Electrochemistry on Carbon Nanotubes Highlights 2000 Charge Transfer at Carbon Nanotubes

had focussed on practical issues of hydrogen storage [1], Li batteries [2] and supercapacitors [3]. Owing to their unique electronic structure, the singlewalled carbon nanotubes (SWCNT) show characteristic Raman and VisNIR spectra. They are understood in terms of resonance enhancement and optical band-gap excitation in onedimensional conductor with Van Hove singularities in the electronic density of states [4]. There are significant spectral changes, if the SWCNT are subjected to redox processes. While the chemical redox modifications of SWCNT were studied in detail by Raman and Vis-NIR spectroscopy, the first corresponding work on electrochemical charging of SWCNT was given by the present authors [5]. The cited work [5] reported on in-situ Raman and Vis-NIR spectra of commercial SWCNT from Tubes@Rice (further referred to as TR-SWCNT) in aqueous electrolyte solution. In continuing these efforts, the charging of SWCNT was studied also in non-aqueous medium (0.2 M LiClO4+acetonitrile). The work was further extended to SWCNT prepared by catalytic decomposition of CO (research sample obtained from Rice University, further referred to as CO-SWCNT). The SWCNT were deposited on Pt, Au, ITO (indiumtin oxide conducting glass) or Hg. The latter support avoids disturbances by hydrogen evolution in aqueous medium at higher cathodic potentials [5]. The ITO-supported SWCNT served also for in-situ Vis-NIR spectroelectrochemistry [5]. The set-up for in situ Raman spectroelectrochemistry employed a homemade electrochemical cell (Fig. 1). The cell can be used both in the microRaman regime and in the standard macro-chamber geometry. The first experimental routine allows a precise control of sampling area, which is important at mercury electrode and for the study of photoanodic breakdown of SWCNT (vide infra). Highlights 2000