Development of inverse opal titania films for efficient photocatalysis

Abstract

Efficient light harvesting is considered a promising approach towards the commercialization of heterogeneous photocatalysis. Accordingly, photonic crystals might be a perfect example, but their fabrication might be challenging. In this study, inverse opal titania (IOT) films were fabricated via a co-assembly approach using a titania mixture sol containing both amorphous and crystalline titania. This method enables the preparation of highly ordered, crack-minimized structures by optimizing synthesis parameters. The obtained films were characterized by various methods (XRD, SEM, UV/vis) and tested towards photocatalytic generation of hydroxyl radicals (via hydroxylation of terephthalic acid). It has been found that both film thickness and crack-free morphology are decisive for photocatalytic performance. Interestingly, the irradiation angle influences not only optical properties (photonic bandgap (PBG) wavelength) but also overall photocatalytic activity. It has been found that 20° is the best angle of irradiation, at which additional bands are formed, corresponding to intrinsic photoabsorption by titania. Moreover, it is proposed that by simple change in irradiation angle, photonic properties could be tuned, allowing both photocatalytic activity enhancement and mechanism investigations.