Etched Carbon Fiber/Polyaniline Composite with p–n Heterojunction for High-Energy Electrochemical Supercapacitor

Abstract

The etched carbon fiber/polyaniline (ECF/PANI) composite material with p–n heterojunction was successfully prepared via in situ chemical oxidation polymerization. The experimental results revealed the growth of uniform orderly PANI coating layer with slight agglomeration and generation of p–n heterojunction in ECF/PANI composite. The specific capacitance of ECF/PANI-3 composite with mass ratio 1:2 reached an optimized maximum of 525.1 F g−1 at current density 0.1 A g−1 while still maintaining as high as 374.8 F g−1 at 5 A g−1, and 75.6% capacitance retention ratio could be achieved on ECF/PANI-3 at 1 A g−1 after 5000 cycles. Meantime, the redox reaction kinetics were controlled by the diffusion process and the electron transfer resistance of ECF/PANI-3 exhibited as low as 0.25 Ω cm2. Such excellent performances stem from the synergetic effect of the high conductivity of ECF and loose porous morphology of the PANI layer. Most importantly, the enhancement of electrochemical properties for ECF/PANI is substantially ascribed to the p–n heterojunction with low flat band potential, which is favorable to the electron transition from valence to conduction-band and provides higher carrier concentration and more driving force for the charge transmission, electrons mobility, and conductivity of ECF/PANI composite.