Photonic Crystal Coupled TiO2/Polymer Hybrid for Efficient Photocatalysis under Visible Light Irradiation

Abstract

Inverse TiO₂ opal photonic crystal coupled TiO₂/poly(3-hexylthiophene) (bilayer TiO₂/P3HT) was structured on FTO substrate for efficient photocatalysis under visible light irradiation (λ > 400 nm). We expected that the photocatalytic capability of this hybrid photocatalyst could be enhanced by the efficient visible light absorption owing to the photonic crystal structure and effective charge separation owing to the unique heterojunction built between TiO₂ and P3HT. The bilayer TiO₂/P3HT photocatalyst was prepared first by depositing inverse TiO₂ opal on FTO substrate via replicating polystyrene opal, followed by spin coating a layer of TiO₂ nanoparticles on the inverse TiO₂ opal. The as prepared bilayer TiO₂ was modified by P3HT via dipping method. Environmental scanning electron microscopy (ESEM) images demonstrated that the as prepared photocatalyst was composed of inverse TiO₂ opal layer and TiO₂ nanoparticles layer. The UV−vis diffuse reflectance spectra showed that the optical absorption for bilayer TiO₂/P3HT was more intensive than for pristine TiO₂ nanoparticle/P3HT (NP-TiO₂/P3HT) in the range of 400−650 nm. The enhanced generation of photocurrent under visible light irradiation (λ > 400 nm) was observed using the bilayer TiO₂/P3HT. The results of photocatalytic experiments under visible light irradiation revealed that the pseudofirst-order kinetic constant of photocatalytic degradation of methylene blue using the bilayer TiO₂/P3HT was 2.08 times as great as that using NP-TiO₂/P3HT, showing the advantage of the unique structure in the bilayer TiO₂/P3HT for efficient photocatalysis.