Synthesis, characterization and visible light photocatalytic activity of metal based TiO₂ monoliths for CO₂ reduction

The use of multichannel monoliths for CO2 photoreduction applications is gaining increased attention over slurry and annular reactors due to their tunable geometry for reactor designs and exposed surface area per volume. Metal based TiO2 sol with varying concentrations of Cr, V and Co were deposited on ceramic honeycomb monolithic structures threaded with optical fibres, which can provide light irradiation along each coated interconnected monolithic channel. The coated monoliths show a red shift of absorption edge and light absorption in the visible light region increase with increasing metal concentration compared to pure TiO2. Photocatalytic activities of the metal based TiO2 monoliths under visible light irradiation were evaluated for vapour-phase CO2 photoreduction with H2O. Maximum acetaldehyde rate of 11.13 μmol/gcat h was achieved over the 0.5 wt% V–TiO2 monolith after 4 h of visible light irradiation.