The objective of this award is to elucidate the mechanism of a novel self-rising approach for the synthesis of hierarchically porous electrodes for solid oxide fuel cells (SOFCs). SOFCs convert chemical energy from the fuel directly to electricity, offering high efficiency with zero to low emissions. SOFCs operating at reduced operating temperatures (400-600 degrees C) have commercial advantages, but the cell performance is mainly limited by the sluggish electrode reactions at reduced temperatures. The advantages offered by hierarchically porous electrodes include dramatically increased active surface areas for fast electrode kinetics and enhanced mass transport. The project will study the different parameters influencing porous network formation to achieve hierarchically porous microstructure and to apply the hierarchically porous electrode to improve the performance of SOFCs at reduced temperatures. A fundamental understanding of the synthesis, processing, and properties of hierarchically porous electrodes is essential to the rational design of a new generation of SOFCs.
This project is expected to create a unique self-rising method in the dynamic control of the pore size and geometry so that hierarchically porous materials can be economically and reproducibly fabricated. Utilization of hierarchically porous electrode is expected to bring significant enhancement of SOFC performance at reduced operating temperatures. This project is expected to have significant impacts on improving energy conversion efficiency and environmental quality. By active dissemination of the self-rising approach, it will offer the scientific community a unique technique to economically and efficiently produce hierarchically porous materials in other applications such as drug delivery, sensing, catalysis and adsorption. Outreach to high school students and the general public to promote the interest and awareness of the fuel cell technology as well as the training of graduate and undergraduate students through this project will help transfer the solid oxide fuel cell technology to US industry, thus enhancing its global competitiveness.
The focus of this NSF award is to develop a self-rising method for the synthesis of hierarchically porous mixed ionic and electronic conductors as electrodes for solid oxide fuel cells (SOFCs). Solid oxide fuel cells (SOFCs) convert chemical energy from the fuel directly to electricity, offer high system efficiency and are environmentally benign. SOFCs operating at reduced temperatures (400-600 Celsius) are of particularly interest, but the cell performance is mainly limited by the sluggish oxygen reduction process in the cathode at these temperatures. The cathode performance is directly related to the cathode microstructures. In this NSF project, a novel self-rising approach has been developed to synthesize a new generation of SOFC cathode consisting of hierarchically porous mixed ionic-electronic conductors (MIECs). The advantages offered by hierarchically porous MIEC electrodes include dramatically increased active surface areas for fast electrode kinetics, a significantly increased population of conductive defects for enhanced charge transfer process, shorter diffusion lengths for rapid mass and charge transport, and increased flexibility in surface modification for catalysis. The project has developed a fundamental understanding of the working mechanism of the self-rising approach, studied the different parameters influencing porous network formation to achieve hierarchically porous microstructure, and applied the hierarchically porous mixed ionic and electronic conducting electrode to improve the performance and durability of SOFCs at reduced temperatures. In addition, a transient SOFC model has been developed that links the multi-physics process with porous material microstructure. Furthermore, mechanistic electrochemical impedance spectroscopy (EIS) modeling has been developed to understand the cathode process, and to identify the physically distinct processes involved in the SOFC cathode. The fundamental understanding of synthesis, processing, and properties of hierarchically porous mixed ionic and electronic conducting electrodes obtained from this NSF support is essential to the rational design of a new generation of SOFCs with enhanced performance and durability. Key outcomes of this project include producing multiple peer-reviewed publications, presenting at national and international technical conferences, training both graduate and undergraduate students in materials science and energy conversion and storage, offering one-week summer program in fuel cells to high school students, and outreaching to K-12 students and the general public to promote the interest and awareness of the fuel cell technology.
