The performance of sintered TiO 2-x electrodes and the electrochemical polymerization of O-phenylene diamine at surface imperfections

Abstract

TiO 2-x electrodes were fabricated under atmospheric conditions using the ceramic method at 1400°C. Photoelectrochemical and capacitance measurements permitted verification of the relation of the performance of such electrodes to the presence of surface imperfections. The electropolymerization of o-phenylene diamine ( OPD ) on TiO 2-x ceramic electrodes in the dark was investigated and compared with the electropolymerization of OPD on smooth platinum electrodes. The results indicate that polymerization occurs only on the surface imperfections of the TiO 2-x semiconductor and effectively blocks the electrode surface and prevents electron exchange with the solution. The photoelectrical response of electrodes subjected to this treatment shows the decrease of the dark current intensity in the potential region of oxygen adsorption in comparison with untreated electrodes. The flat band potential determined from Mott-Schottky plots did not correlate well with the potential for the onset of anodic photocurrent and photopotential. Evidence for the electrochemical incorporation of hydrogen in the oxide and oxide surface reduction are discussed.