Influence of pH on the morphology and photocatalytic activity of CuO obtained by the sonochemical method using different surfactants

In this work, copper oxide II (CuO) was obtained using different surfactants (PVP, PEG and EDA), as well as without surfactant (WS), varying synthesis pH (8, 11 and 13). The powders were characterized by X-ray diffraction (XRD), field scanning electron microscopy (SEM), Brunauer-Emmett-Teller method (BET), UV-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), photoluminescent properties and their photocatalytic properties were measured against the methylene blue dye under UV radiation. XRD patterns showed that a pH increase from 8 to 13 favors CuO single phase formation, whereas Cu2(OH)3(NO3) secondary peaks appear at lower values. FTIR spectra confirmed the appearance of Cu2(OH)3(NO3) through the vibrations related to the hydroxide nitrate. The SEM images showed the variations in morphology obtained through the different surfactants and the medium pH, in which, the morphology presents a leaf appearance with a lower value (pH = 8), while increasing the pH to 13, changed the morphology into agglomerate flower-like nanoparticles. The BET results showed that the samples obtained without surfactant and with PEG at pH = 8 had the highest and lowest surface area, being 18.935 and 4.531 m2-1, respectively. The photocatalytic activity shows that the CuO powders that have a small amount of Cu2(OH)3(NO3) present better methylene blue dye degradability when illuminated by UV-Vis radiation