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

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.