Heller Iddo, Kong Jing, Williams Keith A, Dekker Cees, Lemay Serge G
Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
J Am Chem Soc. 2006 Jun 7;128(22):7353-9. doi: 10.1021/ja061212k.
We present a theoretical description of the kinetics of electrochemical charge transfer at single-walled carbon nanotube (SWNT) electrodes, explicitly taking into account the SWNT electronic band structure. SWNTs have a distinct and low density of electronic states (DOS), as expressed by a small value of the quantum capacitance. We show that this greatly affects the alignment and occupation of electronic states in voltammetric experiments and thus the electrode kinetics. We model electrochemistry at metallic and semiconducting SWNTs as well as at graphene by applying the Gerischer-Marcus model of electron transfer kinetics. We predict that the semiconducting or metallic SWNT band structure and its distinct van Hove singularities can be resolved in voltammetry, in a manner analogous to scanning tunneling spectroscopy. Consequently, SWNTs of different atomic structure yield different rate constants due to structure-dependent variations in the DOS. Interestingly, the rate of charge transfer does not necessarily vanish in the band gap of a semiconducting SWNT, due to significant contributions from states which are a few k(B)T away from the Fermi level. The combination of a nanometer critical dimension and the distinct band structure makes SWNTs a model system for studying the effect of the electronic structure of the electrode on electrochemical charge transfer.
我们给出了单壁碳纳米管（SWNT）电极上电化学电荷转移动力学的理论描述，明确考虑了SWNT的电子能带结构。SWNTs具有独特且低密度的电子态密度（DOS），这表现为量子电容的较小值。我们表明，这在伏安实验中极大地影响了电子态的排列和占据情况，进而影响了电极动力学。我们通过应用电子转移动力学的Gerischer - Marcus模型，对金属型和半导体型SWNTs以及石墨烯上的电化学进行建模。我们预测，半导体或金属型SWNT的能带结构及其独特的范霍夫奇点可以在伏安法中得到分辨，其方式类似于扫描隧道谱。因此，由于DOS中与结构相关的变化，不同原子结构的SWNTs会产生不同的速率常数。有趣的是，由于距费米能级几个k(B)T的态的显著贡献，电荷转移速率在半导体型SWNT的带隙中不一定为零。纳米级临界尺寸与独特能带结构的结合，使SWNTs成为研究电极电子结构对电化学电荷转移影响的模型体系。
