Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ composite cathodes for proton ceramic fuel cells

Abstract

Layered Ruddlesden-Popper (RP) lanthanide nickelates, Lnn+1NinO3n+1 (Ln = La, Pr, and Nd; n = 1, 2, and 3) have generated great interest as potential cathodes for proton conducting fuel cells (PCFCs). The high-order phase (n = 3) is especially intriguing, as it possesses the property of a high and metallic-type electronic conductivity that persists to low temperatures. To provide the additional requirement of high ionic conductivity, a composite electrode is here suggested, formed by a combination of La4Ni3O10±δ with the proton conducting phase BaCe0.9Y0.1O3-δ (40 vol%). Electrochemical impedance spectroscopy (EIS) is used to analyse this composite electrode in both wet (pH2O ~ 10-2 atm) and low humidity (pH2O ~ 10-5 atm) conditions in an O2 atmosphere (400-550 °C). An extended analysis that first tests the stability of the impedance data through Kramers-Kronig and Bayesian Hilbert transform relations is outlined, that is subsequently complemented with the distribution function of relaxation times (DFRTs) methodology. In a final step, correction of the impedance data against the short-circuiting contribution from the electrolyte substrate is also performed. This work offers a detailed assessment of the La4Ni3O10±δ-BaCe0.9Y0.1O3-δ composite cathode, while providing a robust analysis methodology for other researchers working on the development of electrodes for PCFCs.