Characterized Semiconductor Electrodes: II . Room Temperature Diffusion in a Single Crystal Rutile Electrode

The capacitance, spectral response, and volt‐ampere characteristics of lightly reduced TiO 2 photoelectrochemical electrodes are all significantly altered by immersion in concentrated acids or by operation at sufficiently negative voltages. These changes, which are reversible, are attributed to diffusion of protons along the c‐axis channels of rutile. There is an apparent threshold voltage for appreciable accumulation af protons which are presumed to enter the crystal as H atoms.