Ferrocenyl-functionalized carbon nanotubes with greatly improved surface reactivity for enhancing electrocapacitance

A series of ferrocenyl functionalized carbon nanotubes (CNT-Fc-n,n = 1,2,3) were synthesized and used as electrode materials for high performance supercapacitors. The results of galvanostatic charge-discharge measurement show that the specific capacitances of CNT-Fc-3 based electrode increase with the decrease of current densities. When the current density is 0.4 A g⁻¹, the maximum capacitance is 53.6 F g⁻¹. Ragone diagram, which shows that the symmetrical supercapacitor device based on CNT-Fc-3 electrode has typical symmetric capacitance characteristics. The energy density of CNT-Fc-3 based electrode under 0.1 kW kg⁻¹ is calculated to be 5.0 Wh kg⁻¹, and 3.0 Wh kg⁻¹ is kept in 0.5 kW kg⁻¹. In addition, the galvanostatic charge-discharge technique is used to test the stability of the cycle. The results show that the capacitance retention rate reaches 96.0% in 5000 cycles. In conclusion, ferrocenyl functionalized carbon nanotubes are ideal electrode materials for low cost and high efficiency electrochemical supercapacitors.