Triboelectric Enhancement in Droplet-Based Electricity Generators via Nafion-Functionalized Cellulose Nanocrystals

Liquid-solid triboelectric nanogenerators (L-S TENGs) enable the harvesting of electrical energy through interactions between water droplets and solid surfaces. In particular, droplet-based electricity generators (DEGs) utilize the impact and spreading behavior of water droplets on dielectric materials to convert mechanical energy into electricity. Most existing DEG systems rely on synthetic polymers because of their excellent triboelectric characteristics. In this study, a Nafion-functionalized cellulose nanocrystal (Nf-CNCs) film is introduced to enhance the triboelectric performance in a DEG configuration. Cellulose nanocrystals, owing to their high dielectric constant, pronounced crystallinity, and ordered molecular structure, represent an ideal sustainable material for triboelectric energy conversion. The fabricated DEG device demonstrated stable electrical performance over a broad range of droplet kinetic conditions. It achieves a peak power density of approximately 310  mW/m². Parametric investigations reveal the effects of droplet diameter, impact velocity, and impingement position on device performance. Furthermore, long-term durability tests demonstrate stable open-circuit voltage and current, confirming the device's robustness. The DEG device delivers sufficient power to directly activate low-power electronics such as LEDs, underscoring its potential as an eco-friendly and scalable platform for ambient mechanical energy harvesting from water droplets.