Journal of Power Sources 172 (2007) 768–774 On the nanostructuring and catalytic promotion of intermediate temperature solid oxide fuel cell (IT-SOFC) cathodes Jos´ e M. Serra ∗ , Hans-Peter Buchkremer Forschungszentrum J¨ ulich GmbH, Institute for Materials and Processes in Energy Systems, IEF-1, D-52425 J ¨ ulich, Germany Received 16 October 2006; received in revised form 30 April 2007; accepted 13 May 2007 Available online 18 May 2007 Abstract Solid oxide fuel cells (SOFCs) are highly efficient energy converters for both stationary and mobile purposes. However, their market introduction still demands the reduction of manufacture costs and one possible way to reach this goal is the decrease of the operating temperatures, which entails the improvement of the cathode electrocatalytic properties. An ideal cathode material may have mixed ionic and electronic conductivity as well as proper catalytic properties. Nanostructuring and catalytic promotion of mixed conducting perovskites (e.g. La 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3-δ ) seem to be promising approaches to overcoming cathode polarization problems and are briefly illustrated here. The preparation of nanostructured cathodes with relatively high surface area and enough thermal stability enables to improve the oxygen exchange rate and therefore the overall SOFC performance. A similar effect was obtained by catalytic promoting the perovskite surface, allowing decoupling the catalytic and ionic-transport properties in the cathode design. Noble metal incorporation may improve the reversibility of the reduction cycles involved in the oxygen reduction. Under the cathode oxidizing conditions, Pd seems to be partially dissolved in the perovskite structure and as a result very well dispersed. © 2007 Elsevier B.V. All rights reserved. Keywords: Fuel cell; Solid oxide fuel cell; SOFC; Perovskite; Electrocatalysts; Nanostructuring 1. Introduction Solid oxide fuel cells (SOFCs) are promising candidates for high efficiency energy production in the near future. SOFCs allow transforming directly the chemical energy of a fuel into electrical energy producing as by-product a high-quality hot stream. This heat can readily be used for different applications, as for instance the co-generation by means of microturbines, increasing in turn the overall system efficiency. Fuel flexibility is one important advantage with respect to PEM fuel cells, since it is possible to feed, besides H 2 , directly hydrocarbons into the cell anode. Especially interesting is the use of not only natu- ral gas, diesel, (bio-)alcohols but also gasified coal or biomass [1–3]. In principle, SOFCs do not require external reforming, water–gas-shift and CO selective oxidation catalytic convert- ∗ Corresponding author. Present address: Instituto de Tecnolog´ ıa Qu´ ımica (UPV-CSIC), av. los Naranjos s/n, E-46022 Valencia, Spain. Tel.: +34 963 877 819; fax: +34 963 877 809. E-mail address: jsalfaro@itq.upv.es (J.M. Serra). ers due to the anode internal reforming and the CO tolerance. Nevertheless, sulfur poisoning [4], coking and redox stability [5] at the anode are issues still to be enhanced. Indeed, the advantages of SOFC are as consequence of: (i) the high operat- ing temperature (600–900 ◦ C), allowing the use of non-precious metal electrocatalysts, heat recovery and the superior ionic con- ductivity of the different components; and (ii) the fact that the cell consists of assembled solid ceramic components. Never- theless, the current SOFC technology suffers from two main drawbacks that must be overcome before up-scaling and launch to the market: (i) the high price of the produced kWh due to the manufacturing costs; and (ii) the high operating temperature (>750 ◦ C), which increases the costs of construction materials and the starting-up time, shortens the operating life of the fuel cell stack, and therefore decreases the scope for domestic and vehicle power generation applications. As a consequence, there exists the need of improving the tolerance to direct hydrocarbon fueling with impurities and decreasing the operating temper- ature to 700–500 ◦ C. Consequently, the catalytic performance and ionic conductivity of both electrodes have to be strongly improved at those intermediate temperatures. The current limita- 0378-7753/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2007.05.018