Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ Composite Cathodes for Proton Ceramic Fuel Cells

Layered Ruddlesden-Popper (RP) lanthanide nickelates, Ln(n+1)Ni(n)O(3n+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 +/-delta with the proton conducting phase BaCe0.9Y0.1O3-delta (40 vol%). Electrochemical impedance spectroscopy (EIS) is used to analyse this composite electrode in both wet (p(H2O) similar to 10(-2) atm) and low humidity (p(H2O) similar to 10(-5) atm) conditions in an O-2 atmosphere (400-550 degrees 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 +/-delta-BaCe0.9Y0.1O3-delta composite cathode, while providing a robust analysis methodology for other researchers working on the development of electrodes for PCFCs.