Enhanced photocatalytic degradation of malachite green using manganese oxide doped graphene oxide/zinc oxide (GO-ZnO/Mn2O3) ternary composite under sunlight irradiation

In this work, photocatalytic degradation of malachite green (MG) dye using manganese oxide doped graphene oxide/zinc oxide (GO-ZnO/Mn2O3) ternary composite under sunlight irradiation is studied. GO-ZnO/Mn2O3 is a novel composite, which is non-toxic and of low cost prepared by the conventional solvothermal route. The synthesized composite was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), RAMAN spectra, photoluminescence (PL) spectroscopy, Diffuse reflectance spectroscopy (UV-Vis. DRS), and Barrett-Joyner-Halenda (BJH) pore size distribution. The GO-ZnO/Mn2O3 composite has a moderately large surface area of 75.35 m2/g and bandgap energy of 1.6 eV. Due to more pollutants adsorbed onto the photocatalyst surface and the reduction in bandgap energy, resulted less recombination rate and shifted the light absorption into the visible region to effectively utilize the sunlight and enhanced degradation of 98.75% is achieved within 30 min of sunlight irradiation for GO-ZnO/Mn2O3 composite. Using various scavengers, the main oxidizing radicals for the degradation of MG dye are identified as hydroxyl (•OH) and superoxide radical (•O2-). The synthesized composite is stable and reproducible as after five successful cycles, there was a small reduction in its degradation efficiency of 11.65%. Keywords: Graphene oxide; Photocatalyst; Malachite green; Bandgap; Scavengers.