OPTICAL ELECTROCHEMISTRY .2. REAL-TIME SPECTROSCOPY OF CONDUCTION-BAND ELECTRONS IN A METAL-OXIDE SEMICONDUCTOR ELECTRODE

Transparent titanium dioxide membranes (thickness 4-mu-m) were prepared by sintering 15-nm colloidal anatase particles on a conducting glass support. Potentiostatic control of the Fermi level within the colloidal-like particles of the membrane was possible. The kinetics of formation and dissipation of the accumulation layer have been measured. In addition, the real-time Nernstian shift of the membrane flatband potential following reduction of H+ ions at the surface of the TiO2 membrane under acidic conditions has been measured. Finally, reduction of methylviologen (MV2+) at a TiO2 membrane was investigated in real time by measurement of absorbance changes assigned both to charge carriers present in the accumulation layer, formed following application of the required negative potential step, and to the MV2+ molecules undergoing Faradaic processes.