Identification and characterization of titania photocatalyst powders using their energy-resolved distribution of electron traps as a fingerprint

Here we report identification of powders of titania, one of the most important metal oxides, with their energy-resolved distribution of electron traps (ERDT), as a fingerprint, measured by reversed double-beam photoacoustic spectroscopy (RDB-PAS). The ERDT patterns combined with conduction-band bottom (CBB) position data measured by ordinary PAS for various titania powders and other metal-oxide powders were different depending on the kind of sample. The degree of coincidence (zeta) of ERDT/CBB patterns was evaluated for a given pair of samples as a product of each degree of coincidence for ERDT-pattern matching, total density of electron traps and CBB position. Titania samples collected from close positions in a container exhibited high values of zeta, while samples with different code names showed low values of zeta, except for pairs of samples prepared in the same way but coded differently. It was shown that the higher was the values of zeta, the higher was the degree of coincidence for photocatalytic activity of titania samples. ERDT/CBB-pattern arrays arranged in the order of photocatalytic activities in three reaction systems suggested preferable patterns for each photocatalytic reaction.