In order to understand the dynamics of redox processes and to design the Ni-GDC electrodes with optimal microstructure the information related to simultaneous structural and electrochemical changes during SOFC operation would be very useful. In this work a novel approach for simultaneous monitoring of electrochemical (EC) properties and crystallographic structure in operating SOFC i.e. in operando SOFC EC-XRD measurement cell has been proposed and applied to understand the redox dynamics in Ni-GDC anode.
The impact of polarization on structure of Ce0.9 Gd0.1O2-d (GDC) in Ni-GDC cermet anode as well as impact of NiO ⇌ Ni redox cycles on the size and structure of Ni particles and electrical contact between particles has been studied with the in house developed in operando EC-HTXRD cell. Changes in the lattice parameters of Ni and GDC as well as electrochemical properties of Pt|Ni-GDC|ScCeSZ|GDC|LSC were monitored as a function of temperature (T), electrode polarization (E) and oxygen partial pressure (pO2). Influence of temperature, pO2 and polarization on GDC lattice parameters was observed. O2- current through the membrane lead to decrease of unit cell volume of GDC lattice. The observed change in lattice parameter upon polarization change from open circuit voltage (OCV) (depending on temperature, about 1.1 V) to 0.9V (potential of 3-electrode setup) was equal to 50 degree temperature change.
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