Binder-free hierarchical porous N-doped graphene directly anchored on carbon fiber cloth for high-performance electrochemical energy storage

A binder-free hierarchical porous N-doped graphene directly anchored on carbon fiber cloth was manufactured by a simple and practical two-step process, in which polyindole/graphene oxide (PIn/GO) composites were prepared by in-situ oxidation polymerization of indole on the surface of GO, and then PIn/GO composites coated on the surface of carbon fiber cloth was activated with KOH at 700 °C. By adjusting the contents of PIn, GO, and KOH, a hierarchical porous P7G-K-2 electrode with N content (4.98 at.%) was obtained and showed lager specific surface area and low interfacial contact resistance. The electrochemical evaluation showed that the P7G-K-2 electrode had a maximum specific capacitance of 451 F g−1 at 1 A g−1 and excellent rate performance. Moreover, a simple supercapacitor consisting of two symmetrical P7G-K-2 electrodes, P7G-K-2//P7G-K-2, was assembled, the specific energy of 21.8 Wh kg−1 can be obtained at the specific power of 75 W kg−1, and it had excellent long-term cycle stability (maintaining 92% initial specific capacitance after 10,000 cycles). The excellent performance indicates that the P7G-K-2 is a promising candidate for supercapacitor electrode materials with high energy output. And this work provides a strategy to fabricate supercapacitors electrode with high specific power and specific energy.