JPH0311058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphoric acid fuel cell, and more specifically, a unit cell consisting of an air electrode, an electrolyte matrix, and a fuel electrode, and an electrode base provided with a reactive gas flow path. The present invention relates to a phosphoric acid fuel cell equipped with a gas separation plate sandwiching the two.

The conventionally well-known phosphoric acid fuel cell has a fuel electrode (anode) and an air electrode (cathode) placed opposite each other.
An electrolyte matrix holding phosphoric acid as an electrolyte is disposed between them, and the fuel electrode and air electrode are operated by supplying fuel gas and air to the fuel electrode and air electrode, respectively. At this time, depending on whether the supply groove for supplying the reaction gas is provided on the gas separation plate or on the electrode base material,
The former is generally called the paper type, and the latter is generally called the ribbed electrode type. In particular, the ribbed electrode type is attracting attention because it is possible to provide an internal reservoir, which is a mechanism for controlling the volume of the electrolyte, on the electrode base material, which is advantageous for the long-term stability of the battery.

FIG. 1 shows a conventional ribbed electrode with an internal reservoir, in which an air flow path 3 and a cathode catalyst layer 4 are arranged on a cathode electrode base material 2 disposed in contact with a gas separation plate 1. A fuel flow path 8 is formed in an anode electrode base material 7 having an anode catalyst layer 6 in contact with an electrolyte matrix 5 disposed in contact with a cathode catalyst layer 4 . Further, an internal reservoir 9 is arranged in the anode electrode base material 7.

In such a configuration, fuel and air flow into the cell orthogonally to each other as shown in FIG. That is, in FIG. 2, air flows from the air inlet manifold 10 to the air outlet manifold 1.
1 as shown by two points, and the fuel flows from the fuel inlet side manifold 12 to the fuel return side manifold 13 and further to the fuel outlet side manifold 14 perpendicular to the air flow as shown by the dashed line. The reason for returning fuel through the fuel return side manifold 13 is that if the reactive gases are simply crossed at right angles, the reactive gas will be consumed within the unit cell and the air will be the most diluted, and the fuel will be the most diluted. This is to prevent the dilution from being formed in the same area and the current distribution within the cell surface becoming uneven, making it impossible to obtain desired battery characteristics.By returning the fuel gas, the current distribution can be made uniform. This is an attempt to make the world a better place.

Here, the flow of the reaction gas will be further considered. FIG. 3 is a partially enlarged view of the cathode side, in which air flowing through the air flow path 3 passes through the porous cathode electrode base material 2 and reaches the cathode catalyst layer 4, where it reacts. When passing through this cathode electrode substrate 2, the air flow experiences a significant diffusion resistance, which causes a local reduction in current density and reduces the efficiency of the cell. This development appears more prominently in the lipped electrode type than in the thin paper type. The arrows shown in FIG. 3 indicate the flow of air from the air flow path 3 to the cathode catalyst layer 4, but compared to the air flowing through the thinnest arrow a of the cathode electrode base material 2, the arrow b passing through the thickest part of the cathode electrode base material 2 , c will experience greater diffusion resistance. Therefore, regarding the entire surface of the cathode catalyst layer 4, air reacts efficiently in the area directly below the air flow path 3 as shown by arrow a, and diffuses in the area sandwiched between the air flow paths 3 as shown by arrows b and c. Resistance reduces air utilization. The former active catalyst layer region 15 is an active region,
The catalyst layer area 16 that enters the latter blind spot is referred to as a blind spot area.

FIG. 4 is an enlarged view of the vicinity of the internal reservoir 9 on the anode side. Simply put, the internal reservoir 9 is made by filling the anode electrode base material 7 with a substance that is highly wettable to phosphoric acid, such as silicon carbide powder, and impregnating it with phosphoric acid. No blind zone is formed in the anode catalyst layer 6 near the internal reservoir 9, and the blind zone 16 is directly connected to the electrolyte matrix 5. This is because the change in the volume of phosphoric acid in the electrolyte matrix 5 is controlled by the internal reservoir 9, but for this reason, as seen in FIG. 4, the anode catalyst layer 6 is reduced by half.

The structure of the above ribbed electrode will be explained in more detail with reference to FIG. 5. Figure 5 shows the distribution of the above active area and blind area, with active area 15 and blind area 16.
is seen with the cathode side and the anode side superimposed, and the active region 15 is shown by diagonal lines in opposite directions on the anode side of the cathode side. As is clear from this figure, there are active areas 17 where both the cathode and anode are active areas, and blind areas 18 where both the cathode and anode are blind areas. Then both active areas 1
7, the reaction gas reacts most efficiently, whereas in both blind areas 18, the reaction gas has the lowest efficiency.
Here, the internal reservoir 9 is formed into a circular shape using both blind areas 18.

Both blind areas 18 occur because the reactant gas flow paths are orthogonal to each other, but if the air flow path 3 and fuel flow path 8 are made to flow in parallel as shown in FIG. Although this will not occur, both active regions will also disappear.

Conventional ribbed electrode fuel cells were constructed as described above, and had the disadvantage that they had a blind area of about 1/4 of the total surface area of the single cell, meaning that the catalyst layer could not be used effectively. Ta. Furthermore, although these blind spots were used as internal reservoirs, there was a problem in that these internal reservoirs were localized and were not structured to allow phosphoric acid to be supplied from the outside.

This invention was made in view of the above-mentioned circumstances, and involves providing undulations in opposite gas flow path units on the surface of the electrode base material opposite to the surface on which the reaction gas flow path is formed, and forming a catalyst layer along these undulations. The object of the present invention is to provide a phosphoric acid fuel cell in which both active regions are expanded and the utilization of the catalyst layer is significantly improved.

Another object of the present invention is to form a catalyst layer in the peaks and an internal reservoir in the troughs on the undulating surface of the electrode base material opposite to the surface on which the reaction gas flow path is provided, thereby achieving both active regions. The object of the present invention is to provide a phosphoric acid fuel cell in which the battery characteristics are improved by expanding the cell area to 1/2 of the total surface area of the single cell plane and eliminating blind spots on both sides.

Furthermore, it is an object of the invention to communicate the individual internal reservoirs to enable external phosphate replenishment;
An object of the present invention is to provide a phosphoric acid fuel cell having an internal reservoir structure that is effective for long-term stability of the cell.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 7 shows a ribbed electrode according to this embodiment, in which the surface of the cathode electrode base material 22 opposite to the surface on which the air flow path 23 is formed has undulations for each air flow path 23, that is, one air flow path 23. Forms one undulation. 22a indicates a cathode peak, and 22b indicates a cathode valley. The anode electrode base material 27 also has an anode valley part 27b and an anode peak part 2 opposite to the cathode peak part 22a and the cathode valley part 22b, respectively, on the surface opposite to the surface on which the fuel flow path 28 is formed.
7a, and the cathode catalyst layer 24, electrolyte matrix 25, and anode catalyst layer 26 are arranged between both the undulations and along the undulations. The internal reservoir 29 is in this example anode valley 2
7b, and the anode catalyst layer 26 is provided only on the anode mountain portion 27a. The gas separation plate 1 is the same as the conventional one.

Next, the action and effect will be explained. 8 and 9 show the flow of reaction gas, and in FIG. 8, white arrows indicate the flow of air, and black arrows indicate the flow of fuel gas. Air enters from the air inlet side inner manifold 30 formed in the gas separation plate 1 and passes through the air flow path 23.
The air flows along the air outlet and is guided to the internal manifold 31 on the outlet side. The fuel gas is led out from the fuel inlet internal manifold 32 through the fuel flow path 28 to the fuel outlet internal manifold 33. 34 is an external reservoir. Looking at this in the plan view of FIG. 9, the one-dot chain line indicates the flow of fuel gas, and the two-dot chain line indicates the flow of air. Air flows from the air inlet side manifold 35 to the air outlet side manifold 36, and the fuel gas fuel inlet side manifold 37, fuel inlet side internal manifold 32,
The fuel is guided from the fuel outlet side internal manifold 33 to the fuel outlet side manifold 38 . 34a is an electrolyte supply port of the external reservoir 34. As shown in FIG. 9, the air flow and the fuel gas flow flow parallel to each other, but there is no blind area between them as in the conventional case. This point will be explained in more detail.

FIG. 10 is an enlarged view of a part of the cathode side, with arrows pointing from the air flow path 23 to the cathode catalyst layer 2.
4, the air passes through the thinnest part of the cathode electrode base material 22 at the arrow abc. Therefore, a wide active region 39 is obtained.
On the other hand, as shown by the arrow d, the blind area 40 passing through the thick part of the cathode electrode base material 22 is approximately 1/3 of the active area 39, which is significantly reduced.

FIG. 11 is an enlarged view of a part of the anode side, in which the internal reservoir 29 is
The active region 39 is enlarged similarly to the cathode side.

FIG. 12 is a plan view showing a state in which the cathode side and the anode side of the above configuration are overlapped, and are occupied by the blind area 40 and both active areas 41, and both blind areas do not exist at all and both active areas 41 are Approximately 1/2 of the total area on a plane
It's getting old. White arrows indicate the air flow, and black arrows indicate the direction of the fuel gas flow.

In this way, when the above embodiment is used, both active regions are approximately doubled compared to the conventional device, and the efficiency of gas reaction is improved accordingly. In addition, by installing the internal reservoir in the blind area on the anode side,
Since the internal reservoirs are arranged in a straight line instead of being localized as in the conventional system, it is possible to use external reservoirs to communicate with each internal reservoir and supply phosphoric acid from the outside, as shown in Figure 9. This greatly improves the functionality of the internal reservoir.

In the above embodiment, the internal reservoir is formed on the anode side, but it may be formed using the blind area on the cathode side, or it may be provided on both the anode and the cathode.

Further, the internal manifold does not necessarily need to be provided on the gas separation plate, but may be provided on the electrode base material side, and the same effect can be achieved. The same applies to external reservoirs.

As is clear from the above explanation, this invention
It has special effects such as effectively utilizing the catalyst layer to improve the gas reaction and realize excellent battery characteristics, and also improves the function of the internal reservoir.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the main part of the conventional type, Figure 2 is a plan view of the conventional type showing the flow of reaction gas, Figure 3 is an enlarged front sectional view of the cathode of the conventional type, and Figure 4 is the same. An enlarged side sectional view of a conventional anode, FIGS. 5 and 6 are plan views showing the active area and blind area of the conventional anode, respectively. FIG. 7 is a side sectional view of a main part of an embodiment of the present invention. 8th
9 are a front sectional view and a plan view showing the flow of the reaction gas, FIGS. 10 and 11 are enlarged side sectional views of the cathode and anode of this embodiment, respectively, and FIG. 12 is an enlarged side sectional view of this embodiment. FIG. 2 is a plan view showing an active area and a blind area. DESCRIPTION OF SYMBOLS 1... Gas separation plate, 22... Cathode electrode base material, 23... Air flow path, 24... Cathode catalyst layer, 25... Electrolyte matrix, 26... Anode catalyst layer, 27... Anode electrode base material, 28...
Fuel flow path, 29... Internal reservoir, 30... Air inlet side internal manifold, 31... Air outlet side manifold, 32... Fuel inlet side internal manifold, 3
3...Fuel outlet side internal manifold, 34...External reservoir, 35...Air inlet side manifold, 36
...Air outlet side manifold, 37...Fuel inlet side manifold, 38...Fuel outlet side manifold, 3
9... Active area, 40... Blind spot area, 41... Both active areas. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An electrolyte matrix, a cathode electrode base material having a cathode catalyst layer and an air flow path, an anode electrode base material having an anode catalyst layer and a fuel flow path, and an action area to which phosphoric acid is supplied. None A phosphoric acid type comprising an internal reservoir formed in either the cathode electrode base material and the anode electrode base material, and a gas separation plate disposed on the outside of each of the cathode electrode base material and the anode electrode base material. In the fuel cell, the cathode electrode base material and the anode electrode base material have undulations, and the cathode catalyst layer and the anode catalyst layer are formed on one surface, respectively, and the cathode electrode base material has an undulating surface. The peaks and valleys of the undulations on the surface on which the cathode catalyst layer is formed are connected via the electrocatalytic matrix to the valleys and peaks of the undulations on the surface of the anode electrode base material on which the anode catalyst layer is formed, respectively. The peaks on the other surface of the cathode electrode base material are in contact with the gas separation plate to form the air flow path between the valleys and the gas separation plate, and the air flow path is formed between the valleys and the gas separation plate. The peaks on the other side of the material are in contact with another gas separation plate, and the fuel flow path is formed between the valley and the another gas separation plate, and the air flow path and the fuel flow path are A phosphoric acid fuel cell characterized in that the cells are arranged parallel to each other. 2. The phosphoric acid fuel cell according to claim 1, wherein a cathode catalyst layer and an internal reservoir are formed in the undulating peaks and valleys of the cathode electrode base material, respectively. 3. The phosphoric acid fuel cell according to claim 1, wherein an anode catalyst layer and an internal reservoir are formed in the undulating peaks and valleys of the anode electrode base material, respectively. 4. The phosphoric acid fuel cell according to claim 2 or 3, wherein the internal reservoir communicates with an external reservoir provided on the gas separation plate. 5. The phosphoric acid fuel cell according to claim 1, wherein the air flow path and the fuel flow path communicate with internal manifolds provided on the cathode electrode base material and the anode electrode base material, respectively. 6. The phosphoric acid fuel according to claim 1, wherein the air flow path and the fuel flow path communicate with internal manifolds provided in the gas separation plates on the cathode electrode base material side and the anode electrode base material side, respectively. battery.