Layered perovskites as electrocatalysts for energy conversion and storage systems

Abstract

With growing concerns over energy and environmental issues, sustainable and environmentally-friendly energy conversion and storage devices have received significant attention from both the academic and industrial communities. Solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), which are collectively referred to as solid oxide cells (SOCs), are attractive energy conversion and storage systems with high energy conversion efficiency and environmental benefits. SOFCs, which directly convert chemical energy (such as H2, CH4, C3H8, etc) into electricity, represent an efficient alternative combustion system for the production of electricity. Similarly, SOECs, which convert water to hydrogen, are a clean and efficient hydrogen production system. Ideally, SOFCs and SOECs should meet several criteria, such as high performance, long term stability, and relatively inexpensive cost. However, the operation of SOFCs and SOECs still accompanies several problems, especially in relation to the electrode materials. Conventional electrode materials suffer from insufficient performance, performance degradation, redox instability, coarsening, electrode delamination, and the formation of a secondary phase. In this regard, the development of electrode materials with both high conductivity and high and stable electrocatalytic activity is a vital step for the commercialization of SOFCs and SOECs. This dissertation focuses on layered perovskite based electrode materials for SOFCs and SOECs with an aim to overcome the problems noted above. These materials show outstanding performance and stability with fast electrochemical reaction kinetics. I first discuss basic principles and present a theoretical overview of solid oxide fuel cells and solid oxide electrolysis cells in chapter 1 and then describe the experimental techniques for the fabrication and characterization of electrode materials for SOFCs and SOECs in chapter 2. Finally, my research papers on the properties of electrode materials for SOFCs and SOECs are presented as outlined below,

1. Thermodynamic and electrical properties of Ba0.5Sr0.5Co0.8Fe0.2O3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ for intermediate-temperature solid oxide fuel cells. 2. Optimization of Sr content in layered SmBa1-xSrxCo2O5+δ perovskite cathodes for intermediate-temperature solid oxide fuel cells. 3. High redox and performance stability of layered SmBa0.5Sr0.5Co1.5Cu0.5O5+δ perovskite cathodes for intermediate-temperature solid oxide fuel cells. 4. Electrochemical properties of B-site Ni-doped layered perovskite cathodes for IT-SOFCs. 5. Correlation between fast oxygen kinetics and enhanced performance in Fe doped layered perovskite cathode for solid oxide fuel cells. 6. Achieving high efficiency and eliminating degradation in solid oxide electrochemical cells by using high oxygen capacity perovskite. 7. Novel hydrogen production system: Dual Solid Oxide Electrolyzer.