Ammonia-assisted thermal activation of graphene-embellished biological fiber for flexible supercapacitors.

Abstract Herein, we have demonstrated a scalable synthesis route to develop nitrogen-doped graphene embellished carbonized cottons (NGCs) via ammonia-assistant thermal activation processes combining with freeze-drying technique. It is found that the nitrogen-doped graphene (NG) nanosheets are well dispersed and cross-linked with the carbonized cotton skeleton fibers. The assistance of ammonia in thermal treatments can not only benefit the carbonization of the cotton and the reduction of the graphene oxide, but also make the nitrogen elements dope into the whole carbon composites. Due to the synergistic effect between the doped N functional groups and the highly conductive cross-linked networks, the NGCs electrodes exhibit a high capacitance (291 F g−1 at 1.0 A g−1) and a high cycle stability (almost no attenuation after 10,000 cycles). Furthermore, a type of lightweight and flexible symmetric supercapacitors was assembled, delivering a high energy density (5 W h kg−1 at 0.2 A g−1) and an excellent bending stability, which demonstrates its potential application in wearable energy storage devices. Graphical abstract Image 1 Highlights • A facile process was developed for NG immobilized on N-doped carbonized cotton. • NH 3 activation achieved cotton carbonization, GO reduction, and overall N doping. • The composite demonstrates an 11% increase in capacitance after 10,000 cycles. • A fully foldable supercapacitor delivers high energy density of 5 Wh/kg at 0.2 A/g. [ABSTRACT FROM AUTHOR]