Results are reported on the flat band potential Vfb of the contact TiO2/CH3CN. The informations were taken from capacitance/voltage and photocurrent/voltage measurements. As electrolyte either pre‐dried CH3CN or various mixtures of dried CH3CN with H2O were used. It was found that both the addition of H2O and illumination with band gap light affect Vfb considerably. – It could be shown that Vfb‐values determined from photocurrent/potential measurements differ up to 2 V from values evaluated from capacitance/potential measurements taken on unilluminated electrodes. However, Vfb‐values obtained from capacitance measurements on pre‐illuminated electrodes agree well with data from photocurrent measurements. The results are discussed in terms of alterations of the inner Helmholtz plane. Finally, consequences of the observed Vfb shifts on the charge transfer process are outlined.

It is reported on changes of the flat band potential V, at the n-TiO,/CH,CN junction upon water addition. It is shown that these shifts are related to the increasing density of H+ ions in the CH,CN electrolyte by adding water to it. The results are discussed in terms of specific adsorption of H + ions at the TiO, electrode that affects the potentiaVcapacitance distribution of the junction.

We report on the optical absorbance A and the photoelectrochemical quantum efficiency η of Titanium oxide samples modified by ion implantation and reductive/oxidative annealing. Rutherford‐Backscattering spectra were taken to probe the depth profile of implanted Kr+. It is shown that A varies drastically upon modification. Generally, with increasing Ti/O ratios the absorbance decreases. The observed decrease in A upon implantation of stoichiometric TiO2 is attributed to an increase of the Ti/O ratio. The suggested explanation takes into account the formation of Ti3+ ‐ O vacancy complexes which influence the electronic structure of TiO2. Furthermore it is shown that changes of A give rise to conductivity changes. This reflects changes in ND, the doping density, εr, the relative dielectric constant, and lp, the mean free diffusion length of minority carriers. The observed photoelectrochemical quantum efficiency η of modified samples is discussed in terms of model calculations which take into account changes of ND, εr, lp and the absorption coefficient α. Recombination losses of photo‐produced electron‐hole‐pairs via band gap states introduced by the implanted ions are also discussed.

It is shown that Avaries drastically upon modification.