Polypyrrole@CNT@PU Conductive Sponge-Based Triboelectric Nanogenerators for Human Motion Monitoring and Self-Powered Ammonia Sensing

Elastic sponges are ideal materials for triboelectric nanogenerators (TENGs) to harvest irregular and random mechanical energy from the environment. However, the conductive design of the elastic materials in TENGs often limits its applications. In this work, we have demonstrated that an elastic conductive sponge can be used as the triboelectric layer and electrode for TENGs. Such an elastic conductive sponge is prepared by a simple way of adsorbing multiwalled carbon nanotubes and monomers of pyrrole to grow conductive polypyrroles on the surface of an elastic polyurethane (PU) sponge. Due to the porous structure of the PU sponge and the conductive multiwalled carbon nanotubes (MWCNTs), PPy on the surface of PU could provide a large contact area to improve the output performance of TENGs, and the conductive sponge-based TENG could generate an output of open-circuit voltage of 110 V or a short-circuit current of 12 μA, respectively. The good flexibility of the conductive PU sponge makes the TENG harvest the kinetic energy of disordered motion with different amplitudes, allowing for human motion monitoring. Furthermore, the porous structure of PU and the synergistic effects of PPy and MWCNTs enable the conductive sponge to sense NH3 as a self-powered NH3 sensor. This work offers a simple way to construct a flexible TENG system for random mechanical energy harvesting, human motion monitoring, and self-powered NH3 sensing.