Photocatalytic carbon dioxide reduction to fuels in continuous flow monolith photoreactor using montmorillonite dispersed Fe/TiO₂ nanocatalyst

Photocatalytic conversion of CO₂ to fuels has attracted immense attention because it offers a cleaner energy technology and safer environment. In this study, performance of structured montmorillonite (MMT) dispersed Fe-doped titanium dioxide (Fe/TiO₂) nanocomposite was tested for dynamic photo-induced CO₂ reduction by H₂ to fuels. Cordierite monolithic support was employed in order to improve the photo-activity and reusability of Fe-MMT/TiO₂ nanocomposite in a CO₂ utilization process. MMT-clay supported Fe/TiO₂ samples were prepared by a controlled and direct sol-gel method and were dip-coated over the monolith micro-channels. The efficiency of Fe-loaded MMT/TiO₂ for CO₂ reduction by H₂ toward CO was investigated using a cell type and a monolith photo-reactor under UV-light. The maximum CO yield over 3 wt % Fe-10 wt % MMT-loaded TiO₂ catalyst reached 166 μmole g-catal.⁻¹ h⁻¹ at selectivity 99.70%, considerably higher than the amount of CO produced over the MMT/TiO₂ (16 μmole g-catal.⁻¹ h⁻¹) and the pure TiO₂ (5 μmole g-catal.⁻¹ h⁻¹) catalysts. The other products observed with adequate amounts were CH₄ and C₂H₆. More importantly, photo-activity and stability of Fe-MMT/TiO₂ catalyst for CO evolution was significantly improved using monolith photo-reactor compared to the cell type reactor under the same operating conditions. This enactment was evidently due to higher quantum efficiency of monolith photoreactor, improved adsorption-desorption process in a catalyst coated monolith channels and hindered charges recombination by Fe. The reusability of catalyst loaded over the monolithic support showed greater recycling capability than the catalyst dispersed in a cell reactor. This development confirmed higher photo-activity of Fe-MMT/TiO₂ photo-catalyst loaded over monolithic support for CO₂ photo-reduction to cleaner fuels.