Preparation And The Photoelectrochemical Property Study Of Ag Decorated TiO₂Nanotube Arrays

Titanium dioxide nanotube arrays (TiO2NTAs) have been drawn a lot of attention because of their large surface area, high photocatalytic activity, nontoxicity, vectorial charge transfer, and long-term stability against photo and chemical corrosion. However, the intrinsic wide band gap physical properties of TiO2and the high rate of the photo-generated charge carrier recombination result in weak light absorption capability in the visible light spectrum, which limits the applicability of TiO2for applications such as visible light water splitting and organic pollutant degradation.To surmount these problems, due to the effect of localized surface plasmon resonance (LSPR), silver nanoparticles (Ag NPs) were employed to modify the surface of TiO2NTAs in this paper. The effect of Ag NPs particle size on the photoelectrochemical properties of Ag/TiO2NTAs was investigated. Furthermore, based on the results of this systematic research, the size dependent photoelectronchemical performance mechanism of Ag/TiO2NTAs was proposed. The main results are as follows:1. The TiO2NTAs were fabricated by anodization in an NH4F and H3PO4mixed electrolyte. The effects of the anodization time on the morphology and the photoelectronchemical property of TiO2NTAs was investigated. The results show the satisfactory tube morphology and the highest photoelectronchemical property of TiO2NTAs when the anodization time is2h, which laid the foundation for the subsequent preparation for Ag/TiO2NTAs.2. TiO2NTAs decorated with Ag NPs of various particle sizes were fabricated by a photochemical reduction method. UV-visible diffuse reflectance spectroscopy and photoluminescence emission spectroscopy demonstrated that the Ag decorating significantly enhanced the light absorption of TiO2NTAs in the visible spectral range and improved the separation of photo-induced charge carriers in the TiO2NTAs. The photoelectrochemical properties of prepared samples were investigated by the transient photocurrent measurement (I-T) and the potential dependence of photocurrent (Ⅰ-Ⅴ) under visible light irradiation. The results show that the photoelectrochemical behavior of Ag/TiO2NTAs is dependent on the size of the Ag NPs. The maximum photoconversion efficiency of Ag/TiO2NTAs is about3 times greater than that of unmodifiled TiO2NTAs under the optimal condition.3. The mechanism of Ag NPs size dependent photoelectrochemical performance of Ag/TiO2NTAs was discussed.We propose that the enhanced photoelectrochemical properties of Ag decorated TiO2NTAs results from different ratios of light absorption to scattering caused by the localized surface plasmon resonance of the various sizes of Ag nanoparticles. The tunable photoelectrochemical properties of Ag decorated TiO2NTAs are expected to have promising applications in photoelectrochemical solar cells and other light-harvesting devices.