Bio-waste composites for cost-effective self-powered breathing patterns monitoring: An insight into energy harvesting and storage properties

The disposal of agricultural residues and solid biowaste from fruits and vegetables are detrimental to the environment as their decomposition creates toxic greenhouse gases. Herein, we demonstrate both energy harvesting and storage devices such as piezoelectric nanogenerator (PNG) and piezo-supercapacitor (PSC) by enforcing coconut husk (CH) as a filler into the polymer separator. To begin with, the CH powder was immobilized into the polyvinyl difluoride (PVDF) matrix to improve its piezoelectric performance. Remarkably, the poled PNG with a 7 wt% of CH powder/ PVDF composition delivers an output of voltage of 14 V, a current of 50 nA, and a power density of 0.35 μW/cm² at 100 MΩ. This output performance is significant enough not only to charge commercial capacitors but also to power electronic devices. Further, the PVDF/CH piezoelectric separator was sandwiched between graphene electrodes to develop a supercapacitor. The device achieved a maximum power density of 1.316 mW/cm² and an energy density of 76.33 mJ/cm², which is significantly higher than other graphene/PVDF-based devices. The practical feasibility of PNG is demonstrated as a breathing pattern monitor, which is an effective way to tackle the SARS-CoV-2 virus health conditions. Thus, the presented investigation paves the way towards a circular economy and sustainability.