Study of Silicon Nitrate and Tin Dioxide Carbon Nanotube Composite as Lithium-ion Battery Anode, Gas Sensor and the Self-Assembly of Carbon Nanotubes on Copper Substrates
Hernández Lugo, Dionne M.
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Carbon nanotubes since their discovery have been used for many applications. They are predicted to reinforce novel composite materials because of their structural perfection, excellent mechanical properties and low density. CNT can be made into nanowires of different materials or as part of a composite making them beneficial for the incorporation into electrochemical devices. Carbon nanotubes in this study were gown directly on a copper substrate employing hot filament chemical vapor deposition (HFCVD). Bamboo-like carbon nanotubes were made into electrodes reducing the use of inactive materials on the development of working electrodes for electrochemical application. This BCNT were tested as lithium-ion battery anodes assembled together with high capacity materials such as Silicon and Tin Oxide (4200mAh/g and 782 mAh/g). On this study BCNT served as a conductive matrix as well as buffer matrix for the volume expansion brought by cycling silicon and tin oxide. The composite structural properties enhance the surface-to-volume ratio of the electrode demonstrating a desirable electrochemical performance for a lithium-ion battery anode. As a gas sensor electrode CNT was assembled with tin-oxide directly on a copper substrate for the detection of ethanol, methanol, ammonia and H2S. CNT gave a higher surface area and a conductive matrix aiding to the sensing capabilities of the SnO2 increasing the effectiveness of the matrix material for gas detection. Copper is known to produce CNT with a disturb structure. To develop an electrode on copper with well-ordered CNT other techniques need to be used. One way to do this is by chemical modification of the copper substrate with a molecule able to react with the carbon nanotube. For the attachment of well-ordered carbon nanotubes such as SWCNT a self-assembly monolayer technique is chosen. On this study 4- aminothiophenol served as the linker between the copper substrate and the carbon nanotubes. This study let to chemically attached CNT to a copper substrate surface resulting in a working electrode able to be used in electrochemical applications. The electrodes under study were characterized structurally using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform Infrared – Attenuated Total Reflectance (ATR-FTIR) Spectroscopy, X-ray diffraction (XRD) and Atomic Force Microscopy. The lithium-ion battery electrode was study electrochemically using cyclic voltammetry and charge-discharge profiles using a Gamry Potenstiostat at room temperature. The sensor device was developed in house.