JP2018085200A - Anode for solid oxide fuel cell and solid oxide fuel cell - Google Patents

Abstract

An anode for a solid oxide fuel cell that is advantageous in increasing active sites while maintaining good gas diffusibility of an active layer, and a solid oxide fuel cell using the anode. An anode 1 for a solid oxide fuel cell has a diffusion layer 2 for diffusing a fuel gas F supplied from the outside, and an active layer 3 in contact with one surface of the diffusion layer 2. The active layer 3 has a layer body portion 31 and a gas flow path 32. The layer body 31 is made of an active layer material and is formed more densely than the diffusion layer 2. The gas flow path 32 extends inward along the thickness direction of the active layer 3 from the interface 23 between the diffusion layer 2 and the active layer 3. [Selection] Figure 2

Description

  The present invention relates to an anode for a solid oxide fuel cell and a solid oxide fuel cell.

  2. Description of the Related Art Conventionally, a two-layered anode for a solid oxide fuel cell having a diffusion layer for diffusing fuel gas supplied from the outside and an active layer including an active site serving as an anode reaction field is known.

  Prior Patent Document 1 includes a pore derived from a pore forming agent, and has a pore diameter gradient composition in which the pore diameter increases from the solid electrolyte side toward the opposite side, for a solid oxide fuel cell. An anode is disclosed.

JP 2008-4422 A

  The prior art has the following problems. That is, in order to improve the power generation performance of the solid oxide fuel cell, it is effective to increase the active point by densifying the active layer and reduce the reaction resistance. However, when the active layer is densified, it becomes difficult for the fuel gas to reach the active layer, and the fuel gas necessary for the anode reaction is not supplied to the active point. As a result, the power generation performance decreases. Further, in order to secure an active point according to the power generation load, it is effective to increase the thickness of the active layer while maintaining the density of the active layer. However, if the thickness of the active layer is increased while maintaining the density of the active layer, the diffusion control of the fuel gas occurs at a stage where the thickness of the active layer is relatively thin. That is, a limit value corresponding to the density of the active layer exists in the thickness of the active layer, and it is difficult to freely design the thickness of the active layer according to the power generation load. Conversely, if the thickness of the active layer is set to a desired value, the active layer cannot be sufficiently densified to ensure the gas diffusibility of the active layer. Thus, in the prior art, there is a problem that it is difficult to achieve both an increase in active points due to densification and an increase in thickness of the active layer and ensuring good gas diffusibility of the active layer.

  The present invention has been made in view of the above problems, and has an anode for a solid oxide fuel cell that is advantageous for increasing active points while maintaining good gas diffusibility of an active layer, and a solid using the same. An oxide fuel cell is to be provided.

One aspect of the present invention is a diffusion layer (2) for diffusing fuel gas (F) supplied from the outside,
An active layer (3) in contact with one side of the diffusion layer,
The active layer is made of an active layer material, and extends inward along the thickness direction of the active layer from an interface (23) between the layer body portion (31) denser than the diffusion layer and the diffusion layer. A solid oxide fuel cell anode (1) having a gas flow path (32).

  Another aspect of the present invention resides in a solid oxide fuel cell (7) having the solid oxide fuel cell anode.

  In the anode for a solid oxide fuel cell, the active layer has a gas flow path extending inward along the thickness direction of the active layer from the interface with the diffusion layer. Therefore, in the solid oxide fuel cell anode, the fuel gas that has passed through the diffusion layer and reached the interface between the diffusion layer and the active layer is formed in the active layer regardless of the density and thickness of the active layer. It diffuses to the solid electrolyte layer side along the thickness direction of the active layer through the gas flow path, and then diffuses in the in-plane direction within the layer body portion of the active layer. Therefore, according to the anode for a solid oxide fuel cell, it is possible to increase the active point by densifying the active layer and increasing the thickness while maintaining good gas diffusibility of the active layer.

  The solid oxide fuel cell has the anode for the solid oxide fuel cell. Therefore, it is easy to secure a necessary active point according to the power generation load, and a solid oxide fuel cell advantageous in improving power generation performance can be obtained.

  In addition, the code | symbol in the parenthesis described in the means to solve a claim and a subject shows the correspondence with the specific means as described in embodiment mentioned later, and limits the technical scope of this invention. It is not a thing.

1 is a schematic cross-sectional view of an anode for a solid oxide fuel cell and a solid oxide fuel cell of Embodiment 1. FIG. 2 is a diagram schematically showing a part of the microstructure of an anode for a solid oxide fuel cell according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram for schematically illustrating an example of a cross section taken along line III-III of an active layer in the anode for a solid oxide fuel cell according to Embodiment 1 and for explaining a method of measuring an average flow path interval W of gas flow paths. is there. Explanatory drawing for demonstrating the measuring method of the average flow path space | interval W of a gas flow path while showing typically the modification of the III-III line cross section of the active layer in the anode for solid oxide fuel cells of Embodiment 1. FIG. It is. FIG. 3 is an explanatory diagram for explaining a method for measuring an average thickness D of an active layer in the anode for a solid oxide fuel cell according to Embodiment 1. FIG. 5 is another explanatory diagram for explaining a method for measuring the average thickness D of the active layer in the anode for the solid oxide fuel cell of Embodiment 1. 6 is a diagram schematically showing a part of the microstructure of an anode for a solid oxide fuel cell according to Embodiment 2. FIG.

(Embodiment 1)
The anode for a solid oxide fuel cell according to Embodiment 1 (hereinafter sometimes simply referred to as “anode”) will be described with reference to FIGS. As illustrated in FIGS. 1 to 5, the anode 1 of this embodiment is used for a solid oxide fuel cell 7 (SOFC). The solid oxide fuel cell 7 is a fuel cell using solid oxide ceramics showing oxygen ion conductivity as a solid electrolyte constituting the solid electrolyte layer 4.

  The anode 1 has a diffusion layer 2 and an active layer 3.

  The diffusion layer 2 is a layer for diffusing the fuel gas F supplied from the outside. The active layer 3 is a layer having electrode activity at a point including an active point that becomes a field for the anode reaction. The active layer 3 is in contact with one surface of the diffusion layer 2. The active layer 3 has a layer main body 31 and a gas flow path 32. In FIG. 1, the detailed configuration of the active layer 3 is omitted.

  The layer body portion 31 of the active layer 3 is made of an active layer material and is formed more densely than the diffusion layer 2. Specifically, the active layer material can include, for example, catalyst particles 311 and solid electrolyte particles 312.

  Specific examples of the catalyst constituting the catalyst particles 311 include Ni, Fe, Co, noble metals (Pt, Pd, etc.), Cu, Zn, Cr, Ti, Al, and alloys thereof. it can. Among these, Ni, Fe, Co, noble metals (Pt, Pd, etc.) can be suitably used as the catalyst from the viewpoint of electrical conductivity, catalytic activity, etc., more preferably Ni. Can do. The catalyst particles 311 can be used alone or in combination of two or more.

The solid electrolyte constituting the solid electrolyte particles 312 is specifically doped with at least one element selected from the group consisting of, for example, ZrO ₂ ; Y, Sc, Sm, Gd, and La. Examples include CeO ₂ doped with at least one element selected from the group consisting of ZrO ₂ ; CeO ₂ ; Gd, Sm, Y, La, Nd, Yb, Ca, and Ho. The solid electrolyte particles 312 can be used alone or in combination of two or more.

The active layer material includes Ni particles as catalyst particles 311 and solid electrolyte particles 312, and the solid electrolyte constituting the solid electrolyte particles 312 is made of ZrO ₂ ; Y, Sc, Sm, Gd, and La. ZrO ₂ doped with at least one element selected from the group consisting of: CeO ₂ ; or at least one selected from the group consisting of Gd, Sm, Y, La, Nd, Yb, Ca, and Ho When the element is doped CeO ₂ , there is the following advantage. That is, according to this configuration, it is possible to obtain the anode 1 that easily enhances the electrode activity of the active layer 3 in terms of material and easily maintains good power generation performance.

  Note that the diffusion layer material constituting the diffusion layer 2 specifically includes, for example, catalyst particles 211 and solid electrolyte particles 212 having the same configuration as the catalyst particles 311 and the solid electrolyte particles 312 in the active layer 3. be able to. However, the catalyst particles 211 and the solid electrolyte particles 212 may have different particle diameters from the catalyst particles 311 and the solid electrolyte particles 312 in consideration of gas diffusibility and the like.

  Specifically, the layer main body 31 of the diffusion layer 2 and the active layer 3 can include pores 10 constituted by interparticle gaps. Since the layer body 31 is formed more densely than the diffusion layer 2, the anode 1 is specifically configured to satisfy the relationship of the porosity of the layer body 31 <the porosity of the diffusion layer 2. Can do. The magnitude relationship of the porosity can be determined by observing a cross section perpendicular to the in-plane direction of the anode 1. If the size relationship between the porosity cannot be determined only from the cross-sectional observation, the cross-sectional image is binarized by image processing, and the layer body portion is calculated by the formula of 100 × the area Sp of the pores / the area Sm of the particles forming the skeleton. By calculating and comparing the porosity of 31 and the porosity of the diffusion layer 2, it is possible to determine the magnitude relationship of each porosity. However, Sp is the total area of the pores 10 in each measurement object, and Sm is the total area of the particles constituting the skeleton in each measurement object.

  Specifically, the porosity of the layer main body 31 can be set to 40% or less. According to this configuration, an anode 1 that can easily maintain good power generation performance due to an increase in active points due to densification of the active layer 3 can be obtained. The porosity of the layer body 31 can be preferably 35% or less, more preferably 30% or less. From the viewpoint of ensuring the ability to discharge water vapor generated by the anode reaction, the porosity of the layer body 31 is preferably 20% or more, more preferably 22% or more, and even more preferably 25% or more. Can do.

  Specifically, the porosity of the diffusion layer 2 is preferably 40% or more, more preferably 45% or more, and still more preferably 50% or more from the viewpoint of gas diffusibility and the like. The porosity of the diffusion layer 2 is preferably 60% or less, more preferably 58% or less, and even more preferably 55% or less, from the viewpoints of ensuring anode strength, securing an electron conduction path, and the like. .

  The gas flow path 32 of the active layer 3 extends inward of the active layer 3 along the thickness direction of the active layer 3 from the interface 23 between the diffusion layer 2 and the active layer 3. The interface 23 between the diffusion layer 2 and the active layer 3 is a boundary surface where the layer surface of the diffusion layer 2 on the active layer 3 side and the layer surface of the active layer 3 on the diffusion layer 2 side are in contact. Note that the gas flow path 32 is different from the pores 10 constituted by the interparticle gaps described above, and specifically, can be a flow path derived from a flow path forming agent.

  The gas flow path 32 may or may not penetrate the layer surface of the active layer 3 opposite to the interface 23 side between the diffusion layer 2 and the active layer 3. The layer surface of the active layer 3 opposite to the interface 23 side between the diffusion layer 2 and the active layer 3 is the surface that becomes the solid electrolyte layer 4 side when the anode 1 is applied to the solid oxide fuel cell 7. Yes, and comes into contact with the solid electrolyte layer 4 on the surface.

  The gas flow path 32 preferably includes a through flow path that penetrates the layer surface of the active layer 3 on the side opposite to the interface 23 side. According to this configuration, the fuel gas F can be easily diffused to the vicinity of the boundary between the active layer 3 and the solid electrolyte layer 4 through the through flow path, and then into the active layer 3 along the in-plane direction. It becomes easy to diffuse. Therefore, according to this configuration, it is possible to obtain the anode 1 that can easily keep the gas diffusibility of the active layer 3 better.

  Specifically, the gas flow path 32 can be comprised from a groove | channel or a hole, for example. According to this configuration, the active layer 3 can be formed relatively easily using a simple method such as a screen printing method. Therefore, the anode 1 excellent in manufacturability can be obtained. Moreover, according to this structure, since the layer main-body part 31 and the gas flow path 32 are easy to form by patterning, the anode 1 which can control the gas diffusibility of the active layer 3 easily according to patterning is obtained. In addition, the gas flow path 32 can be formed using the flow path forming agent which consists of an organic material burned down by baking at the time of manufacture of the anode 1, for example.

  When the gas flow path 32 is configured by a groove, the groove-shaped gas flow path 32 can surround the outer periphery of the layer main body 31, so that the fuel gas F extends in the in-plane direction from the outer periphery of the layer main body 31. Can be supplied into the layer body 31. Therefore, in this case, it is possible to obtain the anode 1 in which the gas diffusion property of the active layer 3 can be easily maintained. On the other hand, when the gas flow path 32 is formed of holes, the fuel gas F can be supplied into the layer main body 31 from the holes in a radial and in-plane direction. Therefore, also in this case, the anode 1 that easily maintains the gas diffusibility of the active layer 3 is obtained.

  More specifically, FIG. 3 shows an example in which the gas flow path 32 is constituted by a groove. As illustrated in FIG. 3, the layer main body 31 has a shape such as a polygonal shape such as a square shape or a circular shape (including an elliptical shape) as seen from a direction perpendicular to the layer surface of the active layer 3. Can be presented. In FIG. 3, quadrangular (more specifically, square) layer body portions 31 are regularly arranged in a row direction and a column direction with a groove-like gas flow path 32 (arranged in a plurality of rows × a plurality of columns). Example) is shown. In this case, one side of the layer main body 31 can be set to about 2 μm to 50 μm, for example.

  Moreover, in FIG. 4, an example in case the gas flow path 32 is comprised from a hole is shown. As illustrated in FIG. 4, the hole may have a shape such as a circular shape (including an elliptical shape) or a polygonal shape such as a quadrangle when viewed from a direction perpendicular to the layer surface of the active layer 3. it can. FIG. 4 shows an example in which circular holes are regularly arranged in a row direction and a column direction (arranged in a plurality of rows × a plurality of columns) across a layer main body portion 31 existing around the holes. Yes.

  Here, the anode 1 can be configured to satisfy 2D> W, where D is the average thickness of the active layer 3 and W is the average interval between the gas channels 32. According to this configuration, the fuel gas F can be reliably supplied to the active point close to the solid electrolyte layer 4 regardless of the density and thickness of the active layer 3. Therefore, according to this configuration, it is easy to obtain a solid oxide fuel cell advantageous for improving the power generation performance.

The average thickness D of the active layer 3 is measured as follows. The measurement sample is adjusted by polishing or the like so that a surface parallel to the in-plane direction of the anode 1 can be observed by SEM. At this time, the measurement sample is adjusted so that the layer main body 31 and the gas flow path 32 exist on the surface to be observed. In addition, an SEM field in which the active layer 3 and the gas flow path 32 on both sides of the active layer 3 are preliminarily selected by SEM is selected in advance, and an element included in the entire field is determined by SEM-EDX (energy dispersive spectrometer). Identify the species. From this result, the type of catalyst used in the active layer 3 is specified. When a plurality of catalysts are included, the following measurement is performed on the catalyst having the highest quantitative value of the element concentration. Next, line profile analysis is performed by SEM-EDX along a line (arrow DP in FIG. 5) that passes through substantially the center of the layer body 31 and is perpendicular to the in-plane direction of the anode 1. Here, the measurement width (measurement visual field in the in-plane direction of the anode 1) at the time of performing the line profile analysis is made to substantially coincide with the analysis width (arrow LW in FIG. 5) of the layer main body portion 31 that performs the line profile analysis. In the EDX spectrum thus obtained, the integrated intensity of the Kα characteristic X-ray peak of the catalyst element of interest is defined as the catalyst intensity, and a line profile of the catalyst intensity is obtained. For example, when the catalyst is Ni, a line profile of Ni intensity can be obtained by setting the integrated intensity from 7.3 keV to 7.8 keV of the obtained EDX spectrum as Ni intensity. In the line profile schematically shown in FIG. 6 (horizontal axis: analysis position in SEM-EDX line profile analysis, vertical axis: catalyst strength), the difference from the rising position to the falling position of the catalyst strength in the active layer 3 is D _i . The same measurement is performed on five randomly selected layer body portions 31, and the average value thereof is defined as the average thickness D of the active layer 3. The acceleration voltage during SEM observation is set to 2 to 3 times the energy at which the Kα characteristic X-ray peak of the catalyst element of interest appears. For example, when the catalyst is Ni, the Ni-Kα peak appears at 7.47 keV, so the acceleration voltage is preferably about 20 kV.

The average flow path interval W of the gas flow path 32 is a value measured as follows. The measurement sample is adjusted by polishing or the like so that a surface parallel to the in-plane direction of the anode 1 can be observed by SEM. At this time, the measurement sample is adjusted so that the layer main body 31 and the gas flow path 32 exist on the surface to be observed. Next, an area of about 20D × 20D (D is the average thickness D of the active layer 3 described above) is arbitrarily set in the SEM image of the observation surface. As illustrated in FIGS. 3 and 4, the longest linear distance from the gas channel formation location existing in the region to the other gas flow channel 32 through the layer main body 31 only once (see FIG. 3 and FIG. 4). the arrow length) in the W _i. The thus determined is W _i, performed on 100 or plants selected randomly, the average value of 100 obtained points of W _i, the average flow path width W of the gas passages 32.

Moreover, the anode 1 can make the average flow path width H of the gas flow path 32 into about 10 micrometers-50 micrometers, for example. The average flow path width H of the gas flow path 32 is a value measured as follows. The measurement sample is adjusted by polishing or the like so that the cross-sectional direction perpendicular to the in-plane direction of the anode 1 can be observed by SEM. At this time, the measurement sample is adjusted so that the layer main body 31 and the gas flow path 32 exist in the cross section to be observed. Next, with respect to the layer body 31 in the SEM image, one pulling the auxiliary line parallel to the plane direction of the anode 1, all measures the flow path width H _i of the gas channel 32 in the auxiliary line. This operation is performed on arbitrary five cross sections, and the average value of all the obtained _Hi is set as the average channel width H of the gas channel 32.

  The average length L of the gas flow path 32 in the anode 1 preferably satisfies the relationship L> (D−1 / 2W). According to this configuration, the gas diffusibility to the layer main body 31 by the gas flow path 32 can be kept better. More preferably, the gas flow path 32 may be provided so as to completely penetrate the active layer 3. According to this configuration, the fuel gas (F) can reliably reach the active layer 3 around the solid electrolyte layer where the contribution of power generation is the largest, and the best power generation output can be easily obtained.

In addition, the average length L of the gas flow path 32 is a value measured as follows. The measurement sample is adjusted by polishing or the like so that a surface parallel to the in-plane direction of the anode 1 can be observed by SEM. At this time, the measurement sample is adjusted so that the layer main body 31 and the gas flow path 32 exist on the surface to be observed. Then, with respect to the gas flow path 32 of the 20 points randomly selected from within SEM image, measuring the length L _i in the direction perpendicular to the plane direction of the anode 1. In addition, when the gas flow path 32 of 20 places does not exist in an observation visual field, the SEM image which can obtain the required number of gas flow paths is acquired additionally. The average value of _Li obtained in this way is defined as the average length L of the gas flow path 32.

  Specifically, the average thickness D of the active layer 3 can be, for example, 5 μm or more. The average thickness D of the active layer 3 is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, from the viewpoint of increasing the active point by increasing the thickness of the active layer 3. it can. Specifically, the average thickness D of the active layer 3 can be, for example, 100 μm or less. In this case, when the configuration satisfies 2D> W, the average flow path interval W of the active layer is less than 200 μm. Therefore, gas diffusion from the gas flow path 32 to the layer main body 31 is easily performed sufficiently, and the fuel gas can easily reach the vicinity of the center of the layer main body 31. Therefore, in this case, it is advantageous for securing the power generation output. The average thickness D of the active layer 3 is preferably 80 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, and still more preferably, from the viewpoint of facilitating the discharge of water vapor generated during power generation. , 35 μm or less.

  The average thickness of the diffusion layer 2 is preferably 200 μm or more, more preferably 250 μm or more, and even more preferably 300 μm or more, from the viewpoint of ensuring anode strength and the like. The average thickness of the diffusion layer 2 is preferably 450 μm or less, more preferably 400 μm or less, and even more preferably 350 μm or less from the viewpoint of improving gas diffusibility.

  The average thickness of the diffusion layer 2 can be calculated from the average thickness of the anode 1−the average thickness D of the active layer 3. The average thickness of the anode 1 is measured as follows. An SEM cross-sectional image perpendicular to the in-plane direction of the anode 1 is prepared. Note that the field of view of the SEM cross-sectional image is such that the thickness direction of the anode 1 is within one field of view. From the prepared SEM cross-sectional image, 20 measurement lines perpendicular to the in-plane direction of the anode 1 are drawn at equal intervals. However, when the measurement line is applied to the gas flow path 32, the measurement line is drawn with a position shifted so as to pass through the adjacent layer body 31. The length of each measurement line cut off on one side and the other side of the anode 1 is obtained, and the average value of the measurement lengths of the obtained 20 measurement lines is defined as the average thickness of the anode 1.

  In the anode 1, the layer body 31 specifically includes wall surface side catalyst particles 311 a disposed on the wall surface on the gas flow path 32 side and inner catalyst particles 311 b included inside the wall surface side catalyst particles 311 a. And the average particle diameter of the wall surface side catalyst particles 311a can be larger than the average particle diameter of the inner catalyst particles 311b.

  According to this configuration, due to the coarse wall surface side catalyst particles 311 a, it is difficult for water vapor contained in the fuel gas F flowing in the gas flow path 32 to enter the layer main body 31. Therefore, according to this structure, it becomes easy to suppress aggregation of the inner catalyst particles 311b due to the water vapor, and it becomes easy to obtain the anode 1 capable of maintaining good power generation performance over a long period of time. Note that the above-described configuration is, for example, a catalyst particle raw material disposed on the gas flow path 32 side using oxygen present in the space of the gas flow path 32 formed by burning out the flow path forming agent during anode manufacture. (For example, an oxide such as NiO) can be selectively grown and then reduced.

The average particle diameter is a value measured as follows. The measurement sample is adjusted by polishing or the like so that the cross-sectional direction perpendicular to the in-plane direction of the anode 1 can be observed by SEM. At this time, the measurement sample is adjusted so that the layer main body 31 and the gas flow path 32 exist in the cross section to be observed. Next, an SEM image in which a visual field having a size of 5D at least in the in-plane direction of the anode 1 and D in the thickness direction of the anode 1 can be observed is acquired (D is the average thickness D of the active layer 3 described above). With respect to all of the wall surface side catalyst particles 311a (20 arbitrarily selected wall surface side catalyst particles 311a) in the acquired SEM image, an auxiliary line passing in the in-plane direction of the anode 1 and passing through the center of the wall surface side catalyst particles 311a is drawn. Then, each auxiliary lines, the length across the respective wall-side catalyst particles 311a and d _w. The average value of d _w obtained, the average particle diameter of the wall-side catalyst particles 311a. Further, five auxiliary lines are drawn at equal intervals in the in-plane direction of the anode 1 and across the layer main body 31 from the acquired SEM image. Next, let d _i be the length of each auxiliary line crossing the respective inner catalyst particle 311b. For all inner catalytic particles 311b auxiliary line crosses measures the d _i, the average value of the d _i obtained, the average particle diameter of the inner catalyst particles 311b.

  The average particle diameter of the wall-side catalyst particles 311a is preferably 0.5 μm or more, more preferably 0.8 μm or more, and still more preferably, from the viewpoint of easily suppressing aggregation degradation of the inner catalyst particles 311b due to water vapor. 1 μm or more. The average particle diameter of the wall surface side catalyst particles 311a is preferably 2 μm or less, more preferably 1.8 μm or less, and even more preferably 1.5 μm or less, from the viewpoint of securing active sites. The average particle diameter of the inner catalyst particles 311b is preferably 0.3 μm or more, more preferably 0.5 μm or more, and still more preferably 0.8 μm or more, from the viewpoint of suppressing deterioration due to particle aggregation. Can do. The average particle diameter of the inner catalyst particles 311b is preferably 1.5 μm or less, more preferably 1 μm or less, and still more preferably 0.9 μm or less, from the viewpoint of securing active sites.

  In the anode 1, the wall-surface side catalyst particles 311 a and the inner side catalyst particles 311 b can be specifically composed of Ni particles. According to this configuration, composition change due to reaction diffusion between different kinds of materials hardly occurs, so that it is easy to improve performance stability during power generation.

  In the anode 1 of the present embodiment, the active layer 3 has a gas flow path 32 extending inward from the interface 23 with the diffusion layer 2 along the thickness direction of the active layer 3. Therefore, in the anode 1, the fuel gas F that has reached the interface 23 between the diffusion layer 2 and the active layer 3 through the diffusion layer 2 is formed in the active layer 3 regardless of the density and thickness of the active layer 3. Then, it diffuses through the gas flow path 32 along the thickness direction of the active layer 3 to the solid electrolyte layer 4 side, and then diffuses within the layer main body 31 of the active layer 3 along the in-plane direction. Therefore, according to the anode 1, it is possible to increase the active points by densifying the active layer 3 and increasing the thickness while keeping the gas diffusibility of the active layer 3 good.

  A solid oxide fuel cell according to Embodiment 1 will be described with reference to FIG. The solid oxide fuel cell 7 of the present embodiment includes the solid oxide fuel cell anode 1 of the first embodiment.

  In the present embodiment, the solid oxide fuel cell 7 specifically includes an anode 1, a solid electrolyte layer 4, and a cathode 6. The solid oxide fuel cell 7 may further include an intermediate layer 5 between the solid electrolyte layer 4 and the cathode 6, as illustrated in FIG. The intermediate layer 5 is a layer mainly for suppressing the reaction between the solid electrolyte layer material and the cathode material. In the present embodiment, specifically, the solid oxide fuel cell 7 includes an anode 1, a solid electrolyte layer 4, an intermediate layer 5, and a cathode 6 that are stacked in this order and joined together. The solid oxide fuel cell 7 can be an anode support type in which the anode 1 as an electrode functions as a support. In the anode-supported solid oxide fuel cell 7, the anode 1 is sufficiently thicker than the other layers. FIG. 1 shows an example in which the outer shape of the solid oxide fuel cell 7 is rectangular. Besides, the outer shape of the solid oxide fuel cell 7 may be a circular shape or the like. In the solid oxide fuel cell 7, the fuel gas F is supplied from the outside to the surface of the anode 1 opposite to the solid electrolyte layer 4 side.

  As a material of the solid electrolyte layer 4, zirconium oxide-based oxides such as yttria stabilized zirconia and scandia stabilized zirconia can be suitably used from the viewpoint of excellent strength and thermal stability. The material of the solid electrolyte layer 4 is preferably yttria-stabilized zirconia from the viewpoints of oxygen ion conductivity, mechanical stability, compatibility with other materials, and chemical stability from an oxidizing atmosphere to a reducing atmosphere. is there. In the present embodiment, specifically, yttria-stabilized zirconia can be used as the material of the solid electrolyte layer 4.

  The thickness of the solid electrolyte layer 4 is preferably 3 to 20 μm, more preferably 4 to 15 μm, and still more preferably 5 to 10 μm, from the viewpoint of reducing ohmic resistance.

  The cathode 6 is disposed on the opposite side of the solid electrolyte layer 4 from the anode 1 side. In the present embodiment, the outer shape of the cathode 6 is formed smaller than the outer shape of the anode 1. In each figure, the outer shapes of the anode 1, the solid electrolyte layer 4, and the intermediate layer 5 are all substantially the same.

Examples of the material of the cathode 6 include transition metal perovskite oxides. The transition metal perovskite oxide, specifically, for _{example, La x Sr 1-x CoO} 3 based _{oxide, La x Sr 1-x Co} y Fe 1-y O 3 based oxide, _Sm x Sr ₁ Examples include _-x CoO ₃ oxides (wherein 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). These can be used alone or in combination of two or more. In the present embodiment, specifically, La _x Sr _1-x Co _y Fe _1-y O ₃ -based oxide (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is used as the material of the cathode 6. it can.

  The thickness of the cathode 6 is preferably 20 to 100 μm, more preferably 30 to 80 μm, from the viewpoints of gas diffusibility, electrode reaction resistance, current collection, and the like.

Examples of the material of the intermediate layer 5 include CeO ₂ , or CeO ₂ doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho. Examples thereof include cerium oxide-based oxides such as ceria-based solid solutions. These can be used alone or in combination of two or more. In the present embodiment, specifically, a ceria-based solid solution in which CeO ₂ is doped with Gd can be used as the material of the intermediate layer 5.

  Further, the thickness of the intermediate layer 5 is preferably 1 to 20 μm, more preferably 2 to 5 μm, from the viewpoints of reducing ohmic resistance and suppressing element diffusion from the cathode 6.

  The solid oxide fuel cell 7 of the present embodiment has the anode 1 of the present embodiment. Therefore, the solid oxide fuel cell 7 is easy to ensure a necessary active point according to the power generation load, and is advantageous in improving the power generation performance.

(Embodiment 2)
The anode for a solid oxide fuel cell according to Embodiment 2 will be described with reference to FIG. Of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-described embodiments represent the same components as those in the above-described embodiments unless otherwise indicated.

  As illustrated in FIG. 6, in the anode 1 of the present embodiment, the layer main body portion 32 includes wall surface side catalyst particles 311 a arranged on the wall surface on the gas flow path 32 side and wall surfaces, as in the first embodiment. And the inner catalyst particles 311b included inside, the average particle diameter of the wall surface side catalyst particles 311a may be larger than the average particle diameter of the inner catalyst particles 311b.

  In the anode 1 of the present embodiment, specifically, the inner catalyst particles 311b can be composed of Ni particles, and the wall surface side catalyst particles 311a can be composed of Ni alloy particles. According to this configuration, the Ni alloy particles have a higher material aggregation suppressing effect than the Ni particles, so that water vapor that can be contained in the fuel gas F flowing in the gas flow path 32 enters the layer main body 31. It becomes difficult. That is, according to this configuration, since the wall surface side catalyst particles 311a are coarser than the inner catalyst particles 311b, it is difficult for water vapor to penetrate into the layer main body 31 morphologically, and the Ni alloy is made of Ni in terms of material. Therefore, it is possible to obtain an anode 1 that easily maintains good power generation performance over a long period.

  Specific examples of alloy elements other than Ni in the Ni alloy constituting the Ni alloy particles include, for example, Fe, Co, Ti, Cu, Ni, Mg, Ca, Mn, Cr, Zn, Al, and the like. Can do. These can be used alone or in combination of two or more. As the alloy element, at least one selected from the group consisting of Fe, Co, Ti, and Cu can be suitably used from the viewpoint of ensuring the above-described effects. Particularly preferably, the Ni alloy can be a Ni—Fe alloy from the viewpoint of a large aggregation suppressing effect on water vapor.

In addition, the said structure can be obtained as follows, for example. That is, the oxide of the above-described alloy element (Fe ₂ O ₃ or the like) is added to the flow path forming agent at the time of manufacturing the anode. In this case, when the flow path forming agent burns out, the oxide added to the flow path forming agent is taken into the nickel oxide (NiO) particles on the wall surface of the layer main body portion 31, and is added to the wall surface of the layer main body portion 31. A composite oxide (Ni-Fe composite oxide or the like) containing Ni and the above alloy elements is produced. Then, using the oxygen present in the space of the gas flow path 32 formed by burning the flow path forming agent, the composite oxide particles arranged on the gas flow path 32 side were selectively grown. Thereafter, coarse Ni alloy particles (such as Ni—Fe alloy particles) can be generated by reduction. Thereby, the said structure can be obtained.

  Other configurations and operational effects are the same as those of the first embodiment.

(Experimental example 1)
<Material preparation>
NiO powder (average particle size: 1.0 μm), yttria-stabilized zirconia (8YSZ) powder (average particle size: 0.8 μm) containing 8 mol% of Y ₂ O ₃ , carbon (pore forming agent), polyvinyl A slurry was prepared by mixing butyral (organic material), isoamyl acetate, 2-butanol and ethanol (mixed solvent) with a ball mill. The mass ratio of NiO powder and 8YSZ powder was 60:40. Using the doctor blade method, the slurry was applied in layers on a resin sheet, dried, and then the resin sheet was peeled off to prepare a diffusion layer forming sheet. The average particle diameter is the particle diameter (diameter) d50 when the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method shows 50% (hereinafter the same).

  By mixing 8YSZ powder (average particle size: 0.8 μm), polyvinyl butyral, ethyl cellulose (organic material), and terpineol (solvent) with a ball mill, a paste for forming the layer body part of the active layer is obtained. Got ready.

  A flow path forming paste was prepared by mixing acrylic resin powder (binder) (average particle size: 0.6 μm), ethyl cellulose and terpineol with a ball mill.

By mixing acrylic resin powder (binder) (average particle size: 0.6 μm), Fe ₂ O ₃ powder (average particle size: 0.5 μm), ethyl cellulose, and terpineol with a ball mill, A paste for forming a flow path containing Fe ₂ O ₃ was prepared. Incidentally, the content of _Fe 2 _{O 3} with respect to the acrylic resin powder was 1 mass%.

  A slurry was prepared by mixing 8YSZ powder (average particle size: 0.8 μm), polyvinyl butyral, isoamyl acetate, 2-butanol and ethanol with a ball mill. Thereafter, a solid electrolyte layer forming sheet was prepared in the same manner as the preparation of the diffusion layer forming sheet.

A slurry was prepared by mixing CeO ₂ (10GDC) powder (average particle diameter: 0.8 μm) doped with 10 mol% Gd, polyvinyl butyral, isoamyl acetate, 2-butanol and ethanol with a ball mill. . Thereafter, an intermediate layer forming sheet was prepared in the same manner as the preparation of the diffusion layer forming sheet.

By mixing La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (LSCF) powder (average particle size: 0.6 μm), ethyl cellulose, and terpineol (solvent) with a ball mill, A cathode forming paste was prepared.

<Preparation of Sample 1 Anode, Sample 1 Fuel Cell Single Cell>
A plurality of diffusion layer forming sheets were laminated and pressure-bonded using an isostatic pressing (CIP) molding method to obtain a first pressure-bonded body having a thickness of 500 μm. The CIP molding conditions were a temperature of 80 ° C., a pressing force of 50 MPa, and a pressing time of 10 minutes.

  Next, a layer body portion forming paste patterned so as to form a layer body portion as shown in FIG. 3 was applied to the surface of the first pressure-bonded body by a screen printing method. Such patterning was performed by screen plate making. In this example, adjustment is made so that a plurality of square-shaped application portions of 50 μm in length × 50 μm in width are regularly arranged in the row direction and the column direction, with each being 30 μm apart (with a gap). did.

  Next, the flow path forming paste was applied to the surface of the first pressure-bonded body to which the layer main body forming paste was applied, by a screen printing method using a reverse pattern having a negative / positive relationship with respect to the pattern.

  Next, the solid electrolyte layer forming sheet and the intermediate layer forming sheet are laminated in this order on the paste application surface of the diffusion layer forming sheet to which the layer body portion forming paste is applied, and hydrostatic pressure press (CIP) molding is performed. A second pressure-bonded body was obtained by pressure bonding using the method. The second pressure-bonded body was degreased after pressure bonding. The CIP molding conditions were a temperature of 80 ° C., a pressing force of 50 MPa, and a pressing time of 10 minutes.

  Next, the second pressure-bonded body was fired at 1350 ° C. for 2 hours. As a result, a sintered body was obtained in which the anode composed of the diffusion layer and the active layer, the solid electrolyte layer (10 μm), and the intermediate layer (10 μm) were laminated in this order.

Next, a cathode forming paste was applied to the surface of the intermediate layer of the sintered body by a screen printing method and baked at 1000 ° C. for 2 hours to form a layered cathode (thickness 60 μm). Thereafter, the anode was reduced at 800 ° C. in an H ₂ atmosphere. Thus, a fuel cell unit cell of Sample 1 having the anode of Sample 1 was obtained.

  The anode of Sample 1 has a diffusion layer and an active layer. The active layer is composed of an active layer material containing Ni and YSZ, and includes a layer body portion denser than the diffusion layer and a groove extending inward along the thickness direction of the active layer from the interface with the diffusion layer. A gas flow path. The gas flow path penetrates the interface of the active layer on the side opposite to the interface side. The average thickness D of the active layer measured by the above-described method is 30 μm, the average length L of the gas channel is 29 μm, the average channel interval W of the gas channel is 41 μm, the average thickness of the diffusion layer is 300 μm, and the layer body part The porosity was 30%, and the porosity of the diffusion layer was 65%. Further, when the cross section of the active layer was observed by SEM, the Ni particles (wall surface side catalyst particles) on the wall surface on the gas flow path side in the layer main body portion were Ni particles (inner catalyst particles) on the inner side of the Ni particles on the wall surface side. It was coarser. The average particle diameter of the Ni particles on the wall surface side measured by the above-described method was 1.1 μm, and the average particle diameter of the inner Ni particles was 0.8 μm.

<Production of Sample 2 Anode and Sample 2 Fuel Cell Single Cell>
In the preparation of Sample 1, a layer body part forming paste patterned so as to form a layer body part as shown in FIG. 4 was applied to the surface of the first pressure-bonded body by a screen printing method. Such patterning was performed by screen plate making. In this example, the plurality of holes having a diameter of 100 μm were adjusted so as to be regularly arranged in the row direction and the column direction in a state of being spaced apart from each other by the application part. At this time, the inter-hole distance in the diagonal direction between adjacent holes was set to 50 μm.

  Next, the flow path forming paste was applied to the surface of the first pressure-bonded body to which the layer main body forming paste was applied, by a screen printing method using a reverse pattern having a negative / positive relationship with respect to the pattern. Except for these points, the fuel cell single cell of Sample 2 having the anode of Sample 2 was obtained in the same manner as Sample 1.

  The anode of Sample 2 has a diffusion layer and an active layer. The active layer is made of an active layer material containing Ni and YSZ, and has a layer body portion denser than the diffusion layer and a hole extending inward along the thickness direction of the active layer from the interface with the diffusion layer. A gas flow path. The gas flow path penetrates the interface of the active layer on the side opposite to the interface side. The average thickness D of the active layer measured by the above-described method is 20 μm, the average length L of the gas channel is 19 μm, the average channel interval W of the gas channel is 38 μm, the average thickness of the diffusion layer is 300 μm, and the layer body part The porosity was 30%, and the porosity of the diffusion layer was 65%. Further, when the cross section of the active layer was observed by SEM, the Ni particles (wall surface side catalyst particles) on the wall surface on the gas flow path side in the layer main body portion were Ni particles (inner catalyst particles) on the inner side of the Ni particles on the wall surface side. It was coarser. The average particle diameter of the Ni particles on the wall surface side measured by the above-described method was 1.1 μm, and the average particle diameter of the inner Ni particles was 0.8 μm.

<Preparation of Sample 3 Anode, Sample 3 Fuel Cell Single Cell>
In the preparation of Sample 1, the gap between the application parts formed on the surface of the first pressure-bonded body was filled with Fe ₂ O ₃ containing flow path forming paste by screen printing. Except for this point, the fuel cell single cell of Sample 3 having the anode of Sample 3 was obtained in the same manner as Sample 1. In addition, the organic substance in the paste for forming a flow path containing Fe ₂ O ₃ was burned out by firing.

  When the cross section of the active layer was observed by SEM, the wall surface side catalyst particles on the wall surface on the gas flow path side in the layer main body were coarser than the Ni particles (inner catalyst particles) inside the wall surface side catalyst particles. When the cell laminate cross section was adjusted by polishing or the like for SEM observation and the material of the wall surface side catalyst particles was specified by performing SEM-EDS analysis, the wall surface side catalyst particles were Ni-Fe alloy particles. The average particle size of the Ni—Fe alloy particles on the wall surface side measured by the above-described method was 0.9 μm, and the average particle size of the inner Ni particles was 0.8 μm. The other measured values were equivalent to Sample 1.

<Preparation of Sample 4 Anode, Sample 4 Fuel Cell Single Cell>
In preparing Sample 2, the pores formed on the surface of the first pressure-bonded body were filled with a flow path forming paste containing Fe ₂ O ₃ by screen printing. Except for this point, the fuel cell unit cell of Sample 4 having the anode of Sample 4 was obtained in the same manner as Sample 2. In addition, the organic substance in the paste for forming a flow path containing Fe ₂ O ₃ was burned out by firing.

  When the cross section of the active layer was observed by SEM, the wall surface side catalyst particles on the gas flow path side wall surface in the layer main body were coarser than the Ni particles (inner catalyst particles) inside the wall surface side catalyst particles. . When the cell laminate cross section was adjusted by polishing or the like for SEM observation and the material of the wall surface side catalyst particles was specified by performing SEM-EDS analysis, the wall surface side catalyst particles were Ni-Fe alloy particles. The average particle size of the Ni—Fe alloy particles on the wall surface side measured by the above-described method was 0.9 μm, and the average particle size of the inner Ni particles was 0.8 μm. The other measured values were equivalent to those of Sample 2.

(Experimental example 2)
A plurality of levels of anode-supported fuel cell single cells having gas flow paths were produced by the same production method as in <Preparation of Sample 1 Anode, Sample 1 Fuel Cell Single Cell> in Experimental Example 1. Specifically, a plurality of samples having the levels shown in Table 1 were produced by changing the number of times the layer body portion forming paste was printed and the coating pattern of the layer body portion forming paste. In this Experimental Example 2, adjustment was made so that a plurality of square-shaped application portions of 50 μm in length × 50 μm in width were regularly arranged in the row direction and the column direction, and the spacing between the plurality of square-shaped application portions Was changed as shown in Table 1. The anode and the solid electrolyte layer were adjusted to 100 × 100 mm after firing, and the cathode was adjusted to 80 × 80 mm.

  About the produced samples of each level, the average thickness D of the active layer in the anode, the average channel interval W of the gas channel, and the average length L of the gas channel were measured by the above-described methods.

Next, a power generation test was carried out on the single fuel cell of each sample produced. With 100% -H ₂ to the fuel, the fuel utilization rate at 25A power was adjusted flow rate to be 80%. Current-voltage (IV) characteristics up to 25A were measured, and the power generation amount (current x voltage) at 25A was calculated. These results are summarized in Table 1.

  According to Table 1, the following can be understood. From a comparison between level 1 and level 6 or level 7, it was confirmed that the power generation output increased at levels 6 and 7 where the gas flow path was formed even with the same active layer thickness. This is because the gas flow path maintains good gas diffusibility into the active layer.

  Further, when the relationship of 2D> W was satisfied, it was confirmed that the power generation output increased even with the same active layer thickness. In addition, when the relationship of 2D> W was satisfied, it was confirmed that the power generation output increased as the active layer thickness increased. This is because when the relationship of 2D> W is satisfied, the gas diffusibility of the active layer can be maintained better than when the relationship of 2D> W is not satisfied.

  Further, when the average thickness D of the active layer exceeds 100 μm, the power generation output may decrease. From this result, by setting the average thickness D of the active layer to 100 μm or less and the average flow path interval W of the active layer to less than 200 μm, gas diffusion from the gas flow path to the layer main body 31 is promoted, and the layer main body 31 It has been confirmed that it is advantageous for securing the power generation output to make the fuel gas easily reach the vicinity of the center.

  The present invention is not limited to the above-described embodiments and experimental examples, and various modifications can be made without departing from the scope of the invention. Moreover, each structure shown by each embodiment and each experiment example can be combined arbitrarily, respectively.

DESCRIPTION OF SYMBOLS 1 Anode for solid oxide fuel cell 2 Diffusion layer 23 Interface 3 Active layer 31 Layer body part 32 Gas flow path 4 Solid electrolyte layer 7 Solid oxide fuel cell F Fuel gas

Claims (11)

A diffusion layer (2) for diffusing the fuel gas (F) supplied from the outside;
An active layer (3) in contact with one side of the diffusion layer,
The active layer is made of an active layer material, and extends inward along the thickness direction of the active layer from an interface (23) between the layer body portion (31) denser than the diffusion layer and the diffusion layer. A solid oxide fuel cell anode (1) having a gas flow path (32).   2. The anode for a solid oxide fuel cell according to claim 1, wherein the gas flow path includes a through flow path that penetrates a layer surface of the active layer on a side opposite to the interface side. When the average thickness of the active layer is D and the average channel interval of the gas channels is W,
The anode for a solid oxide fuel cell according to claim 1 or 2, wherein 2D> W is satisfied.   The anode for a solid oxide fuel cell according to any one of claims 1 to 3, wherein the gas flow path is constituted by a groove or a hole. The layer body has wall surface side catalyst particles (311a) disposed on the wall surface on the gas flow path side, and inner catalyst particles (311b) included inside the wall surface side catalyst particles,
5. The anode for a solid oxide fuel cell according to claim 1, wherein an average particle diameter of the wall surface side catalyst particles is larger than an average particle diameter of the inner catalyst particles.   6. The anode for a solid oxide fuel cell according to claim 5, wherein both the wall surface side catalyst particles and the inner side catalyst particles are Ni particles. The inner catalyst particles are Ni particles,
6. The anode for a solid oxide fuel cell according to claim 5, wherein the wall surface side catalyst particles are Ni alloy particles.   The anode for a solid oxide fuel cell according to any one of claims 1 to 7, wherein the porosity of the layer body is 40% or less.   9. The anode for a solid oxide fuel cell according to claim 1, wherein the average thickness of the active layer is 5 μm or more and 100 μm or less. The active layer material contains Ni particles and solid electrolyte particles,
The solid electrolyte constituting the solid electrolyte particles is ZrO ₂ , CeO ₂ or Gd doped with at least one element selected from the group consisting of ZrO ₂ , Y, Sc, Sm, Gd, and La. 10. The CeO ₂ doped with at least one element selected from the group consisting of Sm, Y, La, Nd, Yb, Ca, and Ho. Anode for solid oxide fuel cell.   A solid oxide fuel cell (7) comprising the anode for a solid oxide fuel cell according to any one of claims 1 to 10.

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