ACTIVATION OF TITANIUM ELECTRODES FOR VOLTAMMETRIC DETECTION OF OXYGEN AND HYDROGEN-PEROXIDE IN ALKALINE MEDIA

Bright, freshly-polished Ti electrodes give minimal cathodic response for O-2 and H2O2 in 1.0 M NaOH. However, the response is increased gra dually by repeated application of a triangular waveform within the app roximate potential limits of O-2 response (ca. -1.5 to -0.7 V vs. SCE) . This same voltammetric pretreatment applied for excessive periods re sults in formation of golden films on the Ti surfaces that are active for reduction of O-2 and H2O2. Levich plots of cathodic current for O- 2 and H2O2 at rotated golden-Ti disk electrodes in 1.0 M NaOH (-1.35 V ) are linear over a large range of rotational velocity (42 to 513 rad s(-1)), a behavior considered to be indicative of fast heterogeneous k inetics. Ring-disk data demonstrate that a small amount of H2O2 is pro duced throughout the potential region for O-2 reduction and H2O2 is co ncluded to be an intermediate product in the O-2-reduction mechanism. These observations are consistent with those reported previously for s ingle-crystal TiO2 electrodes.