Investigation of Ce0.9Gd0.1O2-δ dispersed Sm1.5Sr0.5NiO4+δ: Cathode for intermediate temperature solid oxide fuel cell applications. (6th January 2021) - Khandale, A.P.
Abstract: Dispersion of nanocrystalline (94–350 nm) Ce0.9 Gd0.1 O2-δ in superfine (260–312 nm) Sm1.5 Sr0.5 NiO4+δ using modified precipitation technique is established using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Presence of Ce0.9 Gd0.1 O2-δ grains inhibits grain growth of Sm1.5 Sr0.5 NiO4+δ, which provides morphological stability (up to 1100 °C). Ce0.9 Gd0.1 O2-δ concentration dependent behaviours of ionic conductivity, surface exchange rate and electrode polarization resistance ( R p ) of composites (determined using electrochemical impedance spectroscopy) are comprehended using percolation model. Three oxygen reduction reaction mechanisms are considered to understand electrochemical performance. Minimum R p (0.81 Ω cm 2 at 700 °C) for 70Sm1.5 Sr0.5 NiO4+δ :30Ce0.9 Gd0.1 O2-δ is correlated to percolation threshold (optimum (i) electrochemically active sites (ii) oxygen reduction reaction kinetics, (iii) O 2- conductivity and (iv) charge transfer rate). Nano crystallite size of Ce0.9 Gd0.1 O2-δ is crucial for enhancement in electrochemical performance. Oxygen partial pressure dependent electrochemical impedance spectroscopy studies reveal dominance of coexisting non-charge transfer oxygen adsorption/desorption and bulk O 2- diffusion. Graphical abstract: Image 1 Highlights: Investigated composite cathodes prepared using modified precipitation technique. Percolation model invoked to understand electrochemical response of composites. Ce0.9 Gd0.1 O2- δ inhibits Sm1.5 Sr0.5 NiO4+ δ grain growth. σ ion and O2 surface exchange rate ( k O ) evaluated using EIS data and interpreted. Three different ORR mechanisms are suggested.