Reactivation of passive titanium: the enhancement of O2 evolution after potentiodynamic cyclings

Titanium oxide films were grown potentiodynamically at 50 mV s-1 from -1.1 up to 10.0 V, at room temperature (23±1 °C) in H3PO4/NaH2PO4 aqueous solutions of ionic strength 0.5 mol L-1 and pH 3.0. After the oxide growth, the passive electrode was subjected to different repetitive potentiodynamic cycles at 50 mV s-1 between pre-set cathodic (Es,c) and anodic (Es,a) switching potentials. The changes in the electrochemical behaviour of the passive electrode, specially that of the O2 evolution reaction, were followed as a function of the number of cycles and of the limiting negative potential value used, Es,c. The enhancement of the oxygen reaction rate occurring with the repetitive potential sweeps might be due to an increase of both the oxide conductivity and the porous-oxide surface area.