Engineering Commons^™

Hydrogen-Rich Syngas Derived From Smouldering Biomass And Hydrocarbon Wastes, Joshua K. Brown

Electronic Thesis and Dissertation Repository

In the face of climate change, the world is looking to new fuel sources to meet the surging global energy demand. Hydrogen has been proposed as a promising energy vector being both a net-zero carbon emitter and having one of the highest gravimetric energy densities of known fuels. Production of hydrogen, however, is difficult with many of the technologies which exist today failing to be economically feasible or environmentally sustainable. Smouldering has recently been developed as a cost effective and energy efficient technology for destruction of organic wastes. The unique reaction zones created within a smouldering system have the potential …

Hydrogen Production Via Photocatalytic Water Splitting Under Near-Uv And Visible Light Using Doped Pd Tio2, Bianca Rusinque

Electronic Thesis and Dissertation Repository

The present PhD thesis reports the modification of titanium dioxide (TiO₂) with palladium (Pd), to enhance hydrogen production via water splitting, using 2.0v/v% ethanol as a scavenger. Titanium dioxide was used as photocatalyst, given its ability to absorb photons, producing e^-/h⁺ pairs. Mesoporous TiO₂ was synthesized using a soft template, following the sol-gel method, to modify its morphological properties. Palladium was used as co-catalyst doping TiO₂ agent, narrowing the band gaps down to 2.51 eV, and creating additional active metal sites.

Water splitting experiments under near-UV and visible light irradiation were carried out …

High-Pressure Studies On The Transition From Red Phosphorus To Black Phosphorus, Heng Xiang

Electronic Thesis and Dissertation Repository

Black phosphorus (BP) is a promising material in many research fields. However, the transition process from amorphous red phosphorus (ARP) is elusive and hence hinders large scale synthesis and applications. This work describes the application of the high-pressure method to study the transition process from ARP to BP.

In this thesis, the following three objectives were achieved: (1) to understand the mechanism of the transition, (2) to facilitate the synthesis of BP by taking the advantage of less pure ARP, (3) to propose new methods of synthesizing BP-based materials, such as the moderately oxidized BP and the black phosphorus/ amorphous …

Doped Tio2 Nanowires For Applications In Dye Sensitized Solar Cells And Sacrifical Hydrogen Production, Qasem Alsharari

Electronic Thesis and Dissertation Repository

This thesis explores the synthesis of metal oxide 1-D nanowires using a sol-gel method in supercritical carbon dioxide (sc-CO₂), as an environmental friendly enabling solvent. Porous nanowires were synthesized and their performance was tested in dye sensitized solar cell and sacrifical hydrogen production. Titanium isopropoxide (TIP) was used as a precursor for titania synthesis while copper, bismuth and indium were examined as dopants, respectively. The sol-gel reactions were catalyzed by acetic acid in CO₂ at a temperature of 60 °C and pressure of 5000 psi. It was observed that acetic acid/monomer ratio > 4 produced nanowires while a …

Enhanced Solar Photocatalytic Hydrogen Generation And Water Treatment Using Hetero-Structure Photocatalysts, Ghodsieh Malekshoar

Electronic Thesis and Dissertation Repository

Among different approaches to overcome current environmental concerns, heterogeneous photocatalysis is recognized as a promising one. While there are various applications of photocatalysis including water splitting and water treatment, the overall efficiency of this process is still fairly low due to the two dominant drawbacks of current semiconductors, namely wide band gap and fast recombination of photo-generated charges, which restrict the photocatalytic reactions. Designing a hybrid photocatalyst composed of semiconductor hetero-junctions is a viable approach to address these challenges.

The objective of this research project is developing efficient photocatalysts via simple and practical synthesis methods in order to enhance the …

The Effects Of Volatile Fatty Acids On The Performance Of Microbial Electrolysis Cells, Nan Yang

Electronic Thesis and Dissertation Repository

This study investigated the performance of microbial electrolysis cells (MECs) fed with three common fermentation products: acetate, butyrate, and propionate. Each substrate was fed to the reactor for three consecutive-batch cycles. The results showed high current densities for acetate, but low current densities for butyrate and propionate (maximum values were 6.0 ± 0.28, 2.5 ± 0.06, 1.6 ± 0.14 A/m², respectively). Acetate also showed a higher coulombic efficiency of 87 ± 5.7 % compared to 72 ± 2.0 and 51 ± 6.4 % for butyrate and propionate, respectively. This paper also revealed that acetate could be easily oxidized …

Reductive Depolymerization Of Kraft Lignin For Chemicals And Fuels Using Formic Acid As A In-Situ Hydrogen Source, Shanhua Huang

Electronic Thesis and Dissertation Repository

In this thesis work, formic acid (FA) proved to be an effective in-situ hydrogen donor for the reductive de-polymerization of kraft lignin (KL). At the optimum conditions without catalysts, i.e., 300 ^oC, 1 h, 18.6 wt.% substrate concentration, 50/50 (v/v) water-ethanol medium at a FA-to-lignin mass ratio of 0.7, KL (M_w ~10,000 g/mol) was effectively de-polymerized, producing de-polymerized lignin (DL, M_w 1, 270 g/mol) at a yield of ~90 wt.% and wt.% yield of solid residue (SR). The effects of heterogeneous catalysts on KL reductive de-polymerization in 50/50 (v/v) water-ethanol medium were also investigated. At all conditions, …

Electrochemical And Surface Compositional Studies On Uranium Dioxide, Mayuri Razdan

Electronic Thesis and Dissertation Repository

This thesis describes electrochemical and surface compositional studies performed on a number of simulated nuclear fuel (SIMFUEL) materials under conditions relevant to permanent disposal of spent nuclear fuel in a geologic repository. This is important since a number of critical issues have been identified in the event of waste container failure. The research performed was mainly focused in three areas: (i) the influence of low pH on the surface chemistry of UO₂, since acidity could develop within corrosion product deposits and flaws in the fuel; (ii) the combined influence of dissolved H₂ and H₂O_{2 …}

Solar And Visible Light Driven Photocatalysis For Sacrificial Hydrogen Generation And Water Detoxification With Chemically Modified Ti02, Pankaj Chowdhury

Electronic Thesis and Dissertation Repository

Photocatalysis is a recognized approach where light energy is employed to excite the semiconductor material producing electron/hole pair which eventually involves in the detoxification of pollutants and/or water splitting producing hydrogen. Existing photocatalysts suffer from poor activity or no activity in visible light irradiation which restricts them from solar light utilization. This work is focused on two key applications of photocatalysis (i) sacrificial hydrogen generation, and (ii) phenol degradation in visible and/or solar light. Platinum was loaded on TiO₂ photocatalyst by solar photo-deposition method. Eosin Y dye was used as a sensitizer for sensitization of platinum loaded TiO_{2 …}

Investigation Of Bio-Hydrogen And Bio-Methane Production From Thin Stillage, Noha El-Sayed Nasr

Electronic Thesis and Dissertation Repository

An evaluation of single-stage and two-stage anaerobic digestion processes for biomethane and biohydrogen production using thin stillage was performed to assess the viability of biohydrogen production from thin stillage and the impact of separating the acidogenic and methanogenic stages on anaerobic digestion with hydrogen production in the first stage. A comparative evaluation of anaerobic digester sludge (ADS) and acclimatized anaerobic digester sludge (AADS) for biohydrogen production was performed at various S°/X° ratios. The optimum range of S°/X° ratio for hydrogen production was found to be 1 to 2 gCOD/gVSS using conventional ADS and 3 to 6 gCOD/gVSS using AADS. Maximum …

Enhancement Of Biohydrogen And Biomethane Production From Wastes Using Ultrasonication, Elsayed Elrefaey Elbeshbishy

Electronic Thesis and Dissertation Repository

This thesis demonstrated the feasibility of using ultrasonication to solubilize the particulate matter, suppress the growth of methanogens, and enrich the biohydrogen producers, thus overcoming the main challenge of biohydrogen systems i.e. long-term stability and contamination with methanogens. Furthermore, this work emphasized the benefits of applying ultrasonication inside a bioreactor over using it as a pretreatment for biohydrogen and biomethane production from wastes. The results of this work showed that sonicating hog manure at specific energy (SE) of 500 kJ/kg TS resulted in a 20% increase in methane production and 36% increase in VSS destruction. The viability of using ultrasonication …