Releasing metal catalysts via phase transition: (NiO)_0.05-(SrTi_0.8Nb_0.2O₃)_0.95 as a redox stable anode material for solid oxide fuel cells

Donor-doped perovskite-type SrTiO₃ experiences stoichiometric changes at high temperatures in different P_o2 involving the formation of Sr or Tirich impurities. NiO is incorporated into the stoichiometric strontium titanate, SrTi_0.8Nb_0.2O_3-δ (STN), to form an A-site deficient perovskite material, (NiO)_0.05-(SrTi_0.8Nb_0.2O₃)_0.95 (Ni-STN), for balancing the phase transition. Metallic Ni nanoparticles can be released upon reduction instead of forming undesired secondary phases. This material design introduces a simple catalytic modification method with good compositional control of the ceramic backbones, by which transport property and durability of solid oxide fuel cell anodes are largely determined. Using Ni-STN as anodes for solid oxide fuel cells, enhanced catalytic activity and remarkable stability in redox cycling have been achieved. Electrolytesupported cells with the cell configuration of Ni-STN-SDC anode, La_0.8Sr_0.2Ga_0.87Mg_0.13O₃ (LSGM) electrolyte, and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode produce peak power densities of 612, 794, and 922 mW cm^-2 at 800, 850, and 900°C, respectively, using H₂ as the fuel and air as the oxidant. Minor degradation in fuel cell performance resulted from redox cycling can be recovered upon operating the fuel cells in H₂. Such property makes Ni- STN a promising regenerative anode candidate for solid oxide fuel cells. (Graph Presented).