Chiral Nematic Cellulose Nanocrystal/Germania and Carbon/Germania Composite Aerogels as Supercapacitor Materials

Abstract

The development of novel aerogel materials with chiral nematic ordered structures offers exciting pathways for the fabrication of multifunctional hybrid materials with enhanced functionality. Aerogels prepared from cellulose nanocrystals are especially interesting due to their unique structural properties. To promote applicability in energy storage materials, it is often necessary to incorporate metals and metal oxides into three-dimensional porous nanostructures. In this study, germania was incorporated into a chiral nematic cellulose nanocrystal aerogel using a sol–gel method. Interestingly, our approach does not disturb the order of the original chiral nematic CNC aerogels, providing hybrid aerogels with a large concentration of randomly distributed GeO2 nanoparticles and specific surface areas up to 705 m2 g–1. Carbonization of the composite material afforded a highly ordered material with no collapse during compression and good shape recovery after release. The combination of the electrochemical double layer capacitance provided by the carbonaceous skeleton and the pseudocapacitive contribution from the GeO2 nanoparticles resulted in materials with a maximum Cp of 113 F g–1 that exhibited good capacitance retention. To push the boundaries of safer energy storage devices based on renewable resources, we demonstrate the preparation of an all-cellulose solid-state symmetric supercapacitor.