Transformation of Nanostructures Cu₂O to Cu₃Se₂ through Different Routes and the Effect on Photocatalytic Properties

In this work, copper selenide (Cu₃Se₂ umangite phase) was synthesized by two routes, using a chemical reaction and the hydrothermal method to obtain CuSe-A and CuSe-H, respectively. The synthesis of Cu₃Se₂ consisted of a three-step process: in the first step, copper(I) oxide hexapods (Cu₂O) were obtained as the copper reservoir; in the second step, selenium ions were obtained from the reduction of selenium powder; and in the third step involves mixing two precursors following the two synthesis routes mentioned before. Analysis of X-ray diffraction and X-ray photoelectron spectroscopy showed the formation of the Cu₃Se₂ phase by both synthesis routes. On the other hand, using the scanning electron microscopy (SEM) technique, it is observed that the Cu₃Se₂ sample (CuSe-A) is obtained by exchanging in solution with agitation and that the copper selenium phase grows only on the surface of the hexapods. Meanwhile, the hydrothermal route promotes a total conversion of copper(I) oxide hexapods to the copper selenide phase (CuSe-H). The resulting materials were tested as photocatalytic materials to remove methylene blue dye in water under sunlight irradiation. Cu₃Se₂ (CuSe-H) obtained by the hydrothermal route exhibited a higher efficiency of photodegradation of dye, reaching a removal percentage of 92% after 4 h under sunlight.