| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Thursday Sessions |
| Session NS-ThM |
| Session: | Nanotube Devices and Processes |
| Presenter: | Y.-G. Lin, National Chiao Tung University, Taiwan |
| Authors: | Y.-G. Lin, National Chiao Tung University, Taiwan Y.-K. Hsu, Academia Sinica, Taiwan J.-L. Yang, National Chiao Tung University, Taiwan S.-Y. Chen, National Chiao Tung University, Taiwan K.-H. Chen, Academia Sinica, Taiwan L.-C. Chen, National Taiwan University |
| Correspondent: | Click to Email |
With the recent advancements in nanoscience and nanotechnology, carbon nanotubes (CNTs) have drawn a great deal of attention as novel catalyst supports due to their unique structure, high surface area, stability, and excellent mechanical and electrical properties, all of which could offer improvements for fuel cell applications. We have developed a method to synthesize well-aligned nitrogen-containing carbon nanotube (CNx NT) by microwave-enhanced chemical vapour deposition with a source gas of CH4, N2, and H2. Here we report our recent results on employing different flow rate of nitrogen to control the structure and electrochemical activity of CNx NTs. The effect of nitrogen on the structure and electrochemistry has been examined by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photonelectron spectroscopy (XPS), and cyclic voltammetry (CV) using the redox probe of Fe(CN)63-/Fe(CN)64-. From the structural investigation, as the flow rate of N2 gas is higher than 120 sccm, the average diameter of the nanotubes goes beyond 100 nm. The intensity ratio of the D band to G band of Raman spectrum increased with increasing N2 flow rate from 0 to 40 sccm, and then rapidly decreased with further increase in the flow rate of N2. Similarly, XPS results showed the highest nitrogen concentration occurred at 40 sccm and the intensity of pyridine-type N bonding which causes the interlinked node morphology inside the CNx NTs increased with increasing N2 gas flow rate. Hence, the nitrogen-incorporation promotes the disorder in graphitic structure in the initial stage; however, further increase in the N2 flow rate won’t enrich the nitrogen concentration in CNx NTs, but raise the growth temperature leading to enhanced graphitization. In addition, CNx NT electrode with N2 flow rate of 40 sccm was found to significantly improve the electron transfer kinetics of Fe(CN)63-/4- redox couple, approaching almost reversible electron transfer kinetics. The reason could be ascribed that the nitrogen treatment at 40 sccm creates disordered and chemically active sites which play a key role to facilitate electron transfer.