Large area solid oxide fuel cells with room temperature sputtered barrier layers: Role of the layer thickness and uniformity in the enhancement of the electrochemical performances and durability

We investigate the effects of the layer thickness and uniformity in solid oxide fuel cells with Gd0.1Ce0.9O1.95-δ buffer layers deposited by room temperature sputtering followed by in air annealing. Buffer layers with different thickness (in the range 200–400 nm) have been deposited using two different sputtering configurations resulting in different thickness uniformity and coverage of the Gd0.1Ce0.9O1.95-δ thin layers. By comparing the electrochemical performances at different temperatures of the cells with sputtered and screen printed buffer layers assembled in the same short stack, we have observed improvements, particularly at lower temperatures, of all the analysed properties (current density vs. voltage curves, Area Specific Resistance, Electrochemical Impedance Spectroscopy) in the case of the cells with sputtered buffer layers, with those having better thickness uniformity always showing the higher and more regular values. Percentage voltage changes of about +8% along with polarization resistance percentage reduction around −10% have been observed at 650 °C. Durability test at 750 °C performed over about 3000 h on the cell with 300 nm thick buffer layer having larger thickness uniformity, has shown percentage voltage changes more than halved respect to those observed for cells with screen printed buffer layers. The obtained results address the importance of the thickness uniformity control when fabricating thin buffer layers of few hundreds of nanometers on anode/electrolyte half-cells with surface roughness of the same order of magnitude.