ZnO-graphene nanohybrids for photocatalytic degradation of methylene blue dye

Abstract

Addressing the escalating global crisis of water contamination by synthetic dyes, necessitates the advancement of efficient and sustainable photocatalytic materials. In this study, we report a simple and direct fabrication of ZnOgraphene (ZG) nanohybrids photocatalyst via a scalable photothermal approach, yielding a hierarchical architecture comprising vertically aligned ZnO nanoparticles uniformly anchored onto graphene layers. The engineered configuration imparts a high surface area, enhanced interfacial contact, and improved charge carrier dynamics, critical for efficient photocatalysis. Comprehensive microstructural and spectroscopic analyses confirm the successful integration of ZnO with graphene, revealing an improved optical bandgap of similar to 1.92 eV, which extends the light absorption spectrum into the visible region. Photocatalytic assessments reveal that the ZG nanohybrids achieve 93 % degradation of 5 ppm methylene blue (MB) under UV-visible light within 130 min, significantly outperforming pristine graphene. This increased activity is attributed to efficient electron-hole separation, broadened photoresponse, and the generation of reactive oxygen species, particularly hydroxyl radicals (center dot OH), as supported by photoluminescence and radical scavenger studies. The graphene framework facilitates rapid charge transport, while the ZnO nanoparticles contribute abundant active sites and enhance the surface area. Furthermore, the ZG photocatalyst demonstrates excellent cycling stability, maintaining performance over five consecutive degradation cycles with minimal loss. This work highlights the potential of ZG nanohybrids as a robust, cost-effective, and scalable photocatalytic platform for advanced environmental remediation, offering promising avenues for future wastewater treatment technologies.