Organosodium-derived Na2ZrO3 sorbents for low-concentration CO2 capture: An experimental and DFT study

In recent years, the development of novel solid materials for high-temperature CO2 capture has garnered worldwide attention. The advancement and investigation of Na2ZrO3-based sorbents have provided a novel technological route and application potential for industrial CO2 removal. However, the unsatisfactory capacity and unclear sorption mechanism hinder its further development. In this work, organosodium-derived Na2ZrO3 was synthesized, and the CO2 sorption performance exhibited obvious enhancement with the total CO2 capacity increased by 20.69 % even under 15 vol% CO2 atmospheres. In addition, the modification mechanism of organic sodium sources as well as the reaction behavior between Na2ZrO3 and CO2 was investigated via kinetic analysis and various characterization techniques. Sorbents derived from organic sodium sources, characterized by a significant amount of small mesopores (3-4 nm), exhibited high reaction rates during the superficial chemisorption stage. Besides, the CO2 sorption reaction was described via the double-shell model, and the activation energies for the superficial chemisorption and bulk diffusion stages were calculated to be 30.2 kJ/mol and 54.3 kJ/mol, respectively. Finally, the CO2 chemisorption mechanism of Na2ZrO3 was studied via density functional theory (DFT) calculations for the first time. Chemisorption was the product of bonding between C atom of CO2 molecule and O atom on the surface, and O atom was the main active center for the chemisorption. Generally, this study proposed an effective route for the production of structurally-improved Na2ZrO3 sorbents for efficient CO2 capture, and the sorption mechanisms were thoroughly studied from the macro to the micro level.