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

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.