Electrochemistry of Metallofullerene Films: The Major Isomer of Dy@C₈₂

Abstract

Solution-cast films of the major isomer of Dy@C(82) (Dy@C(82)(I)) have been studied by cyclic voltammetry (CV) in acetonitrile. The films are found to display pronounced and stable redox responses in solution. The reduction/reoxidation processes exhibit large splittings between the first two reduction and reoxidation waves. However, a pair of reversible oxidation and rereduction waves is observed after the reoxidation of a reduced film. The characteristics and the inter-relationship of these waves are uncovered by the CV technique, scanning electron microscopy (SEM), and UV/Vis-NIR spectra. A possible mechanism is proposed for the film electrode processes, which emphasizes the redox-induced structural reorganization of the metallofullerene film by the incorporation and expulsion of electrolyte ions into and out of the film. The influence of the counter ion diffusivity and the ion-pair stability on the electrochemical activity of the metallofullerene film has also been indicated.

Electroactive endohedral metallofullerene film electrodes in aqueous solutions

“…1(a). The electrochemical responses are similar to those of metallofullerenes dissolved in organic solvents with a Pt working electrode, but very different from that of the same film in acetonitrile containing 0.1 M TBAPF 6 with large redox peak splittings [18]. The cathodic waves at 0.040, À0.40, À1.04, and À1.35 V are ascribed the first, second, third, and fourth reduction states of Dy@C 82 , respectively.…”

“…Therefore, once the metallofullerenes are reduced or oxidized, the counter ions would diffuse relatively easily into the film so as to balance the resulting charge. This differs from the rearrangement that occurs in the C 60 or Dy@C 82 film in acetonitrile, where asymmetric redox waves were observed [18]. The key point here is that water plays a lubrication role for the counter ion diffusion.…”

“…4(a)). This morphology is very different from the aggregate form when dispersed on a Pt plate [18]. After repeated potential scans between 0.8 V and À1.5 V for several cycles in an aqueous solution of TBABr or KCl and rinses with water several times, the SEM images of the film appeared to be very different.…”

“…For the second reduction wave of Dy@C 82 , the peak current increases in the range of 10.0-100 mV/s linearly with the increase of the square root of the scan rate, implying a reversible diffusion process [43]. This is also completely different from the usual linear scan rate dependence observed for some solutioncast films [18,44]. Although such a phenomenon is not well understood at present, a possible scenario is that water permeates into the electroactive Dy@C 82 film during the CV scans.…”

“…Some properties of these films have been measured regarding their photoelectrochemistry and electrochemistry [14][15][16][17][18]. In particular, we have reported the first study on the electron transfer of the Dy@C 82 (I) film on electrode surfaces in an organic medium such as acetonitrile [18].…”