Sandwich construction of chitosan/reduced graphene oxide composite as additive-free electrode material for high-performance supercapacitors.

The sandwich construction of chitosan (CS)/reduced graphene oxide (rGO) composite was synthesized through microwave-assisted hydrothermal method without further carbonization or activation process (CRG). CS homogeneous attached between the rGO slice sheet and improve the dispersion of CRG effectively, which can increase its specific surface area with hierarchical porous structure. Dehydration condensation occurred between CS and rGO, forming NHCO groups that can promote the wettability and conductivity of the composites. CRG exhibited improved degree of order and reduced graphitization defect, N-5 and OI groups were the dominant nitrogen and oxygen-containing groups. When used as additive-free electrode, CRG exhibited a high specific capacitance of 274 F g-1 at the current density of 0.5 A g-1 with good rate performance in a three-electrode system using 1 M H2SO4 electrolyte. Solid-state supercapacitor device was assembled with CRG electrode and lignin hydrogel electrolytes, high gravimetric energy densities of 8.4 Wh kg-1 at the power density of 50 W kg-1 was achieved.