Application of nano cerium oxide in solid oxide fuel cells

Abstract

This review is analyzed the state of modern literature on the nanoceria based materials application as components for solid oxide fuel cells. The principle of operation of fuel cells, their classification and the difference in the constructions of fuel cells are described. The unique redox properties of nanosized cerium oxide make this material promising for application as components for solid oxide fuel cells (SOFC). Because of high ionic conductivity, high coefficient of thermal expansion and low activation energy at relatively low temperatures, cerium-containing materials are widely used as a solid electrolyte. On the surface of nanosized CeO2 there many surface defects (which is determined by the concentration of oxygen vacancies) that lead to the electronic conductivity increases even at temperatures (300 - 700 °C). The concentration of surface defects can be increased by doping the surface of nanoceria by divalent and trivalent cations. The ionic and electrical properties of the obtained nanocomposites dependent from synthesis methods, ionic radii and concentration of doping cations. It is explained the effect of the transition in the size of cerium oxide particles in the nanoscale region on the concentration of surface defects and defects in the sample structure. Particular attention is paid to the effect of doping nanosized CeO2 by transition metal cations and lanthanides on the characteristics of the obtained material, namely, on the increase of concentration of surface defects due to the increase of oxygen vacancies. It is established that nanosized cerium oxide is used for the development and implementation of the main components of SOFC: electrolyte, anode and cathode. Advantages of using solid electrolytes based on nanosized cerium oxide over the classical electrolytes are listed. It was shown that doping of cerium oxide by double and triple cations lead to increase the ionic conductivity and reduces the activation energy and has a positive effect on its characteristics as a SOFC electrolyte. Composites, based on nanoscaled cerium oxide, are actively developed and studied for use as electrodes of solid oxide fuel cells. Cerium-containing anodes are resistant to the deposition of carbon and fuel impurities, increase the catalytic activity of solid oxide fuel cells, and compatible with other components. Nanosized cerium oxide particles are sprayed onto the cathode to prevent the cathode from interacting with the electrolyte. The prospects for the use of cerium-containing materials for the conversion of chemical energy of fuel into electrical energy are analyzed.