The cathodic electrochemical behavior of nanosized sols of TiO2 on mer
cury electrodes in aqueous perchloric acid consists of two processes.
The first, at more positive potential, is ascribed to the reduction of
soluble Ti(IV) species. The nature of the second process, which does
appear to involve the sole directly, has not been determined. However,
it may involve the reduction of hydrogen ion adsorbed on the particle
s, as suggested by Heyrovsky, Jirkovsky, and Struplova-Bartackova.