Structural engineering of NiFe-Layered double hydroxides and halloysite composites for efficient CO2 capture

The cost-and use-effects for solid CO2 adsorbents have accelerated development of the clay-based adsorbents. Herein, a series of NiFe-layered double hydroxides/halloysite (NiFe-LDH/Hal) composites were fabricated via facile hydrothermal strategy using calcined halloysites (Hal) as supports. Depending on treatment temperatures of halloysite, the supported NiFe-LDH exhibited different morphologies in form of nanoparticle or intertwined nanosheets. Based on the distinct morphology, these NiFe-LDH/halloysite composites displayed different textural properties and CO2 adsorption performance. Particularly, the sample NiFe-LDH/Hal600 using halloysite calcined at 600 degrees C as support possessed 3D hierarchical structure, and displayed superior CO2 adsorption capacity of 60.7 mg g-1 and 40.3 mg g-1 at 273 K and 298 K, respectively, much higher than those of NiFe-LDH/Hal composites supporting LDH nanoparticles. The high isosteric heat of adsorption calculated from Clausius-Clapeyron equation (21.7 kJ mol-1) indicated the strong interaction between basic NiFe-LDH surface and CO2 molecules. It was validated that the dehydroxylation and forming of silanols groups during calcination process changed the activity of internal and external surface, resulting in distinct morphology and distribution difference of the supported NiFe-LDH. The prepared clay-based composites displayed satisfying recyclability of CO2 adsorption at a high retention level after 25 cycles of adsorption-desorption.