Microstructure and reactivity effects on the performance of Nd2NiO4+δ oxygen electrode on Ce0.9Gd0.1O1.95 electrolyte

Abstract

The effect of electrode microstructure on the electrochemical behavior of symmetricalNd2NiO4þd/Ce0.9Gd0.1O1.95/Nd2NiO4þd cells was studied by Electrochemical ImpedanceSpectroscopy as a function of temperature (500 < T < 750 C) and oxygen partial pressure(104 < pO2 < 1 atm). Nd2NiO4þd powders were synthesized by Solid State Reaction, HMTAand Citrates. The samples observed by Scanning Electron Microscopy presented verydifferent microstructures. Three characteristic processes were distinguished at high,medium and low frequency. High frequency contribution was attributed to oxygen iontransfer electrode/electrolyte. Medium frequency contribution was related to oxygeninterstitial bulk diffusion and oxygen incorporation in those cases in which the surface ofsmall particles is affected by chemical reactivity with the electrolyte. The low frequencycontribution was attributed to dissociative adsorption for electrodes with small particlesizes and high porosity, and a co-limited process of adsorption and gas diffusion for anelectrode with dense microstructure and low porosity.