Macroporous carbon nanotube-carbon composite electrodes

Macroporous carbon nanotube-carbon composite electrodes (CNT-C) have been fabricated and characterized. CNT/polystyrene beads assembly was first prepared by electrophoretic co-deposition. Polypyrrole (PPy) was then polymerized electrochemically in the pore volume generated by the CNT assembly. After removal of the polystyrene template and pyrolysis of the conductive polymer between 650 and 950 °C, a macroporous composite material made of CNT and an amorphous carbon binder (quoted as C) was obtained. Increasing the amount of PPy allowed to improve the mechanical properties of the composite, as measured by the Young's modulus extending from 7 (CNT alone) to 663 GPa (CNT-C composite). CNT-C composite was characterized by Raman and X-ray photoelectron spectroscopies. Its surface area was dramatically enhanced, as evidenced by the increase in capacitance from 6 mF cm−2 to 199 mF cm−2 in the presence of the largest content of amorphous carbon. The influence of the amount of deposited carbon was discussed regarding the VO2+/VO2+ electrochemistry (i.e., the most critical redox couple in vanadium redox flow batteries). A 50 μm thick macroporous CNT-C composite gave rise to 5 times enhancement of the electrochemical response compared to a nonmacroporous CNT-layer).