SOFC-SOEC Characteristics of an Intermediate-temperature Micro-tubular Ceramic Reactor Using Ag for Current Collecting

Abstract

Ni-based electrode-supported cells with a Sc₂O₃-stabilized ZrO₂ electrolyte have been evaluated as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) in intermediate-temperature operation. Using a Ag current collector, a power density of 1.68 W cm⁻² at 2.87 A cm⁻² and an electrolysis voltage of 1.42 V at 0.57 A cm⁻² were obtained at 650°C. The current efficiency in steam electrolysis was almost 100%. This suggests that the high performance is related to decreases in current collector resistance and polarization of the air electrode, due to the formation of Ag current collecting paths on the air electrode. During a 450 h durability measurement in SOEC mode, a degradation rate of 0.056 mV h⁻¹ was observed. Impedance measurements showed the polarization of the steam electrode increased, while the polarization of the air electrode and ohmic resistance showed no change, after the long-term SOEC operation.