Cellulose is an abundant fibrous biopolymer and holds a leading position among renewable materials that can be derived from biomass feedstocks.¹ Separation of fibers results in nanoscale cellulose substances known as nanocellulose, which is classified into three main groups: cellulose nanocrystals, cellulose nanofibrils, and bacterial nanocellulose. However, cellulose nanocrystals (CNCs) are the mostly commonly used nanocellulose and are mainly produced through hydrolysis of the amorphous section of cellulose fibers. CNCs are rod-like crystalline fragments that generally feature a large surface area, which facilitates surface modifications of the cellulose due to the presence of hydroxyl groups on the surface of the nanofibrils. These hydroxyl groups with different reactivities can contribute to the formation of intra- and intermolecular hydrogen bonds, which in turn enable the creation of highly ordered, three-dimensional crystalline structures. These hydroxyl groups with different reactivities, different chemical modifications of CNCs have been attempted including sulfonation, oxidation, nucleophilic substitution, esterification, among others.² However, the main challenge for the chemical functionalization of CNCs is to conduct the process in such a way that it only changes the surface of CNCs and avoid any polymorphic conversion and other side reactions. Electrosynthesis provides economical and sustainable synthetic approaches for the functionalization of organic compounds and can be performed under lower potentials that lead to fewer side reactions and reaction selectivities can be fine-tuned. As such, the current work investigates the electrochemical modification of CNCs. Bulk electrolysis of reactions was operated under controlled current or controlled potential conditions using 3-electrode setup. Chronoamperometry and cyclic voltammetry techniques were employed to obtain quantitative information (e.g., turnover frequency) of electrochemical modification of CNCs and to investigate the reaction mechanism, respectively. Finally, the electrochemically functionalized CNCs were characterized using standard chemical and physical characterization protocols.³

(1) Calvino, C.; Macke, N.; Kato, R.; Rowan, S. J. Development, Processing and Applications of Bio-Sourced Cellulose Nanocrystal Composites. Prog. Polym. Sci. 2020, 103, 101221.

(2) Eyley, S.; Thielemans, W. Surface Modification of Cellulose Nanocrystals. Nanoscale 2014, 6 (14), 7764–7779.

(3) Foster, E. J.; Moon, R. J.; Agarwal, U. P.; Bortner, M. J.; Bras, J.; Camarero-Espinosa, S.; Chan, K. J.; Clift, M. J. D.; Cranston, E. D.; Eichhorn, S. J.; Fox, D. M.; Hamad, W. Y.; Heux, L.; Jean, B.; Korey, M.; Nieh, W.; Ong, K. J.; Reid, M. S.; Renneckar, S.; Roberts, R.; Shatkin, J. A.; Simonsen, J.; Stinson-Bagby, K.; Wanasekara, N.; Youngblood, J. Current Characterization Methods for Cellulose Nanomaterials. Chem. Soc. Rev. 2018, 47 (8)