Electrochemical investigation of a propane-fed solid oxide fuel cell based on a composite Ni–perovskite anode catalyst Massimiliano Lo Faro a, *, Daniela La Rosa a , Isabella Nicotera b , Vincenzo Antonucci a , Antonino Salvatore Arico ` a a CNR-ITAE Institute, Via Salita S. Lucia sopra Contesse 5, IT-98126 Messina, Italy b Universita ` degli Studi della Calabria, IT-87036 Arcavacata di Rende (CS), Italy 1. Introduction The use of dry hydrocarbons in intermediate temperature (500– 800 8C) solid oxide fuel cells (IT-SOFCs) has been intensively investigated in the recent years [1–3]. A significant attention has been focused on methane electro-oxidation by using different electrocatalysts including Cu/CeO 2 , Ni–Cu and various perovskites [1–5]. The perovskite materials have shown promising perfor- mances for natural gas combustion [5,6] and suitable activity for oxygen reduction [7] showing bi-functional properties. Encoura- ging results have been achieved at temperatures below 800 8C, especially in the presence of ceria electrolyte [1,4,5]. Some attempts have been addressed to the oxidation of larger molecular weight hydrocarbons in SOFCs [1,8]. It has been observed that the reaction rate for the oxidation of propane is lower compared to methane, especially because it involves several steps and formation of intermediates [8–15]; moreover, oxidation of dry propane is more affected than methane by the cracking process producing carbon fibers that poison the anode surface. This occurs especially in the case of Ni–cermet catalysts. These cermets usually contain up to 65 vol.% of metallic Ni, as electronic conducting phase, and yttria-stabilised zirconia as ion conducting phase [16,17]. Such composite catalytic layer allows an extension of the triple-phase boundary where the electrochemical reaction occurs. The formation of carbon deposits occurs under both direct oxidation and steam reforming conditions at intermediate temperatures in the presence of low steam to carbon (S/C) ratios [18,19]. However, an excess of water injected into the stream reduces the process efficiency and increases the water-manage- ment constraints. Propane is the main component of liquefied petroleum gas (LPG). This is an interesting fuel for SOFCs. It is cheap, widely available and it can be liquefied to facilitate its storage for specific applications. Due to these properties, desulphurised LPG has good properties to be used as fuel in portable power sources. For such applications, the oxidation of dry propane in SOFC is favoured since it does not require any special fuel or water management, thus, reducing the complexity of the system. For portable applications, the main requirements concern with the obtainment of suitable power densities and the simplicity of design as well as operation at intermediate temperatures. In this regard, ceria-based electrolytes have good perspectives since the lower electrical efficiency, usually associated to a partial electronic conductivity of this material as compared to the conventional yttria-stabilised zirconia, is compensated by the higher conductivity at lower temperatures. Applied Catalysis B: Environmental 89 (2009) 49–57 ARTICLE INFO Article history: Received 17 July 2008 Received in revised form 7 November 2008 Accepted 14 November 2008 Available online 24 November 2008 Keywords: Propane Direct oxidation La 2 NiO 4 Gadolinia-doped ceria IT-SOFC ABSTRACT A composite Ni–perovskite anode was investigated for operation in dry propane-fed intermediate temperature solid oxide fuel cells (IT-SOFC). A La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3 (LSFCO) perovskite, characterized by mixed electronic–ionic conductivity, was used to support a highly dispersed Ni-phase. However, the catalyst structure was modified during SOFC operation. X-ray diffraction analysis of the electrocatalyst showed that, after operation, Ni was mainly present as La 2 NiO 4 ; whereas, the LSFCO structure was partially modified into a lanthanum-depleted SrFe 1x Co x O 3y (SFCO) perovskite structure. These results were corroborated by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) analysis showed the presence of a suitable dispersion of a nanosized Ni-phase and a strong interaction of Ni-enriched particles with the perovskite substrate. High reaction rates for the propane reaction were achieved with this electrocatalyst while minimizing carbon deposition. Power densities of about 300 mW cm 2 for dry propane oxidation were obtained at 800 8C in the presence of a thick gadolinia- doped ceria electrolyte. Fuel cell time-tests indicated promising electrochemical stability. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +39 090 624241; fax: +39 090 624247. E-mail address: lofaro@itae.cnr.it (M. Lo Faro). Contents lists available at ScienceDirect Applied Catalysis B: Environmental journal homepage: www.elsevier.com/locate/apcatb 0926-3373/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2008.11.019