Fabrication of alginate-based bio-tribopositive films via amine modification and metal ion coordination for high surface charge density

Developing triboelectric materials with high charge density is crucial for promoting large-scale applications of triboelectric nanogenerators (TENG). However, most of the reported works are only interested in tribonegative materials, while the tribopositive materials are rarely touched. Here, an efficient method was proposed to significantly boost the charge density of sodium alginate (SA)-based tribopositive films by simply grafting polyethyleneimine (PEI) and complexing copper ions. The prepared SA/PEI-Cu (SP-Cu) aerogel films not only have excellent flexibility and good environmental compatibility, but also high output triboelectric performance. Based on the aerogel film with a size of 5×5 cm², the fabricated TENG reveals a high output voltage of 3.5 kV, a maximum peak power density of 120 W m^-2, and a remarkable output charge density of 205 μC m^-2, which is nearly 8.2 times high that of pure SA and breaks the record for all reported biomass tribo-materials under environmental conditions. More than 9000 LEDs and a 24 W fluorescent lamp can be illuminated using this small-size TENG device. In particular, we successfully fabricated a rotating TENG device with a power management module (PMM) for harvesting wind energy to power a wireless environmental sensing system for smart agriculture. This work provides a novel strategy for developing high-performance bio-tribopositive materials, which may promote the practical applications of TENGs.