Graphene/silk fibroin based carbon nanocomposites for high performance supercapacitors

The graphene and silk fibroin based carbon (GCN-S) material is prepared by the carbonization of reduced graphene oxide (RGO) and silk fibroin (SF) nanofibrils composite in the presence of KOH. The good combination of RGO and SF nanofibrils, which turns out to be micro/meso-carbon after activation, endows the obtained GCN-S materials with high specific surface area, multi-porous structure, good electrical conductivity, and consequently excellent electrochemical performance. For example, the GCN-S-0.5 synthesized at 0.5 : 1 ratio of KOH and RGO/SF nanofibrils suspension shows a high BET specific surface area of 3.2 x 10(3) m(2) g(-1), and the specific capacitance is 256 F g(-1) at a current density of 0.5 A g(-1). Moreover, it still delivers a specific capacitance of 188 F g(-1) even at a current density as high as 50 A g(-1), corresponding to a capacitance retention rate of 73.4%. After a charge-discharge rate of 5 A g(-1) for 10 000 cycles, the GCN-S-0.5 exhibits remarkable electrochemical stability with the capacitance retention ratio of 96.3%. Furthermore, the GCN-S-0.5 based supercapacitor achieves high energy density up to 14.4 Wh kg(-1) at an ultrahigh power density of 40 000 W kg(-1). The results shown in this work indicate that our GCN-S material is a promising candidate for manufacturing supercapacitors with both a high performance and relatively low cost.