Metal/Metal Oxide Composites for Environmental and Energy Applications
| Autor: | Rini Ravindranath, 李妮 |
|---|---|
| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 This thesis focuses on synthesizing metal/metal oxide and graphene based low-dimensional materials for use in environmental remediation and energy applications. The thesis is divided into five parts. Chapter one introduces the rise of nanomaterials and nanotechnology and also provides an overview of the metal oxide photocatalysts that have been developed. Also introduced are nanomaterials used in removing heavy metals and green nanomaterials that can be used as an alternative to direct methanol fuel cells (DMFCs). In chapter two, photocatalytic titanium dioxide- gold nanospheres (TiO2-Au NSs) are used for the degradation of toxic dyes such as methylene blue (MB) and to reduce inorganic pollutants such as Cr6+ to Cr3+. Under UV irradiation, TiO2–Au NSs provide high catalytic activity for the degradation of MB and reduction of Cr6+ within 15 and 60 min, respectively. It can also be used for highly sensitive, selective and colorimetric detection of mercury (Hg). The method provides linearity (R2 = 0.98) for Hg2+ over a concentration range of 10.0 to 100.0 nM, with a limit of detection (LOD) of 1.5 nM. Using a low-cost smartphone APP that records the color changes (ΔRGB) of MB solution based on the Red-Blue-Green (RGB) component values, this TiO2-Au NSs/MB approach provides LOD of 2.0 nM for Hg2+ and 5.0 nM for CH3Hg+, respectively. In chapter three, we talk about the development of stable absorbents made of iron oxide/aluminum oxide microboxes (Fe2O3/Al2O3). The microboxes with a cubic structure (1 ± 0.09 µm) possess large specific surface area (208.3 m2 g-1) and high adsorption capacity (216 mg g-1) and were used for the removal of Hg2+ (100 ppm) from various samples, including tap water, lake water and tomato juice, with efficiencies of 98.2 ± 0.4, 98.5 ± 0.3 and 97.1 ± 0.5%, respectively. The microboxes are efficient adsorbents mainly because of a synergetic effect provided by the two metal oxides and high surface area. Chapter four explains the work done on the development of alternative catalysts for oxygen reduction reactions (ORR). Hybrid silicon nanosheets (NSs)–graphene quantum dot nanocomposites (Si–GQD NCs) were prepared from a mixture of GQDs and Si NSs in ethanol at 25 °C for 2 h. The onset potential of the Si–GQD NC electrode is -0.33 V (versus Ag/AgCl) with a current density of 2.61 ± 0.27 mA cm-2, showing greater electrocatalytic activity. The environmentally-friendly, active, stable and inexpensive Si–GQD NCs hold great potential for DMFCs. The final chapter talks about free-standing reduced graphene oxide-copper oxide-polyvinyl alcohol (RGO-Cu2O-PVA) film that has been developed for the reducing carbon dioxide (CO2) electrochemically. The low-cost and stable RGO-PVA-Cu2O film allows selective reduction of CO2 to CH3OH, with a current density of 9.04 mA cm-2 at -0.85 V and 96% Faradaic efficiency. The development of metal/ metal oxide and graphene based low-dimensional materials offers potentials for further energy and environment-related applications such as energy storage and conversion, clean water, and pollution remediation among others. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|