- Title
- Synthesis and characterization of titanium dioxide nanotubes using electrochemical anodization technique for solar cell applications
- Creator
- Lupiwana, Mpheleki
- Subject
- Titanium dioxide Nanostructured materials Nanotubes
- Date
- 2017
- Type
- Thesis
- Type
- Masters
- Type
- Chemistry
- Identifier
- http://hdl.handle.net/10353/11795
- Identifier
- vital:39107
- Description
- High demand on energy conversion in dye-sensitized solar solar cells (DSSCs), requires development of well-organized TiO2 nanotube (TNT) structures because of their large surface area-to-volume ratio, superior lifetime and provision of optimal pathways for electron percolation. In this work TiO2 nanotube membranes with an average length of 2.40 μm and average pore diameter of 41.08 nm have been fabricated using electrochemical anodisation employing an organic electrolyte consisting of 0.5wt.percent NH4F + 3 vol percent H2O + Glycerol at an applied voltage of 60 V for 12 hours. The fabricated TNTs were annealed at different annealing temperatures. Scanning Electron Microscopy (SEM) showed that anodisation at these conditions yields nanotubes with periodic rings which present the roughness of the walls. Surface SEM images have revealed the presence of porous structures on the fabricated TNT membranes. Also evident from SEM cross-sectional images are multi-layered TiO2 nanotubes with top and bottom layers. The effect of annealing temperature on the structural, morphological and topographical has been investigated for TNTs. Surface SEM morphological analyses have revealed that the surface morphology of the annealed TNTs membranes changes with an increase in annealing temperature from 350°C to 650°C. The surface SEM analysis has revealed that as the annealing temperature increases the fabricated nanotubes deforms and collapses at annealing temperatures above 550°C. The TNTs annealed at 350°C have a modal pore size of 34.56 nm which is somewhat smaller compared to the TNTs annealed at 650°C with a modal pore size of 31.05 nm. Atomic Force Microscopy (AFM) topographical measurements have confirmed the presence of porous structure on the surface of the as-annealed TNTs with a modal pore diameter decreasing with increasing in annealing temperature. SEM-EDS analysis have revealed the presence of Ti, O and C and no other additional impurities. The presence of Ti and O confirms the successful electro-anodization of titanium metal sheets to TNTs. C must be due to glycerol electrolyte that got absorbed onto the TNTs structured during electro anodization. Structure investigation through X-Ray Diffraction (XRD) analysis has revealed that as-anodised TNTs have peaks at 2Ɵ positions 35.62°, 39.02°, 40.76°, 53.55°, 63.49°, 71.14°, and 76.71° belonging to the amorphous phase of TiO2. Additionally XRD analysis has revealed that for the annealed samples in the temperature range from 350°C to 450°C have peaks at 24.66° (101), 27.11° (110) belonging Anatase and Rutile phase of TiO2 respectively. Confocal Raman Spectroscopy (CRM) image analysis through a large area scan, and Raman depth profiling have also been used to evaluate the phase changes in TNTs annealed at different temperatures. CRM large area scan and depth profiling has revealed the presence of Anatase phase of TiO2 with Raman vibration modes at 142.37 cm-1, 199.04 cm-1, 394.67 cm-1,516.16 cm-1 and 639.29 cm-1 and the presence of some Rutile phase of TiO2 peaks with Raman vibration modes at 445.26 cm-1 and 612.07 cm-1. These findings were correlated to the XRD analysis, SEM analysis as well as AFM. In XRD the transformation of Anatase to Rutile phase was observed as the annealing temperature increased, that was also supported by SEM analysis whereby nanotube structures collapsed and deformed as annealing temperature increased due to phase transformation. In AFM pore diameter decreased as annealing temperature increases, which was also due to the effect of phase transformation observed in XRD and CRM. These findings showed that TiO2 nanotube membranes were successfully fabricated, which may have wide applications in the development of electronic materials for the solar devices.
- Format
- 115 leaves
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Pure and Applied Chemistry
- Language
- English
- Rights
- University of Fort Hare
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details | SOURCE1 | MSc (Chemistry) LUPIWANA, M.pdf | 4 MB | Adobe Acrobat PDF | View Details |