Highly stable FeNiMnCaO catalyst for integrated CO₂ capture and hydrogenation to CO

The integrated CO₂ capture from flue gas and hydrogenation can be realized by the consecutive calcium-looping (CaL) and reverse-water–gas-shift (RWGS) reactions. However, the incompatibility between the catalysis and adsorption components aggravates the sintering and deactivation of metal particles and CaO base material during the high-temperature process. Herein, we prepared a highly efficient and stable FeNiMnCaO material via a modified sol–gel method for in situ CaL and RWGS reaction, exhibiting a CO₂ adsorption capacity of 13.2 mmol g⁻¹ at 40 cycles with 58.0 % CO₂ conversion and 100 % CO selectivity at 700 °C. The highly-dispersed Fe and Ni species in the developed catalyst not only suppressed the sintering of MnCaO, but also synergistically benefited the RWGS reaction, where FeO_x species promoted CO₂ adsorption and metallic Ni facilitated H₂ dissociation. The reaction followed the H-assisted association formate mechanism, in which adsorption of CO₂ occurred at the FeO_x-CaO interface with the aid of the hydroxyl surface groups to form bidentate bicarbonates, followed by dehydration to bidentate formate and decomposition to CO and H₂O in the presence of Ni-dissociated reactive H* species.