Rare earth oxide promoted Ru/Al2O3 dual function materials for CO2 capture and methanation: An operando DRIFTS and TGA study

Dual-function materials (DFMs) combine sorbent and catalytic components to perform selective CO 2 capture and subsequent hydrogenation. This study explores the performance of rare-earth oxides (REOs) as CO 2 adsorption sites on Ru/Al 2 O 3 . REOs increase CO 2 uptake by upwards of +60 % by enhancing the overall catalyst surface basicity and favoring metal–support interactions. Thermogravimetric analysis during CO 2 adsorption-hydrogenation cycles exhibited significant catalytic activity and enhanced stability of Ru-REO/Al 2 O 3 at temperatures as low as 200 °C. This leads to methane production of 50–85 µmol g −1 , surpassing recently reported values obtained for alkali and alkali-earth promoted Ru-based materials operated at 250 °C. The highest performing studied DFM, RuNd 2 O 3 /Al 2 O 3 , achieved 85 % CO 2 capture efficiency and steadily produced methane in cyclic operation (+120 % CO 2 uptake relative to Ru/Al 2 O 3 ). Operando DRIFTS revealed that the dominant mechanism for methane formation is the hydrogenation of ruthenium carbonyls, which are stabilized by REOs. Upon CO 2 exposure, surface carbonates and bicarbonate species form more abundantly on DFMs than on Ru/Al 2 O 3 . This confirms that REOs enhance the adsorption and retention of carbonates, which generate additional promoter-related reaction pathways during low-temperature hydrogenation. These findings are crucial in the advancement of sustainable, wider operation range carbon capture and utilization technologies. • Rare-earth oxides (REOs) were used as sorbents for enhanced CO 2 capture in DFMs. • DFMs (Ru-REO/Al 2 O 3 ) capture CO 2 and convert it to CH 4 via cyclic operation at 200 ºC. • 120 % more CO 2 capture and CH 4 production with DFMs compared to Ru/Al 2 O 3 . • DFMs showed remarkable stability and sustained conversion over 15 cycles at 200 ºC. • Operando DRIFTS studies identified carbonates as reacting species on the DFMs.