Long‐Term Behavior of a Solid Oxide Electrolyzer (SOEC) Stack▴

Abstract

The successful market introduction of the solid oxide fuel/ electrolysis cell technology for power-togas applications requires the reduction of the degradation rates and the better understanding of the degradation mechanisms of the stacks. Therefore, the paper reports and compares the long-term behavior of a solid oxide cell stack in electrolysis and reversible fuel cell/electrolysis operation. The 30-cell stack with electrolyte supported cells was supplied by Sunfire GmbH (Dresden/Germany) in the German funded RSOC Project. The stack was operated for 3,370 h in electrolysis and afterwards for 2,500 h in reversible fuel cell/electrolysis mode, each at 70% gas conversion. In the beginning of the test, the stack showed high gas tightness, good performances and high efficiencies in both SOEC and SOFC operations. During 3,370 h of SOEC operation a low degradation of +0.5%/ 1,000 h was measured. During 2,500 h of reversible fuel cell/ electrolysis cycling, the gas tightness of the stack slightly decreased, which led to a temperature increase, and higher degradation rates were observed. The increase of the ohmic resistance contributed mostly to the degradation. Optimized operating conditions for reversible cycling and increasing the purity of the supplied water are foreseen in order to minimize stack degradation in reversible operation.

Advancing Electrode Properties through Functionalization for Solid Oxide Cells Application: A Review

“…Fused aggregate network structured three dimensional NiO have been prepared by flame pyrolysis method in order to form an electronically conducting additional network into the CL (Ni−Co into SDC) and CCL (Ni‐YSZ) by Uchida et al. They have shown that presence of additional 10 vol% of 3D NiO resulting an accelerated electrochemical performance with reduced rate of degradation [167] …”

“…The cell (4x4 cm 2 ) with such engineered fuel electrode exhibited excellent performance at 750 °C and showed long‐term durability at high C.D of 1 A.cm −2 for 900 h. No significant change in the cell microstructure with low R OER of 0.012 Ω.cm 2 is reported after 900 h. This proved that CGO‐coating effectively mitigate the microstructural deterioration of Ni‐YSZ cermet for long‐term SOC‐operation. A study on long‐term SOC‐stack test has been reported by DLR comprising of 30 electrolyte supported cells of configuration Ni‐GDC/YSZ/GDC/LSCF provided by SUNFIRE with Ni‐GDC fuel electrode [167] …”

Performance and Durability of Reversible Solid Oxide Cells with Nano-electrocatalysts Infiltrated Electrodes

“…In the past decade, different electrode materials, microstructure of the electrodes, and operating conditions have been studied. [10][11][12][13] Lang et al 11 reported the long-term durability performance of an SOC stack consisting of 30 electrolytesupported cells (ESCs) supplied by Sunfire. The stack was operated for 3370 h in constant SOEC mode at 820°C followed by 2500 h in reversible SOFC/SOEC mode with the steam utilization of 70%.…”

Interface Evolution of Solid Oxide Cells between the Electrode and the Interconnect Rib Induced with Applied Current

“…[ 3 ] For example, Yan et al [ 4 ] used a four‐cell solid oxide electrolysis cells (SOEC) with two different electrode materials for nearly 1000 h electrolysis with a constant current density of −500 mA cm −2 at 800 °C; the average degradation rate for their cell stack was 15.8% kh −1 , which is due to increasing porosity at the fuel electrode. Lang et al [ 5 ] tested a 30‐cell SOEC stack for 3370 h at 820 °C with a constant current density of −520 mA cm −2 , with an average degradation rate of 0.5% kh −1 owing to the gas tightness of the stack slightly decreased. Takuto [ 6 ] studied the durability of a single SOEC with a current density of −300 mA cm −2 at 973 K; the degradation rate during the SOEC operation was 4.8% kh −1 after 5000 h, which was concluded that the S poisoning of the oxygen electrode was the primary reason for the high degree of degradation observed.…”