Triboelectrification based on NiO-Mg magnetic nanocomposite: Synthesis, device fabrication, and energy harvesting performance

This study presents a systematic investigation on the NiO-Mg mechanochemical reduction process to form in-situ ferromagnetic NiO-Ni-MgO nanocomposites and utilize them as positive triboelectric layers in the fabricated triboelectric nanogenerator (TENG) devices for harvesting biomechanical energy in real-life applications. The structural and microstructural analyzes reveal a near-complete NiO reduction with three phases of face-centered-cubic structured nanocomposites. The magnetic study exhibits a robust ferromagnetic behavior. The correlative fractions of NiO and Ni phases eventually determine the overall structural and magnetic behavior of the nanocomposites. The coexisting ferromagnetic Ni and antiferromagnetic NiO phases determine the overall magnetic anisotropy induced ferromagnetism. The high temperature magnetization studies confirm the induced ferromagnetism caused by the higher Ni contents due to the NiO reduction. The nanocomposite, acting as a positive triboelectric layer, is successfully utilized for TENG device application, which helps to convert the accessible waste mechanical energy into suitable electrical energy. The fabricated TENG device with an area of 2 cm × 2 cm delivers the voltage of 35 V, an electrical current of 130 nA and a power density of 0.72 µW/cm² at 10⁸ Ω load resistance. The demonstration of biomechanical energy harvesting using the fabricated TENG devices provides ways to utilize the ferromagnetic nanocomposite as a positive triboelectric layer, suitable for several energy harvesting device applications in daily life.