Solar fuels from the photocatalytic reduction of CO2

Invited Keynote lecture The possibility to reduce CO2 by means of solar light is attractive as a powerful tool to reconvert a harmful greenhouse gas into renovated fuels and it is also a straightforward method to store solar energy. The basic principles for the process will be recalled, together with the more recent advancements on materials design for this application, with particular reference to inorganic semiconductors. The attention will be then focused on photoreactors and process design and on the available examples of direct solar light conversion. The coupling of smart materials with tailor made devices is indeed the route to enhance the solar storage efficiency of these processes, which is currently still too low for exploitation. The main open challenges will be discussed from both the points of view of materials requirements and reactors. An attractive opportunity will be also discussed, consisting in the coupling of solar concentrators with photoreactors to amplify solar light utilization and explore unconventional operating conditions.