KR102322024B1 - Graphene hybrid catalyst for Water splitting and Zn-Air battery, and Method thereof - Google Patents

Abstract

A noble metal catalyst used in the prior art has good activity but is expensive and has economic problems. Accordingly, the present invention provides a graphene hybrid catalyst for water decomposition and a zinc-air battery and a method for manufacturing the same, wherein the graphene hybrid catalyst has sufficient active sites on a basal plane, and simultaneously exhibits excellent activity in oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) when the graphene hybrid catalyst is applied to water decomposition and a secondary battery.

Description

Graphene hybrid catalyst for Water splitting and Zn-Air battery, and Method thereof

The present invention provides an oxygen reduction reaction (ORR), a hydrogen evolution reaction (HER) and an oxygen evolution reaction (oxygen evolution reaction, It relates to a graphene hybrid catalyst that exhibits excellent activity at the same time in OER) and a method for preparing the same.

Today, metal-air batteries, fuel cells and water electrolysis have been widely recognized by the scientific community as advanced technologies for large-scale production of clean and renewable energy with environmental friendliness, durability and cost-effectiveness. Important reactions of the above energy system include an oxygen reduction reaction (ORR), a hydrogen evolution reaction (HER), and an oxygen evolution reaction (OER). Conventionally, noble metal-based materials such as platinum (Pt), ruthenium oxide (RuO ₂ ) and iridium oxide (IrO ₂ ) have been used as catalysts for accelerating the above reactions, but they are expensive and difficult to commercialize because they are rare metals. There is this. Therefore, research on the development of inexpensive, environmentally friendly, high activity and powerful catalysts as an alternative to rare metal catalysts is being actively conducted.

As an example of the above study, molybdenum disulfide (MoS ₂ ) is attracting attention as an efficient catalyst. F. Pan, H. Zhang, K. Liu, D. Cullen, K. More, M. Wang, Z. Feng, G. Wang, G. Wu, Y. Li, ACS Catal. According to 2018, 8, 3116 et al., when an accelerator such as cobalt (Co), nickel (Ni), or copper (Cu) is introduced into molybdenum disulfide, two transition metals are present in the structure, which generates more active sites. This has been shown to significantly increase the activity of the catalyst.

The metal sulfide catalyst thus developed is not only strong, but also a catalyst that exhibits an active reaction over a wide range of pH values. Although various structures and forms thereof have been prepared, metal sulfide catalysts are difficult to use in industry because they lack active sites on the basal plane to have uniformity and a large electroactive surface area.

Meanwhile, according to Korean Patent Laid-Open No. 10-2017-0097579, a catalyst structure in which a plurality of nanostructured catalyst particles are dispersed on a support is formed instead of a high-cost platinum-based catalyst. The invention has the effect of increasing economic efficiency and productivity since mass production is possible without loss of precursors.

Furthermore, as interest in multifunctional nanomaterials increases, core-shell nanostructures are a technology that has recently attracted attention because they have a variety of configurations as well as special features. The excellent interaction and charge transfer between core and shell have better electrochemical performance than alloying and doping.

Recently, a catalyst having a core-shell structure has emerged as an electrocatalyst with unique and useful properties. However, pure core-shell nanostructures have poor electrical conductivity, and severe agglomeration may occur due to high surface energy and low ferromagnetism, which may reduce the surface area and active sites.

Korean Patent Publication No. 10-2017-0097579 (published on August 28, 2017)

The present invention was devised in consideration of the above problems, and it is economical instead of the conventional platinum-based catalyst, and has sufficient active sites on the base plane, so that the activity of the core-shell type catalyst is high, as well as oxygen reduction reaction, An attempt is made to prepare a graphene hybrid catalyst that exhibits good activity in a hydrogen evolution reaction and an oxygen evolution reaction.

The graphene hybrid catalyst of the present invention includes a graphene sheet with a surface modified 　; and a nano sheet containing at least a part of the graphene sheet and a metal represented by Formula 1 formed on the surface; and core-shell nanoparticles formed on the nanosheet.

[Formula 　1]

BS ₂

In the formula 　1, 　B is molybdenum (Mo), chromium (Cr), or tungsten (W).

In a preferred embodiment of the present invention, the surface-modified graphene sheet may be characterized in that the graphene is doped with nitrogen (N) and sulfur (S) on the surface of the graphene sheet.

In a preferred embodiment of the present invention, the core-shell nanoparticles include a core including a metal compound represented by the following formula (2); and a shell including a metal sulfide represented by Formula 3 below.

[Formula 2]

AS _x

In Formula 2, A is cobalt (Co), rhodium (Rh) or iridium (Ir), and x is 0 to 4,

[Formula 3]

C ₂ BS ₄

In Formula 3, B is molybdenum (Mo), chromium (Cr), or tungsten (W), and C is copper (Cu), gold (Au), or silver (Ag).

In a preferred embodiment of the present invention, the graphene hybrid catalyst may be used in a water decomposition device or a secondary battery.

Another object of the present invention is a method for producing a graphene hybrid catalyst comprising: a first step of preparing a mixed solution of graphene oxide and water; Step 2 of adding metal ions and precursor to the mixed solution and performing ultrasonic treatment; Step 3 of adding sulfur and precursor to the solution that performed step 2 and stirring; Step 4, in which the solution stirred in step 3 is dried to obtain a solid powder; Step 5 of performing the first heat treatment and the second heat treatment on the solid powder; It may include step 6 of cooling the solid powder that has undergone the 5 step heat treatment to room temperature to obtain a hybrid catalyst.

In a preferred embodiment of the present invention, the ultrasonic treatment in the second step is performed for 60 to 100 minutes, and the drying in the fourth step may include being performed at a temperature of 60 to 100° C. for 12 to 15 hours. .

In a preferred embodiment of the present invention, the sulfur precursor is at least two selected from ammonium tetrathiomolybdate, thiourea, tetrathiomolybdate and thioacetamide. may include.

In a preferred embodiment of the present invention, the sulfur precursor may include ammonium tetrathiomolybdate and thiourea in a weight ratio of 1:80 to 1:110 by weight.

In a preferred embodiment of the present invention, the primary heat treatment is argon (Ar) and hydrogen (H ₂ ) under a gas containing argon (Ar) and hydrogen (H 2 ) in a volume ratio of 1: 1.5 to 1: 4.0, heating ^{at 1 to 3 ° C. min -1} After heating to 450 ~ 550 ℃ at a rate, it can be carried out at 450 ~ 550 ℃ for 60 ~ 100 minutes.

In a preferred embodiment of the present invention, the secondary heat treatment is ^{heated to 850 ~ 950 ℃ under an inert gas at a heating rate of 4 ~ 6 ℃ min -1} , and then at 850 ~ 950 ℃ for 3 to 5 hours can be performed.

The graphene hybrid catalyst of the present invention is not only economical, but also has an effect of showing good activity in oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction, and is used in a water decomposition device and/or secondary battery by the production method of the present invention. A graphene hybrid catalyst can be prepared.

1 is a schematic diagram of a method for preparing a graphene hybrid catalyst.
2 (a) to (c) are field-emission scanning electron microscopy (FE-SEM) images, specifically (a) is an image of the catalyst prepared in Comparative Example 2, (b) ) to (c) are images of the catalyst prepared in Example 1, (d) to (e) are transmission electron microscopy (TEM) images, specifically (d) is prepared in Comparative Example 2 is an image of the catalyst, (e) to (f) are images of the catalyst prepared in Example 1, (g) is the catalyst prepared in Example 1 X-ray energy dispersive analyzer (EDAX; Energy dispersive X- ray analysis), and (h) to (i) are images of the catalyst prepared in Example 1 observed by high resolution transmission electron microscopy (HR-TEM).
3(a) is an image of the catalyst prepared in Example 1 observed with a scanning-transmission electron microscope (STEM), and (b) to (g) are images of the catalyst prepared in Example 1 Color mapping was performed by analysis using energy dispersive spectrometry (EDS), and cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen (N) were sequentially performed. and an image of carbon (C), (o) is an X-ray diffraction pattern (XRD) analysis image, (I) of the image is an analysis of the catalyst prepared in Comparative Example 1, (II) is the analysis of the catalyst prepared in Comparative Example 2, (III) is the analysis of the catalyst prepared in Example 1, (p) is the specific surface area of the catalyst prepared in Example 1 ) and the inserted image are images showing the pore distribution.
4 is an image obtained by X-ray Photoelectron Spectroscopy (XPS) analysis. (a) to (c) are graphs of binding energy of the catalyst prepared in Example 1, respectively, C 1s, N 1s, S 2p. , (e) is a Co 2p graph of the catalyst prepared in Example 1 and Comparative Example 4, and (f) is a Cu 2p graph of the catalyst prepared in Example 1 and Comparative Example 3.
5 (a) is a cyclic voltammetry (CV) curve graph of the catalyst prepared in Example 1, (b) is a linear injection of the catalyst prepared in Example 1 and Comparative Examples 1 to 5 It is a linear sweep voltammetry (LSV) curve graph, (c) is the Tafel slopes of the catalysts prepared in Example 1 and Comparative Examples 1 to 5, and (d) is Example 1 according to the potential The KL slope and inserted image of the catalyst prepared in It is a graph evaluating the stability of the prepared catalyst during long-term operation using chronoamperometry, and (f) is a graph evaluating the durability of the catalysts prepared in Example 1 and Comparative Example 5 in methanol.
6 (a) is a linear sweep voltammetry (LSV) curve graph when the catalysts prepared in Example 1 and Comparative Examples 1 to 5 react with hydrogen evolution, (b) is Example 1 and Tafel slopes are the Tafel slopes when the catalysts prepared in Comparative Examples 1 to 5 undergo a hydrogen evolution reaction, and (c) is a chronoamperometric method ( chronoamperometry) was used to evaluate stability during long-term operation, and (d) to (e) are linear scanning potentials (LSV) when the catalysts prepared in Example 1 and Comparative Examples 1 to 5 react with oxygen; Linear sweep voltammetry curve graph and Tafel slopes, (f) is a graph evaluating the stability of the catalyst prepared in Example 1 and Comparative Example 6 using chronoamperometry for a long time operation, and ( Inset image) is a linear sweep voltammetry (LSV) curve graph after operating Example 1 for 33 hours, (g) is (1) Example 1, (2) Comparative Example 3, (3) Comparative Example 4, (4) Comparative Examples 2 and (5) is a graph measuring the electrochemical impedance spectroscopy (EIS) of the catalysts prepared in Comparative Example 1, (h) is prepared in Example 1 at 0.92 ~ 1.02V It is a cyclic voltammetry (CV) curve graph of the catalyst, and (i) a graph showing the double layer capacitance _{(C dl , double layer capacitance) of the catalysts prepared in Example 1 and Comparative Examples 1 to 4} am.
Figure 7 (a) is a linear scanning potential (LSV; Linear sweep voltammetry) curve graph of the water decomposition device prepared in Preparation Example 1 and Comparative Preparation Example 1, (b) is an image taken of the apparatus of Preparation Example 1. , (d) is a graph comparing the stability of the water decomposition device prepared in Preparation Example 1 and Comparative Preparation Example 1, (e) is a linear scanning potential (LSV) before and after 25 hours of operation of the water decomposition device prepared in Preparation Example 1 ; Linear sweep voltammetry) curve graph, (f) to (i) are SEM, TEM, HR-TEM, and STEM images of the catalyst prepared in Example 1, (j) to (o) are carried out after oxygen evolution reaction The catalyst prepared in Example 1 was analyzed by energy dispersive spectrometry (EDS) to perform color mapping, and each of cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen Images for (N) and carbon (C).
(a) of FIG. 8 is a linear sweep voltammetry (LSV) curve graph of the catalyst prepared in Example 1, showing the potential difference between the oxygen evolution reaction and the oxygen reduction reaction, (b) is a preparation example 2 is a configuration image of the secondary battery, (c) is a cell voltage measurement image of the secondary battery prepared in Preparation Example 2, (d) is a cell voltage measurement image of the secondary battery manufactured in Preparation Example 2 connected in series , (e) is an OCP measurement graph of the secondary battery prepared in Preparation Example 2 and Comparative Preparation Example 2, (f) is a graph showing the polarization and power density of the secondary battery prepared in Preparation Example 2 and Comparative Preparation Example 2 and (h) is a discharge polarization curve of the secondary batteries prepared in Preparation Example 2 and Comparative Preparation Example 2, and the inserted image is a series of the secondary batteries manufactured in Preparation Example 2 connected to an LED. An image, (i) is an image obtained by supplying power to the water decomposition device by connecting two secondary batteries manufactured in Preparation Example 2 in series.
9 is an image taken with a scanning electron microscope (SEM) of the catalyst prepared in Comparative Example 1.
10 is a graph showing the analysis performed on the catalyst prepared in Comparative Example 2 by an X-ray energy dispersive analyzer (EDAX; Energy dispersive X-ray analysis).
11 (a) is an image of the catalyst prepared in Comparative Example 2 observed with a scanning-transmission electron microscope (STEM), (b) to (e) are the catalyst prepared in Comparative Example 2 It is an image of carbon (C), nitrogen (N), sulfur (S), and molybdenum (Mo) in order by color mapping using EDS.
12 is related to the catalyst prepared in Comparative Example 2, specifically, (a) is an image taken with a transmission electron microscope (TEM), (b) is a measurement of the thickness of the selected region, (c) is a graph showing analysis performed using an atomic-force microscopy (AFM).
13 is a graph showing the specific surface area and (inset image) pore size distribution of the catalyst prepared in Comparative Example 2;
14 (a) to (d) relate to the catalyst prepared in Example 1, and a core composed of _{CoS x and a shell composed of Cu 2} MoS ₄ were examined by high resolution transmission electron microscopy (HR-TEM). ) is an image analyzed using
15 is a catalyst prepared in Comparative Example 4, (a) to (b) are scanning electron microscope (SEM) images, (c) is a CoS _x nanoparticle distribution diagram corresponding to the core, (d) is It is a graph analyzed using energy dispersive spectrometry (EDS).
16 is a catalyst prepared in Comparative Example 3, (a) to (b) are scanning electron microscope (SEM) images, (c) is a Cu ₂ MoS ₄ nanoparticle distribution diagram corresponding to the shell, (d) ) is a graph analyzed by EDS.
17 is a graph showing the X-ray diffraction patterns (XRD) analysis of the catalysts prepared in Comparative Examples 3 and 4;
18 is a graph of the catalysts prepared in Preparation Example 1, Example 1 and Comparative Example 1 analyzed by Raman spectroscopy.
19 is a survey spectrum of XPS. Specifically, (a) is an analysis of the catalyst prepared in Comparative Example 1, (b) is an analysis of the catalyst prepared in Comparative Example 2, (c) is The catalyst prepared in Comparative Example 3 is analyzed, (d) is an analysis of the catalyst prepared in Comparative Example 4, and (e) is an analysis of the catalyst prepared in Example 1.
20 is a linear sweep voltammetry (LSV) curve graph and a KL slope graph therefor, (a) to (b) are graphs analyzing the catalyst prepared in Comparative Example 4, (c) to (d) ) is a graph analyzing the catalyst prepared in Comparative Example 3, (e) to (f) are graphs analyzing the catalyst prepared in Comparative Example 2, (g) to (h) are graphs prepared in Comparative Example 1 It is a graph analyzing the catalyst.
21 is an analysis performed using a rotating ring-disk electrode (RRDE) during the oxygen reduction reaction, specifically (a) is prepared in Example 1 and Comparative Examples 1 to 5 It is a schematic diagram showing the electron transfer number (n) of the catalyst, (b) is the peroxide (HO ₂ ^- ) of the catalyst prepared in Example 1 and Comparative Examples 1 to 5 It is a graph showing the content of anions as a percentage (%).
22 is a catalyst prepared in Example 1 after the oxygen reduction reaction, (a) is an image taken with a scanning electron microscope (SEM), (b) is an image taken with a transmission electron microscope (TEM), (c) is an image taken with a scanning-transmission electron microscope (STEM), (d) ~ (i) are cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), respectively ), a graph analyzing carbon (C) and nitrogen (N).
23 is a high-resolution XPS spectrum by analyzing the catalyst prepared in Example 1 before and after the oxygen reduction reaction (a) Co 2p, (b) Cu 2p, (c) Mo 3d and (d) It is a graph observing the peak at S 2p.
24 is a graph illustrating the measurement of overvoltage during the hydrogen reduction reaction under 0.1M KOH aqueous solution and ^{scanning rate of 10, 50 mV sec -1} , and 1 on the drawing is the catalyst prepared in Comparative Example 1. , 2 is for the catalyst prepared in Comparative Example 2, 3 is for the catalyst prepared in Comparative Example 3, 4 is for the catalyst prepared in Comparative Example 4, 5 is prepared in Example 1 For the catalyst, 6 is for the catalyst prepared in Comparative Example 5.
25 is a graph showing multi-potentiometry when the catalysts prepared in Example 1 and Comparative Example 5 were subjected to a hydrogen evolution reaction in 0.1 M KOH.
26 is a high-resolution XPS spectrum, by analyzing the catalyst prepared in Example 1 before and after the hydrogen evolution reaction (a) Co 2p, (b) Cu 2p, (c) Mo 3d and (d) It is a graph observing the peak at S 2p.
27 is a graph illustrating the measurement of overvoltage during the oxygen evolution reaction under 0.1M KOH aqueous solution and ^{scanning rate conditions of 10 and 50 mV sec -1} , 2 is for the catalyst prepared in Comparative Example 2, 3 is for the catalyst prepared in Comparative Example 3, 4 is for the catalyst prepared in Comparative Example 4, 5 is prepared in Example 1 For the catalyst, 6 is for the catalyst prepared in Comparative Example 5.
28 is a multi-step chronopotentiometry graph according to the overvoltage of the catalysts prepared in Example 1 and Comparative Example 6 in an oxygen evolution reaction.
29 is a graph of EDAX analysis performed on the catalyst prepared in Example 1 after the oxygen evolution reaction, and the inserted image shows the percentage (%) of each element after the oxygen evolution reaction.
30 is a high-resolution XPS spectrum by analyzing the catalyst prepared in Example 1 before and after the oxygen evolution reaction (a) Co 2p, (b) Cu 2p, (c) Mo 3d and (d) It is a graph observing the peak at S 2p.
31 is an image of X-ray diffraction patterns (XRD) analysis of the catalyst prepared in Example 1 before and after the oxygen evolution reaction.
32 (a) shows Cu ₂ MoS ₄ (shell), CoS _x (core, x = 0 and x = 2) and CoS _x @Cu ₂ MoS ₄ (core@shell, x = 0 and x = 2) It is a schematic diagram (yellow color means sulfur atom, dark blue color means cobalt atom, red color means copper atom, and cyan color means molybdenum atom), and the structural parameters related thereto are described, (b) ~ ( c) is a graph obtained by calculating the density of states (DOS _{) of CoS x} @Cu ₂ MoS ₄ (core-shell) nanoparticles and CoS _x (core) and Cu ₂ MoS _{4 (shell).}
33 is a graph showing the results of cyclic voltammetry (CV) analysis performed through the CH660D workstation (CH Instruments Inc., USA) device, (a) is the catalyst prepared in Comparative Example 4, (b) is The catalyst prepared in Comparative Example 3, (c) is the catalyst prepared in Comparative Example 2, and (d) is the catalyst prepared in Comparative Example 1.
34 (a) is a photograph of a device for collecting gas by decomposing water under ^{100mA·cm -2} , (b) is a theoretical value and actual value _{of the captured hydrogen (H 2} ) gas and oxygen (O _{2 ) gas} The difference in the obtained values is shown in a graph.

Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. The same reference numerals are assigned to the same or similar elements throughout the specification.

The present invention will be described in more detail through a method for preparing the graphene hybrid catalyst of the present invention.

The method for preparing the catalyst was prepared as schematically schematically shown in Figure 1, and a step of preparing a mixed solution in which graphene, oxide, and water were mixed; Step 2 of adding the mixed solution, metal ions, precursors, and ultrasonication; Step 3 of adding sulfur and precursor to the solution that performed step 2 and stirring; Step 4, in which the solution stirred in step 3 is dried to obtain a solid powder; Step 5 of performing the first heat treatment and the second heat treatment on the solid powder; and step 6 of cooling the solid powder that has been subjected to the heat treatment of step 5 to room temperature to obtain a hybrid catalyst.

Graphene oxide (GO, graphene oxide) prepared in step 1 may be reduced graphene oxide (rGO, reduced graphene oxide), which is a known method as Hummer's method or a modified Hummer method ( modified Hummer's method), but is not particularly limited thereto.

Next, the metal ion precursor of the second step is ruthenium (Ru), rhodium (Rh), molybdenum (Mo), osmium (Os), iridium (Ir), rhenium (Re), vanadium (V), tungsten (W), Cobalt (Co), iron (Fe), selenium (Se), nickel (Ni), bismuth (Bi), tin (Sn), chromium (Cr), titanium (Ti), cerium (Ce), and copper (Cu) Including a metal ion precursor containing a metal selected from the group consisting of, preferably molybdenum (Mo), It may include one selected from the group consisting of cobalt (Co) and copper (Cu).

In addition, the ultrasonic treatment of the second step may be performed for 60 to 100 minutes, preferably for 60 to 90 minutes.

Next, the sulfur precursor input in step 3 includes at least two selected from ammonium tetrathiomolybdate, thiourea, tetrathiomolybdate and thioacetamide. and preferably ammonium tetrathiomolybdate and thiourea.

In addition, as the sulfur precursor, ammonium tetrathiomolybdate and thiourea may be included in a weight ratio of 1:80 to 1:110, preferably 1:85 to 1:105 by weight. . If the amount of the thiourea group is less than 85 times that of ammonium tetrathiomolybdate, there may be a problem that the core of the nanoparticles is not well formed, and if it exceeds 105 times, there may be a problem that the reaction is inhibited. .

Next, the drying in step 4 is carried out at a temperature of 60 ~ 100 ℃, preferably performed at a temperature of 70 ~ 90 ℃, is carried out for 12 ~ 15 hours, preferably it can be carried out for 12 ~ 14 hours have.

The reaction shown by performing the above steps 1 to 4 is as follows.

First, by performing the above steps, nitrogen and sulfur can be uniformly doped on the surface of the graphene sheet. More specifically, referring to FIG. 9 (SEM image taken of NSG), the honeycomb structure of graphene is doped with nitrogen and sulfur. , the graphene surface may have a wrinkled planar structure, and as a result, nanosheets may be uniformly formed on the surface.

In a specifically preferred example, when thiourea and ammonium tetrathiomolybdate are used as sulfur precursors, the thiourea is combined with a metal ion of the metal ion precursor through the reaction of Scheme 1 below. can bind, and as a result form a complex. In this case, the composite may serve to adsorb metal ions to the surface of the graphene sheet, and may serve to form the core of the nanoparticles during the heat treatment process.

[Scheme 1]

In addition, it may be ammonium tetrathiomolybdate, and the sulfur precursor may combine with metal ions adsorbed on the surface of the graphene sheet to form a metal sulfide represented by the following Chemical Formula 3 precipitated around the complex, preferably Preferably, the metal sulfide may be formed through the reaction of Scheme 2 below.

[Formula 3]

C ₂ BS ₄

In Chemical Formula 3, B may be molybdenum (Mo), chromium (Cr) or tungsten (W), preferably molybdenum, and C is copper (Cu), gold (Au) or silver (Ag). may be, preferably copper.

[Scheme 2]

Next, the first heat treatment process of step 5 is performed under argon (Ar) and hydrogen (H ₂ ) gas at a heating rate of 1 to 3 ° C. min ^-1 , preferably 1.5 to 2.5 ° C. min ^-1 It is carried out at a heating rate, and is carried out at a final temperature of 450 to 550° C. for 60 to 100 minutes, and preferably for 60 to 90 minutes.

In addition, the argon (Ar) and hydrogen (H ₂ ) gas is carried out under a gas containing in a volume ratio of 1: 0.25 to 1: 0.67, and preferably in a gas containing in a volume ratio of 1: 0.30 to 1: 0.50. can be If the hydrogen gas is contained in an amount of less than 0.25 times that of the argon gas, a problem may occur that the nanosheets of metal sulfide are not formed properly, and if the hydrogen gas is included in excess of 0.67 times, the reaction occurs as hydrogen gas is added in excess Problems that hinder this may arise. In addition, when the ratio of the gas is out of the scope of the claims, the residual solution may not be removed, and the product separated from the sulfur precursor and the metal ion precursor may not be removed, so there may be a problem that an oxidation reaction may occur.

In addition, the first heat treatment process is characterized in that the solid powder is heat-treated at a final temperature of 450 to 550 °C, preferably at 470 to 530 °C. If the heat treatment is performed at a temperature of less than 450° C., there may be a problem that the nano-sheet is not properly formed, and when the heat treatment is performed at a temperature exceeding 550° C., there may be a problem that the nano-sheet is decomposed under hydrogen gas.

The sulfur precursor and hydrogen gas remaining unreacted through the first heat treatment process may react to form a nanosheet including a metal sulfide represented by the following Chemical Formula 1, and as a preferred example, thiourea ( thiourea) and ammonium tetrathiomolybdate, the remaining ammonium tetrathiomolybdate may react with hydrogen gas through the reaction of Scheme 3 below to form nanosheets.

[Formula 　1]

BS ₂

In the formula 　1, 　B may be molybdenum (Mo), chromium (Cr), or tungsten (W), preferably molybdenum.

[Scheme 3]

Next, the secondary heat treatment process of step 5 ^{is performed under an inert gas at a heating rate of 4 to 6 °C min -1} , preferably at a heating rate of 4.5 to 5.5 °C min ^-1 , and a final temperature of 850 It may be characterized in that it is carried out at ~ 950 ° C. for 3 to 5 hours, preferably for 3 to 4 hours.

In this case, the inert gas may be one or more of helium (He), argon (Ar), neon (Ne), and krypton (Kr), but may preferably include argon.

In addition, the second heat treatment process includes heat-treating the solid powder subjected to the first heat treatment at a final temperature of 850 to 950° C., preferably heat-treating at 870 to 930° C. If the heat treatment is performed at a temperature of less than 850 ° C, sulfur is not separated from the sulfur precursor, so there may be a problem that the core of nanoparticles cannot be formed. There may be problems that may cause deformation of the

Through the secondary heat treatment process, sulfur ions may be separated from the sulfur precursor, and a metal compound represented by the following Chemical Formula 2 may be formed by combining the sulfur precursor included in the complex with the separated sulfur, a preferred example When thiourea and ammonium tetrathiomolybdate are used as sulfur precursors, sulfur ions can be separated from ammonium tetrathiomolybdate, and thiourea is replaced with sulfur in the complex, so that the following formula The metal compound represented by 2 may be formed, and specifically, it may be formed through the reaction of Scheme 4 below. As a result, the metal sulfide (shell) deposited around the composite may adhere to the surface of the metal compound (core) to form core-shell type nanoparticles.

[Formula 2]

AS _x

In Formula 2, A is cobalt (Co), rhodium (Rh) or iridium (Ir), preferably cobalt, x may be 0 to 4, preferably x = 0 to 3, More preferably, x=0 to 2 may be present.

[Scheme 4]

In Scheme 4, x=0 to 4, preferably x=0 to 3, and more preferably x=0 to 2.

Meanwhile, the first and second heat treatment may include performing a chemical vapor deposition (CVD) system.

Next, the cooling in step 6 includes cooling the solid powder subjected to the first heat treatment and the second heat treatment process at room temperature, and as a result, the hybrid catalyst in the form of a solid powder of the present invention can be prepared.

The graphene hybrid catalyst prepared by the above method includes: a graphene sheet having a modified surface; and a nano sheet containing at least a part of the graphene sheet and a metal represented by Formula 1 formed on the surface; and core-shell nanoparticles formed on the metal sulfide nanosheets.

In addition, the surface-modified graphene sheet includes a graphene sheet surface doped with nitrogen (N) and sulfur (S), and has a thickness of 0.30 to 0.38 nm, preferably 0.32 to 0.36 nm. have.

In addition, the nanosheet including the metal sulfide represented by Formula 1 may have a thickness of 0.54 to 0.7 nm, preferably 0.56 to 0.68 nm. Formula 1 is as follows.

[Formula 　1]

BS ₂

In Formula 1, 　B may be molybdenum (Mo), chromium (Cr), or tungsten (W), preferably molybdenum (Mo).

In addition, the core-shell nanoparticles may include a core including a metal compound represented by the following Chemical Formula 2; and a shell including a metal sulfide represented by the following formula (3).

[Formula 2]

AS _x

In Formula 2, A is cobalt (Co), rhodium (Rh) or iridium (Ir), preferably cobalt (Co), wherein x is 0 to 4, preferably x is 0 to 3 days can and More preferably, x may be 0 to 2. Specifically, it may include A, AS, AS ₂ , AS ₃ and the like, and preferably A, AS, AS ₂ .

In addition, the size of the nanoparticles of Formula 2 in the core part may be 0.16 to 0.25 nm, preferably 0.18 to 0.23 nm.

[Formula 3]

C ₂ BS ₄

In Formula 3, B may be molybdenum (Mo), chromium (Cr), or tungsten (W), preferably molybdenum (Mo). In addition, C may be copper (Cu), gold (Au) or silver (Ag), preferably copper (Cu).

In addition, the chemical formula 3 nanoparticles of the shell portion may have a size of 40 to 60 nm, preferably 42 to 58 nm.

The graphene hybrid electrocatalyst may include water decomposition and used for a negative electrode of a secondary battery.

In the above, the present invention has been mainly described with respect to the embodiment, but this is only an example and does not limit the embodiment of the present invention. It can be seen that various modifications and applications not exemplified above are possible without departing from the scope. For example, each component specifically shown in the embodiment of the present invention can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

[Example]

Preparation Example 1: Preparation of graphene oxide

Graphene oxide was prepared by a modified Hummer's method.

Example 1: Preparation of graphene hybrid catalyst (CoS _x @CuMoS ₄ /MoS ₂ -NSG)

(1) 100 mL of a solution containing 60 mg of the graphene oxide prepared in Preparation Example 1 homogeneously was prepared.

_{(2) 25 mg of each of Co(NO 3} ) ₂ ·6H ₂ O and Cu(NO ₃ ) ₂ ·6H ₂ O as metal ion precursors were added to the solution, followed by ultrasonic treatment for 1 hour.

_{(3) 5 mg of (NH 4} ) ₂ MoS ₄ (ammonium tetrathiomolybdate) and 480 mg of thiourea (thiourea) were added to the solution in which (3) (2) was performed as a sulfur precursor.

(4) The solution in which (3) was carried out was stirred at 80° C. for 12 hours.

(5) The solution subjected to (4) was dried to obtain a solid powder.

(6) The solid powder was heated to 500° C. at a heating rate of ^{2° C. min −1} under a gas containing argon (Ar) and hydrogen (H ₂ ) gas in a volume ratio of 1:0.43, and then at 500° C. The first heat treatment was performed under the condition of temperature for 60 minutes.

(7) The solid powder subjected to the primary heat treatment was ^{heated to 900° C. at a heating rate of 5° C. min −1} under argon (Ar) gas, and then the second heat treatment was performed under a temperature condition of 900° C. for 3 hours.

(8) The solid powder subjected to the secondary heat treatment was cooled to room temperature to obtain a solid powder hybrid catalyst.

Examples 2 to 5: Preparation of graphene hybrid catalyst

A hybrid catalyst was prepared in the same manner as in Example 1, but Examples 2 to 5 were carried out with the temperatures of the first heat treatment and the second heat treatment as shown in Table 1 below.

Example 6 ~ Example 7: Preparation of graphene hybrid catalyst

A graphene hybrid catalyst was prepared in the same manner as in Example 1, but Examples 6 to 7 were performed with the gas composition in the first heat treatment process as shown in Tables 1 to 2 below.

Examples 8 to 9: Preparation of graphene hybrid catalyst

A graphene hybrid catalyst was prepared in the same manner as in Example 1, but Examples 8 to 9 were carried out with the amount of the sulfur precursor added in step (3) as shown in Table 2 below.

Comparative Example 1: Catalyst Preparation (NSG)

(1) 100 mL of a solution containing 60 mg of the graphene oxide prepared in Preparation Example 1 homogeneously was prepared.

(2) The solution was sonicated for 1 hour.

(3) (2) as a sulfur precursor in the solution 480 mg of thiourea was added.

(4) The solution in which (3) was carried out was stirred at 80° C. for 3 hours.

(5) The solution subjected to (4) was dried to obtain a solid powder.

(6) to (8) were prepared in the same manner as the catalyst prepared in Example 1.

Comparative Example 2: Catalyst preparation (MoS ₂ -NSG)

A hybrid catalyst was prepared in the same manner as the catalyst prepared in Comparative Example 1, but as a sulfur precursor (NH ₄ ) ₂ MoS ₄ (ammonium tetrathiomolybdate) 5 mg and thiourea (thiourea) 480 mg in the solution performed in (2) was prepared by adding

Comparative Example 3: Catalyst Preparation (CuMoS ₄ /MoS ₂ -NSG)

100 mL of a solution containing 60 mg of graphene oxide prepared in Preparation Example 1 and _{25 mg of Cu(NO 3} ) ₂ ·6H _{2 O homogeneously was prepared.}

(2) to (8) were prepared in the same manner as in Comparative Example 1.

Comparative Example 4: Catalyst Preparation (CoS _x /MoS ₂ -NSG)

100 mL of a solution containing 60 mg of graphene oxide prepared in Preparation Example 1 and _{25 mg of Co(NO 3} ) ₂ ·6H _{2 O homogeneously was prepared.} And, (2) to (8) were prepared in the same manner as in Comparative Example 1.

Comparative Example 5: Catalyst Preparation (Pt/C)

Platinum on graphitized carbon (Pt/C catalyst) manufactured by Sigma-Aldrich was used.

Comparative Example 6: Catalyst Preparation (RUO ₂ /C)

Ruthenium(IV) oxide (RUO ₂ /C catalyst) manufactured by Sigma-Aldrich was used.

Comparative Example 7 to Comparative Example 10: Preparation of catalyst

A catalyst was prepared in the same manner as in Example 1, but Comparative Examples 7 to 10 were carried out with temperature conditions as shown in Tables 2 to 3 below.

Comparative Example 11 to Comparative Example 12: Preparation of catalyst

A catalyst was prepared in the same manner as in Example 1, but Comparative Examples 11 to 12 were carried out with the gas composition in the first heat treatment process as shown in Table 3 below.

Comparative Example 13 to Comparative Example 14: Catalyst Preparation

A catalyst was prepared in the same manner as in Example 1, but Comparative Examples 13 to 14 were carried out with the amount of the sulfur precursor added in step (3) as shown in Table 3 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Sulfur precursor (mg)
(NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 5 thiourea 480 480 480 480 480 480 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1: 96 1: 96 1: 96 1: 96 1: 96 primary heat treatment Temperature (℃) 500 450 550 500 500 500 gas ratio
(Ar:H ₂ ) 1:0.43 1:0.43 1:0.43 1:0.43 1:0.43 1:0.25 Secondary heat treatment temperature (℃) 900 900 900 850 950 900

Example 7 Example 8 Example 9 Comparative Example 7 Comparative Example 8 Comparative Example 9 Sulfur precursor (mg) (NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 5 thiourea 480 400 550 480 480 480 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1:80 1:110 1: 96 1: 96 1: 96 primary heat treatment Temperature (℃) 500 500 500 420 580 500 gas ratio
(Ar:H ₂ ) 1:0.67 1:0.43 1:0.43 1:0.43 1:0.43 1:0.43 Secondary heat treatment temperature (℃) 900 900 900 900 900 820

Comparative Example 10 Comparative Example 11 Comparative Example 12 Comparative Example 13 Comparative Example 14 Sulfur precursor (mg) (NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 thiourea 480 480 480 300 650 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1: 96 1: 96 1:60 1:130 primary heat treatment Temperature (℃) 500 500 500 500 500 gas ratio
(Ar:H ₂ ) 1:0.43 1:0.11 1:1.00 1:0.43 1:0.43 Secondary heat treatment temperature (℃) 980 900 900 900 900

_{Hereinafter, CoS x} @Cu ₂ MoS ₄ -MoS ₂ /NSG of FIGS. 2 to 33 described in Experimental Examples means the catalyst prepared in Example 1, and GO is the graphene oxide prepared in Preparation Example 1. oxide), NSG means Comparative Example 1, MoS ₂ /NSG means Comparative Example 2, Cu ₂ MoS ₄ -MoS ₂ /NSG means Comparative Example 3, CoS _x -MoS ₂ / NSG means Comparative Example 4, Pt/C means Comparative Example 5, RuO ₂ /C means Comparative Example 6.

Experimental Example 1: Surface structure analysis 1

For surface structure analysis, the catalysts prepared in Example 1 and Comparative Example 2 were subjected to field-emission scanning electron microscopy (FE-SEM) using a Supra 40 VP apparatus (Zeiss Co., Germany). to perform the analysis, and as an analysis equipment, Supra 40 VP equipment (Zeiss. Co., Germany) was used.

First, (a) of FIG. 2 is an image of the catalyst prepared in Comparative Example 2, and it can be seen that the catalyst prepared in Comparative Example 2 has a three-dimensional porous structure connected by a microporous sheet.

On the other hand, Figure 2 (b) ~ (c) is an image of the graphene hybrid catalyst of the catalyst prepared in Example 1, it was confirmed that the core-shell type nanoparticles are dispersed.

Experimental Example 2: Surface structure analysis 2

For surface structure analysis, the catalysts prepared in Example 1 and Comparative Example 2 were subjected to transmission electron microscopy (TEM) using H-7650 equipment (Hitachi Ltd., Japan) and Park-NX10 (Park System Co., Korea) was analyzed using an atomic-force microscopy (AFM).

First, (d) of FIG. 2 is a TEM observation of the catalyst prepared in Comparative Example 2, and it can be seen that the thin metal sulfide nanosheets are closely attached to the graphene layer and have a unique heterogeneous structure.

In addition, as shown in Fig. 2 (d) and Fig. 12 (a) ~ (b), the thickness of the metal sulfide nanosheet was 0.62nm, the thickness of the graphene sheet was found to be 0.34nm, which It corresponds to d(002). In addition, in (a) to (b) of FIG. 12, the catalyst prepared in Comparative Example 2 was observed through TEM, and it was found that a large number of pores were present on the surface of Comparative Example 2.

In addition, the fact that the catalyst prepared in Comparative Example 2 had a mesoporous pore size was also found through the analysis of the catalyst prepared in Comparative Example 2 using AFM in FIG. 12(c).

Meanwhile, FIGS. 2(e) to (f) and FIG. 7(g) are observations of the catalyst prepared in Example 1 by TEM, and nanosheets and core-shell nanosheets of the catalyst prepared in Example 1 It was confirmed that the particles were well formed.

Experimental Example 3: Surface structure analysis 3

For surface structure analysis, the catalyst prepared in Example 1 was analyzed using a high resolution transmission electron microscopy (HR-TEM) using H-7650 equipment (Hitachi Ltd., Japan).

First, (h) of FIG. 2 shows that the catalyst prepared in Example 1 was analyzed, and core-shell nanoparticles formed on the metal sulfide nanosheets could be identified.

In addition, in Fig. 2 (i), Fig. 7 (h), and Fig. 14 (a) ~ (d) are analysis performed on the catalyst prepared in Example 1, Co contained in the metal compound corresponding to the core and CoS ₂ nanoparticles were confirmed to have sizes of 0.20 nm (corresponding to d(111)) and 0.28 nm (corresponding to d(200).), respectively, and the metal sulfide nanoparticles corresponding to the shell size were 0.51 nm (corresponding to d(200)). (002).) was confirmed.

Experimental Example 4: Surface structure analysis 4

For surface structure analysis, X-ray energy dispersive X-ray analysis (EDAX) or Energy dispersive spectrometry (EDS) using Supra 40 VP equipment (Zeiss. Co., Germany) as an analysis equipment ) and the catalysts prepared in Example 1 and Comparative Examples 2 to 4 were analyzed.

First, (g) of FIG. 2 shows the EDAX analysis of the catalyst prepared in Example 1, and FIGS. 3 (b) to (g) and (i) to (n) show the catalyst prepared in Example 1 It is an element mapping (mapping) by performing EDS analysis and a graph analyzing it. Specifically, (b) to (g) of Figure 3 relates to the catalyst prepared in Example 1, in order cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen (N) ), are color mapping images for carbon (C), (i) to (n) are cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen (N), carbon ( It is an analysis graph for C). Through this, it was found that the catalyst prepared in Example 1 had all of the elements cobalt (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen (N), and carbon (C).

In addition, (g) of Figure 2 is a graph performed by EDAX analysis of the catalyst prepared in Example 1, copper (Cu), cobalt (Co), molybdenum (Mo), sulfur (S), nitrogen (N) and carbon It was confirmed that each element of (C) was present.

On the other hand, Figure 10 shows the EDAX analysis of the catalyst prepared in Comparative Example 2, and it can be confirmed that the elements of carbon (C), nitrogen (N), oxygen (O), molybdenum (Mo) and sulfur (S) are present. It was confirmed that each element was properly distributed in the measurement range.

In addition, (b) to (e) of FIG. 11 are color-mapped by EDS analysis of the catalyst prepared in Comparative Example 2, respectively, carbon (C), nitrogen (N), sulfur (S) and molybdenum (Mo) elements. , and through this, it was possible to confirm the existence of each element.

On the other hand, FIGS. 15 (d) and 16 (d) are graphs in which the catalysts prepared in Comparative Examples 4 and 3 were analyzed by EDS, respectively, and the presence of each element could be confirmed through this.

Experimental Example 5: Surface structure analysis 5

In order to analyze the surface structure, Example 1, Comparative Example 1, and Comparative Examples 3 to 4 were analyzed with a scanning electron microscope (SEM).

First, in FIG. 7(f), the catalyst prepared in Example 1 was observed, and it was confirmed that the core shell was well formed.

On the other hand, FIG. 9 is an observation of the catalyst prepared in Comparative Example 1, and it can be seen that the surface of the graphene sheet is doped with nitrogen and sulfur to form wrinkles on the surface.

On the other hand, (a) to (b) of FIG. 16 are observations of the catalyst prepared in Comparative Example 3, and the catalyst structure of the catalyst prepared in Comparative Example 3 could be known, and through FIG. 16(c), Comparative Example _{It was confirmed that the Cu 2} MoS ₄ nanoparticles of the catalyst prepared in 3 had an average size of about 50 nm.

On the other hand, FIGS. 15 (a) to (b) are observations of the catalyst prepared in Comparative Example 4, and the catalyst structure of the catalyst prepared in Comparative Example 4 was known, and through FIG. 15 (c), the comparative example _{It was confirmed that the CoS x} nanoparticles corresponding to the core of the catalyst prepared in step 4 had an average size of about 21 nm.

Experimental Example 6: Surface structure analysis 5

In order to analyze the surface structure, the catalysts prepared in Example 1 and Comparative Example 2 were analyzed with a scanning-transmission electron microscope (STEM).

First, (a), (h) and 7 (i) of FIG. 3 are images of observing the catalyst prepared in Example 1, to confirm _{CoS x corresponding to the core and Cu 2} MoS ₄ corresponding to the shell could

On the other hand, (a) of FIG. 11 is an image of the catalyst prepared in Comparative Example 2, and the structure could be confirmed.

Experimental Example 7: Crystal structure analysis 1

To analyze the crystal structures of the catalysts prepared in Preparation Example 1, Example 1 and Comparative Examples 1 to 4, D/Max 2500 V/PC (Rigaku Co., Japan) targeting Cu (at λ = 0.154 nm) ) was analyzed using X-ray diffraction patterns (XRD) or analyzed by Raman spectroscopy.

First, (o) of FIG. 3 is a graph performed by XRD analysis. Looking at this, (I) is an analysis of the catalyst prepared in Comparative Example 1, (II) is an analysis of the catalyst prepared in Comparative Example 2, (III) is an analysis of the catalyst prepared in Example 1. Through this, graphene has a 2θ peak value of ^{25.39 o} corresponding to the crystal lattice d(002), _{and MoS 2} (PDF#37-1492) has the crystal lattice d(002), d(100), d(103) 2θ of ^{14.24 o} , 32.79 ^o , 39.03 ^{o , 43.85 o} , 58.35 ^{o ,} and 60.38 ^o corresponding to , d(006), d(110) and d(008) It was confirmed that it has a peak value. In addition, it was confirmed that the Co phase (PDF#18-0806) of the core part had 2θ peak values of ^{44.63 o} and 51.03 ^o _{corresponding to the crystal lattices d(111) and d(200), and the CoS 2} phase of the core part ( ^{PDF#04-003-2292) is 32.48 o} , 35.98 ^o , 40.74 corresponding to the crystal lattices d(200), d(210), d(211), d(220), d(311) and d(321). ^o , 46.59 ^o , 54.69 ^o and 62.72 ^o were confirmed to have 2θ peak values. In addition, the Cu ₂ MoS ₄ phase of the shell portion is crystal lattice d(002), d(101), d(112), d(103), d(200), d(220), d(204), d(222) and 17.67 ^o for the d (312), 18.76 ^{o, o} 29.20, 32.63 ^{o, o} 33.41, 48.14 ^{o, o} 50.02, 53.21 and 56.80 ^{o o} of 2θ It was confirmed that it has a peak value.

On the other hand, FIG. 18 shows that the graphene sheet prepared in Preparation Example 1, the catalyst prepared in Example 1 and Comparative Example 1 were analyzed by Raman spectroscopy to confirm the chemical structure, and Example 1 is a plane (in plane) ^{showed small peaks corresponding to E 1} _{2 g} (378.8 cm ^-1 ) and A _{1 g} (406.5 cm ^-1 ) in the out of plane, and the difference was 27.7 cm ^-1 , suggesting a hybrid structure. there was.

In addition, the D peak of the catalyst prepared in Example 1 was 1,338 cm ^-1 , the G peak ^{appeared at 1574 cm -1} , and I _D /I _G (intensity) was 1.35. In contrast, the graphene sheet prepared in Preparation Example 1 was 0.78, and the catalyst prepared in Comparative Example 1 was 1.03. Through this, the catalyst prepared in Comparative Example 1 is a form in which nitrogen and sulfur are doped together on the surface of the graphene sheet, and when MoS ₂ nanosheets and core-shell nanoparticles are dispersed, the graphene sheet doped with nitrogen and sulfur becomes more disordered. Could know.

Meanwhile, FIG. 17 shows that the catalysts prepared in Comparative Examples 3 and 4 were analyzed by XRD, and it was confirmed that the preparation was successfully performed by confirming the presence of each crystal phase.

Experimental Example 8: Crystal structure analysis 2

In order to analyze the crystal structures of the catalysts prepared in Example 1 and Comparative Examples 1 to 4, XPS (X-ray Photoelectron Spectroscopy) analysis was performed using Theta Probe equipment (Thermo Fisher Scientific Inc., USA). did.

First, looking at (a) of Figure 4, the catalyst prepared in Example 1 is a graph of binding energy in C 1s, C = C (284.6 eV), CO (286.5 eV), C = O (287.2 eV), It could be seen that OC=O (289.2eV), CN (285.4eV), and CSC (284.0eV) had binding energies, indicating that nitrogen and sulfur were successfully doped into the graphite skeleton of the graphene sheet.

In addition, looking at (b) to (c) of Figure 4, it relates to the catalyst prepared in Example 1, and showed a graph of binding energy in N 1s and S 2p, specifically, in N 1s, three strong A peak was observed, which was pyridinic-N having a binding energy of 394.8 eV, pyrrolic-N having a binding energy of 398.5 eV, and quaternary-N having a binding energy of 401.1 eV, respectively. was found to be composed of In addition, it was confirmed that S2p has binding energy peaks at C-S (163.4 eV), Mo-S (162.6 to 164.3 eV), and Co-S/Cu-S (161.7 eV). Through this, it was confirmed that nitrogen and sulfur were successfully doped.

In addition, (d) of FIG. 4 shows the binding energy in Mo 3d of the catalyst prepared in Example 1, which showed peaks at 228.3, 232.0, 232.6 and 235.5 eV, which are Mo ⁴⁺ 3d _{5/2, respectively.} , Mo ⁴⁺ 3d _3/2 , Mo ⁶⁺ 3d _5/2 and Mo ⁶⁺ 3d _3/2 were found to correspond. Through this, it was found that MoS ₂ nanosheets and core-shell nanoparticles have a strong interaction.

On the other hand, (e) of FIG. 4 means the binding energy in Co 2p of the catalyst prepared in Example 1 and Comparative Example 4, and the binding energy of Co ⁰ and Co ²⁺ of the catalyst prepared in Example 1 and sulfur is It was confirmed that they were 778.3 eV and 794.1 eV, respectively, and the binding energies ^{of Co 0} and Co ²⁺ and sulfur of the catalyst prepared in Comparative Example 4 were 781.1 and 797.4 eV, respectively. Through this, it was confirmed that the catalyst prepared in Example 1 was downshifted by ~1.06 eV compared to the catalyst prepared in Comparative Example 4.

In addition, (f) of FIG. 4 is a comparison of the binding energy graphs in Cu 2p of the catalysts prepared in Example 1 and Comparative Example 4, and showed a similar graph form. At this time, the catalyst prepared in Example 1 showed strong peaks at 932.6 and 952.4 eV, which corresponds to ^{Cu 1+ .} In addition, the catalyst prepared in Example 1 ^{showed two small doublets corresponding to Cu 2+} , which correspond to 934.6 eV, 954.9 eV and 943.2 eV and 962.4 eV, respectively. Through this, it was confirmed that copper (Cu) was mainly present in the form of ^{Cu 2+} impurities and Cu ₂ MoS _{4 .} In addition, the catalyst prepared in Example 1 was upshifted by 0.13 eV compared to the catalyst prepared in Comparative Example 4, indicating that a strong interaction between the core and the shell existed.

Meanwhile, FIG. 19 is a survey spectrum of XPS, in which (a) is an analysis of the catalyst prepared in Comparative Example 1, (b) is an analysis of the catalyst prepared in Comparative Example 2, (c) is a comparison The catalyst prepared in Example 3 is analyzed, (d) is an analysis of the catalyst prepared in Comparative Example 4, and (e) is an analysis of the catalyst prepared in Example 1. Through this, it was found that the catalyst prepared in Example 1 showed peaks at 779.9, 932.8, 232.2, 166.5 and 398.7 eV in Co 2p, Cu 2p, Mo 3d, S 2p, N 1s and C 1s, respectively.

Experimental Example 9: Measurement of specific surface area

In order to analyze the specific surface area of the catalysts prepared in Example 1 and Comparative Example 2, it was measured using ASAP 2020 Plus System (Micromeritics Instrument Corp., USA).

First, (p) of FIG. 3 shows the specific surface area of the catalyst prepared in Example 1, and was measured to ^{be 254.8 m 2} ·g ^{−1 .}

13 shows the specific surface area of the catalyst prepared in Comparative Example 2, ^{measured as 203.6 m 2} ·g ^-1 , the catalyst prepared in Comparative Example 2 has a smaller specific surface area compared to the catalyst prepared in Example 1 has been shown to have Through this, the catalyst prepared in Example 1 has a large contact area, so that charge transfer occurs rapidly, and as a result, it is expected to have high activity.

In addition, the inserted image of FIG. 13 shows the pore distribution of the catalyst prepared in Comparative Example 2, and the pores of the catalyst prepared in Comparative Example 2 have a mesoporous pore size with an average size of 10 to 40 nm. Could know.

Experimental Example 10: Catalyst Structure Analysis

32 (a) is an analysis of the catalyst prepared in Example 1, Cu ₂ MoS ₄ (shell), CoS _x (core) (x = 0 and x = 2) and CoS _x @Cu ₂ MoS ₄ ( Core@shell) is a schematic diagram of nanoparticles, (yellow color means sulfur atom, dark blue color means cobalt atom, red color means copper atom, and cyan color means molybdenum atom.) By measuring the structural parameters related to this it will be described Through this, it was possible to know the shape, formation energy, and interatomic distance of each component.

Experimental Example 11: Catalytic Activity Evaluation 1

The catalysts prepared in Example 1 and Comparative Examples 1 to 5 were analyzed using a CH660D workstation (CH Instruments Inc., USA), and electrodes (graphite and H/HgO) were prepared for the experiment. Specifically, 2.5 mg of solid powder of the catalyst (Examples and Comparative Examples) and 5 μl of Nafion solution (5 wt%) were dispersed in 0.5 mL of ethanol, followed by sonication for 1 hour to prepare a solution. Then, 5 μl of the solution was slowly dropped on the polished surface of the electrode of a rotating ring disk electrode (RRDE), and then dried at 25° C. for 5 hours at room temperature to evaluate oxygen reduction reaction (ORR) activity. will be.

First, (a) of FIG. 5 shows the cycle voltage of the catalyst prepared in Example 1 at a scanning rate of ^{50 mV·s −1} in a 0.1M KOH electrolyte condition saturated with _{nitrogen (N 2} )/oxygen (O _{2 ).} As a current (CV; cyclic voltammetry) curve was shown, it was found that the catalyst prepared in Example 1 showed strong activity in the oxygen reduction reaction.

On the other hand, Figure 5 (b) shows the catalyst prepared in Example 1 and Comparative Examples 1 to 5 at a ^{scan rate of 10 mV s -1} , a rotation speed of 1,600 rpm and 0.1M KOH solution conditions. The linear sweep voltammetry (LSV) curve of Compared to the catalyst prepared in Comparative Example 4, higher onset potential (E _on, onset potential) +0.97V and _{half-wave potential (E half} , half-wave potential) +0.89V were exhibited, but the catalyst prepared in Comparative Example 5 (initiation potential) +0.99V, half-wave potential +0.90V) and showed good activity in oxygen reduction reaction.

In addition, FIG. 5 (c) is a graph showing the Tafel slopes of the catalysts prepared in Example 1 and Comparative Examples 1 to 5, and the catalyst prepared in Example 1 was 53.5 mV·dec ^- The catalyst of the catalyst prepared in Comparative Example 5 with a Tafel slope of ^{1 had a Tafel slope of 48.2 mV·dec -1, and} the Tafel slope of the catalyst prepared in Example 1 and Comparative Example 5 (noble metal-based) of the present invention was It was found that it had the relatively lowest value, and the catalysts prepared in Comparative Examples 1 to 4 were 92.9mV·dec ^-1 ,72.8 mV·dec ^-1 , 69.1 mV·dec ^-1 , 62.2 mV·dec, respectively. ^It was confirmed that it has a Tafel slope of -1. Through this, since the activity of the catalyst was also high as the Tafel slope was low, it was found that the catalyst prepared in Example 1 had good activity in the oxygen reduction reaction.

On the other hand, the KL plots (Koutecky-Levich) of the catalysts prepared in Example 1 and Comparative Examples 1 to 4 in FIGS. 5 (d) and 20 (b), (d), (f), and (h) are plot), and it was found that excellent linearity and parallelism were exhibited. In addition, the number of electron transfers (n) in Example 1 is 3.97, which is the highest with the catalyst prepared in Comparative Example 5 of the noble metal type where n is about 4.0, and the catalyst prepared in Comparative Examples 1 to 4 is 2.79, It was shown in the order of 3.10, 3.61, and 3.75, and it was found to have a relatively low number of electron transfers compared to the catalyst prepared in Example 1. In general, the oxygen reduction reaction occurs via the 2e-passage when oxygen is reduced to peroxide and then reduced to water, and via the 4e-passage when oxygen is directly reduced to water. If the oxygen reduction reaction occurs through the 2e-passage, peroxide is generated, so the catalytic efficiency is generally reduced due to corrosion, but in Example 1, the number of electrons is high, so it is determined that good catalytic efficiency is maintained during the oxygen reduction reaction do.

On the other hand, Figure 21 is a rotating ring-disk electrode device (RRDE; It shows the number of electron transfers (n), and the number of electron transfers of the catalyst prepared in Example 1 of the present invention was 3.92 to 3.96, and the number of electron transfers of the catalyst prepared in Comparative Example 5, which is a noble metal, was 3.96 to 4.0, the catalyst showed the highest value, indicating good activity.

In addition, (b) of FIG. 21 shows the peroxides of the catalysts prepared in Example 1 and Comparative Examples 1 to 5 (HO ₂ ⁻ ) The content of anions is expressed as a percentage (%), and the catalyst prepared in Example 1 contains 6.8 to 8.3% of peroxide, and the peroxide of the catalyst prepared in Comparative Example 5, which is a noble metal, is 2.8 to 4.4%, and the least peroxide is generated. appeared to do At this time, the number of electron transfers (n) is calculated by the following formula.

[Relational Expression 1]

In Relation 1, I _r , I _d represent the ring current and the disk current, respectively, and N represents the collection efficiency, where N=0.42.

On the other hand, the inserted image of Figure 5 (d) and Figure 20 (a), (c), (e), (g) are the catalysts of the catalysts prepared in Example 1 and Comparative Examples 1 to 4 An experiment was performed with a rotating ring-disk electrode (RRDE) under the conditions of a scan rate of 10mV·s ^-1 and a rotation speed of 400 to 2000 rpm, and the results were obtained with a linear scanning potential (LSV; Linear). As a graph represented by a sweep voltammetry) curve, it was found that mass transfer was improved as the rotational speed increased.

On the other hand, Figure 5 (e) shows the catalyst prepared in Example 1 and Comparative Example 5 in an oxygen-saturated KOH solution of 0.1M and an operating condition of +0.80 V, using chronoamperometry for a long time. As an evaluation of stability, the current response of the catalyst of Example 1 was maintained at 99.6% after 16.4 hours of operation, but the catalyst of Comparative Example 5 had a current response of 85.1% after 13 hours of operation under similar conditions. was found to be low.

In addition, the inserted image in (e) of FIG. 5 relates to the catalyst prepared in Example 1, and shows a linear sweep voltammetry (LSV) curve after the oxygen reduction reaction, through which Example 1 is carried out for a long time. It was found that there was no decrease in activity even after.

On the other hand, (a) to (b) of Figure 22 is a scanning electron microscope (SEM) and H-7650 equipment (Hitachi Ltd., Japan) of the catalyst prepared in Example 1 after carrying out the oxygen reduction reaction. was observed with a transmission electron microscope (TEM) using

In addition, FIG. 22(c) shows the observation of the catalyst prepared in Example 1 after the oxygen reduction reaction was performed with a scanning-transmission electron microscope (STEM), and FIGS. 22(d) to ( i) is an analysis performed on the catalyst prepared in Example 1 by energy dispersive spectrometry (EDS), and elemental mapping by measuring Co, Cu, Mo, S, C and N elements after oxygen reduction reaction One result is a graph, and it can be seen that each element is reasonably distributed in all investigation ranges.

In addition, (a) to (d) of FIG. 23 is a graph obtained by analyzing the catalyst prepared in Example 1 with a high-resolution XPS spectrum, through which Example 1 is Co 2P before and after the oxygen reduction reaction , Cu 2P, Mo 3d, and S 2p, there was no significant change in the graph before and after the oxygen reduction reaction, indicating good stability during the oxygen reduction reaction.

In addition, FIG. 5 (f) is a graph showing the durability of the catalysts prepared in Examples 1 and 5 when the oxygen reduction reaction was performed by adding 1.0 M methanol (MeOH) to an oxygen-saturated KOH solution. As a result, it can be seen that the catalyst prepared in Example 1 of the present invention did not show a noticeable change in current, but the catalyst prepared in Comparative Example 5 of the noble metal system showed a noticeable change in current, indicating that the durability in methanol was lowered. there was. Through this, it was found that the catalyst prepared in Example 1 under methanol conditions had better durability than the catalyst prepared in Comparative Example 5.

Experimental Example 12: Catalyst Activity Evaluation 2

The catalysts prepared in Example 1 and Comparative Examples 1 to 5 were analyzed using a CH660D workstation (CH Instruments Inc., USA), and electrodes (graphite and H/HgO) were prepared for the experiment. Specifically, 2.5 mg of the solid powder of the catalyst prepared in Example 1 and Comparative Example 1 to Comparative Example 5 and 5 μl of Nafion solution (5 wt %) were dispersed in 0.5 mL of ethanol, and sonicated for 1 hour. to prepare a solution. Then, 5 μl of the solution was slowly dropped on the polished surface of the electrode of a rotating ring disk electrode (RRDE), and then dried at room temperature for 5 hours at 25° C. Activity was evaluated in the following manner at a scan rate of 10 mV·s ^{-1 and 0.1M KOH electrolyte conditions.}

First, (a) of FIG. 6 shows the linear sweep voltammetry (LSV) curves of the catalysts prepared in Example 1 and Comparative Examples 1 to 5 Catalysts Example 1 and Comparative Examples 1 to 5. That is, ^{the catalyst prepared in Example 1 under the conditions of 0.1M KOH and a scan rate of 10mV·s −1} requires an overvoltage of 118.1mV, and the catalysts of Comparative Examples 1 to 4 were 321mV, 282.7mV, and 282.7mV, respectively. It was found that 238.1 mV and 182.5 mV of overvoltage were required, and Comparative Example 5 was found to require an overvoltage of 63.1 mV, and Example 1 and Comparative Example 5 required the lowest overvoltage, which is good in the hydrogen generation reaction. activity was found.

In addition, Figure 6 (b) is a graph showing the Tafel slopes of the catalysts prepared in Example 1 and Comparative Examples 1 to 5 in Example 1 and Comparative Example 1, the catalyst of Example 1 shows a Tafel slope ^{of 41.1 mV·dec -1} The catalyst of Comparative Example 5, which is a noble metal, had ^{a Tafel slope of 35.1 mV·dec -1} and had the lowest value, and the Tafel slopes of the catalysts of Comparative Examples 1 to 4 were 89.7, 73.6, 67.5 and 58.6 mV·dec ^{- 1} , indicating a relatively high value. Through this, as Example 1 and Comparative Example 5 had the lowest Tafel slope, it was found that it had the best activity in the hydrogen evolution reaction.

Meanwhile, in FIG. 6(c), in order to evaluate the stability of the catalysts prepared in Example 1 and Comparative Example 5 when operated for a long time by chronoamperometry, a current density of ^{10mA·cm -2 for 33 hours} wanted to keep. Both Example 1 and Comparative Example 5, which are noble metals, were well maintained, but as the catalyst of the catalyst prepared in Example 1 was a little more linear on the graph, it was shown to have good stability compared to the catalyst prepared in Comparative Example 5. In addition, the current loss after 33 hours of operation was found that the catalyst prepared in Example 1 of the present invention showed better performance than the catalyst prepared in Comparative Example 5 having a current loss of 15% and 30%.

In addition, the inserted image of FIG. 6 (c) is a graph showing a linear sweep voltammetry (LSV) curve before and after the operation of the catalyst prepared in Example 1 for 33 hours. was found to be durable.

In addition, FIG. 25 shows that the catalysts prepared in Example 1 and Comparative Example 5 were analyzed by a multi-potentiometry method, respectively, and the current density was increased ^{from 10 mA cm -2} to 90 mA cm ^-2. Accordingly (ie, as the overvoltage increased), the current response immediately increased and appeared as a step-wise graph, and the catalyst prepared in Example 1 showed excellent activity in the hydrogen evolution reaction.

In addition, (a) to (d) of FIG. 26 are graphs in which the hydrogen evolution reaction of the catalyst prepared in Example 1 before and after the hydrogen evolution reaction was analyzed with high-resolution XPS spectra, in that order Co 2P, Cu 2P , Mo 3d and S 2p were shown, and through this, there was no significant change before and after the hydrogen evolution reaction, indicating that the catalyst of Example 1 had good stability in the hydrogen evolution reaction.

In addition, Figure 24 is a graph by measuring the overvoltage in the hydrogen reduction reaction, in which Figure 1 is for the catalyst prepared in Comparative Example 1, 2 is for the catalyst prepared in Comparative Example 2, and 3 is For the catalyst prepared in Comparative Example 3, 4 is for the catalyst prepared in Comparative Example 4, 5 is for the catalyst prepared in Example 1, 6 is for the catalyst prepared in Comparative Example 5 Through this, it was found that the catalyst prepared in Example 1 had an overvoltage in the hydrogen reduction reaction as low as that of the catalyst prepared in Comparative Example 5, which is a noble metal-based catalyst.

Experimental Example 13: Catalyst Activity Evaluation 3

Analysis was performed using a CH660D workstation (CH Instruments Inc., USA) apparatus, and electrodes (graphite and H/HgO) were prepared for the experiment. Specifically, 2.5 mg of the solid powder of the catalyst prepared in Example 1 and Comparative Examples 1 to 6 and 5 μl of Nafion solution (5 wt %) were dispersed in 0.5 mL of ethanol and sonicated for 1 hour. to prepare a solution. Then, 5 μl of the solution was slowly dropped on the polished surface of the electrode of a rotating ring disk electrode (RRDE), and then dried at 25° C. for 5 hours at room temperature to determine the oxygen evolution reaction (OER) activity of the catalyst. It was evaluated as follows under the conditions of a scan rate of 10mV·s ^{-1 and a 0.1M KOH solution.}

First, (d) of Figure 6 in Example 1 and Comparative Examples 1 to, when a catalyst prepared in Comparative Example 6 to the oxygen generating reaction in the scan speed condition of 0.1M KOH electrolyte and 10mV · s ^-1, a linear scanning potential ( Linear sweep voltammetry (LSV) curve graph is shown, and the slope was large in the order of the catalysts prepared in Example 1, Comparative Example 4, Comparative Example 3, Comparative Example 5, Comparative Example 1 and Comparative Example 6. It was found that the catalyst prepared in Example 1 had the best activity in the oxygen evolution reaction.

In addition, (e) of Figure 6 is the Tafel slope (Tafel slopes) when the catalyst prepared in Example 1 and Comparative Examples 1 to 5 reacted with oxygen generation, the Tafel slope of Example 1 is 61.5 mV·dec ^-1 was the lowest, Comparative Example 4 92.9mV·dec ^-1 , Comparative Example 3 101.9mV·dec ^-1 , Comparative Example 5 106.4mV·dec ^-1 , Comparative Example 2 163.5mV·dec ^-1 , Comparative Example 1 124.7mV·dec ^-1 increased in the order. Through this, it was found that the catalyst prepared in Example 1 had better activity than the catalyst prepared in Comparative Example 5, which is a noble metal-based catalyst, in the oxygen evolution reaction.

Meanwhile, in FIG. 6(f), in order to evaluate the stability of the catalysts prepared in Example 1 and Comparative Example 6 during long-term operation by chronoamperometry, a current density of ^{10mA·cm -2 was maintained for 33 hours.} wanted to Through this, the catalyst prepared in Example 1 maintained the current density well, but the catalyst prepared in Comparative Example 6, which is a noble metal, did not maintain relatively well compared to Example 1. Specifically, after 33 hours of operation, the retention rate (retention rate) of Example 1 of the present invention was 93.1%, which was found to show better performance than Comparative Example 6 showing a retention rate of 65.1%.

In addition, FIG. 6(f) is a graph showing a linear sweep voltammetry (LSV) curve before and after operation for 33 hours with respect to the catalyst prepared in Example 1, showing excellent durability without change in current density for a long time. I knew I had

On the other hand, FIG. 28 is a graph showing the results obtained by analyzing the catalysts prepared in Example 1 and Comparative Example 6 by multi-potentiometry, and the current density was changed ^{from 5mA·cm -2} to 45mA·cm ^-2 As it increased (ie, as the overvoltage increased), the current response immediately increased and appeared as a step-by-step graph, confirming that it had excellent activity.

On the other hand, FIG. 29 is an analysis equipment of the catalyst prepared in Example 1, using Supra 40 VP equipment (Zeiss. Co., Germany) to analyze the catalyst by EDAX (Energy Dispersive Analysis of X-rays), and FIG. The inserted image of 29 shows the percentage (%) of each element ratio before and after the oxygen evolution reaction, and as an analysis result, cobalt (Co), copper (Cu), molybdenum (Mo), carbon (C) before and after the oxygen evolution reaction ), sulfur (S), oxygen (O) and nitrogen (N) elements were shown, and no significant change was observed except for oxygen and sulfur elements. In addition, it was found that the reduction in the content of elements of oxygen and sulfur is to perform an oxidation process on the surface during the oxygen evolution reaction.

In addition, (a) ~ (d) of Figure 30 is a high-resolution (high-resolution) XPS (X-ray Photoelectron Spectroscopy) of the catalyst prepared in Example 1 using Theta probe equipment (Thermo Fisher Scinetific Inc., USA) analysis was performed. It is a graph showing the peaks in Co 2P, Cu 2P, Mo 3d and S 2p before and after the oxygen evolution reaction of the catalyst prepared in Example 1. Looking at this, the Co 2p binding energy after the oxygen evolution reaction showed that ^{the disappearance of Co 0} and the visible Co ³⁺ occupies a large proportion compared to before the oxygen evolution reaction, and the Cu 2p binding energy is the core-shell (CoS _x -Cu ₂ MoS ₄ ^{) An increase in Cu 2+ on} the surface of the nanoparticles was confirmed, and through this, it was confirmed that the core was a core-shell catalyst in which the shell was wrapped around the surface of the core.

In addition, the Mo 3d binding energy after the oxygen evolution reaction showed that the binding energy of metal (M)-sulfur (S) (observed as 226.2 eV before the reaction) was significantly reduced compared to before the oxygen evolution reaction, and oxygen The S 2p binding energy after the generation reaction showed a definite decrease compared to before the oxygen generation reaction, and through this, it was confirmed that the oxidation of the nanoparticles was made and a metal-sulfur bond (the core of the nanoparticles) was formed, and the core part of these nanoparticles It was found to accelerate the oxygen evolution reaction.

On the other hand, (j) ~ (o) of FIG. 7 shows that the catalyst prepared in Example 1 after the oxygen evolution reaction was analyzed using energy dispersive spectrometry (EDS) to perform color mapping, and each cobalt Corresponds to (Co), copper (Cu), molybdenum (Mo), sulfur (S), nitrogen (N) and carbon (C). Through this, it was found that Example 1 well maintained the shape of the catalyst even after the oxygen evolution reaction.

On the other hand, FIG. 27 is a graph showing the results of measuring the overvoltage during the oxygen evolution reaction under ^{0.1M KOH aqueous solution and scanning rate conditions of 10 and 50 mV sec -1} the catalyst prepared in Comparative Example 2, 2 is the catalyst prepared in Comparative Example 2, 3 is the catalyst prepared in Comparative Example 3, 4 is the catalyst prepared in Comparative Example 4, and 5 is Example 1 For the catalyst prepared in , 6 is for the catalyst prepared in Comparative Example 5. Through this, it was found that Example 1 of the present invention has a lower overvoltage than Comparative Example 5, which is a noble metal-based catalyst, in the oxygen evolution reaction, and thus is a better catalyst.

On the other hand, Figure 31 shows the X-ray diffraction patterns (XRD) of the catalyst prepared in Example 1 before and after the oxygen evolution reaction using D/Max 2500 V/PC (Rigaku Co., Japan) equipment. As a result of the analysis, it was found that Example 1 maintained well without losing activity even after the oxygen evolution reaction.

Experimental Example 14: Evaluation of Catalytic Activity 4

To evaluate the activity of the catalyst, analysis was performed using a CH660D workstation (CH Instruments Inc., USA), and electrodes (graphite and H/HgO) were prepared for the experiment. Specifically, 2.5 mg of the solid powder of the catalyst prepared in Example 1 and Comparative Examples 1 to 4 and 5 μl of Nafion solution (5% by weight) were dispersed in 0.5 mL of ethanol, followed by sonication for 1 hour. was prepared. Then, 5 μl of the solution was slowly dropped on the polished surface of the electrode of a rotating ring disk electrode (RRDE), and then dried at 25° C. for 5 hours at room temperature, and evaluated as follows. First, (b) to (c) of FIG. 32 are graphs obtained by calculating the density of states (DOS) of Example 1, in which the core-shell structure has only the core part (CoS _x ) and the shell part It was found to have a higher energy level than that with only (Cu ₂ MoS _{4 ).}

On the other hand, (g) of FIG. 6 is a graph in which electrochemical impedance spectroscopy (EIS) is measured in a frequency range ^{of 10 5} to 10 ^{-2 and an applied potential of +0.8V.} 1) to (5) correspond to the catalysts prepared in Example 1, Comparative Example 3, Comparative Example 4, Comparative Example 2, and Comparative Example 1, respectively. Specifically, Example 1 had the lowest charge transfer resistance of 66.6 Ω, showing that it had the best conductivity, and Comparative Examples 1 to 4 had relatively high charges of 80.9 Ω, 75.7 Ω, 74.2 Ω, and 70.4 Ω, respectively. It had a movement resistance value.

In addition, (h) to (i) of FIG. 6 and (a) to (d) of FIG. 33 are electrochemically active areas (ECSA) of the catalysts prepared in Example 1 and Comparative Examples 1 to 4 To evaluate the surface area), a cyclic voltammetry (CV) curve and double layer capacitance (C _dl ) were measured in a _{0.1M KOH electrolyte saturated with nitrogen (N 2} )/oxygen (O _{2 ).} will be.

Specifically, FIG. 6(h) shows a cyclic voltammetry (CV) curve in the range of 0.92 to 1.02V depending on the scanning speed of the catalyst prepared in Example 1 (5 to 30mV·s ^{-1 ).} It can be seen that, through this, it has stability even when the injection speed is changed.

In addition, (a) to (d) of FIG. 33 shows cyclic voltammetry (CV) curves of the catalysts prepared in Comparative Example 4, Comparative Example 3, Comparative Example 2, and Comparative Example 1, through which the nano It is predicted that the structure of the sheet and graphene sheet accelerates the absorption of protons and electrons and rapidly desorbs hydrogen.

In addition, (i) of FIG. 6 is a graph showing the measurement of the double layer capacitance _{(C dl , double layer capacitance).} As a result, the catalyst prepared in Example 1 had a C _dl ^{value of 16.92 mF·cm -2} and showed the largest double layer capacity, and the catalysts prepared in Comparative Examples 1 to 4 were 1.26, 2.51, 10.59, respectively. 11.95 mF·cm ^{-2 It has} a C _dl value of -2 It can be seen that it has a lower double-layer capacity value compared to Example 1.

In addition, in (a) of FIG. 8, when the catalyst prepared in Example 1 was a KOH electrolyte of 0.1M and ^{a scanning rate of 10mV·s −1} , a linear sweep potential (LSV; Linear sweep) in the range of 0.3 to 1.9V voltammetry) curve was shown. It was found that the potential difference between the oxygen evolution reaction and the oxygen reduction reaction was as low as 0.694 V, making it suitable for use as a zinc-air battery. In this case, the potential difference (ΔE) may be calculated as _{ΔE=E J} -E _{half , where E J} is a potential value for achieving a current response of 10 mA·cm ^{-2 in} _{the oxygen evolution reaction, and E half} is oxygen reduction It means the half-wave potential in the reaction.

Experimental Example 15: Evaluation of Catalytic Activity 5

In order to evaluate the activity of the catalyst according to the conditions of the first heat treatment, the second heat treatment and the sulfur precursor, analysis was performed using a CH660D workstation (CH Instruments Inc., USA) device, and for the experiment, electrodes (graphite and H/ HgO) was prepared. Specifically, 2.5 mg of the solid powder of the catalysts of Examples 1 to 9 and Comparative Examples 7 to 14 and 5 μl of Nafion solution (5 wt %) were dispersed in 0.5 mL of ethanol, and for 1 hour The solution was prepared by sonication. Then, 5 μl of the solution was slowly dropped on the polished surface of the electrode of the rotating ring disk electrode (RRDE), dried at 25° C. for 5 hours at room temperature, and evaluated in the following manner, and the results are shown in Table 4 below ~ shown in Table 6.

(1) Tafel slope measurement

The Tafel slope was calculated via the logarithmic slope of the current density to the overvoltage.

(2) The double layer capacitance (C _dl , double layer capacitance value) was calculated.

(3) Measurement of charge transfer resistance

Electrochemical impedance spectroscopy (EIS) was measured in a frequency range of 10 ⁵ to 10 ^{-2 and an applied potential of +0.8V.}

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Sulfur precursor (mg)
(NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 5 thiourea 480 480 480 480 480 480 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1: 96 1: 96 1: 96 1: 96 1: 96 primary heat treatment Temperature (℃) 500 450 550 500 500 500 gas ratio
(Ar:H ₂ ) 1:0.43 1:0.43 1:0.43 1:0.43 1:0.43 1:0.25 Secondary heat treatment temperature (℃) 900 900 900 850 950 900 Tafel slope (mV·dec ^-1 ) 53.5 59.4 55.1 58.6 54.7 60.4 Double layer capacity (C _dl , mF cm ^-2 ) 16.92 12.68 14.52 13.15 15.63 12.29 Charge transfer resistance (Ω) 66.6 68.2 67.7 67.6 67.5 69.4

Example 7 Example 8 Example 9 Comparative Example 7 Comparative Example 8 Comparative Example 9 Sulfur precursor (mg) (NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 5 thiourea 480 400 550 480 480 480 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1:80 1:110 1: 96 1: 96 1: 96 primary heat treatment Temperature (℃) 500 500 500 420 580 500 gas ratio
(Ar:H ₂ ) 1:0.67 1:0.43 1:0.43 1:0.43 1:0.43 1:0.43 Secondary heat treatment temperature (℃) 900 900 900 900 900 820 Tafel slope (mV·dec ^-1 ) 56.1 57.8 54.6 91.5 71.3 88.4 Double layer capacity (C _dl , mF cm ^-2 ) 16.23 13.92 15.33 1.51 9.58 3.45 Charge transfer resistance (Ω) 66.8 67.1 66.6 80.6 74.8 76.9

Comparative Example 10 Comparative Example 11 Comparative Example 12 Comparative Example 13 Comparative Example 14 Sulfur precursor (mg) (NH ₄ ) ₂ MoS ₄ 5 5 5 5 5 thiourea 480 480 480 300 650 Weight ratio ((NH ₄ ) ₂ MoS ₄ : thiourea) 1: 96 1: 96 1: 96 1:60 1:130 primary heat treatment Temperature (℃) 500 500 500 500 500 gas ratio
(Ar:H ₂ ) 1:0.43 1:0.11 1:1.00 1:0.43 1:0.43 Secondary heat treatment temperature (℃) 980 900 900 900 900 Tafel slope (mV·dec ^-1 ) 75.1 90.2 78.8 68.6 70.3 Double layer capacity (C _dl , mF cm ^-2 ) 9.64 1.77 8.51 10.91 9.57 Charge transfer resistance (Ω) 75.1 80.2 78.4 72.5. 79.3

Referring to Tables 4 to 6, it was found that the catalyst prepared in Example 1 had the lowest Tafel slope and charge transfer resistance, and had the highest double layer capacity and thus was the most efficient catalyst. In addition, Examples 2 to 9 showed slightly lowered physical properties compared to Example 1, but showed good properties and were found to be suitable catalysts for application to batteries and water decomposition devices.

On the other hand, the catalysts prepared in Comparative Examples 7 to 14 showed significantly lower physical properties. Specifically, Comparative Example 7 was performed at a first heat treatment temperature of less than 450 ° C., Example 2 (first heat treatment temperature) 450°C), the Tafel slope and charge transfer resistance values were significantly higher, and the double layer capacity was significantly smaller. This is considered to be because the temperature of the primary heat treatment was too low and the metal sulfide nanosheets were not properly formed on the surface of the graphene sheet.

In addition, Comparative Example 9 was carried out at a secondary heat treatment temperature of less than 850 ° C., compared with Example 4 (second heat treatment temperature of 850 ° C.), the Tafel slope and charge transfer resistance value were significantly higher, and the double layer capacity was significantly small. appear. This is predicted because the shell of metal sulfide and the nanosheet of metal sulfide were well formed, but as the secondary heat treatment temperature was excessively low, the core of the nanoparticles was not properly formed.

In addition, Comparative Examples 8 and 10 were carried out by varying the first heat treatment temperature (over 550° C.) and the second heat treatment temperature (over 850° C.), respectively, and Example 3 (first heat treatment temperature of 550° C.) and Examples 5 (secondary heat treatment temperature of 950 °C), the Tafel slope and charge transfer resistance values were significantly higher, and the double layer capacity was significantly smaller. Through this, when the heat treatment temperature was performed higher than the range, it was confirmed that the physical properties were rather deteriorated.

In Comparative Examples 11 and 12, the gas ratios of argon and hydrogen in the primary heat treatment were respectively 1:0.11 and 1:1.00, respectively, in Example 6 (gas ratio 1:0.25) and Example 7 (gas ratio) 1:0.67), the Tafel slope and charge transfer resistance values were significantly higher, and the double layer capacity was significantly smaller. Specifically, when the gas ratio is 1:0.11, it is determined that the hydrogen gas and the sulfur precursor react to not sufficiently form the metal sulfide nanosheets, resulting in deterioration of physical properties, and when the gas ratio is 1: 1.00, hydrogen gas It is judged that the reaction is inhibited as the amount is excessive and the physical properties are deteriorated.

In Comparative Example 13, the weight ratio of the sulfur precursor was less than 1:80, and compared with Example 8 (the sulfur precursor weight ratio 1:80), the Tafel slope and charge transfer resistance value were significantly higher, and the double layer capacity was significantly higher. appeared to be small. This is considered to be due to insufficient formation of the core-shell nanoparticles due to insufficient formation of the composite.

In addition, Comparative Example 14 was carried out in a weight ratio of the sulfur precursor exceeding 1: 130, and compared with Example 9 (sulfur precursor weight ratio 1: 110), the Tafel slope and charge transfer resistance value were significantly higher, and the double layer capacity was significantly higher. appeared to be small. This is judged to be a result of the unreacted substances remaining after the reaction act as impurities as the weight ratio of the sulfur precursor is excessively high.

Preparation Example 1: Preparation of water decomposition device

A water decomposition device was prepared by applying the hybrid catalyst prepared in Example 1 to an electrolyzer under alkaline conditions composed of an anode and a cathode, and the water decomposition device prepared in Preparation Example 1 was shown in FIGS. 7 (b) and 34 (a). ) is shown in

Comparative Preparation Example 1: Preparation of water decomposition device

A water decomposition device was prepared under the same conditions as in Preparation Example 1, but the catalyst prepared in Comparative Example 5 was applied to the negative electrode and the catalyst prepared in Comparative Example 6 was applied to the positive electrode to perform Comparative Preparation Example 1.

Experimental Example 16: Water decomposition device performance comparison

The water decomposition apparatus prepared in Preparation Example 1 and Comparative Preparation Example 1 was analyzed using a CH660D workstation (CH Instruments Inc., USA) apparatus, and the performance of the water decomposition apparatus was evaluated as follows. First, (a) and (d) to (e) of Figure 7 is a comparison of the performance of the water decomposition device prepared in Preparation Example 1 and Comparative Preparation Example 1. _{CoS x} @Cu ₂ MoS ₄ -MoS ₂ /NSG in the figure refers to Preparation Example 1 prepared in Example 1, and Pt/c+RuO ₂ /C is Comparative Preparation prepared in Comparative Examples 5 and 6 I mean example 1.

Analysis was performed using a CH660D workstation (CH Instruments Inc., USA) apparatus, and the performance of the water decomposition apparatus was evaluated as follows. First, (a) and (d) to (e) of Figure 7 is a comparison of the performance of the water decomposition device prepared in Preparation Example 1 and Comparative Preparation Example 1. _{CoS x} @Cu ₂ MoS ₄ -MoS ₂ /NSG in the figure refers to Preparation Example 1 prepared in Example 1, and Pt/c+RuO ₂ /C is Comparative Preparation prepared in Comparative Examples 5 and 6 I mean example 1.

As a result, Preparation Example 1 requires ^{a cell voltage of 1.60V to achieve 10mA·cm -2} , whereas Comparative Preparation Example 1 requires 1.63V, so that the performance of Preparation Example 1 is relatively was found to be excellent. In addition, in (b) of Figure 7, it was confirmed that the water decomposition device of Preparation Example 1 produces hydrogen (H ₂ ) and oxygen (O ₂ ) gases well at the anode and the cathode, respectively.

In addition, (d) of FIG. 7 confirms the durability of the water decomposition device of Preparation Example 1 and Comparative Preparation Example 1 when trying to maintain a current density of ^{10mA·cm -2 in 0.1 M KOH.}

As a result, the water decomposing device of Comparative Preparation Example 1 ^{had a sharp decrease in current density from 10mA·cm -2} to 6mA·cm ^-2 after 25 hours of operation, whereas the water decomposing device of Preparation Example 1 was 9.3 even after 25 hours of operation. was maintained at a current density in mA · cm ^-2, was confirmed by having a better durability to maintain a current density of 7.5mA · cm ^-2, even after working 68 hours.

In addition, Fig. 7 (e) is a linear sweep voltammetry (LSV) curve of Preparation Example 1, it was found that the water decomposition device of Preparation Example 1 maintains good activity even after 25 hours of operation.

Experimental Example 17: Water decomposition device performance evaluation

The performance of the water cracking device was evaluated as follows. First, gas was collected at a current density of ^{100 mA cm -2} through the catalyst prepared in Preparation Example 1 as shown in FIG. Calculated.

[Relational Expression 2]

In Relation 2, η _F means Faraday efficiency, V _Theo is the theoretical value of the emission volume, and V _Meas means the actual emission volume.

[Relational Expression 3]

In the above relation 3, V _Theo is the theoretical value of the emission volume, I means the current density (mA·cm ^-2 ), R is a constant, R=0.082, T is the operating temperature (K), t is the operating time (s), P is the operating pressure (atm), z is the number of charges used to generate 1 mole of hydrogen or 1 mole of oxygen, and F is the Faraday constant, where F = 96,485C.

In addition, (b) of FIG. 34 is a _{graph showing the actual and theoretical obtained values of hydrogen (H 2} ) and oxygen (O ₂ ) gases, respectively, Calculated in the figure means the theoretical obtained value, Measured is It means the actual value obtained.

As a result, the Faradaic efficiency (ηF) calculated as the ratio of the actual obtained value and the theoretical obtained value was 99.31%, and the actual amount of captured gas was similar to the theoretical value. It has been shown to have excellent activity when used in the device.

Preparation Example 2: Preparation of a zinc-air (Zn-air) battery

^{A zinc-air battery was prepared by using 1.6 mg·cm -2} of the catalyst prepared in Example 1 as an anode catalyst, and is shown in FIG. 8(b).

Comparative Preparation Example 2: Preparation of a zinc-air (Zn-air) battery

It was prepared under the same conditions as in Preparation Example 2, but Comparative Preparation Example 2 was carried out using the catalyst (Pt/C) prepared in Comparative Example 5 as a catalyst.

Experimental Example 18: Zinc-air (Zn-air) battery performance evaluation

The zinc-air (Zn-air) batteries prepared in Preparation Example 2 and Comparative Preparation Example 2 were evaluated as follows.

First, in (c) to (d) of Figure 8, the circuit voltage of Preparation Example 2 was measured, the single cell of Preparation Example 2 had an open circuit voltage of ~1.44V, and the two series circuit open circuit voltages were ~2.88V. appear. In addition, (e) of FIG. 8 is a graph showing the open circuit potential (OCP) measurement results of Preparation Example 2 and Comparative Preparation Example 2, and Preparation Example 2 of the present invention shows that the open circuit voltage is approximately 1.4V. and showed a slightly higher cell voltage than Comparative Preparation Example 2 (using a platinum-based catalyst).

On the other hand, (f) of FIG. 8 is a measurement of the polarization and the resulting power density of Preparation Example 2 and Comparative Preparation Example 2. As a result, preparation 2 has a maximum power density of 40mW · cm ^-2 at a current density of 58mA · cm ^-2, Comparative Production Example 2 is brought up to a power density 32mW · cm ^-2 at a current density of 50mA · cm ^-2 , it was found that Preparation Example 2 was a battery having better performance.

In addition, (h) of FIG. 8 shows the discharge polarization curves at a constant current of Preparation Example 2 and Comparative Preparation Example 2, and when operated for a long time at 5.5 hours, Comparative Preparation Example 2 showed a somewhat lower voltage with time. It could be seen that, through this, the zinc-air battery of Preparation Example 2 was more stable. In addition, the inserted image shows that the zinc-air battery of Preparation Example 2 is connected in series to supply power to a red-light-emitting diode (LED), and it can be seen that it continues without a change in brightness for 5.5 hours. .

On the other hand, (i) of FIG. 8 is a photograph of an experiment result in which two zinc-air batteries of Preparation Example 2 are connected in series to supply power to a water decomposition device, and a lot of gas bubbles of hydrogen and oxygen are generated on the electrode surface. Thus, it was found that strong power could be produced by connecting Preparation Example 2 in series.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (9)

surface-modified graphene sheet; and
a nanosheet including a metal sulfide represented by the following Chemical Formula 1 formed on at least a portion of the graphene sheet; and
a graphene hybrid catalyst for water decomposition and zinc-air batteries, characterized in that it comprises core-shell nanoparticles formed on the nanosheets;
[Formula 1]
BS ₂
In Formula 1, B is molybdenum (Mo), chromium (Cr), or tungsten (W).
The graphene hybrid catalyst for water decomposition and zinc-air batteries according to claim 1, wherein the surface-modified graphene sheet is doped with nitrogen (N) and sulfur (S) on the surface of the graphene sheet. .
According to claim 1, wherein the core-shell nanoparticles
A core comprising a metal compound represented by the following formula (2); and
A graphene hybrid catalyst for water decomposition and zinc-air batteries, characterized in that it consists of; a shell including a metal sulfide represented by the following Chemical Formula 3;
[Formula 2]
AS _x
In Formula 2, A is cobalt (Co), rhodium (Rh) or iridium (Ir), and x is 0 to 4,
[Formula 3]
C ₂ BS ₄
In Formula 3, B is molybdenum (Mo), chromium (Cr), or tungsten (W), and C is copper (Cu), gold (Au), or silver (Ag).
The graphene hybrid catalyst for water cracking and zinc-air batteries according to any one of claims 1 to 3, wherein the hybrid catalyst is used in a water cracking device or a secondary battery.
1 step of preparing a mixed solution of graphene oxide and water;
2 to add a metal ion precursor to the mixed solution and sonicate
step;
Step 3 of adding and stirring the sulfur precursor to the solution in which Step 2 was performed;
Step 4 to obtain a solid powder by drying the solution stirred in Step 3;
Step 5 of performing a first heat treatment and a second heat treatment on the solid powder; and
Step 6 to obtain a hybrid catalyst by cooling the solid powder subjected to the heat treatment of 5 steps to room temperature;
A method for producing a graphene hybrid catalyst for water decomposition and zinc-air batteries in which a sulfur precursor and hydrogen gas react through the first heat treatment process to form a nanosheet including a metal sulfide represented by the following Chemical Formula 1.
[Formula 1]
BS ₂
In Formula 1, B is molybdenum (Mo), chromium (Cr), or tungsten (W).
The method of claim 5, wherein the ultrasonic treatment in step 2 is performed for 60 to 100 minutes,
The drying of the 4 steps is water decomposition and zinc-air graphene hybrid catalyst manufacturing method for a battery comprising being carried out for 12 to 15 hours at a temperature of 60 ~ 100 ℃.
According to claim 5, wherein the sulfur precursor is ammonium tetrathiomolybdate (ammonium tetrathiomolybdate), thiourea (thiourea), tetrathiomolybdate (Tetrathiomolybdate) and thioacetamide (Thioacetamide) water containing two or more selected from Method for decomposition and preparation of graphene hybrid catalyst for zinc-air cell.
The water decomposition and zinc-air battery according to claim 7, wherein the sulfur precursor contains ammonium tetrathiomolybdate and thiourea in a weight ratio of 1:80 to 1:110 by weight. A method for preparing a graphene hybrid catalyst.
The method of claim 5, wherein the primary heat treatment is in a gas containing argon (Ar) and hydrogen (H2) in a volume ratio of 1: 1.5 to 1: 4.0, 450 to 550 at a heating rate of ^{1-3 °C min -1} After heating to ℃, it is carried out at 450 ~ 550 ℃ for 60 ~ 100 minutes,
The secondary heat treatment is water decomposition and zinc, characterized in that, after heating to 850 ~ 950 ℃ at a heating rate of ^{4 ~ 6 ℃ min -1} under an inert gas, and then at 850 ~ 950 ℃ for 3 ~ 5 hours - A method for preparing a graphene hybrid catalyst for an air battery.

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