Green synthesis of graphene for targeted recovery of silver from photovoltaic waste

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.