Performance Characterization of Solid-Oxide Electrolysis Cells for Hydrogen Production

An experimental study has been completed to assess the hydrogen-production performance of single solid-oxide electrolysis cells operating over a temperature range of 800 to 900°C. The experiments were performed over a range of steam inlet partial pressures (2.3 – 12.2 kPa), carrier gas flow rates (50–200 sccm), and current densities (−0.75 to 0.25 A/cm²) using single electrolyte-supported button cells of scandia-stabilized zirconia. Steam consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation. Cell operating potentials and cell current were varied using a programmable power supply. Values of area-specific resistance and hydrogen production rate are presented as a function of current density. Cell performance is shown to be continuous from the fuel-cell mode to the electrolysis mode of operation. The effects of steam starvation and thermal cycling on cell performance parameters are discussed. Laboratory capabilities are currently being expanded to allow for testing and characterization of multiple-cell electrolysis stacks. Some fundamental differences between the fuel-cell and electrolysis modes of operation have been summarized.