KR101064154B1 - Method of preparing cathode material for high temperature electrolysis - Google Patents

Abstract

Disclosed is a method for producing a cathode material for high temperature electrolysis for producing an electrode capable of improving electrical conductivity of an electrode material used as a cathode of a high temperature electrolytic cell, preventing coarsening of sintered particles, and maintaining a porosity. In such a manufacturing method, Ni powder and Cu powder are mixed with YSZ powder, terpineol is added and ball milling to form Ni / Cu / YSZ cermet, where the volume ratio of Ni powder, Cu powder and the YSZ powder is 10:50:40 to 50:10:40, the number of revolutions of the ball mill may be 200 to 500rpm, the ball milling time may be 24 to 60 hours, the Ni / Cu / YSZ cermet Particle size may be 0.5 to 4㎛.

High temperature hydroelectrolyte, cathode, ball mill, hydrogen

Description

METHODS OF PREPARING CATHODE MATERIAL FOR HIGH TEMPERATURE ELECTROLYSIS

The present invention relates to a method for producing a cathode material for high temperature hydrolysis, and more particularly, to a method for producing a cathode material for high temperature electrolysis used for hydrogen production by electrolysis of water.

Hydrogen is widely used in the chemical industry, such as petroleum desulfurization and ammonia production. Recently, hydrogen is also used as a raw material for fuels, aerospace, gas and fuel cells in the aerospace industry. Currently, fossil fuels, which are the main energy sources, have many problems such as emissions of air pollutants such as nitrogen oxides, sulfur oxides, and various dusts, and various environmental regulations that are strict due to global warming caused by carbon dioxide. Therefore, researches on the production and production technology of hydrogen as an environmentally friendly energy source to replace such fossil fuels are actively conducted.

Examples of methods for producing hydrogen include steam reforming or partial oxidation using oil or natural gas, but hydrogen produced by these methods cannot be used in renewable energy systems. There is this.

Thus, a method of producing hydrogen by electrolyzing water with a permanent renewable energy system has been studied. Hydrogen production by electrolysis of water can be classified into low temperature electrolysis and high temperature hydrolysis according to the operating temperature. In particular, the hydrogen production method using the high temperature electrolytic method has the advantage of replacing about 1/3 of the required energy with thermal energy and lowering the manufacturing cost by using the rapid electrode reaction, compared to the low temperature hydroelectrolyzing method. have.

Hydrogen production using high temperature hydrolysis is a reverse reaction of solid oxide fuel cells (SOFCs), and has similar advantages to the composition of solid oxide fuel cells. There is a need to develop an electrode material that can be manufactured in a stable form at a high temperature because it is a high temperature of more than ℃.

Ni / YSZ cermet is prepared by synthesizing Yttrium Stabilized Zirconia (YSZ), which is widely known as an electrode material for high temperature electrolytic and solid oxide fuel cells.

The method for producing Ni / YSZ cermet uses a high energy ball milling device to achieve mechanical alloying. In forming the Ni / YSZ cermet, the mixing ratio of the Ni powder and the YSZ powder is mixed at a volume ratio of about 2: 8 to 8: 2, and the ball milling process is performed by a wet milling process. In the ball milling process, Ni and YSZ powders are added to the container, and the solvent is terpineol and ethanol, and the process is performed at 150 to 500 rpm for 24 to 90 hours. The formation of the Ni / YSZ cermet is described in more detail in Application No. 10-2006-0026023 (filed March 22, 2006) and may be referred to this.

As described above, in the case of using Ni alone in the preparation of Ni / YSZ cermet electrode materials, the electrolytic reaction proceeds at high temperature while the electrolytic reaction of the particle coarsening phenomenon and the microstructure is changed from porous to low porosity structure. There is a problem in that the electrical conductivity and the catalyst function, which are important properties of the reaction, are degraded. The lowering of the electrical conductivity and the catalytic function increases the mass transfer of the electrochemical reaction and the resistance of the battery, resulting in a decrease in durability and electrolytic efficiency of the battery. Thus, such a phenomenon increases the maintenance cost and the hydrogen production cost of the receiving system, and thus there is a problem of increasing economic losses.

Therefore, there is an urgent need in the electrode manufacturing technology for technical supplementation to solve such problems.

The problem to be solved by the present invention is to improve the electrical conductivity of the electrode material used as the cathode of the high temperature electrolytic cell, to prevent the coarsening of the sintered particles and to prepare the electrode capable of maintaining the porosity It is to provide a manufacturing method.

Another problem to be solved by the present invention is to provide a method for producing a cathode material for high temperature electrolysis, which can prevent degradation of battery durability and electrolytic efficiency.

Another object of the present invention is to provide a method for producing a cathode material for high temperature electrolysis, which can lower the maintenance cost and the hydrogen production cost of the electrolytic system.

According to an aspect of the present invention, there is provided a method for producing a cathode material for high temperature electrolysis according to an aspect of the present invention, wherein Ni / Cu / YSZ is mixed by mixing Ni powder and Cu powder with YSZ powder, and then terpineol is added. Form a cermet.

Preferably, the volume ratio of the Ni powder, the Cu powder and the YSZ powder may range from 10:50:40 to 50:10:40, and the particle size of the Ni powder is about 3 μm or less, The particle size is about 10 μm or less, and the particle size of the YSZ powder is 220 nm.

Preferably, the rotation speed in the ball mill may be 200 to 500rpm.

Preferably, the time of the ball milling may be 12 hours to 60 hours.

Preferably, the particle size of the Ni / Cu / YSZ cermet may be 0.5 to 4 ㎛.

Preferably, the method of manufacturing the cathode material for high temperature water electrolysis may further include adding an antifoaming agent.

Preferably, the method for producing a high temperature electrolytic cathode material may further include adding a dispersant.

Preferably, the method for producing a cathode material for high temperature water electrolysis may further include adding a plasticizer.

Preferably, the antifoaming agent may be polyethylene glycol (PolyEthylene Glycol, PEG).

Preferably, the dispersant may be fish oil.

Preferably, the plasticizer may be glycerol (glycerol) or dibutyl phthalate (DiButyl Phthalate, DBP).

As described above, the present invention provides an improved method for producing a cathode material for high temperature electrolysis, thereby improving the electrical conductivity of the electrode material used as the cathode of the high temperature electrolytic cell, preventing coarsening of sintered particles, and maintaining porosity. It has the effect of being able to prevent the fall of durability of a battery, and electrolytic efficiency.

In addition, the present invention has an effect of lowering the maintenance cost and the hydrogen production cost of the electrolytic system by providing an improved method for producing a cathode material for high temperature electrolytic.

Hereinafter, with reference to the accompanying drawings will be described preferred embodiments of the present invention. The following description and the annexed drawings are intended to assist those of ordinary skill in the art to understand the present invention, and therefore, they should not be construed as limiting the scope of the present invention. will be.

The cathode material for hot water electrolysis according to an embodiment of the present invention is a high-energy ball milling solution after adding terpineol as a solvent to directly mix YSZ powder with Ni powder and Cu powder. mechanical alloying by ball milling) to produce Ni / Cu / YSZ cermets. The high energy ball milling refers to a process of manufacturing at 300 rpm or more using a planetary mill.

As the Ni powder used as the cathode material for high temperature water electrolysis, a powder having a particle size of about 3 μm or less and Cu powder of about 10 μm or less is used. As the YSZ powder, zirconium oxide (ZrO ₃ ) stabilized with about 8 mol% yttrium oxide (Y ₂ O ₃ ) having a particle size of 220 nm is used. The particle size of the prepared Ni / Cu / YSZ cermet is 0.5 to 4 ㎛.

In Ni / Cu / YSZ cermet formation, the Ni powder, Cu powder and YSZ powder may be in the range of about 50:10:40 (i.e. 5: 1: 4) to 10:50:40 (i.e. 1: 5: 4). It is carried out in a wet milling process by volume ratio. The particle size of the Ni powder used for forming the Ni / Cu / YSZ cermet is about 3 μm or less, the particle size of the Cu powder is about 10 μm or less, and the particle size of the YSZ powder is 220 nm.

The ball milling process is performed by milling for about 12 to about 60 hours using a planetary ball mill using terpineol as a solvent. The terpineol prevents agglomeration of Ni powder, Cu powder, and YSZ powder, which are raw materials added to the ball mill, and facilitates contact between the raw material and the ball.

It is preferable that the rotation speed at the time of ball milling is 200-500 rpm, More preferably, it is 400 rpm. The charge weight ratio of ball to powder is preferably about 15: 1. Wherein the powder comprises a Ni powder, a Cu powder and an YSZ powder as described above in a volume ratio of about 50:10:40 (ie 5: 1: 4) to 10:50:40 (ie 1: 5: 4). The particle size of the Ni powder used for forming the Ni / Cu / YSZ cermet is about 3 μm or less, the particle size of the Cu powder is about 10 μm or less, and the particle size of the YSZ powder is 220 nm. In addition, the container and the ball used in the ball milling process are made of zirconium oxide to prevent contamination of the Ni / Cu / YSZ cermet, the diameter of the ball is about 1mm.

The mechanical alloying process conditions for preparing Ni / Cu / YSZ cermet are shown in Table 1 below.

Additive Milling time Milling speed
Ni, Cu, YSZ, Terpineol

12 to 60 hours

400 rpm

In the manufacturing method of Ni / Cu / YSZ cermet, by directly mixing the Ni powder and YSZ powder during ball milling, the reduction process is unnecessary compared to the conventional Ni / YSZ manufacturing process.

In addition, by performing a wet milling process in which terpineol is added, a Ni / Cu / YSZ cermet having a uniform particle size distribution can be produced with a smaller particle size than the raw powder. Therefore, it is possible to improve the characteristics of the high temperature electrolytic reduction electrode including the same.

Defoamers may be further added to suppress foaming of the mixture in high energy ball milling processes. As such antifoaming agent, for example, polyethylene ethylene (PolyEthylene Glycol) can be used.

In addition, dispersants may be further added to promote the dispersion of Ni, Cu, and YSZ powders and terpineol in high energy ball milling processes. As such a dispersant, for example, fish oil may be used.

In addition, a plasticizer may be further added to increase the manufacturability of the Ni / Cu / YSZ cermet, ie, increase yield. As such a plasticizer, glycerol or dibutyl phthalate (DBP) can be used, for example. In the cathode for high temperature electrolysis, it is important to prepare a composite in which Ni and Cu, which are electrically conductive materials, and YSZ, which are ion conductive materials, are uniformly distributed. Therefore, the plasticizer may give plasticity to materials during a high energy ball mill process. Makes it possible to produce a fine and even distribution. Yield improvement by the addition of plasticizers usually appears on the order of 5-10%.

1A to 1E are SEM photographs showing examples of particle sizes and shapes of Ni / Cu / YSZ cermets prepared by the method of preparing a cathode material for high temperature water electrolysis according to an embodiment of the present invention. Figure 1a is a SEM image ball milled for 12 hours, the particle size of the powder is an average 1.1㎛, the size of the particles slightly compared to the raw powder.

The photographs of FIGS. 1B-1E increase the ball milling time at 12 hour intervals (ie, after 24 hours in FIG. 1B, after 36 hours in FIG. 1C, after 48 hours in FIG. 1D, and after 60 hours in FIG. 1E). The results of the preparation are shown. As the ball milling time becomes longer, the size of the particles may be gradually refined.

2A to 2D are photographs showing a cermet powder prepared by the method for preparing a cathode material for high temperature water electrolysis according to an embodiment of the present invention and a distribution diagram of Ni, Cu, and YSZ particles (after 60 hours). In order, FIG. 2A shows Ni / Cu / YSZ powder, FIG. 2B shows Ni, FIG. 2C shows Cu, and FIG. 2D shows the distribution of YSZ particles.

Referring to FIGS. 2A to 2D, in particular, as shown in the element distribution diagram of the energy dispersive X-ray analyzer (EDX) of FIGS. 2B to 2D, each of the elements Ni, Cu, and YSZ is represented. It can be confirmed that it is uniformly distributed.

3 is a diagram illustrating a particle size distribution with an increase in ball milling time.

Referring to FIG. 3, it can be seen that as the ball milling time increases, the size of the particle size gradually decreases from about 40 to 250 nm. The finer the particles, the wider the area of the three-phase interface in which the electrolytic reaction occurs, so that the electrical conductivity and the ionic conductivity can be improved, and the connection between the particles can be smoothly formed, thereby improving the performance of the high temperature electrolytic reduction electrode. .

FIG. 4 shows the results of X-ray diffraction patterns carried out to observe changes in the respective crystal structures for ball milling of Ni / Cu / YSZ cermet at 12 hour intervals up to 12 to 60 hours.

Referring to FIG. 4, as the ball milling time is increased, the peaks of Ni and Cu are smoothed, which is repeated as the ball milling time is increased and the crushing and pressure contact due to the collision between the balls and the Ni, Cu, and YSZ materials are repeated. This peak may be caused by partial damage of the grain boundaries of Ni and Cu. On the other hand, the peak of YSZ shows the same peak regardless of the ball mill time. During the 60-minute ball mill, it can be seen that the crystallinity exists in favor of electrical conduction.

Table 2 shows the measurement results of the electrical conductivity of Ni / Cu / YSZ cermet (invention, Example) and Ni / YSZ cermet (prior art, comparative example) subjected to reduction heat treatment at 900 ° C.

Ball milling time Comparative Example Conductivity Average (S / cm) Example Conductivity Average (S / cm) Porosity (%) 12 - 0.2 x 10 ³ 35.5 24 1.4 x 10 ⁴ 1.6 x 10 ⁴ 35.3 36 - 1.9 x 10 ⁴ 35.9 48 - 3.0 x 10 ⁴ 36.4 60 - 4.4 x 10 ⁴ 39.9

It can be seen that the electrical conductivity increases as the ball milling time increases. The electrical conductivity changes depending on the content of Ni and Cu, which are electron transfer paths, and the connection of particles. Therefore, as the ball milling time is increased, the electrical conductivity is increased, and the addition of Cu having excellent electrical conductivity and the fine production of Ni and Cu particles have an effect on the electrical conductivity by improving the connection between the particles. Such a microstructure is believed to work better than 1.4x10 ⁴ S / cm in electrical conductivity of the prior art (ie, Comparative Example, Patent Application No. 10-2004-0075766 (filed September 22, 2004)).

In order to generate an electrolytic reaction in the three-phase interface of water molecules, a certain amount of porosity is required to penetrate the reduction electrode evenly. Table 2 above shows the porosity results measured by the mercury porosimetry, and it can be seen that the porosity also increases as the ball mill time increases. The Ni / Cu / YSZ cermet, having a ball milling time of 60 hours, carried out under sintering conditions at 900 ° C. for 2 hours, is considered to have sufficient pore formation to be provided as a cathode.

In the above-described method for producing a high temperature electrolytic cathode material according to the present invention, a Cu powder having excellent electrical conductivity is added to Ni / YSZ, which is a conventional cathode material, to perform a wet milling process using a mechanical alloying method to obtain Ni under predetermined conditions. By manufacturing the / Cu / YSZ cermet, the electrical conductivity is superior to that of the conventional Ni / YSZ electrode material, and the three-phase interface in which the electrolytic reaction occurs can be secured widely.

1A to 1E are SEM photographs showing examples of particle sizes and shapes of Ni / Cu / YSZ cermets prepared by the method of preparing a cathode material for high temperature water electrolysis according to an embodiment of the present invention.

2A to 2D are photographs showing the cermet powder prepared by the method for preparing the cathode material for high temperature electrolysis according to an embodiment of the present invention and the distribution of Ni, Cu, and YSZ particles.

3 is a diagram illustrating a particle size distribution with an increase in ball milling time.

FIG. 4 shows the results of X-ray diffraction patterns carried out to observe changes in the respective crystal structures for ball milling of Ni / Cu / YSZ cermet at 12 hour intervals up to 12 to 60 hours.

Claims (11)

Ni powder, Cu powder and YSZ powder having particle sizes of 3 μm or less, 10 μm or less and 220 nm, respectively, were mixed in a volume ratio of 10:50:40 to 50:10:40, and after the addition of terpineol, ball milling To form a Ni / Cu / YSZ cermet. delete The method according to claim 1, The number of revolutions in the ball mill is a method for producing a high temperature electrolytic reducing material, characterized in that 200 to 500rpm. The method according to claim 1, The ball milling time is 24 hours to 60 hours, characterized in that the method for producing a high temperature electrolytic reduction cathode material. The method according to claim 1, The particle size of the Ni / Cu / YSZ cermet is 0.5 to 4㎛ method for producing a cathode material for high temperature electrolytic, characterized in that. The method according to any one of claims 1 and 3 to 5, A method of producing a cathode material for high temperature water electrolysis, further comprising adding an antifoaming agent. The method according to any one of claims 1 and 3 to 5, A method of producing a cathode material for high temperature electrolysis, further comprising adding a dispersant. The method according to any one of claims 1 and 3 to 5, A method of producing a cathode material for high temperature electrolysis, further comprising the step of adding a plasticizer. The method according to claim 6, The antifoaming agent is a polyethylene glycol (PolyEthylene Glycol) method of producing a cathode material for high temperature electrolytic, characterized in that. The method of claim 7, The dispersant is a fish oil (fish oil) characterized in that the method for producing a high temperature electrolytic ring electrode material. The method according to claim 8, The plasticizer is glycerol (glycerol) or dibutyl phthalate (DiButyl Phthalate) characterized in that the manufacturing method of the cathode material for high temperature water electrolysis.

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