Potassium-Promoted Limestone for Preferential Direct Hydrogenation of Carbonates in Integrated CO 2 Capture and Utilization.

Integrated CO 2 capture and utilization (ICCU) via the reverse water-gas shift (RWGS) reaction offers a particularly promising route for converting diluted CO 2 into CO using renewable H 2 . Current ICCU-RWGS processes typically involve a gas-gas catalytic reaction whose efficiency is inherently limited by the Le Chatelier principle and side reactions. Here, we show a highly efficient ICCU process based on gas-solid carbonate hydrogenation using K promoted CaO (K-CaO) as a dual functional sorbent and catalyst. Importantly, this material allows ∼100% CO 2 capture efficiency during carbonation and bypasses the thermodynamic limitations of conventional gas-phase catalytic processes in hydrogenation of ICCU, achieving >95% CO 2 -to-CO conversion with ∼100% selectivity. We showed that the excellent functionalities of the K-CaO materials arose from the formation of K 2 Ca(CO 3 ) 2 bicarbonates with septal K 2 CO 3 and CaCO 3 layers, which preferentially undergo a direct gas-solid phase carbonates hydrogenation leading to the formation of CO, K 2 CO 3 CaO and H 2 O. This work highlights the immediate potential of K-CaO as a class of dual-functional material for highly efficient ICCU and provides a new rationale for designing functional materials that could benefit the real-life application of ICCU processes.