JP5495377B2 - Power generation method for solid oxide fuel cell - Google Patents

Description

  The present invention relates to a power generation method of a solid oxide fuel cell having a fuel cell that generates power using solid carbon supplied to an anode material as a fuel, and the solid oxide fuel cell.

  Solid oxide fuel having a laminated structure in which an electrolyte layer (solid electrolyte layer) made of an ion conductive solid oxide (oxide ion conductor) is disposed between a cathode (air electrode) and an anode (fuel electrode) The battery (SOFC) is expected as a third generation fuel cell, and its development is progressing.

A solid oxide fuel cell supplies a reducing agent, for example, hydrogen (H ₂ ), carbon monoxide (CO), methane (CH ₄ ), or other gas (fuel gas) to the anode, and an oxidant, for example, , A device that generates electricity by supplying a gas (for example, air) containing oxygen (O ₂ ) or the like (see, for example, Patent Document 1 below).

As described above, normally, in the case of a solid oxide fuel cell (SOFC), the fuel is gaseous, but it has been proposed to use solid carbon having a very high energy density as the fuel (Patent Document 2). In Patent Document 2, solid carbon supported on an anode material is reacted with carbon dioxide (CO ₂ ) to be converted into gaseous carbon monoxide (CO), and the gaseous carbon monoxide (CO) is oxidized. It is characterized by generating electricity.

  However, the solid oxide fuel cell described above includes an activation process in which an organic compound such as a hydrocarbon is introduced into the anode, a thermal decomposition reaction proceeds, and solid carbon is once supported on the anode material as an essential process. . That is, it is necessary to previously support solid carbon as a fuel on the anode, and since solid carbon cannot be replenished during power generation, the fuel cell reaction cannot be continuously continued. It is difficult to apply as it is to a power generation system that requires proper operation, and its technical value cannot be fully exhibited from the viewpoint of practical use.

JP-A-9-129256 JP 2008-198585 A

  The present invention has been made in view of the above-mentioned background art, and the problem is that the anode material temporarily supports solid carbon generated by introducing an organic compound such as a hydrocarbon into the anode and causing a thermal decomposition reaction to proceed. The present invention provides a solid oxide fuel cell and a power generation method thereof in which the convenience of fuel supply is improved and the convenience is improved in a fuel cell capable of continuously continuing the fuel cell reaction without the need for is there.

  As a result of intensive studies to solve the above problems, the present inventors have provided a fuel chamber for storing at least solid carbon as an apparatus configuration of a solid oxide fuel cell having fuel cells, and the fuel chamber The solid carbon is not supported on the anode material if a solid-state carbon is reacted with carbon dioxide generated by power generation to convert it into carbon monoxide and the power generation method is performed by oxidizing the carbon monoxide. Even if it is molded solid carbon, or even if it is simply stored in the fuel chamber, that is, the solid carbon is separated from the anode, the molded solid carbon is consumed as a fuel, resulting in a continuous We found that power generation is possible.

  Then, in order to take advantage of the above features of the fuel cell, by using “molded solid carbon” as solid carbon, that is, by storing “molded solid carbon” in the fuel chamber, As a result, the present invention has been found.

That is, the present invention
(1-a) an anode having an anode material comprising a composite metal oxide;
(1) a fuel cell comprising: (1-b) a cathode having a cathode material; and (1-c) an electrolyte containing an ion conductive solid oxide disposed between the anode and the cathode.
(2) at least a solid carbon used as a fuel during power generation, and (3) a fuel chamber for storing the solid carbon,
A method for power generation of a solid oxide fuel cell, wherein solid carbon in the fuel chamber is converted into carbon monoxide by reacting with carbon dioxide generated by power generation, and power is generated by oxidizing the carbon monoxide,
A solid oxide fuel cell power generation method is characterized in that the solid carbon used in the solid oxide fuel cell is molded solid carbon.

  Further, the present invention resides in the above power generation method of the solid oxide fuel cell, wherein the shape of the “molded solid carbon” is a core shape, a rod shape, or a tablet shape.

The present invention also resides in the above power generation method for a solid oxide fuel cell, wherein the fuel cell generates power using the following reaction formulas (1) and (2) during power generation.
CO ₂ + C → 2CO (1)
CO + O ²⁻ → CO ₂ + 2e ⁻ (2)

The present invention also provides:
(1-a) an anode having an anode material comprising a composite metal oxide;
(1) a fuel cell comprising: (1-b) a cathode having a cathode material; and (1-c) an electrolyte containing an ion conductive solid oxide disposed between the anode and the cathode.
(2) at least a solid carbon used as a fuel during power generation, and (3) a fuel chamber for storing the solid carbon,
A solid oxide fuel cell that generates electric power by reacting solid carbon in the fuel chamber with carbon dioxide generated by power generation to convert to carbon monoxide and oxidizing the carbon monoxide, wherein the solid carbon is The present invention resides in a solid oxide fuel cell characterized by being formed solid carbon.

  According to the present invention, it is not necessary to introduce an organic compound such as a hydrocarbon into the anode in advance and to have solid carbon supported once on the anode material using a pyrolysis reaction, so that the fuel cell reaction is continuously continued. Therefore, it can be easily applied to a power generation system that requires continuous operation, and the practical application can be promoted.

  Generating power without directly supporting solid carbon on the anode means that the solid carbon stored in the fuel chamber is consumed. That is, it does not require a gaseous fuel as in the prior art, and may require an activation process in which an organic compound such as a hydrocarbon is introduced and a pyrolysis reaction proceeds to directly support solid carbon on the anode. As long as the solid carbon is supplied to the fuel chamber, the fuel cell can be continuously operated, so that a highly practical operation method is possible.

  In addition, even if the solid carbon that is the fuel is not in contact with the anode material, it operates as long as it is stored or filled in the fuel chamber that exists in the vicinity. Therefore, the shape of the solid fuel is “molded solid carbon”. By doing so, it becomes possible to supply fuel to the fuel cells extremely easily compared to the conventional form that requires gas, and even in the case of powder, Applicable not only to stationary solid oxide fuel cells for stores, but also to mobile solid oxide fuel cells for mobile phones, portable cassette players, portable audio players, headphone stereos, personal computers, etc. Become.

It is a schematic cross section which shows an example of the basic composition of embodiment of a solid oxide fuel cell. It is a schematic cross section which shows the basic composition of the solid oxide fuel cell provided with the power generation initiator introduction pipe. FIG. 3 is a schematic cross-sectional view showing an example of a basic configuration of a solid oxide fuel cell in which a power generation initiator introduction pipe passes through a fuel chamber. FIG. 3 is a schematic cross-sectional view showing an example of a basic configuration of a solid oxide fuel cell that is disposed so that a tip of a power generation initiator introduction tube is positioned in a fuel chamber. 1 is a schematic cross-sectional view illustrating an example of a basic configuration of a solid oxide fuel cell according to the present invention having an external control circuit for controlling current density. It is a solid oxide type battery in the present invention, and is a schematic sectional view showing an example of a basic configuration of an embodiment having an electric circuit for electrochemically injecting an oxygen source into an anode. It is a schematic cross section which shows an example of the form of the solid oxide fuel cell in this invention. It is a schematic cross section which shows an example of the form of the solid oxide fuel cell in this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the technical idea thereof.

<Basic configuration of solid oxide fuel cell>
The solid oxide fuel cell of the present invention has at least the following (1), (2) and (3).
(1) Fuel cell (2) Solid carbon used as fuel during power generation (3) Fuel chamber for storing solid carbon

  The fuel cell generates electric power by reacting solid carbon in the fuel chamber with carbon dioxide generated by power generation to convert it into carbon monoxide and oxidizing the carbon monoxide. The material, power generation method, power generation principle, and the like of each part of the fuel cell that make this possible will be described later. First, the basic configuration of the solid oxide fuel cell will be described below.

The (1) fuel cell in the present invention has at least the following (1-a), (1-b) and (1-c).
(1-a) an anode having an anode material comprising a composite metal oxide;
An electrolyte comprising (1-b) a cathode having a cathode material, and (1-c) an ion-conducting solid oxide disposed between the anode and the cathode,

  FIG. 1 is a schematic cross-sectional view showing a basic configuration of an embodiment of a solid oxide fuel cell according to the present invention. The solid oxide fuel cell shown in FIG. 1 has at least a fuel cell 10, a fuel chamber 1, and a “gas inlet containing an oxidizing agent” 33. The fuel battery cell 10 includes at least an anode 11, a cathode 31, and an electrolyte 21 disposed between the anode 11 and the cathode 31. The anode 11 shown in FIG. 1 has an anode material 11b and an anode current collector 11a. Further, the cathode 31 shown in FIG. 1 includes a cathode material 31b and a cathode current collector 31a.

  Further, the solid oxide fuel cell according to the present invention can store solid carbon 2 as fuel, and includes a fuel chamber 1 for supplying the solid carbon 2 to the fuel cell 10. Here, the fuel chamber 1 is a space for storing solid carbon 2 for power generation provided on the anode 11 side, and the solid carbon 2 stored therein does not need to be in contact with the anode 11. However, it is also preferable that at least a part of the solid carbon 2 is in contact with the anode 11. More specifically, in the fuel chamber 1, the solid carbon 2 stored in the fuel chamber 1 is not necessarily in contact with the anode current collector 11a or the anode material 11b, but is in contact with it. It is also preferable.

  In the present invention, it is essential that the solid carbon 2 is molded. That is, the solid carbon 2 as the fuel supplied to the solid oxide fuel cell in the present invention is molded in advance, and the shape of “molded solid carbon” 43 (hereinafter abbreviated as “molded solid carbon” 43). Is stored in the fuel chamber 1. In FIG. 1, the solid carbon 2 is molded into a molded solid carbon 43.

  The shape of the molded solid carbon 43 is not particularly limited, but is easy to supply to the fuel chamber 1, convenient to handle and move, easy to sell, and safer than powder or gas. From the viewpoint of being easily handled, it is preferably a core shape, a rod shape or a tablet shape.

  Although not limited, for example, in FIG. 1, solid carbon 2 is stored in the form of molded solid carbon 43 in about 90% of the lower part of the fuel chamber 1. Even during power generation, power generation can be continued by adding solid carbon 2 as fuel to the fuel chamber 1 in the form of molded solid carbon 43.

It is preferable that oxygen contamination on the anode 11 side be reduced as much as possible from the viewpoint of power generation efficiency. In order to remove oxygen, it is also preferable to store solid carbon 2 that is substituted with an inert gas such as nitrogen (N ₂ ) or carbon dioxide (CO ₂ ), that is, molded solid carbon 43.

If there is solid carbon 2 in the fuel chamber 1 and CO ₂ generated by power generation is present at, for example, 500 to 1000 ° C., the CO generation reaction proceeds and power generation is continued by the fuel cell 10. The present invention has been made on the basis of a new discovery of this surprising fact.

Further, the solid oxide fuel cell shown in FIG. 1 supplies a carbon dioxide (CO ₂ ) outlet 3 for discharging CO ₂ to the anode 11 side and an oxidant such as oxygen (O ₂ ) to the cathode 31 side. For this purpose, a “gas introduction port containing an oxidizing agent” 33 is provided.

FIG. 2 is also a schematic cross-sectional view showing the basic configuration of the solid oxide fuel cell according to the present invention. In addition to the basic configuration shown in FIG. 1, the tip of a power generation initiator introduction tube 13 for supplying a power generation initiator at the start of power generation is disposed on the anode 11 side of the solid oxide fuel cell. In FIG. 2, in particular, the tip of the power generation initiator introduction pipe 13 is disposed between the fuel chamber 1 and the anode 11. Specifically, a power generation initiator introduction pipe 13 is provided in a space excluding the fuel chamber 1 at the carbon dioxide (CO ₂ ) discharge port 3, and the tip of the power generation initiator introduction pipe 13 is connected to the fuel chamber 1 and the anode 11 (specifically, Is disposed between the anode current collector 11a). Since the tip of the power generation initiator introduction pipe 13 is disposed between the fuel chamber 1 and the anode 11, the power generation initiator is supplied in the vicinity of the anode material 11b, and as a result, the initial power generation characteristics are easily stabilized. .

  The basic configuration of the solid oxide fuel cell shown in FIG. 3 is the same as that of the solid oxide fuel cell shown in FIG. 2, but the arrangement of the power generation initiator introduction pipe 13 is different. That is, the power generation initiator introduction pipe 13 penetrates through the fuel chamber 1, and the tip of the power generation initiator introduction pipe 13 is disposed between the fuel chamber 1 and the anode 11. More specifically, it is disposed so as to be positioned between the fuel chamber 1 and the anode current collector 11a. The power generation initiator introducing pipe 13 is provided so as not to overlap with the stored molded solid carbon 43 such as a side surface of the molded solid carbon 43 stored in the fuel chamber 1. As in the above, the initial power generation characteristics are likely to be stable.

  The basic configuration of the solid oxide fuel cell shown in FIG. 4 is the same as that of the solid oxide fuel cell shown in FIGS. 2 and 3, but the position of the tip of the power generation initiator introduction pipe 13 is different. That is, the power generation initiator introduction pipe 13 is disposed so that the tip thereof is located in the fuel chamber 1. Even in this case, since the power generation initiator is gradually supplied to the anode 11, the same effect as described above can be obtained.

  FIG. 5 is also a schematic cross-sectional view showing the basic configuration of the solid oxide fuel cell according to the present invention. In addition to the basic configuration of the solid oxide fuel cell shown in FIG. 1, an external control circuit 22 for controlling the current density of the solid oxide fuel cell is provided.

  FIG. 6 is also a schematic cross-sectional view showing the basic configuration of the solid oxide fuel cell according to the present invention. In addition to the basic structure of the solid oxide fuel cell shown in FIG. 1, an electric circuit 23 for electrochemically injecting an oxygen source into the anode 11 is provided. In the power generation method of the solid oxide fuel cell according to the present invention, it is preferable to electrochemically inject an oxygen source into the anode 11 at the start of power generation from the viewpoint of stabilizing the initial power generation characteristics. The oxygen source is not particularly limited, and specific examples include air and oxygen.

The method for electrochemically injecting the oxygen source is not particularly limited. Specifically, for example, the Nernst potential of the battery cell is used between the anode 11 and the cathode 31, and the current density is 0.01 mA / It flows at a rate of cm ^{2 to 5} mA / cm ² , and oxygen takes in electrons at the cathode 31 to become oxide ions (O ²⁻ ). This O ²⁻ moves through the electrolyte and reacts with the fuel at the anode 11 to release electrons. It is preferable to start the electrode reaction. If the oxygen source is not electrochemically injected into the anode 11 at the start of power generation, stable power generation may not be obtained at the initial stage of power generation.

<(1-a) Anode>
The anode material 11b of the anode 11 includes a composite metal oxide. That is, the anode material 11b may include a composite metal oxide or may include cermet. Here, “cermet” means a mixture of metal and metal oxide powder and sintered. The composite metal oxide or cermet is preferably porous. As the composite metal oxide or cermet, those generally used as an anode active material in known solid oxide fuel cells can be suitably used.

[Composite metal oxide]
The composite metal oxide used as a component of the anode material 11b and also as a raw material of the cermet that is a component of the anode material 11b is generally used as an anode active material in a solid oxide fuel cell. If there is no particular limitation. From the viewpoint of reliably obtaining sufficient output characteristics, durability, etc. during power generation, stabilized zirconia (Y ₂ O ₃ —ZrO ₂ ) containing yttria (hereinafter abbreviated as “YSZ”); Gd , La, Y, Sm, Nd, Ca, Mg, Sr, Ba, Dy and Yb doped with at least one kind of CeO ₂ [Of these, CeO ₂ doped with Gd (hereinafter, Sg-doped CeO ₂ is preferred]; Sc ₂ O ₃ —ZrO ₂ (hereinafter abbreviated as “ScSZ”); Sm ₂ O ₃ —CeO ₂ (hereinafter “SDC”) Are abbreviated to be particularly preferable.

In the case of the _{YSZ, (the} content of Y 2 _{O 3)} ratio of Y 2 _{O 3,} it is preferred for Y ₂ O 3 -ZrO ₂ is 8-10 mol%. In addition, in the case of the GDC, (content of Gd) proportion of Gd is preferably 3 to 40 mol% based on doped CeO _2, more preferably 8 to 40 mol%, further 10 to 40 mol% Preferably, it is 15-40 mol%, and it is especially preferable. Furthermore, in the case of CeO ₂ doped with Sm, the ratio of Sm (content of Sm) is preferably 15 to 40 mol% with respect to doped CeO ₂ . Particularly preferable ceria-based solid solutions include Ce _0.8 Gd _0.2 O _2-δ (where δ represents the amount of oxygen deficiency), Ce _0.67 Gd _0.33 O _2-δ (wherein , Δ represents the amount of oxygen deficiency).

In addition, it is preferable to use a composite metal oxide having electrical conductivity from the viewpoint of obtaining sufficient output characteristics during power generation. The conductivity of the composite metal oxide is particularly preferably 0.01 to 10 Scm ⁻¹ at 1000 ° C.

[[cermet]]
From the viewpoint of more reliably obtaining the effects of the present invention and more reliably obtaining excellent output characteristics, the anode material 11b is preferably cermet. The cermet is not particularly limited as long as it is generally used as an anode active material in a solid oxide fuel cell, but at least selected from the group consisting of Ni, Pt, Au, Cu, Fe, W and Ta. A cermet of one kind of metal and a composite metal oxide (particularly the composite metal oxide) is preferred. From the point of ensuring sufficient output characteristics during power generation, etc., cermets of nickel and composite metal oxides are preferred, and in particular, cermets of nickel and the above composite metal oxides are preferred. It is mentioned as a thing.

  Particularly preferably, in terms of output characteristics, cermet of nickel and YSZ (hereinafter abbreviated as “Ni / YSZ”), cermet of nickel and GDC (hereinafter abbreviated as “Ni / GDC”), nickel, It is a cermet with ScSZ (hereinafter abbreviated as “Ni / ScSZ”) or a cermet with nickel and SDC (hereinafter abbreviated as “Ni / SDC”).

Moreover, it is preferable from the point of ensuring electronic conductivity that the volume fraction V1 of the metal in a cermet and the volume fraction V2 of a composite metal oxide satisfy | fill the conditions represented by a following formula.
0.2 ≦ [V1 / (V1 + V2)] ≦ 0.8

  Here, if [V1 / (V1 + V2)] is less than 0.2, sufficient electron conductivity in the anode material 11b cannot be secured, and the output characteristics of the solid oxide fuel cell may be insufficient. . Further, if [V1 / (V1 + V2)] exceeds 0.8, the ion conductivity in the anode material 11b cannot be sufficiently secured, and the output characteristics of the solid oxide fuel cell 1 may be insufficient. . [V1 / (V1 + V2)] is preferably 0.2 to 0.8, and preferably 0.3 to 0.7 from the viewpoint of sufficiently ensuring both the electron conductivity and the ionic conductivity in the anode material 11b. Particularly preferred is 0.4 to 0.6.

  Specifically, in Ni / YSZ, Ni / GDC, Ni / ScSZ, or Ni / SDC, the value of Ni / (such composite metal oxide + Ni) falls within the above range as the volume fraction ratio. Is preferred.

[[Composite metal oxide with electrical conductivity]]
Here, when the anode material 11b is a material containing metal particles or alloy particles such as cermet, the metal in the anode causes generation of carbides and carbon whiskers, which causes long-term electrode deterioration. There is. That is, when carbon dissolved in the metal precipitates and grows, the metal particles are dropped from the frame structure of the electrode, which may cause deterioration of the electrode. Moreover, the volume expansion / contraction of the metal particles during the redox cycle may cause electrode deterioration. Therefore, it is also preferable to use a composite metal oxide having electrical conductivity instead of the cermet as the anode material 11b.

By using a composite metal oxide having electrical conductivity for at least one anode material of the anode material 11b in place of the cermet containing metal particles or alloy particles that cause electrode degradation, the cause of electrode degradation described above. Is eliminated, anode deterioration during operation of the RDCFC is suppressed, redox cycle characteristics are improved, and high output can be stably maintained. The anode material 11b preferably contains a composite metal oxide having electrical conductivity. Here, “having electrical conductivity” means that the electrical conductivity is 10 ⁻⁴ Scm ⁻¹ or more at the operating temperature.

  Here, a metal may be contained within a range in which the above-described electrode deterioration does not occur, and the present invention does not exclude the inclusion of a small amount of “metal particles or alloy particles” from the composition of the anode material 11b. . The total amount of “metal particles or alloy particles” contained in the anode material 11b is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less, including both metal particles and alloy particles. More preferably not.

The electric conductivity of the above-mentioned “complex metal oxide having electric conductivity” is preferably 10 ⁻² Scm ⁻¹ or more, particularly preferably 10 ⁻¹ Scm ⁻¹ or more, at the operating temperature. Here, “electric conduction” means electric conduction consisting of at least one of electron conduction, hole conduction, oxide ion conduction and proton conduction, that is, one or more of them are combined. Means electrical conduction. If the electrical conductivity is too low, sufficient output characteristics may not be obtained.

  The anode of the solid oxide fuel cell according to the present invention does not contain metal particles or alloy particles, or contains metal particles or alloy particles up to a range in which a three-dimensional network is not formed. It is preferable. The “three-dimensional network” refers to a state in which electrical conduction is possible through the thickness direction of the anode. If a three-dimensional network is formed of metal particles or alloy particles, the anode may deteriorate as a result of repeated expansion and contraction of the anode material due to repeated oxidation and reduction.

  In addition, the composite metal oxide having electrical conductivity used for the anode material 11b of the solid oxide fuel cell in the present invention itself forms a three-dimensional network, that is, the composite metal oxide itself. Thus, it is preferable to form a three-dimensional network capable of conducting electrons in that good electrical conductivity can be realized and as a result, sufficient output characteristics can be obtained.

  At least one of the composite metal oxides having electrical conductivity used for the anode material 11b of the solid oxide fuel cell according to the present invention has a perovskite crystal structure, a pyrochlore crystal structure, or a fluorite crystal structure. It is preferable that the composite metal oxide is included.

The composite metal oxide having a perovskite crystal structure refers to a composite metal oxide having a so-called perovskite crystal structure, and a composite metal oxide represented by the following general formula (G) is preferable.
A _{1 ± a} B _{1 ± b} O _3-δ (G)
[In the composition formula (G), A represents La, Sr, Ca, Y, Ba, Pr, Ce, K, Na, Sm, Pb, Nd, Gd, Bi, Ag, Cs, Rb, Tl, Cd, Eu. , Mg, Dy, Li, and Ho, B represents Co, Cr, Mn, Ni, Ce, Gd, Al, Ti, Zr, Sc, Mg, Ga, Cu, Fe Yb, Y, Nb, I, Ni, Sr, Bi, In, Ca, Sn, Ta, W, Th, U, Hf, Mo, Lu, Tm, Tb, Dy, Ho, Os, Rh, Ag, Tr , Sb, Zn, Pa, In, Re, and Er, at least one selected from the group consisting of 0 ≦ a ≦ 0.2 and 0 ≦ b ≦ 0.2, and δ is the amount of oxygen deficiency. ]

Of these, substances based on LaMnO ₃ , LaCoO ₃ , LaCrO _{3 and the} like are more preferable. For example, (LaSr) MnO ₃ -based composite metal oxide (in the present invention, this is abbreviated as “LSM”), ( LaSr) CoO ₃ -based composite metal oxide (in the present invention, this is abbreviated as “LSC”) is particularly preferable.

  Moreover, in compositional formula (G), it is preferable for B to contain 50 mol% or more of Mn with respect to the whole B in order to exhibit the said effect more. Further, in the composition formula (G), B contains 50 mol% or more of Co with respect to the entire B, or B contains Co and Fe in total of 50 with respect to the entire B. It is preferable for the content to be at least mol% in order to achieve the above effects.

Other composite metal oxides having a perovskite crystal structure are represented by the general formula A (B _1-x M _x ) _{1 ± a} O _3-δ [where 0 ≦ x ≦ 0.8, 0 ≦ a ≦ 0. .2], A is at least one selected from divalent cations such as Ba, Sr, and Ca, B is at least one selected from tetravalent cations such as Ce, Zr, and Ti, and M Is at least one selected from trivalent rare earth, Y, Sc, In, Yb, Nd, Gd, Al, Ga and the like.

For example, Ba (Ce _1-x Gd _x ) _{1 ± a} O ₃ [where 0 ≦ x ≦ 0.8, 0 ≦ a ≦ 0.2], Ca (Al _1-x Ti _x ) _{1 ± a} O ₃ [wherein, 0 ≦ x ≦ 0.8,0 is _{≦ a ≦ 0.2], Sr (} Ce 1-x Yb x) in _{1 ±} a _{O 3} (wherein, 0 ≦ x ≦ 0. 8, 0 ≦ a ≦ 0.2), Sr (Zr _1−x Y _x ) _{1 ± a} O ₃ (where 0 ≦ x ≦ 0.8, 0 ≦ a ≦ 0.2), Those represented by Sr (Zr _1-x Sc _x ) _{1 ± a} O ₃ (where 0 ≦ x ≦ 0.8, 0 ≦ a ≦ 0.2) are also preferred. Specifically, BaCe _0.9 Gd _0.1 O ₃ , CaAl _0.7 Ti _0.3 O ₃ , SrCe _0.95 Yb _0.05 O ₃ , SrZr _0.95 Y _0.05 O ₃ , SrZr _0.9 Sc _0.1 O _{3 and the} like.

_{Formula, La 1-x Sr x Ga} 1-y-z Mg y M z O 3 [ wherein, M represents, Co, Fe, indicates any one or more elements of Ni or Cu, x = 0. It is the range of 05-0.3, y = 0-0.29, z = 0.01-0.3, y + z = 0.025-0.3. The lanthanum gallate represented by the formula is also preferable. Specific examples include La _0.8 Sr _0.2 Ga _0.8 Mg _0.15 Co _0.05 O _3-δ (where δ represents the amount of oxygen deficiency).

Specific examples of the composite metal oxide having preferable electrical conductivity include La _0.8 Sr _0.2 MnO ₃ , La _0.85 Sr _0.15 MnO ₃ , and La _0.95 Sr _0.05. La _1-b Sr _b MnO [b is 0 ≦ b ≦ 0.5], such as MnO ₃ ; La _0.8 Sr _0.2 CoO ₃ , La _0.85 Sr _0.15 CoO ₃ La _1-d Sr _d MnO ₃ [d is 0 ≦ d ≦ 0.5], such as La _0.95 Sr _0.05 CoO ₃ ; La _0.6 Sr _0.4 Fe _{0. 8 Co 0.2 O 3, La 0.6} Sr 0.4 Fe 0.2 Co 0.8 La 1-e Sr of _{O 3, e Fe f Co 1-f O} 3 [e is 0 ≦ e ≦ 0 .5, f is a compound represented by 0 ≦ f ≦ 1]; La _0.75 Sr _{0. 2} Cr _0.5 Mn _0.5 O _{3 and} other La _1-g Sr _g Cr _1-h Mn _h O ₃ [g is 0 ≦ g ≦ 0.5, h is 0 ≦ h ≦ 1] And the like.

The composite metal oxide having a pyrochlore crystal structure refers to a composite metal oxide having a so-called pyrochlore crystal structure, Ln ₂ ((Zr _1−x Ti _x ) ₂ ) _{1 ± a} O ₇ (wherein Ln represents one or more elements selected from the group consisting of Sc, Y, La and other lanthanoids, and 0 ≦ x ≦ 0.5 and 0 ≦ a ≦ 0.2) are preferred. . Specifically, for example, Gd ₂ ((Zr _1-x Ti _x ) ₂ ) _{1 ± a} O ₇ (where 0 ≦ x ≦ 0.5, 0 ≦ a ≦ 0.2), Y ₂ ( (Zr _1-x Ti _x ) ₂ ) _{1 ± a} O ₇ (where 0 ≦ x ≦ 0.5, 0 ≦ a ≦ 0.2).

The composite metal oxide having a fluorite-type crystal structure refers to a composite metal oxide having a so-called fluorite-type crystal structure. Among them, a ceria-based composite metal oxide is preferable, and Ce _1-x M _x O ₂ (wherein M is selected from the group consisting of Gd, La, Y, Sc, Sm, Pr, Nd, Ca, Mg, Sr, Ba, Dy, Yb, Tb and other divalent or trivalent lanthanoids) 1 or more elements, and 0 ≦ x ≦ 0.5). Particularly preferred ceria-based composite metal oxides include Ce _0.8 Gd _0.2 O _2-δ (where δ represents the amount of oxygen deficiency).

  As the composite metal oxide having electrical conductivity used for the anode material 11b of the solid oxide fuel cell in the present invention, the composite metal oxide having a perovskite crystal structure does not contain metal particles or alloy particles. Is particularly preferable in that it has high electrical conductivity and exhibits the effects of the present invention described above.

When the anode material 11b is a composite material composed of two or more kinds of anode materials, the anode material other than the above is also preferably a composite metal oxide. Further, in the anode, two or more kinds of composite metal oxides having at least one of electron conductivity and hole conductivity and composite metal oxides having at least one of oxide ion conductivity and proton conductivity are used. Preferably it contains an anode material. Here, “having at least one of electron conductivity and hole conductivity” means that the combined electric conductivity is 10 ⁻⁴ Scm ⁻¹ or more, and “at least oxide ion conductivity. "Having either proton conductivity or proton conductivity" means that the combined electrical conductivity is 10 ⁻⁴ Scm ⁻¹ or more.

Preferred anode material 11b in the present invention is that LSM / GDC, which is a composite material of LSM and GDC, LSC alone, and a composite of LSC and GDC in that it has both relatively high electronic conductivity and oxide ion conductivity. Examples thereof include LSC / GDC which is a material. In addition, a composite material of LSM and SrCe _1-i Yb _i O ₃ (i is 0 ≦ i ≦ 1) (hereinafter abbreviated as “SCYb”) in that it has both electron conductivity and proton conductivity. And LSC / SCYb, which is a composite material of LSC and SCYb. In addition to “LSM or LSC”, GDC and SCYb composite material “LSM or LSC” / GDC / SCYb, etc. in terms of having proton conductivity in addition to electron conductivity and oxide ion conductivity. .

[Film thickness]
The thickness of the anode material 11b is not particularly limited, but is usually 10 μm to 5 mm, preferably 20 μm to 1 mm, more preferably 30 μm to 700 μm, still more preferably 40 μm to 400 μm, and most preferably 50 μm to 150 μm. The film thickness may be measured by a stylus type surface roughness meter or cross-sectional observation by SEM.

  Note that the optimum thickness of the anode 11 (fuel electrode) mentioned here varies depending on the porosity. That is, since the porosity affects the ease of gas diffusion to the anode 11 and the ease of movement of the generated carbon monoxide (CO) gas to the effective reaction site, the thickness changes as the porosity changes. Optimum conditions may vary. Therefore, it is preferable to determine the thickness of the anode 11 as appropriate in accordance with the porosity of the obtained anode 11.

[Power generation initiator]
When using the solid oxide fuel cell according to the present invention, a power generation initiator is introduced (hereinafter also referred to as “power generation initiator introduction process”) and a power generation (hereinafter also referred to as “power generation process”). At least exists. When introducing a power generation initiator, it is preferable to start power generation by supplying a power generation initiator to the anode 11 in terms of easy stabilization of initial power generation characteristics. Here, the “power generation initiator” refers to carbon monoxide or carbon dioxide. In the power generation initiator introduction step, a power generation initiator is supplied, and carbon monoxide or carbon dioxide is brought into contact with the solid carbon 2 in the fuel chamber 1.

  As the means for introducing the power generation initiator, for example, as shown in FIGS. 2, 3, and 4, it is preferable to install a power generation initiator introduction pipe 13 for supplying the power generation initiator at the start of power generation. The tip of the power generation initiator introduction pipe 13 may be arranged at any position as long as the power generation initiator reaches the anode 11, but as shown in FIG. 2 or FIG. It is preferable that the power generation initiator is provided between the anode 11 in a quick and reliable manner.

[Anode mechanism, structure, physical properties, etc.]
At the time of power generation (in the power generation process), the solid carbon 2 supplied to the fuel chamber 1 is used, and electrons are generated at least according to the following reaction formulas (1) and (2). At the same time, the cathode 31 donates electrons to the oxidizing gas and injects ionized oxide ions (O ²⁻ ) into the electrolyte 21.

There is no particular limitation on the size of the solid oxide fuel cell according to the present ^invention, it is particularly preferable preferably from 1 cm 3 to 500m ^3, a 1000cm ³ ~50000cm 3.

  The output during power generation of the solid oxide fuel cell in the present invention is not particularly limited, but is preferably 0.001 kW to 500 kW, particularly preferably 0.01 kW to 100 kW, and preferably 0.01 kW to 10 kW. Further preferred. The solid oxide fuel cell of the present invention can generate the output when the size is the above.

  As long as the constituent material of the anode current collector 11a of the anode 11 is electronically conductive and is chemically and physically stable in the operating temperature region of the solid oxide fuel cell, its shape and constituent material are It does not specifically limit, The thing similar to what is equipped in the well-known solid oxide fuel cell can be used. Those which are chemically and physically stable at 600 ° C. to 1200 ° C. are preferred.

  The anode current collector 11a also functions as a separator disposed between the unit cells when a plurality of fuel battery cells 10 are stacked.

  The anode 11 has a gas supply port (not shown) and a discharge port (not shown), and an internal gas flow path (not shown) connected to the supply port and the discharge port. It may be provided. The solid oxide fuel cell according to the present invention is completely different from a general known fuel cell in the type of fuel, the method of use, the principle of power generation, etc., but the gas supply port and discharge port, and the supply port and discharge port As the mechanical external structure such as the internal flow path of the gas connected to, a structure similar to that of a general known fuel cell can be used.

  In the solid oxide fuel cell according to the present invention, it is preferable that substantially no carrier gas for releasing the reaction product gas to the anode 11 is substantially introduced during power generation. As will be described later, it is preferable that the carrier gas is not substantially introduced because the reaction represented by the reaction formula (1) occurs more efficiently at the anode 11. This also makes the device configuration much more compact during power generation.

<(1-b) Cathode>
At the time of power generation, the cathode 31 is supplied with “a gas containing an oxidizing agent (for example, oxygen)” (for example, air), and the cathode material 31b serves as a reaction field in which the reduction reaction of the oxidizing agent proceeds. The composition and shape of the cathode material 31b are not particularly limited, and those similar to those generally used for the cathode 31 provided in a known solid oxide fuel cell can be used. For example, a material composed of (LaSr) MnO ₃ -based or (LaSr) CoO ₃ -based composite metal oxide can be preferably used. Particularly preferable examples include La _0.85 Sr _0.15 MnO ₃ .

  The configuration of the cathode current collector 31a of the cathode 31 is the same as that of the anode current collector 11a of the anode 11 described above, and the constituent material and shape are not particularly limited, and are provided for a known solid oxide fuel cell. The same ones can be used. The cathode current collector 31a is formed with a gas flow path (not shown) for supplying a gas containing an oxidizing agent such as air to the cathode material 31b. The cathode current collector 31a also functions as a separator disposed between the unit cells when a plurality of fuel battery cells 10 are stacked.

<(1-c) Electrolyte>
The electrolyte 21 includes an ion conductive solid oxide. The electrolyte 21 is not only a moving medium for oxide ions (O ²⁻ ), but also a partition wall for preventing a reducing agent (the solid carbon 2 described above) and a gas containing an oxidizing agent (for example, air) from being in direct contact with each other. It functions and has a gas impermeable dense structure. The constituent material of the electrolyte 21 is not particularly limited, and a material used for a known solid oxide fuel cell can be used. However, the oxide 21 has a high conductivity of the oxide ion, and the anode 31 from the oxidizing atmosphere on the cathode 31 side. It is preferable to use a material that is chemically stable and resistant to thermal shock under conditions up to the reducing atmosphere on the 11th side.

Examples of materials that satisfy such requirements include yttria stabilized zirconia (YSZ),
Preferred examples include stabilized zirconia such as scandia-stabilized zirconia (ScSZ); lanthanum gallate; ceria-based solid solution.

Stabilized zirconia is not particularly limited, but the following general formula (ZrO ₂ ) _1-x (M ₂ O ₃ ) _x
[Wherein M represents one or more elements selected from the group consisting of Y, Sc, Sm, Al, Nd, Gd, Yb and Ce. However, here, when M is Ce, it is CeO ₂ instead of M ₂ O ₃ . Or the following general formula (ZrO ₂ ) _1-x (MO) _x
In the formula, M is preferably a solid solution in which x is 0 <x ≦ 0.3 in M represents one or more elements selected from the group consisting of Ca and Mg. Particularly preferable examples include (ZrO ₂ ) _1-x (Y ₂ O ₃ ) _x (where 0 <x ≦ 0.3), and more preferably 0.08 ≦ x ≦ 0.1. More preferable examples include (ZrO ₂ ) _0.92 (Y ₂ O ₃ ) _0.08 .

  For example, the expression “in the formula, A represents one or more elements selected from the group consisting of Q, R and T” is a solid solution in which A is Q and a solid solution in which A is R. In addition, the solid solution having Q and R simultaneously at the crystal site as A is also shown. The same applies hereinafter.

Although lanthanum gallate is not particularly limited, general _formula, La in _{1-x Sr x Ga 1-} y-z Mg y A z O 3 ( wherein, A is Co, Fe, any one or more of Ni or Cu Element is represented by x = 0.05 to 0.3, y = 0 to 0.29, z = 0.01 to 0.3, y + z = 0.025 to 0.3). A solid solution is preferred. Specific examples include La _0.8 Sr _0.2 Ga _0.8 Mg _0.15 Co _0.05 O _3-δ (where δ represents the amount of oxygen deficiency).

The ceria-based solid solution is not particularly limited, but Ce _1-x M _x O ₂ (wherein M is Gd, La, Y, Sc, Sm, Al, Pr, Nd, Ca, Mg, Sr, Ba, Dy, A solid solution in which x is 0 <x ≦ 0.5 in Yb, Tb, and one or more elements selected from the group consisting of other divalent or trivalent lanthanoids) is preferable. Among them, Ce _1-x Gd _x O ₂ where M is Gd (where 0 <x ≦ 0.5), or Ce _1-x Sm _x O ₂ where M is Sm (where 0 <x ≦ 0.5) is more preferable, and in any formula, 0.03 ≦ x ≦ 0.4 is particularly preferable, 0.08 ≦ x ≦ 0.4 is further preferable, and 0.1 ≦ x ≦ 0.4. 0.4 is most preferred. Particularly preferable ceria-based solid solutions include Ce _0.8 Gd _0.2 O _2-δ (where δ represents the amount of oxygen deficiency), Ce _0.67 Gd _0.33 O _2-δ (wherein , Δ represents an oxygen deficiency amount), Ce _0.9 Gd _0.1 O _2-δ (where δ represents an oxygen deficiency amount), and the like. In particular, it is preferable to use GDC as the material of the electrolyte 21 because the output density can be sufficiently increased even when the temperature during power generation is 750 ° C. or lower.

Moreover, from the viewpoint of obtaining sufficient output characteristics during power generation, the conductivity of the composite metal oxide is preferably 0.01 to 10 Scm ⁻¹ at 1000 ° C.

<Method for producing fuel cell>
The manufacturing method of the fuel cell 10 in the present invention is not particularly limited, and a known thin film manufacturing technique applied to manufacturing a known solid oxide fuel cell can be used. For example, a squeegee method, a screen printing method, a vacuum deposition method, a sputtering method, a PVD method such as an ion plating method, a CVD method such as a thermal CVD method, a plasma CVD method, and a laser CVD method, a thermal spraying method, and the like.

  As a method of forming the electrolyte 21, for example, a sheet forming and sintering method which is a known ceramic process can be exemplified. More specifically, the slurry obtained by mixing the raw material and the solvent is extended into a sheet shape, dried, and then shaped and fired as necessary using a cutter knife or the like. You may mix | blend well-known additives, such as a binder, a plasticizer, a dispersing agent, with a slurry as needed. Conditions such as molding and firing can be appropriately set according to the composition of the raw material. Moreover, the layer of the electrolyte 21 can be formed on the anode 11 or the cathode 31, for example, by a thin film forming method such as the PVD method, the CVD method, or the spraying method described above.

<Form of solid oxide fuel cell>
The solid oxide fuel cell according to the present invention includes at least (1) a fuel cell 10, (2) solid carbon 2 used as fuel during power generation, and (3) a fuel chamber 1 that stores the solid carbon 2. Have.

  7 and 8 show an example of the form of the solid oxide fuel cell according to the present invention. A gas inlet 33 containing an oxidant is provided below the fuel cell 10, and “a gas containing an oxidant such as air” can be supplied to the cathode 31 (see FIGS. 1 to 6) below the fuel cell 10. It is like that. Further, in FIG. 7, there is a fuel chamber 1 for storing molded solid carbon 43 serving as fuel on the fuel battery cell 10, that is, on the anode 11 side of the fuel battery cell 10. It can be put in the room 1.

  In FIG. 7, there is a partition network 42 between the fuel cell 10 and the molded solid carbon 43, and the molded solid carbon 43 directly contacts the anode current collector 11 a and the anode material 11 b of the fuel cell 10 and is damaged. However, the partition 42 is not essential. The partition net 42 can pass a gas such as carbon monoxide (CO), and all the gas can contact the solid carbon 2.

The fuel chamber 1 has a carbon dioxide (CO ₂ ) discharge port 3 so that carbon dioxide (CO ₂ ) can be discharged to the outside. In addition, the fuel chamber 1 including the carbon dioxide (CO ₂ ) discharge port 3, the molded solid carbon storage port (not shown), and the like has a gas containing an oxidant such as air from the outside. Cannot be reached.

  Moreover, it is preferable that the tip of the power generation initiator introduction pipe 13 for supplying the power generation initiator at the start of power generation is disposed on the anode 11 side of the fuel cell 10, as shown in FIGS. Further, it is particularly preferable that the fuel chamber 1 is disposed between the fuel chamber 1 and the anode 11.

  As shown in FIG. 7, there is an external control circuit 22 that operates a solid oxide fuel cell while increasing the current density from its initial value immediately after the start of power generation, or electrochemically supplies to the anode 11 at the start of power generation. It can be used for the purpose of injecting an oxygen source and taking out the generated electric power.

  In FIG. 8, there is a storage chamber 45 for preliminary molded solid carbon, in which preliminary molded solid carbon 44 is stored. The preliminary molded solid carbon 44 can be moved from the preliminary molded solid carbon storage chamber 45 to the fuel chamber 1 when the molded solid carbon 43 is consumed or almost exhausted. . During the movement, gas containing an oxidant such as air from the outside cannot substantially reach the anode of the fuel cell 10, and gas such as carbon monoxide (CO) does not leak to the outside. It is like that.

  The method for adding the solid carbon 2 during the power generation is not particularly limited, but a method of adding the solid carbon 43 from the top of the fuel chamber 1 by stacking, for example, or the like, as shown in FIG. The solid carbon 44 is stored, and when the solid carbon 2 is consumed, it is replaced with the preliminary solid carbon 44 (additional storage of the preliminary solid carbon 44).

  The solid carbon 2 in the molded solid carbon 43 supplied as fuel or the solid carbon 2 before molding refers to a solid containing carbon, where “carbon” is a crystalline simple substance such as amorphous carbon or graphite. Refers to carbon. The solid carbon 2 is not specifically limited, but natural graphite, artificial graphite, carbon black (furnace black, channel black, acetylene black, lamp black, etc.), crystalline carbon such as graphite chalk, fullerene; charcoal, And carbon derived from animals and plants such as bamboo charcoal and ink; chimney smoke; coke; and carbon fine particles in particulate matter (generally also referred to as “PM”) contained in exhaust gas.

  The carbon content in the molded solid carbon 43 is not particularly limited, but it is preferably 50% by mass or more for good power generation of the solid oxide fuel cell. More preferably, it is 70 mass% or more, Most preferably, it is 90 mass% or more. “Carbon content” refers to the content (mass%) of carbon atoms (C) relative to the entire solid solid carbon.

  The shape of the molded solid carbon 43 is not particularly limited as long as it is not a powder but a molded shape. However, the shape of the molded solid carbon 43 may be a core, a rod, or a tablet in Preferred for the reasons described. The size of the molded solid carbon 43 is not particularly limited, and a shape such as a mechanical pencil core or chalk is also preferable.

  A molding method is not particularly limited, and a known method is used. In molding, a binder such as an organic polymer; a binder such as tar and pitch can be used in combination.

  It is preferable that the gas permeates through the storage portion of the molded solid carbon 43 and the inside of the molded solid carbon 43. For this purpose, it is preferable to secure the gas flow path by making the molded solid carbon 43 itself porous or by providing a through hole or a groove.

<Driving method>
The operation method of the solid oxide fuel cell according to the present invention includes at least a power generation step of supplying a gas containing an oxidant such as air to the cathode 31 and generating power using the continuously supplied solid carbon 2 as a reducing agent. If it is a method, it will not specifically limit. If necessary, continuous operation is possible as long as the solid carbon 2 continues to be supplied after the step of supplying the power generation initiator such as carbon monoxide to the solid carbon 2 in the fuel chamber 1 to start the cell reaction. is there.

  The method for introducing the power generation initiator is not particularly limited, and an extremely small amount of carbon monoxide or carbon dioxide may be instantaneously flowed to the solid carbon 2 in the fuel chamber 1. The inflow amount of the reaction initiator is not particularly limited as long as it is sufficient to start the battery reaction. It is also preferable to electrochemically inject an oxygen source into the anode 11 at the start of power generation.

  The method of supplying the solid carbon 2 is very simple because it is sufficient to store the molded solid carbon 43 directly in the fuel chamber 1 and an activation step as described in the conventional known document 2 is unnecessary. .

In the power generation method of the solid oxide fuel cell according to the present invention, it is preferable for stable power generation to operate while increasing the current density from its initial value immediately after the start of power generation. Immediately after the start of power generation, gradually increasing the current density is particularly preferable for stable power generation. “Slowly increasing the current density” usually means increasing at a rate of 0.008 mA / cm ² to ² mA / cm ² per minute, and particularly preferably 0.016 mA / cm ^{2 to 1} mA / min per minute. cm ² . Outside this range, the initial power generation characteristics may not be stable.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the solid oxide fuel cell according to the present invention may have, for example, a form in which a plurality of the solid oxide fuel cells shown in FIGS.

In the present invention, the solid carbon 2 in the fuel chamber 1 is converted into carbon monoxide by reacting with carbon dioxide generated by power generation, and power is generated by oxidizing the carbon monoxide. In particular, at the time of power generation, the anode 11 generates power using at least the following reaction formulas (1) and (2).
CO ₂ + C → 2CO (1)
CO + O ²⁻ → CO ₂ + 2e ⁻ (2)

  By using the reaction formula (1), the solid carbon 2 supplied in the vicinity of the anode 11 is converted into gaseous CO and consumed as fuel, so that the influence of the location of the solid carbon 2 during power generation is extremely low. It becomes possible to make it smaller. That is, in a solid oxide fuel cell, the electrode reaction closer to the surface of the electrolyte 21 generally has a greater contribution to power generation, so the solid carbon 2 distributed far from the surface of the electrolyte 21 is less likely to be consumed. Therefore, a high fuel utilization rate is obtained as compared with the case where the reaction represented by the reaction formula (1) does not occur, and power generation is possible even when the solid carbon 2 is supplied to a position away from the anode 11.

In addition, the CO oxidation reaction according to the reaction formula (2) has a higher reaction rate than the solid carbon 2 oxidation reaction according to the following reaction formula (3) or the following reaction formula (4), so that a high output density can be obtained. In order to cause the reaction formula (2) to dominate, for example, the reaction product gas is not released outside the anode 11 beyond the pressure increase due to the reaction product gas, and the reaction formula (1) or the reaction formula (3) is used. Examples include increasing the time during which the produced carbon monoxide (CO) stays in the anode 11 and suppressing consumption due to oxidation of carbon monoxide (CO) caused by oxygen flowing from outside the system.
C + O ²⁻ → CO + 2e ⁻ (3)
C + 2O ²⁻ → CO ₂ + 4e ⁻ (4)

  In the power generation method of the solid oxide fuel cell in the present invention, it is preferable that 50 mol% or more of carbon monoxide (CO) consumed in the reaction formula (2) is generated in the reaction formula (1). That is, it is preferable that 50 mol% or more of carbon monoxide consumed during power generation is carbon monoxide generated by the reaction between the solid carbon 2 and carbon dioxide. Especially preferably, it is 60 mol% or more, More preferably, it is 70 mol% or more.

  Moreover, in the power generation method of the solid oxide fuel cell according to the present invention, it is preferable that 50% or more of the charge transfer amount is due to the oxidation of carbon monoxide obtained by the reaction between the solid carbon 2 and carbon dioxide. .

  Means for causing the reaction formula (2) to dominate is caused by extending the residence time of CO produced in the reaction formula (1) or the reaction formula (3) in the anode 11 or by oxygen flowing from outside the system. In order to suppress consumption due to oxidation of CO, for example, blocking inflow of oxygen can be mentioned. When a carrier gas is passed through the anode 11 as in a conventional method, the reaction formula (2) hardly occurs.

In order to cause the reaction represented by the reaction formula (1) in the anode 11, it is important to retain the CO ₂ produced in the electrode reaction (2) and / or (4) in the anode 11 for a long time. It is preferable to eliminate the introduction of carrier gas during power generation. In order to eliminate the introduction of the carrier gas, it is preferable to reduce the leakage of air, that is, oxygen from outside the system as much as possible by improving the sealing performance and preventing the voltage drop due to the increase of the oxygen partial pressure.

  In the power generation step, the gas containing the oxidant supplied to the cathode 31 is preferably air from the viewpoint of availability. From the same viewpoint, the oxidizing agent is preferably oxygen.

  From the viewpoint of improving the charge transfer amount and power density of the solid oxide fuel cell during power generation, it is preferable not to supply a carrier gas for releasing the reaction product gas in the anode 11 to the anode 11. .

  In the solid oxide fuel cell of the present invention, the temperature in the power generation step is preferably 400 to 1000 ° C, more preferably 450 to 900 ° C, and particularly preferably 500 to 750 ° C. If the temperature is too low, the reaction formula (1) is difficult to proceed, and the resistance of the cell (electrode and electrolyte) increases, which may reduce the output density. On the other hand, if it is too high, the cell and peripheral members may be deteriorated quickly.

The solid oxide fuel cell according to the present invention can have a power generation temperature of 750 ° C. or lower and a power density of 50 (mW / cm ² ) or higher. In addition, a solid oxide fuel cell whose composition, structure, setting, etc. are adjusted so that the power density is 50 (mW / cm ² ) or more is preferable. In particular, by using GDC as the electrolyte 21, even when the temperature during power generation is 750 ° C. or lower, the output density can be 50 (mW / cm ² ) or higher.

In addition, the solid oxide fuel cell according to the present invention can achieve a fuel utilization efficiency of 60% or more when power is generated at a current density of 9.3 mA / cm ² . Further, a solid oxide fuel cell in which the composition, structure, setting, etc. are adjusted so that the fuel utilization efficiency is 60% or more is preferable. Here, the “fuel use efficiency” is the ratio of the consumed carbon amount calculated from the charge transfer amount assuming the reaction formula (4) with respect to the carbon in the solid carbon 2 supplied in the vicinity of the anode material 11b.

Moreover, the solid oxide fuel cell according to the present invention can achieve a fuel utilization efficiency of 20% or more when power is generated at a current density of 80 mA / cm ² . In addition, a solid oxide fuel cell in which the composition, structure, setting, etc. are adjusted so that the fuel utilization efficiency is 20% or more is preferable. Particularly preferably, it is 30% or more, more preferably 40% or more.

  Specifically, as described above, leakage of air from the outside of the system, that is, oxygen, is reduced as much as possible by improving the sealing performance, or the opening diameter of the anode 11 to the atmosphere is reduced. This is realized by reducing the loss of carbon monoxide (CO) in the reaction formula (1) and / or the reaction formula (2) by suppressing the inflow of oxygen to the anode 11.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1
As an electrolyte, ScSZ thickness 0.3 mm _(Sc 2 of 10 mole% _{O 3} and ZrO ₂ 1 mole% of CeO ₂ doped) using a disk, the anode material, Ni / GDC (Gd doped The CeO ₂ ) porous cermet was used, and a La _0.85 Sr _0.15 MnO ₃ porous film was used as a cathode material. The anode thickness was 50 μm.

  The configuration and manufacturing method followed the configuration and manufacturing method of a general solid oxide fuel cell. That is, the anode material and cathode material powders were dispersed in a solvent, and an organic binder or the like was added to prepare a slurry. Next, the slurry was applied to a disk by a doctor blade method and fired to produce a fuel cell.

  A solid oxide fuel cell was produced using the fuel cell described above. In order to confirm that power is generated by consuming solid carbon as fuel, 28.3 mg of carbon black (“MA7” manufactured by Mitsubishi Chemical Corporation) (hereinafter abbreviated as “CB”) was stored in the fuel chamber.

Thereafter, pure argon (Ar) was supplied to the anode at 202 STPmL / min for about 1 hour, and residual gas such as O ₂ was exhausted sufficiently. During the treatment, pure oxygen was supplied as an oxidizing agent to the cathode side. The cell was securely sealed, a 3.5 m 1/8 inch stainless steel tube was connected from the anode, and the gas chromatograph was sandwiched between the cells and the gas was exhausted to the outside with a 5 m vinyl tube (inner diameter: 8 mm).

Electric power was generated by adjusting the current to a certain constant current density at 900 ° C., and the change with time in the terminal voltage at each current density was monitored. A maximum output density of 20.3 mW / cm ² was obtained at a current density of 33.0 mA / cm ² . Therefore, it was confirmed that the fuel cell generates power using solid carbon supplied from the outside as fuel.

  In the above description, CB is directly supplied to the fuel chamber. However, even if molded solid carbon is supplied, power can be generated in the same manner as described above using the solid carbon in the molded solid carbon as a fuel.

  Since the present invention can supply fuel to the fuel cells without using gas as a fuel as in the prior art, it can be used only for stationary solid oxide fuel cells such as houses, factories and stores. In addition, since it can be applied to mobile solid oxide fuel cells such as mobile phones and personal computers, it is widely used in all fields that require electric power.

1 fuel chamber 2 solid carbon 3 carbon dioxide (CO ₂₎ outlet 10 fuel cell 11 anode 11a anode current collector 11b anode material 13 generating initiator inlet tube 21 electrolyte 22 the external control circuit 23 the electric circuit 31 cathode 31a cathode collector Body 31b Cathode material 33 Gas inlet containing oxidant 41 Lead wire 42 Partition network 43 Molded solid carbon (molded solid carbon)
44 Preliminary molded solid carbon 45 Preliminary molded solid carbon storage room

Claims (10)

  A fuel cell having an anode having an anode material comprising a composite metal oxide, a cathode having a cathode material, and an electrolyte comprising an ion conductive solid oxide disposed between the anode and the cathode, during power generation Solid carbon used as a fuel, and at least a fuel chamber for storing the solid carbon, the solid carbon in the fuel chamber is reacted with carbon dioxide generated by power generation to be converted into carbon monoxide, and the carbon monoxide Solid oxide fuel cell for generating power by oxidizing a solid oxide fuel cell, characterized in that the solid carbon used in the solid oxide fuel cell is molded solid carbon Battery power generation method.   The power generation method for a solid oxide fuel cell according to claim 1, wherein the shape of the molded solid carbon is a core shape, a rod shape, or a tablet shape.   The power generation method for a solid oxide fuel cell according to claim 1 or 2, wherein power generation is started by supplying carbon monoxide or carbon dioxide to the solid carbon in the fuel chamber. The tip of a power generation initiator introduction pipe for supplying carbon monoxide or carbon dioxide at the start of power generation is disposed on the anode side of the fuel cell, according to any one of claims 1 to 3. Power generation method for solid oxide fuel cells. The power generation of the solid oxide fuel cell according to claim 4, wherein a tip of a power generation initiator introduction pipe for supplying carbon monoxide or carbon dioxide at the start of power generation is disposed between the fuel chamber and the anode. Method.   6. The power generation method for a solid oxide fuel cell according to any one of claims 1 to 5, wherein the operation is performed while increasing the current density from its initial value immediately after the start of power generation.   The power generation method for a solid oxide fuel cell according to any one of claims 1 to 6, wherein an oxygen source is electrochemically injected into the anode at the start of power generation. 8. The solid oxide fuel according to claim 1, wherein the fuel cell generates power using the following reaction formulas (1) and (2) during power generation. Battery power generation method.
CO ₂ + C → 2CO (1)
CO + O ²⁻ → CO ₂ + 2e ⁻ (2)   The power generation method for a solid oxide fuel cell according to any one of claims 1 to 8, wherein a carbon content in the molded solid carbon is 50 mass% or more.   A fuel cell having an anode having an anode material comprising a composite metal oxide, a cathode having a cathode material, and an electrolyte comprising an ion conductive solid oxide disposed between the anode and the cathode, during power generation Solid carbon used as a fuel, and at least a fuel chamber for storing the solid carbon, the solid carbon in the fuel chamber is reacted with carbon dioxide generated by power generation to be converted into carbon monoxide, and the carbon monoxide A solid oxide fuel cell that generates electricity by oxidizing the solid oxide fuel cell, wherein the solid carbon is a molded solid carbon.

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