Abstract
Cu-Mg-Al layered double hydroxides (LDHs) with amine modification were prepared by an organic combination of an anionic surfactant-mediated method and an ultrasonic spalling method using N-aminoethyl-γ-aminopropyltrimethoxysilane as a grafting agent. The materials were characterized by elemental analysis, XRD, SEM, FTIR, TGA, and XPS. The effects of the Cu2+ content on the surface morphology and the CO2 adsorption of Cu-Mg-Al LDHs were investigated, and the kinetics of the CO2 adsorption and the photocatalytic reduction of CO2 were further analyzed. The results indicated that the amine-modified method and appropriate Cu2+ contents can improve the surface morphology, the increase amine loading and the free-amino functional groups of the materials, which were beneficial to CO2 capture and adsorption. The CO2 adsorption capacity of Cu-Mg-Al N was 1.82 mmol·g−1 at 30 °C and a 0.1 MPa pure CO2 atmosphere. The kinetic model confirmed that CO2 adsorption was governed by both the physical and chemical adsorption, which could be enhanced with the increase of the Cu2+ content. The chemical adsorption was suppressed, when the Cu2+ content was too high. Cu-Mg-Al N can photocatalytically reduce CO2 to methanol with Cu2+ as an active site, which can significantly improve the CO2 adsorption and photocatalytic conversion.
Highlights
IntroductionUncontrolled burning of fossil fuels, since the industrial revolution, has caused serious energy consumption problems, and made global warming an urgent problem for human sustainable development due to the sharp increase of CO2 concentration in the atmosphere [1,2,3]
Observed from the formula for intercalated molecules, the increment of amino silanes was greater than the decrement of the anionic surfactant, which indicated that amino silanes partially replaced the anionic active sites and condensed with the surface hydroxyl groups on the laminates
The kinetic model confirmed that the complex CO2 adsorption mechanism of
Summary
Uncontrolled burning of fossil fuels, since the industrial revolution, has caused serious energy consumption problems, and made global warming an urgent problem for human sustainable development due to the sharp increase of CO2 concentration in the atmosphere [1,2,3]. For this reason, capturing CO2 from sources and converting it to carbon-containing fuels or high-value non-fuel chemicals are currently relatively attractive solutions to avoid extreme climate change [4,5]. Because LDHs materials have attractive physiochemical properties, such as characteristic layered structures with large surface areas, specific “memory effects”, high anion exchange capacity, precise morphological controllability, facileness to synthesize, and low costs [6,7,8,9,10,11]
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