Impedance Measurements and Photoeffects on Ni Electrodes

Depending on the electrode potential an n‐type or a p‐type semiconducting oxide can be present at a Ni electrode surface giving rise respectively, to anodic or cathodic photocurrents under illumination. Impedance measurements show that a solid‐state diffusion process, presumably of protons through the oxide film, dominates the impedance behavior for the charged electrode; for the discharged electrode, the impedance behavior is dominated by the space charge inside the p‐type oxide. A flatband potential and donor density estimate could be made for the p‐type semiconducting oxide.