Photoelectrochemical and structural properties of TiO2 nanotubes and nanorods grown on FTO substrate: Comparative study between electrochemical anodization and hydrothermal method used for the nanostructures fabrication

Abstract

Titanium dioxide in the form of one-dimensional (1D) nanostructure arrays represent widely studied morphological arrangement for light harvesting and charge transfer applications such as photocatalysis and photoelectrochemistry (PEC). Here we report a comparative structural and PEC study of variously grown 1D TiO2 nanostructures including i) nanorod arrays prepared by a hydrothermal method (TNR), ii) nanotube arrays fabricated by a two-step hydrothermal method using a ZnO nanorod array film as a template (THNT) and finally iii) nanotubes grown by self-organized electrochemical anodization of Ti films deposited on the FTO substrate (TNT). These nanostructures are assumed to be utilized as photoanodes in PEC water splitting devices. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), TEM images and UV–vis absorption spectra were used to characterize TiO2 nanostructures. The SEM and TEM morphology images revealed that the main difference among the nanostructures grown on the FTO are the shape and diameter of the individual nanotubes/nanorods and also the array’s density in the range of TNR>THNT>TNT and the degree of organization in the range of TNT>TNR>THNT. The obtained photocurrents at 0V vs. Ag/AgCl increased in the order of THNT (110μAcm−2)<TNT (185μAcm−2)<TNR (630μAcm−2). Extended electron lifetime and light absorption shifted to the longer wavelengths were attributed to the enhanced PEC performance of TNR.