Study Of Synthesis And Properties Of Sr₂FeMoO_6-δ As Hydrogen Electrode Materials For Soec

Based on the roles of the A-site elements and B-site elements in properties of hydrogen electrode with double perovskite structures, combined with the tolerance factor formula, we designed a reasonable hydrogen electrode material which had a structure of Sr2FeMoO6-δ for solid oxide electrolysis cell (SOEC). Sr2FeMoO6-δ powders were synthesized by sol-gel citric acid combustion method. The Sr2FeMoO6-δ hydrogen electrode was formed by suppressing under 10 MPa and sintering at 1300℃.The impact of adding pore-former to the micro pore structure and conductivity of the hydrogen electrode were researched.SOEC cellswere fabricated by an electrolyte supported technique with LSGM as the electrolyte, LSM as the oxygen electrode, and SFM as the hydrogen electrode.The phases and crystal structures of Sr2FeMoO6-δ powders were characterized by XRD, the microstructures of Sr2FeMoO6-δ powders were observed by SEM, and the electrochemical properties of the cells were performed on Sloartron.Sr2FeMoO6-δ powders were synthesized by sol-gel citric acid combustion method.The effects of pH of the sol, calcination atmosphere, and calcination temperature during the synthesis of powders of Sr2FeMoO6-δon the phase structure were investigated. It was found that pure double perovskite Sr2FeMoO6-δ powders were synthesized by calcination at 900-1000℃ for 8 h under 5 vol% H2/Ar atmosphere.The Sr2FeMoO6-δ hydrogen electrode was formed by suppressing under 10 MPa and sintering at 1300℃. The pore structures of the hydrogen electrode were improved by the addition of pore former, and the impact of adding pore-former to the micro pore structure and conductivity of the hydrogen electrode were researched. Finally, the thermal expansion matching between the hydrogen electrode and the electrolyte LSGM was tested. The porosity of the hydrogen electrode could be increased from 12% to 52% and the conductivity of hydrogen electrode was decreased slightly,when starch were added from 0 to 30 wt%.The thermal expansion coefficients of hydrogen electrode and electrolyte LSGM tested may showedthat the hydrogen electrode and electrolyte LSGM had mathed well.Cell 1, cell 2, and cell 3 were fabricated by an electrolyte supported structure with LSGM as the electrolyte, LSM as the oxygen electrode, and SFM with 0,20, and 30 wt% starch as the hydrogen electrode respectively. The electrochemical properties of the cells were performed on Sloartron. Cell 3 had a decreased mechanical of hydrogen electrode, for strach was added at the mount of 30 wt%.The polarization resistance of cell 1 reduced from8.11 Ω/cm2to 1.2 Ω/cm2and the power density of cell 1 improved from0.024 W/cm2 to 0.063 W/cm2, while temperature increased from 700℃ to 850℃.The polarization resistanceof cell 2 was 1.14 Ω/cm2 and the power densities of cell 2 was 0.077 W/cm2 at 850℃. Cell 2 was better than cell 1 both in the polarization resistance and in the power densities, for the micro pore structures of hydrogen electrode were improved by adding an appropriate amount of starch.