Fabrication of 3D array ferromagnetic photocatalyst with enhanced visible-light photocatalytic activity

Abstract

A photocatalyst consisting of ZnFe2O4/Ag nanocomposite particles deposited on a 3D columnar array Si substrate was prepared. The photocatalytic performance under visible light of the 3D columnar array Si/ZnFe2O4/Ag photocatalyst was compared with that of planar Si/ZnFe2O4/Ag and planar Si/ZnFe2O4. The effect of an applied magnetic field was also investigated. The interfacial contact in Si/ZnFe2O4/Ag increases carrier transfer, whereas the 3D columnar array substrate provides more photocatalytic reaction sites, increasing the utilization of photogenerated electrons and holes. The photocurrent density of 3D columnar array Si/ZnFe2O4/Ag (0.621 mA/cm2) was higher than that of planar Si/ZnFe2O4/Ag (0.09 mA/cm2). Additionally, applying a 1000 Oe magnetic field to 3D columnar array Si/ZnFe2O4/Ag resulted in a high photocurrent of 1.315 mA/cm2. In addition, the 3D columnar array Si/ZnFe2O4/Ag photocatalyst can also be effectively used for photodegradation of Methyl orange, and exhibits high stability. At the same time, the external magnetic field can further improve its photodegradation efficiency. The I–V experiments demonstrated that the Si/ZnFe2O4/Ag has a more negative magnetoresistance than Si/ZnFe2O4. Thus, the spin moments of the photocatalyst align parallel to each other under a magnetic field, allowing more photogenerated carriers to transfer through the interface and thus improving the photocatalytic performance. These results provide a relatively simple method for the development of efficient photocatalysts and improvement of existing photocatalysts.