Boosted output performance of nanocellulose-based triboelectric nanogenerators via device engineering and surface functionalization.

Triboelectric nanogenerators (TENGs) provide promising potential to sustainably power modern portable electronic devices through harvesting mechanical energy from the environment. There is a need to further improve the sustainability credentials of TENGs by reducing the usage of non-renewable materials. Nanocellulose possessing outstanding properties, can partially replace non-renewable materials used in TENGs. Here, main sources and types of nanocellulose and methods of forming nanocellulose-based 2D/3D configurations used as triboelectric layers of TENGs are introduced. Cellulose has relatively weak tribopositivity and this review describes effective strategies of amplifying the output performance of TENGs possessing a nanocellulose-based tribopositive layer. Furthermore, efforts made to change the polarity of nanocellulose structures in order to use them as both positive and negative triboelectric layers are reviewed and their output performance is compared to that of all-synthetic polymer-based TENGs. Finally, requirements expected to be met in near future for development of commercial green nanocellulose-based TENGs are highlighted.