The Photoelectrochemical Behavior of an n‐TiO₂ Electrode Coated with a Thin Metal Film, as Revealed by Measurements of the Potential of the Metal Film

Photocurrent‐potential curves of an n‐TiO 2 electrode coated with a thin gold or palladium film are studied in aqueous solutions, together with the change of the potential of the metal film with respect to the solution. It is found that, when the metal‐coated n‐TiO 2 electrode is illuminated under anodic potentials (i.e., in the presence of band bending), the potential of the metal film shifts toward the positive until it reaches the oxygen evolution potential at the metal, with little change of the surface band energies of the n‐TiO 2 electrode. This implies that the height of the Schottky barrier at the metal/ n‐TiO 2 contact is considerably increased by illumination, and the photovoltage obtained is much larger than expected from the barrier height in the dark.