Fluorine-free coating-based droplet triboelectric nanogenerators for highly efficient energy harvesting

Abstract

As a new promising strategy for harvesting energy from low-frequency and irregular motions, triboelectric nanogenerators (TENGs) have attracted substantial attention in the realm of water droplet energy capture. However, conventional TENGs extensively employ fluorine-containing materials with surface micronanostructures, resulting in issues such as reduced lifespan, elevated costs for large area application, and risks associated with fluorine pollution. In this study, we substitute these fluorinated compounds with weather-resistant silicon-modified acrylic resin to prepare a new coating TENG with high-output performance for practical applications, achieving not only cost reduction and an extended lifespan of friction materials but also circumventing fluorine contamination. By utilizing water droplets as instantaneous switches, a droplet-based (D)-TENG with a communal electrode (CE) was developed. Then, by constructing a closed circuit by integrating a CE with a planar dual-electrode setup, fluorine-free TENGs could enhance the output performance and charge utilization efficiency. Compared with structures lacking CEs, the novel droplet TENG achieved a twentyfold increase in voltage, a fortyfold increase in current, and a tenfold enhancement in charge transfer. A peak output current of 1.5 mA and a peak output voltage of 200 V, combined with easily lit 180 commercial LEDs, were also accomplished. Furthermore, multiple D-TENGs with CE units could operate simultaneously, enabling extensive energy harvesting from water droplets. The D-TENG with a CE can be directly incorporated into metal devices requiring anti-corrosive and anti-fouling coatings, indicating a new method for the in situ utilization of marine equipment and facilities for collecting blue energy. By leveraging existing coating fabrication technologies, the proposed scheme holds the potential to propel the large-scale application of efficient water droplet energy harvesting systems.