Titania photonic crystal photocatalysts functionalized by graphene oxide nanocolloids

Abstract

Photonic crystal-assisted semiconductor photocatalysis has been attracting significant attention as an advanced photon management approach that combines light harvesting with the macro/mesoporous structured materials properties permitting enhanced mass transport and high adsorption. In this work, surface functionalization of well-ordered photonic band gap engineered TiO2 inverse opal films fabricated by the convective evaporation-induced co-assembly method was performed by graphene oxide nanocolloids (nanoGO). The loading of GO nanosheets was determined by the films’ macropore size, with minimal effects on their long range periodicity and photonic properties. While nanoGO deposition reduced mesoporosity of the nanocrystalline titania walls, their surface functionality was greatly improved by the abundant oxygen groups of the GO nanosheets leading to increased pollutant adsorption. Slow photon amplification in the aqueous phase methylene blue photodegradation was identified for the unmodified TiO2 photonic films under both UV–vis and Vis illumination upon spectral overlap of the low energy edge of the inverse opal stop band (in water) with the dye electronic absorption, due to (red) slow photons localized in the titania skeleton that distinctly accelerated dye photodegradation kinetics. The photocatalytic efficiency was further improved for the nanoGO functionalized TiO2 inverse opal films via the synergetic action of interfacial electron transfer from TiO2 to the GO nanosheets. Under UV–vis light, the functionalized photonic films outperformed benchmark mesoporous Aeroxide® P25 TiO2 films where nanoGO modification, despite the enhanced dye adsorption, resulted in adverse effects in photocatalytic degradation due to pore clogging. Combination of the exceptional structural and photonic properties of TiO2 inverse opals with the high adsorption capacity and charge separation afforded by GO nanocolloids is proposed as a promising modification route for the development of efficient photocatalytic films.