Enhancing the Photocatalytic Activity by Tailoring an Anodic Aluminum Oxide Photonic Crystal to the Semiconductor Catalyst: At the Example of Iron Oxide

Abstract

Photonic crystals (PhCs) are interesting structures for photocatalytic applications because of their capability of harnessing distinct forms of light–matter interactions within the PhCs. Of all these, overlapping one of the photonic stopband’s (PSB) edge with the absorption of the PhC material or adsorbed molecules improves their excitation and generated charge carriers can subsequently induce photocatalytic reactions. The PSB position of anodic aluminum oxide PhCs (AAO-PhCs) can be easily adjusted by modifying the anodization profile. Herein, AAO-PhCs are designed to match the band gap of a model semiconductor enabling a general photocatalytic activity enhancement independent of the chemical to be decomposed. Fe₂O₃, as an example photocatalyst, is coated onto AAO-PhCs to demonstrate efficient photocatalytic systems by utilizing the slow photon effect. Tailored Fe₂O₃-AAO-PhCs with their PSB edge at 564 nm matching the Fe₂O₃ band gap exhibit generally enhanced degradation of three different organic dyes while a significant activity decrease is observed when the PSB edge does not overlap with the Fe₂O₃ absorption. Furthermore, photocatalyst degradation can be reduced down to only 4% activity loss over six consecutive measurements by an ultra-thin alumina coating.