Ordered Macroporous Photonic Crystal Hot Electron Plasmonic Photocatalysts

Abstract

Plasmon-enhanced photocatalysis provides opportunities for controlling chemical reaction rates, especially when the influence of the light is to enhance or alter charge transfer properties. Semiconductor photocatalysts with an inverse opal or photonic crystal structure not only provide large, open and accessible surface area, they are electrically interconnected as a porous network. This becomes a useful scaffold to dock metallic nanoparticles whose size can be tuned to absorb specific frequencies resonant with their localised surface plasmon resonance. Coupling this with the nature of the metal-semiconductor band structure (where the metal oxide is wide band gap) and exploiting certain properties of photonic crystals, more efficient photocatalysts are possible. We demonstrate semiconducting photonic crystal plasmonic photocatalysts using V2O5 and TiO2 as visible light semiconductor catalysts that showed superior performance to a conventional TiO2 support for hydrogenation of 4-nitrophenol. The approach married the photonic band gap, metal oxide semiconductor bandgap, slow photon effect and localised surface plasmon polaritons to maximum photon absorption to modulate charge transfer and electron density either in the metal nanoparticle, or the conduction band of the semiconductor to give a better photocatalyst.