Operational Aspects of a Perovskite Chromite-Based Fuel Electrode in Solid Oxide Electrolysis Cells (SOEC)

The lanthanum strontium chromite perovskite La0.65Sr0.3Cr0.85Ni0.15O3-delta (L6SSCrN) was implemented as fuel electrode in electrolyte-supported cells (ESC). The electrochemical cell performance in steam electrolysis operation with a fuel gas mixture of 80% H2O-20% H-2 was demonstrated to be comparable to that of Ni-CGO-based state of the art cells at 860 degrees C. At 830, 800, and 770 degrees C, the perovskite fuel electrode exhibited a gain in performance. Lower apparent activation energy barrier values were calculated for the L6SSCrN in symmetrical and full cell configurations, in contrast to Ni-CGO fuel electrodes. A reaction model is proposed, where the water-splitting reaction mainly occurs on the oxygen vacancy sites on the L65SCrN surface and where the exsolved metallic Ni nanoparticles assist the catalytic activity of the electrode with hydrogen spillover and H-2 desorption. We observed a voltage degradation of similar to 48 mV/kh during 1000 h of operation under steam electrolysis conditions at 860 degrees C close to the thermoneutral voltage. van der Pauw conductivity measurements corroborated this degradation with a decrease of the perovskite's p-type conductivity, which appeared to be a diffusion-limited phenomenon. Nevertheless, the lower activation energy of the perovskite-based fuel electrode for solid oxide cells (SOCs) is promising for green hydrogen production via steam electrolysis at a reduced temperature (below 860 degrees C) and without the need of a hydrogen sweep.