CO2 Reduction on the Pre‐reduced Mixed Ionic–Electronic Conducting Perovskites La0.6Sr‐0.4FeO3‐δ and SrTi0.7Fe0.3O3‐δ

• Published in: Chemphyschem Vol. 19; no. 1; pp. 93 - 107
• Main Authors: Grünbacher, Matthias, Götsch, Thomas, Opitz, Alexander K., Klötzer, Bernhard, Penner, Simon
• Format: Journal Article
• Language: English
• Published: 05-01-2018
• Subjects: adsorption; carbon dioxide; dissolved hydrogen; oxygen vacancies; perovskites
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201700970

The activity of the pre‐reduced perovskites La0.6Sr0.4FeO3‐δ (LSF64) and SrTi0.7Fe0.3O3‐δ (STF73) for the CO2 reduction to CO was investigated with special focus on the reactivity of oxide‐dissolved hydrogen. This is of particular interest in hydrogen solid‐oxide electrolysis cell (H‐SOEC) technology, where proton‐conducting ceramics are used and the reaction 2e−+2H++CO2→CO+H2O is of central importance. To clarify if hydrogen dissolved in LSF64 and STF73 partakes in the CO2 reduction, temperature‐programmed reduction (TPR) in H2, followed by temperature‐programmed reoxidation (TPO) in CO2 and, moreover, temperature‐programmed desorption (TPD) of ad‐ and absorbed species were utilized. The experiments reveal that 50 mol % of the CO2 is converted by hydrogen dissolved in STF73 and reacts quantitatively. On the other hand, LSF64 converts less than 20 mol % of CO2 via dissolved hydrogen and a residual of bulk OH is still detectable after CO2‐TPO.
The reactivity of oxide‐dissolved hydrogen in the reduction of CO2 to CO is investigated using the pre‐reduced perovskite materials La0.6Sr0.4FeO3‐δ (LSF64) and SrTi0.7Fe0.3O3‐δ (STF73). This is of particular interest in hydrogen solid‐oxide electrolysis cell technology, where proton‐conducting ceramics and the reaction 2e−+2H++CO2→CO+H2O are of paramount importance. Hydrogen dissolved in STF73 reacts quantitatively with CO2, whereas LSF64 tends to retain hydrogen.