Abstract
The BiOCl and BiOBr oxyhalides were prepared by a simple coprecipitation route in a rich polyol medium at 100oC, where glycerol was used as solvent and mannitol as additive to increase the concentration of -OH groups in the reaction medium. The characterization of the samples was performed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), diffusion reflectance spectroscopy (DRS), and the specific surface area was revised by N2 adsorption-desorption isotherms following BET protocol. The photocatalytic activity of BiOCl and BiOBr was determined in the photooxidation of nitric oxide (NO) in air, obtaining values of nitric oxide conversion degree of 77 and 90%, respectively. The origin of the photocatalytic activity was associated to the higher concentration of -OH groups in the medium of reaction that induce a preferential orientation of the crystalline plane (110) in BiOCl, and in the formation of the heterojunction BiOBr/B24O31Br10 in BiOBr. The high selectivity in the reaction of NO photooxidation to innocuous NO3− ions was confirmed with values of 96% (BiOCl) and 93% (BiOBr). Electron paramagnetic resonance (EPR) measurements determined that the hydroxyl (•OH) and the superoxide (•O2¯) radicals are the highly oxygen reactive species that rule the NO oxidation photocatalyzed by BiOCl and BiOBr oxyhalides.