Post-test characterization of a solid oxide fuel cell after more than 10 years of stack testing
Norbert H. Menzler, Doris Sebold, Yoo Jung Sohn, Sebastian Zischke
Abstract
A short stack composed of two layers with anode-supported SOFCs was operated galvanostatically for 100,000 h. The operating temperature was 700 °C, the current density 0.5 A cm−2 and humidified hydrogen and ambient air were used as gases. Over time, the degradation slope varied and the overall voltage degradation finally amounted to 0.5% per 1000 h. After dismantling the stack all relevant components were post-test analyzed. Here we report on our cell findings. The Ni/8YSZ support, the 8YSZ electrolyte and the perovskitic cathode contact layer appear nearly intact after 11 years. Most of the observed changes/interactions can be attributed to the anode (Ni/8YSZ), the barrier layer (GDC) and the cathode (LSCF). Close to the barrier layer, the cathode is fragmented, elementally disintegrated and Cr poisoning was detected. The GDC also shows some fragmentation close to the cathode and some interaction with chromium. Elements from both layers, the cathode and the barrier, interdiffuse to a certain amount. The fuel electrode displays some foreign phase formation consisting of manganese and aluminium. Additionally, and this was found for the first time in a solid oxide fuel cell stack, Ni enrichment in the anode was observed.