Tailoring dopant concentrations in bismuth oxide nanoparticles for enhanced solar-driven photocatalytic wastewater remediation

Abstract

Pure and Mn-doped bismuth oxide (Bi₂O₃:Mn) nanoparticles were prepared by the low-temperature solution combustion method with urea as fuel, followed by calcination at 600 °C. The Bi₂O₃ was analyzed using X-ray diffraction method to find out the tetragonal phase of single Bi₂O₃ and no impurity, but UV–Vis spectroscopy indicates a hypsochromic (blue) shift in the absorption edge to 341 from 354 when doped with Mn. Bandgap decreased from 3.63 eV (Bi₂O₃) to 3.5 eV (Mn-doped), which means improved visible-light absorption through Mn-induced defect states. Application of simulated sunlight led to the photocatalytic degradation of methylene blue (MB), over which its Mn-doped Bi₂O₃ sample attained the MB removal of 96 % within 2 h, whereas undoped Bi₂O₃ (73 % degradation). This enhancement is due to the fact that Mn participates in the suppression of electron-hole recombination and the facilitation of charge separation, confirmed by decreased photoluminescence intensity and increased rate of reaction. Morphological studies (SEM) proved the uniformity of the nanoparticles, whilst the EDAX confirmed the incorporation of Mn. Such findings show that Mn doping is a good way of fine-tuning Bi₂O₃ to a structure that is more suitable for use in environmental remediation. The scalable synthesis technique and enhanced photocatalytic activity of Mn-doped Bi₂O₃ NPs make them a potential material for dye-contaminated wastewater remediation using natural sunlight, overcoming the key issues of sustainable pollution abatement and photocatalysis-driven chemical processes.