Graphene quantum dot inlaid carbon nanofibers: Revealing the edge activity for ultrahigh rate pseudocapacitive energy storage

The edge sites of carbon show high electrochemical activity because of the unique electronic structure and functionalization. But revealing their energy storage ability and the underlying mechanism are still challenging. Herein, we prepare a novel edge-enriched carbon nanofiber fabric by exposing the embedded graphene quantum dots (GQDs) through partial hydrolysis of the electrospun GQDs/polyacrylonitrile fabric. The edges of inlaid GQDs are mainly terminated by various oxygen-bearing functional groups even after high temperature treatment, simultaneously contributing to abundant surface redox active sites and good electrolyte wettability. Further facilitated by the entire conductive networks, the edge sites are proved to show an ultrafast pseudocapacitive performance (200 F g−1 at 1 A g−1, 130 F g−1 at 100 A g−1) because of the robust electrochemical kinetics. Moreover, at an ultra-high mass loading of 25.5 mg cm−2 (thickness: 1.4 mm), the multilayer-folded fabric performs a remarkable areal capacitance (3.95 F cm−2 at 25.5 mA cm−2), outstanding rate performance (2.04 F cm−2 at 510 mA cm−2), and good cycle stability (98% capacitance retention after 10,000 times), demonstrating the great potential of edge structure design for high power devices.