Improvement of the BiOI photocatalytic activity optimizing the solvothermal synthesis

BiOI nanostructured microspheres were obtained from the solvothermal synthesis route in the presence of ethylene glycol and KI as solvent and source of iodide, respectively. Optimal conditions for the synthesis were obtained by using multivariate analysis and choosing the photocatalytic oxidation rate constant 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 time and 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 was also carried out for the comparison of microstructure and its photocatalytic efficiency. The obtained BiOI nanostructures were characterized by scanning electron microscopy (SEM) attached with energy dispersive spectrometer (EDS), nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), Fourier transform infrared (FTIR) spectrometry, diffuse reflectance spectroscopy (DRS) and cyclic voltammetry (CV) analyses for their changes in morphological and structural behaviors. It was observed that the synthesis temperature of BiOI nanostructures strongly influenced the morphology, crystalline phase, surface area and electrochemical behavior, 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. [Display omitted] •Optimization of the synthesis for increase the photocatalytic activity.•BiOI microspheres were synthesized with high catalytic activity.•The structural characterization of the catalyst was carried out.•The synthesis temperature of BiOI strongly alter their catalytic activity.•Band gap and electrochemical properties were determined experimentally.