Energy from discarded graphite-based pencils: Recycling the potential waste material for sensing application

Day-by-day piling up of various waste items is havoc for the environment. Particularly, non-degradable waste objects are deteriorating the environment at a fast pace. Energy from waste is a robust strategy that can mitigate the harsh consequences of daily-generated waste over the environment and the step of recycling waste for energy can reduce the energy consumption of daily life. Herein, we adopted a facile approach to harvest energy from discarded graphite lead pencils through triboelectric nanogenerator, employing top-to-bottom material synthesis technique the core of pencils is transformed into very fine powder material. For further utility of the material, several flexible composite films are fabricated through incorporating the material into polydimethylsiloxane (PDMS) matrix. Characterizing the as-fabricated composite films, maximum open-circuit voltage, short-circuit current and power density are achieved as 187 V, 28 μA and 1.2 mW/cm², respectively. 22 light-emitting diodes (LEDs) are illuminated by utilizing the output power of the film. The electrical output of B-grade lead-pencil graphite material (BLGM)/PDMS composite film is analyzed in parallel with pure-graphite-based composite film. Furthermore, several tribomaterials including aluminum (Al), perfluoroalkoxy (PFA), and polytetrafluoroethylene (PTFE) are also used as top-contacting material to analyze electrical signals sensing characteristics of the composite membrane. With comparable results to that of pure-graphite, the BLGM waste material can be beneficial for the economic fabrication of energy harnessing and sensing devices in a more sustainable and cost-effective way along with reducing environmental load.