KR102257600B1 - Composite containing B-doped carbon quantum dot and preparation method thereof - Google Patents

Abstract

The present invention relates to a composite including boron-doped carbon quantum dots and a method for manufacturing the same, wherein the composite is manufactured through a hydrothermal reaction of a mixture containing glucose, boronic acid, and graphene oxide, so that the process is simple and environmentally friendly. have. In addition, the prepared composite has high porosity and specific surface area, has excellent electrical properties due to abundant active sites, and has excellent electrolyte material transfer and ion diffusion ability because of its high stability even in alkaline conditions, so oxygen reduction reaction (ORR), oxygen production reaction It can be usefully used as a catalyst used for (OER) and/or hydrogen production reaction (HER).

Description

Composite containing B-doped carbon quantum dot and preparation method thereof

The present invention relates to a composite including boron-doped carbon quantum dots and a method of manufacturing the same.

In recent years, the demand for the development of new and sustainable energy conversion and energy storage devices has increased to solve the energy crisis and environmental pollution, and accordingly, fuel cells, rechargeable metal air cells and water distribution to realize clean energy technology. Many energy systems such as devices have been developed. The basic operation of these systems mainly depends on three main electrochemical reactions: oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and ORR and OER are considered to be the two main electrochemical reactions. have. OER and HER are two important electrochemical reactions in the water separation process, or the slow reaction rate and high overvoltage, which limits the overall efficiency of the energy device. Accordingly, efforts have been made to solve this problem by using noble metal and transition metal catalysts, including platinum (Pt) for ORR and HER, and iridium (Ir) and ruthenium (Ru) for OER. However, the scarcity and high cost of noble metal-based catalysts hinder the widespread technical use and large-scale application of these electrochemical energy technologies. Therefore, as an inexpensive alternative to noble metal catalysts such as transition metal and carbon nanomaterial-based catalysts, research has been extensively conducted to develop efficient catalysts containing earth-rich materials.

Meanwhile, recently, carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene, and their composites, have been studied as efficient non-metallic electrocatalysts due to their stable activity and unique properties. In particular, carbon nanomaterials doped with nitrogen (N), phosphorus (P), sulfur (S) and boron (B) atoms and their composites generate a large number of active sites in the carbon skeleton and lower the reaction barrier, making it an efficient multifunctional electrocatalyst. The potential as has been proven. In particular, among the various heteroatoms, the nitrogen (N) and boron (B) atoms have attracted a lot of attention due to the atomic radius similar to that of carbon. For example, N-doped carbon nanomaterials have been widely used as non-metallic electrocatalysts for ORRs and OERs.

However, N-doped carbon nanomaterials that induce n-type transport properties exhibit very sensitive electronic properties to the atmosphere, and their electrocatalytic mechanisms are still unknown. In addition, B-doped carbon nanomaterials have insufficient research results than N-doped carbon nanomaterials due to difficulty in synthesis and low doping concentration.

Therefore, there is a need to develop a catalyst that is economical due to abundant resources, easy synthesis, and excellent catalytic activity, which can be applied to both oxygen reduction reactions (ORR), oxygen generation reactions (OER), and hydrogen generation reactions (HER).

Republic of Korea Patent Publication No. 10-2014-0012016 Republic of Korea Patent Publication No. 10-2016-0122009

The object of the present invention is economical, easy synthesis, and excellent catalytic activity due to abundant resources, and is eco-friendly and applicable as a catalyst for oxygen reduction reaction (ORR), oxygen generation reaction (OER) and/or hydrogen generation reaction (HER). It is to provide an efficient multifunctional catalyst and a method for producing the same.

In order to solve the above problem,

The present invention in one embodiment,

Graphene hydrogel; And

It provides a composite including carbon quantum dots dispersed on the inside and the surface of the graphene hydrogel and doped with boron.

In addition, the present invention in one embodiment,

Forming a reaction intermediate by performing a hydrothermal reaction of a mixture containing glucose, boronic acid, and graphene oxide; And

Performing a reduction reaction of the formed reaction intermediate to prepare a composite including a graphene hydrogel in which boron-doped carbon quantum dots are dispersed on a surface;

It provides a method of manufacturing the composite comprising a.

Furthermore, the present invention in one embodiment,

It provides a catalyst comprising the complex.

Since the composite according to the present invention is prepared through a hydrothermal reaction of a mixture containing glucose, boronic acid and graphene oxide, the process is simple and environmentally friendly. In addition, the prepared composite has high porosity and specific surface area, has excellent electrical properties due to abundant active sites, and is excellent in stability even under alkaline conditions, so it has high electrolyte material transfer and ion diffusion ability, so oxygen reduction reaction (ORR), oxygen generation It can be usefully used as a multifunctional catalyst for metal-air cells, fuel cells, water decomposition devices, etc. used in reaction (OER) and/or hydrogen generation reaction (HER).

1 is a flow chart showing the manufacturing process of the composite according to the present invention.
Fig. 2 is an image of an example complex analyzed by a scanning electron microscope (SEM).
3 is an image obtained by analyzing the composite (GH-BGQD) of the example with a transmission electron microscope (TEM).
4 is an image of an example composite (GH-BGQD) analyzed by a high-resolution transmission electron microscope (HR-TEM).
5 is a graph showing the results of measuring the BET specific surface area for the composites of Comparative Examples 2 and 4 and Example 2. FIG.
6 is a graph showing the results of Raman spectroscopy analysis of the complex of Example 2 (GH-BGQD) and the complex of Comparative Example 2 (GH-GQD).
7 is a graph showing X-ray photoelectron spectroscopy (XPS) for the composites prepared in Examples 1 to 3 and Comparative Example 3.
8 is a graph showing an enlarged spectrum showing C1s and B1s binding energies in X-ray photoelectron spectroscopy (XPS) for the composites prepared in Examples 1 to 3. FIG.
9 is a result of evaluating the oxygen reduction reaction (ORR) catalytic activity of the composites prepared in Examples 1 to 3 and Comparative Examples 3 and 4:
Here, (a) is a curve analyzed by cyclic voltammetry (CV),
(b) is an ORR polarization curve obtained by performing linear scanning voltammetry (LSV),
(c) is a graph showing the number of electron transfers per oxygen molecule (n) and hydrogen peroxide production rate of the complex calculated from the rotating ring-disk electrode (RRDE) test,
(d) is a graph showing the preliminary limiting current density according to the preliminary rotation square root velocity at various potentials through the KL plot,
(e) is a graph showing the current density of the electrode system after methanol is added to the electrolyte.
10 is an experimental result of evaluating the electrochemical stability of the electrode system including the composite of Example 2 and a platinum/carbon (Pt/C) catalyst:
Here, (a) is a graph showing the results of the chronoamperometric test,
(b) is a graph showing the current density in the case of measuring the current density of the electrode system once and after repeated measurements of 10,000 times.
11 is a result of evaluating the oxygen production reaction (OER) catalytic activity of the composites prepared in Examples 1 to 3 and Comparative Examples 3 and 4:
Here, (a) is the OER polarization curve obtained by performing the linear scanning voltammetry (LSV),
(b) is the Tafel curve for the electrode system containing each composite,
(c) is a graph showing the linear scanning voltage current (LSV) for the composite of Example 2 in the range of 0.4 to 1.6 V,
(d) is a graph showing the results of the chronoamperometric test.
12 is a result of evaluating the hydrogen production reaction (HER) catalytic activity of the complexes prepared in Examples 1 to 3 and Comparative Examples 3 and 4:
Here, (a) is a HER polarization curve obtained by performing a linear scanning voltammetry (LSV),
(b) is the Tafel curve for the electrode system containing each composite,
(c) is a graph measuring the current density according to the potential once and 2,000 times in the electrode system including the composite of Example 2 at a scan rate of 10 mA/s,
(d) is a graph showing the results of the chronoamperometric test.
13 is a graph showing the electrochemical impedance of composites of Examples 1 to 3;
14 is a graph showing the electrical conductivity of composites of Examples 1 to 3;

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present invention, terms such as "comprises" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof does not preclude in advance.

In addition, the accompanying drawings in the present invention should be understood as being enlarged or reduced for convenience of description.

The present invention relates to a composite including boron-doped carbon quantum dots and a method of manufacturing the same.

In recent years, the demand for the development of new and sustainable energy conversion and energy storage devices has increased to solve the energy crisis and environmental pollution, and accordingly, fuel cells, rechargeable metal air cells and water distribution to realize clean energy technology. Many energy systems such as devices have been developed. The basic operation of these systems mainly depends on three main electrochemical reactions: oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and ORR and OER are considered to be the two main electrochemical reactions. have. OER and HER are two important electrochemical reactions in the water separation process, or the slow reaction rate and high overvoltage, which limits the overall efficiency of the energy device. Accordingly, efforts have been made to solve this problem by using noble metal and transition metal catalysts, including Pt for ORR and HER, and Ir and Ru for OER. However, the scarcity and high cost of noble metal-based catalysts hinder the widespread technical use and large-scale application of these electrochemical energy technologies. Accordingly, there is a need for development of a multifunctional catalyst applicable to both oxygen reduction reactions (ORR), oxygen generation reactions (OER), and hydrogen generation reactions (HER) because of abundant resources, economical, easy synthesis, and excellent catalytic activity.

Accordingly, the present invention provides a composite including boron-doped carbon quantum dots.

Since the complex is manufactured through a hydrothermal reaction of a mixture containing glucose, boronic acid and graphene oxide, the process is simple and environmentally friendly. In addition, the prepared composite has high porosity and specific surface area, has excellent electrical properties due to abundant active sites, and has excellent stability even under alkaline conditions, so it has high electrolyte material transfer and ion diffusion ability, so oxygen reduction reaction (ORR), oxygen generation reaction It can be usefully used as a multifunctional catalyst used in (OER) and/or hydrogen generation reaction (HER).

Hereinafter, the present invention will be described in more detail.

Complex

The present invention in one embodiment,

Graphene hydrogel; And

It provides a composite including carbon quantum dots dispersed on the inside and the surface of the graphene hydrogel and doped with boron.

The composite according to the present invention includes a graphene hydrogel (GH) having a three-dimensional porous structure by connecting two-dimensional graphene sheets to each other through self-assembly, and on the inside and the surface of the graphene hydrogel. It has a structure in which boron-doped carbon quantum dots are dispersed.

At this time, the boron-doped carbon quantum dots may be fixed on the surface of the graphene sheet included in the graphene hydrogel through a π-π bond with the graphene sheet, through which the carbon quantum dots are fixed to the surface and the inside of the graphene hydrogel. It can have a distributed form.

In addition, the carbon quantum dots may have an average size of 1 nm to 10 nm, specifically, may have an average size of 1 nm to 8 nm, of which carbon quantum dots having an average diameter of 3 nm to 6 nm are all It may occupy about 75% to 85% of the carbon quantum dots.

In addition, the content of boron doped in the carbon quantum dots may be 0.1 atomic% to 10.0 atomic %, more specifically 0.1 atomic% to 8.0 atomic %, 0.5 atomic% to 7.0 atomic %, and 1.0 atomic% with respect to the entire composite. To 5.0 atomic%, 2.0 atomic% to 5.0 atomic%, 2.5 atomic% to 4.5 atomic%, 3.0 atomic% to 5.0 atomic%, or 4.1 atomic% to 4.9 atomic%.

The present invention can optimize the disorder or defect of the carbon structure by controlling the content of boron doped in the carbon quantum dot in the above range, and by controlling the position where the boron element is introduced into the carbon element. Since electron transfer within a substance may be improved or a binding rate with an oxygen-containing substance may be improved, excellent catalytic activity for an oxygen reduction reaction (ORR), an oxygen generation reaction (OER), and/or a hydrogen generation reaction (HER) may be exhibited.

As an example, the composite according to the present invention is doped with a certain amount of boron in a carbon quantum dot to contain a disorder or defect in a carbon structure, and thus, a D band peak indicating the degree of disorder or defect present in the carbon lattice during Raman spectroscopy analysis is obtained. And can satisfy Equation 1 below:

[Equation 1]

0.8 ≤ I _D /I _G

In Equation 1,

I _D represents the intensity of the peak present in the range of 1330 to 1360 cm ^-1,

I _G represents the intensity of the peak present in the range of 1580 to 1610 cm ^-1.

Specifically, in the Raman spectroscopy analysis, the G band peak representing the sp2 orbital of the aromatic structure has ^{a chemical shift value of about 1595±1 cm -1} , and the D band peak representing the degree of disorder or defect present in the carbon lattice is about 1350. It has a chemical shift value of ±1 cm ^-1. The composite of the present invention exhibits both the G-band peak and the D-band peak, and the degree of interference or bonding of the carbon lattice is controlled within a certain range, so that the intensity ratio (I _D / I _G ) of these peaks is 0.8 or more, specifically 0.8 To 1.0, 0.8 to 0.95, 0.8 to 0.9, or 0.85 to 0.89.

As another example, since the composite may control the position at which the boron element is introduced into the carbon element, the bonding position and/or relationship between the boron element and the carbon element may be controlled to satisfy Equation 2:

[Equation 2] I ₁₈₉ /I ₁₉₁ > 1.0

In Equation 2,

I ₁₈₉ represents the intensity of the peak present at 189±0.4 eV,

I ₁₉₁ represents the intensity of the peak present at 191±0.4 eV.

Specifically, the composite is doped with boron on carbon quantum dots, indicating the bond between the boron element and the carbon element in X-ray photoelectron spectroscopy (XPS) analysis. Can show a peak at.

Here, the peaks appearing at 189±0.4 eV, 190±0.4 eV, and 191±0.4 eV are peaks representing the binding energy of the BC3 bonding structure, the BC2O bonding structure, and the BCO2 bonding structure, respectively, and the composite of the present invention is doped with carbon quantum dots. Depending on the content of boron, the ratio of the bond structure between the boron element and the carbon element is controlled, so that the intensity ratio of the peak indicating the bonding energy of the BC3 bond structure and the BCO2 bond structure (I ₁₈₉ / I ₁₉₁ ) is 1.0 or more, specifically 1.0 to 2.0. ; 1.0 to 1.8; 1.0 to 1.6; 1.0 to 1.5; 1.0 to 1.4; Alternatively, Equation 2 may be satisfied by 1.0 to 1.3.

The BC3 bond is a base planar species formed by replacing a carbon atom with a boron atom without destroying the planar bond, and electrons of the boron atom included in the BC3 bond may move toward the carbon element due to lower electronegativity. Since charge redistribution by the BC3 bond can improve electron transfer in the plane, as an active catalytic site, a polarized site on the boron-doped carbon quantum dots may be generated. In comparison, BC2O and BCO2 bonds are mainly located at the edge of boron-doped carbon quantum dots and can be appropriately bonded with oxygen-containing intermediates such as _{water molecules (H 2 O) or molecules having a hydroxyl group (OH).} And when the ratio of boron participating in the BCO2 bonding is high, the catalytic activity of the oxygen production reaction (OER) and/or the hydrogen production reaction (HER) may be excellent.

Meanwhile, the composite according to the present invention may include a graphene hydrogel (GH) having a three-dimensional porous structure as described above and may have a large average BET specific surface area.

Specifically, the composite includes a graphene hydrogel (GH) having a 3D porous structure by interconnecting the walls of graphene sheets forming pores having an average size of 0.1 μm to 10 μm when analyzed by a scanning electron microscope. , When measuring the BET specific surface area, the average BET specific surface area and the average size of the pores included in the composite may be 100 m 2 /g to 500 m 2 /g and 1 nm to 10 nm, respectively.

As an example, the composite has an average BET specific surface area of 100 m2/g to 400 m2/g, 100 m2/g to 350 m2/g, 100 m2/g to 340 m2/g, 200 m2/g to 340 m2 /g or 300 m2/g to 340 m2/g, and the average pore size is 1 nm to 9 nm, 1 nm to 8 nm, 2 nm to 8.5 nm, 4 nm to 8.5 nm, or 5 nm to 8.5 nm I can. The present invention can further promote the electrochemical activity of the composite by controlling the average BET specific surface area and the average pore size of the composite within the above range.

Manufacturing method of composite

In addition, the present invention in one embodiment,

Forming a reaction intermediate by performing a hydrothermal reaction of a mixture containing glucose, boronic acid, and graphene oxide; And

Performing a reduction reaction of the formed reaction intermediate to prepare a composite including a graphene hydrogel in which boron-doped carbon quantum dots are dispersed on a surface;

It provides a method for producing a composite comprising a.

The manufacturing method of the composite according to the present invention includes graphene oxide (GO) as a raw material for graphene hydrogel (GH), glucose as a raw material for carbon quantum dots (GQD), and boronic acid as a raw material for boron doped on carbon quantum dots. acid) after performing a hydrothermal reaction of the mixture, and subsequently reducing the reaction intermediate produced by the hydrothermal reaction to prepare a complex in a one-pot manner.

At this time, in the step of performing a hydrothermal reaction of the mixture, the mixture may have a form in which graphene oxide (GO), glucose and boronic acid are dissolved or dispersed in water as a solvent, and as an additive, a strong acid such as sulfuric acid may be further included. I can.

In addition, the amount of glucose contained in the mixture may be included in an amount of 50 parts by weight to 100 parts by weight based on 100 parts by weight of graphene oxide, and specifically, 50 parts by weight to 90 parts by weight; 50 to 85 parts by weight; 60 to 90 parts by weight; Alternatively, it may be included in an amount of 70 parts by weight to 90 parts by weight.

In addition, the amount of boronic acid contained in the mixture may be included in an amount of 1 to 15 parts by weight based on 100 parts by weight of glucose, and specifically, 1 to 13 parts by weight; 1 to 11 parts by weight; 1 to 10 parts by weight; 1 to 9 parts by weight; 1 to 6 parts by weight; 1 to 5 parts by weight; 3 parts by weight to 13 parts by weight; 5 parts by weight to 13 parts by weight; 7 parts by weight to 13 parts by weight; 11 to 14 parts by weight; Or it may be included in 5 parts by weight to 9 parts by weight.

Further, the hydrothermal reaction may be performed at a temperature of 150° C. to 200° C. for 10 to 30 hours, and specifically at a temperature of 170° C. to 190° C. for 20 to 28 hours.

In addition, the step of reducing the reaction intermediate is not particularly limited and may be applied as long as it is a method commonly used in the art to reduce the carbon material, but in the present invention, ascorbic acid, hydrogen iodide (HI), hydrogen bromide ( HBr) and hydrogen chloride (HCl) using one or more reducing agents selected from the group consisting of (concentration: 50 ~ 60 vol.%) can be carried out by reacting for 4 ~ 6 hours at 35 ~ 45 ℃.

The present invention is a problem in that not only a composite can be manufactured simply by performing a hydrothermal reaction and a reduction reaction of raw materials continuously under the above-described conditions, but also a conventional carbon structure/material, specifically, a carbon quantum dot, in which boron is doped at a low ratio. Can be solved effectively.

Electrode catalyst

Furthermore, in one embodiment, the present invention provides a catalyst including the complex.

Since the catalyst according to the present invention exhibits high catalytic activity in oxygen reduction reaction (ORR), oxygen generation reaction (OER) and/or hydrogen generation reaction (HER) including the above-described complex, metal-air cells, fuel cells, It is useful as a multifunctional catalyst that can be used in any water decomposition device.

Hereinafter, the present invention will be described in more detail by examples and experimental examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following Examples and Experimental Examples.

Examples 1 to 3.

Glucose (120 mg), boronic acid, and sulfuric acid (100 µl) were added to distilled water (10 ㎖), and after mixing by irradiating with ultrasonic waves for 20 minutes, a graphene oxide solution (20 ㎖, concentration: 3) while stirring vigorously for 30 minutes. mg/ml, graphene oxide content: 150 mg) was slowly added dropwise. When the dropwise addition was completed, the mixture was transferred to a stainless steel autoclave having a capacity of 100 ml equipped with a Teflon line, and hydrothermal reaction was performed at 180° C. for 24 hours. When the reaction was completed, the solid product formed in the solution was collected and immersed in distilled water for 12 hours to remove impurities, and the reduction reaction was performed by immersing in 55 vol.% hydrogen iodide (HI) aqueous solution at 40° C. for 5 hours. Thereafter, the product was collected, washed with distilled water, and dried at 90° C. for 1 hour to prepare a composite (GH-BGQD) in which boron-doped carbon quantum dots (BGQD) were dispersed in graphene hydrogel (GH). I did.

At this time, the content of boronic acid used in the preparation of the composite (GH-BGQD) and the content of boron doped in the carbon quantum dots are as shown in Table 1 below:

Boronic acid consumption Based on 100 parts by weight of glucose
Boronic acid content Content of boron doped in carbon quantum dots Example 1 5 mg 4.1 parts by weight 2.8±0.2 atomic% Example 2 10 mg 8.3 parts by weight 4.4±0.2 atomic% Example 3 15 mg 12.5 parts by weight 4.8±0.2 atomic%

Comparative Example 1.

Glucose (120 mg), boronic acid (10 mg), and sulfuric acid (100 µl) were added to distilled water (10 ㎖), and the mixture was mixed by irradiation with ultrasonic waves for 20 minutes, and then the mixture was mixed with a stainless steel of 100 ㎖ equipped with a Teflon line Transferred to an autoclave and subjected to a hydrothermal reaction at 180° C. for 24 hours. When the reaction was completed, the solid product formed in the solution was collected and immersed in distilled water for 12 hours to remove impurities to prepare boron-doped carbon quantum dots (B-GQD). At this time, the content of boronic acid based on 100 parts by weight of glucose was 8.3 parts by weight.

Comparative Example 2.

Graphene oxide solution (20 ml, concentration: 3 mg/ml, graphene oxide content: 150 mg) and boronic acid (10 mg) were transferred to a 100 ml stainless steel autoclave equipped with a Teflon line and placed for 24 hours. Hydrothermal reaction was performed at 180°C. When the reaction was completed, the solid product formed in the solution was collected and immersed in distilled water for 12 hours to remove impurities, and the reduction reaction was performed by immersing in 55 vol.% hydrogen iodide (HI) aqueous solution at 40° C. for 5 hours. Thereafter, the product was collected, washed with distilled water, and dried at 90° C. for 1 hour to prepare a graphene hydrogel (GH).

Comparative Example 3.

A composite (GH-GQD) in which carbon quantum dots (GQD) were dispersed in graphene hydrogel (GH) was prepared by performing the same reaction as in Example 1, except that boronic acid was not mixed in the mixture.

Comparative Example 4.

The complex (B-GQD) obtained in Comparative Example 1 and 55 vol.% hydrogen iodide (HI) aqueous solution were added to the graphene oxide solution (20 ml, concentration: 3 mg/ml, graphene oxide content: 150 mg). Uniformly mixed and subjected to a reduction reaction at 40° C. for 5 hours to prepare a composite (G-BGQD) in which boron-doped carbon quantum dots (B-GQD) were dispersed in reduced graphene oxide (rGO).

Experimental Example 1.

In order to evaluate the shape and structure of the composite according to the present invention, targeting the composites of Examples 1 to 3 and Comparative Examples 1 to 4, ① Field Emission-Scanning Electron Microscopy (FE-SEM), ② Transmission Electron Microscopy (TEM), ③ High-Resolution Transmission Electron Microscopy (HR-TEM), ④ BET specific surface area, ⑤ Raman spectroscopy, ⑥ X-Ray Diffraction, XRD) and ⑦ X-ray Photoelectron Spectroscopy (XPS) analysis was performed, and the results are shown in FIGS. 2 to 8 and Tables 2 and 3. Specific analysis conditions are as follows:

-Field emission scanning electron microscope (FE-SEM) was measured using JEOL's JSM-6500F and JEM-2100F.

-High-resolution transmission electron microscope (HR-TEM) analysis: Using JEOL's JEM-ARM200F high-resolution transmission electron microscope (Cs-Corrector), the surface of the specimen was measured by scanning a wavelength of 0.025 Å at a resolution of 200 keV and measuring the transmitted electron beam. Images were taken, and the electron beam diffracted at the same time was subjected to Fast Fourier Transformation (FFT) to obtain a Selected Area Electron Diffraction (SAED) pattern.

-Specific surface area: Calculated by Brunauer-Emmett-Teller (BET) analysis using Micromeritics' nitrogen adsorption analyzer (ASAP 2020).

-X-ray photoelectron spectroscopy (XPS): X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy) in a binding energy range of 100 eV to 900 eV using monochromatic AlKα radiation (hv = 1486.6 eV) using Thermo Fish's X-ray photoelectron spectroscopy, XPS) was measured.

2 to 8 and Tables 2 and 3, it can be seen that the composite according to the present invention has a structure in which boron-doped carbon quantum dots are uniformly dispersed in a graphene hydrogel.

Specifically, FIG. 2 is an image of analyzing the composite of the Example with a scanning electron microscope (SEM), and the composite of the Example is graphene forming pores having an average size of 0.1 µm to 10 µm, specifically 0.1 µm to 5 µm. It can be seen that the walls of the sheet are interconnected to each other to include graphene hydrogel (GH) having a 3D porous structure.

In addition, Figures 3 and 4 are images analyzed by a transmission electron microscope (TEM) and a high-resolution transmission electron microscope (HR-TEM), respectively, of the composite (GH-BGQD) of the embodiment, and the transmission electron microscope (TEM) and corresponding elements Looking at the elemental mapping images, it can be seen that carbon, oxygen, and boron elements are uniformly distributed. This means that the boron-doped carbon quantum dots contained in the composite are not aggregated and are uniformly dispersed on the surface and/or inside of the graphene hydrogel (GH). In addition, boron-doped carbon quantum dots have a structure of high crystallinity and have a lattice spacing of 0.24 nm corresponding to the (1120) lattice, and have an average diameter of 1 nm to 8 nm, and an average diameter of 3 nm to 6 nm. It was found that carbon quantum dots account for about 75% to 85% of the total carbon quantum dots.

In addition, Figure 5 is a graph showing the results of measuring the BET specific surface area for the composites of Comparative Examples 2 and 4 and Example 2. Referring to FIG. 5 and Table 2 below, the composite of Example 2 includes a graphene hydrogel having a 3D porous structure and exhibits a large average BET specific surface area of 300 m 2 /g or more, but boron-doped carbon It was confirmed that the composite of Comparative Example 4 dispersed in the graphene sheet from which the quantum dots were reduced has a remarkably low specific surface area of less than 100 m 2 /g. In addition, the composite of Example 2 was found to have a relatively large specific surface area compared to Comparative Example 2 containing only graphene hydrogel, which is formed at the same time as the graphene hydrogel boron-doped carbon quantum dots Compared to the graphene hydrogel of Comparative Example 2, it means that a graphene hydrogel having a higher porosity is formed, and such a high porosity structure provides an effective diffusion path to the active site in the electrolyte or intermediate, thereby providing an electrochemical reaction. It can function to promote:

Average BET specific surface area
[㎡/g] Average volume of pores
[Cm3/g] Average pore size
[nm] Example 2 320.3 0.67 6.9 Comparative Example 2 343.1 0.65 8.6 Comparative Example 4 77.4 0.13 10.3

In addition, FIG. 6 is a graph showing the results of Raman spectroscopy analysis of the complex of Example 2 (GH-BGQD) and the complex of Comparative Example 2 (GH-GQD). Referring to FIG. 6, Example 2 and Comparative Example 2 When the Raman spectrum was measured, ^{it was found that a peak having a chemical shift value of about 1595 ± 1 cm -1} and a peak having a chemical shift value of about 1350 ± 1 cm ^-1 existed. These peaks are the G band representing the sp2 orbital of the aromatic structure and the D band representing the degree of disorder or defect present in the carbon lattice of the carbon material, respectively. Through these intensity ratio of the peak (I _D / I _G) may estimate the degree of failure or defect of the carbon material composite of Example 2 is the a 0.87 ± 0.05 a peak intensity ratio (I _D / I _G), while, The composite of Comparative Example 2 was found to have a peak intensity ratio (I _D /I _G ) of 0.75±0.05. This indicates that the composite of Example 2 is doped with boron on the carbon quantum dots and thus has more carbon defects. From this, it can be seen that the composite of Example 2 has higher activity than the composite of Comparative Example 2 when used as an electrocatalyst.

7 and 8 are graphs showing X-ray photoelectron spectroscopy results for the composites of Examples 1 to 3 and Comparative Example 3. Referring to FIG. 7, the composites of Example and Comparative Example are 530.4±2 eV and 284.2±2. In eV, it was confirmed that peaks representing the binding energy of the carbon element and the oxygen element exist, respectively. However, the composite of Comparative Example 3 (GH-GQD) did not have a peak indicating the binding energy to the boron element at about 190 ± 2 eV, whereas the composite of Example (GH-BGQD) was doped with boron on the carbon quantum dots. A peak indicating the binding energy to the boron element appeared at about 190±2 eV, and it was confirmed that the intensity of the peak increased as the content of boron doped in the carbon quantum dots increased from 2.8 atomic% to 4.8 atomic%. .

In addition, referring to FIG. 8, it was confirmed that the composites of Examples 1 to 3 exhibit different trends in the binding energy of the carbon element (C) and the binding energy of the boron element (B) according to the content of boron doped in the carbon quantum dots. . Specifically, the composites of the examples are C=C bonds, CO bonds, C=O bonds of aromatic carbons having sp2 orbitals at 284.5±0.2 eV, 286.6±0.2 eV, 287.3±0.2 eV, and 288.9±0.5 eV of the C1s spectrum, respectively. And a peak representing the binding energy of the OC=O bond, and a peak representing the binding energy of the BC bond at 283.7±0.5 eV. This indicates that boron has been introduced into the carbon network of carbon quantum dots. In addition, the complexes exhibited peaks representing the binding energy of BC4 binding, BC3 binding, BC2O binding and BCO2 binding at 187.7±0.4 eV, 189.0±0.4 eV, 190.1±0.4 eV, and 191.3±0.4 eV of the B1s spectrum, respectively. , As shown in Table 3 below, it was confirmed that the fraction of each peak was different depending on the content of boron doped in the carbon quantum dots:

Boron content Peak fraction BC4 combination BC3 combination BC2O bonding BCO2 binding Example 1 2.76 atomic% 0 atomic% 0.30 atomic% 0.43 atomic% 2.03 atomic% Example 2 4.41 atomic% 0.19 atomic% 2.07 atomic% 1.24 atomic% 0.91 atomic% Example 3 4.87 atomic% 0.51 atomic% 0.98 atomic% 1.39 atomic% 1.99 atomic%

Specifically, the composite of Example 2 has the highest content of boron participating in BC3 binding, and the BC3 binding energy peak present at 189.0±0.4 eV is the intensity ratio with the BC2O binding energy peak present at 191.3±0.4 eV (I ₁₈₉ /I ₁₉₁ ) was found to be between about 1.20 and 1.25. In contrast, the complexes of Examples 1 and 3 had a high content of boron participating in BC2O bonding and BCO2 bonding, so that the BC3 binding energy peak at 189.0±0.4 eV was compared with the BC2O binding energy peak at 191.3±0.4 eV. The intensity ratio (I ₁₈₉ /I ₁₉₁ ) was found to be about 0.47 and 0.89 dls, respectively.

The BC3 bond is a base planar species formed by replacing a carbon atom with a boron atom without destroying the planar bond, and electrons of the boron atom included in the BC3 bond may move toward the carbon element due to lower electronegativity. Since charge redistribution by the BC3 bond can improve electron transfer in a plane, as an active site, a polarized site on a boron-doped carbon quantum dot may be generated. In comparison, BC2O and BCO2 bonds are mainly located at the edge of boron-doped carbon quantum dots, so they can act to lower electrical conductivity, but _{oxygen such as water molecules (H 2} O) or molecules having a hydroxyl group (OH) Since it can be appropriately combined with the containing intermediate, the composite of Example 3 having a high ratio of boron participating in BC2O and BCO2 bonding may have excellent catalytic activity of the oxygen production reaction (OER) and/or the hydrogen production reaction (HER). have.

On the other hand, from the X-ray photoelectron spectroscopy results of the graphene hydrogel (GH) of Comparative Example 2, the peak representing the binding energy to the boron element at about 190±2 eV even though boronic acid was used in the preparation of the graphene hydrogel was It was found to be non-existent. This means that doping of boron is induced during graphitization of glucose, not graphene hydrogel.

From these results, it can be seen that the composite according to the present invention has a structure in which boron-doped carbon quantum dots are uniformly dispersed and fixed in the graphene hydrogel, thereby having excellent electrical properties.

Experimental Example 2.

In order to evaluate the electrochemical properties of the composite according to the present invention, a three-electrode system was prepared for the composites of Examples 1 to 3 and Comparative Examples 1 to 4. Specifically, the complexes (5 ml) prepared in Examples and/or Comparative Examples were added to isopropyl alcohol (4.975 ml) together with Nafion solution (25 μl, 0.5% by weight, DuPont), and catalytic activity was performed by sonication. A paste was prepared. The prepared paste was loaded on a glass-carbon electrode (GCE, diameter 4 mm) and a platinum (Pt) ring (inner diameter: 5.5 mm, outer diameter: 7.2 mm) to prepare a working electrode. As a comparative working electrode, an electrode using platinum/carbon (Pt/C, containing 20% Pt on Vulcan XC72) and iridium/carbon (Ir/C, containing 20% Ir on Vulcan XC-72) instead of the composite were also fabricated. In addition, a graphite rod is used as a counter electrode for oxygen reduction reaction (ORR) and hydrogen production reaction (HER), and a Pt wire is used as a counter electrode for oxygen production reaction (OER), so that a saturated calomel electrode (SCE) is used for all reactions. A system to be used as a reference electrode was fabricated. The following experiments were performed on the fabricated electrode systems, and the following experimental results for the electrode system are shown in FIGS. 9 to 12.

A) Evaluation of physical properties for oxygen reduction reaction (ORR)

-The ORR performance was evaluated by performing Cyclic Voltammetry (CV) on the electrode system including the composites of Examples and Comparative Examples. At this time, the cyclic voltammetry is performed using a 0.1M KOH solution saturated with _{N 2 or a 0.1M KOH solution saturated with O 2} as an electrolyte solution within a potential range of 0.0 to 1.2V at a scan rate of 10 mV/s. It was performed, and the results for the complex of Example 2 (GH-BGQD) are shown in FIG. 9(a).

Referring to FIG. 9(a), in the case of the composite of Example 2, when the electrolyte solution was _{a 0.1M KOH solution saturated with N 2} , a characteristic peak was not observed, whereas a 0.1M KOH solution saturated with _{O 2 was used.} In the case of use, a distinct cathode peak was clearly observed at 0.61V due to a substantial increase in current density. This means that the composites of the examples exhibit remarkable electrocatalytic activity for ORR.

-In addition, linear scanning voltammetry (LSV) was performed on electrode systems including composites of Examples 1 to 3 and Comparative Examples 3 and 4. In this case, the linear scanning voltammetry _{was performed using a 0.1M KOH solution saturated with O 2} as an electrolyte solution, and a rotational speed of 1600 rpm using a rotating disk electrode (RDE), and the results are shown in Fig. 9(b). ).

Referring to FIG. 9(b), it can be seen that the composites of the Example have a better initiation potential and a greater current density compared to the composite of Comparative Example 3 in which carbon quantum dots not doped with boron are dispersed in a graphene hydrogel. have. This is due to the increase in active sites by doping boron on the carbon quantum dots. In addition, looking at the curves of the composites of Examples 1 to 3, the polarization curve is different depending on the content of boron doped in the carbon quantum dots, Example 2 in which the content of boron doped in the carbon quantum dots is 3.0 atomic% or more with respect to the entire composite, and The composite of 3 exhibited significantly higher initiation potential and limiting current density than the composite of Comparative Example 4 in which boron-doped carbon quantum dots were dispersed in graphene. In particular, the composite of Example 2 exhibits the most excellent physical properties among the composites of the example with the maximum starting potential and the maximum limiting current density of 0.93 V and 5.74 mA/cm 2, respectively, and the maximum of platinum/carbon (Pt/C) used in the conventional ORR catalyst The starting potential (0.93V) and the maximum limiting current density (4.03 mA/cm2) are equivalent to or better than those of the catalyst. In addition, the composite of Example 2 has a half-wave potential of 0.87 V, which is higher than the half-wave potential of 0.85 V of a platinum/carbon (Pt/C) catalyst, so that the ORR performance is higher than that of a platinum/carbon (Pt/C) catalyst. Able to know.

In addition, in the present invention, a rotating ring disk experiment (RRDE) was performed under different rotational speed conditions for an electrode system including the composites of the examples, and a Koutecky-Levich (KL) plot was obtained from the corresponding curve. At this time, the rotating ring disk experiment (RRDE) was _{performed at a speed of 1600 rpm using a 0.1M KOH solution saturated with O 2} as an electrolyte, and the measured results are shown in FIGS. 9(c) and (d).

Referring to Figures 9(c) and (d), it can be seen that the current density increases simultaneously with the rotational speed due to the shorter diffusion length and higher speed of the composites. It can be seen that there is a high linearity between the limiting current densities. In addition, the number of electron transfers per oxygen molecule (n) of the complex calculated from the rotating ring-disk electrode (RRDE) test is 3.73 to 3.92 in the range of 0.4 to 0.8 V, and the hydrogen peroxide (H ₂ O ₂ ) production rate of the complexes is studied. It was found to be less than 18% in the total potential range and 15% at 0.8V. This means that the complexes of the examples exhibit high ORR catalytic activity through a 4-electron reaction pathway.

-Further, in order to check the methanol resistance of the composites, methanol was added to the electrolyte provided in the system while measuring the current density of the electrode system including the composite of Example 2 for 1200 seconds, after which the current density of the electrode system was changed. Was observed. The electrode system using a platinum/carbon (Pt/C) catalyst as a control was also observed to change the current density in the same manner. As a result, referring to FIG. 9(e), the current density of the electrode system including the composite of Example 2 was stably maintained, but the current density was significantly reduced in the case of the electrode system using a platinum/carbon (Pt/C) catalyst. It was confirmed to be.

-In addition, a chronoamperometric test was performed to confirm the electrochemical stability of the electrode system including the composite of Example 2 and the platinum/carbon (Pt/C) catalyst, respectively. The results are shown in FIG. 10, and in FIG. 10 (a) in _{a 0.1M KOH solution in which O 2} is present, current density according to measurement time of each electrode system is shown under a rotation speed of 0.4V and 1600 rpm, (b) shows the current density when the electrode system including the composite of Example 2 _{was measured once in a 0.1M KOH solution in the presence of O 2} and a rotation speed of 1600 rpm and repeated 10,000 times. It shows the ORR polarization curve obtained after CV scan.

Referring to FIG. 10, the initial current density of the composite of Example 2 was maintained at about 94% after 25 hours of continuous measurement, whereas the platinum/carbon (Pt/C) catalyst reduced the current density to 38% of the initial density. Appeared to be. In addition, the composite was found to maintain the initiation potential and current density without deterioration even after 10,000 measurements.

This means that the graphene hydrogel having a three-dimensional porous structure can stably maintain the structure by preventing agglomeration or separation of carbon quantum dots dispersed on the surface and/or inside. It can be seen that it has electrical stability.

From these results, it can be seen that the composite according to the present invention is useful as a catalyst for oxygen reduction reaction (ORR).

B) Evaluation of physical properties for oxygen evolution reaction (OER)

-OER polarization curve by performing Linear Sweep Voltammetry (LSV) on the electrode system including the composites of Examples 1 to 3 and Comparative Examples 3 and 4 and an iridium/carbon (Ir/C) catalyst Got it. In this case, the linear scanning voltammetry _{was performed using a 0.1M KOH solution saturated with N 2} as an electrolyte solution, and a rotational speed of 1600 rpm using a rotating disk electrode (RDE), and the results are shown in Fig. 11(a). ).

Referring to FIG. 11(a), the composites of the Example are of Comparative Example 3 in which carbon quantum dots not doped with boron are dispersed in graphene hydrogel and Comparative Example 4 in which carbon quantum dots doped with boron are dispersed in graphene. It was found to have a low onset potential compared to the complex. This means that the composites of the examples have boron-doped carbon quantum dots uniformly dispersed and fixed in the graphene hydrogel to further improve catalyst efficiency. In addition, looking at the polarization curves of the composites of Examples 1 to 3, the polarization curves are different depending on the content of boron doped in the carbon quantum dots.In particular, the composite of Example 2 has an overpotential of 370 mV at a current density of 10 mA/cm2. It was confirmed to have. This performance means that the porous structure of the graphene hydrogel is involved in the efficient mass transport of oxygen intermediates.

-In addition, Tafel curves were analyzed for electrode systems each including the composites of Examples 1 to 3 and an iridium/carbon (Ir/C) catalyst. The results are shown in Fig. 11(b).

Referring to FIG. 11(b), the composites of Examples 1 to 3 had a tapel slope of 125, 70 and 84 mV/dec, respectively, and the composite of Example 2 was shown to have the lowest tapel slope among the composites of Examples. . This means that the Tafel slope is low even compared to the iridium/carbon (Ir/C) catalyst, which means that the composite of Example 2 exhibits the most favorable kinetic reaction with respect to OER. In addition, looking at the linear scanning voltage current (LSV) curve in the range of 0.4 to 1.6 V shown in FIG. 11(c), the composite of Example 2 is a bifunctional catalyst for an oxygen reduction reaction (ORR) and an oxygen production reaction (OER). It can be seen that it has an activity, and the potential difference ΔE between the reactions is 0.73V (here, the ΔE is the operating potential (E _{j = 10} ) transferred at 10 mA/cm 2 with respect to the OER) and the half wave potential of the ORR (E _{1/ 2} ) shows the difference), it can be seen that it has a small value compared to the conventional metal-based catalyst. This means that the complex of Example 2 has a high bifunctional catalytic activity against ORR and OER.

In addition, a chronoamperometric test was performed on the electrode system including the composite of Example 2 and an iridium/carbon (Ir/C) catalyst. Specifically, the test was performed under a rotational speed of 0.4V and 1600 rpm in a 0.1M KOH solution in the presence _{of N 2, and the results are shown in FIG. 11(d).}

Referring to FIG. 11(d), the composite of Example 2 was measured at a constant potential of 1.55 V while continuously measured for 10 hours, and it was confirmed that the initial current density was maintained at about 95.7%. In contrast, the iridium/carbon (Ir/C) catalyst showed a remarkably large current density loss. In addition, it was confirmed that the change in the potential region was not large even after the composite of Example 2 was repeatedly used 500 times.

From these results, it can be seen that the composite according to the present invention is useful as a catalyst for oxygen production reaction (OER).

C) Evaluation of physical properties for hydrogen generation reaction (HER)

-Linear scanning voltammetry (LSV) was performed on the composites of Examples 1 to 3 and Comparative Examples 3 and 4 and an electrode system including a platinum/carbon (Pt/C) catalyst to obtain a HER polarization curve. At this time, the linear scanning voltammetry _{was performed using a 0.1M KOH solution saturated with N 2} as an electrolyte solution, and a rotational speed of 1600 rpm using a rotating disk electrode (RDE), and the results are shown in Fig. 12(a). ).

Referring to FIG. 12(a), it was found that the composites of the Example had a lower current density compared to the composite of Comparative Example 3 in which carbon quantum dots not doped with boron were dispersed in a graphene hydrogel. This indicates that the complexes of the Example have excellent HER catalytic activity compared to the complex of Comparative Example 3. In addition, looking at the polarization curves of the composites of Examples 1 to 3, the initial potentials were -0.41 V, -0.25 V, and -0.33 V, respectively, depending on the content of boron doped in the carbon quantum dots, indicating that the value of Example 2 was the lowest. Able to know. In addition, it was confirmed that the composite of Example 2 had an overpotential of 130 mV at a current density of -10 mA/cm 2. This means that the content of boron doped in the carbon quantum dots affects the catalytic activity of the composite.

-In addition, Tapel curves were analyzed for the composites of Examples 1 to 3 and electrode systems each including a platinum/carbon (Pt/C) catalyst, and the results are shown in FIG. 12(b).

Referring to FIG. 12(b), the composite of Example 2 has a Tapel slope of 95 mA/cm 2, which is low compared to the composites of Examples 1 and 3, and has a similar value to that of the platinum/carbon (Pt/C) catalyst. Was confirmed. In addition, the composite of Example 2 was found to have a constant curve even when the experiment was performed at a scanning speed of 5 to 100 mA/s. This means that the complexes of the examples have excellent HER reactivity.

-In addition, in order to evaluate the stability of the composite/catalyst, the linear scanning voltammetry (LSV) and chronoamperometric test of the electrode system including the composite of Example 2 and a platinum/carbon (Pt/C) catalyst Was performed respectively. At this time, in the time vs. current test, a curve was measured at a constant overpotential of 410 mA for 10 hours, and each measurement result is shown in FIGS. 12(c) and 12(d).

12(c) is a HER polarization curve calculated from the linear scanning voltammetry curve of the composite of Example 2 measured at a current density of 10 mA/cm 2, and the composite of Example 2 is performed once at a scan rate of 10 mA/s. And even after 2,000 measurements, the potential change was insignificant, indicating that the potential change amount was about 8 mA or less.

In addition, FIG. 12(d) is a time vs. current test curve for the composite of Example 2, and it was confirmed that the composite of Example 2 maintained about 93.8% of the initial current density even when continuously measured for 10 hours. In contrast, the platinum/carbon (Pt/C) catalyst exhibited a remarkably large current density loss. This indicates that the structural and electrochemical stability of the composite of Example is excellent.

From these results, it can be seen that the composite according to the present invention is economical and environmentally friendly, and is useful as a multifunctional catalyst having excellent activity in oxygen reduction reaction (ORR), oxygen production reaction (OER), and hydrogen production reaction (HER).

Experimental Example 3.

In order to confirm the difference in catalyst performance according to the boron content of the composite according to the present invention, the following experiment was performed.

A) Density functional theory analysis (DFT analysis)

First, in order to confirm the effect of doped boron on carbon quantum dots, oxygen (O ₂ ), hydroxyl group (-OH) and water (H ₂ O) for each boron-carbon bond structure using density functional theory (DFT) analysis. The adsorption energy for was calculated, and the results are shown in Table 4 below.

Adsorption energy O ₂ -OH H ₂ O Non-doped -0.084 eV -0.316 eV -0.159 eV BC3 bonding structure -0.204 eV -1.795 eV -0.185 eV BC2O bonding structure -0.162 eV -1.690 eV -0.196 eV BCO2 bonding structure -0.137 eV -1.809 eV -0.202 eV

Looking at Table 4, it can be seen that when the carbon quantum dots are doped with boron, they have lower adsorption energies for oxygen, hydroxyl groups, and water than when boron is not doped. This indicates that the carbon quantum dots are doped with boron to facilitate adsorption to oxygen, hydroxyl groups, and water.

In addition, the BC3 bonded structure had an adsorption energy of -0.204 eV for oxygen, indicating that the adsorption capacity for oxygen was the best. This means that the reactivity of the BC3 structure is advantageous in ORR.

In addition, the BCO2 bonding structure showed the lowest values of adsorption energies for hydroxyl group and water, respectively -1.809 eV and -0.202 eV. It is known that boron atoms having a conventional BCO2 bonded structure have a large electronegativity and are easily polarized, thereby adsorbing hydroxyl groups and water at a high ratio by interacting with hydroxyl groups and hydrogen groups of water molecules with oxygen atoms. The adsorption energy is synonymous with this, indicating that the BCO2 bond structure has excellent adsorption capacity for hydroxyl groups and water.

On the other hand, the complex of Example 2 predominantly includes the BC3 bonding structure, and the BCO2 bonding structure is included in a slightly lower ratio than the complex of Example 3. This means that the composite of Example 2 may have excellent adsorption not only to oxygen, but also to hydroxyl groups and water.

A) Electrochemical impedance study

Electrochemical impedance and electrical conductivity were measured for the composites of Examples 1 to 3, and the results are shown in FIGS. 13 and 14.

Referring to FIG. 13, the composites of Examples 1 to 3 exhibited a semicircle in the low frequency region of the Nyquist curve, and the semicircle was found to have the smallest composite of Example 2 and a low charge transfer resistance value. This is a result of the composite of Example 2 containing a large amount of BC3 bonding structure similar to graphite. BC3 bonding structure increases the electron density and electrical conductivity of carbon atoms due to the high electronegativity of boron atoms, whereas BC2O bonding structure and/or BCO2 bonding structure can induce low electrical conductivity.

Specifically, referring to FIG. 14, it can be seen that ^{the composite of Example 2 has excellent electrical conductivity of 1.7 × 10 -4} S/cm or more by including a BC3 binding structure in a high ratio. This means that the composite of Example 2 has excellent charge transfer resistance and electrical conductivity, so that rapid charge transfer between the electrode and the electrolyte can be induced.

From these results, it can be seen that the excellent catalytic activity of the complex according to the present invention for ORR, OER and HER is due to the synergistic effect of excellent adsorption capacity and electrical properties for the reaction compound. Therefore, the complex of the present invention can be usefully used as a multifunctional catalyst for ORR, OER and HER.

Claims (14)

Graphene hydrogel; And
It is dispersed on the inside and the surface of the graphene hydrogel, and includes a composite including boron-doped carbon quantum dots,
The complex exhibited peaks at 283.5±0.4 eV, 189±0.4 eV, 190±0.4 eV, and 191±0.4 eV when analyzed by X-ray photoelectron spectroscopy (XPS),
The composite is an electrocatalyst of an oxygen evolution reaction (OER) or a hydrogen evolution reaction (HER) that satisfies the following formula:
[Equation 2]
I ₁₈₉ /I ₁₉₁ > 1.0
In Equation 2,
I ₁₈₉ represents the intensity of the peak present at 189.0±0.4 eV,
I ₁₉₁ represents the intensity of the peak present at 191.3±0.4 eV.
The method of claim 1,
Carbon quantum dots are electrocatalysts of oxygen generation reaction (OER) or hydrogen generation reaction (HER) fixed to the surface of graphene sheet of graphene hydrogel through π-π bonds.

The method of claim 1,
The content of boron is 0.1 atomic% to 10 atomic% with respect to the entire complex, an electrocatalyst of an oxygen generating reaction (OER) or a hydrogen generating reaction (HER).
The method of claim 1,
The complex is an electrocatalyst of an oxygen evolution reaction (OER) or a hydrogen evolution reaction (HER) that satisfies the following equation 1 when analyzed by Raman spectroscopy:
[Equation 1]
0.8 ≤ I _D /I _G
In Equation 1,
I _D represents the intensity of the peak present in the range of 1330 to 1360 cm ^-1,
I _G represents the intensity of the peak present in the range of 1580 to 1610 cm ^-1.
delete delete The method of claim 1,
The average BET specific surface area of the composite is 100 m2/g to 500 m2/g, which is an electrocatalyst for an oxygen evolution reaction (OER) or a hydrogen evolution reaction (HER).
The method of claim 1,
The composite is an electrocatalyst of an oxygen evolution reaction (OER) or a hydrogen evolution reaction (HER) with an average pore size of 1 to 10 nm.
Forming a reaction intermediate by performing a hydrothermal reaction of a mixture containing glucose, boronic acid, and graphene oxide; And
Performing a reduction reaction of the formed reaction intermediate to prepare a composite including a graphene hydrogel in which boron-doped carbon quantum dots are dispersed on a surface;
A method of producing an electrocatalyst of an oxygen generation reaction (OER) or a hydrogen generation reaction (HER) comprising a.
The method of claim 9,
The content of boronic acid is 1 part by weight to 15 parts by weight based on 100 parts by weight of glucose.
The method of claim 9,
The amount of glucose is 50 parts by weight to 100 parts by weight based on 100 parts by weight of graphene oxide. A method of preparing an electrocatalyst for an oxygen generation reaction (OER) or a hydrogen generation reaction (HER).
The method of claim 9,
Hydrothermal reaction is a method of producing an electrocatalyst of an oxygen generating reaction (OER) or a hydrogen generating reaction (HER) performed for 10 to 30 hours at a temperature of 150°C to 200°C.
The method of claim 9,
The reduction reaction of the reaction intermediate is an oxygen evolution reaction (OER) performed using at least one reducing agent selected from the group consisting of ascorbic acid, hydrogen iodide (HI), hydrogen bromide (HBr), and hydrogen chloride (HCl). Or a method for producing an electrocatalyst for hydrogen generation reaction (HER).
delete

Images