Electrochemical Investigation of Traps in a Nanostructured TiO2 Film

Electron traps at the nanostructured TiO2 (anatase)/aq. electrolyte interface were studied by electrochem. methods. The transient current decays at different potentials pos. of the flatband potential clearly illustrate the trap-filling process. The more neg. the potential, the shorter the trap-filling period. Most traps locate pos. of -0.9 V vs. Ag/AgCl at pH 13, or pos. of -0.3 V vs. Ag/AgCl at pH 4.7. Probably the trap distribution as a function of potential is directly proportional to dQ/dU, i.e., to the c.d. in a linear sweep voltammetry expt. The trap densities in aq. electrolytes are 4 × 1011 cm-2 (microscopic area) at pH 4.7 and 5 × 1013 cm-2 (microscopic area) at pH 13. The pH dependency of the trap d. indicates that traps studied are surface-related.