KR20060104578A - Electric cell for high and a method of preparing the same for the high temperature electrolysis - Google Patents

Abstract

Disclosed are an electrochemical cell having a cathode made of a nickel / yttrium stabilized zirconia alloy, a method for producing the same, and a hydrogen production apparatus for producing hydrogen by electrolyzing high temperature steam by the aforementioned electrochemical cell. . In the above-described electrochemical cell, the anode made of an alloy of nickel / itrium-stabilized zirconia has a fine particle size and significantly increases the electrical conductivity, and can produce hydrogen by electrolyzing steam without a separate reduction process by hydrogen.

Description

Electric cell for high and a method of preparing the same for the high temperature electrolysis}

1 is a side view schematically showing an electrochemical cell according to a preferred embodiment of the present invention.

Figure 2 is a SEM photograph showing the size and shape of the alloy of Ni / YSZ formed by dry milling and wet milling from Ni powder and YSZ powder, respectively.

3 is a schematic diagram illustrating a method of manufacturing an electrochemical cell according to a preferred embodiment of the present invention.

The present invention relates to a hydrogen generating device, and more particularly to an electrochemical cell for high temperature water electrolysis and a hydrogen producing device using the same.

Hydrogen is widely used in the chemical industry, such as petroleum desulfurization and ammonia production, and is also used as aerospace fuel, semiconductor gas, and fuel cell raw materials. Fossil fuels currently used as the main energy sources are subject to problems due to rising prices and exhaustion, and various environmental regulations due to emissions of air pollutants such as NOx, SOx and various dusts generated after use and global warming due to carbon dioxide. As an alternative, research on the production and production technology of hydrogen as an environmentally friendly energy source is being actively conducted.

The hydrogen is produced by steam reforming or partial oxidation using oil or natural gas, and hydrogen produced by these methods cannot be used in renewable energy systems. However, electrolysis of water using electrochemical cells is used as a permanent renewable energy system. Water decomposition at low temperatures requires a lot of energy, so it is not used much. Instead, electrolysis using high temperature steam is performed. This situation is being studied.

Hydrogen production at high temperature is increasingly important because it has the advantage of replacing about one third of the energy required for water decomposition with heat energy and lowering the manufacturing cost by using a rapid electrode reaction. In the hydrogen production method using a high temperature electrolysis of the tank manufacturing method, the configuration of the electrochemical cell is similar to the solid oxide fuel cells, the physical temperature at high temperature because the operating temperature is higher than 600 ℃ by high temperature steam. Research into an electrochemical cell having phosphorus stability and maintaining durability is underway.

The anode of the electrochemical cell for high temperature water electrolysis serves to generate oxygen by oxidizing oxygen anions (O 2-) generated in the electrolysis. Therefore, the anode should have stable electrical properties at high temperatures and have high electrical conductivity. It is a noble metal such as platinum or a perovskite type lanthanum straw having stability even at a high temperature of 800 ^° C. or higher. Lithium manganese (LaSrMnO3, LSM) or lanthanum calcium manganese (LaCaMnO3, LCM) is used as the material of the positive electrode.

The solid electrolyte of the electrochemical cell for high temperature water electrolysis serves to transfer oxygen anions generated at the cathode of the electrochemical cell to the anode. Therefore, it should be conductive to oxygen anion and should not have electrical conductivity, such as Yttrium stabilized Zirconia (YSZ), Bismuth Yttrium Oxide, Cerium Oxide dope metal oxides such as with Samarium, Strontium Cerate and the like.

The cathode material is particularly important since the cathode of the electrochemical cell for high temperature water electrolysis serves to separate oxygen ions from hydrogen by electrolysis from water. Therefore, it should have high oxygen ion conductivity and electron conductivity, and have stable properties against mixtures of water vapor and hydrogen. To date, most of the cathode materials are composite materials including nickel (Ni) or nickel (Ni). Alloys of Yttrium stabilized zirconia (hereinafter referred to as YSZ) (hereinafter referred to as Ni / YSZ) are mainly used.

However, when the Ni / YSZ alloy is used as a cathode in an apparatus for generating hydrogen by electrolysis of high temperature steam, the alloy of nickel oxide (NiO) and YSZ is not used as the cathode. After the hydrogen generation apparatus is configured using an electrochemical cell including a cathode, the NiO is reduced with hydrogen to form a cathode composed of Ni / YSZ. In this case, it is disadvantageous in terms of efficiency or economical efficiency and disadvantages in terms of electrical conductivity according to particle size since the hydrogen generation device is formed using a cathode composed of a Ni / YSZ alloy, and a separate reduction process is performed rather than generating hydrogen directly. .

It is therefore a first object of the present invention to provide an electrochemical cell for high temperature electrolysis.

It is a second object of the present invention to provide a method for producing the electrochemical cell.

In order to achieve the first object of the present invention described above, according to a preferred embodiment of the present invention, the average particle of the powder is 0.5 to 1.5 ㎛ by Ni, wet milling process of an anode made of platinum, an electrically conductive material An electrochemical cell comprising a cathode composed of Ni / YSZ having an amount of 40 to 60% by volume and YSZ, and including a solid electrolyte formed between the anode and the cathode is provided.

In order to achieve the second object of the present invention described above, according to a preferred embodiment of the present invention, YSZ is compression molded at high pressure and then sintered at high temperature to form a solid electrolyte body in the form of a disk. At this time, the compression molding is preferably from 10000 to 50000 psi, the temperature in the subsequent sintering is preferably 1350 to 1500 ℃.

After screen printing the slurry in the form of Ni / YSZ on one side of the solid electrolyte and dried at 40 to 100 ℃ conditions to form a negative electrode.

Thereafter, a method of manufacturing an electrochemical cell by screen printing a slurry-type platinum (pt) on a side opposite to one side of the solid electrolyte in which the negative electrode is formed and drying it at 40 to 100 ° C. forms an anode. Is provided.

Hereinafter, the electrochemical cell and its manufacturing method will be described in detail by dividing through the drawings and examples.

1. Electrochemical Cells

1 is a side view schematically showing an electrochemical cell according to a preferred embodiment of the present invention.

Referring to FIG. 1, the electrochemical cell includes a disk-shaped solid electrolyte 120 and a cathode 110 and a cathode 130 formed on both sides of the solid electrolyte 120, respectively. The anode 110 is made of platinum, an electrically conductive material, the cathode is made of Ni / YSZ, and the solid electrolyte 120 is made of YSZ.

In particular, the electrochemical cell according to the preferred embodiment of the present invention has a characteristic that the particle size is significantly improved and the electrical conductivity is increased in the negative electrode which serves to generate hydrogen in the high temperature steam decomposition process. In addition, it has the characteristic of directly producing hydrogen without the reduction process of NiO together with the above characteristics, the negative electrode will be described in detail through examples and comparative examples according to the formation method.

Example

After mixing 600 ml of Ni powder and 400 ml of YSZ, performing a wet milling process in an atmosphere in which alpha-terpineol and ethanol are provided, the wet milling process is carried out, and the resultant is molded in a vacuum state. The Ni / YSZ alloy was formed by sintering at 900 ° C. for 2 hours.

Comparative Example 1

600 ml of Ni powder and 400 ml of YSZ powder and stearic acid (CH ₃ (CH ₂ ) ₁₆ COOH) corresponding to 0.5% by weight of the mixed weight of the Ni powder and YSZ powder were subjected to a ball mill (Plaveraryette 5, Fritsch). Dry milling was then performed for about 24 hours to produce a Ni / YSZ alloy.

Comparative Example 2

Ni / YSZ alloy was prepared by wet milling a mixture of 400 ml of NiO powder and 600 ml of YSZ powder in the same manner as in Example 1, followed by hydrogen reduction in an atmosphere provided with hydrogen gas at 900 ° C.

Experimental Example 1

Particle size of the negative electrode made of Ni / YSZ) alloy formed according to the above-described Example and Comparative Example 1 was compared.

2A and 2B are SEM photographs for analyzing particles of the negative electrode according to the above-described Example and Comparative Example 1.

2A and 2B, FIG. 2A shows particles of a negative electrode formed by wet milling, and the size of the particles has an average of 0.5 to 1.5 μm. On the other hand, Figure 2b shows the particles of the negative electrode formed by dry milling, the size of the particles having an average of 7㎛. Therefore, it can be seen that the particle size of Ni / YSZ formed by wet milling according to an embodiment of the present invention is significantly smaller than that of particles formed by dry milling.

Experimental Example 2

The electrical conductivity of the negative electrode according to the above experimental example and Comparative Examples 1 and 2 was measured, and the results are shown in Table 1 below.

Way Electrical Conductivity (S˙cm ^-1 ) Example 1.0 x 10 ⁴ Comparative Example 1 (Dry) <10 ^-5 Comparative Example 2 (Wet, Reduced) 5 x 10 ²

Referring to Table 1 above, in the case of forming the negative electrode through wet milling according to the embodiment, it has a significantly improved characteristics in terms of electrical conductivity than dry milling according to Comparative Example 1, for the reason described in Experimental Example 1 As described above, in the case of wet milling, the exposed area is significantly increased as the particle size of the cathode becomes smaller. In addition, it can also be seen that the cathode formed by wet milling Ni directly according to the embodiment of the present invention is significantly improved in terms of electrical conductivity compared to the cathode reduced by wet milling NiO.

Experimental Example 3

In the formation of the negative electrode according to the embodiment, the electrical conductivity was measured according to the content of the nickel powder, the results are shown in Table 2.

Ni content (Vol.%) Electrical Conductivity (S˙cm ^-1 ) 40 2.5 x 10 ² 60 1.0 x 10 ⁴

Referring to Table 2, when the Ni content is lower than 40% by volume, the electrical conductivity of the negative electrode is too low, and when higher than 60% by volume, the coefficient of thermal expansion of the negative electrode containing nickel is a solid electrolyte to which the negative electrode is bonded. And a large difference with the thermal window coefficient of the positive electrode, and as a result, the bond between the negative electrode and the solid electrolyte is weakened, so that the negative electrode may be separated from the solid electrolyte at high temperature. The difference between the coefficients of thermal expansion occurs when the Ni content is greater than 60%, since the Ni content is smaller than the YSZ having a larger coefficient of thermal expansion.

The preferred nickel content is therefore 40 to 60% by volume.

2. Manufacturing Method of Electrochemical Cell

3 is a diagram showing an overall manufacturing process diagram of an electrochemical cell.

Referring to FIG. 3, first, the slurry YSZ constituting the electrolyte is pressurized under a condition of 70 to 300 psi (S100), and then the resultant by pressurization is pressurized in a fluid (S200). It will take the form of a disk. Preferred compression molding pressure is 10000 to 50000 psi. If the compression molding is not performed, the electrolyte in the form of a disk is bent during sintering. The disk-shaped electrolyte formed by compression molding becomes a solid electrolyte through high temperature sintering (S300). At this time, preferable temperature conditions in sintering are 1350-1500 degreeC, More preferably, it is 1400-1450 degreeC. If the temperature is lower than 1350 ℃, the density of the electrolyte is lowered to cause an increase in resistance, at 1450 ℃ the density of the electrolyte is close to the theoretical density.

Screen printing a Ni / YSZ alloy having an average particle size of 0.5 to 1.5㎛ formed according to the above-described embodiment on one side of the solid electrolyte (S400). This is dried to form a cathode of a solid state (S500). Preferred temperature conditions for the drying is 40 to 100 ℃, more preferably 55 to 65 ℃. When drying at a high temperature of more than 100 ℃ evaporation rate is too fast may cause the negative electrode to fall from the solid electrolyte. In addition, when the temperature is less than 40 ℃ evaporation rate is too low disadvantage in terms of productivity.

Platinum is screen printed on the opposite side of the solid electrolyte having the negative electrode formed thereon (S600). Thereafter, again by drying at a temperature of 40 to 100 ℃ to form a solid anode (S700), thereby completing the manufacturing process of the electrochemical cell.

The electrochemical cell according to the preferred embodiment of the present invention described above can be used without a separate reduction process for the negative electrode, and has an effect in that the electrical conductivity of the negative electrode is also improved.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. I can understand that you can.

Claims (6)

An anode comprising an electrically conductive material; A negative electrode including a nickel / yttrium stabilized zirconia (YSZ) alloy having a nickel content of 40 to 60 vol% and an average particle size of 0.5 to 1 μm; An electrochemical cell located between the positive electrode and the negative electrode and comprising an electrolyte made of a solid material conductive to oxygen anions. The electrochemical method of claim 1, wherein the anode is made of at least one material selected from the group consisting of platinum (pt), lanthanum strontium manganese (LaSrMnO ₃ ), and lanthanum calcium manganese (LaCaMnO ₃ ). Cell. The method of claim 1, wherein the electrolyte is Yttrium stabilized Zirconia, Bismuth Yttrium Oxide, Cerium Oxide dope with Samarium, Strontium An electrochemical cell comprising at least one material selected from the group consisting of Cerate. i) pressurizing the porous material conductive to the oxygen anion at 70 to 300 psi; Compression molding the result of the pressing at 10000 to 50000 psi; And Forming a solid electrolyte comprising sintering the resultant product by compression molding at 1350 to 1500 ° C; ii) Nickel / Yttrium Stabilized Zirconia (YSZ) alloys having a content of 40 to 60% by volume of nickel (Ni) and an average particle size of 0.5 to 1.5 [mu] m were screen-printed on one side on the solid electrolyte; forming a cathode including screen printing) and drying the screen printed nickel / yttrium stabilized zirconia (YSZ) alloy at 40 to 100 ° C .; And iii) screen printing an electrically conductive material on the opposite side of one side of the solid electrolyte having the negative electrode formed thereon, and drying the screen printed electrically conductive material at 40 to 100 ° C. Method of producing an electrochemical cell comprising the step of forming. The method of claim 4, wherein the solid electrolyte is Yttrium stabilized Zirconia, Bismuth Yttrium Oxide, Cerium Oxide dope with Samarium, Strontium cerate Method for producing an electrochemical cell, characterized in that consisting of at least one material selected from the group consisting of (Strontium Cerate). The method of claim 4, wherein the anode is made of at least one material selected from the group consisting of platinum (pt), lanthanum strontium manganese (LaSrMnO ₃ ), and lanthanum calcium manganese (LaCaMnO ₃ ). Method for producing an electrochemical cell.

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