Exfoliation of Bismuth Dichalcogenide Crystals into Bi₂O₃ Nanosheets for the Photocatalysis of Hexavalent Chromium and Azo Compounds

The disintegration of crystals from bismuth dichalcogenides into Bi2O3 nanosheets stands out as a favorable methodology for the photocatalysis of azo dyes and hexavalent chromium [Cr (VI)] in wastewater treatment. In this investigation, the synthesis of Bi2O3 nanosheets via a simple sonication, utilizing N,N-dimethylformamide solvent, was explored. The Bi2O3 powder's EDX spectra indicate peaks for Bi, O, and C at 82.94, 10.18, and 6.89%, respectively, whereas the Tauc plot yields a band gap of 2.67 eV, and its XRD pattern exhibits three distinct peaks, (120), (200), and (121), suggesting monoclinic Bi2O3 formation. The obtained nanosheets exhibited significant surface area, rock-like shapes composed of multilayer sheets, single-crystalline attributes featuring a lattice spacing of 0.398 nm, and an optical band gap measuring 2.30 eV. Photocatalytic evaluations, employing methyl orange (MO) and Cr (VI), unveiled noteworthy efficiencies, reaching 78.5% within 240 min and 89.8% within 50 min under visible light, respectively. Both catalytic reactions conformed to pseudo-first-order kinetic , with kinetic constants (k) registering at 0.0023 and 0.044 min(-1) for MO and Cr (VI), respectively. The photocatalysis process involves the coordinated transport of electrons (e(-)) from the Bi2O3 nanosheets to the MO/Cr (VI) adsorbed on their surface, leading to effective wastewater treatment. These findings underscore the promise of exfoliated Bi2O3 nanosheets as an adept and efficient photocatalyst for MO/Cr (VI) contaminated wastewater treatment, featuring their notable contribution to advancing ecological water treatment methodologies.