Fabrication and Performance Evaluation of Solid Oxide Electrolysis Cell Integrated with Metal Interconnect by Joining Process

Metal-supported solid oxide electrolysis cell integrated with metal interconnect by joining process (so-called, with fuel electrode(cathode)-supported electrolysis cell) was fabricated and its electrical performance are investigated under both operation mode of fuel cell(hydrogen) and co-electrolysis(steam and CO₂) mode at the intermediate temperature of 750 ^oC~850 ^oC. The fuel(or steam) electrode layers are prepared using NiO and YSZ(8 mol% Y₂O₃-doped ZrO₂) at the ratio of 1:1. In order to obtain pores in the cathode, graphite powders of 24 volume % with average particle size of 44 mm are added. In the case of a metal-supported solid oxide  electrolysis cell(SOEC) with heat-treated cathode support, 10 mol % Sm₂O₃-doped CeO₂ (SDC) paste is screen-printed on the surface of YSZ and subsequently (La_0.6Sr_0.4) (Co_0.2Fe_0.8)O₃ (LSCF) paste mixed with SDC at 1:1 weight ratio as anode(air electrode) is screen-printed on the SDC layer and heat-treated for desirable adhesion. The single electrolysis cell performances are compared by analyzing AC impedance spectra and product gas composition by GC(gas chromatography)of metal-supported electrolysis cell integrated with metal interconnect and cathode-supported electrolysis cell, and the current-voltage characteristics and cross-sectional microstructure of cathode-supported cell integrated with metal interconnect are tested. The stable long-term performance with co-electrolysis of carbon dioxide (CO₂)and steam(H₂O) is shown for about 800 h at 800 ^oC under the constant current density of 300 mA/cm², 600 mA/cm², 800 mA/cm², and 1000 mA/cm². In the fuel cell mode operation of metal-supported SOEC cell, the maximum power density of 0.8W/cm² is indicated with hydrogen fuel. The microstructures are analyzed using optical microscope for observing a diffusion of metal ions at the cathode, adhesion layer and metal support(ferritic stainless steel, STS430) with EDAX analysis. In the present work, we have investigated the performance and microstructures of metal-supported SOEC for the co-electrolysis of CO₂ and H₂O steam. The exemplary works with AC impedance and the composition of product gas are analyzed in the operation of metal-supported co-electrolysis cell.