Enhanced visible-light photoelectrochemical behaviour of heterojunction composite with Cu2O nanoparticles-decorated TiO2 nanotube arrays

Heterojunction composites based on n-type TiO2 nanotubes arrays (TNAs) coupled with p-type Cu2O nanoparticles were synthesized using a square wave voltammetry deposition method for in situ deposition of Cu2O nanoparticles onto the inner surfaces and interfaces of TNAs. The prepared samples were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV-vis spectroscopy. When compared with pure TNAs, the Cu2O-TNAs heterojunction composites exhibit considerably higher photocurrent density under visible-light irradiation and enhanced photocatalytic activity for the visible-light-driven photodegradation of methyl orange. Moreover, the photocurrent densities and photocatalytic activity of the Cu2O-TNAs heterostructures largely depend on the deposition potential which determines the content of the Cu2O nanoparticles. The Cu2O-TNAs prepared by the deposition potential of -1.0 V showed the highest photocurrent density (0.91 mA cm(-2)) and the largest photodegradation rate of methyl orange (88.8%) at the applied potential of 0.5 V under visible light irradiation. The enhanced photoelectrocatalytic activity can be attributed to reducing the recombination rate of the photoexcited electron-hole pairs in TNAs when coupled with Cu2O nanoparticles.