Ag plasmonic enhancement of visible-light photoelectrocatalytic activity for defect-sensitized TiO2 nanotube arrays

We report the large-scale synthesis of monodisperse Ag nanoparticles and their homogeneous assembly into TiO2 nanotube arrays (TNAs) for enhancing the visible-light photoelectrocatalytic (PEC) activity of the photoanodes. Electron beam irradiation reduction was used to synthesize monodisperse mesoporous Ag nanoparticles, composed of smaller nanocrystals, with the aid of PVP surfactant. Ag nanoparticles exhibit an absorption band centered at 410 nm, originating from localized surface plasmon resonance (LSPR). To explore LSPR effects on the visible-light PEC performance of TNAs, we prepared defect-sensitized TNAs by anodic oxidization, followed by a poor-oxygen annealing treatment to induce a wide range of visible-light response owing to the incorporation of Ti3+ defects. A vacuum-assisted filling method was used to assemble Ag nanoparticles into the defect-sensitized TNAs. Compared with unfilled TNAs, a 2.5-fold enhancement in the visible-light PEC activity was observed in the composite photoanodes, which is attributed to LSPR-induced absorption enhancement in a wavelength range of 400–450 nm, as well as to the effective suppression of the recombination of photoexcited electrons and holes through the Ag-TiO2 Shockley junction.

► Monodisperse Ag NPs were synthesized by electron beam irradiation.
► Ag NPs were deposited uniformly onto the defect-sensitized TNAs by the vacuum-assisted filling method.
► A 2.5-fold enhancement in the visible-light PEC activity was observed in the composite photoanodes.
► The mechanism for enhancing visible light absorption by the silver nanoparticle-loaded nanotubes was proposed.