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

The activity of the pre-reduced perovskites La0.6 Sr0.4 FeO3-δ (LSF64) and SrTi0.7 Fe0.3 O3-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+H2 O 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.