A review on applications of graphene in triboelectric nanogenerators

Abstract

Nanogenerators is the growing technology that facilitates self-powered systems, sensors, and flexible and portable electronics in the thriving era of internet of things (IoT). Since the first invention of the triboelectric nanogenerators (TENGs) in 2012, it has become one of the most important inventions in energy harvesting technologies. In this paper, a brief review on the recent progress of energy harvesting research based on TENGs technology is discussed. Basic working modes of the TENG are discussed in detail and the general procedure to synthesize, measure, and characterize a nanogenerator is presented in a direct structure. The triboelectric material choices are extremely important for TENGs since the triboelectric effects of the materials are fundamental for TENGs. The materials used as triboelectric layers are varied from polymers, metals, and inorganic materials with the commonly used materials are dielectric polymers such as PTFE, PVDF, PDMS, nylon, and Kapton. Recently, two-dimensional (2D) materials have been widely reported as candidate materials for TENGs. Graphene, the most attractive 2D materials exhibits an excellent electrical property, great flexibility, and a high surface-to-volume ratio. Owing to the very low thickness of the atomic unit, a stacking graphene structure can be also made to form a very thin and miniature TENGs device. The major applications of the graphene as active materials for TENGs as a sustainable energy harvester are presented, following which structural designs and materials optimization for output performance improvement of the graphene-based TENGs are summarized. Finally, the future directions and perspectives of the graphene-based TENGs are outlined. The graphene-based TENGs is not only a sustainable micro-power source for small devices, but also serves as a potential macro-scale generator of power from blue energy in the future.