Multi-Responsive Supercapacitors from Chiral Nematic Cellulose Nanocrystal-Based Activated Carbon Aerogels

The development of long-lived electrochemical energy storage systems based on renewable materials is integral for the transition toward a more sustainable society. Supercapacitors have garnered considerable interest given their impressive cycling performance, low cost, and safety. Here, the first example of a chiral nematic activated carbon aerogel is shown. Specifically, supercapacitor materials are developed based on cellulose, a non-toxic and biodegradable material. The chiral nematic structure of cellulose nanocrystals (CNCs) is harnessed to obtain free-standing hierarchically ordered activated carbon aerogels. To impart multifunctionality, iron- and cobalt-oxide nanoparticles are incorporated within the CNC matrix. The hierarchical structure remains intact even at nanoparticle concentrations of approximate to 70 wt%. The aerogels are highly porous, with specific surface areas up to 820 m(2) g(-1). A maximum magnetization of 17.8 +/- 0.1 emu g(-1) with superparamagnetic behavior is obtained, providing a base for actuator applications. These materials are employed as symmetric supercapacitors; owing to the concomitant effect of the hierarchically arranged carbon skeleton and KOH activation, a maximum C-p of 294 F g(-1) with a capacitance retention of 93% after 2500 cycles at 50 mV s(-1) is achieved. The multifunctionality of the composite aerogels opens new possibilities for the use of biomass-derived materials in energy storage and sensing applications.