Sponge behaviors of functionalized few-walled carbon nanotubes

Abstract

Few-walled carbon nanotube (FWCNT) was functionalized with two different natures of functional groups in a mild poly(phosphoric acid) (PPA)/phosphorus pentoxide (P(2)O(5)). The one is less polar 4-ethylbenzoyl-functionalized FWCNT (EB-FWCNT) and the other is more polar 4-(aminomethyl)benzoyl-functionalized FWCNT (AB-FWCNT). The degrees of their functionalities were estimated by thermogravimetric analysis (TGA) and they had one functional group per average 17.7 and 25.3 carbon atoms, respectively. Contrary to expectation, the amount of bound water in the EB-FWCNT was 96.6 wt % and it is higher than that for AB-FWCNT (82.3 wt %). The unusual sponge behavior of EB-FWCNT is attributed to higher hydration energy as determined based on molecular simulation studies. The electrochemical behaviors are also greatly different between the EB- and AB-FWCNT.