KR101950367B1 - Apparatus for splitting water using zinc oxide and titanium oxide core/shell nanovires - Google Patents

Abstract

A water decomposition apparatus using zinc oxide / titanium oxide core shell nanowires is disclosed. The present invention relates to a water decomposition apparatus comprising a working electrode, a reference electrode, a counter electrode and an electrolyte to obtain a water decomposing effect, wherein the working electrode comprises a core-shell nanowire in which titanium oxide is coated on zinc oxide nanowire .

Description

FIELD OF THE INVENTION [0001] The present invention relates to a water-decomposing apparatus using zinc oxide / titanium oxide core shell nanowires,

The present invention relates to a water decomposition apparatus using zinc oxide / titanium oxide core shell nanowires, and more particularly, to a water decomposition apparatus using zinc oxide / titanium oxide core shell nanowires using a well-arranged zinc oxide- Lt; RTI ID = 0.0 > nanoparticles < / RTI > with zinc oxide / titanium oxide core shell nanowires.

In a rapidly developing modern society, environmental problems caused by excessive use of fossil fuels are emerging as serious problems. Sulfur oxides, nitrogen oxides, and carbon dioxide from fossil fuel fuels are devastating and are a major cause of pollution problems.

A representative material that can develop without causing environmental pollution is hydrogen. As a method for producing hydrogen, there is a typical electrolysis method, but the efficiency is low and electricity is supplied separately. Therefore, it is necessary to study the production method of high efficiency hydrogen using solar energy.

Since zinc oxide is a semiconductor material with a large bandgap and wide binding energy, it can be used in solar cells and photoelectrochemical cells. Especially well-ordered, high density and large surface area zinc oxide nanowires can be expected to be highly efficient in water decomposition using photoelectrochemical devices. Titanium oxide has a band gap region similar to zinc oxide, but differs in the durability and the absorbing optical wave length. Manufacture of zinc oxide-titanium oxide core shell nanowire, which is a form of zinc oxide nanowire coated with titanium oxide, can be expected to have higher efficiency than zinc oxide nanowire, and can drive the device more stably. Therefore, there is a need to develop and develop a method for manufacturing a zinc oxide-titanium oxide core shell nanowire-based photoelectrochemical cell having high efficiency and excellent durability to contribute to the development of hydrogen-free hydrogen production technology.

For example, in Non-Patent Document 1, zinc oxide nanowires were coated with silver nanoparticles to prepare zinc oxide-silver core-shell nanowires, and the water decomposition efficiency was measured. The higher efficiency is shown in Fig.

1. Korean Patent No. 10-0878742 (2009.01.08) 2. Korean Patent No. 10-0987468 (June 10, 2010)

 Wei, Yuefan, Lin Ke, Junhua Kong, Hong Liu, Zhihui Jiao, Xuehong Lu, Hejun Du, and Xiao Wei Sun. "Enhanced photoelectrochemical water-splitting effect with a bent ZnO nanorod photoanode decorated with Ag nanoparticles." Nanotechnology 23, no. 23 (2012): 235401.

It is an object of the present invention to provide a zinc oxide / zinc oxide / zinc oxide / zinc oxide / zinc oxide / zinc oxide / zinc oxide / zinc oxide core oxide nanowire, And to provide a water decomposition apparatus using titanium core shell nanowires.

In order to achieve the above objects, the present invention provides a water decomposition apparatus using zinc oxide / titanium oxide core shell nanowires,

A water decomposition apparatus comprising a working electrode, a reference electrode, a counter electrode and an electrolyte to obtain a water decomposition effect, wherein the working electrode comprises a core-shell nanowire having titanium oxide coated on zinc oxide nanowire.

The zinc oxide-titanium oxide core shell nanowire may be formed by,

Preparing a zinc oxide nanowire; Supplying a titanium oxide precursor to the zinc oxide nanowire; The titanium oxide precursor is pyrolyzed to produce titanium oxide vapor; And depositing titanium oxide vapor on the surface of the zinc oxide nanowire.

Wherein the zinc oxide nanowire manufacturing step comprises:

Forming a carbon catalyst layer on the silicon substrate; And depositing zinc oxide vapor on the carbon catalyst layer through a thermal chemical vapor deposition method to grow a plurality of zinc oxide nanowires in a direction perpendicular to the silicon substrate.

The step of forming the carbon catalyst layer may include:

Placing an alumina boat containing carbon powder and a silicon substrate in the interior of the ceramic tube; Flowing nitrogen gas as a transfer gas through a mass flow controller at a flow rate of 1 LPM (liter per minute), and heating the furnace temperature to 1,100 ° C or higher; And coating the carbon film on the silicon substrate through the carbon vapor generated from the carbon powder by the nitrogen gas as the transfer gas.

The step of growing the zinc oxide nanowire comprises:

Placing a silicon substrate coated with a carbon film and a zinc rod as a source material in an alumina boat and inside the ceramic tube; Flowing a mixed gas of argon and oxygen as a transfer gas through a mass flow controller at a flow rate of 0.4 to 1 LPM (liter per minute), and heating the furnace to a temperature of 550 to 750 캜; And growing the zinc oxide nanowire on the silicon substrate by the zinc vapor generated from the zinc bar meeting a mixed gas of argon and oxygen as the transfer gas.

The titanium oxide precursor is TTIP (Titanium tetra iso-propoxide).

And the diluent gas is supplied to the titanium oxide vapor so as to produce a titanium oxide layer on the surface of the zinc oxide nanowire.

In the vapor deposition step of the titanium oxide vapor,

And the thickness of the titanium oxide shell is thickened at a rate of 1 nm / min when the deposition time is controlled to 15 to 60 minutes.

The coated titanium oxide shell has a thickness of 1 to 15 nm.

As described above, according to the present invention, a zinc oxide-titanium oxide core shell nanowire is used unlike the conventional water decomposing apparatus, so that a photoelectrochemical cell having high efficiency and high durability can be manufactured have.

By adjusting the thickness of the titanium oxide shell, the water degradation efficiency of the zinc oxide-titanium oxide core shell nanowire is changed. By utilizing the zinc oxide-titanium oxide core shell nanowires having the shell thickness of the most efficient efficiency, Lt; RTI ID = 0.0 > photochemical < / RTI >

The thickness of the titanium oxide shell can be easily controlled by adjusting the time for coating the titanium oxide shell to 15 to 60 minutes, thereby enabling the manufacture of a photoelectrochemical cell utilizing the high-efficiency zinc oxide-titanium oxide core-shell nanowire .

1 is a schematic diagram of a photoelectrochemical cell utilizing zinc oxide-titanium oxide core shell nanowires according to the present invention
2 is a schematic diagram of a zinc oxide-titanium oxide core shell nanowire well-arranged in the apparatus of FIG.
3 is a graph showing the photocurrent density when the titanium oxide thickness varies from 0 to 45 nm in a photoelectrochemical cell utilizing a well-ordered zinc oxide-titanium oxide core shell nanowire according to the present invention.
4 is a graph illustrating the photoelectrochemical cell efficiency when the titanium oxide thickness varies from 0 to 45 nm in a photoelectrochemical cell utilizing a well-ordered zinc oxide-titanium oxide core shell nanowire according to the present invention.
5 is a schematic diagram of an apparatus for manufacturing zinc oxide nanowires in the present invention.
FIG. 6 is a schematic diagram illustrating coating a carbon film on a substrate in the apparatus of FIG. 5; FIG.
Figure 7 illustrates the fabrication of well-ordered zinc oxide nanowires on a silicon substrate coated with a carbon film in the apparatus of Figure 5;
Figure 8 is a schematic view of a tube furnace system for making zinc oxide-titanium oxide core shell nanowires according to the present invention.

Hereinafter, a water decomposition apparatus using zinc oxide / titanium oxide core shell nanowires according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a photoelectrochemical cell utilizing a zinc oxide-titanium oxide core shell nanowire according to the present invention, and FIG. 2 is a schematic diagram of a zinc oxide-titanium oxide core shell nanowire well-arranged in the apparatus of FIG.

1, the water decomposition apparatus according to the present invention is an electrochemical cell comprising a working electrode 101 composed of a zinc oxide-titanium oxide core shell nanowire, a reference electrode 102 composed of a silver / silver chloride electrode, A counter electrode 103 made of a platinum electrode, and an electrolyte 107 made of a 0.5M sodium sulfate aqueous solution.

The reference electrode serves as a reference of potential and can recognize the potential of the working electrode. The counter electrode acts as a cathode and allows a current to flow to the electrochemical cell.

In addition, a computer 105 for processing the potable pot 104 and the measured current and voltage data may be separately installed to measure the generated current.

A solar light generator 106 may be installed for photocurrent measurement, and the solar light generator 106 generates light of AM 1.5 G, 100 mW / cm 2 through a xenon lamp. When the sunlight is emitted from the solar light generator 106, the electrons of the semiconductor material are energized to be divided into electrons and holes, and the divided holes combine with oxygen ions to produce oxygen gas. The oxidation reactions taking place in the following are as follows.

In the water decomposition apparatus according to the present invention, the electrons generated in the working electrode 101 are combined with the electrons moved to the counter electrode 103 and the hydrogen ions generated in the working electrode 101, and the following reduction reaction occurs.

Through this reaction, hydrogen gas can be obtained, and captured hydrogen gas can be used as an energy source in various fields.

The voltage and the photocurrent are measured in the computer 105 while the photovoltaic cell is irradiated with sunlight, and the water decomposition efficiency can be measured using the photocurrent value according to the voltage value as follows.

η is water decomposition efficiency, J is photocurrent density, and I _light is solar energy.

V _RHE can be calculated from the following equation.

V _{Ag / AgCl} is the measured voltage value, pH is the acidity of the electrolyte (107), V ⁰ _{Ag / AgCl} Is the reference voltage value of the reference electrode (0.1976 V). When the water decomposition efficiency calculated by this equation is compared, it is confirmed that the efficiency varies depending on the thickness of the titanium oxide cell.

2 is an enlarged view of a zinc oxide-titanium oxide core shell nanowire used as the working electrode 101 in the present invention.

2, a zinc oxide 112 nanowire grows on the substrate 113 and is coated with a titanium oxide shell on the surface of the zinc oxide 112 nanowire, thereby being applicable as the working electrode 101.

FIG. 3 shows the photocurrent density when the titanium oxide thickness varies from 0 to 45 nm in a photoelectrochemical cell utilizing well-ordered zinc oxide-titanium oxide core cell nanowires, and FIG. The photoelectrochemical cell efficiency when the titanium oxide thickness varies from 0 to 45 nm in a photoelectrochemical cell utilizing titanium oxide core cell nanowires.

As a result of the experiment according to the present invention, the water decomposition efficiency of the zinc oxide nanowire is 0.2%, but when the thickness of the titanium oxide shell is increased to 15 nm, the water decomposition efficiency increases to 0.55% It was found that the water degradation efficiency decreased to 0.1% when thickened.

Therefore, preferably, when the thickness of the titanium oxide shell is 1 to 15 nm, the water decomposition efficiency is the most excellent.

Hereinafter, the manufacturing process of the zinc oxide-titanium oxide core shell nanowire, which is a working electrode used in the present invention, will be described in more detail.

A first step of coating a carbon film on a silicon substrate in a device according to the present invention is carried out and a second step of growing a zinc oxide nanowire well arranged on a silicon substrate coated with a carbon film serving as a catalyst is carried out . In the present invention, by executing the first step and the second step in one system, the process can be simplified and the cost can be greatly reduced.

<First Step>

The alumina boat 10 containing the carbon powder 11 and the silicon substrate 13 is placed inside the ceramic tube 3 as shown in Figs. The carbon powder 11 serves as a source material for depositing a carbon film on the silicon substrate 13. [

Thereafter, nitrogen gas as a transfer gas is flowed through the mass flow controller 1 at a flow rate of 1 LPM (liter per minute: retention time 184 ms), and the temperature of the furnace 4 is heated to 1,100 ° C. or higher.

Then, nitrogen gas as a transfer gas is transferred to the carbon powder 11 and the silicon substrate 13, carbon steam is generated from the carbon powder 11 due to the high temperature inside the ceramic tube 3, The carbon film is uniformly coated on the silicon substrate 13.

&Lt; Second Step &

In order to obtain a well-ordered zinc oxide nanowire, the silicon substrate 23 coated with the carbon film and the zinc bar 21 as a source material are placed in the alumina boat 10 and placed inside the ceramic tube 3 .

A mixed gas of argon and oxygen as a transfer gas is flowed through the mass flow controller 1 at a flow rate of 0.6 LPM (liter per minute: retention time 307 ms), and the temperature of the furnace 4 is heated to 700 ° C or higher do.

The zinc bar 21 then creates a zinc vapor at high temperature which is in contact with a gas mixture of argon and oxygen, which is a transport gas, to grow zinc oxide nanowires on the silicon substrate 23.

In the present invention, the zinc oxide nanowire uses a chemical vapor deposition method. The chemical vapor deposition method can be manufactured in a short time of about 30 seconds by being manufactured in air.

In addition, the chemical vapor deposition method of the present invention can be expected to simplify the process and reduce the cost by using the same device for providing the catalyst and manufacturing the zinc oxide nanowire.

In the chemical vapor deposition method, the diameter, length, and density of the zinc oxide nanowire can be controlled by adjusting the temperature at the time of manufacturing to 550 to 750 캜.

When the temperature is increased from 550 ° C. to 50 ° C. in the chemical vapor deposition method, the shape gradually changes from zinc oxide nanoparticles having a size of 100 nm to zinc oxide nanowire arrays having a high density. Through this, zinc oxide nanowires can be formed on the silicon substrate coated with the carbon film.

That is, when the temperature in the ceramic tube is 550 ° C or less, there is a problem that zinc oxide nanowires are not formed. When the temperature is higher than 750 ° C, zinc oxide nanowires are not produced efficiently.

Also, the arrangement and density of the zinc oxide nanowires can be controlled by adjusting the flow rate of the gas mixture of argon and oxygen, which is a transfer gas, to 0.4 to 1 LPM. That is, when the flow rate of the transfer gas is adjusted to 0.4 to 1 LPM, the residence time of the zinc oxide vapor staying in the ceramic tube can be controlled.

In the present invention, when the flow rates of the transfer gas are set to 0.4, 0.5, 0.6, 0.7 and 1 LPM, the residence times are respectively 461, 369, 307, 263 and 184 ms. , But the arrangement was disorganized.

That is, when the flow rate of the transfer gas is 0.4 LPM or less, it is difficult to form the zinc oxide nanowire, and when the flow rate is 1 LPM or more, the arrangement of the nanowires is disturbed.

Referring to FIG. 8, the present invention includes a mass flow controller 51 and a control box 52 for controlling the flow rate of the transfer gas, which is an inert gas. When the flow rate of the transfer gas to be used in the control box is set, the mass flow controller 51 controls the flow rate of the transfer gas by applying an electrical signal.

A bubbler 53 is provided at the rear end of the mass flow controller 51 so that the transfer gas controlled by the mass flow controller 51 is supplied to the bubbler 53. The bubbler 53 is filled with TTIP (titanium tetraisopropoxide) as a source material.

The bubbler 53 is connected to the core tube 56 at a rear side thereof and a heating system 55 is installed outside the tube connecting the bubbler 53 and the core tube 56.

The heating system 55 is intended to prevent condensation when the TTIP is transported with the transfer gas. At this time, the temperature of the heating system 55 is preferably about 60 ° C.

In addition, a supply tube for supplying a dilution gas is configured to be combined with a tube for supplying TTIP from the bubbler 53 to the inlet side of the core tube 56, so that the TTIP and the diluting gas are supplied to the core tube 56 ) To be mixed together. The diluent gas serves to lower the concentration of the TTIP vapor and to control the total TTIP flow rate finally supplied to the inside of the tube furnace. The diluent gas is supplied from the diluent gas supply unit 54.

At this time, it is preferable that a heating tape is mounted on the outer circumferential surface of the core tube 56 to prevent condensation when TTIP and diluent gas are mixed.

The transport gas, the diluting gas, and the TTIP mixed gas transferred from the core tube 56 to the ceramic tube 57 are heated to a high temperature to decompose TTIP to produce titanium oxide gas.

At this time, the apparatus for heating the ceramic tube 57 to a high temperature can raise the temperature to a predetermined temperature by the user by setting the temperature as the tube furnace 58.

<Third Step>

The zinc oxide nanowire substrate manufactured in the first step and the second step is placed in the ceramic tube 57 and the tube furnace 58 is set at 450 ° C. and then heated. After a predetermined time, the internal temperature of the ceramic tube 57 rises to 450 ° C.

Thereafter, the transferred gas is set to 0.5 liter per minute (LPM) through the mass flow controller 51 and transferred to the bubbler 53. TTIP is filled in the bubbler 53 and TTIP gas is discharged from the bubbler 53 together with the transfer gas when the transfer gas is supplied to the core tube 56 via the heating system 55 . At this time, the diluent gas supplied from the diluent gas supply unit 54 is also transferred to the core tube 56, and the TTIP gas and the dilution gas are mixed in the core tube 56. The diluent gas is preferably supplied at 6.45 LPM.

The TTIP and the diluted gas mixed in the core tube 56 are supplied to the inside of the ceramic tube 57 so that titanium oxide can be coated on the surface of the zinc oxide nanowire on the substrate to a certain thickness in shell form.

At this time, the thickness of the titanium oxide shell to be coated can be adjusted by adjusting the time for supplying TTIP.

Titanium oxide particles having a size of 1 to 2 nm are generated on the surface of the zinc oxide nanowire for 15 minutes after the TTIP is supplied, and coated at a rate of about 1 nm / min from 15 minutes later. When coated for about 30 minutes, 15 nm, for 1 hour, about 50 nm of titanium oxide coated zinc oxide-titanium oxide core shell nanowires can be obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

51: mass flow controller 52: control box
53: Bubbler 54: Dilution gas supply part
55: Heating system 56: Core tube
57: ceramic tube 58: tube furnace
101: working electrode 102: reference electrode
103: counter electrode 104:
105: computer 106: solar generator
107: electrolyte

Claims (9)

A water decomposition apparatus comprising a working electrode, a reference electrode, a counter electrode and an electrolyte to obtain a water decomposition effect,
Wherein the working electrode comprises a core-shell nanowire having zinc oxide nanowires coated with titanium oxide,
The zinc oxide-titanium oxide core shell nanowire may be formed by,
Preparing a zinc oxide nanowire; Supplying a titanium oxide precursor to the zinc oxide nanowire; The titanium oxide precursor is pyrolyzed to produce titanium oxide vapor; And depositing titanium oxide vapor on the surface of the zinc oxide nanowire,
Wherein the zinc oxide nanowire manufacturing step comprises:
Forming a carbon catalyst layer on the silicon substrate; And
Depositing a zinc oxide vapor on the carbon catalyst layer through a thermal chemical vapor deposition process to grow a plurality of zinc oxide nanowires in a direction perpendicular to the silicon substrate,
The step of forming the carbon catalyst layer may include:
Placing an alumina boat containing carbon powder and a silicon substrate in the interior of the ceramic tube;
Flowing nitrogen gas as a transfer gas through a mass flow controller at a flow rate of 1 LPM (liter per minute), and heating the furnace temperature to 1,100 ° C or higher; And
And coating a carbon film on the silicon substrate through the carbon vapor generated from the carbon nanotubes as a transfer gas. The water decomposition apparatus using the zinc oxide-titanium oxide core shell nanowire according to claim 1, delete delete delete The method according to claim 1,
The step of growing the zinc oxide nanowire comprises:
Placing a silicon substrate coated with a carbon film and a zinc rod as a source material in an alumina boat and inside the ceramic tube;
Flowing a mixed gas of argon and oxygen as a transfer gas through a mass flow controller at a flow rate of 0.4 to 1 LPM (liter per minute), and heating the furnace to a temperature of 550 to 750 캜; And
And a step of growing a zinc oxide nanowire on the silicon substrate by bringing the zinc vapor generated from the zinc bar into contact with a gas mixture of argon and oxygen as a transfer gas. Used water decomposition device. The method according to claim 1,
Wherein the titanium oxide precursor is TTIP (Titanium tetra iso propoxide). &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the diluent gas is supplied to the titanium oxide vapor to cause the titanium oxide vapor to form a titanium oxide layer on the surface of the zinc oxide nanowire. The method according to claim 1,
In the vapor deposition step of the titanium oxide vapor,
Wherein the thickness of the titanium oxide shell is increased at a rate of 1 nm / minute when the deposition time is adjusted to 15 to 60 minutes. The method according to claim 1,
Wherein the coated titanium oxide shell has a thickness of 1 to 15 nm. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;

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