Stabilization of the γ-Ag2WO4 metastable pure phase by coprecipitation method using polyvinylpyrrolidone as surfactant: Photocatalytic property

In this work, the effect of polyvinylpyrrolidone (PVP) concentration as a surfactant was studied in the stabilization of the metastable phase gamma-Ag2WO4 by the coprecipitation method at room temperature. The phases obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and spectroscopy in the ultraviolet-visible region (UV-Vis). The photocatalytic activity was estimated by varying the concentration of methylene blue dye. The diffractograms indicate that 0.3 g of PVP is ideal for obtaining the single phase of gamma-Ag2WO4, as larger or smaller amounts favor the appearance of beta-Ag2WO4 as a secondary phase while the absence of PVP formed the alpha-Ag2WO4 phase. UV-Vis spectroscopy showed that both phases have absorption in the ultraviolet region, where the gamma-Ag2WO4 phase has a higher absorption at shorter wavelengths. The micrographs indicate that the beta-Ag2WO4 morphology is formed by rods, while the gamma-Ag2WO4 is formed by octahedrons, both in micrometer scale and with well-defined morphology. The photocatalytic tests indicate that the gamma-Ag2WO4 phase has better photocatalytic activity compared to the beta-Ag2WO4 phase. The scavenger's methodology indicated that h(+) charges are the main mechanism in the photocatalysis of methylene blue dye.