KR20170086786A

KR20170086786A - Flower shape palladium decorated CVD graphene using surface modification and electrodeposition for hydrogen sensor

Info

Publication number: KR20170086786A
Application number: KR1020160006219A
Authority: KR
Inventors: 장정식; 신동훈
Original assignee: 서울대학교산학협력단
Priority date: 2016-01-19
Filing date: 2016-01-19
Publication date: 2017-07-27

Abstract

The present invention relates to the application of the present invention to a hydrogen gas sensor after manufacturing graphene with floral palladium introduced by using surface modification and electrolytic plating, and introducing a functional group to the graphene surface using a reforming solution The present invention also provides a method for producing graphene in which flower-shaped palladium is finally introduced by introducing flower-shaped palladium on the surface of graphene by electrolytic plating using the prepared reformed graphene as a working electrode, It shows high sensitivity and stability when used as a sensor material, suggesting possibility as a next generation hydrogen sensor material.
According to the present invention, it is possible to easily produce graphene in which palladium in a flower shape is introduced by simple and inexpensive surface modification and electrolytic plating. Furthermore, the graphene in which the palladium is introduced in the present invention is not limited to the kind and concentration of the reforming solution, and can be manufactured without restriction on the electrolytic plating time and temperature.

Description

[0001] The present invention relates to a hydrogen sensor employing graphene in which palladium is introduced into a flower shape using a surface modification and electrolytic plating method,

The present invention relates to the application of graphene with hydrogenated palladium to a hydrogen sensor fabricated by surface modification and electrolytic plating. Specifically, after introduction of an amine group on the surface through surface modification, a flower-shaped metal is introduced using an electrolytic plating method and utilized as a gas sensor.

According to the present invention, it is possible to easily produce graphene in which flower-shaped palladium is introduced by simple and inexpensive surface modification and electrolytic plating. The prepared graphene was introduced directly into the electrode after simple patterning, and exhibited remarkably improved sensitivity compared to conventional materials. The palladium-introduced graphene, which can be produced in the present invention, can be produced without limitation on the size of graphene.

Carbon nanofibers, carbon nanotubes, Fullerenes, and Graphene, which are based on carbon, are manufactured in various ways. Particularly, graphene can be manufactured in a large area and exhibits high physical and chemical properties as well as high conductivity, which is attracting high interest as a basic material for electronic circuits. In addition, graphene having a band gap of 0 can be used for chemical sensors and biosensors based on FETs (field effect transistors) by using an adjustable band cap by introducing atoms from the outside. There are Hummers method and CVD (Chemical Vapor Deposition) methods for manufacturing such graphene. The Humulus method can not be manufactured in a large area, and has a disadvantage that impurities are included and conductivity is low. Large-scale pattern growth of graphene films for stretchable transparent electrodes (hereinafter referred to as " large-scale pattern graphene ") on January 14, 2009, Nature, "(Nature < RTI ID = 0.0 > 07199). &Lt; / RTI > The single-layered graphene sheet produced by the chemical vapor deposition method showed excellent electrical properties and showed potential as a next generation alternative electronic material by transferring it to an electrode substrate (Application No. 10-2010-0068173). In particular, it has been widely used as a material for a flexible and transparent high-sensitive sensor electrode. However, the production of single-layer graphene by chemical vapor deposition is influenced by various variables such as the type of metal catalyst thin film, the amount of carbon source influx, graphene growth and termination time. Thus, the fabrication of single layer graphenes has been studied so far.

Hydrogen is an essential energy in electric power generation and environmentally friendly transportation, but it is an essential gas in industry. However, the hydrogen sensor has high sensitivity because it has high explosibility and flammability even if it has a volume ratio of 4% or more in the air. Generally, a hydrogen sensor using tin oxide meets such a demand, but has a limitation that the operating temperature must exceed 200 ° C., so hydrogen sensors at room temperature using Pd, Pt, and Ag have been studied. However, in order to introduce such a metal, a functional group should be introduced. Generally, a plasma treatment or a carboxyl group generated by moisture in the transfer process is used. In the case of plasma, the surface of the graphene is damaged by high energy, The method for introducing a new functional group should be studied.

Electrodeposition is a simple, low-cost process, and it is one of the most popular methods for surface coating because it can provide various substrates depending on the working electrode. Furthermore, it has the advantage of being able to provide a high surface area due to the flower shape produced by surface modification and to maintain high sensitivity.

Therefore, by manufacturing the graphene with the introduction of the flower-shaped palladium by using the above-described manufacturing method, a large surface area per unit area is secured and the possibility of the sensor having high sensitivity at room temperature is shown.

The present invention provides a method for introducing an amine group into the surface of graphene using surface modification to resolve the problems of the prior art, Of palladium is used as an electrode to confirm applicability to a hydrogen gas sensor.

It is an object of the present invention to provide an electrode of an improved hydrogen gas sensor using graphene introduced with palladium in a flower shape manufactured by the above method.

After many experiments and intensive studies, the present inventors have confirmed that it is possible to introduce flower-shaped palladium into graphene through surface modification and electrolytic plating, which are completely different from conventional methods. In addition, it has been confirmed that the present invention can exhibit remarkably improved performance compared to pure graphene in the application of the produced flower-shaped palladium-introduced graphene as a hydrogen gas sensor electrode, leading to the present invention.

The present invention provides a method for manufacturing a graphene in which a flower-shaped palladium is introduced through surface modification and electrolytic plating, and applying the same to a hydrogen sensor.

According to the present invention, the production of graphene with the introduction of flower-shaped palladium and the application of the graphene to a chemical sensor,

(A) preparing graphene from a carbon source by chemical vapor deposition using a metal film as a catalyst;

(B) removing the metal film of the produced graphene and transferring it to the flexible polymer substrate; And

(C) reforming the surface of the graphene transferred to the flexible polymer substrate to an amine group (-NH2) using a reforming solution; And

(D) supporting the surface of the reformed graphene in an electrolytic plating solution, and then introducing palladium in a flower shape by electrolytic plating; And

(E) using the produced flower-shaped palladium as a material for sensing hydrogen gas using graphene.

According to the present invention, a method of introducing a functional group into the surface of graphene using a reforming solution dispersed in methanol is a completely new method which has not been reported so far, and other materials can be easily introduced by using this.

In addition, electrolytic plating can be used to easily introduce the floral palladium onto the reformed graphene.

This makes it possible to manufacture sensor electrodes with high sensitivity and stability to hydrogen gas due to their high surface area.

FIG. 1 is an electron micrograph of a graphene having palladium introduced therein according to Example 13 of the present invention; FIG.
2 is a graph showing the X-ray photoelectron diffraction (XRD) measurement results of the graphene having the flower-shaped palladium introduced therein according to Example 18 of the present invention;
FIG. 3 is a graph illustrating the results of measurement of sensor performance for various concentrations of hydrogen gas using the palladium-introduced graphite particles of Example 19 of the present invention; FIG.
4 is a graph illustrating the results of measurement of the resistance change of the electrode according to the bending radius using the graphite palladium introduced in Example 19 of the present invention;
5 is a graph showing the results of measurement of sensor performance for hydrogen gas according to the bending radius using the graphite palladium introduced in Example 19 of the present invention.

Unless otherwise specified herein, numerical ranges such as temperature, content, size and the like refer to ranges within which the manufacturing method of the present invention can be optimized.

In step (A), a metal film serving as a catalyst capable of growing carbon in a vacuum tube is put into a vacuum tube, and then a temperature is raised and a carbon source is allowed to flow, thereby causing graphene to grow on the surface of the metal film.

The metal film used is not limited to copper, nickel, and cobalt, and other metals that can act as catalysts are also possible. Among them, aluminum (Al), germanium (Ge) and the like are preferable.

The thickness of the metal film to be used is not particularly limited, and in the present invention, it is preferably between 25 and 100 μm. When the thickness is less than 25 μm, it is difficult to control the metal film. When the thickness exceeds 100 μm, complete etching is difficult.

The carbon source to be used is not limited to methane, ethane, ethylene, acetylene, propylene, butane, butylene, butadiene, pentane and pentene, and may be cyclopentadiene, hexane, cyclohexane, ethanol, benzene, .

The temperature used in the chemical vapor deposition is preferably 800 to 1200 ° C. Below 800 ° C, no carbon atoms are produced uniformly, and above 1200 ° C, a special reinforced quartz frame is broken to hold the metal film.

In step (B), the PMMA polymer is coated on the graphene surface as a graphene protective film to remove the metal film of the produced graphene, and is floated in a metal etching solution. When the metal is removed, it is subjected to a cleaning process using distilled water and then transferred to a flexible polymer substrate.

The time for floating the metal etchant is not particularly limited, and is preferably 24 to 60 hours in the present invention. In less than 24 hours, the metal is not etched properly, and in over 60 hours the graphene is damaged.

The flexible polymer substrate to be used is not limited to PET, PEN, and PI. Flexible polymers such as polypropylene (PP), polyvinyl chloride (PVC), and polyethylene (PE)

In step (C), the surface of the prepared flexible graphene is supported on an aqueous reforming solution having an amine group as a functional group on the basis of an aromatic ring compound, and an amine group is introduced on the surface of the graphene due to the π-π interaction.

The type of the reforming solution used is not limited to 1,5-diaminonaphthalene or para-phenylenediamine, but may be 9,10-diaminophenanthrene having an amine group as a functional group based on an aromatic ring compound C14H12N2), benzylamine (C6H5CH2NH2), and the like are preferable.

The concentration of the reforming solution used is preferably 0.01 to 0.1 M. Below 0.01 M, the degree of modification is insignificant, and above 0.1 M, a large amount is deposited.

It is preferable that the time for carrying the solution in the reforming solution is between 10 and 30 minutes.

In step (D), based on an electrolyte solution containing a palladium precursor using sulfuric acid as a solvent using the above-described modified graphene working electrode, Ag / AgCl reference electrode and platinum (Pt) counter electrode to perform the electrolytic plating method A constant voltage is applied to conduct electrolytic plating.

The sulfuric acid concentration of the electrolyte solution used is preferably between 0.1 and 1 M. As the density increases from 0.1 M to 1 M, the density of the plated palladium changes. There is no change in the range above or below this range.

The palladium precursor of the electrolyte solution used is not limited to palladium acetate, palladium nitrate, and palladium chloride. Palladium acetylacetonate (Pd (C10H14O4)), palladium propionate (Pd (C6G10O4) .

The palladium precursor concentration of the electrolyte solution used is preferably between 0.1 and 1 M, and if it is less than 0.1 M, the palladium will not be plated properly and if it exceeds 1 M, excess plating will be released from the graphene surface.

The temperature used for the electrolytic plating process is preferably between 25 and 70 ° C. If the temperature is lower than 25 ° C, the reaction is not properly performed. If the temperature is higher than 70 ° C, excess plating is released from the graphene surface.

The time used for the electrolytic plating method is preferably between 1 and 10 minutes. If the time is less than 1 minute, the reaction is not properly performed. If the time exceeds 10 minutes, excess plating is caused to separate from the graphene surface.

In step (E), hydrogen gas is injected by concentration to measure the sensor performance of the manufactured electrode, and real-time resistance change is recorded. Further, to measure the performance according to the bending, the flexible graphene electrode is bent at an angle, and the change in resistance to hydrogen is recorded.

It is preferable that the concentration of the hydrogen gas is between 1 and 100 ppm when the sensor performance is measured using the manufactured flexible palladium-introduced flexible graphene.

It is preferable that the bending radius is in the range of 10 to 30 mm when measuring the sensor performance according to the bending using the manufactured flexible palladium-introduced flexible graphene.

[Example]

Hereinafter, specific examples of the present invention will be described with reference to examples, but the scope of the present invention is not limited thereto.

A chemical vapor deposition (CVD) process was performed on a 5 cm diameter quartz tube with a 3 μm × 3 cm 25 μm thick copper film. First, a vacuum of 10 mTorr or less is maintained for uniform gas inflow. In order to remove oxides and impurities on the surface of the copper film, hydrogen gas is maintained at a rate of 10 cc / min at 1000 ° C for 30 minutes Respectively. Then, methane (CH4) gas, which is a carbon source, was injected at a rate of 20 cc / min, maintained for 10 minutes, and cooled at a rate of 50 ° C / min to form graphene on the surface of the copper film.

The same method as in Example 1 was used, but a copper film having a thickness of 75 탆 was placed thereon, and a chemical vapor deposition process was performed. As a result, the same results as in Example 1 were obtained.

A nickel film was used in the same manner as in Example 1, and a chemical vapor deposition process was carried out. As a result, the same results as in Example 1 were obtained.

The same procedure as in Example 1 was used, but at 1100 ° C under an investigation gas to remove oxides and impurities on the surface of the copper film in a vacuum state. As a result, the same results as in Example 1 were obtained.

The same procedure as in Example 1 was used, but acetylene was injected as a carbon source. As a result, the same results as in Example 1 were obtained.

The graphene-formed copper film made by the method of Example 1 was coated on one surface with a PMMA solution to prevent damage to the graphene when copper was removed to produce a flexible graphene substrate. Thereafter, the substrate is floated in a copper etching solution, held for 36 hours, and then subjected to a cleaning process five times or more using distilled water. Finally, transition was made to the flexible PEN substrate.

The same method as in Example 6 was used, and the time for floating the copper etching solution was 48 hours. As a result, the same result as in Example 6 was obtained.

Using the same method as in Example 6, the floated graphene was transferred to a PET substrate. As a result, the same result as in Example 6 was obtained.

To modify the surface of the graphene, the flexible graphene substrate produced by the method of Example 6 was immersed in a 0.5 M aqueous solution of 1,5-diaminonaphthalene in which methanol was used as a solvent for 10 minutes, followed by washing with methanol.

The same procedure as in Example 9 was used, but with 0.5 M para-phenylenediamine. As a result, the same results as in Example 9 were obtained.

The same procedure as in Example 9 was used, but using an aqueous 0.01M solution of 1,5-diaminonaphthalene. As a result, the same results as in Example 9 were obtained.

The same method as in Example 9 was used, but the time for carrying the solution in the aqueous reforming solution was 20 minutes. As a result, the same results as in Example 9 were obtained.

In order to obtain flexible graphene in which flower-shaped palladium was introduced, graphene modified by the method of Example 9 was used as working electrode, Ag / AgCl reference electrode and platinum (Pt) counter electrode, and 0.5 M of palladium Electrolytic plating is carried out at a constant voltage of -0.1 V under an electrolyte solution containing acetate for 5 minutes at room temperature.

In Fig. 1, there is shown a photograph of a scanning electron microscope (SEM) of flexible graphene in which floral palladium is introduced by electrolytic plating in this embodiment.

The same procedure as in Example 13 was used, but using an electrolyte containing 0.5 M of palladium chloride. As a result, the same results as in Example 13 were obtained.

The same procedure as in Example 13 was used, but using an electrolyte containing 0.01 M palladium acetate. As a result, the same results as in Example 13 were obtained.

The same method as in Example 13 was used, but the temperature used in the electroplating method was 40 ° C. As a result, the same results as in Example 13 were obtained.

The same method as in Example 13 was used, but the reaction time in the electroplating method was 3 minutes. As a result, the same results as in Example 13 were obtained.

The X-ray diffraction analysis of the flexible graphene containing the flower-shaped palladium prepared in Example 13 showed that the graphitic carbon peak (24 °) due to the crystallinity of graphene It was confirmed that palladium was well formed through four peaks (FIG. 2).

In order to measure the sensor performance of flexible graphene with floral palladium, a 500 ml capacity reactor with a pressure of 100 torr was installed. 1, 20, 50 ppm hydrogen gas was injected, and the real time resistance change was recorded at a current of 10 -4 A. In addition, the change in resistance to hydrogen with the bending radius (30, 20, 10 mm) was recorded to measure the performance according to the bending.

In FIG. 3, the resistance change of the flexible graphene introduced with the flower-shaped palladium according to the concentration of hydrogen gas produced in the present embodiment has been proposed. It was confirmed that the sensor performance is shown even at a low concentration of 1 ppm. In FIGS. 4 and 5, measurement results of the change in resistance according to the bending radius and the sensor performance of the hydrogen gas are shown. It was confirmed that there is no significant decrease in resistance or performance even when the angle is changed.

Using the same method as in Example 18, 5, 10 ppm hydrogen gas was injected and recorded. As a result, the same results as in Example 18 were obtained.

Using the same method as in Example 18, the performance was measured at a bending radius of 15 and 25 mm. As a result, the same results as in Example 18 were obtained.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

none.

Claims

Preparing graphene from a carbon source by chemical vapor deposition using a metal film as a catalyst;
Removing the metal film of the graphene and transferring it to a flexible polymer substrate; And
Exposing the surface of the graphene transferred to the flexible polymer substrate to an amine group (-NH2) using a reforming solution; And
Supporting the surface of the reformed graphene in an electrolytic plating solution, and then introducing palladium in a flower shape by electrolytic plating; And
And using the produced graphite palladium as a material for sensing hydrogen gas using graphene.

The chemical sensor manufacturing method according to claim 1, wherein the metal film used as the catalyst is one of Cu (copper), Ni (nickel), and Co (cobalt).

The method of claim 1, wherein the carbon source used in the chemical vapor deposition method is any one of methane, ethane, ethylene, acetylene, propylene, butane, butylene, butadiene, pentane, and pentene.

The method of claim 1, wherein the temperature used during chemical vapor deposition using a metal film is between 800 and 1200 ° C.

The chemical sensor manufacturing method according to claim 1, wherein the flexible polymer substrate of the produced graphene is one of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and PI (polyimide).

The method of claim 1, wherein the graphene surface reforming solution is one selected from the group consisting of 1,5-diaminonaphthalene (C10H6 (NH2) 2) and para-phenylenediamine (C6H4 &Lt; / RTI >

The chemical sensor manufacturing method according to claim 1, wherein methanol is a solvent for preparing the graphene surface nitriding solution.

The chemical sensor manufacturing method according to claim 1, wherein the concentration of the graphene surface nitriding solution is in the range of 0.01 to 0.1 M.

The method of claim 1, wherein the palladium precursor in the preparation of the electrolytic plating solution is any one of palladium acetate (Pd (OCOCH3) 2), palladium nitrate (Pd (NO3) 2), and palladium chloride Sensor manufacturing method.

The chemical sensor manufacturing method according to claim 1, wherein sulfuric acid is used as a solvent in preparing the electrolytic plating solution.

The method of claim 1, wherein the temperature used in the electrolytic plating process is between 25 and 70 ° C.

The method of claim 1, wherein the time used for the electroplating is between 1 and 10 minutes.