Enhanced solar water-splitting efficiency using core/sheath heterostructure CdS/TiO₂nanotube arrays

Abstract

A novel fabrication route for core/sheath heterostructure CdS/TiO(2) nanotube arrays is proposed using ac electrodeposition for application in photoelectrochemical cells. The morphologies of the CdS/TiO(2) electrodes, which were prepared by electrochemically depositing CdS directly into anodic titanium nanotubes from an electrolyte containing Cd(2+) and S in dimethyl sulfoxide, were characterized by a field emission scanning electron microscope (FESEM). The deposited material was found to be in a hexagonal CdS structure by x-ray diffraction (XRD). The synthesized CdS/TiO(2) electrodes showed much higher photocurrent density in the visible wavelength region than pure TiO(2) nanotube arrays. We demonstrate that ac deposition voltage and time can control the CdS/TiO(2) composite architecture, which is crucial in determining the overall efficiency of the water-splitting reaction. The maximum photocurrent density was obtained with the core/sheath heterostructure CdS/TiO(2) nanotube arrays, which were fabricated by deposition of CdS at 5 V for 30 min with 2.5 microm tube length.

Photocatalytical Properties of TiO₂ Nanotubes

“…In recent years considerable effort has been invested in improving the response of TNTs to visible light, mainly including the sensitization with dye [93,94] or polymer [95], loading with noble metal atom [96,97], and coupling with narrow band gap semiconductor [98,99]. In sensitized cases, charge injection from the CB of the narrowband gap semiconductor to that of TNTs can lead to efficient and longer charge separation by minimizing the electron-hole recombination.…”

High Density n-Si/n-TiO2Core/Shell Nanowire Arrays with Enhanced Photoactivity

“…[12][13][14] Semiconductor heterojunctions can absorb different region of the solar spectrum. [15][16][17][18] The advantage of composite structures is that each semiconductor need to satisfy one energetic requirement: matching the conduction band minimum (CBM) or VBM with either the H 2 reduction or O 2 oxidation potential.…”

Synthesis of Inorganic Nanotubes

“…Typical examples of such nanostructures are the following: Integration of ZnO nanotubes with ordered nanorods, [227] conversion of ZnO nanorod arrays into ZnOÀZnS nanocable and ZnS nanotube arrays, [228] core-sheath heterostructure CdSÀTiO 2 nanotube arrays, [229] ZnS nanotube-In nanowire core-shell heterostructures, [230] ZnOÀZnS core-shall nanotube arrays, [231] Cu nanotube-Bi nanowire heterojunctions, [232] carbon nanotubes in TiO 2 nanotubes, [233] TiO 2 ÀPt coaxial nanotube arrays, [234] Sn nanowires on TiO 2 nanotubes, [235] Fe 2 O 3 ÀTiO 2 nanorod-nanotube arrays, [236] SiO 2 ÀTa 2 O 5 core-shell nanowires and nanotubes, [237] multi-walled BCN-carbon nanotube junctions, [238] and BN nanotubes with periodic iron nanoparticles. [239] …”