Impregnation of Nanoparticle Scaffolds for Syngas-Fed Solid Oxide Fuel Cell Anodes

We will present a strategy for fabrication of solid oxide fuel cell anodes with improved porosity and lower sintering temperatures by impregnation of nanoparticle-containing porous scaffolds of ceria-gadolinia (CGO). The CGO scaffolds are fabricated using a screen-printed ink containing nanoparticles and commercial particles of CGO and polymeric pore formers. The porosity and structure of these scaffolds is characterised by scanning electron microscopy and in situ ultra-small angle X-ray scattering, showing that incorporation of nanoparticles can increase the porosity by allowing a reduction in sintering temperature from 1300 to 1000 °C. The scaffolds are then impregnated with nickel nitrates to produce symmetrical cell and button cells. The electrochemical characterisation of the symmetrical cells shows that the cells sintered at 1000 °C possess similar electrode polarisation compared to those sintered at 1300 °C of around 10 Ωcm² at 500 °C under 10% hydrogen despite being sintered at 300 °C lower temperature. The low frequency response in the impedance spectra usually assigned to diffusion is smaller in the low temperature calcined cells while the high frequency response is larger. Button cell testing showed that reducing the sintering temperature produced cells which perform better at 700 °C (and below) in hydrogen, and performed better at all temperatures using syngas, with power densities of up to 0.15 W cm-2 at 800 °C, while a further improvement in performance could be obtained by impregnating with a mixture of nickel and copper nitrate. This approach has the potential to allow the use of a wider range of nanomaterials, giving a finer control over microstructure.