Perovskite-based oxygen transport

Dense ceramic ion-conducting membranes (CICMs) are emerging as an important class of inorganic membranes based on fluorite- or perovskite-derived crystalline structures [18]. Most of the ion-conducting ceramics discovered to date exhibit a selective ionic oxygen transport at high temperatures >700°C. Ionic transport in these membranes is based on the following successive mechanisms [25] ... 

The principles behind this membrane technology originate from solid-state electrochemistry. Conventional electrochemical halfceU reactions can be written for chemical processes occurring on each respective membrane surface. Since the general chemistry under discussion here is thermodynamically downhill, one might view these devices as short-circuited solid oxide fuel cells (SOFCs), although the ceramics used for oxygen transport are often quite different. SOFCs most frequently use fluorite-based solid electrolytes - often yttria stabUized zirco-nia (YSZ) and sometimes ceria. In comparison, dense ceramics for membrane applications most often possess a perovskite-related lattice. The key fundamental... 

In Section 13.63, it was stated that oxygen-conductive membranes are under development. These membranes are suitable for advanced power generation requiring oxygen for combustion or gasification and are based on zirconia and perovskite where oxygen is transported throngh the material as 0 . 

Plate-and-frame as well as spiral-wound modules house flat membranes. Capillary and hollow fibers are packed in larger bundles in a pressure vessel. Commercially relevant are flat membranes and hollow fibers. However, new developments in perovskite membranes for oxygen transport are based on tubular membranes as well. ... 

The oxygen reduction reaction occurs at the cathode. Nearly all candidate cathode materials are based on perovskite oxides such as lanthanum strontium manganite (LSM). However, the oxygen reduction reaction is particularly affected by lower operating temperatures with kinetics and transport processes that are thermally activated. The development of materials with higher electrochemical activities for the oxygen reduction reaction is critical for the development of IT-SOFCs with higher efficiencies. 

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