Influence of the oxygen electrode and inter-diffusion barrier on the degradation of solid oxide electrolysis cells

Two Solid Oxide Electrolysis Cells (SOECs) with different oxygen electrodes have been tested in galvanostatic tests carried out at -1.5 Acm(-2) and 800 degrees C converting 60% of a 50:50% mixture of H2O and CO2 (co-electrolysis). One of the cells had an LSM:YSZ oxygen electrode. The other had an CGO inter-diffusion barrier sandwiched between the YSZ electrolyte and an LSCF:CGO oxygen electrode. Impedance Spectroscopy was used during the tests to diagnose the change in electrochemical response of the different components of the SOECs. The results showed a significantly lower degradation rate for the cell with an LSCF:CGO oxygen electrode. This was attributed to three different effects: (1) The LSCF electrode was found to be more stable than its LSM:YSZ based counterpart. (2) The crack propagation in the YSZ electrolyte was less severe in the cell with an LSCF electrode. (3) The Ni:YSZ degradation was less severe in the cell with an LSCF electrode. We hypothesize further that (2) is an effect of the CGO inter-diffusion layer and that (3) is an indirect effect of (2). (C) 2012 Elsevier BM. All rights reserved.