Pyramidal Metal–dielectric hybrid-structure geometry with an asymmetric TiO2 layer for broadband light absorption and photocatalytic applications

Highlights: • A pyramidal metal–dielectric hybrid–structure geometry for solar water oxidation offered high broadband light absorption. • TiO₂ was obliquely deposited on the pyramidal Au film, leading to asymmetrically thick pyramids. • With the Au nanoparticles, the light absorption in the entire UV–visible region significantly increased to > 90%. • The band at the interface of Au and TiO₂ was tuned, providing efficient transport pathways for the photogenerated carriers. • The photocurrent density was remarkably enhanced (~0.16 mA/cm²) by 3.4 times compared to the flat TiO₂ layer. In this study, a pyramidal metal–dielectric hybrid-structure geometry with high broadband light absorption was prepared and applied as a photoelectrode for solar water oxidation. TiO₂ was obliquely deposited on the pyramidal Au film, leading to asymmetrically thick pyramids. With the decoration of Au nanoparticles, the light absorption in the entire UV–visible region significantly increased to > 90%, which was examined by three-dimensional finite-difference time-domain simulations and confirmed by confocal spectral mapping techniques. By the introduction of Ti as the insertion layer, the alignment of bands at the TiO₂/Au film interface was tuned, thereby promoting the separation of photogenerated carriers via the efficient transport of electrons to the Au film. This transport led to a remarkable enhancement in the photocurrent density (~0.16 mA/cm²) by 3.4 times compared to that observed for a flat TiO₂ layer.