RESUMO
A two-step simple and efficient ion-exchange chemical strategy is proposed to obtain nanostructured Bi2S3 electrodes of different surface morphologies from the Bi2O3. In the first step, nanoplates of the Bi2O3 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 Bi2O3 are transferred to the Bi2S3 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 Bi2S3 surpasses the Bi2O3 in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. The overpotential of 112-370 mV for the Bi2S3 network is much lower than that of the nanoplates of the Bi2O3 (275-543 mV), and walnuts (134-464 mV), nanowires (125-500 mV), and nanoflowers (194-520 mV) of the Bi2S3. The Bi2S3 network-type Bi2S3 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.
