High-yield of Lignin degradation under N-ZnO/Graphene Oxide compounds

Abstract The present work reports the results of the lignin molecule degradation studies using nitrogen-doped ZnO photocatalysts supported on graphene oxide. Three different nitrogen precursors were used to achieve the nitrogen doping in ZnO, namely urea, ethylenediamine, and thiourea, using a microwave-assisted hydrothermal method. Our purpose is to demonstrate that different nitrogen precursors give rise to different amounts of doping in ZnO, which in turn, favorably affects their photocatalytic behavior. The synthesized compounds were tested on the lignin degradation reaction, under visible (Vis) and ultraviolet (UV) energy irradiation. Structural and physicochemical properties of prepared samples were investigated to provide explanation of the photocatalytic behavior observed in samples. XPS analyses were developed to determine differences in nitrogen content, as well to determine the proportion of N-N or O-Z-N binding in samples. Remarkable structural and photocatalytic differences were found for every sample as effect of the nitrogen precursor. Photocatalytic activity tests revealed that the percentage of lignin degradation under UV irradiation was 80%; while using Vis energy the degradation value was 61%.