Theoretical study on a graphene triboelectric nanogenerator with metal contacts

Charge transfer between graphene and a metal during contact electrification is theoretically investigated herein using a double graphene triboelectric nanogenerator (TENG) as a model system. This contact-separation process has been widely used in energy harvesting, where maximization of the tribo-charge density from an efficiency point of view is preferred. Herein, we introduce an analytical approach for calculating the Fermi energy shift with respect to the graphene conical point as a function of the graphene-metal distance with a change in the work function between the metal and graphene. This theoretical model for understanding the charge transfer between graphene and the metal can potentially be used to enhance device performance of two-dimensional energy harvesting systems.