Co-electrolysis of CO2 and H2O on LaFe0.6Co0.4O3 promoted La0.75Sr0.25Cr0.5Mn0.5O3/YSZ electrode in solid oxide electrolysis cell

Abstract

La0.75Sr0.25Cr0.5Mn0.5O3-δ/ZrO2-8 mol% Y2O3 (LSCM/YSZ) was used as the fuel electrode of solid oxide electrolyzer cell and its performance during steam electrolysis and CO2/H2O co-electrolysis at 850 °C was analyzed. Results from polarization and electrochemical impedance spectroscopy data showed that the electrode exhibits better performance when the steam and CO2 concentration in the carrier gas were 20% and 9%, respectively, rather than when the carrier gas only had 20% steam. In order to further enhance the performance of the electrode, LaFe0.6Co0.4O3 nanoparticles were introduced onto the LSCM/YSZ scaffold by means of infiltration technique, with different concentration of LaFe0.6Co0.4O3 precursors. The field emission scanning electron microscopy images and Energy-dispersive X-ray spectroscopy confirmed the formation of nanoparticles of catalytic materials in the fuel electrode. Polarization and impedance data verified the promotion of the electrochemical behavior of LSCM/YSZ fuel electrode, during both steam and co-electrolysis; for example, by using a 0.6 mol L−1 LaFe0.6Co0.4O3 precursor for infiltration, 80% and 75% decrease in the polarization resistance occurred at steam and co-electrolysis modes, respectively at 850 °C and under potential of −1 V. Moreover, analysis of distribution of relaxation times of impedance data showed that three distinct processes occurred during steam and co-electrolysis on the infiltrated electrodes, which were related to charge transfer process at high frequency region, gas diffusion at medium frequency region and reactant gas adsorption and surface diffusion of activated species from gas dissociation to triple phase boundaries and ionic diffusion at low frequency region.