Green synthesis of bismuth sulfide nanostructures with tunable morphologies and robust photoelectrochemical performance

Abstract

Manipulating the morphology of chalcogenide semiconductor crystals to tailor their shape- and size-dependent properties is much desired but remains a grand challenge. Herein, we for the first time develop a green, facile and surfactant-free hydrothermal approach for the synthesis of bismuth sulfide (Bi₂S₃) with highly tunable morphologies in H₂WO₄ aqueous solution. The H₂WO₄ is prone to balance the concentration of Bi³⁺ to S²⁻ in aqueous solution, thus modulating the nucleation and epitaxial growth of Bi₂S₃. Specifically, in the presence of lower H₂WO₄ concentration, the low number of Bi₂S₃ nuclei facilitates the preferred growth of nanorod structures along the [001] direction, while the Bi-deficient, S-rich conditions in higher H₂WO₄ concentration give rise to Bi₂S₃ nanotubes, presumably due to the stronger interlayer interaction and preferred growth in the [hk0] direction. The resulting Bi₂S₃ nanostructures exhibit broad absorption overlapping UV-visible-NIR regions and red-shifted absorption edges owing to the increased S/Bi molar ratio in Bi₂S₃ lattices. The Bi₂S₃ nanorods with a higher aspect ratio demonstrate an enhanced photocurrent response by virtue of the improved charge carrier mobility along the [001] direction. Different from previous synthetic methodologies, this work details a facile, effective, and environmentally-benign protocol for the synthesis of Bi₂S₃ nanomaterials in the aqueous medium without any organic reagents. Notably, the excellent and tailorable photoelectrochemical (PEC) performance endows these Bi₂S₃ nanostructures with vast potential in solar cell and photodetector applications.