Augmented Photoelectrochemical Efficiency of ZnO/TiO2 Nanotube Heterostructures

Abstract

ZnO/TiO2 nanotube heterostructures have been fabricated by electrodeposition of ZnO microcrystals over electrochemically anodized TiO2 nanotube arrays. The resulting ZnO/TiO2 nanotube heterostructures showed enhanced photocurrent density of 5.72 mA cm−2, about 1.5 times the value of 3.68 mA cm−2 shown by bare compact TiO2 nanotubes. This enhanced photocurrent density of the ZnO/TiO2 nanotube heterostructures is due to high electron mobility in the ZnO crystals, thereby decreasing the electron–hole recombination process, good interfacial quality between the ZnO and TiO2 structures, and a proposed smooth charge-transfer mechanism due to band bending at the interface. The morphological features of the as-prepared heterostructures were determined by field-emission scanning electron microscopy (FESEM). The crystallinity and phase purity of the samples were confirmed by x-ray diffraction (XRD) analysis. The light absorption properties of the prepared samples were investigated by ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). The photoelectrochemical efficiency of bare and ZnO-modified TiO2 nanotube heterostructures was determined by electrochemical analyzer.