Electrochemical investigation of the energetics of particulate titanium dioxide photocatalysts. The methyl viologen-acetate system

Addition of methyl viologen (MV2+) enhances the anodic currents observed for Ti02 suspensions under illumination by trapping of photogenerated electrons with formation of MV’.. The magnitude of the photocurrent depends upon the relative location of the semiconductor Fermi level and Erdon of the MV2+/MV+. couple. The location of the Fermi level in the anatase powders was estimated as -0.05 V vs. NHE ( p H 0) based on the observed variation of photocurrent with p H . T h e shift in the quasi-Fermi level with light intensity is also discussed.