MgO promoted by Fe2O3 and nitrate molten salt for fast and enhanced CO2 capture: Experimental and DFT investigation

Abstract

Rapid and strong CO2 capture is critical in CO2 capture and utilization (CCU) techniques to mitigate global warming. Alkali molten salt (AMS) promoted-MgO sorbents with high capacity attracted attention, but their applications suffer from various limitations of low adsorption kinetics and poor stability. Here, AMS-promoted MgO sorbents corporation with Fe2O3 (Mg100-xFex-AMS10) were fabricated via modified methanol evaporation-induced surface precipitation for use in rapid and stable CO2 capture. Based on characterization of the sorbents, Mg98Fe2-AMS10 showed a loose flake structure, with a large surface area and numerous exposed active sites. Therefore, Mg98Fe2-AMS10 exhibited a strong CO2 capacity (14.86 mmolCO2/gsorbent at 300 °C) and good cyclic durability. Three kinetic models were explored, and the Avrami model provided a good prediction of the CO2 adsorption behavior, with Mg98Fe2-AMS10 exhibiting rapid adsorption kinetics. The adsorption mechanism was investigated using density functional theory (DFT) calculations. The charge transfer and bonding strengths of the surface O atoms on MgO increased, and these atoms preferentially bonded with activated CO2 (CO2∙−) under Fe catalysis. This study may provide insights into enhancing the CO2 capture and kinetics of MgO via combination with 3d transition metals.