NiO–Ti nanocomposites for contact electrification and energy harvesting: experimental and DFT+U studies

Abstract

Triboelectric nanogenerators (TENGs) have recently attracted extensive attention from academia and industry as a promising approach for energy harvesting. This work entails a detailed study of the NiO–Ti reduction process to synthesize NiO–Ni–TiO₂ nanocomposites, with structural, spectroscopic, and magnetic properties investigated to unveil the NiO reduction process to develop three-phase composites. Room temperature and high-temperature magnetic analyses revealed a robust ferromagnetic nature that was strongly correlated with the overall properties of nanocomposites. Density functional theory (DFT) analysis was employed to analyze the enhanced magnetic properties and charge accumulation. The synthesized nanocomposites showed a dielectric permittivity of ∼298 and a very low loss factor of ∼0.098 at 1 MHz. The surface polarity of 769 mV substantiated their successful utilization in enhancing the performance of an as-fabricated TENG, paving the way for the extension of new potential materials in the conventional triboelectric series. The electrical polarization and magnetization cumulatively contributed to improving the triboelectric performance. A 3D-printed eye-shaped vertical contact TENG was fabricated and delivered 60 V and 600 nA output, which could be enhanced by the use of multi-TENG units. The stable output for an extended period was further applied to charge the capacitors and could efficiently harvest energies from stomping and jumping motions.