Novel magnetically separable Fe3O4–WSe2/NG photocatalysts: synthesis and photocatalytic performance under visible-light irradiation

Abstract

Visible light responsive Fe₃O₄–WSe₂/NG (nitrogen doped graphene oxide) heterojunction nanocomposites were synthesized by a hydrothermal synthesis route, in which Fe₃O₄ and WSe₂ particles were coated on the surface of NG. The samples were characterized by XRD, SEM, TEM, XPS, VSM, UV-vis DRS, TOC, and GC-MS techniques. The results showed that the photocatalytic activity of Fe₃O₄–WSe₂/NG photocatalysts under visible-light illumination was higher than that of WSe₂/NG owing to the narrow band gap energy and delayed electron–hole recombination, and Fe₃O₄ can be used in advanced oxidation processes (AOPs) to degrade organic pollutants at pH 3 and 3.0 mM H₂O₂. Moreover, the mass fraction of Fe₃O₄ had a great effect on the photocatalytic activity of Fe₃O₄–WSe₂/NG. Among the hybrid photocatalysts, 30 wt%Fe₃O₄–WSe₂/NG (30 wt% of Fe₃O₄) exhibited the highest photocatalytic activity with a rate constant of 0.05589 min⁻¹ for the degradation of MB in aqueous solution under visible light irradiation, and the removal efficiency reached 98.8% which was 1.6 times higher than that of WSe₂/NG. More importantly, the magnetic properties of 30 wt%Fe₃O₄–WSe₂/NG were analyzed and its reusability was also investigated after four successive runs by applying an external magnetic field.