Novel concept for synthesizing carbon nano-onion, graphene layers, and graphene nano-ribbons from polypropylene waste over Fe2O3 nanoparticles

Abstract In order to optimize the manufacturing of polypropylene-derived few-layer graphene, an innovative utilization of non-supported iron oxide nanoparticles generated under various fuel environment conditions was studied. Three distinct fuel combustion environment circumstances (fusion, fuel shortage, and fuel excess) produced a variety of Fe 2 O 3 nanoparticles for cost-effective and green graphene deposition. XRD, H 2 -TPR, Raman, and TGA measurements were used to characterize both new and spent catalysts. Remarkably, the microstructure of the generated Fe 2 O 3 nanoparticles could be controlled by the citric acid/iron nitrate ratio, ranging from spheroids (Fe 2 O 3 (0)) to sheets (Fe 2 O 3 (0.5-0.75)) and a hybrid microstructure that consists of sheets, spheroids, and interconnected strips (Fe 2 O 3 (1-2)). According to fuel situation (citric acid/iron nitrate ratio, Fe 2 O 3 (0-2)), various graphitization level and yields of graphene derivatives including sheets, ribbons, and onions have been developed. With the ideal fuel/oxidant ratio ( ɸ = 1), the Fe 2 O 3 (0.75) catalyst demonstrated the best catalytic activity to deposit the largest yield of highly graphitized few graphene layers (280%). Lean and rich fuel conditions (1 > ɸ > 1) have detrimental effects on the amount and quality of graphene deposition. It is interesting to note that in addition to graphene sheets, an excess of citric acid caused the production of metallic cores, hollow, and merged carbon nano-onions, and graphene nano-ribbons. It was suggested that carbon nano-onions be converted into graphene nano-ribbons and semi-onion shell-like graphene layers. Graphical abstract