Structural properties and electrochemical behavior of CNT‐TiO2 nanocrystal heterostructures

Abstract

AbstractDifferent methods of preparation of CNT‐TiO2 (anatase) heterostructures have been tested in order to obtain information on the relationship between the preparation method, resulting structure of the material and its electrochemical behavior during Li+ insertion. The most complete TiO2 coverage of individual non‐functionalized MWCNT was achieved in block co‐polymer (Pluronic P123) templated TiO2 thin films. This heterostructure has the highest specific capacity of Li+ insertion into TiO2 lattice to form Lix TiO2 (688 C/g, x = 0.57), however, this was accompanied by the worst reversibility (76%). On the contrary, electrodeposited TiO2 on SWCNT covered only bundles of nanotubes and its Li+ insertion capacity was 507 C/g (x = 0.42). However, the reversibility for all electrodeposited samples was almost complete and varied around 98%. Furthermore, Li+ insertion behavior studied by the cyclic voltammetry technique showed unambiguously the presence of minute amounts of monoclinic TiO2(B) in addition to anatase in samples from both synthesis methods. Thirdly, non‐functionalized MWCNT have been mixed by phase pure anatase nanocrystals of average size 30 nm made by hydrolysis of Ti‐butoxide in ethanol dispersion of CNT. Electrochemical Li+ insertion showed x = 0.54 (charge capacity of 652 C/g) with 85% reversibility. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)