Shape-dependent performance of gold nanocrystals supported on TiO2 for photoelectrochemical water oxidation under different radiations

Abstract

A number of studies are documented for enhanced solar energy conversion of titanium dioxide (TiO2) by surface modification with gold (Au) nanostructures. Herein, Au nanocrystals of different geometry (spherical, cubes, triangles and wires) are synthesized and immobilized on TiO2 (bare and nitrogen–doped) surface. The shape–dependent performance of the as-prepared photocatalysts is evaluated by studying water oxidation, both under UV–visible and visible illuminations. As expected, a strong dependency of PEC performance on the shape of Au nanocrystals is discerned. Also, the trend of performance under UV–visible is different than that of visible radiation, suggesting a distinct charge transport mechanism. In addition, the photocatalytic performance increases under visible light while decreases under UV–visible with increasing Au loading. A schematic is proposed showing a likely interfacial electron transfer reaction between Au nanostructures and TiO2, depending on illuminating wavelength. The performance variation in the as-prepared photoelectrodes is correlated to particle size, optical properties and electrical conductivity.