Semiconducting Metal Oxide Photonic Crystal Plasmonic Photocatalysts

Plasmonic photocatalysis has facilitated rapid progress in enhancing photocatalytic efficiency under visible light irradiation. Poor visible-light-responsive photocatalytic materials and low photocatalytic efficiency remain major challenges. Plasmonic metal–semiconductor heterostructures where both the metal and semiconductor are photosensitive are promising for light harvesting catalysis, as both components can absorb solar light. Efficiency of photon capture can be further improved by structuring the catalyst as a photonic crystal. Here, the synthesis of photonic crystal plasmonic photocatalyst materials using Au nanoparticle-functionalized inverse opal (IO) photonic crystals is reported. A catalyst prepared using a visible-light-responsive semiconductor (V₂O₅) displayed over an order of magnitude increase in reaction rate under green light excitation (λ = 532 nm) compared to no illumination. The superior performance of Au-V₂O₅ IO is attributed to spectral overlap of the electronic bandgap, localized surface plasmon resonance, and incident light source. For the Au-TiO₂ catalyst, despite coupling of the LSPR and excitation source at λ = 532 nm, this is not as effective in enhancing photocatalytic activity compared to carrying out the reaction under broadband visible light, which is attributed to improved photon adsorption in the visible by the presence of a photonic bandgap, and exploiting slow light in the photonic crystal to enhance photon absorption to create this synergistic type of photocatalyst.