Plasmon Resonant Enhancement of Photocatalytic Water Splitting Under Visible Illumination

TLDR

The study demonstrates that integrating plasmonic Au nanoparticles with TiO₂ enhances photocatalytic water splitting under visible light. The enhancement arises from plasmon‑induced local electric field amplification at the TiO₂ surface, boosting electron‑hole pair generation within the short exciton diffusion length. Visible‑light experiments show up to a 66‑fold increase in water‑splitting activity, while ultraviolet light reduces activity fourfold, indicating that plasmonic near‑field enhancement boosts electron‑hole generation and that further optimization could yield even larger gains.

Abstract

We demonstrate plasmonic enhancement of photocatalytic water splitting under visible illumination by integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO2. Under visible illumination, we observe enhancements of up to 66× in the photocatalytic splitting of water in TiO2 with the addition of Au nanoparticles. Above the plasmon resonance, under ultraviolet radiation we observe a 4-fold reduction in the photocatalytic activity. Electromagnetic simulations indicate that the improvement of photocatalytic activity in the visible range is caused by the local electric field enhancement near the TiO2 surface, rather than by the direct transfer of charge between the two materials. Here, the near-field optical enhancement increases the electron-hole pair generation rate at the surface of the TiO2, thus increasing the amount of photogenerated charge contributing to catalysis. This mechanism of enhancement is particularly effective because of the relatively short exciton diffusion length (or minority carrier diffusion length), which otherwise limits the photocatalytic performance. Our results suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized.