High-Temperature Applications of Solid Electrolytes Fuel Cells, Pumping, and Conversion

High-Temperature Applications of Solid Electrolytes Fuel Cells, Pumping, and Conversion 

Ceramic electrochemical reactors are currently undergoing intense investigation, the aim being not only to generate electricity but also to produce chemicals. Typically, ceramic dense membranes are either pure ionic (solid electrolyte SE) conductors or mixed ionic-electronic conductors (MIECs). In this chapter we review the developments of cells that involve a dense solid electrolyte (oxide-ion or proton conductor), where the electrical transfer of matter requires an external circuitry. When a dense ceramic membrane exhibits a mixed ionic-electronic conduction, the driving force for mass transport is a differential partial pressure applied across the membrane (this point is not considered in this chapter, although relevant information is available in specific reviews). 

The fields of applications range from metallurgy to the semiconductor industry, to medicine, the petrochemical industry, electricity production, chemical cogeneration (i.e., the simultaneous production of electricity, heat, and chemicals), atmospheric control within the laboratory, and so on. However, virtually no large-scale industrial applications have yet been reported, and for a variety of reasons, including  

Current and future advancements in materials engineering might, however, lead to a significant reversal of this trend, and in this context the lowering of operating temperatures represents the main target. By comparison, compared to conventional catalytic reactors, SEMRs could be used to produce expensive fine chemicals, with attractive yields. 

The single cells consist of a dense solid electrolyte membrane and two porous electrodes. In most cases, at least one of the electrodes is exposed to an oxygen-containing gas (often, ambient air), while the other electrode is exposed to an inert gas, a liquid metal, a partial vacuum, or a reacting mixture (hydrogen, water vapor, hydrocarbons, CO, CO2, etc.). The single-chamber reactor (SCR) has been also proposed either as a membrane reactor or as a fuel cell. In this case, the solid-electrolyte disk, with two different electrodes that are coated either on opposite sides or on the same side of the pellet, is suspended in a flow of the reacting mixture (see Section 12.6.3). 

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Fouletier, J., Ghetta, V. (2009). High-temperature applications of solid electrolytes fuel cells, pumping, and conversion. In Solid state electrochemistry I fundamentals, materials and their applications (pp. 397—426). 

High temperature or intermediate temperature electrochemical systems have been extensively studied for their potential advantages in terms of clean energy conversion with enhanced efficiency. However, these systems are mainly based on fragile ceramic materials, including solid electrolytes, electrodes and interconnector materials for solid oxide fuel cells, and other prospective solid state electrochemical systems, such as steam electrolysers, electrochemical oxygen pumps, etc. These ceramic-based systems are conditioned by mechanical limitations of cell materials, and mostly intended for stationary applications. 

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