Accelerated Stress Testing of Standard Solid Oxide Electrolysis Cells

Abstract

The production of clean and sustainable hydrogen via the commercialization of solid oxide electrochemical cells (SOECs) is currently limited by high cell degradation rates leading to increased costs. In order to achieve the U.S. DOE’s goal of producing hydrogen at $1 kg-1 by 2030, a thorough understanding of the critical degradation mechanisms and their relationship to the SOEC operating conditions is required. To elucidate these mechanisms, accelerated stress testing of standardized Ni-YSZ|YSZ|GDC|LSCF electrolysis cells is being investigated by a National Laboratory Consortium. Initial work focused on the development and standardization of testing procedures including the glass seals, current collectors, and system configurations, leading to improved yield, uniformity, and process control. With a stable baseline, parametric testing of the cell operating conditions, including the temperature, supply voltage/current, and steam concentration, as well as the cycling of these conditions was performed to intentionally initiate and accelerate proven and less understood microstructural evolution mechanisms and modes of mechanical failures. Both ex-situ sample characterization and in-operando experiments are used to understand the evolution of potential degradation mechanisms, including elemental migration and secondary phase formation, void formation, interfacial segregation, and phase decomposition. By understanding the parameters and kinetics of the degradation processes, the Consortium expects to be able to project lifetime performance and cumulative degradation. Ultimately, this work will improve the fabrication and operation of SOECs and enable the production of low-cost hydrogen via water electrolysis.