Toward enhanced CO2 adsorption on bimodal calcium-based materials with porous truncated architectures

Abstract To increase the mineralization capabilities for the adsorption of carbon dioxide, we prepared bimodal calcium-based materials such as calcium oxide and calcium hydroxide with porous structures using a precipitation method with various drying processes. The various drying methods on porous structure develop different composition ratio of CaO and Ca(OH)2 in bimodal materials, and in particular, formation of different morphology and structure, which leads different adsorption characteristics. Samples prepared with such methods attained porous structure and more active adsorption sites. It is worth noting that the freeze drying (FD) and aerogel drying (AD) methods created the truncated crystal phase of the adsorbents, exposing active facet sites in the place of the vertices. The results of CO2 temperature programmed desorption and dynamic flow experiments reveal that porous calcium-based materials, synthesized through a process combining FD and AD sequentially, show high CO2 adsorption capacity (up to 26.1 wt. % at 650 °C) with enhanced adsorption kinetics. To gain insight into CO2 adsorptive configuration at the atomistic scale and the adsorption mechanism, the adsorption of multiple CO2 molecules on the CaO (100) surface is investigated using density functional theory calculation. The CO2 molecules are chemisorbed through active charge reorganization between the CaO surface and CO2 molecules while the adsorption energy is highly stabilized at –1.56 eV. The experimental and theoretical findings both suggest that CO2 mineralization is feasible on calcium-based bimodal structured materials.