Photocatalytic Activities Enhanced by Au-Plasmonic Nanoparticles on TiO₂ Nanotube Photoelectrode Coated with MoO₃

Although TiO₂ was formerly a common material for photocatalysis reactions, its wide band gap (3.2 eV) results in absorbing only ultraviolet light, which accounts for merely 4% of total sunlight. Modifying TiO₂ has become a focus of photocatalysis reaction research, and combining two metal oxide semiconductors is the most common method in the photocatalytic enhancement process. When MoO₃ and TiO₂ come into contact to form a heterogeneous interface, the photogenerated holes excited from the valence band of MoO₃ should be transferred to the valence band of TiO₂ to effectively reduce the charge recombination of photogenerated electron–hole pairs. This can efficiently separate the pairs and promote photocatalysis efficiency. In addition, photocurrent enhancement is attributed to the strong near-field and light-scattering effects from plasmonic Ag nanoparticles. In this work, we fabricated MoO₃-coated TiO₂ nanotube heterostructures with a 3D hierarchical configuration through two-step anodic oxidation and a facile hydrothermal method. This 3D hierarchical structure consists of a TiO₂ nanotube core and a MoO₃ shell (referred to as TNTs@MoO₃), as characterized by field emission scanning electron microscopy and X-ray photoelectron spectroscopy.