Synthesis of new LDH-derived composites with enhanced photo-thermal properties exploited in photo-thermocatalytic processes for CO₂ conversion

The thermocatalytic CO₂ hydrogenation reaction is a high-energy-consuming process, and for this reason, it is important to develop new hybrid catalytic approaches, such as photo-thermocatalysis, in order to increase the efficency of this process and overcome its main disadvantages. The aim of this research is to synthesize a set of new Layer Double Hydroxide-derived composite materials to be used as photo-thermocatalysts to perform in the CO₂ methanation reaction. LDHs are in fact an excellent candidate for the photo-thermocatalytic conversion of CO₂. This is due to their great adsorption properties, their surface basicity and the presence of optical band-gaps that can be modulated due to the possibility of interposing different metal ions within the LDH structure or on its surface. In this study, ternary LDHs were synthesized by co-precipitation and hydrothermal treatment, inserting different metal species such as Ni or Co as catalytic active species, Mg, Zn, or Zr as photocatalytic active species, and Al or Ce for the structural role. The LDHs were then modified with SiC or different phyllosilicates such as Halloysite, Bentonite, Sepiolite, and Montmorillonite to obtain new materials able to absorb a larger portion of the solar emission spectrum and to increase the conversion of solar radiation into thermal energy, favouring the methanation reaction through a photo-assisted thermocatalytic mechanism. Catalytic tests showed that SiC significantly increased the photo-thermocatalytic activity of LDHs, enhancing yield and selectivity in methane at lower temperatures compared to thermocatalytic tests, while the samples modified with phyllosilicate are currently under investigation. Future objectives of this work include exploring different compositions for the synthesis of LDH–phyllosilicates and the synthesis of LDH–MXene composites to take advantage of the LSPR effect of MXenes so as to improve the photo-driven thermocatalytic activity of the materials.