Construction of multifunctional cellulose nanofibers/reduced graphene oxide carbon aerogels by bidirectional freezing for supercapacitor electrodes and strain sensors

Carbon aerogel is an excellent conductive porous carbon material, but suffers from poor mechanical properties and fatigue resistance, which greatly limits its application as a flexible electronic device. Herein, the cellulose nanofibers/reduced graphene oxide carbon aerogel (BCRCA) with a unique layered structure was prepared by bidirectional freezing technique and thermal annealing. BCRCA's layered structure gives it ultra-low density (3.25 mg/cm3), high specific surface area (159.53 m2/g) and good compression properties (91.3 % stress retention, 100 cycles at 50 % compression). In addition, BCRCA for supercapacitor electrodes has a high specific capacity of 104.3 F g-1 at 0.1 A g-1 and a high capacitance retention rate of 93 % at 5000 cycles at 2 A g-1. Notably, the BCRCA assembled into a wearable strain sensor exhibits a stable current signal for real-time monitoring of finger, wrist, and elbow joint movements. These advantages make BCRCA have broad applica-tion prospects in the field of electronic energy storage devices and wearable strain sensors.