KR20140046662A - Fabrication method of mixed metal oxide electrode for alkaline water electrolysis system - Google Patents

Abstract

The present invention relates to a manufacturing method of a mixed metal oxide electrode, which comprises a step of preparing an electrode substrate, a step of manufacturing a coating solution by mixing iridium (Ir) chloride, ruthenium (Ru) chloride and tantalum (Ta) chloride with organic solvent, and a step of applying and heat-treating the coating solution on the substrate; and a mixed metal oxide electrode manufactured thereby. The mixed metal oxide electrode according to the present invention can be used as an anode electrode for alkaline electrolysis helpfully by having excellent electrochemical properties due to addition of safety against electrochemical reaction and stability against alkali through tantalum (Ta) oxide, as well as having excellent catalytic function of ruthenium (Ru) oxide and iridium (Ir) oxide under an oxygen generation reacting condition in the strong alkali condition.

Description

TECHNICAL FIELD [0001] The present invention relates to a mixed metal oxide electrode for alkaline water electrolysis,

The present invention relates to a method for producing a metal mixed oxide electrode comprising ruthenium (Ru), iridium (Ir) and tantalum (Ta) oxides, and a metal mixed oxide electrode produced by the method.

In recent years, due to the increase in carbon dioxide emissions due to fossil fuel consumption and the rapid change of crude oil prices, there has been a move toward a society that uses petroleum and coal as its main energy source and is oriented toward environmentally friendly energy. When hydrogen is used as a fuel among these energy sources, the pollution problem of present fossil energy can be solved because no pollutant is generated except a very small amount of NOx in combustion.

Hydrogen is produced from non-fossil fuels by far the most well known and most practiced technology is water electrolysis. Water electrolysis is the simplest but highly reliable, mass-producible and highly pure hydrogen. Currently, DSA (Dimensional Stable Anode) electrodes, which are low in overvoltage necessary for water decomposition and low in cost per unit area, are mainly used as water decomposition anode electrodes, and nickel metal materials are utilized as cathode electrodes.

The reaction formula in the alkaline water electrolysis system is as shown in Scheme 1.

<Reaction Scheme 1>

O₂ + H₂O + 2e^- Anode (anode): 2OH ^- ↔

O ₂ + H ₂ O + 2e ^-

Reduction pole (cathode): 2H + 2e ^- ? H ₂

O₂ V = 1.23 V (vs. RHE)
Overall reaction: H₂O → H₂ +

O₂ V = 1.23 V (vs. RHE)

In the alkaline water electrolytic system, the electrode material of the anode performs functions such as reduction of the overvoltage of the battery, stability of the system and increase of efficiency. However, in the case of a system using a DSA electrode that is currently in commercial use, the over-voltage is high in terms of energy efficiency. To overcome these disadvantages, development of low overvoltage, high efficiency DSA electrodes is one of the important factors.

More specifically, in the case of the anode electrode of the alkaline aqueous electrolysis, the stability of the electrode is deteriorated due to the change of oxidation of the metal material constituting the oxide in the electrolysis reaction, and finally chemical change of the electrode constituting material occurs. In order to overcome this problem, when a certain proportion of iridium (Ir) oxide is mixed with ruthenium (Ru) oxide, which is the highest performance substance in the oxygen generating reaction, not only the stability is enhanced but also the activity is increased . In addition, the addition of a transition metal oxide containing enough electrons that can be shared facilitates sufficient electron transfer between the mixed oxides, thereby contributing to the reaction (see, eg, N. Mamaca, Applied Catalysis B: Environmental 111-112 (2012) 376-380) The stability of ruthenium (Ru) oxide and iridium (Ir) oxide can be further increased.

On the other hand, tantalum (Ta) is widely used as a battery material in the electronics industry and can form a highly efficient dielectric oxide layer. In addition, it has been widely used for surgical surgical parts and the like because of its excellent corrosion resistance and chemical resistance without reacting to human body fluids.

Accordingly, the present invention is to provide a metal mixed oxide electrode for an alkali electrolytic anode having low overvoltage and high efficiency, which is prepared by adding a transition metal suitable for ruthenium (Ru) oxide and iridium (Ir) .

In order to solve the above problems,

Preparing an electrode substrate; Preparing a coating solution by mixing ruthenium (Ru) chloride, iridium (Ir) chloride, and tantalum (Ta) chloride with an organic solvent; And coating and heat-treating the coating liquid on a substrate, and a metal mixed oxide electrode produced by the method.

The metal mixed oxide electrode according to the present invention not only has excellent catalytic performance of ruthenium (Ru) oxide and iridium (Ir) oxide in the oxygen generating reaction condition under strong base conditions, but also has stability against alkali by tantalum (Ta) And exhibits excellent electrochemical characteristics due to the addition of stability due to chemical reaction. Therefore, it can be usefully used as an anode for alkaline water electrolysis.

1 is a graph of X-ray diffraction analysis results for Experimental Example 1. FIG. FIG. 1A shows experimental results for a comparative example including tin oxide, and FIG. 1B shows experimental results for an embodiment of the present invention including tantalum oxide.
2 is a graph of XPS results for Experimental Example 2.
3 is a photograph of a result of SEM analysis for Experimental Example 3. FIG. 3A is a photograph of a comparative example including tin oxide, and FIG. 3B is a photograph of an embodiment of the present invention including tantalum oxide. FIG.

The present invention provides a method of manufacturing a semiconductor device, comprising: preparing an electrode substrate; Preparing a coating solution by mixing ruthenium (Ru) chloride, iridium (Ir) chloride, and tantalum (Ta) chloride with an organic solvent; And coating and heat-treating the coating solution on a substrate.

The inventors of the present invention have been studying the related materials to improve the oxygen generating characteristics of the electrode for alkaline water electrolysis when an appropriate amount of tantalum (Ta) is added to ruthenium (Ru) oxide and iridium (Ir) (Ir) oxide and tantalum (Ta) oxide, which exhibit the best electrochemical characteristics, are optimized, and then the present invention is applied to Completed.

In the case of tantalum (Ta) oxide used in the present invention, since it has high stability to alkaline electrolytes and has a large number of external electrons that can be shared, it is possible to improve the activity and stability of the electrode when it is added to ruthenium (Ru) It is also economical because it is cheaper than ruthenium (Ru) and iridium (Ir).

In one embodiment of the present invention, the material of the electrode substrate may be a non-oxidizing material, a non-corrosive material, and an electrically conductive material. More specifically, it may be gold, platinum, or titanium. More specifically, Can be used.

In another embodiment of the present invention, the electrode substrate is made of titanium, and fine irregularities may be formed on the surface thereof.

More specifically, preparing a titanium substrate; And a step of immersing the substrate in an acid and heating and washing the substrate, fine irregularities can be formed on the surface of the substrate.

In one embodiment of the present invention, the acid may be hydrochloric acid and oxalic acid sequentially. More specifically, the substrate is immersed in an aqueous hydrochloric acid solution for 1 to 10 minutes to be heated. After washing, the substrate is immersed in oxalic acid aqueous solution for 15 to 30 minutes A step of immersing the substrate and heating it may be performed. As a result, the surface of the substrate is increased, and the interaction with the metal oxide precursor material can be facilitated during the coating process.

In another embodiment of the present invention, examples of the organic solvent for preparing the coating liquid include acetone, ethyl acetate, ether, chloroform, pentane, hexane, heptane, nonane, decane, benzene, toluene, xylene, The alcohol may be, and more specifically, isopropyl alcohol, but is not limited thereto.

In another embodiment of the present invention, the molar ratio of ruthenium (Ru), iridium (Ir), and tantalum (Ta) may be 1 :( 1.5-2.5) :( 1-2.5) Can be 1: (1.7-2.3): (1-2.5), 1: 2: (1-2.5), or 1: 2: 2.5.

The ruthenium (Ru), iridium (Ir) and tantalum (Ta) chlorides mixed in the molar ratio on the organic solvent are coated on the electrode substrate through a coating and heat treatment process.

In one embodiment of the present invention, the coating and heat treatment steps can be repeated 7 to 15 times, and the peeling of the coating layer can be prevented by repeating. If the number of coatings is more than 15 times, the oxide layer on the surface of the substrate becomes thicker, the electric conductivity may be lowered and a higher voltage may be required. If the number of coatings is less than 7 times, the coating layer is not sufficiently formed. It can be peeled off. More specifically, the ruthenium (Ru), and iridium (Ir) the weight sum of the metal of about 1mg / cm ² And the number of repetition times is adjusted.

In another embodiment of the present invention, the application can be carried out through spraying, and the heat treatment can be carried out at a temperature of 300 to 400 DEG C for 3 to 20 minutes or 5 to 15 minutes.

The spray coating is a technique of directly spraying the coating solution onto an electrode substrate through a nozzle having a small diameter by applying direct pressure by an airless spray method, which corresponds to a coating process capable of minimizing the rate at which the coating liquid is ejected from the substrate .

In another embodiment of the present invention, the step of sintering at a temperature of 400 to 500 DEG C for 30 to 100 minutes may be further performed after the repeated step of the application and heat treatment. The metal chloride may be replaced with an oxide through the sintering process.

The present invention also provides a metal mixed oxide electrode comprising ruthenium (Ru), iridium (Ir), and tantalum (Ta) in a molar ratio of 1: (1.5-2.5) :( 1-2.5) to provide. As can be seen from the following examples, the metal mixed oxide electrode has low overvoltage and high efficiency under the oxygen generating reaction condition under strong base conditions, and thus can be usefully used as an anode for alkaline water electrolysis.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the contents of the present invention, but the scope of the present invention is not limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

< Manufacturing example  1> Alkaline electrolytic solution Anode ( anode ) Preparation of electrode

Step 1: Ti  Substrate pretreatment

A round Ti substrate (r = 1.4 cm) to be used as an electrode was prepared. 1000 ml of distilled water was placed in a beaker, boiled to such an extent that bubbles were generated, and the Ti substrate prepared when boiling was sufficiently added was kept for 30 minutes. Add IPA (iso propanol) in a 1000 ml beaker, boil it thoroughly, and keep the Ti substrate washed for 30 minutes. In this process, IPA boils and removes organic particles that have not been removed by distilled water.

Then, 20 wt% hydrochloric acid and 10 wt% oxalic acid were added to the beaker, and the temperature was raised to such an extent that the bubbles were formed. The Ti substrate was immersed in 20 wt% hydrochloric acid and the chemical reaction was induced for 5 minutes. After washing with distilled water, The chemical reaction was induced by salic acid.

At this time, it can be confirmed that the hydrochloric acid is changed into light purple during the hydrochloric acid treatment, and it is confirmed that a small amount of metal on the surface is melted and the uneven surface is changed uniformly and roughly. It is also confirmed that oxalic acid turns brown after 20 minutes treatment with oxalic acid, which is caused by the phenomenon that the metal on the surface is changed into ions while the surface is etched. Since the surface of the Ti substrate is further roughened by the acid treatment to induce an increase in the surface area, it is possible to facilitate the interaction with the precursor material in the subsequent coating.

The acid-treated substrate was cleaned with distilled water and cleaned using an ultrasonic cleaner for 30 minutes. Finally, it was cleaned several times with distilled water and dried in a dryer at 80 ° C to prepare a pretreated Ti substrate.

Step 2: Preparation of precursor solution

0.519 g of RuCl ₃ ? XH ₂ O, 0.746 g of IrCl ₃ ? X H ₂ O, 0.896 g of TaCl ₅ and 0.876 g of SnCl ₄ ? 5H ₂ O were weighed into a 100 ml beaker, and 50 ml of IPA (iso-propanol) . As a comparative example, tin chloride (SnCl ₄ ? 5H ₂ O) was used instead of tantalum chloride.

The beaker was sealed in order to avoid loss of solution due to the volatility of IPA and mixed for 6 hours or more using a magnetic stirrer. Thereafter, the ratio of ruthenium (Ru) to iridium (Ir) is fixed at 1: 1 and 1: 2, and the molar ratio of tantalum (Ta) or tin (Sn) At 0.5 intervals. The volume of each mixed solution was adjusted to 10 ml, and since the molar concentration was equal to 0.05 M, the volumes of the respective solutions were mixed by the target molar ratio and mixed. For uniform mixing, ultrasonic agitation was used, and the mixture was stirred at 30 to 40 ° C for 1 hour.

The mixing ratios of the precursor solutions according to Examples and Comparative Examples of the present invention are shown in Table 1 below.

Electrode number Added element (mol,%) Coating count Coating amount (Oxide)
mg / cm ² Ru Ir Sn Ta One 100 0 0 0 10 1.25 to 1.35 2 0 100 0 0 10 1.1 to 1.2 3 50 50 0 0 10 1.05 to 1.15 4 33 67 0 0 10 1.00 ~ 1.10 5 40 40 0 20 10 1.55 to 1.65 6 33 33 0 33 10 1.90 to 2.00 7 28.5 28.5 0 43 10 2.30 ~ 2.40 8 25 25 0 50 10 2.70 ~ 2.80 9 28.5 43 0 14.5 10 1.35 to 1.45 10 25 50 0 25 10 1.60 to 1.70 11 22 44.5 0 33.5 10 1.80 to 1.90 12 20 40 0 40 10 2.05-2.15 13 18.2 36.4 0 45.4 10 2.30 ~ 2.40 14 16.7 33.3 0 50 10 2.50 to 2.60 15 28.5 43 14.5 0 10 1.35 to 1.45 16 25 50 25 0 10 1.50 to 1.60 17 22 44.5 33.5 0 10 1.65 to 1.75 18 20 40 40 0 10 1.80 to 1.90

Step 3: Heat treatment after spray coating on the substrate

The mixed metal precursor solution of step 2 was again ultrasonically stirred for 10 minutes before coating, and then the mixed solution was injected into an air gun and evenly sprayed on the pretreated Ti substrate of step 1 preheated to 80 ° C, Heat treatment was repeatedly performed at a temperature for 10 minutes. The total number of the coating is 10 times, wherein the diameter of 6.158cm ² was adjusted to a coating amount of the ruthenium (Ru), and iridium (Ir) agreed weight of the metal on a Ti plate such that the 1mg / cm ^2. After the completion of all the steps, the final sintering was performed at 450 ° C for 1 hour to replace the chloride with oxide, and the resultant was dried again at 80 ° C after air cooling to complete the final electrode production.

< Experimental Example  1> X-ray Diffraction analysis

In order to confirm the components of the metal mixed oxide electrode manufactured according to the above preparation example, the electrode was analyzed by using an X-ray diffractometer in 2? (25? 70) region, and the results are shown in FIG.

1A and 1B are electrode numbers 15, 16, 17 and 18 in Table 1,

1B is a graph of the electrode numbers 10, 11, 12, and 13 of Table 1 in the order from top to bottom.

Referring to FIG. 1, RuO ₂ and IrO ₂ peaks were observed at 2θ values of 28 °, 36 ° and 54 °, and TiO ₂ (Rutile) peaks at 2θ values of 41 ° and 55 °. In particular, referring to FIG. 1A, SnO ₂ peaks were observed at 2θ values of 39 °, 54 ° and 57.5 °. Referring to FIG. 1b, Ta ₂ O ₅ peaks were observed at 57.5 °. As a result, it was confirmed that the metal mixed oxide electrode was produced in Step 3 of Preparation Example 1.

< Experimental Example  2> XPS (X- ray photoelectron spectroscopy )analysis

In order to confirm the presence of Ta ₂ O ₅ among the components of the metal mixed oxide electrode prepared in the above production example, XPS analysis was further performed. The electrode 13 of the metal mixed oxide of Table 1 was analyzed by XPS and the results are shown in FIG. Referring to FIG. 2, there is a Ta4f peak within the binding energy range of 30 to 25 eV, which indicates that Ta ₂ O ₅ is present.

< Experimental Example  3> Scanning electron microscope analysis

The structure of the metal mixed oxide electrode was observed through a scanning electron microscope (S-4300SE) in order to observe the structure of the metal mixed oxide electrode manufactured in the above production example, and the result is shown in FIG.

As shown in FIG. 3, the surface of the metal mixed oxide electrode prepared in the above production example has a mud-crack shape and various types of nanoparticles are formed. On the other hand, in the case of the electrode No. 13 in Table 1 including tantalum in FIG. 3B, the size of the nanoparticles was more uniform than the electrode No. 15 in Table 1 including the tin in FIG.

< Experimental Example  4> Characterization of oxygen generation reaction

One. LSV  analysis

In order to evaluate the characteristics of the electrode formed in the above production example according to the oxygen generation reaction, an electrode was installed in a compression cell, and a three-electrode system including the electrode was constructed and then a linear sweep voltammetry (LSV) was measured.

1M KOH was used as the electrolyte to measure the oxygen generation reaction characteristics under the strong base condition, and the reference electrode was a silver chloride electrode and the counter electrode was a platinum wire. The LSV has a scanning speed of 1 mV / sec and a range of -1V to 2V. At this time, the electrode over-voltage in each of ^{100mA / cm 2, 200mA / cm} 2, 300mA / cm 2 was measured to compare the voltage levels. Analysis data for each experimental electrode according to Table 1 is shown in Table 2 below.

2. EIS  analysis

Electrochemical Impedance spectroscopy (EIS) was measured through the same electrochemical system configuration as the LSV analysis in order to evaluate the characteristics of the electrode formed in the above production example according to the oxygen generation reaction. At this time, EIS was performed by a constant voltage method based on 0.6 V at which sufficient oxygen generation reaction occurred, and R _ct (charge transfer resistance) is shown in Table 2 below.

Electrode number Added element (mol,%) Experimental Example 4-1 Experimental Example 4-2 Ru Ir Sn Ta Overvoltage (mV) R _ct (ohm)
CV I R _ct (ohm)
After CV 100
mA / cm ² 200
mA / cm ² 300
mA / cm ² One 100 0 0 0 0.583 0.865 1.111 1.127 1.778 2 0 100 0 0 0.621 0.827 1.006 2.510 2.698 3 50 50 0 0 0.535 0.721 0.876 0.573 1.389 4 33 67 0 0 0.54 0.721 0.872 0.540 1.314 5 40 40 0 20 0.514 0.679 0.843 1.174 1.027 6 33 33 0 33 0.494 0.676 0.826 1.486 0.761 7 28.5 28.5 0 43 0.475 0.644 0.818 1.043 0.635 8 25 25 0 50 0.477 0.638 0.798 0.637 0.678 9 28.6 57.1 0 14.3 0.540 0.704 0.859 1.032 1.172 10 25 50 0 25 0.482 0.650 0.804 0.868 0.560 11 22 44.5 0 33.5 0.472 0.634 0.779 1.234 0.321 12 20 40 0 40 0.460 0.628 0.758 0.896 0.424 13 18.2 36.4 0 45.4 0.440 0.620 0.780 1.222 0.472 14 16.7 33.3 0 50 0.486 0.672 0.837 1.143 0.610 15 28.6 57.1 14.3 0 0.545 0.739 0.904 1.138 1.347 16 25 50 25 0 0.547 0.751 0.915 1.208 1.472 17 22 44.5 33.5 0 0.578 0.767 0.936 1.322 1.563 18 20 40 40 0 0.588 0.786 0.962 1.368 1.910

Referring to Table 2, before and after the CV (before and after the oxygen evolution reaction) when adding to the electrode having the ratio of Ru: Ir = 1: 2 in the case of tin (electrode Nos. 15, 16, 17, The resistance values of all of the samples were increased.

Further, according to the activity data according to the result of Experimental Example 4, 100, 200, 300 mA / cm 2 (Electrode No. 4) in the case of Ru: Ir = 1: 2 in all cases.

On the other hand, in the case of tantalum, the activity was increased when added to the electrode having the ratio of Ru: Ir = 1: 2. In particular, the ratio of Ru: Ir: Ta = 1: 2: (1 to 2.5) (Electrode Nos. 10, 11, 12, and 13) were most effective

Therefore, when Ru and Ir are appropriately mixed and added with tin, the activity is lowered under the alkaline electrolytic condition, and when the tantalum is mixed, the activity is increased. Further, when the electrochemical reaction proceeds (cyclic voltammetry) , It was confirmed that the electrode containing tantalum was activated under the alkaline electrolytic condition due to the fact that the Rct was further increased and the tantalum had a lower Rct value.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that such detail is solved by the person skilled in the art without departing from the scope of the invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

Preparing an electrode substrate;
Preparing a coating solution by mixing ruthenium (Ru) chloride, iridium (Ir) chloride, and tantalum (Ta) chloride with an organic solvent; And
Method of manufacturing a metal mixed oxide electrode comprising the step of applying and coating the coating solution on a substrate. The method of claim 1,
Wherein the electrode substrate is made of titanium. The method of claim 1,
The step of preparing the electrode substrate
Preparing a titanium substrate; And
Immersing the substrate in an acid, and heating and then washing the substrate to form micro concavities and convexities on the surface of the substrate. The method of claim 1,
Wherein the organic solvent is isopropyl alcohol. The method of claim 1,
A method of manufacturing a metal mixed oxide electrode in which the molar ratio of ruthenium (Ru), iridium (Ir) and tantalum (Ta) in the preparation of the coating solution is 1: 1.5.5-2.5: 1-2.5. The method of claim 1,
Wherein the coating and heat treatment steps are repeated 7 to 15 times. The method of claim 1,
Wherein the application is carried out through spraying. The method of claim 1,
Wherein the heat treatment is performed at a temperature of 300 to 400 DEG C for 3 to 20 minutes. The method of claim 1,
After the step of application and heat treatment,
And sintering at a temperature of 400 to 500 DEG C for 30 to 100 minutes. A ruthenium (Ru), iridium (Ir) and tantalum (Ta) prepared by the method according to any one of claims 1 to 9, containing a molar ratio of 1: (1.5-2.5): (1-2.5). Metal mixed oxide electrode.

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