Hydrogen Oxidation Kinetics and Performance of Ni-LaNbO4 Cermet Anodes for Proton Conducting SOFCs.

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. [ABSTRACT FROM AUTHOR]