Understanding charge transfer processes on metal oxides: a laser-flash-photolysis study

Abstract

In the focus of this study, mixtures of commercially available TiO2 powders were created and their photocatalytic activity concerning the acetaldehyde degradation in the gas phase was tested. Further, the lifetime of the photogenerated charge carriers was analyzed by Laser-Flash-Photolysis-Spectroscopy. The acetaldehyde degradation experiments of the mixed powders lead to positive and negative deviations from the expected weighted mean. Nevertheless, their photocatalytic activity could be correlated with the lifetime of the charge carriers. A longer charge carrier lifetime at ambient conditions correlated with a lower fractional conversion of acetaldehyde. The advantageous activities of the samples were associated with a charge transfer reaction between larger and smaller particles comparable to the antenna mechanism.

Charge carrier dynamics and reaction intermediates in heterogeneous photocatalysis by time-resolved spectroscopies

“…72 Interestingly, Sieland et al found that longer charge carrier lifetimes in TiO 2 actually correlated with lower photocatalytic conversion of acetaldehyde, although the actual reason was not clear. 73 Patrocinio reported that their TiO 2 sample exhibiting faster recombination had higher efficiencies for photocatalytic oxidation, attributed to its larger surface area that offsets poorer electronic properties. 74 However, interestingly, the sample surface area had little effect on H 2 evolution, and the efficiency of electron transfer (ET) from TiO 2 to platinum co-catalysts was the primary factor affecting photocatalytic performance for H 2 evolution.…”