LDH-derived CoTiAl mixed oxide as catalyst for photo-assisted CO2 hydrogenation

Abstract

A layered double hydroxide (LDH) has been used as precursor for the synthesis of a multimetallic mixed oxide with photocatalytic activity. Thus, a trimetallic CoTiAl LDH has been synthesized as spherical aggregates of nanosheets. Analysis at short synthesis times indicates that CoTiAl-LDH particles grow perpendicular to initially formed oligomeric Ti-lactate nuclei. Calcination of CoTiAl-LDH at 400 °C affords the corresponding CoTiAl mixed oxide (MO) with low crystallinity having a cobaltite structure, while also maintaining the morphology. This CoTiAl-MO exhibits at 200 °C photocatalytic activity for CO2 hydrogenation to CO, accompanied with lesser amounts of CH4, with remarkable apparent quantum yields at 365 nm of 7.0 and 4.6 for CO and CH4, respectively and very low apparent activation energy for 10 kJ/mol. The present results show a promising direction to exploit the potential that the preparation of multimetallic LDH offers for the synthesis of mixed oxides with optimal compositions for an even more enhanced photocatalytic activity.

Keywords

• Solar energy conversion
• Photo-assisted CO2 hydrogenation
• Continuous flow
• Reverse water gas shift reaction
• Ti-based layered double hydroxides
• Mixed metal oxides