Environmentally friendly natural materials for triboelectric nanogenerators: a review

Significant progress has been made in using triboelectric nanogenerators (TENGs) to harvest sustainable energy from wind, waves, human activities, and water droplets. Natural materials, which are non-synthetic and have the advantages of being low-cost, environmentally friendly, biodegradable, and partially biocompatible, can be used to prepare green TENGs. In this review, the latest advances made in natural-materials-based TENGs are summarized. The triboelectric mechanisms and properties of natural-materials-based TENGs derived from animals, plants, humans, microorganisms, and minerals are discussed. The output performance, features, and applications of the natural materials used to construct the tribopositive and tribonegative layers of TENGs are discussed. Moreover, the triboelectric sequence of the natural materials is summarized to compare their ability to gain or lose charge in the process of friction. Finally, the challenges facing natural-materials-based TENGs, such as complex processing, short service life, lack of stability, few tribonegative materials, and low power density, are listed. It is thus anticipated that this review will encourage the use of natural materials to manufacture eco-friendly TENGs that have broad application prospects in the field of energy conversion.