Steam Electrolysis Using a Microtubular Solid Oxide Fuel Cell

Reversible operation of a microtubular solid oxide fuel cell SOFC with high electrochemical efficiency is reported. These devices can ideally produce hydrogen from electricity and steam solid oxide electrolyser SOE and then use the stored hydrogen to generate electricity and heat SOFC , acting as a storage device for the electrical energy. A fuel-electrode-supported Ni–yttriastabilized zirconia YSZ /YSZ/ La0.8Sr0.2 0.98MnO3 cell, 2.4 mm in diameter and 20 m of electrolyte thickness, was evaluated in an electrolysis mode as a function of the steam concentration supplied to the Ni/YSZ electrode. A good cell performance was obtained at temperatures as high as 950°C for the electrolysis operation. At 850°C, the cell withstood current densities of −1 A/cm2 at 1.3 V with steam utilization of 16.5%. The production of hydrogen in the electrolyzer was tested by mass spectrometry. Their performance, especially in the SOE mode, is very promising for high temperature electrolysis applications. Voltage–current curves present an S-shaped nonlinear behavior in the electrolysis mode with a tendency to saturate at high current density values. The cell could sustain current densities as high as −6 A/cm2 at 1.5 V, using 70% H2O/15% H2/15% N2 as a fuel with an area-specific resistance of the cell of 0.26 cm2. The origin of this effect is discussed. © 2010 The Electrochemical Society. DOI: 10.1149/1.3332832 All rights reserved.