Electrochemical and Dynamic Characterization of a 6-Cell Solid Oxide Cells Stack in Steam Electrolysis and Steam and Carbon Dioxide Co-Electrolysis

摘要

High temperature steam electrolysis and co-electrolysis of steam and carbon dioxide for hydrogen and syngas production is gaining attention for its potential to play a key role in the production of renewable fuels and for long-term energy storage. Unlocking a longer lifetime and lower costs for these systems is required if they are to be widely deployed. In this work, we consider a 6-cell Solid Oxide Cell (SOC) short-stack, manufactured by SOLID power S.p.a. (Italy), that has been installed and tested at UC Irvine. The short-stack is installed in a test bench that maintains the operating temperature in a controlled range of 650-850°C, via an electric furnace. The cells are characterized by an 8 mol% Y_2O_3 stabilized Zirconia (YSZ) electrolyte (8 ± 2 μm) supported on a conventional porous Ni/YSZ anode electrode (240 ± 20 μm). The cathode electrode is comprised of a composite of metallic perovskite Sr-doped LaMnO_3 (LSM) and oxide-ion electrolyte YSZ (40 ± 10 μm). The active area of each cell is 80 cm~2. The aim of the study is the experimental characterization of the short-stack via electrochemical and dynamic techniques to: i) characterize stack performance in steady-state; ii) investigate single cell degradation and interdependencies between adjacent cell operating conditions to determine stack degradation; and iii) determine characteristic time responses of thermal, fluid-dynamic and electrochemical phenomena. The experiments are conducted for both steam electrolysis and co-electrolysis of steam and carbon dioxide. The experimental electrochemical methods employed include chronopotentiometry, electrochemical impedance spectroscopy and current interrupt. Moreover, fluid-dynamic step response and thermal ramp dynamic response of the stack are evaluated to achieve a better understanding of the effect of an operating control system on local fuel starvation and local temperature hot spot regions, which are possible contributors to increased degradation.