Photocatalytic reduction of CO2 to hydrocarbons using bio-templated porous TiO2 architectures under UV and visible light

Artificial TiO2 leaves with the morphology replicating that of Camellia tree leaves were synthesized through a multi-step bio-templating approach. Scanning and transmission electron microscopy images of the final products indicated that proposed method successfully replicates the highly porous structure of the leaf photosystem, down to the thylakoids. The hierarchical pore network and morphology of the bio-templated TiO2 catalyst were demonstrated to be critical factors in successful photocatalytic reduction of CO2 under UV (370 nm) and visible (515 nm) light. The artificial TiO2 leaves increased the selectivity towards methane in CO2 photoreduction compared with benchmark commercial catalyst under UV light. The new TiO2 structures also outperformed the P25 titania by more than 1.35 times in terms of total product yield (CO + CH4) of under visible light. We hypothesized that modifying the morphology of the catalyst can alter the pathway and efficiency of photocatalytic reactions. Deposition of ruthenium dioxide on the surface of the new TiO2 architecture showed further improvement in photocatalytic activity under both UV and visible light. The photocatalytic reduction of CO2 coupled with the oxidative water splitting was also validated by kinetic modelling. The experimental data exhibited a very good fit to the pseudo first order kinetics. The understanding of the morphological contribution of the photocatalyst revealed in this study can help to augment the efficiency and selectivity of CO2 photoreduction.