Electrochemical Deposition of Cu-Nanoparticle-Loaded CdSe/TiO₂ Nanotube Nanostructure as Photoelectrode

Surface alteration of titanium dioxide nanotube arrays by semiconductor and metal is one of the pathways to narrow the wide bandgap of titanium dioxide and thereby increase its absorption in the visible region. Cu-CdSe-cosensitized titanium dioxide nanotube arrays (Cu-CdSe/TiO₂ nanotube) have been produced for use as photoanodes in photoelectrochemical cells. Ordered Cu-CdSe/TiO₂ nanotubes were successfully prepared by varying the deposition time (1 min to 4 min) using a facile three-step electrochemical method. The composition, morphological structure, and visible-light response were characterized by field-emission scanning electron microscopy, x-ray diffraction (XRD) analysis, energy-dispersive x-ray spectroscopy, ultraviolet–visible (UV–Vis) diffusion reflection spectroscopy (DRS), and photoelectrochemical testing. XRD analysis demonstrated that sensitization using Cu-CdSe did not destroy the structure of the anatase-phase nanotube arrays, with the formation of copper nanoparticles composed of cubic-like particles with increasing deposition time. UV–Vis DRS of the Cu-CdSe/TiO₂ nanotubes revealed a red-shift of the photoresponse towards the visible-light region, characterized by bandgap narrowing and improved photoefficiency. The optimal photoelectrochemical performance was observed when depositing Cu nanoparticles for 1 min, surpassing that of pristine titania nanotube arrays and other materials prepared under different conditions. The features of these photoanodes for many applications include easy synthesis, low cost, high efficiency for visible lighting, and good stability. The present work demonstrates a feasible modification of TiO₂ nanotubes with Cu-CdSe to form potential photoanodes for solar conversion devices.