Investigation of Ce0.9Gd0.1O2-δ dispersed Sm1.5Sr0.5NiO4+δ: Cathode for intermediate temperature solid oxide fuel cell applications

Dispersion of nanocrystalline (94-350 nm) Ce0.9Gd0.1O2-delta in superfine (260-312 nm) Sm1.5Sr0.5NiO4+delta using modified precipitation technique is established using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Presence of Ce0.9Gd0.1O2-delta grains inhibits grain growth of Sm1.5Sr0.5NiO4+delta, which provides morphological stability (up to 1100 degrees C). Ce0.9Gd0.1O2-delta 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 Omega cm(2) at 700 degrees C) for 70Sm(1.5)Sr(0.5)NiO(4+delta):30Ce(0.9)Gd(0.1)O(2-delta) 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 Ce0.9Gd0.1O2-delta 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 O2- diffusion. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.