Structural characterization and CO2 adsorption enhancement of synthesized calcined flower-like Mg–Al LDH@γ-Al2O3

Abstract

Abstract Flower-like Mg–Al CO 3 layered double hydroxides (LDHs) grown on γ-Al₂O₃ substrates with varying Mg:Al molar ratios (2:1 and 3:1 in the precursors( were successfully synthesized via a controlled co-precipitation method. The structural morphology, composition, crystallinity, porosity, and surface charge properties of the synthesized samples were systematically investigated using scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX) mapping, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, zeta potential measurements, and Fourier transform infrared (FTIR). Furthermore, the CO 2 capture potential of the calcined LDHs, known as layered double oxides (LDOs), was evaluated using thermogravimetric analysis (TGA) at different temperatures (25, 100, and 200 °C) in three consecutive adsorption-regeneration cycles. The results reveal that the improved flower-like morphology strongly influences the accessibility of CO 2 molecules to the active adsorption sites and, consequently, the CO 2 adsorption capacity. In addition, varying the Mg molar ratio significantly affects parameters such as specific surface area, surface charge, and layer positive charge density, but has a relatively limited effect on CO 2 adsorption capacity, likely due to the counterbalancing effects of these parameters. The highest CO 2 adsorption capacity observed was 2.63 mmol/g (for the 3:1 flower-like sample at 25 °C). Findings demonstrate that both 2:1 and 3:1 flower-like samples show promising potential for CO 2 capture at moderate temperatures, with adsorption capacities of 2.39 mmol/g and 2.43 mmol/g at 200 °C, respectively. Ultimately, a probable CO 2 capture mechanism using LDOs was proposed corresponding to the adsorption performance.