Reversible operation of tubular type solid oxide fuel cells using LaGaO₃ electrolyte porous layer on dense film prepared by dip-coating method

A micro-tubular type solid oxide fuel cell was prepared by using a NiO-YSZ anode support tube and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) electrolyte film which was prepared by dip-coating and co-sintering process. Since a large electric resistance loss (IR loss) was observed at the cathode side, LSGMporous layerwas inserted between electrolyte and cathode resulting inmuch increased power density. The prepared cell using Sm_0.5Sr_0.5CoO_3-δ (SSC) cathode layer on the porous LSGM layer exhibited almost theoretical open circuit voltage (OCV) of ca.1.1 V and a maximum power density (MPD) of ca. 0.782 and 0.1 W/cm² at 973 and 773 K, respectively, in fuel cell operation. The increased MPD by an inserting the porous LSGM layer can be explained by an increase in mechanical contact and cathodic reaction area. In addition, the electrolysis operation of the prepared LSGM tubular cell with an atmosphere of 20% steam and 30% H₂ was examined and it was found that the prepared tubular type LSGM cell showed a reasonably large electrolysis current. The current density of the cell with and without LSGM porous layer was 1.47 and 1.11 A/cm² at the applied potential of 1.5 V, 973 K. As a result, it was found that the prepared LSGM electrolyte cell can be used as a reversible type cell with reasonable power density in SOFC operation and high H2 formation rate in electrolysis operation by deposition of an LSGM porous layer on the Air electrode side.