Understanding electro-catalysis to design perovskite based electrodes for Solid Oxide Cells

Kurzfassung

The traditional approach to enhance the performance of Solid Oxide Cells (SOC)relies on the functional materials with improved properties, such as enhanced electro-catalytic activity and optimized microstructure. Perovskite based Mixed Ionic and Electronic Conductors (MIEC) change the paradigm of the active sites in SOC electrodes by offering double phase boundaries (DBs) in addition to triple phase boundaries (TPBs). For instance, compounds from the (LaxSr1-x)1-yCo1-zFezO3-δ (LSCF) improved functionality of the air electrode, via a higher ionic conductivity, while compounds from the LaxSr1-xTiO3-δ (LST) due to dimensional stability in both reducing and oxidizing conditions significantly enhance tolerance of the fuel electrode towards redox cycles. Ce1-xGdxO2-α (CGO) itself present a significant MIEC behavior above 600 °C, typical of SOC operation. Hereby, we present the results of studies related to the development of flexible and durable (LaxSr1-x)1-yTiO3-δ (LST) – Ce1-xGdxO2-α (CGO) based fuel electrodes and (LaxSr1-x)1-yCo1-zFezO3-δ (LSCF) – Ce1-xGdxO2-α (CGO) based air electrode. Model electrodes with various phase proportion were produced and electrochemically characterized in relevant atmosphere and at various temperature. The identification of electrochemical processes on the active sites, the understanding of the electrochemical behavior and the identification of the rate limiting processes as a function of the operating temperature will be presented. The results obtained with DBs based electrodes implemented in a metal supported SOC and operated both in fuel cell and electrolysis mode will be presented and critically discussed in terms of performance, durability and tolerance towards poisons. The discussion will be further extended to the use of such materials in other traditional planar cell architectures.