Sulfur ion-exchange strategy to obtain Bi 2 S 3 nanostructures from Bi 2 O 3 for better water splitting performance.

A two-step simple and efficient ion-exchange chemical strategy is proposed to obtain nanostructured Bi 2 S 3 electrodes of different surface morphologies from the Bi 2 O 3 . In the first step, nanoplates of the Bi 2 O 3 are obtained on nickel-foam using successive ionic layer adsorption and reaction method at room-temperature (25 °C). In the second phase, as-obtained nanoplates of the Bi 2 O 3 are transferred to the Bi 2 S 3 using four autoclaves containing different sulfur precursor solutions at 120 °C for 8 h for phase change, structural conversion and surface morphological modification ( i.e. , walnuts, network-type, nanowires, and nanoflowers). Due to higher surface area and conductivity, lower charge transfer resistance, and reduced band gap caused by ionic and phase conversion, the Bi 2 S 3 surpasses the Bi 2 O 3 in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. The overpotential of 112-370 mV for the Bi 2 S 3 network is much lower than that of the nanoplates of the Bi 2 O 3 (275-543 mV), and walnuts (134-464 mV), nanowires (125-500 mV), and nanoflowers (194-520 mV) of the Bi 2 S 3 . The Bi 2 S 3 network-type Bi 2 S 3 electrode shows considerable chemical stability through cycling measurement, suggesting the importance of the present study in obtaining metal sulfides from metal oxide with better water splitting activities.