Quantitative nanoscale visualization of heterogeneous electron transfer rates in 2D carbon nanotube networks
| Autor: | Julie V. Macpherson, Patrick R. Unwin, Michael E. Snowden, Aleix G. Güell, Kim McKelvey, Neil Ebejer |
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| Rok vydání: | 2012 |
| Předmět: |
Materials science
Finite Element Analysis Nanotechnology 02 engineering and technology Carbon nanotube 010402 general chemistry Electrochemistry 01 natural sciences Redox Electrochemical cell law.invention Electron Transport Electron transfer law Computer Simulation Electrodes Nanoscopic scale Microscopy Multidisciplinary Nanotubes Carbon Electrochemical Techniques Silicon Dioxide 021001 nanoscience & nanotechnology Electron transport chain 0104 chemical sciences Electrochemistry Special Feature Electrode 0210 nano-technology Oxidation-Reduction |
| Zdroj: | Proceedings of the National Academy of Sciences |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1203671109 |
| Popis: | Carbon nanotubes have attracted considerable interest for electrochemical, electrocatalytic, and sensing applications, yet there remains uncertainty concerning the intrinsic electrochemical (EC) activity. In this study, we use scanning electrochemical cell microscopy (SECCM) to determine local heterogeneous electron transfer (HET) kinetics in a random 2D network of single-walled carbon nanotubes (SWNTs) on an Si/SiO 2 substrate. The high spatial resolution of SECCM, which employs a mobile nanoscale EC cell as a probe for imaging, enables us to sample the responses of individual portions of a wide range of SWNTs within this complex arrangement. Using two redox processes, the oxidation of ferrocenylmethyl trimethylammonium and the reduction of ruthenium (III) hexaamine, we have obtained conclusive evidence for the high intrinsic EC activity of the sidewalls of the large majority of SWNTs in networks. Moreover, we show that the ends of SWNTs and the points where two SWNTs cross do not show appreciably different HET kinetics relative to the sidewall. Using finite element method modeling, we deduce standard rate constants for the two redox couples and demonstrate that HET based solely on characteristic defects in the SWNT side wall is highly unlikely. This is further confirmed by the analysis of individual line profiles taken as the SECCM probe scans over an SWNT. More generally, the studies herein demonstrate SECCM to be a powerful and versatile method for activity mapping of complex electrode materials under conditions of high mass transport, where kinetic assignments can be made with confidence. |
| Databáze: | OpenAIRE |
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