Improvement of the BiOI photocatalytic activity optimizing the solvothermal synthesis

Abstract

BiOI nanostructured microspheres were obtained from the solvothermal synthesis route in the presenceof ethylene glycol and KI as solvent and source of iodide, respectively. Optimal conditions for the synthesiswere obtained by using multivariate analysis and choosing the photocatalytic oxidation rateconstant of 3,4,5-trihydroxybenzoic acid (gallic acid) as response factor under simulated solar radiation.Response surface methodology (RSM) was used to determine the optimum values of the reaction timeand temperature which were 18 h and 126 C, respectively, to obtain the most active catalyst. In addition,BiOI synthesis using ionic liquid 1-butyl-3-methylimidazolium iodide ([bmim]I) as iodide source wasalso carried out for the comparison of microstructure and its photocatalytic efficiency.The obtained BiOI nanostructures were characterized by scanning electron microscopy (SEM) attachedwith energy dispersive spectrometer (EDS), nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectronspectroscopy (XPS), thermogravimetry (TG), Fourier transform infrared (FTIR) spectrometry,diffuse reflectance spectroscopy (DRS) and cyclic voltammetry (CV) analyses for their changes inmorphological and structural behaviors. It was observed that the synthesis temperature of BiOI nanostructuresstrongly influenced the morphology, crystalline phase, surface area and electrochemicalbehavior, and thus affecting the photocatalytic efficiency. The higher photocatalytic removal of gallic acid(60%) was reached within 30 min of irradiation with UV-A on microspheres obtained with ionic liquid.The (1 1 0) crystal phase of BiOI influenced the photocatalytic efficiency.