Semiconducting Metal Oxide Photonic Crystal Plasmonic Photocatalysts

TL;DR

This paper reports the development of photonic crystal plasmonic photocatalysts using Au nanoparticle-functionalized inverse opal structures, demonstrating significantly improved visible-light photocatalytic efficiency through spectral overlap and photonic band gap effects.

Contribution

It introduces a novel synthesis of inverse opal photonic crystal plasmonic photocatalysts with enhanced visible-light response and compares performance with traditional catalysts, highlighting the role of photonic structures.

Findings

Au-V2O5 IO catalyst shows over tenfold increase in reaction rate under green light.

Photonic band gap enhances photon absorption and photocatalytic activity.

Optimal illumination conditions depend on semiconductor band gap and photonic structure.

Abstract

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.