Synthesis of Porous Carbon Nanomaterials Derived From Non-Biodegradable Landfill Waste for Quantum Dot Solar Cells Counter Electrodes. (Research Proposal Sample)

Research Exposé
Proposed Title: Synthesis of Porous Carbon Nanomaterials Derived From Non-Biodegradable Landfill Waste for Quantum Dot Solar Cells Counter Electrodes.
1.0 Introduction
The declining fossil fuel resources and the anthropogenic destruction of the environment have threatened human beings' future existence on earth. There is a concerted effort worldwide to explore alternative sources of energy that are sustainable and environmentally benign. Sustainable energy sources include wind, geothermal, hydropower, solar, tidal and bio- energy. However, solar energy stands out due to its widespread and constant availability and low-cost setup, unlike wind, tidal and hydropower. Photovoltaic (PV) solar cells convert solar energy into electricity. The double-layer composed of semiconducting material generates electrical charges when exposed to sunlight. An ordinary PV system transforms approximately 4-17% of the sunlight into electricity (Chow, 2010). The conversion efficiency varies with PV cells and the state of the system. The remaining solar energy is converted to thermal energy. Excessive thermal energy my destroy the solar cell or reduce the conversion efficiency. The PV solar cells are subdivided into amorphous silicon solar cells, concentrated photovoltaic cells, dye-sensitized solar cells, nanocrystal solar cells and quantum dot solar cells, among others. Quantum dots solar cells (QDSC) are the most promising substitute for dye-sensitized solar cells, which suffer from low conversion efficiency and photocurrent density.
Quantum dots are minuscule nanometer-scale crystals made of semiconductor materials (Patel, 2011). Quantum dot solar cells can yield more affordable and efficient solar technology compared to the current silicon cells. Modifying their shape and size can result in a wider absorption of the solar radiation spectrum (Patel, 2011). In this regard, diverse counter electrode materials have been explored to improve the performance and efficiency of quantum dot solar cells. Carbon-rich materials used so far include porous carbon harvested from human hair (Sahasrabudhe, Kapri, & Bhattacharyya, 2016), mesoporous carbon- titanium mesh (Du et al., 2016), mesoporous carbon nanofibers (Fang et al., 2011) and biomass-derived carbon (Briscoe, Marinovic, Sevilla, Dunn, & Titirici, 2015). The mesoporous carbon-Ti-mesh counter electrode attained a conversion efficiency and fill factor of 11.16 and 0.677, respectively. In comparison, the mesoporous carbon nanofibers yielded a photoconversion efficiency and a fill factor of 4.81% and 0.6, respectively.
2.0 Problem statement
The main challenges facing quantum dots are photoluminescence, low fill factor, limited photovoltage (Du et al., 2016) and a spectrum absorption that depends on size (Ahmed, 2013). However, this disadvantage has been used to increase its conversion efficiency by using QDs as down-conversion materials. When used in this technique, they absorb a quantum of light in the blue region of the electromagnetic spectrum and emit photons in the higher wavelength electromagnetic region where the device has the best quantum efficiency. This results in better conversion efficiency and spectra response. In an attempt to improve the power conversion efficiency, fill factor and photostability of QDSC, a novel porous carbon derived from landfill waste will be used as a counter electrode material in this study.
3.0 Significance of the research
The proposed research will add knowledge and expertise in using non-biodegradable wastes as precursors for porous carbon QDSC counter electrodes. The proposed synthesis method is economical and environmentally friendly, with no carbon monoxide emissions and carbon dioxide. It has the potential to yield porous carbon with high power conversion efficiency. Converting non-biodegradable landfill waste into porous carbon will help address health and environmental concerns associated with landfill sites. In addition, if successful, it will present an affordable and sustainable method for landfill waste value addition. A notable benefit of porous carbon is that they are potentially multipurpose and can be applied in carbon dioxide capture and oil spill cleanup.
General objectives
1 The proposed research's main objective will be to develop porous carbon materials derived from non-biodegradable landfill waste for quantum dot solar cells counter electrodes.
Specific objectives
1 The main objective of the study will be attained by pursuing the following specific objectives:
2 Synthesis of porous carbon nanomaterials via hydrothermal carbonization, sonication, templating and chemical activation.
3 Materials characterization to determine the surface and cross-sectional morphology, particle size, crystal structure, surface area and pore size distribution
4 Analyze the electrical and electrochemical performance of the synthesized carbon nanomaterials as counter electrodes.
5.0 Research questions
1 Which is the best synthesis method for porous carbon?
2 What will be the surface area, crystal structure, pore size distribution, and morphology of the synthesized porous carbon?
3 What will be the power conversion efficiency and charge transfer resistance of the porous carbon?
6.0 Methodology
Carbon-rich non-biodegradable waste such as plastics (polyvinyl chloride and polythene bags) and electronic waste will be collected from nearby landfill sites. They will be cleaned with distilled water then dried in an oven for 12 h. The hydrothermal carbonization of landfill waste will be performed in tubular reactors. Waste containing ferric and ferrous iron oxide will be added to catalyze the carbonization process. Dry waste and deionized water will be loaded onto the tubular reactors (Berge et al., 2011). The solid waste concentration will be varied between 20 and 40% wt. The tubular reactors will be heated at temperatures between 180 and 250 oC and for periods ranging between 10 and 48 h. Temperature and time optimization will be conducted to determine optimal parameters. After optimizing temperature and time, the oven's reactors will be cooled in a water bath (Berge et al., 2011). In the second step, the carbon obtained will be sonicated for 6 h (with an ultrasonic probe and water as the solvent) then dried at 100 oC.
In the third step, the sonicated carbon will undergo manganese oxide (MnO2) templating. This step aims to obtain mesoporous carbon. Templating will be achieved by mixing hydrochar and manganese in the ratios 1:1, 1:2 and 1:3. The mixture will be heated in a tube furnace under inert gas flow at temperatures ranging between 400 and 600 oC for 1-3 h. The obtained hydrochar-MnO2 composite will be treated with oxalic acid to remove MnO2. The mesoporous carbon will be chemically activated with potassium hydroxide (KOH) in a tube furnace under nitrogen gas flow in the fourth step. The KOH to carbon ratios will be optimized and the activation time and temperature to obtain a material with optimal surface area, fill factor, and energy conversion efficiency.
Benefits of hydrothermal carbonization include yielding sp2 and sp3 hybridized carbon (Guiotoku, Maia, Rambo, & Hotza, 2003) and high carbon conversion efficiency (Poeschmann, Weiner, Woszidlo, Koehler, & Kopinke, 2015). Chemical activation of template carbon leads to higher surface area and pore volume (Jin, Tanaka, Egashira, & Nishiyama, 2010). The porous carbon obtained will be used with cadmium sulfide (CdS) quantum dots because various studies have confirmed that carbon-based materials exhibit the best performance in CdS quantum dot solar cells (QDSC) as compared to Cadmium Selenide (CdSe) QDSC (Jun, Careem, & Arof, 2014).
Materials Characterization
Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) instruments will obtain topographical