LaCoO 3 : Promising cathode material for protonic ceramic fuel cells based on a BaCe 0.2 Zr 0.7 Y 0.1 O 3d electrolyte Sandrine Ricote a, * , Nikolaos Bonanos a , Filip Lenrick b , Reine Wallenberg b a Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde, Denmark b nCHREM/Center for Analysis and Synthesis, Lund University, Box 124, SE-221 00 Lund, Sweden highlights < Successful infiltration of LaCoO 3 into a porous BCY27 after 6 infiltrations of 1 mol L 1 solution. < Single phased LaCoO 3 formed after 2 h at 600  C in air. < LaCoO 3 does not degrade nor react with BCZY27 at temperatures up to 600  C. < Cathode ASR of 0.39 and 0.11 U cm 2 in air, pH 2 O ¼ 0.01 atm, at 500 and 600  C respectively. < Oxide ion conduction is not necessary in PCFC cathodes. article info Article history: Received 23 April 2012 Received in revised form 18 June 2012 Accepted 29 June 2012 Available online 7 July 2012 Keywords: PCFC BCZY Lanthanum cobaltite Cathode material Infiltration abstract Symmetric cells (cathode/electrolyte/cathode) were prepared using BaCe 0.2 Zr 0.7 Y 0.1 O 3d (BCZY27) as proton conducting electrolyte and LaCoO 3 (LC) infiltrated into a porous BCZY27 backbone as cathode. Single phased LC was formed after annealing in air at 600  C for 2 h. Scanning electron micrographs showed the presence of the infiltrated LC in the full cathode depth. Transmission electron micrographs revealed LC grains (60e80 nm) covering partly the BCZY27 grains (200 nme1 mm). Impedance spectra were recorded at 500  C and 600  C, varying the oxygen partial pressure and the water vapour pressure. Two arcs correspond to the cathode contribution: a middle range frequency one (charge transfer) and a low frequency one (oxygen dissociation/adsorption). The area specific resistances (ASRs) of both contributions increase when decreasing the oxygen partial pressure. The low frequency arc is inde- pendent on the water vapour pressure while the charge transfer ASR values increase with higher pH 2 O. The cathode ASRs of 0.39 and 0.11 U cm 2 at 500 and 600  C respectively, in air (pH 2 O ¼ 0.01 atm) are the lowest reported to the authors’ knowledge for PCFC cathodes. Furthermore, this work shows that the presence of oxide ion conduction in the cathode material is not necessary for good performance. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction After more than two decades of research on the electrolyte materials for protonic ceramic fuel cells (PCFCs) [1e4] efforts are now focused on cathode development. Additional challenges compared to those of SOFCs include formation of water vapour at the cathode side and slower electrode kinetics due to the lower operating temperatures (400e600  C). Because of the formation of water at the cathode of PCFCs, protonic conduction in the cathode is necessary in order to extend the reaction sites to the entire gas/ cathode interface. If protonic conduction is absent, the water will be formed only at the electrolyte/cathode interface. Cercer made of the electrolyte material (BaZr 0.1 Ce 0.7 Y 0.2 O 3d ) and a mixed oxide ion and electron conductor MIEC (Sm 0.5 Sr 0.5 CoO 3d referred to as SSC or Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3d referred to as BSCF) were used to impart protonic conduction to the cathode [5,6]. An optimal percentage of MIEC and proton conductor oxide exists for composite cathodes to get the lowest polarization resistance. In the case of SSCeBaCe 0.8 Sm 0.2 O 3d , this value was estimated to be circa 60 wt% of SSC [7]. However, due to the high temperature required for the cercer fabrication, cation interdiffusion was observed between the electrolyte material and MIEC. Infiltration of the MIEC into a porous backbone of proton conductor material was shown to be a good alternative, as this low temperature method prevents the cation interdiffusion [8]. Infiltration of electrode materials is commonly used for SOFC [9,10]: the particle size of the infiltrated MIEC is in * Corresponding author. Tel.: þ45 46 77 56 41; fax: þ45 46 77 58 58. E-mail addresses: sari@risoe.dtu.dk, sari@dtu.dk (S. Ricote). Contents lists available at SciVerse ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour 0378-7753/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jpowsour.2012.06.098 Journal of Power Sources 218 (2012) 313e319