Zeta potential measurements at titanium/titania plates at varying externally applied potentials between solid and solution

The zeta potential at Ti plates covered with a TiO2 layer is measured at different pH values and electrolyte (KCl, KNO3) concns. by the streaming-current method. A voltage is applied externally between the Ti electrode and a counter electrode. The range of voltages accessible for measurements is limited by breakdown of the dark current. In the range in which measurements can be performed, variations in the applied voltage do not result in measurable changes in zeta potential. This result cannot be explained by a simple, in-series capacitors model because the space-charge capacitances of the semiconductor and electrolyte are of the same order of magnitude. Possible explanations for this finding are discussed. [on SciFinder (R)]