Controlling the contribution of transport mechanisms in solid oxide co-electrolysis cells to improve product selectivity and performance: A theoretical framework

Solid oxide co-electrolysis cells offer a promising route to convert carbon dioxide and steam into syngas utilizing renewable energy. Significant challenges that persist in their development are determining the reaction pathways that contribute to carbon monoxide production and carbon deposition in the cathode, which can lead to catalyst deactivation and electrode fracture. The vast majority of numerical models have limited their chemical reaction framework to the reverse water gas shift reaction and methane steam reforming, which alone cannot account for gas-phase reactions that may occur spontaneously due to the elevated operating temperatures, as well as carbon deposition that has been reported in previous experiments. Accordingly, this work develops and experimentally validates a combined 1-D + 1-D mass, momentum, heat, and charge transport model to track the reaction pathways by which each component is utilized/produced and to derive operation strategies to mitigate carbon deposition. Additionally, this analysis develops a combined numerical and experimental approach to extract the catalytic properties of electrode materials, in order to facilitate direct comparisons between the performance of various materials. For the first time, designers and researchers will be able to utilize this model to develop operation strategies in order to alleviate carbon deposition in the cathode, which will improve cell durability and longevity, attain H2/CO ratios desirable for Fischer–Tropsch reactor feedstock, and enhance cell performance.