Integrated experimental and theoretical studies for unravelling CO2 capture of dual function CeO2-CaO bio-based sorbents

Abstract

Solid CaO-based sorbents for CO2 capture represent a promising alternative technology compared to traditional amine scrubbing methods. However, CaO-based sorbents are rapidly sinter and easily decrease CO2 uptake capacity with regenerated carbonation–calcination cycle. Thus, in this study, doping CaO with CeO2 make it an excellent candidate for improving stability and facilitating CO2 capture efficiency. The dual function of CaO bio-based sorbents with varying ratios of cerium (Ce) were derived from naturally occurring blood clam using the gel-combustion method. Their nanostructures and physicochemical properties were characterized through the specific methods, including in situ XAS, CO2 chemisorption and physisorption, XPS, XRD, and SEM. An in-depth understanding of CO2 adsorption mechanism was further emphasized using a density functional theory (DFT) simulation. The results demonstrate that nanosized CeO2-CaO, with a mole ratio of 1:9, exhibited the highest performance for CO2 capture (6.44 mmol CO2/g sorbent). It is postulated that Ce serves as a physical barrier, effectively partitioning adjacent CaO grains and thereby diminishing the sintering rate. CaO is identified as the primary adsorption site, in contrast to CeO2. Mixing the Ce-Ca dual oxide initiates the electron-rich O at the O’ site. The electron localization at the O’ active site improves the activity of O’, making the performance CeCa(200) for capturing CO2 capture dominant. This discovery suggests that CeO2-CaO holds promise as a sustainable alternative sorbent for future CO2 capture applications.