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

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.