Carbon nanofiber/graphene composite paper for flexible supercapacitors with high volumetric capacitance

•Electrospun carbon nanofiber paper was obtained getting rid of traditional process.•Layer-by-layer stacking of nanofibers and graphene was achieved.•The composite paper displays much enhanced bulk density and conductivity•The composite paper has much higher volumetric capacitance than traditional paper.

Flexible carbon nanofiber/graphene composite paper (CGCP) was fabricated by vacuum-assisted filtration of aqueous suspension of phenolic nanofibers and graphene oxide, followed by one-step thermal treatment. CGCP displayed a carbon nanofiber/graphene sandwich structure, excellent flexibility, high bulk density (0.59 g cm−3) and excellent conductivity (7.6 S cm−1), and could be used as supercapacitor electrodes free of binder. Electrochemical measurement results revealed that CGCP had high volumetric capacitance (112 F cm−3), much higher than that of traditional electrospun carbon nanofiber paper (30 F cm−3).