Electrochemical Performance and Degradation Analysis of an SOFC Short Stack for Operation of more than 100,000 Hours

摘要

From August 2007 to January 2019, a two-layer solid oxide fuel cell (SOFC) short stack in a planer design with zirconia based, anode-supported cells (ASC) and ITM interconnectors (with 26% chrome content) was tested with hydrogen and compressed air at a furnace temperature of 700°C for more than 100,000 hours, of which ～93,000 were in constant current mode, with a current density of 0.5 Acm~(-2) and fuel utilization of 40%. The calculated voltage degradation rate decreased slowly from ～8.0 mV/kh (～1.0%/kh) for the first 40,000 h to ～1.4 mV/kh (～0.2%/kh) for the rest of the operation under load, indicating different dominating degradation mechanisms. The average voltage and area-specific resistance (ASR) degradation rates for the complete operating period under electrical load were 0.5%/kh and 2.5%/kh, respectively. Electrochemical impedance spectroscopy (EIS) was also implemented at the end of the testing period for the purpose of electrochemical characterization and a degradation analysis. A comprehensive post-mortem analysis of the stack is currently in preparation. In this study, the performance and degradation behaviour of the stack and cells are analysed and discussed based on the electrochemical measurements.