One-pot synthesis of three bismuth oxyhalides (BiOCl, BiOBr, BiOI) and their photocatalytic properties in three different exposure conditions

BiOCl, BiOBr, and BiOI have been synthesized by wet chemical route using bismuth nitrate (Bi(NO3)(3).5H(2)O) and potassium halides, KCl, KBr, and KI, using a mixture of de-ionized water and ethanol as the solvent. Synthesized samples were characterized by X-ray diffraction and high-resolution SEM to observe the crystalline phase and crystallite size. Effective surface areas of the synthesized samples were estimated by Brunauer-Emmett-Teller studies. Photoactive properties of these samples were studied under three types of light exposure conditions viz. UV light from mercury vapour lamp, natural sunlight, and visible radiations from a 100-W incandescent tungsten filament. Degradation of methyl orange (MO) in aqueous media was estimated spectrophotometerically in visible range from the area under the curve with a peak at 464 nm. Kinetic constant for degradation reaction was calculated assuming the pseudo-first-order degradation mechanism. It was revealed that all the three samples show excellent degradation of MO in UV exposure with BiOCl as the most efficient photocatalyst in these radiations. BiOBr shows highest photodegradation performance among the three samples under natural sunlight exposure. Overall performance of the three photocatalyst samples is much better than the popular titanium dioxide photocatalyst.