Chemistry Commons^™

X-Ray Absorption And Emission Studies Of Anodic Titania Nanostructures, Jun Li

Electronic Thesis and Dissertation Repository

One-dimensional (1D) TiO₂ nanomaterials with ordered structure have been extensively applied in various fields, such as photocatalysts, solar cells, supercapacitors and rechargeable batteries, due to the unique structural and functional properties compared to the disordered nanoparticulate forms. Nevertheless, intrinsic disadvantages of TiO₂, such as its large band gap (~3 eV), fast recombination rate of photoexcited electron–hole pairs and insufficient ionic conductivity, severely limit the development of 1D TiO₂ nanomaterials for practical applications. To address the above issues, the scope of this thesis focus on the fundamental understandings of the electronic structure of highly ordered TiO_{2 …}

Nanostructured Air Electrodes And Electrochemical Reaction Mechanism Studies For Sodium-Oxygen Batteries, Hossein Yadegari

Electronic Thesis and Dissertation Repository

Alkali metal-O₂ batteries, i.e. Li- and Na-O₂, are considered as the next generation of energy saving technologies with potential application in electric transportation. The high theoretical energy density in these cells is related to the use of high energy alkali metals as negative and oxygen as the positive electrode materials. The performance of alkali metal-O₂ cells is highly dependent on the positive electrode material, where oxygen reduction and evolution reactions take place. Besides, the primary products of oxygen reduction reaction in these cells are typically metal oxides, which are insoluble in nonaqueous electrolytes, resulting in accumulation …

Model Of The Formation Of Iron Oxide Nanoparticles By Irradiation In Aqueous Media, Thomas I. Sutherland

Electronic Thesis and Dissertation Repository

This thesis aims to develop the mechanistic understanding of the formation of iron oxide nanoparticles by γ-irradiation. Under irradiation water breaks down into a wide array of redox active species (H•, •OH, H₂O₂, •e^-_(aq)) uniformly throughout the solution. These species are capable of rapidly interconverting any soluble Fe^II and insoluble Fe^III species resulting in the formation of nanoparticles with a narrow size distribution. The initial concentration of Fe²⁺ in the solution, the solution pH, the presence of any radical scavengers, the temperature of the reaction, and the dose rate of …

Development Of Novel Anode Materials For Lithium Ion Batteries, Mike A. Nieradko

Electronic Thesis and Dissertation Repository

This thesis focuses on the development of new anodes for Li ion batteries. Aluminium has been long considered as promising anode material for Li ion batteries because of its low cost, abundance, and low toxicity. Aluminium undergoes alloying with lithium through intermetallic LiAl formation which offers a relatively high theoretical capacity of 993 mAh/g compared to 372 mAh/g for graphite that is currently the principal anode material in commercial Li ion batteries. However, despite intensive research, all aluminium-based anodes tested so far suffered from rapid capacity fading and failure within first few cycles. Furthermore, there is insufficient understanding of the …

Photo-Isomerizable Self-Complementary Hydrogen Bond Arrays, Iamnica Janic Linares Mendez

Electronic Thesis and Dissertation Repository

This thesis exploits the use of a photochromic system in a self-complementary hydrogen bond array; i.e. the azo group, -N=N. The novelty of the approach described in this thesis resides in the double function of the azo group within the array: as a hydrogen bond acceptor site and as an element that promotes a structural change capable of disrupting the complexation equilibrium when irradiated with light.

The photo-isomerizable self-complementary hydrogen bond arrays presented are obtained by a general and practical synthetic method from inexpensive starting materials. Their self-complementary recognition was corroborated by ¹H NMR dilution experiments and single crystal …

Fractional Charge Methods For Correcting Approximate Kohn-Sham Potentials, Darya N. Komsa

Electronic Thesis and Dissertation Repository

The Kohn-Sham density functional theory relies on approximating the exchange-correlation energy functional or the corresponding potential. The behavior of the exchange-correlation potential as a function of position in a system can be used to detect and correct deficiencies of the parent functional. The too-fast decay of the potentials derived from common density functionals is a major problem, because it causes inaccurate Rydberg excitation energies and erroneous fractional charges in dissociating molecules. An efficient method to correct the shape of the exchange-correlation potential was proposed by Gaiduk et al. [A. P. Gaiduk, D. S. Firaha, and V. N. Staroverov, Phys. Rev. …

Mechanism Of Ethanol Partial Oxidation Over Titania Supported Vanadia Catalysts: Geometric And Electronic Structure Consequences On Reaction Kinetics, Dongmin Yun

Electronic Thesis and Dissertation Repository

Supported vanadium oxide catalysts (VO_x) are used for a wide range of industrial processes. A significant amount of research has been carried on this specific system with the aim to identify the critical parameters involved in catalytic activity. The results on this relative large body of research indicate that the catalyst support plays a critical role in determining the catalytic activity of vanadia and the use of titanium dioxide as support renders a catalyst with superior activity. Studies on supported vanadia on titanium oxide (VO_x/TiO₂) have provided an understanding on support interactions that result …

Development And Optimization Of Solid Polymer Electrolyte For Lithium Ion Batteries, Ladan Eskandarian

Electronic Thesis and Dissertation Repository

This thesis focuses on the development of new poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) in order to enhance their ionic conductivity at ambient temperature and fabricate the prototypes of novel Li ion batteries using these SPEs. Different types of SPEs have been developed: (i) blends of high molecular weight PEO and low molecular weight poly(vinyl acetate) (PVAc); (ii) composites of high molecular weight PEO and titanium dioxide (TiO₂)nanoparticles; and (iii) blend-based composite electrolytes consisting of PEO and PVAc with dispersed TiO₂. The SPEs were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and …

The Corrosion Of Carbon Steel Under Deep Geologic Nuclear Waste Disposal Conditions, Shannon L.W. Hill

Electronic Thesis and Dissertation Repository

The proposed disposal scenario for high-level nuclear waste (spent fuel) in Canada is emplacement within a sealed, deep geological repository (DGR) located in either granitic rock or sedimentary clay. Disposal is based on a multi-barrier approach, with the primary barrier being a sealed container which could be either dual-walled with a copper shell over an inner carbon steel vessel for granitic rock or a single thick-walled steel container for sedimentary clay. This study focuses on the corrosion behaviour of A516 Gr70 carbon steel as well as the corrosion products formed in a variety of groundwater compositions and concentrations expected within …