Porous Carbon Composite Generated from Silk Fibroins and Graphene for Supercapacitors

Hierarchical porous heteroatom-doped carbon composites were developed by carbonization followed by KOH activation process, with natural silkworm cocoon and chemical exfoliated graphene sheets as starting materials. The introduction of graphene sheets offers more hierarchical micro/meso porosities, a low charge-transfer resistance, and a large BET surface area of ∼1281.8 m² g^-1, which are responsible for the fast charge/discharge kinetics and the high rate capability compared with those of single silk fibroins-derived carbon materials. The silk fiber provides a high level of heteroatom functionalities (∼2.54% N and ∼21.3% O), which are desirable for high faradaic pseudocapacitance. The as-prepared carbon composite exhibited a high specific capacitance of 290 F g^-1 with good rate capability and cycling stability. The symmetric supercapacitors yielded a high value of energy density of 12.9 W h kg^-1 at a power density of 95 W kg^-1 with a 1.45 V voltage range in 1 M KOH aqueous electrolytes.