KR20110083371A - Solid oxide fuel cell containing composite nanotube and preparation method thereof - Google Patents

Abstract

PURPOSE: A solid oxide fuel cell containing composite nanotube and a preparation method thereof are provided to reduce electrode resistance by increasing the area of a triple phase boundary capable of contacting an oxygen ion conductor, electron conductor and fuel or air. CONSTITUTION: A solid oxide fuel cell containing composite nanotube comprises a solid oxide electrolyte, a first electrode, and a second electrode. The solid oxide fuel cell containing composite nanotube includes one or more electrodes selected from the group consisting of first and second electrodes. In the solid oxide fuel cell, the composite nanotube forms a 2D or 3D structure. The solid oxide fuel cell has a nonwoven form.

Description

Solid oxide fuel cell containing composite nanotube and preparation method

It relates to a solid oxide fuel cell comprising a composite nanotube, and a method for producing the composite nanotube.

Fuel cells of interest as one of alternative energy are polymer electrolyte membrane fuel cell (PEMFC), phosphoric acid fuel cell (PAFC) and molten carbonate fuel cell (MCFC) depending on the type of electrolyte. molten carbonate fuel cell) and solid oxide fuel cell (SOFC).

The solid oxide fuel cell uses a solid oxide having ion conductivity as an electrolyte. The solid oxide fuel cell has high efficiency, high durability, various types of fuels, and relatively low manufacturing cost.

The unit cell of the solid oxide fuel cell includes a solid oxide electrolyte and an electrode. Since the solid oxide fuel cell operates at a high temperature of 750 to 1200 ° C, only a stable material at the high temperature may be applied. Therefore, it is desirable to lower the operating temperature of the solid oxide fuel cell. However, when the operating temperature is lowered, the resistance of the electrode is rapidly increased and the output density is lowered.

Accordingly, it is required to increase the area of the oxygen phase conductor, the electron conductor, and the triple phase boundary to which fuel or air may contact in the electrode in order to suppress the increase in resistance of the electrode.

One aspect is to provide a novel structure of solid oxide fuel cell comprising composite nanotubes.

Another aspect is to provide a method for producing the composite nanotubes.

According to one aspect,

Solid oxide electrolytes; A first electrode; And a second electrode,

There is provided a solid oxide fuel cell in which at least one electrode selected from the group consisting of the first electrode and the second electrode comprises a composite nanotube.

According to the other side

Preparing a first solution by adding a precursor of an electrode component and a precursor of a solid oxide electrolyte component to a first solvent;

Preparing a second solution by adding a solubility improving agent to the second solvent;

Preparing a mixed solution by mixing the first solution and the second solution;

Preparing a nanofiber by electrospinning the mixed solution; And

A method for manufacturing a composite nanotube for a solid oxide fuel cell, comprising: heat treating the nanofibers.

According to one aspect, the electrode includes a composite nanotube, the resistance of the electrode can be reduced by increasing the area of the three-phase interface.

Figure 1a is a scanning electron microscope image of the composite nanotube prepared in Example 1. The size of the scaler is 10.0 μm.
Figure 1b is a scanning electron microscope image of the composite nanotube prepared in Example 1. The size of the scaler is 200 nm.
Figure 1c is a scanning electron microscope image of the composite nanotube prepared in Example 1. The size of the scaler is 50 nm.
Figure 2a is a scanning electron microscope image of the composite nanotube prepared in Example 2. The scaler is 100 nm in size.
Figure 2b is a transmission electron microscope image of the composite nanotube prepared in Example 2. The scaler is 100 nm in size.
3 is a transmission electron microscope image of the composite nanotube prepared in Example 3.
4 is an EDM mapping image of the composite nanotubes prepared in Example 2. FIG.
5 is an X-ray diffraction test result of the composite nanotube prepared in Example 1.
FIG. 6 is a Nyquist plot of the results of negative electrode resistance measurements on the cells prepared in Example 4 and Comparative Example 1. FIG.
7 is a schematic diagram of the electrospinning apparatus used in Example 1. FIG.

Hereinafter, a solid oxide fuel cell and a method of manufacturing the composite nanotube according to one or more exemplary embodiments will be described in more detail.

A solid oxide fuel cell according to an embodiment includes a solid oxide electrolyte; A first electrode; And a second electrode, wherein at least one electrode selected from the group consisting of the first electrode and the second electrode comprises a composite nanotube.

Since the composite nanotube includes an electron conductor as an electrode component and an oxygen ion conductor as a solid oxide electrolyte component, an area of a triple phase boundary to which an oxygen ion conductor, an electron conductor, and fuel or air can contact is reduced. Can be increased. As the area of the three-phase interface is increased, the electrode resistance can be reduced.

The composite nanotubes may form a two-dimensional or three-dimensional structure. For example, the structure may be in the form of a two-dimensional or three-dimensional non-woven fabric, but is not necessarily limited to this form may form any type of structure that can be used in the art. For example, the composite nanotubes may be continuously radiated onto a predetermined substrate by an electrospinning method and then thermally treated to form a non-woven sheet. Depending on the thickness of the sheet may be in the form of a two-dimensional non-woven or three-dimensional non-woven.

The solid oxide electrolyte may be disposed between the first electrode and the second electrode, and the two-dimensional or three-dimensional composite nanotube structure may be disposed at an interface between the electrodes and the solid oxide electrolyte. For example, the composite nanotube structure may be disposed on the electrode surface in contact with the solid oxide. For example, the composite nanotube structure itself may be an electrode.

The outer diameter of the composite nanotube may be 50 to 100nm, but is not necessarily limited to this range may be appropriately adjusted within the range to reduce the resistance of the electrode. For example, the outer diameter of the nanotubes may be 50 to 80nm.

The inner diameter of the composite nanotube may be 10 to 40nm, but is not necessarily limited to this range may be appropriately adjusted within a range that can reduce the resistance of the electrode. For example, the inner diameter of the nanotubes may be 15 to 30nm.

The wall thickness of the composite nanotube may be 10 to 30 nm, but is not necessarily limited to this range, and may be appropriately adjusted within a range capable of reducing the resistance of the electrode. For example, the wall thickness of the nanotubes may be 15 to 30nm.

The length of the composite nanotube may be 100nm or more, but is not necessarily limited to this range and may be appropriately adjusted within a range that can reduce the resistance of the electrode. For example, the length of the nanotubes may be from 100nm to 10mm.

The composite nanotube is a composite including components constituting the solid oxide electrolyte and components constituting the electrode at the same time. For example, the composite nanotube may be cermet in which a powder of a material forming the solid oxide electrolyte and nickel oxide are mixed.

As shown in FIG. 5, the composite nanotube included in the solid oxide fuel cell according to the exemplary embodiment includes both a phase of NiO, an electrode component, and a phase of a GDC (gadollium doped ceria), which is a solid oxide component. Include.

Solid oxide electrolyte components included in the composite nanotubes are cation (Y, Sc) doped zirconia (ZrO ₂ ), cation (Gd, Sm) doped ceria (CeO ₂ ), lanthanum-strontium-gadolinium (gallium) -magnesium (La _1-x Sr _x Ga _1-y Mg _y O ₃ ) It may be at least one selected from the group consisting of oxide (LSGM), cation (Y, La) doped bismuth oxide (Bi ₂ O ₃ ), but not necessarily The present invention is not limited thereto, and may be appropriately selected within a range capable of reducing the resistance of the electrode. For example, the solid oxide electrolyte component may be yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), samaria doped ceria (SDC), gadolinia doped ceria (GDC), and the like. The YSZ may be, for example, Zr _0.84 Y _0.16 O ₂ .

Electrode components included in the composite nanotubes are perovskite composite oxides; Lanthanum manganese oxide doped with one or more of strontium, cobalt, and iron; It may be one or more selected from the group consisting of nickel oxide (NiO), metal nickel, copper oxide (CuO), and copper, but is not necessarily limited thereto, and may be appropriately selected within a range capable of reducing the resistance of the electrode. have. For example, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co Metal oxide particles such as, Ni) O ₃ , precious metals such as platinum, ruthenium and palladium, lanthanum manganite doped with strontium, cobalt and iron, La _0.8 Sr _0.2 MnO ₃ (LSM), La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O ₃ (LSCF) and the like.

The composite nanotubes may be porous. The pores may be present through the walls of the composite nanotubes or dispersed throughout from the surface of the composite nanotube walls. For example, the wall of the composite nanotube may be a kind of net-like structure including a plurality of pores in the wall. As shown in FIG. 1C, a plurality of pores may be included in the wall of the composite nanotube. As the composite nanotube includes a plurality of pores, the area of the oxygen ion conductor, the electron conductor, and the triple phase boundary to which fuel or air may contact may be significantly increased. As the area of the three-phase interface is significantly increased, the electrode resistance can be reduced.

The pore diameter of the porous composite nanotube may be 10 nm. For example, the diameter of the pores may be 2 to 10 nm, but is not necessarily limited to this range and may be appropriately adjusted within a range in which electrode resistance may be reduced.

The first electrode may be an anode or a cathode, and the second electrode may be a remaining electrode. For example, the second electrode may be a cathode or an anode.

The thickness of the solid oxide electrolyte, the positive electrode and the negative electrode is not particularly limited as long as it is generally used in the art. For example, the thickness of the solid oxide electrolyte may be 10 μm or less. For example, the solid oxide electrolyte may have a thickness of 5 nm to 10 μm. For example, the solid oxide electrolyte may have a thickness of 5nm to 500nm. For example, the solid oxide electrolyte may have a thickness of 5 nm to 200 nm. For example, the cathode and the anode may have a thickness of 10 μm or less independently of each other. For example, the negative electrode and the positive electrode may have a thickness of 50 nm to 10 μm independently of each other. For example, the cathode and the anode may have a thickness of 50 nm to 500 nm independently of each other. For example, the cathode and the anode may have a thickness of 50 nm to 200 nm independently of each other. For example, the thickness of the cathode and the anode may be the thickness of the composite nanotube structure itself.

For example, the composite nanotubes included in the solid oxide fuel cell include NiO or Ni; And gadolinium doped ceria. The NiO or Ni and gadolithium doped ceria may be included in an atomic% ratio of 0.8: 1.2 to 1.2: 0.8, and may include a plurality of pores having a diameter of 2 to 8 nm in the wall of the tube.

According to another embodiment, a method of manufacturing a composite nanotube for a solid oxide fuel cell may include preparing a first solution by adding a precursor of an electrode component and a precursor of a solid oxide electrolyte component to a first solvent; Preparing a second solution by adding a solubility improver (DMF) and a dispersant (PVP) to the second solvent; Preparing a mixed solution by mixing the first solution and the second solution; Preparing a nanofiber by electrospinning the mixed solution; And heat treating the nanofibers.

The precursor of the solid oxide component used in preparing the first solution may be at least one selected from the group consisting of cerium nitride, gadolithium nitride, zirconium oxide, and yttrium oxide. For example, the precursor may be (NH ₄ ) ₂ Ce (NO ₃ ) ₆ , Gd (NO ₃ ) ₃ xH ₂ O (0 ≦ x ≦ 9).

The precursor of the electrode component used in preparing the first solution may be at least one selected from the group consisting of nickel nitride and copper nitride. For example, the precursor may be Ni (NO ₃ ) ₂ 6H ₂ O.

The first solvent used in preparing the first solution may be at least one selected from the group consisting of ethanol and methanol, and the solubility improving agent used in preparing the second solution may be a dimethylformamide. It may be one or more selected from the group consisting of.

The dispersant used in preparing the second solution may be at least one selected from the group consisting of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

Since the first solution obtained by adding and dissolving the precursor of the solid oxide electrolyte component and the precursor of the electrode component must be electrospun, insoluble materials can be removed before the electrospinning step.

The electrospinning step can be radiated in general methods and conditions known in the art. The voltage applied during the electrospinning may be 1 to 100 kV. The spun solution is formed on the substrate in the form of nanofibers and may have a form of a nonwoven fabric. For example, the substrate may be a solid oxide electrolyte.

Composite nanotubes may be obtained by heat treating the spun nanofibers at 300 to 900 ° C. The heat treatment temperature is not necessarily limited to the above range, any temperature can be used as long as the composite nanotube can be obtained. For example, the heat treatment temperature may be 500 to 700 ℃. The heat treatment may be performed in a 500 ^° C air atmosphere. The heat treatment may be performed for 1 to 10 hours.

The composite nanotube manufacturing method may further include the step of reducing the heat treatment in a hydrogen atmosphere. The heat treatment temperature in the hydrogen atmosphere may be 400 to 1000 ℃, heat treatment time may be 1 to 10 hours. A part or all of NiO contained in the composite may be reduced to Ni by heat treatment in the hydrogen atmosphere. This reduction can also be achieved by driving the fuel cell.

The present invention is described in more detail through the following examples and comparative examples. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.

(Production of Composite Nanotubes)

Example 1

0.476 g of (NH ₄ ) ₂ Ce (NO ₃ ) ₆ , 0.033 g of Gd (NO ₃ ) ₃ xH ₂ O (0≤x≤9) and 0.509 g of Ni (NO ₃ ) ₂ 6H ₂ O were added to 30 ml of anhydrous ethanol. After stirring, the solution was completely dissolved. This is called the first solution.

1 g of polyvinylpyrrolidone was added to 9 ml of dimethylformamide, followed by stirring to completely dissolve it. This is called a second solution.

The mixed solution was prepared by mixing the first solution and the second solution.

The mixed solution was introduced into a syringe of an electrospinning apparatus (Nano C., E-spinning) and then electrospun into a collector while applying a voltage of 16 kV to obtain a nonwoven fabric-shaped nanofiber. A schematic diagram of the electrospinning apparatus is shown in FIG.

The nanofibers were heat treated in an air atmosphere at 500 ° C. for 1 hour to obtain a composite nanotube. The obtained composite nanotubes are shown in FIGS. 1A-1C.

The prepared composite nanotubes had an outer diameter of 40 to 100 nm, an inner diameter of 10 to 50 nm, a wall thickness of 15 to 25 nm, and a pore size of less than 10 nm.

Example 2

The composite nanotubes prepared in Example 1 were further heat-treated in a hydrogen atmosphere of 500 ° C. (5v% H ₂ + 95v% N ₂ ) for 1 hour to obtain composite nanotubes. The resulting composite nanotubes are shown in FIGS. 2A and 2B.

The prepared composite nanotubes had an outer diameter of 40 to 100 nm, an inner diameter of 10 to 50 nm, a wall thickness of 15 to 25 nm, and a pore size of 3 to 10 nm.

Example 3

The composite nanotubes prepared in Example 1 were further heat-treated in a hydrogen atmosphere of 700 ° C. (5v% H ₂ + 95v% N ₂ ) for 1 hour to obtain composite nanotubes. The obtained composite nanotubes are shown in FIG. 3.

The prepared composite nanotubes had an outer diameter of 40 to 100 nm, an inner diameter of 10 to 50 nm, a wall thickness of 15 to 25 nm, and a pore size of 5 to 20 nm.

(EDS experiment)

Evaluation example 1

EDS (Electron Diffraction Sopectra) experiments were performed on the composite nanotubes prepared in Example 1, and the results are shown in Table 1 and FIG. 4. As shown in Table 1, the GDS content and the NiO content showed an atomic ratio of almost 1: 1. Therefore, it can be seen that NiO and GDS are included in almost similar content.

In addition, as shown in Figure 4, Ce, Gd and Ni are uniformly distributed throughout the composite nanotube. 4 is a scanning electron micrograph of the composite nanotube prepared in Example 1 used in the EDS experiment.

Atomic% Ce 21.70 Gd 2.43 Ni 24.38

(X-ray diffraction experiment)

Evaluation example 2

X-ray diffraction experiments were performed on the composite nanotubes prepared in Example 1, and the results are shown in FIG. 5. As shown in FIG. 5, the NiO phase and the GDC phase were clearly distinguished. Thus, the composite nanotube may be a composite of NiO and GDC.

(Manufacture of Solid Oxide Fuel Cell)

Example 4

A composite cell having the following configuration was prepared: NiO + YSZ layer / composite nanotube layer / YSZ solid electrolyte layer / composite nanotube layer / NiO + YSZ layer.

A first electrode and a second electrode including the NiO + YSZ commercial oxide composite (Fuel Cell Materials, USA) layer and the composite nanotube layer were formed, respectively. The composite nanotube layer is a layer including the composite nanotube prepared in Example 1. YSZ solid electrolyte was used commercially available disk (Fuel Cell Materials, USA).

To prepare the cell, the NiO + YSZ oxide composite layer and the composite nanotube layer were sequentially coated on both sides of a commercial solid electrolyte disk using screen printing.

Specifically, a composite nanotube slurry was prepared by mixing the composite nanotube prepared in Example 1 and a commercial solvent (Vehicle, VEH, Fuel Cell Materials) in a 1: 1 volume ratio for the coating. In addition, the oxide composite slurry was prepared by mixing the NiO + YSZ oxide composite and a commercial solvent (Vehicle, VEH, Fuel Cell Materials) in a 1: 1 volume ratio.

The composite nanotube slurry was first coated on a solid electrolyte disk, dried in an oven at 150 ^° C., and the oxide composite slurry was secondarily coated on the composite nanotube layer, and dried under the same conditions to prepare a fuel cell.

This is called cell_b.

Comparative Example 1

A fuel cell was manufactured in the same manner as in Example 4, except that there was no composite nanotube layer.

The configuration of the cell is as follows.

NiO + YSZ layer / YSZ solid electrolyte layer / NiO + YSZ layer

This is called cell_a.

(Electrode resistance measurement)

Evaluation Example 3

The anode resistance (anode polarization, Rp) of the fuel cell manufactured in Example 4 and Comparative Example 1 was measured under a reducing atmosphere of 700 ° C. (hydrogen 5v% + argon 95v%).

Cathode resistance of the cells was measured by a 2-probe method using an impedance analyzer (Material Mates 7260 impedance analyzer). The frequency range was 10 MHz to 1 MHz. The Nyguist plot of the negative electrode resistance measurement results is shown in FIG. 6. 6 is for Comparative Example 1, and cell_b is for Example 4. FIG.

For example, in FIG. 6, the difference between the point where the left side of the hemisphere is extrapolated to contact the X axis and the point at which the right side of the hemisphere is extrapolated to contact the X axis corresponds to the resistance of the negative electrode.

The negative electrode resistance of the cell prepared in Example 4 was 30 ohm, and the negative electrode resistance was significantly reduced compared to the 85 ohm negative electrode resistance of the cell prepared in Comparative Example 4.

Claims (20)

Solid oxide electrolytes; A first electrode; And a second electrode,
At least one electrode selected from the group consisting of the first electrode and the second electrode comprises a composite nanotube. The solid oxide fuel cell of claim 1, wherein the composite nanotubes form a two-dimensional or three-dimensional structure. The solid oxide fuel cell of claim 1, wherein the structure is in the form of a nonwoven fabric. The solid oxide fuel cell of claim 1, wherein the composite nanotube is disposed at an interface between the solid oxide electrolyte and the electrode. The solid oxide fuel cell of claim 1, wherein an outer diameter of the composite nanotube is 40 to 100 nm. The solid oxide fuel cell of claim 1, wherein an inner diameter of the composite nanotube is 10 to 50 nm. The solid oxide fuel cell of claim 1, wherein the composite nanotube has a wall thickness of 15 to 25 nm. The solid oxide fuel cell of claim 1, wherein the composite nanotube comprises a solid oxide electrolyte component and an electrode component. The solid oxide fuel cell of claim 8, wherein the solid oxide electrolyte component and the electrode component are included in an atomic% ratio of 3: 7 to 7: 3. 9. The method of claim 8, wherein the solid oxide electrolyte component is cation (Y, Sc) doped zirconia (ZrO ₂ ), cation (Gd, Sm) doped ceria (CeO ₂ ), lanthanum-strontium-gadolinium (gallium)-magnesium (La _1-x Sr _x Ga _1-y Mg _y O ₃ ) Solid oxide fuel cell at least one selected from the group consisting of oxide (LSGM), cation (Y, La) doped bismuth oxide (Bi ₂ O ₃ ). The method of claim 8, wherein the electrode component is a perovskite composite oxide; Lanthanum manganese oxide doped with one or more of strontium, cobalt, and iron; At least one solid oxide fuel cell selected from the group consisting of nickel oxide (NiO), metal nickel, copper oxide (CuO) and metal copper. The solid oxide fuel cell of claim 1, wherein the composite nanotube is porous. The solid oxide fuel cell of claim 12, wherein a pore included in the porous composite nanotube has a diameter of 10 nm or less. The solid oxide fuel cell of claim 1, wherein the first electrode is an anode or a cathode and the second electrode is a remaining electrode. The method of claim 1, wherein the composite nanotubes are NiO or Ni; And gadolinium doped ceria, wherein the NiO or Ni and gadolithium doped ceria are included in an atomic% ratio of 0.8: 1.2 to 1.2: 0.8, and a plurality of pores having a diameter of 2 to 8 nm are formed on a wall of the tube. Porous solid oxide fuel cell comprising a. Preparing a first solution by adding a precursor of an electrode component and a precursor of a solid oxide electrolyte component to a first solvent;
Preparing a second solution by adding a solubility improving agent to the second solvent;
Preparing a mixed solution by mixing the first solution and the second solution;
Preparing a nanofiber by electrospinning the mixed solution; And
A method for manufacturing a composite nanotube for a solid oxide fuel cell, comprising: heat treating the nanofibers. The method of claim 16, wherein the precursor of the solid oxide electrolyte component is at least one selected from the group consisting of cerium nitride, gadolithium nitride, zirconium nitride, and iturium nitride. The method of claim 16, wherein the precursor of the electrode component is at least one selected from the group consisting of nickel nitride and copper nitride. The method of claim 16, wherein the first solvent is at least one selected from the group consisting of ethanol and methanol. The method of claim 16, wherein the second solvent is at least one selected from the group consisting of dimethylformamide, polyvinylpyrrolidone (PVP), and polyvinyl alcohol (PVA).

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