Nanoforest-like CdS/TiO₂ heterostructure composites: Synthesis and photoelectrochemical application

In this study, TiO₂ nanoforest films consisting of nanotubes have been synthesized by a simple hydrothermal method and a subsequent sintering technique. The hydrothermal reaction time is important for the controlling of the nanotube diameter and the specific surface area of holistic TiO₂ films. When the hydrothermal process reaction time is up to 8 hours, the diameter of the nanotube is about 10 nm, and the specific surface area of TiO₂ nanoforest films reaches the maximum. CdS nanoparticles are synthesized on TiO₂ nanoforest films by the successive ionic layer adsorption and reaction (SILAR) technique. The transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDX) mapping results verify that TiO₂/CdS heterostructures are realized. A significant red-shift of the absorption edge from 380 nm to 540 nm can be observed after the pure TiO₂ film is sensitized by CdS nanoparticles. Under irradiation of light, the current density of the optimal TiO₂/CdS photoanode is 2.30 mA⋅cm⁻² at 0 V relative to the saturated calomel electrode (SCE), which is 6 times stronger than that of the pure TiO₂ photoanode. This study suggests that the TiO₂ nanoforest consisting of interlinked pony-size nanotubes is a promising nanostructure for photoelectrochemical. (paper)