■Air Catalytic Layer (A-Cat) Uatrix(ilt) •Fuel Catalytic Layer(F-Cat) -Fuel Substrate (F-Sub) ■Fuel Ribbed Plate(F-RP)

Fig. 1,_Configuration of the sincrle cell was loaded only in matrix and in each electrode (it means in both Cat and Sub), not in each RP, at the fabrication of the cell The cells were tested for 16 hours under two conditions written below. After the test, the cells were disassembled within extremely short time, and the AFL of each component was measured by the weight changes of them. Condition 1: Open circuit with reactive gases Condition 2: Current load of300mA/cm2. Figure 2 shows the weight changes of acid in each component, i.e. subtracted values of the initial weights from the final weights. Figure 3 shows the AFL after this test

In the condition 1, the acid in A-Sub and F-Sub decreased almost the same weights, and the acid in A-EP and F-RP increased which approximately corresponded to the loss weights of each Sub. The weight changes of acid in the catalytic layers and the matrix were few. The distribution of the acid between each component was equal to the estimated balance based on the pore size distribution of each component.

In the condition 2, the weight gain of A-RP decreased to 18% of that of condition 1, and that of F-RP increased on the contrary about 1.5 times. Moreover, the acid decrease of A-Sub was greater than that of F-Sub; the AFL ofA-Sub decreased in the vicinity of 0%.

From the results mentioned above, under open circuit condition, the acid was distributed according to the capillary force of each component, regardless of electric potential level or the kinds of gases in each electrode. But when the cell was operated, the acid which was initially loaded in A-Sub and which had been absorbed in A-BP in condition 1 was

Teight change of acid(ng)

Teight change of acid(ng)

(Attar 16 hours test, at 1901C. PH2/P02=100)i/2l X)

transferred to the direction of anode. Consequently a driving force that transfers the acid toward anode exists in a cell during the cell operation.

Tanuma et al. conducted an investigation [ 2 ] concerning this force, and it was concluded to be electroosmotic pressures generated in the catalytic layers.

The relation between the driving force and current density

To investigate the relation between the acid driving force and current density, the same configuration cells as figure 1 were used. For this experiment the F-Sub was wet-proofed with PTFE dispersion. The purpose of this treatment was to make the difference of the driving force emphasize against the current density. A-RP was loaded with the acid of about 35% AFL at the fabrication of the cell, but not loaded in F-KP. After operating conditions of150,300,600mA/cm2for two hours respectively, the AFL of each component of the cell was measured in the same method as the previous section.

The weight of F-KP increased in every current density condition, that means the driving force at these current densities is stronger than the acid repellency force of F-Sub.

Figure.4 shows the correlation between the AFL of both EP and the current density. The AFL of F-KP linearly increased with the increase of the logarithm of current density, and the AFL of A-RP decreased to the contrary of that of F-RP. These findings indicated that the intensity of the driving force increased with the increase of current load.

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