Photocatalytic Conversion of CO₂ into Oxygenate Fuels/Chemicals Using Efficient, Eco-Friendly, Titania/Hematite-Based Nanostructured Solar-Energy Materials.

Photocatalytic hydrogenation of carbon dioxide (CO₂), using water feedstock (H source), sunlight and appropriate semiconducting low-cost/eco-friendly/solar-energy materials, is a promising route for sequestration of this greenhouse gas and its conversion into value-added oxygenate fuels (compounds). Herein, by employing three hematite-based nanostructured photocatalyst/solar-energy materials, the CO₂ photoreduction (hydrogenation) process was carried out inside a water photosplitting reactor, and various oxygenate (C/H/O) products [including ethanol, methanol and formaldehyde as well as oxalic, acetic and formic acids] were synthesized in the reaction medium. Concerning the complexity of system and the diversity of products-being photocatalytically synthesized during the photoconversion process, two straightforward problem-solving strategies were proposed [one, focusing on a single/particular product and pursuing its quantity (concentration) at different illumination periods, and the other, simultaneous investigation of various products being produced at a fixed reaction period, in the aqueous or gas-phase medium]. Finally, the matter of CO₂ photoconversion into oxygenate fuels/chemicals was explained in detail from photoelectrochemical [semiconductor band structure and redox potential] as well as mechanistic perspectives.