Optimising the acid–base ratio of Mg–Al layered double oxides to enhance CO2 capture performance: the critical role of calcination conditions

Abstract

The effect of calcination conditions (ramp rate, calcination temperature and time) on the formation of Mg₂Al layered double oxides (Mg₂Al LDOs) as well as their CO₂ capture performance, has been systematically investigated. This study explores novel insights into the intricate relationship between these calcination conditions and the resulting surface characteristics, which play a vital role in CO₂ capture efficiency. Notably, it is revealed that a rapid ramp rate (100 °C min⁻¹) significantly increases surface area and hydroxyl concentration, leading to a 69% increase in CO₂ capture efficiency compared to slower ramp rate. Conversely, short calcination times (1 h) and fast ramp rates (100 °C min⁻¹) are observed to compromise CO₂ adsorption due to the presence of dehydrated LDHs. A critical acid : base ratio of 0.37, achieved from a fast ramp rate (100 °C min⁻¹) at 400 °C for 2 h, was found as a key threshold for optimising surface properties, effectively balancing favourable hydroxyl and less favourable strong acid sites, thereby maximizing CO₂ capture performance.