A simple and low-cost alternating current (AC)-based method, without electrolyte correction, is proposed (Electrochemical Impedance Spectroscopy (EIS)-Zero Gap Cell) for the determination of ohmic contribution of diaphragms. The effectiveness of the proposed methodology was evaluated by using a commercial Alkaline Water Electrolysis (AWE) diaphragm (Zirfon^®). Furthermore, the results were compared with two conventional electrochemical methodologies for calculating the separator resistance, based on direct current (DC), and AC measurements, respectively. Compared with the previous techniques, the proposed approach reported more accurate and precise values of resistance for new and aged samples. Compared with the manufacturer reference, the obtained error values for new samples were 0.33%, 5.64%, and 41.7%, respectively for EIS-Zero gap cell, AC and DC methods, confirming the validity and convenience of the proposed technique.

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–yttria-stabilized zirconia (YSZ)/YSZ/ <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>La</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.8</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Sr</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mn>0.98</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>MnO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>(La0.8Sr0.2)0.98MnO3 cell, 2.4 mm in diameter and <mml:math display="inline"><mml:mrow><mml:mn>20</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi></mml:mrow></mml:math>20μm 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 <mml:math display="inline"><mml:mrow><mml:mn>950</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>950°C for the electrolysis operation. At <mml:math display="inline"><mml:mrow><mml:mn>850</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>850°C , the cell withstood current densities of <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi mathvariant="normal">A</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>−1A/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 <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>6</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi mathvariant="normal">A</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>−6A/cm2 at 1.5 V, using <mml:math display="inline"><mml:mrow><mml:mn>70</mml:mn><mml:mi mathvariant="normal">%</mml:mi><mml:mspace width="0.5em"></mml:mspace><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mo>/</mml:mo><mml:mn>15</mml:mn><mml:mi mathvariant="normal">%</mml:mi><mml:mspace width="0.5em"></mml:mspace><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:mn>15</mml:mn><mml:mi mathvariant="normal">%</mml:mi><mml:mspace width="0.5em"></mml:mspace><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>70%H2O/15%H2/15%N2 as a fuel with an area-specific resistance of the cell of <mml:math display="inline"><mml:mrow><mml:mn>0.26</mml:mn><mml:mspace width="0.5em"></mml:mspace><mml:mi>Ω</mml:mi><mml:mspace width="0.5em"></mml:mspace><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>0.26Ωcm2 . The origin of this effect is discussed.