Porous Functionalized Self-Standing Carbon Fiber Paper Electrodes for High-Performance Capacitive Energy Storage

A facile and cost-efficient approach to functionalize raw carbon fiber paper (CFP) used for a self-standing capacitive electrode has been proposed here. Benefiting from the improved' specific surface area and surface functional groups, the functionalized CFP (F-CFP) showed much enhanced capacitive performance, 3 orders of magnitude higher than that of the raw CFP. It delivered the areal capacitance of 1275 mF cm(-2) at 5 mA cm(-2) with a rather wide voltage window of 1.4 V (-0.4 to 1 V vs Ag/AgCI) in 0.5 M H2SO4. However, in a neutral 1 M Na2O4 aqueous solution, although the areal capacitance of 1115 mF cm(-2) at 3 mA cm(-2) is slightly smaller, the potential window is much:wider (2 V, -1 to 1 V vs Ag/AgCl), indicating a high overpotential of hydrogen evolution. The areal capacitance was still as high as 722 mF cm(-2) at a very fast charge-discharge current density of 50 mA cm(-2), and about 66% of the initial capacitance (at 3 mA cm(-2)) was remained in Na2SO4, indicating considerable, rate capability.