  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 we report the synthesis of photonic
crystal plasmonic photocatalyst materials using Au nanoparticle-functionalized
inverse opal (IO) photonic crystals. A catalyst prepared using a visible light
responsive semiconductor (V2O5) displayed over an order of magnitude increase
in reaction rate under green light excitation ($\lambda$=532 nm) compared to no
illumination. The superior performance of Au-V2O5 IO was attributed to spectral
overlap of the electronic band gap, localized surface plasmon resonance and
incident light source. Comparing the photocatalytic performance of Au-V2O5 IO
with a conventional Au-TiO2 IO catalyst, where the semiconductor band gap is in
the UV, revealed that optimal photocatalytic activity is observed under
different illumination conditions depending on the nature of the semiconductor.
For the Au-TiO2 catalyst, despite coupling of the LSPR and excitation source at
$\lambda$=532 nm, this was 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 band gap, and exploiting slow light in the photonic
crystal to enhance photon absorption to create this synergistic type of
photocatalyst.
