Conversion of the Bi2O3 to Bi2S3: An ion exchange strategy for tailoring the surface morphology with accrued energy storage performance

Abstract

A novel salt-mediated ion exchange strategy for changing the crystal structure and surface morphology of the bismuth oxide (Bi2O3) to bismuth sulfide (Bi2S3) with accrued energy storage performance has been investigated. Upright standing nanoplates of the Bi2O3 obtained at room-temperature (27 °C) on 3D nickel-foam (NiF) using successive ionic layer adsorption and reaction (SILAR) method after immersing it in thermal autoclaves in different sulphur salts at 120 °C for 8 h convert into nanocrystalline Bi2S3 having walnut, network, nanowire, and nanoflower-type surface morphologies. The electrochemical investigations carried out using electrochemical measurements reveal a noteworthy increase in the specific capacitance (SC) of the Bi2O3 nanoplates after forming Bi2S3 i.e. changing the phase and surface morphology. Compared to pristine Bi2O3 (221F g−1), the SC performances of network (1576 F g−1), walnut (358 F g−1), nanowire (296 F g−1), and nanoflower (836.6 F g−1)-type Bi2S3 electrode materials are higher in a 6.0 M KOH electrolyte solution. Furthermore, the network-type Bi2S3 of 22.02 m2 g−1 surface area exhibits remarkable stability, as evidenced by its 93 % capacitance retention even after 2000 redox cycles over other electrodes. The as-manufactured Bi2S3//nickel hydroxide (Ni(OH)2) asymmetric supercapacitor device, wherein the Bi2S3 acts as a negatrode and Ni (OH)2 positrode, delivers an outstanding energy density of 65.9 Wh/ kgat a power density of 988 W Kg−1. A twin cell assembly is envisaged for glowing the ‘CNED’ panel comprising approximately 42 LEDs with full luminosity. This idea of changing the crystal structure and surface morphology can be applied to other metal oxides to change their structures, surface areas, and morphologies for higher energy storage performance.