Novel electrode materials with double perovskite structure for IT-SOFC

Abstract

Solid oxide fuel cells (SOFCs) are widely viewed as promising energy conversion devices because of their high efficiency, low pollutant emissions, and excellent fuel flexibility at high operating temperatures (>1000 oC). These benefits notwithstanding, the high operating temperature leads to a number of problems, including high cost, electrode sintering, interface reactions between cell components, and material compatibility challenges. In efforts to overcome these issues, recent research has been directed toward developing intermediate temperature SOFCs (IT-SOFCs) operating from 500 to 700 oC to reduce fabrication costs, improve long-term performance, and extend the variety of material selections. However, there are major obstacles to the practical use of IT-SOFCs, including poor oxide-ion conductivity and poor catalytic activity of the conventional cathodes tracing from the reduced temperature. The development of a highly stable cathode material with both high oxide-ion conductivity and electrocatalytic activity thus could be an important step toward the commercialization of IT-SOFCs. Furthermore, the most attractive feature of SOFCs is fuel flexibility, which offers the possibility of direct utilization of hydrocarbons. However, the conventional anode for an SOFC, a composite consisting of nickel and yttria-stabilized-zirconia (YSZ), is easily deactivated by carbon formation when it is exposed to hydrocarbon fuels and vulnerable to sulfur poisoning. Consequently, alternative anode materials should be proposed to replace the Ni-based materials, focusing on achieving better sulfur tolerance and coking resistance.

This dissertation mainly focuses on the development of novel materials to resolve the fatal drawbacks of conventional SOFC electrodes (cathode and anode). These materials can be offered as a promising SOFC cathode and anode material with highly stable and remarkable power output. I started with basic principle and theory of overall solid oxide fuel cell in chapter 1 and then described the experimental procedure for electrochemical and thermodynamic properties in chapter 2. Finally my research papers studying cathode and anode materials for IT-SOFC are presented as following,

1. High performance SOFC cathode prepared by infiltration of Lan+1NinO3n+1 (n = 1, 2, and 3) in porous YSZ 2. The electrochemical and thermodynamic characterization of PrBaCo2-xFexO5+ (x = 0, 0.5, and 1) infiltrated into yttria-stabilized zirconia scaffold as cathodes for solid oxide fuel cells 3. Chemical compatibility, redox behavior, and electrochemical performance of Nd1-xSrxCoO3- cathodes based on Ce1.9Gd0.1O1.95 for intermediate-temperature solid oxide fuel cells 4. Electrochemical properties of an ordered perovskite LaBaCo2O5+-Ce0.9Gd0.1O2-composite cathode with strontium doping for intermediate-temperature solid oxide fuel cells 5. Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co2-xFexO5+ 6. The effect of calcium doping on improvement of performance and durability in layered perovskite cathode for intermediate-temperature solid oxide fuel cells 7. Highly Efficient and Redox Stable Layered Perovskite Ceramic Anode for SOFC: PrBaMn2O5