Layered double hydroxides supported on multi-walled carbon nanotubes: preparation and CO2 adsorption characteristics

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Layered double hydroxides (LDHs) are promising materials for CO2 sorption, although improvements in performance are required for practical applications. In the current study, the CO2 sorption capacity and multi-cycle stability were both increased by introducing an open supporting framework of multi-walled carbon nanotubes (MWNTs). This nanostructured inert network provides a high surface area, maximizing the gas accessibility and minimizing coarsening effects. Specifically, LDH nanoparticles were precipitated directly onto MWNTs, initially oxidised to ensure a favourable electrostatic interaction and hence a good dispersion. The dependence of the structural and physical properties of the Mg–Al LDH grown on MWNT supports has been studied, using electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), and BET surface area, and correlated with the CO2 sorption capacity, established via TGA and temperature programmed desorption measurements. The use of a MWNT support was found to improve the absolute capacity and cycle stability of the hybrid adsorbent under dry conditions.