Barium carbonate as a synergistic catalyst for the H2O/CO2 reduction reaction at Ni–yttria stabilized zirconia cathodes for solid oxide electrolysis cells

Abstract

BaCO₃ is primarily demonstrated as an excellent synergistic catalyst for efficient electro-reduction of H₂O/CO₂ to H₂/CO at the state-of-the-art Ni–YSZ (yttria-stabilized zirconia) cathodes for solid oxide electrolysis cells (SOECs) with YSZ electrolytes and strontium doped lanthanum manganite oxygen electrodes. BaCO₃ nanoparticles, which are deposited onto porous Ni–YSZ using the infiltration process, can significantly improve the SOEC performance such as increasing the electrode interfacial polarization conductivity over 50% and promoting the electrolysis current density by a factor of up to 2 for the electrolysis of H₂O to H₂, CO₂ to CO, and co-electrolysis of H₂O–CO₂ to H₂–CO at 800 °C. In addition, it seems that BaCO₃ can improve the SOEC durability for the co-electrolysis of H₂O–CO₂. The improvement is associated with an enhanced surface charge transfer process, which is the rate-determining step for the reduction reaction, as shown by analyzing the AC impedance spectrum measured with a three-electrode configuration. The highest improvement is achieved with CO₂ reduction possibly due to the additional enhancement in the adsorption/dissociation process by BaCO₃ as revealed with temperature programmed CO₂ desorption analysis.