Theoretical Understanding of Effects of Operating Modes on the Performance Durability of Solid Oxide Cells: A Comparison between Potentiostatic and Galvanostatic Operations

Abstract

In solid oxide cells (SOCs), the choice of operating mode, specifically between galvanostatic and potentiostatic, has negligible impact when the properties of the cell components remain unchanged, leading to stable cell performance without degradation. However, when there are changes in the cell properties, the chosen operating mode becomes a critical factor influencing the performance and durability of SOCs. The aim of this paper is to investigate the effects of these operating modes on the changing properties of SOC components and, consequently, on their performance durability. To achieve this, we utilize nonequilibrium thermodynamic analysis, a method crucial for comprehending the degradation processes occurring within these electrochemical devices. Key findings include:
 In cases where oxygen electrode (OE) degradation is accelerated by the higher partial pressure of oxygen pO2, operating under constant voltage electrolysis can prevent high pO2 at the OE|electrolyte (OE|EL) interface. 
 Conversely, if OE degradation occurs more rapidly under lower p_(O_2 ), constant current electrolysis is more effective in sustaining high pO2 at the OE|EL interface during degradation.
 For fuel electrode (FE) degradation favored by higher pO2, constant current electrolysis helps maintain low pO2 at the FE|EL interface. When FE degradation is expedited by lower pO2, potentiostatic electrolysis can avert it.