Economic and green synthesis of carbon-based nanomaterials from agricultural wastes

Today, green chemistry in the synthesis of nanomaterials is attracting attention due to environmentalist approaches. The aim of this study was to prepare bio-graphene oxide (bio-GO) from agricultural waste such as rice husk, sunflower stalk and corn cob, and filter coffee waste, and to synthesise bio-graphene from these bio-GOs. Graphene oxide was synthesised in a single step, catalysed by ferrocene, at low temperature using a simple and fast method. Biomass waste is combusted under defined conditions in a muffle furnace with a ferrocene catalyst, which performs an electron transfer reaction for conversion to bio-GO. For optimisation, combustion temperature, combustion time and catalyst ratio studies were carried out, and the synthesised bio-GOs were characterised by X-ray diffraction (XRD) and Raman spectroscopy. In the optimisation studies, the combustion temperature, combustion time and catalyst/biomass ratio were 350 oC, 15 min and ½ for rice husk, respectively. For other samples, 400 oC, 15 min, and 1/5 was determined. As a result of ICP-OES analyses, the purity of Bio-GOs was found to be in the range of 95.55-98.99%. The bio-GOs obtained under optimum conditions were further characterized by energy dispersive X-ray spectrometry (SEM-EDS), elemental mapping, transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area and inductively coupled plasma-atomic emission spectroscopy (ICP-OES). Bio-graphene (bio-G) nanomaterials were synthesised from the prepared bio-GOs by chemical reduction method with hydrazine. The obtained bio-G nanomaterials were characterised by XRD, Raman, SEM-EDS, elemental mapping, TEM, BET surface area and, ICP-OES. The purity of the bio-Gs was determined to be in the range of 99,49 - 99,64 % according to the ICP-OES analysis results. The analysis results confirmed the formation of bio-GO and graphene layer structure and hexagonal framework. It can be concluded that the biomass waste used in the study is suitable as a sustainable alternative to graphite for the synthesis of bio-GO and graphene.