Ferromagnetic-assisted Maxwell's displacement current based on iron/polymer composite for improving the triboelectric nanogenerator output

Triboelectric nanogenerator (TENG) based on Maxwell's displacement current as the driving force has broad applications in energy harvesting and self-powered sensors. However, the effect of doped ferromagnetic materials with bearing an external magnetic field on TENG's displacement current has not been clearly revealed. Herein, a ferromagnetic-assisted Maxwell's displacement current is proposed for improving TENG output based on polymer/iron composite film (PICF). Based on Maxwell's equations, the magnetizing current of the ferromagnetic medium coupled with the displacement current is investigated theoretically for boosting TENG output and verified simulationally and experimentally. Comparing TENG output with the magnetization method of PICF, the initial magnetization significantly determines the coupling mechanism between magnetizing current and displacement current. Moreover, the strength and direction of an external magnetic field further reveal the mechanism impacting the initial magnetization on TENG's displacement current. A short-circuit current density of 27 mA/m² and instantaneous power density of 2 W/m² are achieved by the champion TENG, which are 800% and 8200% higher than those of pristine polymer. Finally, a distributed TENG array is developed for efficiently harvesting distributed energy to demonstrate the application potential of the improved TENG in self-powered systems. This work elaborates the coupling mechanism of the magnetizing current with TENG's displacement current, which provides general guidance for investigating efficient energy harvester toward self-powered sensors, wearable electronics and flexible electromagnetic shielding devices.