Solid-state synthesis, characterization, and optical properties of zinc oxide/graphene oxide nanocomposites for pollutant remediation

The band gap is crucial in evaluating semiconductor catalysts for photocatalysis. Zinc oxide nanoparticles (ZnONPs) are popular for renewable energy and environmental restoration but face challenges like a large band gap and rapid charge carrier recombination. Techniques like nanostructuring, doping, and using composite materials improve their efficiency. ZnONPs and ZnO/GO nanocomposites were synthesized using precipitation and solid-state methods. The ZnO/GO nanocomposite has a reduced bandgap (2.44 eV) compared to ZnONPs (3.31 eV), enhancing photocatalytic performance. Under visible light, ZnONPs reduced Cr(VI) by 67.9 %, while ZnO/GO achieved >99 % in 24 min. The degradation of phenol improved with increasing GO content; a 7 wt. % ZnO/GO dose achieved 99.2 % degradation without activators. These results highlight the role of hydroxyl radicals in pollutant breakdown, demonstrating the superior photocatalytic efficiency of ZnO/GO nanocomposites over ZnONPs.