Preparation of BiOI microspheres in 2-propanol/ethylene glycol by microwave method with high visible-light photocatalytic activity

BiOI microspheres were synthesized by using mild conditions under microwave irradiation and applying short reaction times. The effect of the reaction medium in the final morphology of BiOI was revised modifying the relative concentrations of 2-propanol and ethylene glycol (EG) used as solvents. The as-prepared samples were characterized by X-ray powder diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, N 2 adsorption–desorption isotherms and photoluminescence measurements. The photocatalytic activity of BiOI was evaluated in the oxidation reaction of nitric oxide (NO) under visible-light irradiation. In particular, the samples with morphology of 3D flower-like microspheres prepared with EG showed the highest activity for NO removal (83%), maintaining its performance after several photocatalytic cycles. Besides the morphology of BiOI samples, the high photocatalytic activity was associated with the large surface area and the low rate of charge recombination observed in samples prepared with EG. The use of scavenger agents allowed to determine the predominant participation of holes (h + ), electrons (e − ) and superoxide ion ( · O 2 − ) in the reaction mechanism of the NO oxidation.