Electrochemical performance of nanocrystalline nickel/gadolinia-doped ceria thin film anodes for solid oxide fuel cells

Nickel oxide/Ce0.8Gd0.2O1.9-x (NiO/CGO) films were deposited by spray pyrolysis and pulsed laser deposition on polished CGO electrolyte pellets. The thicknesses of the as-deposited films were 500-800 nm. The sprayed films showed a homogeneously distributed nano-grain sized microstructure after annealing in air whereas the PLD films exhibited a texture with elongated columnar grains oriented perpendicular to the substrate surface. The electrochemical performance of the Ni/CGO cermet thin film anodes was measured in a symmetrical anode/electrolyte/anode configuration in a single gas atmosphere setup by impedance spectroscopy. The polarization resistance of 60/40 vol.% Ni/CGO spray pyrolysed films decreased with decreasing grain size and was 1.73 and 0.34 Omega(.)cm(2) for grain sizes of 53 and 16 nm, respectively, at 600 degrees C in 3% humidified 1:4 H-2:N-2.The activation energy was 1.45 and 1.44 eV in the temperature range of 400-600 degrees C. The performance of the 49/51 vol.% Ni/CGO PLD cermet film was comparable to the spray pyrolysis films and was 0.68 Omega(.)cm(2) at 600 degrees C with an activation energy of 1.46 eV. The electrochemical performance was similar to state-of-the-art thick film anodes and the Ni/CGO thin film cermets are promising candidates as electrodes in micro solid oxide fuel cells. (C) 2007 Elsevier B.V. All rights reserved.