N-doped ZnO/graphene oxide: a photostable photocatalyst for improved mineralization and photodegradation of organic dye under visible light

This research work focused on the synthesis of visible light-active ZnO photocatalyst through modification with nitrogen and graphene oxide, followed by its application towards the degradation of brilliant smart green (BG) dye. The characterization of the synthesized photocatalysts was done using optical approaches such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), UV–vis absorption, and diffuse reflectance spectra (UV–vis DRS). N-ZnO-GO (NZGO-1, NZGO-2, and NZGO-3) composites show a higher photocatalytic activity in degrading BG dye in water compared to ZnO and N-ZnO nanoparticles. The composite NZGO-1 achieved 100% degradation and 80% mineralization of BG within 90 min of irradiation. The results also showed the degradation of BG using NZGO-1 occurs faster in basic medium (pH 9) compared to acidic medium. Photostability test of NZGO-1 analyzed after three cycles of exposure gave 94% degradation of BG which implies that the composite is also highly stable and can be recovered and reused. This study further highlighted that the modifications made on ZnO were positive by increasing its light absorption capability into the visible region and thus drastically improved its photocatalytic activities under visible light.