Theoretical and experimental insight into plasma-catalytic degradation of aqueous p-nitrophenol with graphene-ZnO nanoparticles

This paper aims to investigate plasma-catalytic degradation of p-nitrophenol (PNP) with graphene-ZnO nanoparticles based on theoretical and experimental perspects. The graphene-ZnO nanoparticles were firstly prepared by hydrothermal process, which were then systematically characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectrum, UV-Vis spectrophotometer, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption desorption analyzer. Combined with the analysis of Discrete Fourier Transform (DFT), the morphology, structure, specific surface area, absorption light range and electron transfer of the prepared catalyst are described in detail. The prepared graphene-ZnO nanocomposites displayed larger specific surface area and wider light absorption range. The charge could be transferred from ZnO to graphene. The catalytic degradation performace was further examined. Results indicated that degradation rate of PNP was enhanced from 68.5% to 80.2% with ZnO, which could futher improved to 97.6% with graphene (6%)-ZnO nanocomposites. The prepared samples exhibited good stability. Active species including OH, O-2(-), HO2, O-1(2), h(+) and e(-) played crucial role in PNP degradation. The degradation pathways were proposed based on DFT calculation and relevant literatures. Lastly, ECOSAR algorithm illustrated that the toxicity of PNP can be relieved after plasma-catalytic treatment.