Direct air capture and isothermal conversion of CO2 to CO over La-based perovskite mixed metal oxides

Abstract

The atmospheric CO2 (∼400 ppm) poses a formidable obstacle for efficient direct air capture and in situ conversion without desorption during transition from capture to reaction stage. Therefore, developing dual-function materials (DFMs) with well-defined active sites is essential for integrating CO2 adsorption and catalytic hydrogenation. Here, we demonstrate the viability of a La-based perovskite mixed oxide Co/La-LaCoO3 (Co/LCO) as a DFM for direct air capture and in situ conversion under isothermal conditions with simulated air conditions (400 ppm CO2/ 4.2 vol% H2O in inert gas). For comparison, La2O3 and Co/CoOx were also evaluated. H2-TPR and CO2-TPD analyses revealed reduction of Co species in LaCoO3 (from Co3 + to Co2+ and Co0), while CO2 was strongly adsorbed. Consequently, Co/LCO exhibited a breakthrough CO2 adsorption of 48.9 μmol g−1 (3.4 and 44.4 fold higher than control DFMs). Under hydrogenation step, Co/LCO produced 20.9 μmol g−1 of CO, outperforming La2O3 (5.07 μmol g−1) and Co/CoOx (no detectable CO). Under humid conditions (75 % RH), Co/LCO showed significantly increased CO2 adsorption but suppressed CO formation up to 400 °C, which recovered at elevated temperatures. This work demonstrates the potential of La-based perovskite mixed oxides as a promising DFM for direct CO2 capture and selective conversion.