Improved Visible Light Photoactivity of CuBi₂O₄/CuO Heterojunctions for Photodegradation of Methylene Blue and Metronidazole

Abstract

Herein, a one-step solvothermal method was applied to produce CuBi2O4/CuO heterojunctions containing nanocolumns with small platelike nanoparticles homogeneously distributed over its surface. The photocatalytic activity of the heterojunctions was evaluated through the photodegradation of Methylene Blue (MB) dye and Metronidazole (MTZ) under simulated solar light and visible light irradiation, respectively. The heterojunction CuBi2O4/CuO-b showed an enhanced photocatalytic performance with 98% removal of MB (@2 sun simulated solar irradiation) and 36% removal of MTZ (@1 sun visible light) within 60 min of irradiation, compared to the results obtained with the pristine materials (CuO and CuBi2O4) or the other composite synthesized CuBi2O4/CuO-a. The apparent quantum efficiency for MB photocatalytic degradation using the optimized photocatalyst and 180 min of light irradiation is ∼2.1%, under the excitation wavelength of 540 nm. This enhanced photocatalytic performance is a result of an effective charge separation through a type-II heterojunction, indicating that photoinduced electrons transfer from CuBi2O4 to CuO nanoparticles and the photoholes migrate in the opposite direction. The main reactive species responsible for the photocatalytic degradation of the organic pollutant molecules were the photogenerated holes. Finally, the best photocatalysts were reused and presented good stability over three cycles, endorsing their promise as candidates for photocatalytic applications.