High-Performance CO ₂ Capture and In Situ CO Generation over Calcium Looping by Hydrogen Calcination Strategy

This work introduces a cyclic process based on the hydrogen reduction of CaCO3 to prepare highly active CaO, enabling efficient CO2 capture and in situ conversion. Under a hydrogen atmosphere, the decomposition temperature of CaCO3 decreases by approximately 150 °C, accompanied by the formation of CO. Compared with conventional CaO prepared by air calcination at ≥900 °C, the hydrogen-reduced CaO exhibits reduced particle aggregation, higher oxygen vacancy concentration, and enhanced surface basicity. Its CO2 capture capacity reaches 0.727 gCO2/gCaO, close to the theoretical value of 0.786 gCO2/gCaO. Crucially, the captured CO2 can be converted in situ to value-added CO or syngas under the hydrogen reduction atmosphere, forming a CO-rich stream with potential for subsequent utilization, thereby enabling the resource utilization of inorganic carbon. Furthermore, electron paramagnetic resonance (EPR) and CO2-temperature-programmed desorption (CO2-TPD) analyses reveal that hydrogen reduction increases the vacancy concentration, enhances CaO surface basicity, and facilitates CO2 activation and capture.