Calcium-based dual-functional materials for integrated CO2 capture and reverse water gas shift: Boosting stored CO2 hydrogenation via dispersed MgO-CaCO3 interfaces

The chemical looping principle of integrated CO₂ capture and hydrogenation has shown promise for streamlining carbon capture processes and reducing energy consumption. However, the practical application is hindered by the kinetic limitations of dual functional materials (DFMs). In this work, we investigated the synergistic effect of the magnesium-calcium interface to enhance CO₂ capture and RWGS performance under ideal feed gas conditions (CO₂ in Argon without steam or oxygen). By fine-tuning the Mg-to-Ca ratio, Mg_0.12Ca_0.36CO₃ exhibited an eightfold improvement in integrated CO production compared to conventional CaO, reaching 9.54 mmol g⁻¹ at 650 °C. Experimental results and mechanistic studies revealed that the incorporation of Mg not only enhanced the stability of the carbonate lattice during the reverse water–gas shift reaction but also facilitated efficient CO₂ hydrogenation by strengthening the basic sites. The interfacial sites effectively activate the stored CO₂, promoting the formation of HCOO* intermediates and their subsequent conversion to CO via deoxygenation. Theoretical calculations provided further insights into the superiority of the MgO-CaCO₃ interface for activating stored CO₂, demonstrating stable CO₂ adsorption and low H₂ dissociation barriers at the interface. These findings highlight the potential of strategically incorporating Mg into CaCO₃-based DFMs as a viable approach to enhance the stability and efficiency of integrated CO₂ capture and hydrogenation in real-world applications.