Electrochemistry at single-walled carbon nanotubes: The role of band structure and quantum capacitance
Electrochemistry at single-walled carbon nanotubes: The role of band structure and quantum capacitance
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DOI：
10.1021/ja061212k
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发表时间：
2006-06-07
影响因子：
15
通讯作者：
Lemay, Serge G.
中科院分区：
文献类型：
--
作者：
Heller, Iddo;Kong, Jing;Lemay, Serge G.
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，明确考虑了单壁碳纳米管的电子能带结构。单壁碳纳米管具有明显且低的电子态密度(DOS)，用小的量子电容值表示。我们发现，这对伏安实验中电子态的排列和占据有很大的影响，从而影响了电极动力学。通过应用电子转移动力学的Gerischer-Marcus模型，我们模拟了金属和半导体单壁碳纳米管以及石墨烯的电化学。我们预测，半导体或金属SWNT能带结构及其独特的van Hove奇点可以用类似于扫描隧道光谱的方式用伏安法来分辨。因此，不同原子结构的单壁碳纳米管由于DOS随结构的不同而产生不同的速率常数。有趣的是，由于远离费米能级几个k(B)T的态的显著贡献，电荷转移速率并不一定在半导体单壁碳纳米管的带隙中消失。纳米级的临界尺寸和清晰的能带结构使单壁碳纳米管成为研究电极电子结构对电化学电荷转移影响的模型系统。
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.