(459d) High-Temperature Co-Electrolysis of CO2 and H2o on Lanthanum Ferrite-Type Perovskite Oxide Cathodes

High-temperature electrolysis of water and co-electrolysis of water and carbon dioxide are promising ways to produce clean hydrogen and syngas (a mixture of hydrogen and carbon monoxide) with pure oxygen being the only by-product. The co-electrolysis of H₂O and CO₂ also provides a potential CO₂ mitigation route by converting this greenhouse gas into syngas, an important chemical building block, which can be turned into valuable chemicals by Fischer-Tropsch synthesis. In this study, a high-temperature (700-850°C) solid electrolysis cell (SOEC) is used to co-electrolyze H₂O and CO₂ into syngas.

The SOEC employed in the present work consists of an yttria-stabilized zirconia (YSZ) solid oxide oxygen ion conducting electrolyte, sandwiched between two electrode layers. The counter electrode (anode) is a commercially available mixture of La_0.8Sr_0.2MnO₃ and YSZ (LSM-YSZ), whereas the working electrode (cathode) consists of an in-house developed lanthanum ferrite-type perovskite oxide. H₂O and CO₂ get electrolyzed at the cathode producing O^2- ions which travel through the YSZ electrolyte to the anode where they combine to form molecular oxygen.

The B-site doped lanthanum ferrite perovskite materials used in this study as the working electrode were synthesized via EDTA-citric acid complexation method. The synthesized materials were characterized ex-situ, in-situ and operando using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), Raman spectroscopy, transmission electron microscopy and four probe DC van der Paw techniques to investigate their morphology, bulk and surface structure and electrical conductivity and the changes in these properties during the electrochemical reaction under bias. The electrocatalytic activity tests showed that the synthesized perovskites are highly active in electrolysis of water and co-electrolysis of H₂O and CO₂, and H₂/CO ratio of the product can be tuned through modifications on the A- and B-site doping.