Non-stoichiometric layered cobaltite performing as a highly active catalytic electrode for solid oxide cells

Solid oxide cells (SOCs) have attracted wide attention as highly efficient energy transfer devices between hydrogen and electricity. A Ca(OH) 2 nanoparticles modified Ca 3 Co 4 O 9+δ (CCO) hetero-structured oxygen electrode is obtained from the non-stoichiometric Ca 3.5 Co 4 O 9+δ (C35CO) in this work. By annealing at 850 °C in air, excessive Ca cations in C35CO are exsolved from oxide lattice to maintain the thermodynamically stable and forms homogeneously dispersed CaO nanoparticles on the surface. CaO is subsequently converted into Ca(OH) 2 by hydration reaction. The novel C35CO electrode contributes to greatly improved electrochemical kinetics with a polarization resistance of 0.07 Ω cm 2 at 800 °C, surpassing many results of the reported CCO catalysts. Such enhancement is based on the promoted oxygen vacancy concentration that significantly boosts the chemical adsorption and surface reaction kinetics of O 2 . This work validates that the highly active and durable oxygen electrode of non-stoichiometric layered cobaltite is promising in applications of ceramic fuel cells and electrolysis cells.