Solvent-controlled morphology of bismuth sulfide for supercapacitor applications

In our study, we report a facile solvothermal method for the synthesis of Bi₂S₃ nanoparticles with unique morphologies using water and mixed solvent systems, such as ethylene glycol/water (1:1, v/v) and butyldiglycol/water (1:1, v/v). Altering the solution mixtures used in the solvothermal synthesis allowed the shape of the Bi₂S₃ nanoparticles to be controlled. The synthesis of Bi₂S₃ in water at 150 °C for 24 h led to the formation of sphere-like particles 100–300 nm in size. Very uniform spherical nanospheres with diameters from 50 to 90 nm formed when ethylene glycol/water mixture (1:1, v/v) was used as the solvent under the same solvothermal conditions. The butyldiglycol/water mixture promoted the formation of plate-shaped Bi₂S₃ nanoparticles composed of nanorods. The electrochemical properties of the Bi₂S₃ samples were determined in a three-electrode cell in 6 mol L⁻¹ KOH using cyclic voltammetry, galvanostatic charging/discharging and impedance spectroscopy. Among the synthesized materials, the Bi₂S₃ sample obtained in the butyldiglycol/water mixture exhibited a superior capacitive behavior with an outstanding capacitance of 550 F g⁻¹ (at 0.5 A g⁻¹), and great cycle stability, which was reflected by a capacitance retention of 87% after 500 charge/discharge cycles. These results demonstrate the high potential of Bi₂S₃ as an active electrode material for supercapacitors.