Photochemical Quartz Crystal Microbalance Study of the Nanocrystalline Titanium Dioxide Semiconductor Electrode/Water Interface:  Simultaneous Photoaccumulation of Electrons and Protons

Photochemical quartz crystal microbalance (PQCM) studies of nanocrystalline titanium dioxide films show evidence of charge-compensating cation intercalation during photolytically induced accumulation layer formation. The manifestation and magnitude of mass uptake (intercalation) are dependent, respectively, on the illumination and intensity of illumination provided. Isotope experiments performed in H 2 O and D 2 O unambiguously identify the cations as protons and deuterons. The experiments extend earlier experiments with dark TiO 2 (and other metal oxide semiconductors) that have implicated cation intercalation as the primary process involved in charge compensation under accumulation conditions.