Influence of pH variation on CuWO4, CuWO4/WO3 and CuWO4/CuO structures stabilization: study of the photocatalytic properties under sunlight

• Published in: Journal of materials science. Materials in electronics 2020-10, Vol.31 (20), p.18221-18233
• Main Authors: Andrade Neto, N. F., Oliveira, Y. G., Nascimento, J. H. O., Bomio, M. R. D., Motta, F. V.
• Format: Article
• Language: English
• Subjects: Catalytic activity; Characterization and Evaluation of Materials; Chemistry and Materials Science; Field emission microscopy; Field emission spectroscopy; Fourier transforms; Heterostructures; Hydroxyl radicals; Materials Science; Methylene blue; Morphology; Optical and Electronic Materials; Photocatalysis; Photodegradation; Photoelectrons; Polyvinylpyrrolidone; Scanning electron microscopy; Sonochemical reactions; Spectrum analysis; Stabilization; Sunlight; Tungsten oxides
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-04371-x

In this work, the reaction pH range (from 2 to 10) was used to study the stabilization of the CuWO 4 phase in the presence of polyvinylpyrrolidone surfactant synthesized by the sonochemical method. The powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), nitrogen adsorption and desorption using the Brunauer–Emmett–Teller methodology and ultraviolet–visible spectroscopy (UV–Vis). The photocatalytic activity was studied against MB dye under sunlight and CuWO 4 powders were tested at 5 reuse cycles. Diffractograms indicated that syntheses at pH 2 and 4 generate WO 3 /CuWO 4 heterostructures, while reaction pH at 8 and 10 generate CuO/CuWO 4 heterostructures and at pH 6 generates pure CuWO 4 . FE-SEM images indicated semispherical morphology for CuWO 4 , nanoplate morphology for CuO, and large particles without definite form for WO 3 powders. The scavenger's methodology indicates that hydroxyl radicals are the main responsible for the photodegradation of methylene blue in all samples. Also, it indicates that the formation of the WO 3 /CuWO 4 and CuO/CuWO 4 heterostructures increase the e − /h + pair recombination rate, reducing the photocatalytic activity in sunlight.