Lignin-derived materials for triboelectric nanogenerators with emphasis on lignin multifunctionality

Sustainably sourced lignin, as natural polymer material rich in functional groups with electronegativity such as hydroxyl and carboxyl groups, is prone to gain or lose electrons to form triboelectric effects, thus providing enormous possibilities for the fabrication of triboelectric materials. Lignin has been extensively investigated in recent years for the preparation of triboelectric nanogenerators (TENG). However, there is still a lack of a well-defined classification references summarizing for these approaches. This review highlights the forefront research studies on TENG based on the lignin-derived materials with accented emphasis on lignin multifunctionality. A systematic description of the enhancement of TENG properties based on the lignin-derived materials by chemical modification, composite synergy and surface morphology modification methods is presented. Then, the current applications of TENG based on the lignin-derived materials, such as energy harvesting, medical monitoring and smart packaging, are summarized. Finally, challenges and strategies for the prospective development of TENG based on the lignin-derived materials are also reviewed. Therefore, this review will encourage the utilization of lignin-derived materials for the fabrication of eco-friendly TENG with promising applications in the field of energy conversion.