KR101609947B1 - Preparing method of electrodes using a potential shock - Google Patents

Abstract

The present invention relates to a producing method of an electrode using an electric shock, comprising: a first step of forming a titanium oxide layer on a titanium substrate by anodizing the titanium substrate; and a second step of supporting the titanium substrate, in which the titanium oxide layer is formed, in an electrolyte, and penetrating an anion on the titanium oxide layer through the electric shock. Therefore, the producing method does not need a separate process coating a catalyst using a metal precursor in order to increase electrode activity, and can dope a metal anion on the titanium substrate by a one-pot process. An electrode, in which a metal anion is uniformly doped, has low onset potential, and shows very high efficiency in the oxygen reduction reaction.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method for producing a water-decomposable electrode, and more particularly, to a method for manufacturing an electrode through an electric shock.

The most widely used method for obtaining hydrogen which is an environmentally friendly energy source is to decompose methane, a natural gas, into steam at high temperature and high pressure (CH ₄ + H ₂ O → H ₂ + CO ₂ ). In this way, half of the global hydrogen production is produced, but at the same time, carbon dioxide is generated, which has a negative impact on global warming. Hydrogen production by electrolysis of water is ideal, but in order to generate hydrogen and oxygen gas by electrically decomposing water, theoretically an electrical energy of 1.23 V (vs. NHE) is needed and practically more energy than the theoretical value In the case of producing hydrogen by an electrolysis method, the oxygen generation reaction occurring in the anode is a major source of energy consumption because the overvoltage is considerably high. Various methods of electrode development studies are being conducted to minimize the energy consumption.

On the other hand, TiO ₂ can increase the efficiency of the electrode when various catalysts such as RuO ₂ , IrO ₂ , Au, and WO ₃ are doped or coated, and the non-noble metal catalyst such as WO ₃ , Ni, Even though it shows excellent effect on cost, it exhibits a tendency to be easy to corrode and exhibits relatively low efficiency. Thus, precious metals are still used as major dopants. TiO ₂ is used as a base material for DSA (dimensionally stable anode) electrode because of its excellent stability. However, since it shows high overvoltage by pure metal electrode, additional catalyst coating process is needed.

The TiO ₂ electrode coated or doped with RuO ₂ or IrO ₂ can be used as a DSA electrode in the water decomposition system and chlorine-alkali process. IrO ₂ increases the durability and RuO ₂ reduces the oxygen reduction reaction Thereby improving the electrocatalytic performance. Various methods such as electrochemical deposition, pyrolysis, anodic oxidation, sol-gel and polymer precursors have been studied for the DSA production, but the ruthenium oxide, which is a noble metal, is effectively doped into a semiconductor TiO ₂ nanotube by a one- There is no attempt to lower the overvoltage of the electrode.

Korean Patent Publication No. 2011-0059114

The present invention relates to a process for producing water for decomposing electrodes by adding an anion of a metal oxide to a titanium dioxide layer by uniformly doping an anion of a metal oxide in a one-pot process of a titanium oxide base material and by increasing the water decomposition efficiency of the electrode, And a method of manufacturing an electrode capable of lowering the temperature of the electrode.

In order to achieve the above object, the present invention provides a method of manufacturing a semiconductor device, comprising: (a) forming a titanium oxide layer on the titanium substrate by anodizing the titanium substrate (first step); And a step of supporting the titanium substrate having the titanium oxide layer formed thereon in an electrolytic solution and penetrating the titanium oxide layer through an electric shock (second step).

The anodic oxidation is performed by adding a 0.9 M to 1 M phosphoric acid (H ₃ PO ₄ ), 3.6 to 4 g sodium hydroxide (NaOH), and 0.5 wt% hydrogen fluoride (HF) to deionized water to prepare a mixed solution, The titanium substrate is supported on the mixed solution and can be carried out at 20 V for 3 to 4 hours.

The length of the titanium oxide layer may be 900 nanometers to 1 micron.

The electrolytic solution may include a metal oxide solution of 0.02 M to 0.002 M.

The solution of the metal oxide may be one in which a metal oxide selected from the group consisting of KRuO ₄ , NaRuO ₄ , and LiRuO ₄ is dissolved.

The electric shock may be performed at a voltage of 20 to 200 V for 5 seconds to 10 seconds.

The electric shock may dope the entirety of the titanium oxide layer formed with the titanium oxide barrier layer at the lower end of the titanium oxide layer.

According to the method for manufacturing an electrode through an electric shock according to the present invention, there is no need for a separate step of coating a catalyst using a metal precursor to increase the activity of the electrode, and a metal anion is doped into a titanium substrate by a one- can do. Electrodes uniformly doped with metal anions have a low onset potential when used as an oxygen generating electrode and exhibit very high efficiency in an oxygen reduction reaction.

1 is a schematic view of a method for manufacturing an electrode by electric shock according to an embodiment of the present invention.
2 is an SEM image of a titanium oxide layer after anodization of a titanium substrate according to an embodiment of the present invention.
3 is an FE-SEM image of a titanium oxide layer according to the method of manufacturing an electrode through an electric shock according to an embodiment of the present invention.
4 is an EDS analysis image of a titanium oxide layer by an electrode manufacturing method according to an embodiment of the present invention.
FIG. 5 is an XPS analysis graph of a titanium oxide layer by an electrode manufacturing method according to an embodiment of the present invention.
FIG. 6 is a graph illustrating efficiency as a water-decomposing electrode of an electrode manufactured by the method of manufacturing an electrode through an electric shock according to an embodiment of the present invention.
FIG. 7 is a graph showing the atomic content of an electrode manufactured by the method for manufacturing an electrode through an electric shock according to an embodiment of the present invention. FIG.

The present inventors investigated a method of increasing the water decomposition efficiency of titanium oxide used as a water decomposition electrode. An anodic oxidation of a titanium substrate was performed to form a titanium oxide layer, and ruthenium oxide (KRuO ₄ , NaRuO ₄ , LiRuO ₄ ) was uniformly penetrated into the titanium oxide layer, and thus the electrode was found to exhibit low overvoltage and high catalytic efficiency, thereby completing the present invention.

The present invention provides a method of manufacturing a semiconductor device, comprising: (a) forming a titanium oxide layer on the titanium substrate by anodizing the titanium substrate; And a step of supporting the titanium substrate having the titanium oxide layer formed thereon in an electrolytic solution and penetrating the titanium oxide layer through an electric shock (second step).

The titanium substrate may be a good base material for manufacturing the DSA electrode.

The anodic oxidation is performed by adding a 0.9 M to 1 M phosphoric acid (H ₃ PO ₄ ), 3.6 g to 4 g sodium hydroxide (NaOH), and 0.5 wt% hydrogen fluoride (HF) to deionized water to prepare a mixed solution, The titanium substrate is supported on the mixed solution and can be performed at 20 V for 3 to 4 hours.

When the above conditions are exceeded, it is difficult to uniformly form the titanium oxide layer, which is a nanotube, on the titanium substrate.

Also, when the above conditions are exceeded, the length of the nanotubes on the titanium substrate may be out of the range of 900 nm to 1 占 퐉. If the diameter of the nanotubes is smaller than the above-mentioned condition, metal anions described later may not uniformly penetrate.

The electrolytic solution may include a metal oxide solution of 0.02 M to 0.002 M.

The metal oxide may be characterized in that the metal oxide is dissolved in any one selected from the group consisting of KRuO ₄ , NaRuO ₄ , and LiRuO ₄ .

The metal oxide solution is dissociated to transfer metal anions, and the metal anion is preferably RuO ₄ ^- .

The metal anion can be effectively doped in a short time on the titanium substrate by electric shock, and other metal anions can not be efficiently doped.

The electric shock may be performed at a voltage of 20 to 200 V for 5 to 10 seconds.

Also, the electric shock can penetrate the entirety of the titanium oxide layer formed with the titanium dioxide barrier layer at the lower end portion, and the electric shock can generate a large amount of the metal anion flow.

A titanium oxide barrier layer may be formed at the lower end of the titanium oxide layer at a voltage greater than 100 V and no additional titanium oxide barrier layer is formed in the anodized titanium substrate at a voltage less than 80 V.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited by these examples.

≪ Example 1 > Electrode Fabrication

Titanium substrate (thickness 0.127 mm, purity 99.7%, 15 mm x 15 mm, Sigma-Aldrich) was ultrasonically washed with ethanol, acetone, and distilled water for 15 minutes and dried at 60 ° C for 15 minutes Respectively. The anodic oxidation was performed at 20 V for 4 hours using a DC power supply (source meter 2400, Keithley). Among the two electrodes, an electrochemical cell containing titanium was used as a working electrode, and a platinum mesh And used as a counter electrode. The electrolyte contained 1 M phosphoric acid (Aldrich), 1 M sodium hydroxide (Daejung, South Korea) and 0.5 wt.% Hydrofluoric acid (Aldrich).

And potassium perruthenate (KRuO ₄ , Sigma Aldrich) were used as a source of ruthenium used for the preparation of ruthenium-doped titanium oxide nanotubes as metal oxide solutions.

Titanium oxide (TiO ₂ ) nanotubes formed on a titanium substrate formed a titanium oxide layer.

A high-voltage electric shock was applied with a 0.002 M potassium ruthenate solution as an electrolytic solution on a tin oxide substrate formed with a titanium oxide layer at room temperature, and a high temperature annealing was performed in an air heating furnace at 450 ° C. for 1 hour to cure the titanium oxide layer (thermal-annealing).

≪ Experimental Example 1 > Properties of electrodes

1. Shape of electrode

The shape of the prepared electrode was confirmed using a field emission scanning electron microscope (FE-SEM, 4300S, Hitachi, Japan). The ruthenium ions were doped in the titanium oxide layer using an energy dispersive X-ray analyzer (EDX, 4300S, Hitachi, Japan). The chemical composition of the substrate surface and the depth profile of the nanotubes were prepared using X-ray photoelectron spectroscopy (XPS, VGESCALAB220i-XL spectrometer, Fisons) using Al-Kα as an X-ray source. Linear sweep voltammetry (LSV) was performed in a 1 M potassium hydroxide (KOH) solution at -0.5 V using a galvanostatic system (Autolab, PGSTAT302N, Netherlands) 0.0 > mV / s. ≪ / RTI >

1 is a schematic view of a method for manufacturing an electrode by electric shock according to an embodiment of the present invention.

2 is an SEM image of a titanium oxide layer after anodizing a titanium substrate according to an embodiment of the present invention.

Referring to the drawings, it was confirmed that the titanium oxide nanotubes were uniformly formed after the anodic oxidation.

3 is an FE-SEM image of a titanium oxide layer according to the method of manufacturing an electrode through an electric shock according to an embodiment of the present invention.

The shape of the titanium oxide layer did not change even after a high-voltage electric shock. Referring to FIG. 3 (d), when a voltage of 100 V or higher was applied, a titanium oxide barrier layer was further formed at the lower end of the titanium oxide layer. It was confirmed that the thickness of the barrier layer was greatly increased due to the formation of holes in the electric shock of 200 V. In the low voltage region (20 V to 80 V), a new oxide layer was formed at the lower portion of the titanium oxide nanotubes generated in the anodic oxidation It was not created.

4 is an EDS analysis image of a titanium oxide layer by an electrode manufacturing method according to an embodiment of the present invention.

The metal anions supplied from the metal oxide solution were permeated onto the titanium substrate to confirm that the ruthenium was uniformly doped into the titanium oxide layer.

KRuO ₄ contained in the metal oxide solution was easily dissociated into K ⁺ cation and RuO ₄ ^- anion, and a large amount of metal anion RuO ₄ ^- penetrated into the positively charged titanium oxide layer through electric shock.

The formation of the titanium oxide barrier layer can be explained as a non-porous oxide induced by anodic oxidation in a neutral electrolyte. The pH of the 0.002 M KRuO ₄ solution ranged from 8.2 to 8.4, and the high - voltage electric shock caused a larger amount of RuO ₄ ^- to penetrate into the titanium dioxide layer, forming a highly concentrated ruthenium - doped titanium oxide layer.

4 (d) shows the result of atomic mapping of the titanium oxide layer, and it was confirmed that ruthenium was uniformly doped into the entire nanotube.

FIG. 5 is an XPS analysis graph of a titanium oxide layer by an electrode manufacturing method according to an embodiment of the present invention.

Referring to the drawings, it was confirmed that no binding energy peak was associated with the ruthenium or ruthenium complex, and that ruthenium was doped not only at the top of the nanotubes but also at the bottom of the titanium oxide layer. After the electric shock, a peak due to the binding energy of Ru, RuO ₂ , and RuO ₃ was observed in the XPS analysis.

FIG. 5 (b) shows the atomic concentration according to the depth after the electric shock which makes the magnitude of the voltage different.

It was confirmed that the ruthenium penetrated into the titanium oxide layer through the electric shock at a high concentration, and the maximum concentration was less than 5%. The results are consistent with the EDX analysis.

2. Performance of the catalyst

The electrochemical catalytic performance of the electrode including the ruthenium - doped titanium oxide layer was measured to confirm its performance as a water - splitting electrode.

FIG. 6 is a graph illustrating efficiency as a water-decomposing electrode of an electrode manufactured by the method of manufacturing an electrode through an electric shock according to an embodiment of the present invention.

LSV was measured at a scanning rate of 20 mV / s in 1 M KOH solution.

The electrode subjected to the electric shock of 140 V exhibited the lowest starting potential among the plurality of electrodes manufactured with different voltages and exhibited the highest current density at the fixed potential. Therefore, the optimal electric shock condition to be used for the water decomposition electrode was confirmed.

The electrode subjected to an electric shock of 200 V contained the largest amount of ruthenium in the titanium oxide layer but failed to exhibit the catalyst performance which was the most for some reason.

First, as the voltage of the electric shock increases, the thickness of the titanium oxide barrier layer increases, and voids are formed in the electric shock of 200 V. The increase of the titanium oxide barrier layer at the bottom of the nanotubes tended to increase the potential of the oxygen reduction reaction. Therefore, the optimum electric impulse voltage was determined according to the discrepancy between the content of doped ruthenium determined by the applied voltage and the thickness of the titanium oxide barrier layer.

Secondly, ruthenium penetrated into the titanium oxide layer in the bonding state of Ru, RuO ₂ , and RuO ₃ .

FIG. 7 is a graph showing the atomic content of an electrode manufactured by the method for manufacturing an electrode through an electric shock according to an embodiment of the present invention. FIG.

Referring to the drawings, the effect of the electrochemical catalyst of the oxygen reduction reaction tends to increase when the permeated ruthenium predominates with RuO ₂ . A relatively higher amount of RuO ₂ was found in the taoatanium oxide layer after an electrical shock of 140 V. RuO ₄ ^{-, which} is a metal anion, tends not to penetrate into the titanium oxide layer due to the size of the metal anion when a low voltage electric shock is applied. However, when a high voltage electric shock having a sufficient electric field is performed, RuO ₃ Was very well formed. A large amount of RuO ₂ was formed at the intermediate potential of 140 V.

In the anodizing process of the first step, a titanium oxide layer containing nanotubes was formed on the titanium substrate. The titanium dioxide layer was formed of nanotubes. A titanium substrate on which a titanium oxide layer is formed by anodic oxidation is deposited on an electrolyte containing KRuO ₄ metal oxide and subjected to electric shock at 140 V for 10 seconds to form a titanium oxide layer in a state of Ru, RuO ₂ , and RuO ₃ , The layer was doped with ruthenium. As the voltage of the electric shock increases, the total amount of Ru, RuO ₂ , and RuO ₃ also increases, and the thickness of the titanium oxide barrier layer formed at the lower end of the nanotube increases. According to the LSV analysis, it was confirmed that the electrode efficiency was the highest when the electric shock of 140 V was performed.

It is also confirmed that the RuO ₂ state contained in the titanium oxide layer is the most suitable for increasing the efficiency of the water decomposition electrode.

While the invention has been described with reference to a limited number of embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (7)

Anodizing the titanium substrate to form a titanium oxide layer on the titanium substrate (first step); And
(A second step) of supporting the titanium substrate on which the titanium oxide layer is formed with an electrolyte and impregnating the titanium oxide layer with an anion through electric shock (second step)
The anodic oxidation is performed by adding a 0.9 to 1 M phosphoric acid (H ₃ PO ₄ ), 3.6 to 4 g sodium hydroxide (NaOH), and 0.5 wt% hydrogen fluoride (HF) to deionized water to prepare a mixed solution, A titanium substrate was supported on the solution and was performed at 20 V for 3 to 4 hours,
Wherein the electrolytic solution comprises a metal oxide solution dissolved in a metal oxide selected from the group consisting of KRuO ₄ , NaRuO ₄ , and LiRuO ₄ of 0.002 to 0.02 M. delete The method of claim 1, wherein the titanium oxide layer is formed of nanotubes having a length of 900 nm to 1 占 퐉. delete delete The method according to claim 1, wherein the electric shock is performed at a voltage of 20 to 200 V for 5 to 10 seconds. The method of claim 1, wherein the electric shock comprises doping an anion on the entirety of the titanium oxide layer having the titanium dioxide barrier layer formed on the lower end of the titanium oxide layer.

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