Diameter-Tunable CdSe Nanotubes from Facile Solution-Based Selenization of Cd(OH)2 Nanowire Bundles for Photoelectrochemical Cells

Diameter-tunable CdSe nanotubes are synthesized via a sacrificial template approach in solution phase by reacting Cd(OH)2 nanowire bundles with NaHSe. The sacrificial templates of diameter-controlled Cd(OH)2 nanowire bundles undergo an interdiffusion process between Se2− and Cd2+ species, and subsequently core/shell structures of Cd(OH)2/CdSe are formed at intermediate states. The crystalline CdSe hollow nanotubes are finally formed when all Cd reagent sources are chalcogenized with Se in the solution phase, and their diameter can be readily controlled from ca. 20 to 60 nm depending on the dimension of nanowire bundle templates. With heat treatment at 300 °C, crystallinity of the CdSe nanotubes can be enhanced with removal of amorphous selenium present on the nanotube surface, which shows a photo-conversion efficiency of 0.57% in CdSe/polysulfide liquid-junction solar cell along with a bandgap energy of 1.89 eV. A possible scheme for the CdSe nanotube synthesis from the template of Cd(OH)2 nanowire bundle...