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 O₂ and H₂O₂ in 1.0 M NaOH. However, the response is increased gradually by repeated application of a triangular waveform within the approximate potential limits of O₂ response (ca. −1.5 to −0.7 V vs. SCE). This same voltammetric pretreatment applied for excessive periods results in formation of golden films on the Ti surfaces that are active for reduction of O₂ and H₂O₂. Levich plots of cathodic current for O₂ 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 kinetics. Ring-disk data demonstrate that a small amount of H₂O₂ is produced throughout the potential region for O₂ reduction and H₂O₂ is concluded to be an intermediate product in the O₂-reduction mechanism. These observations are consistent with those reported previously for single-crystal TiO₂ electrodes.