The continuous combustion of non-renewable fossil fuels and depletion of existing resources is intensifying the research and development of alternative future energy options that can directly abate and process ever-increasing carbon dioxide (CO2) emissions. Since CO2 is a thermodynamically stable compound, its reduction must not consume additional energy or increase net CO2 emissions. Renewable sources like solar energy provide readily available and continuous light supply required for driving this conversion process. Therefore, the use of solar energy to drive CO2 photocatalytic reactions simultaneously addresses the aforementioned challenges, while producing sustainable fuels or chemicals suitable for use in existing energy infrastructure. Recent progress in this area has focused on the development and testing of promising TiO2 based photocatalysts in different reactor configurations due to their unique physicochemical properties for CO2 photoreduction. TiO2 nanostructured materials with different morphological and textural properties modified by using organic and inorganic compounds as photosensitizers (dye sensitization), coupling semiconductors of different energy levels or doping with metals or non-metals have been tested. This review presents contemporary views on state of the art in photocatalytic CO2 reduction over titanium oxide (TiO2) nanostructured materials, with emphasis on material design and reactor configurations. In this review, we discuss existing and recent TiO2 based supports, encompassing comparative analysis of existing systems, novel designs being employed to improve selectivity and photoconversion rates as well as emerging opportunities for future development, crucial to the field of CO2 photocatalytic reduction. The influence of different operating and morphological variables on the selectivity and efficiency of CO2 photoreduction is reviewed. Finally, perspectives on the progress of TiO2 induced photocatalysis for CO2 photoreduction will be presented

A family of Cu/TiO2 catalysts was prepared using a refined sol–gel method, and tested in the photocatalytic reduction of CO2 by H2O to CH4 using a stirred batch, annular reactor. The resulting photoactivity was benchmarked against pure TiO2 nanoparticles (synthesised by an identical sol–gel route). CO2 photoreduction exhibited a strong volcano dependence on Cu loading, reflecting the transition from 2-dimensional CuOx nanostructures to 3-dimensional crystallites, with optimum CH4 production observed for 0.03wt.% Cu/TiO2

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 CO2photoreduction withH2O.Maximum acetaldehyde rate of 11.13μmol/gcath was achieved over the 0.5wt% V–TiO2 monolith after 4h of visible light irradiation