Compositional Engineering of a La1-xBaxCoO3-δ-(1-a) BaZr0.9Y0.1O2.95 (a = 0.6, 0.7, 0.8 and x = 0.5, 0.6, 0.7) Nanocomposite Cathodes for Protonic Ceramic Fuel Cells.

Laura Rioja-Monllor,Marie-Laure Fontaine,Mari-Ann Einarsrud,Tor Grande,Carlos Bernuy-Lopez

doi:10.3390/ma12203441

Abstract

Compositionally engineered a La1-xBaxCoO3-δ-(1-a) BaZr0.9Y0.1O2.95 (a = 0.6, 0.7, 0.8 and x = 0.5, 0.6, 0.7) (LBZ) nanocomposite cathodes were prepared by oxidation driven in situ exsolution of a single-phase material deposited on a BaZr0.9Y0.1O2.95 electrolyte. The processing procedure of the cathode was optimized by reducing the number of thermal treatments as the single-phase precursor was deposited directly on the electrolyte. The exsolution and firing of the cathodes occurred in one step. The electrochemical performance of symmetrical cells with the compositionally engineered cathodes was investigated by impedance spectroscopy in controlled atmospheres. The optimized materials processing gave web-like nanostructured cathodes with superior electrochemical performance for all compositions. The area specific resistances obtained were all below 12 Ω·cm2 at 400 °C and below 0.59 Ω·cm2 at 600 °C in 3% moist synthetic air. The resistances of the nominal 0.6 La0.5Ba0.5CoO3-δ-0.4 BaZr0.9Y0.1O2.95 and 0.8 La0.5Ba0.5CoO3-δ-0.2 BaZr0.9Y0.1O2.95 composite cathodes were among the lowest reported for protonic ceramic fuel cells cathodes in symmetrical cell configuration with ASR equal to 4.04 and 4.84 Ω·cm2 at 400 °C, and 0.21 and 0.27 Ω·cm2 at 600 °C, respectively.

Highlights

Protonic ceramic fuel cells (PCFCs) have received considerable attention in the past decades sinceIwahara and Takahashi investigated the ionic conduction in perovskite oxide materials in 1971 [1].One of the main advantages of proton ceramic fuel cells (PCFC) over solid oxide fuel cells (SOFCs) is the lower operating temperature (350–600 ◦ C) because of the lower activation energy for proton conduction compared to oxygen ion conduction [2,3]
Upon lowering of the operating temperature of PCFCs, the cathode has been identified as the performance-limiting component and the search of suitable cathodes has been in focus [8,9,10]
The X-ray diffraction (XRD) patterns of the ex situ exsolved cathodes shown in Figure 3 demonstrate the presence of only two phases for all compositions after calcining the single-phase material at 1100 ◦ C for 2 h in air

Summary

Introduction

Protonic ceramic fuel cells (PCFCs) have received considerable attention in the past decades since. One of the main advantages of PCFCs over solid oxide fuel cells (SOFCs) is the lower operating temperature (350–600 ◦ C) because of the lower activation energy for proton conduction compared to oxygen ion conduction [2,3]. Yttrium-doped barium zirconates and cerates are among the most studied electrolyte candidates because of their high bulk proton conductivity [4,5]. The most studied cathode materials for PCFCs are those commonly used in SOFCs such as La0.8 Sr0.2 MnO3 (LSM) [11,12], La1-x Bax CoO3-δ (LBC) [13,14,15,16], Materials 2019, 12, 3441; doi:10.3390/ma12203441 www.mdpi.com/journal/materials

Methods

Results

Conclusion