Search

The synthesis of free-standing graphene in a microwave plasma at ambient conditions is currently of great interest. The past works have relied on the usage of higher microwave powers to synthesize free-standing graphene which is not only costly but also an obstacle to the industrialization of the process. The aim of this work was to bring down the cost of the process by synthesizing graphene at a significantly lower microwave power, i.e. 250 W. The formation of graphene was confirmed through Raman spectrum and scanning electron microscopy, where the Raman spectrum showed the signature 2D peak of graphene, and the vertical orientation of the graphene was observed in the microscopic images. The application of graphene in oil-water separation is demonstrated based on its hydrophobic and oleophilic properties. The as-synthesized pristine graphene coated on a melamine sponge showed a mass absorption capacity (57 g/g) comparable to that of functionalized or composite graphene.

Atmospheric pressure microwave plasma can synthesize freestanding graphene in a few seconds at ambient conditions. Recent research has explored this method for the synthesis of graphene yet constrained by the utilization of toxic or non-renewable resources. This study aimed to substitute environmentally benign and sustainable precursors, synthesizing graphene from expired tangerine peel oil, an abundant natural source globally. The Raman spectrum of synthesized material showed a characteristic graphene-related 2D peak at microwave powers varied between 200 and 1000 W. The images of transmission electron microscopy revealed interstitial spacing of 0.34, which matched the value of X-ray diffraction calculated through Bragg's law. However, marginal variations in lattice spacing owing to the presence of oxygen functional groups were also observed. Additionally, the as-synthesized graphene deposited on a screen-printed electrode was used to selectively recover silver from spent photovoltaics. Our approach of creating a graphene-silver composite directly from waste material offers environmental benefits, resource utilization, waste reduction, and versatile applications in electrochemistry. [Display omitted] • Graphene with mild hydroxyl oxygen inclusions is synthesized from tangerine peel oil. • Microwave power significantly influences oxygen content attached to graphene. • Consistent interlayer spacing (0.34 nm) was confirmed through TEM and XRD. • Graphene exhibits a vertically oriented, curled-paper-like structure at all microwave powers. • Cyclic voltammetry analysis confirmed the recovery of silver from photovoltaic waste. [ABSTRACT FROM AUTHOR]