Time-resolved microwave conductivity study of charge carrier dynamics in commercially available TiO2 photocatalysts

Charge carrier dynamics in various commercially available TiO 2 photocatalysts were studied by means of the time-resolved microwave conductivity (TRMC) technique. The intensities of TRMC signals strongly depended on the photocatalyst, suggesting that the TRMC technique is potentially useful for characterizing photocatalytic activity. We found that fast charge recombination within the time resolution of the measurement system becomes dominant when one or more charges are generated primarily in a particle. We also found that TRMC signals were sensitive to particle size and that the maximum signal intensity was roughly proportional to the diameter of the particles. This tendency was explained on the basis of a model in which electron traps are located at the surface of the particles. P25, one of the best photocatalysts developed to date, showed a slight deviation from this tendency; the reason for the deviation is discussed. Charge carrier dynamics in various commercially available TiO 2 photocatalysts was studied by means of the time-resolved microwave conductivity (TRMC) technique.