Liquid-Interfaces-Based Triboelectric Nanogenerator: An Emerging Power Generation Method from Liquid-Energy Nexus

As a state of matter, liquids exist in an extremely wide range, including water such as that in oceans and rivers, as well as various solutions, oils, liquid metals, etc. Due to the fluidity of liquids, the triboelectric effect based on them often shows unexpected results and can be used in complex environments. Herein, the latest research on working principles of the triboelectric effect at liquid-solid, liquid-liquid, and liquid-gas interfaces are reviewed. The factors affecting triboelectric charge generation and the output performance of liquid-interfaces-based TENGs (LI-TENG) in terms of material, environment, and structure are systematically discussed. Besides, to harvest the ubiquitously existing energy in various forms, studies about the hybridization of LI-TENG with other energy harvesters for syngeneic single-source and multisource energy harvesting are also reviewed. Moreover, the performances of LI-TENGs as energy harvesters and as novel sensors with various applications are reviewed. Finally, opportunities and challenges in the future development of LI-TENG are discussed.