Shape-tunable and sustainable carbon materials derived from nanocellulose and nanochitin: Carbonization, structures, and applications

Natural polysaccharides, cellulose, and chitin have gained exceptional popularity as sustainable precursors for biocarbons because of their abundance and carbonizability; however, their poor processability limits industrial expansion. Nanocellulose and nanochitin, which exist in the form of nanofibers and nanocrystals, respectively, have particularly attracted interest owing to their versatile ability to self-assemble into desired multidimensional structures while retaining intrinsic biomass features. This remarkable structural tunability enables these nanomaterials to be engineered through carbonization into diverse forms of biocarbons, such as dots, papers, films, and aerogels. This review aims to highlight recent progress in the fabrication of biocarbon materials derived from nanocellulose and nanochitin and their applications. Several carbonization processes and strategies for controlling the structural and functional properties of multidimensional biocarbons are discussed. Finally, advanced applications in terms of energy conversion and storage, environmental remediation, and sensing are summarized, together with known challenges for the practical utilization of carbon materials derived from nanocellulose and nanochitin.