Читать книгу Carbon Nanofibers - Группа авторов - Страница 56

Another important application of CNMs is in the development of supercapacitor. Among the CNF obtained from seeds of various plants, it was found by Khairnar et al. (2008) that jackfruit seeds gave the highest capacitance of 92F/g [45]. It has been observed that though the CNM from rice straw has a higher surface area (140.15 m²/g) than that obtained from jackfruit seeds (114.02 m²/g), the capacitance obtained from the CNM of rice straw was lower (83F/g) than that of CNM from jackfruit seed. This apparent anomaly has been resolved by analyzing the SEM micrographs of both the CNMs, which show that CNMs from rice straw show channeltype structure while that from jackfruit seeds show porous but block-type structure (Figure 2.11). The cotton fiber-like structure of the CNM from jackfruit helps in forming the electrical double layer which is not so facile in the CNMs from rice straw.

This study established that for getting higher capacitance, in addition to large surface area CNF should also have a large number of pores in a plane parallel to the plane of the electrode for which the surface of CNM should be fluffy like a cotton ball.

Figure 2.11 CNF synthesized from seeds of Jackfruit and Rice straw by CVD method (Courtesy of Vilas Khairnar).