Water Splitting on Composite Plasmonic-Metal/Semiconductor Photoelectrodes: Evidence for Selective Plasmon-Induced Formation of Charge Carriers near the Semiconductor Surface

TLDR

High charge‑carrier recombination limits photocatalytic water‑splitting rates on oxide semiconductors. The study demonstrates that coupling a semiconductor photocatalyst with tailored plasmonic‑metal nanostructures can significantly reduce charge‑carrier recombination. Plasmonic nanostructures generate resonant surface plasmons that concentrate electromagnetic energy at their interfaces, enabling selective generation of charge carriers in the adjacent semiconductor. Evidence shows that the localized electric fields of the plasmonic nanostructures selectively generate electron/hole pairs in the semiconductor’s near‑surface region, facilitating rapid separation and migration to the surface for efficient photocatalytic reactions.

Abstract

A critical factor limiting the rates of photocatalytic reactions, including water splitting, on oxide semiconductors is the high rate of charge-carrier recombination. In this contribution, we demonstrate that this issue can be alleviated significantly by combining a semiconductor photocatalyst with tailored plasmonic-metal nanostructures. Plasmonic nanostructures support the formation of resonant surface plasmons in response to a photon flux, localizing electromagnetic energy close to their surfaces. We present evidence that the interaction of localized electric fields with the neighboring semiconductor allows for the selective formation of electron/hole (e−/h+) pairs in the near-surface region of the semiconductor. The advantage of the formation of e−/h+ pairs near the semiconductor surface is that these charge carriers are readily separated from each other and easily migrate to the surface, where they can perform photocatalytic transformations.