Solid state preparation and photocatalytic activity of bismuth oxybromide nanoplates

A mechanochemical method was applied to prepare bismuth oxybromide (BiOBr) nanoplates using bismuth nitrate pentahydrate and potassium bromide for 15 (A15), 30 (A30) and 60 (A60) minutes. Scanning electron microscopy studies showed that all the products were comprised of nanoplates. Aggregated nanoplates along with microblocks were observed for A15 and A30 and the entire morphology was not homogenous. The morphology of A60 was uniform and consisted of thin and isolated nanoplates. Evaluation of the X-ray diffraction patterns showed that the purity and crystallinity of the products improved by increasing the milling time. The energy dispersive X-ray analysis confirmed the high purity of the products. Fourier transform infrared spectroscopy, photoluminescence spectroscopy and nitrogen adsorption-desorption analysis using the Brunauer-Emmett-Teller technique were also used to study the products. Diffuse reflectance spectroscopy studies clarified that all the samples were indirect band gap semiconductors with the band gap of 3.25 eV for A15 and the narrow band gap of 2.74 eV for A30 and A60. Photocatalytic studies revealed that A30 has the highest photocatalytic activity among the products. The effect of oxygen vacancies, surface defects, morphology and band gap of products on the photocatalytic or photosensitized degradation of rhodamine B (RhB) and pentachlorophenol (PCP) aqueous solutions were studied.