Abstract
Ni composite anodes for Ca-doped LaNbO4 (LCNO) based proton conducting solid oxide fuel cells were fabricated as screen-printed Ni-LCNO cermets on a dense self-supported LCNO electrolyte and as a semi-symmetrical cell consisting of a ∼ 15 μm thick LCNO electrolyte deposited on a tape-cast Ni-LCNO anode support. The influence of Ni content and sintering temperature on the polarization resistance of the Ni-LCNO interface was investigated. The interface was characterized by electrochemical impedance spectroscopy, and the effects of temperature, pO2 and pH2O on the area specific resistance (ASR) at open circuit were used to determine the rate limiting steps of the hydrogen kinetics of these anodes. The total electrode response is 1.1 Ωcm2 for 40/60 (vol) Ni/LCNO cermet support, at 800°C in wet H2, and the activation energy ∼ 0.5 eV. Three processes were suggested to contribute to the polarization resistance of Ni-LCNO cermet anodes, the most resistive believed to correspond to a charge transfer process at the interface between hydrogen atoms on or in Ni and protons in the electrolyte.