Positioning the Water Oxidation Reaction Sites in Plasmonic Photocatalysts.

Plasmonic photocatalysis, stemming from the effective light absorbance and confinement of surface plasmons, provides a pathway to enhance solar energy conversion. Although the plasmonic hot electrons in water reduction have been extensively studied, exactly how the plasmonic hot holes participate in the water splitting reaction has not yet been well understood. In particular, where the plasmonic hot holes participate in water oxidation is still illusive. Herein, taking Au/TiO2 as a plasmonic photocatalyst prototype, we investigated the plasmonic hot holes involved in water oxidation. The reaction sites are positioned by photodeposition together with element mapping by electron microscopy, while the distribution of holes is probed by surface photovoltage imaging with Kelvin probe force microscopy. We demonstrated that the plasmonic holes are mainly concentrated near the gold-semiconductor interface, which is further identified as the reaction site for plasmonic water oxidation. Density functional theory also corroborates these findings by revealing the promotion role of interfacial structure (Ti-O-Au) for oxygen evolution. Furthermore, the interfacial effect on plasmonic water oxidation is validated by other Au-semiconductor photocatalytic systems (Au/SrTiO3, Au/BaTiO3, etc.).

Unusual Charge Distribution on the Facet of a SrTiO3 Nanocube under Light Irradiation.

Spatial charge separation has already been realized between different facets of a single crystal. However, how the photogenerated charges distribute on one facet of a single crystal is still unknown. In this work, we found that the distribution of photogenerated charges on a SrTiO3 nanocube varies with the light intensity. Photogenerated holes tend to transfer to the edges and corners of the crystal under weak illumination, indicating that a spatial charge separation takes place on the same facet of the SrTiO3 nanocube. Based on this effect, oxidation and reduction cocatalysts can be respectively photodeposited on the edges and central areas of one facet. The separated dual-cocatalysts lead to a remarkable enhancement in photocatalytic overall water splitting. These findings reveal that the spatial charge separation can happen even on the same facet.