Perovskites Used in Fuel Cells

Abstract

Fuel cells are devices for energy generation with very high theoretical efficiency. Many researches were been carried out in the last few decades in order to develop reliable fuel cells. Solid oxide fuel cells SOFC and polymeric exchange membrane fuel cells PEMFC are those with more potential for commercial use. Specially for SOFC cathodes, many perovskites have been proposed as potential materials for this application. Nevertheless, other components of SOFC, such as the electrolytes, anodes and interconnects, have also been targeted with potential perovskites. More recently, the use of perovskites in PEMFC has also been proposed and studied. As many perovskite compositions can be used in SOFC components, some of the most important are discussed in this chapter and some recent works in perovskites for PEMFC are also referred. As a whole, in this chapter, the reader will find the relationship between the properties of perovskites with their compositions and the main effects of dopant agents regarding the utilization of these materials in different components of SOFC and in electrodes of PEMFC.Keywords: SOFC, IT-SOFC, PEMFC, Nonstoichiometric compounds . IntroductionFuel cells are devices that convert the chemical energy of a fuel directly into electrical energy and heat. The most common fuel is H , but other hydrocarbon compounds such as methanol, methane, natural gas, ethanol or others can also be used. A single cell is composed of three main components anode, cathode and electrolyte. For the effective use of fuel cells, single cells must be interconnected to increase the power production, which requires the use of two more components interconnects, for the serial electrical connection, and sealants, for the hermetic sealing of the set. The electrodes are permeated by the gases, fuel in the anode and oxygen air in the cathode, and they catalyse electrochemical reactions through electron capitation or © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.conduction from or to the reactive sites the electrolyte, an electrical insulator, promotes ionic conductivity. Figure shows a general schematic drawing of a fuel cell operation. The residual water if pure H is used can be produced in the anode or in the cathode and it will depend of the nature of the electrolyte. If the electrolyte is a cationic conductor, the water will form in the cathode and, conversely, if it is an anionic conductor, the water will be formed in the anode. In general, a fuel cell works similarly to a battery however, its energy is not stored in its electrodes, so there is no need for recharging because there is a continuous supply of fuel in the anode and oxidants air in the cathode. The electrical work provided by the electrochemical reactions does not consume the cell's components, which keeps o...

Recent advances, practical challenges, and perspectives of intermediate temperature solid oxide fuel cell cathodes

“…1b–d. 10–17 The deviation of the lattice from an ideal cubic structure can be calculated using the tolerance factor ( t ) as:where r A and r B are the ionic radii of A and B cations, respectively, and r O is the ionic radii of oxygen. The perfect cubic symmetry is obtained when t = 1, while t < 1 and t > 1 lead to the formation of less symmetric crystals with rhombohedral/orthorhombic (Fig.…”

“…Table 1 summarizes the most common techniques to synthesize perovskite-type SOFC cathodes and compares their advantages and disadvantages. 14–17 The solid-state synthesis method is a simple and mature technique, however, less homogeneity of the composition, grain growth due to sintering at high temperatures and lower surface area limiting their catalytic behaviour are some of the disadvantages of this method. 14–17 In contrast, the sol–gel technique benefits from a good homogeneity of the chemical composition, better control over grain size and processing at lower temperatures.…”

“…14–17 The solid-state synthesis method is a simple and mature technique, however, less homogeneity of the composition, grain growth due to sintering at high temperatures and lower surface area limiting their catalytic behaviour are some of the disadvantages of this method. 14–17 In contrast, the sol–gel technique benefits from a good homogeneity of the chemical composition, better control over grain size and processing at lower temperatures. 15–17 Another common technique is the co-precipitation method which produces single-phase perovskite oxides, but the synthesis time is longer due to a slow precipitation rate.…”

Investigation of Thermal, Structural and Electrical Properties of LaMnO&lt;sub&gt;3&lt;/sub&gt;-Sigma

“…These types are alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), polymeric electrolyte membrane fuel cell (PEMFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell (SOFC). In addition to the above category fuel cell also differ in other important aspects such as efficiency and operating temperature [4].…”

“…According to the outcome of different research the composition of the material, synthesis method and fabrication have significant impact on the cathode material of SOFC. In most cases, cathode is composed of a perovskite material [4]. Therefore, this study focuses only on cathode perovskite material.…”