment during the step (1) is a method of producing a layered FeP compound, characterized in that after mixing Na powder, Fe powder, and P powder, heat treatment is performed at 800°C to 900°C for 3 to 5 days. The method of claim 1,
The cooling step of the step (1) is a method for producing a layered FeP compound, characterized in that performed at a temperature reduction rate of 0.5 ℃ / h to 2.0 ℃ / h. The method of claim 1,
The step (2) is a method for producing a layered FeP compound, characterized in that Li or Na ions are selectively removed by treating a solvent containing at least one selected from water, ethanol, and isopropanol. The method of claim 5,
The method of producing a layered FeP compound, characterized in that the treatment of the solvent is carried out at a temperature of 20 ℃ to 60 ℃. The method of claim 1,
The LiFeP or NaFeP compound obtained in step (1) has a crystal structure in which Li ions or Na ions are intercalated between each layer in the crystal of the layered FeP compound. A layered FeP compound having a layered crystal structure in which the space group is P4/nmm and the crystal system is tetragonal. The method of claim 8,
The layered FeP compound is 14.7±0.2, 28.4±0.2, 37.5±0.2, 40.2±2 46.0±0.2, 48.8±0.2, in X-ray diffraction diagrams obtained by powder X-ray diffraction using Cu-Ka rays. Layered FeP compound, characterized in that it has peaks at 2θ values of 51.8±0.2 and 57.9±0.2. The method of claim 9,
The layered FeP compound is characterized in that it does not have a peak at 2θ values of 34.2±0.2, 39.1±0.2, and 58.8±0.2 in an X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. Layered FeP compound. The method of claim 8,
The layered FeP compound is a layered FeP compound, characterized in that the maximum value is present in a region of 650nm to 670nm in the region of the wavelength of 630nm to 800nm of the photoluminescence (Photoluminescence) emission graph. The FeP nanosheets peeled from the layered FeP compound according to any one of claims 8 to 11, have a space group of P4/nmm, and have a layered crystal structure of a tetragonal crystal system. The method of claim 12,
FeP nanosheets, characterized in that the thickness is less than 30nm. A catalyst comprising the FeP nanosheet according to claim 12.

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