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- Title
- ELECTROCHEMICAL CHARACTERIZATION OF DYE-SENSITIZED SOLAR CELLS
- Creator
- Ha, Seonbaek
- Date
- 2011-05-09, 2011-05
- Description
-
Dye-Sensitized Solar Cells (DSSCs) have been investigated using various methods including: varied illumination density, cyclic voltammetry (CV...
Show moreDye-Sensitized Solar Cells (DSSCs) have been investigated using various methods including: varied illumination density, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and equivalent circuit models. Under various illumination conditions, DSSCs were affected by many factors: exposure time, surrounding temperature, light intensity and UV (ultraviolet) radiation. In order to understand and identify aging phenomena, as well as ionic and electronic processes, a number of physical and electrochemical experiments were performed. The internal resistances among the components of DSSCs showed distinct features under different experimental conditions. For long-term stability and high performance of DSSCs, it is necessary to investigate the characteristics of these internal resistances and develop methods to reduce them. By using electrochemical impedance spectroscopy (EIS) and equivalent circuit models, it was possible to demonstrate the electrochemical phenomena and degradation characteristics of DSSCs.
M.S. in Chemical Engineering, May 2011
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- Title
- ELECTROCHEMICAL AND THERMAL BEHAVIOR OF ENERGY STORAGE AND CONVERSION SYSTEMS: LITHIUM ION BATTERIES AND PEM FUEL CELLS
- Creator
- Ha, Seonbaek
- Date
- 2015, 2015-05
- Description
-
In this dissertation, three major topics in electrochemical energy storage and conversion systems are discussed. Lithium-ion batteries as...
Show moreIn this dissertation, three major topics in electrochemical energy storage and conversion systems are discussed. Lithium-ion batteries as electrochemical energy storage and catalyst support in proton exchange membrane (PEM) fuel cells as an electrochemical energy conversion system has been investigated. Most work was done to understand the mechanism of an electrochemical reaction and performance degradation in both systems. After that, it was essential to overcome the technical challenges. The thermal stability of lithium-ion cells has been characterized by a novel cathode and anode material with an electrolyte. For electrochemical energy storage, LiFePO4 as a cathode material in a lithium-ion battery has been investigated by various electrochemical techniques. Generally, the electrode consists of an active material, polymer binder, and conducting agents. The electrode material compositions can affect the electrochemical performance by changing the ratio of carbon content to binder or active material content. The LiFePO4 electrodes were optimized by several factors; electronic conductivity, over voltage during discharge, area specific impedance, hybrid pulse power, and energy density. Silicon is a promising material as a novel anode material in lithium-ion batteries. The importance of selecting a polymer binder among various binders has been addressed by the experiments. The additive in the electrolyte also affects the interfacial property between the solid active material and the electrolyte. The effect of fluoroethylene carbonate (FEC) additive was investigated by electrochemical and physical characterization. The thermal stability of the silicon anode was studied by varying the FEC concentration. Metal oxide, as a non-carbon catalyst support in the PEM fuel cell, was chosen and developed to replace the carbon support for better electrochemical durability. The electronic conductivity; Brunauer, Emmett and Teller (BET) surface area; stability in acid media; and the electrochemical stability of fabricated Zr-doped In2O3 were evaluated.
Ph.D. in Chemical Engineering, May 2015
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