Insight into the Electrochemical Processes of the Titanate Electrode with in Situ Ni Exsolution for Solid Oxide Cells

Perovskite-type titanate with in situ exsolution is one promising electrode material for solid oxide cells because of its distinct properties to resist redox operation, carbon deposition, and sulfur contamination. However, lacking a mechanistic understanding of the electrochemical processes significantly hinders further optimization of the exsolved titanate electrode for its practical application. In this study, the in situ growth of Ni nanoparticles and its effect on the electrode processes was investigated on the Ni-doped Sr0.94Ti0.9Nb0.1O3-delta electrode for solid oxide cells. Four individual electrode processes were distinguished and determined by equivalent circuit modeling and distribution of relaxation times analysis of the electrochemical impedance data. Correlated with in situ and ex situ characterizations, it is revealed that the electrochemical processes were dominated by the surface reaction process, which was substantially activated by the exsolution of Ni nanoparticles by providing catalytically active sites and accelerating the rate of H-2/H2O dissociative adsorption.