Self-standing multiwalled carbon nanotubes/polypyrrole foams for aqueous symmetric supercapacitors

Developing lightweight structures employing materials with large capacitance is desirable to diversify the employment of supercapacitors in portable electronics. Here, hollow and flexible MWCNT/PPy foams were fabricated by electropolymerization to take advantage of the PPy properties and use it as a current collector and active material for supercapacitors. The effect of the formation time of the foams was evaluated using spectroscopic and electrochemical techniques, finding the best performance after 1200 s. Using a three-electrode arrangement, this foam reached a specific capacitance of up to 450 F g−1 (@ 0.5 A g−1) in 1 M H2SO4. As a result, a symmetric supercapacitor with performance comparable to those currently reported for polypyrrole-based materials was assembled. Moreover, the assembled device herein delivered specific energy of 12.5 W h kg−1 at a specific power of 200 W kg−1, and 9.1 W h kg 1 at 4000 W Kg−1. The main reason for the capacitance fading during the galvanostatic cycling was the increment of the electric series resistance, derived from the structural stress experienced by the PPy in the foam, as shown by the morphological characterization after prolonged cycling.