Enhancing the photoelectrochemical response of TiO_2 nanotubes through their nanodecoration by pulsed-laser-deposited Ag nanoparticles

摘要

We report on the pulsed laser deposition (PLD) based nanodecoration of titanium dioxide (TiO_2) nanotube arrays (NTAs) by Ag nanoparticles (NPs). We focus here on the investigation of the effect of the number of laser ablation pulses (N_(LP)) of the silver target on both the average size of the Ag-NPs and the photoelectrochemical conversion efficiency of the Ag-NP decorated TiO_2-NT based photoanodes. By varying the N_(LP), we were able to not only control the size of the PLD-deposited Ag nanoparticles from 20 to ∼50 nm, but also to increase concomitantly the surface coverage of the TiO_2 NTAs by Ag-NPs. The red-shifting of the surface plasmon resonance peak of the PLD-deposited Ag-NPs deposited onto quartz substrates confirmed the increase of their size as the N_(LP) is increased from 500 to 10 000. By investigating the photo-electrochemical properties of Ag-NP decorated TiO_2-NTAs, by means of linear sweep cyclic voltammetry under UV-Vis illumination, we found that the generated photocurrent is sensitive to the size of the Ag-NPs and reaches a maximum value at N_(LP) =500 (i.e.,; Ag-NP size of ∼20 nm). For N_(LP) = 500, the photoconversion efficiency of the Ag-NP decorated TiO_2-NTAs is shown to reach a maximum of 4.5% (at 0.5 V vs Ag/AgCl). The photocurrent enhancement of Ag-NP decorated TiO_2-NTAs is believed to result from the additional light harvesting enabled by the ability of Ag-NPs to absorb visible irradiation caused by various localized surface plasmon resonances, which in turn depend on the size and interdistance of the Ag nanoparticles.