Effects of Calcination Condition on Photocatalytic Properties of Nano-TiO2/Opal Composite and Its Mechanism

Nanocrystalline TiO2 particles immobilized on opal by a hydrolysis precipitation method are used as a novel catalyst in photocatalysis. Effects of crystalline and size, BET specific surface area and porous properties on the photoactivity were investigated by characterizing samples obtained under various calcination temperatures and periods. Results reveal that there is still no evidence of rutile phase in XRD patterns when the calcination temperature increases to 800 degrees C. This indicates that the opal support impedes the phase transformation. The photocatalytic reactivity of this nano-TiO2/opal composite catalyst was evaluated by degrading Rhodamine B (RhB) under ultraviolet light. The sample calcined at 600 degrees C for 2 h exhibits the smaller crystalline size and larger specific surface area with a concomitant higher activity of 97.24% for RhB degradation by 4 h irradiation under 250 W Hg lamp.