Steam Electrolysis Coupled with CO2 Conversion in a Pressurized Proton Conducting Solid Oxide Electrolysis Cell
Date
2022-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Development of proton conducting solid oxide electrolysis cells (H-SOECs) for steam electrolysis coupled with the conversion of CO2 into fuels is a promising strategy for mitigating global warming. The aim of this research was to design and test a pressurized H-SOEC with an active Fischer-Tropsch cathode. Although no liquid hydrocarbons were produced at elevated pressures, the H-SOEC was able to synthesize CO, H2 and CH4 from steam and CO2. The electrochemical performance of this cell was modest with a maximum current density of 42 mA cm-2 (at 5 V), due to the presence of mass transfer limitations and ohmic losses. Two relevant phenomena related to application of proton conducting ceramics technology in the conversion of CO2 were analysed: the interaction between supported iron oxides and conducting substrates with oxygen vacancies, and the degradation of proton conducting perovskites in the presence of CO2. Ceramic supports containing oxygen vacancies as extrinsic defects (such as proton conducting perovskites) promote the reduction of iron oxide with activation energies lower than for the reduction of pure iron oxide. Kinetic analysis indicated that these defects not only facilitated the removal of oxygen ions, but also promoted the formation and growth of metal nuclei in 2 and 3 dimensions. Conversely, it was determined that supports with intrinsic oxygen vacancies inhibit the reduction of supported Fe2O3 due to a strong metal support interaction. Low-cerium BaCe0.1Zr0.8Y0.1O3-δ (BCZY) perovskite was not stable under CO2 at elevated pressures. Kinetic analysis revealed that the carbonation of BCZY is a single-step solid gas reaction that can be described by a first order nucleation/nuclei growth mechanism, which produces a carbonate protective layer that inhibits the deterioration of the internal crystalline structure. On the contrary, proton conducting perovskite H-SOEC with the composition Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ (BSCZGY) showed good chemical stability under CO2 at elevated pressures. These results demonstrate the practical application of proton conducting ceramics technology in the conversion of CO2 and H2O at high pressures for the first time.
Description
Keywords
Proton conducting ceramics and perovskites
Citation
Mora, J. C. (2022). Steam electrolysis coupled with CO2 conversion in a pressurized proton conducting solid oxide electrolysis cell (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.