Interfacial phenomena at ZnO : CoO electrodes

Abstract The admittance of a cobalt-doped ZnO crystal/NaOH electrolyte interface has been studied as a function of frequency for various electrode potentials. Analysis of the admittance data gives evidence of a continuum of surface states, the density of which reaches a maximum for an energy 0.30 eV lower than the energy of the conduction-band edge. However, appropriate surface states are involved in the charge transfer processes of carriers photogenerated in the visible, between the Co 2+ states and the O 2 OH − level, and can stabilize as a consequence the electrode against photocorrosion.