August 1969Apparently, electrolyte retention in the TESC was the most critical variable for reproducibility obtaining O2 reduction at a rate sufficient to establish an O2 cycle in a practical Pb-acid cell, without resorting to an auxiliary electrode. It is a complex function of the four variables mentioned previously. Since it was not feasible to optimize electrolyte retention through control of electrode and/or separator porosity or cell pack pressure, only elimination of the free electrolyte reservoir remained as a possible technique to achieve such control. This method was evaluated by raising the cell pack 0.5 in. above the bottom of the test cell. The electrolyte level could then be dropped below the bottom of the cell pack, eliminating all contact between them. Ionic contact to the reference electrode was maintained through a thin piece of separator on the back side of the test electrode which dipped into the electrolyte reservoir. Five such fully exposed electrodes, with three layers of microporous rubber on their inside faces, yielded Iss's of --110, --78, --114, --118, and--93 mA at --50 mV ~1 and 1 psig O2 in 1.3 sp gr H2SO4. These Iss'S lie in a significantly narrower range toward the upper end of the values obtained previously.Since b~)th O2 diffusion and the ability to send current through the system are heavily dependent on the amount of electrolyte retained in the TESC, over which there was no effective control, this data should not be considered to represent exactly the O2 reduction capability of the Pb/PbSO4 electrode. Satisfactory operation of maintenance-free Pb-acid cells will require close control of electrolyte metering. The optimum amount of electrolyte will have to be determined through a study of the initial distribution of electrolyte between electrodes and separators and its variation with cycling.

The anodic dissolution of nickel has been studied in acidified chloride, sulfate, and perchlorate solutions under a variety of nonpassivating conditions. The Tafel slopes at 45°C are approximately 0.085, 0.115, and 0.12, respectively. The lower value of the Tafel slope in chloride solutions is attributed to specific adsorption. The potential of the nickel anode is independent of Ni+2 concentration under conditions for which the back reaction is negligible, and no pH dependence has been found for pH of 1–2.5. The temperature dependence of the polarization yields an approximate value of 15 kcal/mole for the heat of activation in the chloride solution.

Immobilized‐electrolyte, high‐temperature fuel cells of nonconventional design were operated successfully on a wide variety of fuel gases. This design permits the incorporation of a reference electrode and avoids gasketing problems for low‐pressure operation. The performance of these cells was compared with preliminary results on free electrolyte and solid electrolyte cells. Oscilloscopic observations of polarization decay indicated that ohmic rather than concentration or activation polarization limits the performance of matrix cells in most instances.

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