JPH03245463A - Fuel cell - Google Patents

Abstract

PURPOSE:To generate a power of equal voltage on every position all over electrodes by gradually increasing the amount of catalyst carried on electrodes from the intake side toward the outlet side of the electrodes to which reaction gases are supplied. CONSTITUTION:A fuel gas is supplied to a fuel electrode 14, and air is supplied to an air electrode 15 separately to each other, and these reaction gases electrochemically react through a matrix layer 11 to generate a power. In a fuel cell, the amount of catalyst carried on electrodes is increased gradually from the intake side toward the outlet side of the electrodes to which the reaction gases are supplied. Thereby even when hydrogen and oxygen contributing to the electrochemical reaction contained in the reaction gases are consumed with the reaction, so as that the concentration of them is decreased from the intake side toward the outlet side of the electrodes to reduce the output voltage, on the other hand, the amount of catalyst on the electrodes is inversely increased from the intake side toward the outlet side of the electrodes so as to elevate the output voltage, hence as a whole, the generated voltage can be made uniform all over the electrodes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a fuel that generates electricity by supplying fuel gas to a fuel electrode and air to an air electrode, and causing these reaction gases to undergo an electrochemical reaction via a matrix. The present invention relates to a method for supporting a catalyst on a battery, particularly on an electrode thereof.

[Conventional technology]

FIG. 2 shows a general cell stack (also referred to as a cell stack) structure of a fuel cell. In the figure, 1 is a single cell (also called a single cell), which includes a matrix layer 11 holding an electrolyte, a fuel electrode catalyst layer 12, an air electrode catalyst layer 3,
It consists of a fuel electrode catalyst layer 4, an air electrode base material 15, and a separator 16. A cell stack 2 is constructed by stacking a large number of such single cells 1. Furthermore, the cell stack 2 is provided with cooling bodies 3 every few cells. The cooling body 3 has metal cooling vibes 5 buried in the layer of the cooling substrate 4 and is piped in order to cool the reaction heat generated when power is generated by an electrochemical reaction in each single cell.

Further, each cooling vibrator 5 is connected to the header vibrator and then to an external refrigerant supply line (not shown).

FIG. 3 shows a cross-sectional view of the single cell shown in FIG. 2.

A single cell includes a fuel electrode including a fuel electrode base material 14 through which fuel gas flows, and a fuel electrode catalyst layer 12 supporting a catalyst;
It consists of an air electrode made up of an air electrode base material 15 and an air electrode catalyst layer 13, and a matrix layer arranged between these picture electrodes. Fuel gas and air, which are reaction gases, are separately supplied to these electrodes.

In a phosphoric acid fuel cell, fuel gas contains carbon dioxide in addition to hydrogen, which is a reactive component, and air contains nitrogen in addition to oxygen, which is a reactive component. Only hydrogen and oxygen are consumed in the reaction gas supplied to each electrode, so as the reaction gas flows from the gas inlet to the outlet of the electrode substrate, hydrogen and oxygen are consumed by the reaction and gradually disappear. The component concentration decreases, and conversely, carbon dioxide and nitrogen increase their component concentrations.

On the other hand, as shown in the graph of FIG. 4, the relationship between the concentration of hydrogen and oxygen in the reaction gas and the output voltage of the fuel cell is such that as the concentration decreases, the output voltage decreases. Therefore, in a single cell, the output voltage is high at the inlet of the reactant gas, and gradually decreases toward the outlet of the reactant gas, where the concentration of hydrogen and oxygen is low. Potential differences occur depending on location. Conventionally, the fuel electrocatalyst layer 12 and the air electrocatalyst layer 13 of the electrode uniformly support an equal amount of milligrams of catalyst per square centimeter of the layer. Further, as shown in the graph of FIG. 5, the fuel cell electrode has a characteristic that when the amount of catalyst supported per unit area is increased, the cell output voltage increases.

[Problem to be solved by the invention]

As described above, in a fuel cell equipped with electrodes on which a catalyst is evenly supported, a potential difference occurs within the single cell, and in each single cell, this potential difference causes an equalization current to circulate within the electrode. Therefore, there is a problem in that loss due to heat generated by this current reduces power generation efficiency, and localized heat generation progresses local deterioration of the single cell.

This invention was made in view of this point, and its purpose is to provide a fuel cell that can eliminate the potential difference within a single cell, improve power generation efficiency, and create a single cell with a long life, and in particular, to provide a method for supporting a catalyst on its electrode. do.

[Means to solve the problem]

Above tJ1. In order to solve B, according to this invention,
In a fuel cell where fuel gas is supplied to a fuel electrode and air is supplied to an air electrode, these reactive gases undergo an electrochemical reaction via a matrix to generate electricity. The amount of catalyst supported by the electrodes shall be increased.

C Effect] According to this invention, since the amount of catalyst supported by the electrode of the fuel cell is increased from the inlet side where the reaction gas is supplied to the outlet side, hydrogen participating in the electrochemical reaction in the reaction gas is Even if oxygen and oxygen are consumed by the reaction and their concentration decreases from the inlet side to the outlet side of the electrode and the output voltage decreases,
On the other hand, since the amount of catalyst in the electrode increases from the inlet side to the outlet side, the resulting output voltage increases, and the voltage generated as a whole becomes uniform over the entire electrode.

(Example) The present invention will be described below based on Examples. Figure 1 is a graph showing the amount of catalyst supported on the electrode of a fuel cell according to the present invention. As the distance approaches, the amount of catalyst supported per unit area is increased.

〔Effect of the invention〕

In this invention, as mentioned above, by gradually increasing the number of catalysts in the electrode catalyst layer along the flow direction of the reaction gas, the same voltage can be generated at all locations on the electrode, creating a potential difference. Since no equalizing current flows in the electrodes of the fuel cell, it is possible to prevent a decrease in power generation efficiency due to heat loss caused by this current, and to eliminate the progress of local deterioration due to local heat generation. It can provide a long life fuel cell.

[Brief explanation of drawings]

Fig. 1 is a graph showing a method of supporting a catalyst on the electrode of a fuel cell according to the present invention, Fig. 2 is a perspective view of a cell stack, Fig. 3 is a cross-sectional view of a unit cell, and Fig. 4 is a graph showing the reaction passing through the electrode. FIG. 5 is a graph showing the relationship between the concentration of hydrogen and oxygen in the gas and the battery output voltage. FIG. 5 is a graph showing the relationship between the amount of catalyst supported per unit area on the electrode and the battery output voltage. 11: M) IJ wax layer 12: Fuel electrode catalyst layer, 1
3: Air electrode catalyst layer. 1WtY skin, m & 777λ [1711'JNlil 1st
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) Supplying fuel gas to the fuel electrode and air to the air electrode,
In a fuel cell that generates electricity through an electrochemical reaction between these reactive gases via a matrix, the fuel cell is characterized by increasing the amount of catalyst supported by the electrode from the inlet side of the electrode to which the reactive gas is supplied to the outlet side. fuel cell.