KR100621565B1 - Method of Preparing material for the high temperature electrolysis - Google Patents

Abstract

In the method for producing a material for a high temperature electrolytic electrode, a nickel (Ni) or nickel oxide (NiO) powder and YSZ (Yttrium Stabilized Zirconia) powder are mixed and milled at a volume ratio of 0.55 to 2 by volume to form a Ni / YSZ alloy. Prepare a substance for use. The electrode material formed by the above-described method has a fine particle size and the electrical conductivity is significantly increased, so that a high-temperature electrolytic electrode having improved performance can be formed.

Description

Method of preparing material for high temperature electrolytic electrode {Method of Preparing material for the high temperature electrolysis}

1 is a graph showing the change of the X-ray diffraction pattern of NiO / YSZ alloy according to the milling method of NiO powder and YSZ powder.

2 is a graph showing the change of X-ray diffraction pattern of NiO / YSZ alloy with milling time of NiO powder and YSZ powder.

3 is a graph showing the change of the X-ray diffraction pattern of Ni / YSZ alloy according to the milling method of Ni powder and YSZ powder.

Figure 4 is a graph showing the particle size and distribution of Ni / YSZ alloy according to the milling method of NiO and YSZ powder.

Figure 5 is a graph showing the particle size and distribution of Ni / YSZ alloy according to the dry milling method of Ni and YSZ powder.

6 is a graph showing particle size and distribution of Ni / YSZ alloys according to the wet milling method of Ni and YSZ powders.

7 is a SEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of NiO powder and YSZ powder.

8 is a SEM photograph showing the particle size and shape of the Ni / YSZ alloy according to the wet milling of NiO powder and YSZ powder.

9 is a TEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of NiO powder and YSZ powder.

10 is a TEM photograph showing the size and shape of Ni / YSZ alloy particles according to wet milling of NiO powder and YSZ powder.

11 is a SEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of Ni powder and YSZ powder.

12 is a SEM photograph showing the size and shape of the particles of the Ni / YSZ alloy according to the wet milling of Ni powder and YSZ powder.

The present invention relates to a method for producing an electrode material, and more particularly to providing a method for producing a material for a high-temperature water electrolytic electrode that is applied to the production of hydrogen.

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 being used as the main energy sources are subject to problems caused by rising prices and exhaustion, and due to stricter environmental regulations such as emissions of air pollutants such as NOx, SOx, and various dusts generated after use, and global warming by carbon dioxide. Alternatively, research on the production and production 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, water electrolysis 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 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. Hydrogen production method using high temperature water electrolysis in the above-mentioned tank manufacturing method is similar to solid oxide fuel cells in terms of its configuration and the operating temperature is higher than 600 ℃ high physical properties that can be produced in a stable form at high temperatures Research to investigate this is needed.

Among them, the cathode material is particularly important because it serves to separate oxygen ions from water by electrolysis, and thus has high oxygen ion conductivity and electron conductivity and must be stable to H ₂ O / H ₂ mixture. Until now, Ni / YSZ cermet is mainly used as a composite material of a cathode including nickel or nickel, and NiO / YSZ has been manufactured first and then reduced. Ni / YSZ is an alloy of Ni and YSZ for high electrical conductivity and ionic conductivity. Ni / YSZ should be a porous material that is easy to move and diffuse H ₂ O and O- ² , and uniformly distribute fine Ni particles for high electrical conductivity. The electrons must move smoothly. In particular, the size of the three-phase interface is very important because the electrochemical reaction takes place in the three-phase interface consisting of Ni, YSZ and pores in the cathode.

In addition, the performance of Ni / YSZ is greatly affected by the microstructure depending on the particle size. The particle size of Ni and YSZ is an important factor in determining the microstructure and also affects the amount of three-phase interface that determines the performance of the cathode. In addition, the effect of Ni sintering, which is a deterioration factor of the cathode, can control the thermal expansion coefficient of the alloy (Cermet) according to the Ni content, but particle coarsening occurs due to sintering at high temperature, thereby degrading the electrode performance. That is, it is difficult to form an electrode that maintains the microstructure while maintaining porosity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a material for an electrolytic electrode, which can produce an electrode in which coarsening of sintered particles of a material applied to the electrolytic electrode is maintained and porosity is maintained.

Method for producing a material for the electrolytic electrode according to an embodiment for achieving the above object of the present invention is a nickel (Ni) or nickel oxide (NiO) powder and YSZ (Yttrium Stabilized Zirconia) powder 1: 0.55 ~ 2 volume ratio Mix milling to form a Ni / YSZ alloy.

In addition, the method for producing a material for a electrolytic electrode according to a more specific embodiment to achieve the object is a mixture of nickel (Ni) or nickel oxide (NiO) powder and YSZ (Yttrium Stabilized Zirconia) powder 1: 0.55 ~ 2 volume ratio After the wet milling, the resultant is press-molded, and then the press-formed result is sintered to form a Ni / YSZ alloy.

The Ni / YSZ alloy powder is formed by performing a dry milling process performed in a dry atmosphere or a wet milling process performed in an atmosphere provided with ethanol. It is preferably formed by a wet milling process. The sintering is characterized in that it is carried out at 900 to 1400 ℃.

As described above, the Ni / YSZ alloy powder formed by directly mixing and milling Yttrium Stabilized Zirconia (YSZ) powder on nickel (Ni) or nickel oxide (NiO) powder has finer particles since coarsening is prevented during sintering. . By using the above-described powder, it is possible to form an electrode having excellent electrical conductivity while maintaining porosity.

Hereinafter, a method of manufacturing the Ni / YSZ alloy, which is a material for the electrolytic electrode of the present invention, will be described in detail.

 The method for producing the Ni / YSZ alloy of the present invention is largely divided into two methods.

In the first method, a Ni / YSZ alloy is formed by directly mixing nickel (Ni) powder or nickel oxide (NiO) powder with yttrium stabilized zirconia (Yttrium Stabilized Zirconia) powder, followed by mechanical milling.

The nickel powder is preferably particles having a size of 70 μm or less, and the nickel oxide powder has a size of 270 to 350 nm. As the YSZ (TZ-8YS, Tosoh) powder, it is preferable to use zirconia oxide (ZrO ₂ ) stabilized with 8 mol% of yttrium oxide (Y ₂ O ₃ ).

In the Ni / YSZ alloy formation, the nickel powder and the YSZ powder are mixed in a volume ratio of 0.5 to 2, preferably in a volume of 1: 0.6 to 1.5.

The milling is divided into a dry milling process and a wet milling process. The dry milling process is to mill for 20 to 30 hours using a planetary ball mill at room temperature. In order to prevent excessive welding in the dry milling process, it is preferable to add stearic acid (stearic acid, CH ₃ (CH ₂ ) ₁₆ COOH) to 0.1 wt% to 100 wt% of the Ni / YSZ alloy. The milling time is preferably carried out for about 24 hours.

The wet milling is to mill for 20 to 30 hours using a planetary ball mill in an ethanol provided atmosphere. The ethanol prevents agglomeration of the raw materials added to the ball mill and at the same time, the raw materials smoothly play contact with the balls. It is preferable to perform a baking treatment at about 60 ° C. after the wet milling process.

As a second method, the resultant formed by performing the same process as the first method described above is sintered to form a Ni / YSZ alloy. The sintering process is carried out at 900 to 1400 ℃. Preferably at 1350 ° C. Here, the sintering process provides the effect of increasing the electrical conductivity of the Ni / YSZ alloy.

 Description of the formation of the result is omitted in order to avoid duplication because it has been described in detail above.

In addition, a more specific embodiment is to form a Ni / YSZ alloy by pressing and molding the resultant formed by the same process as the first method described above and then sintered. The press molding is carried out in a vacuum or in a hydrogen atmosphere. Here, the press forming and sintering processes provide the effect of further increasing the electrical conductivity of the Ni / YSZ alloy. Description of the formation of the result is omitted in order to avoid duplication because it has been described in detail above.

The manufacturing method of the present invention has a great feature in reducing the reduction process in the conventional Ni / YSZ manufacturing process during the milling process by mechanical energy by directly mixing Ni and NiO with YSZ during milling, and also directly reducing the density difference between Ni and YSZ. Considering the wet milling process of adding ethanol to improve the mechanical properties of the electrode material.

Since the Ni / YSZ alloy, which is a material for the electrolytic electrode formed by the above-described methods, has a fine particle size and the electrical conductivity is significantly increased, it is possible to form a high-temperature electrolytic electrode having an improved performance.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following Examples are intended to illustrate the present invention, but are not limited thereto.

Example 1

600 ml of nickel (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 nickel powder and YSZ powder were used as ball mills. Pulverisette 5, Fritsch)). Dry milling was then performed for about 24 hours to produce a Ni / YSZ alloy.

Example 2

A Ni / YSZ alloy was manufactured in the same manner as in Example 1, except that a nickel oxide powder was used instead of the nickel (Ni) powder.

Example 3

600 ml of nickel (Ni) powder, 400 ml of YSZ powder, and 600 to 1300 ml of ethanol were put into a planetary mill, and wet milling was performed for about 24 hours to prepare a Ni / YSZ alloy.

Example 4

A Ni / YSZ alloy was manufactured in the same manner as in Example 3, except that a nickel oxide powder was used instead of the nickel (Ni) powder.

Example 5

600 ml of nickel (Ni) powder, 400 ml of YSZ powder, and 600-1300 ml of ethanol were put into a planetary mill, and wet milling was performed for about 24 hours. After the wet milling process was carried out to form a product in a vacuum state it was sintered at 1350 ℃ for 2 hours to form a Ni / YSZ alloy.

Comparative Example 1

600 ml of nickel oxide (NiO) powder and 400 ml of YSZ powder were added to a ball mill, followed by dry milling for about 24 hours, and hydrogen reduction was performed at 900 ° C hydrogen gas to prepare a Ni / YSZ alloy.

Comparative Example 2

A Ni / YSZ alloy was manufactured in the same manner as in Example 1, except that the milling time was applied at 90 hours instead of 24 hours.

Comparative Example 3

Ni / YSZ alloys were prepared in the same manner as in Comparative Example 1, except that wet milling was applied instead of dry milling.

Experimental Example 1

X-ray diffraction analysis was carried out by XRD (X-ray diffractometer, Rikagu) to measure the alloying state of each Ni / YSZ alloy prepared according to Example 2 and Example 4 described above.

1 is a graph showing the change of the X-ray diffraction pattern of NiO / YSZ alloy according to the milling method of NiO powder and YSZ powder.

The diffraction pattern (a) shown in FIG. 1 is a diffraction pattern of the NiO / YSZ alloy formed by wet milling, and the intensity of the peak of NiO tends to decrease, and the peak of the YSZ is widened. The (b) diffraction pattern is a diffraction pattern of the alloy formed by dry milling, and it was confirmed that the YSZ decreases and the peak of NiO increases relatively.

In the above-described pattern, since no elements other than the NiO powder and the YSZ powder were found, the oxide was not reduced, and the crystallinity of the NiO was relatively smaller in the wet milling method than in the dry milling method.

Experimental Example 2

X-ray diffraction analysis was carried out by XRD (X-ray diffractometer, Rikagu) to observe the change of fms crystal structure according to milling time of Ni / YSZ alloys prepared according to Example 2 and Comparative Example 2, respectively.

2 is a graph showing the change of X-ray diffraction pattern of NiO / YSZ alloy with milling time of NiO powder and YSZ powder.

The diffraction pattern (a) shown in FIG. 2 is a diffraction pattern of the NiO / YSZ alloy powder formed by the method of Example 2, and it was confirmed that the width of the peak decreases and the height of the peak increases. However, in comparison, the diffraction pattern (b) of 2 confirmed that the NiO / YSZ alloy powder became amorphous, so that the width of the peak was wide and the height of the peak was very small. That is, it was confirmed that the crystallinity of the alloy powder milled for 24 hours in the milling cycle is the highest.

Experimental Example 3

X-ray diffraction analysis was carried out by XRD (X-ray diffractometer, Rikagu) to know the alloying state of each Ni / YSZ alloy prepared according to Example 1 and Example 3 described above.

3 is a graph showing the change of the X-ray diffraction pattern of Ni / YSZ alloy according to the milling method of Ni powder and YSZ powder.

The (a) diffraction pattern shown in FIG. 3 is a diffraction pattern of wet milled Ni and YSZ powders, in which the width of the peak of the YSZ is narrowed and the peak intensity decreases to have an amorphous form. Ni peaks are relatively increased in intensity, and the width of the peaks is also wide. The (b) diffraction pattern is a diffraction pattern of dry milled Ni and YSZ powders, where YSZ has a large peak intensity and a relatively small peak of Ni.

Experimental Example 4

In order to measure the particle size of each Ni / YSZ alloy prepared according to Example 2 and Example 4 described above was measured using PSA (Mastersizer2000, MALVERN).

Figure 4 is a graph showing the particle size and distribution of Ni / YSZ alloy according to the milling method of NiO and YSZ powder.

As shown in FIG. 4, the particle size of YSZ powder (▼) and NiO powder (▲) showed the largest distribution at 223 nm and 289 nm. The particle size of the Ni / YSZ alloy (■) obtained after milling these powders by dry method showed the largest distribution at about 750 nm. This is because the particles of YSZ powder and NiO powder agglomerate with each other under dry milling conditions, so that the size of Ni / YSZ alloy (■) particles is coarser than that of raw powder.

On the other hand, the particle size of the Ni / YSZ alloy (•) obtained after milling these powders by wet method in which ethanol was added showed the largest distribution at 223 nm and a slight distribution at 50 nm. The size of the Ni / YSZ alloy (●) obtained by the wet method was the same or finer than that of the raw powder, which prevented the aggregation of the particles of the YSZ powder and the NiO powder due to the addition of ethanol and the contact of the powder with the balls. Because it was done smoothly.

Experimental Example 5

Each of the Ni / YSZ alloys prepared in Examples 1 and 3 described above was measured using PSA (Mastersizer2000, MALVERN) to measure particle size.

5 is a graph showing the particle size and distribution of Ni / YSZ alloy powder according to the dry milling method of Ni and YSZ powder, Figure 6 is a particle size and distribution of Ni / YSZ alloy according to the wet milling method of Ni and YSZ powder A graph representing.

FIG. 5 is a graph showing particle distribution after dry milling of Ni and YSZ, showing the largest distribution at about 60 μm, and particle distribution at 1.5 μm and 10 μm. The particle size of the Ni powder was 63 μm, and the particles having a size of about 60 μm were determined to be particles due to Ni, and showed a size similar to that of the Ni raw material. The particles having sizes of 1.5 μm and 10 μm are considered to be coarsened by coagulation of the YSZ particles.

FIG. 6 is a graph showing particle distribution after wet milling Ni and YSZ, showing the largest distribution at about 14 μm, a large distribution at 3.5 μm, and a slight distribution at around 100 nm. It has been shown to exist as particles of significantly smaller size than the powder.

The particle size of the Ni / YSZ alloy powder by wet milling was 14 μm, whereas the particle size of the YSZ powder, which is the raw material, was 223 nm, and the particle size of the Ni powder was 63 μm. The contact was smoothed, and thus, the fineness of the raw powder during ball milling influenced the Ni / YSZ particle size. In addition, the particle distribution of 100 nm is likewise a peak due to the miniaturization of YSZ particles and the peak of 3.5 μm is a result of the agglomeration of particles finely refined by ball milling. These results are consistent with the PSA results of the NiO and YSZ powder particles of Experimental Example 3.

Experimental Example 6

In order to observe the shape and size of the particles of the Ni / YSZ alloys prepared in Examples 2 and 4, respectively, the measurement was performed using SEM (JSM-35CF, JEOL).

7 is a SEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of NiO powder and YSZ powder, and FIG. 8 is a particle size and shape of Ni / YSZ alloy according to wet milling of NiO powder and YSZ powder. It is a SEM photograph showing the.

Referring to the SEM photograph of FIG. 7, the average particle size of the Ni / YSZ alloy powder was 700 nm, and it was confirmed that the particles were evenly dispersed. Referring to the SEM photograph of FIG. 8, the average particle size of the Ni / YSZ alloy powder was 250 nm, and it was confirmed that the particle size was smaller than that of the raw powder. This is consistent with the results of Experimental Example 4 as a result of which the addition of ethanol increases the performance of milling.

Particularly, the particles of NiO powder were spherical in the dry milling method, but in the wet milling method, the spherical particles were split and refined due to the effect of the addition of ethanol. It was also confirmed that NiO and YSZ were evenly dispersed.

Experimental Example 7

In order to observe the particle shape and size of each of the Ni / YSZ alloy prepared in Examples 2 and 4 described above was measured using TEM (JEOL-200CX, JEOL).

9 is a TEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of NiO powder and YSZ powder, and FIG. 10 is the size and shape of Ni / YSZ alloy particles according to dry milling of NiO powder and YSZ powder. It is a TEM photo showing.

Looking at the TEM picture of Figure 9 the particle size of the Ni / YSZ alloy powder represents 100 to 700nm. Here, the EDS analysis shows that particles having a size of 100 nm are particles of YSZ powder, particles having a size of 400 nm are particles of NiO powder, and particles having a size of 400 to 700 nm are particles of Ni / YSZ alloy.

Looking at the TEM picture of Figure 10, the Ni / YSZ powder particles have a size of 50 ~ 400nm. Here, as a result of the EDS analysis, particles having a size of 150 nm are particles of YSZ powder, particles having a size of 400 nm are particles of NiO powder, and particles having a size of 50 nm are particles of Ni / YSZ alloy powder. These results are consistent with the results of Experimental Example 5, wherein ethanol addition further improved the performance of the milling process.

Experimental Example 8

In order to observe the shape and size of the particles of the Ni / YSZ alloy prepared in Examples 1 and 3, respectively, the measurement was performed using SEM (JSM-35CF, JEOL).

FIG. 11 is a SEM photograph showing the size and shape of Ni / YSZ alloy particles according to dry milling of Ni powder and YSZ powder, and FIG. 12 is the size of particles of Ni / YSZ alloy according to wet milling of Ni powder and YSZ powder. SEM photograph showing the shape.

Referring to the SEM photograph of FIG. 11, Ni particles having a size of about 40 μm and fine YSZ powders were confirmed, and the Ni particles were determined to be still in progress due to agglomeration of particles in the ball milling method in which agglomeration and refinement were repeated after dry milling. do. The Ni particles in the Ni / YSZ alloy powder are considered to be large.

Looking at the SEM photograph of FIG. 12, it was confirmed that the largest particles were about 10 μm and most of them had evenly dispersed particles having a fine size of several hundred nm and several μm. This is a result showing that the large Ni particles of 63 mu m were refined in the milling process in addition to ethanol. In addition, after wet milling, the particles of the Ni / YSZ alloy powder have a finer size than the raw powder.

Experimental Example 9

Each Ni / YSZ alloy formed according to Examples 1, 3, 5 and Comparative Examples 1, 3 described above was measured for electrical conductivity at room temperature using a 4-point probe. The results are shown in Table 1 below.

Condition Electrical conductivity Example 1 (dry milling) 3.2 × 10 ^-7 (S / cm) Example 3 (Wet Milling) 2.0 × 10 ² (S / cm) Example 5 (Wet Milling, Sintering) 1.4 × 10 ⁴ (S / cm) Comparative Example 1 (dry milling, reduction) 2.5 × 10 ^-6 (S / cm) Comparative Example 3 (Wet Milling, Reduction) 3.5 × 10 ^-6 (S / cm)

As shown in Table 1, the electrical conductivity after reduction of the Ni / YSZ alloy prepared by the dry or wet ball milling method is 2.5 × 10 ⁻⁶ and 3.5 × 10 ⁻⁶ (S / cm), respectively. In addition, as in Example 1, the electrical conductivity of the Ni / YSZ alloy obtained without the reduction process after dry ball milling is 3.2 × 10 ⁻⁷ (S / cm) to the electrical conductivity of the Ni / YSZ alloy subjected to the reduction process. The value was lower than that. As can be seen from Figure 11, the relatively large Ni powder particles are not evenly distributed Ni chain can not be connected, and this is believed to be the result obtained by the movement of the electron is not smooth.

In addition, after the wet ball milling, the electrical conductivity of the Ni / YSZ alloy manufactured without the reduction process is 2 × 10 ² (S / cm). As shown in the results of FIG. 12, Ni / YSZ particles and Ni powder particles are evenly dispersed due to the addition of ethanol to serve as a connection path for electrons, and thus have relatively higher electrical conductivity than other cases. In particular, as in Example 5, after the wet ball milling, the electrical conductivity of the Ni / YSZ alloy manufactured without undergoing a reduction process after undergoing a sintering process in a vacuum atmosphere at 900 ° C. is 1.4 × 10 ⁴ (S / cm), which is high. Indicated. This result is to prevent the oxidation of Ni / YSZ in a vacuum atmosphere to improve the electrical properties of the Ni / YSZ alloy.

In the electrode material manufacturing method of the present invention described above, by mixing Ni or NiO directly with YSZ, a Ni / YSZ alloy may be manufactured without performing a reduction process performed in a conventional Ni / YSZ manufacturing process in a milling process by mechanical energy. have.

In addition, since it is manufactured by performing a wet milling process in which ethanol is added in consideration of the density difference between Ni and YSZ, mechanical properties of the electrode material may be improved. The Ni / YSZ alloy, which is a material for the electrolytic electrode manufactured by the above method, has a fine particle size and significantly increases the electrical conductivity, thereby forming a high-temperature electrolytic electrode having an improved performance.

Claims (5)

A method for producing a material for an electrolytic electrode, in which a nickel (Ni) or nickel oxide (NiO) powder is mixed and milled with a Yttrium Stabilized Zirconia (YSZ) powder at a volume ratio of 0.55 to 2 to form a Ni / YSZ alloy. The method of claim 1, wherein after the mixed milling, sintering at a temperature of 900 ° C. to 1400 ° C. is further performed. The method of claim 2, further comprising performing pressure molding before the sintering. The method according to any one of claims 1 to 3, wherein the milling is a dry milling process or a wet milling process performed in an atmosphere to which ethanol is added. The method for producing a material for a electrolytic electrode according to any one of claims 1 to 3, wherein the nickel powder has a size of 70 µm or less.

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