Role of Dissociatively Adsorbed Water on the Formation of Shallow Trapped Electrons in TiO2 Photocatalysts

The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Anton LitkeJan P Hofmann

Abstract

The mismatch between short lifetimes of free charge carriers and slow kinetics of surface redox reactions substantially limits the efficiency of most photocatalytic systems. Hence, the knowledge of trapping and recombination of photogenerated electrons and holes at different time scales is key for a rational optimization of photocatalytic materials. In this study, we used subsecond time-resolved diffuse-reflectance FTIR spectroscopy to investigate how energy and intensity of the incident irradiation affect the dynamics of photogenerated charge carriers in TiO2 P25 photocatalysts subjected to different pretreatments and how shallow trapped electrons (STE) are formed under these conditions. Intensity-dependent measurements demonstrated that electrons and holes generated by 325 and 409 nm irradiation undergo bimolecular and trap-assisted recombination, respectively. Analysis of characteristic times of photogenerated electron absorption rise and decay indicated that the apparent charge carrier dynamics at the time scale of seconds to minutes relate to chemical trapping of photogenerated electrons and holes. The presence of dissociatively adsorbed water on the oxide surface was required for efficient STE formation. This suggests tha...Continue Reading

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Apr 18, 2017·The Journal of Physical Chemistry. C, Nanomaterials and Interfaces·Anton LitkeJan P Hofmann

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Methods Mentioned

BETA
electron scattering
infrared spectroscopy
transmission electron microscopy
irradiate
electron paramagnetic resonance

Software Mentioned

Bruker OPUS
Origin

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