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AC impedance measurements were made on nickel oxide electrodes in an alkaline medium. The electrodes were prepared by electrodeposition of nickel oxide on nickel foils from a nickel nitrate solution. The main purpose of the investigation was to determine the dependence of impedance parameters on the state of charge of the electrode. The results demonstrated that the current phase shift and impedance modulus vary linearly with state of charge at low frequencies. Hence, the state of charge can be estimated from the values of phase shift and modulus. The state of charge of nickel electrodes exposed to argon and hydrogen was determined at various time intervals. It was found that the electrode exposed to hydrogen discharged faster than that exposed to argon, indicating that hydrogen enhances the self-discharge rate of nickel oxide electrodes.

A microcalorimetric method has been used to investigate the self-discharge behaviour of nickel oxyhydroxide electrodes in a pressurized gaseous hydrogen environment. It was found that the heat generation rate is proportional to hydrogen pressure, and is significantly dependent on the immersion state of the electrode in the electrolyte. Hence, diffusion of dissolved hydrogen gas towards or within the electrode controls, at least partially, the self-discharge rate. However, the heat generation decreases exponentially with time, indicating that self-discharge is also proportional to the amount of the charged active material available for the reaction. The presence of Mg, Co and Cd oxides or hydroxides appears to inhibit self-discharge. It was found that direct chemical reaction between dissolved hydrogen and the active material dominates, while in addition, electrochemical oxidation of hydrogen coupled with electrochemical reduction of the active material might also occur at a much smaller rate than the direct reaction.

Electronically conducting interconnector materials are required to connect consecutive anodes and cathodes in high-temperature solid oxide fuel cells. Nb-doped TiO2-glass composites, prepared by cold pressing and sintering in air above 1200° C, possess adequate conductivity and resistance to oxidizing and reducing atmospheres, as well as compatibility with Y2O3-doped ZrO2. They thus show promise as interconnector materials.