Probing significant light absorption enhancement of titania inverse opal films for highly exalted photocatalytic degradation of dye pollutants

• Continuous TiO2 inverse opal films by sol–gel method.
• High stability of photonic crystal structures of TiO2 inverse opal films under high temperature treatment.
• Highly enhanced photocatalytic activity of TiO2 inverse opal films.
• Slow photon effect in photodegradation of dye pollutants in aqueous solution.
• Light absorption enhanced and further highly enhanced photocatalytic performance by slow photon effect.

The continuous titania inverse opal (TiO2-IO) films have been prepared by sol–gel infiltration method and calcined at different temperatures. The morphologies of the TiO2 inverse opal films remain unchanged under high temperature treatment. XRD patterns reveal an anatase crystalline phase between 550 and 900 °C and a mixture of anatase and rutile phase at 1000 °C. Comparing with the mesoporous TiO2 films obtained under the same conditions, all the TiO2 inverse opal films demonstrate a highly enhanced photocatalytic activity in photodegradation of rhodamine B (RhB) as dye pollutant model in aqueous solution. In spite of the fact that the TiO2 inverse opal films with open macroporous structures and possible light scattering effect of the wavelengths can result in the higher photocatalytic activity in the degradation of the dye pollutant, the phenomenon of the slow photon occurring in the TiO2 inverse opal photonic crystals can explain the extraordinary enhancement of the photocatalytic activity. In consequence, the TiO2-IO-700, TiO2-IO-550 and TiO2-IO-800 films show the best photocatalytic performance mainly due to the slow photon effect at the light incident angle at 0°, 20° and 45°, respectively, a direct proof of light absorption enhancement due to the slow photon effect. The slow photon effect in TiO2 inverse opals to enhance light absorption and further to enhance photocatalysis is very important for further potential applications in solar cells and other processes linked to the light absorption.

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