gC3N4 decorated with ZnO:Mn rods for enhanced photocatalytic performance

Abstract

In the present research, ZnO:Mn rods obtained from recycled anodic paste of spent Zn–MnO₂ alkaline batteries were immobilized on the surface of graphitic carbon nitride (gC₃N₄) and tested as photocatalysts for degradation of RhB under visible light irradiation. The effect of the ratio between the two components of the composite materials on the RhB removal rate was investigated. The achievement of the composite material was proved by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), Fourier transform infrared spectroscopy (FTIR), and electron paramagnetic resonance (EPR). The Brunauer–Emmett–Teller (BET) analysis shows that increasing the ZnO:Mn content decreases the surface area of the composite samples. The composite samples show enhanced photocatalytic activity under visible irradiation compared with ZnO:Mn. The sample with the ratio 1–0.1 between gC₃N₄ and ZnO:Mn has the highest removal rate of 93% with a kinetic constant of 12.1 × 10⁻³ min⁻¹ almost six times higher than that corresponding to the ZnO:Mn sample (2.3 × 10⁻³ min⁻¹). The superoxide radicals are the main reactive oxygen species (ROS) involved in the dye degradation, as evidence by EPR spectroscopy coupled with the spin trapping technique. The coupling between gC₃N₄ and ZnO:Mn suppresses the electron–hole pair recombination, improving the photocatalytic performance. Moreover, the sample has good stability, and the removal rate was slightly modified after 5 consecutive reaction cycles. Also, the samples have a potential inhibitory antibacterial effect.