The energy conversion performance of the triboelectric nanogenerator (TENG) is a function of triboelectric charges which depend on the intrinsic properties of materials to hold charges or the dielectric properties of triboelectric materials. In this work, Ag nanoparticles were synthesized and used to incorporate into natural rubber (NR) in order to enhance the dielectric constant for enhancing the electrical output of TENG. It was found that the size of Ag nanoparticles was reduced with the increasing CTAB concentration. Furthermore, the CTAB surfactant helped the dispersion of metallic Ag nanoparticles in the NR-insulating matrix, which promoted interfacial polarization that affected the dielectric properties of the NR composite. Ag nanoparticle-incorporated NR films exhibited an improved dielectric constant of up to almost 40% and an enhanced TENG performance that generated the highest power density of 262.4 mW/m2.

Because of a lack of electron donor/acceptor groups, TENGs fabricated from natural rubber (NR) usually produce low electrical outputs. The present study demonstrated that the electrical outputs of NR TENGs could be enhanced by the presence of lignin. Lignin with an unanticipated triboelectric property became a triboelectric active material upon subjecting to ultrasound in a basic solution. Physically, lignin irradiated with ultrasound would undergo particle size reduction from tens of micrometers down to a micrometer in diameter, leading to an increase of interfacial area for triboelectric charge generation. Accompanying the size reduction was a partial depolymerization of lignin arising from the chemical bond cleavage via the nucleophilic attack of hydroxide ions. This event caused an increase of polar functional groups on lignin that benefited the charge generation and transfer. TENGs from the NR/lignin composite generated a power output density up to 500% larger than that produced from NR TENG. However, NR/lignin TENGs suffered from the aggregation of lignin leading to a compromise of the electrical outputs. Therefore, NR was grafted with polyacrylamide (NR-g-PAM) to inhibit lignin aggregation as well as to promote an even distribution of lignin particles in the NR matrix. As a result, NR-g-PAM/lignin TENG was capable of enhancing the power output density to 260 and 1300% compared with that of NR/lignin and NR TENGs, respectively.