Direct electrolysis of CO2 in solid oxide cells supported on ceramic fuel electrodes with straight open pores and coated catalysts

This study was to investigate direct electrolysis of CO2 via solid oxide cells with thin Y0.16Zr0.84O1.92 (YSZ) electrolytes and (La0.8Sr0.2)(0.)95MnO3-delta (LSM)-YSZ air electrodes supported on La0.8Sr0.2Cr0.5Fe0.5O3-delta (LSCrF)YSZ fuel electrodes. The fuel electrode with straight open pores was prepared using the phase-inversion tape casting method, modified with nano-scaled Sr(2)FeLsMn(0)(.5)O(6-delta) (SFM) catalysts using the impregnation method. Substantially larger maximum power densities were observed in the fuel cell mode for single cells with the SFM catalysts than without, e.g., 423 vs. 51 mW.cm(-2) at 800 degrees C. Impedance analysis showed an order magnitude drop in the pure ohmic resistances and the interfacial polarization resistances in the presence of electronically conductive and catalytically active SFM nanoparticulates. Electrolysis measurements indicated that these nanoscaled SFM catalysts also helped to promote CO2 reduction reactions. The electrolysis current densities at 1.5 V were 0.48, 0.64 and 1.02 A.cm(-2) for the SFM-infiltrated cells at 700, 750, 800 degrees C, respectively. In contrast, the blank cells displayed much smaller current densities of 0.22, 0.35 and 0.41 A.cm(-2) under the similar conditions. Apparently, the modification of the LSCrF-YSZ electrode with SFM nanoparticulates provided extended electrochemically active sites with sufficient interconnected paths to transfer electrons and oxygen ions, which led to a significant increase in the electrochemical performance. The reduced polarization resistance and high current density show that the nano-scaled SFM-modified LSCrF-YSZ fuel electrode is highly effective for pure CO2 electrolysis without using the safe gas.