Photoelectrochemical Determination of Shallow and Deep Trap States of Platinum-Decorated TiO2 Nanotube Arrays for Photocatalytic Applications

Abstract

A novel insight into the effect of Pt decoration on electrochemical and photoelectrochemical behavior of TiO2 nanotube arrays (TNA) was developed in this study. TNA samples were prepared via a two-step anodization of a titanium foil and decorated with Pt by a facile photodeposition method. The formation of metallic Pt were confirmed by X-ray photoelectron spectroscopy (XPS). On the basis of our calculations, the localized states and surface states induced by Pt deposition into the bandgap of titania nanotubes, play a dominant role in trapping/detrapping charge carriers and electron transfer to electrolyte. In Pt/TNAs the appropriate electrical connection between Pt nanoparticles and TNA induces sufficiently shallow traps in the vicinity of conduction band edge of TNA which creates a fast lane for electrons toward semiconductor/electrolyte interface and decreases the density of deep trap levels compared to the pristine TNA. However, there is an optimum amount for deposited Pt. Higher amount of optimum Pt c...