One of the main concerns related to environmental impact of human activity is the carbon dioxide emission, which is responsible for the global warming. In the short term, the current fossil-based technologies which are the primary cause of CO2 production are unlikely to be replaced by more sustainable one. To achieve the goal of climate neutrality by 2050, the World Community has given a strong incentive to renewable energies, but the search for processes aiming at capturing and valorizing carbon dioxide still remains of crucial importance. In this context, photo catalytic reduction of CO2 with H2O using solar energy, well-known as artificial photosynthesis, is considered one of the most elegant and investigated strategies. As a result, solar fuels and high-value chemicals such as formic acid, methane and methanol can be obtained. Of special interest is the production of formic acid, which is not only a valuable chemical (i.e. preservative and antibacterial agent), but also considered a hydrogen storage compound with potential application in fuel cells, being prompt to release H2 by thermal decomposition. Since CO2 is regenerated during this latter pathway, the concentration of the greenhouse gas is not reduced in the overall process.Researchers from Italian CNR-ICCOM-SS Bari’s Caterina Fusco, Angelo Nacci & Lucia D’Accolti, University of Bari’s Chemistry Department Michele Casiello, Pasquale Pisani, Antonio Monopoli, Angelo Nacci & Lucia D’Accolti, CNR-NANOTEC-SS Bari’s Fiorenza Fanelli, CNR-ICCOM’s Werner Oberhauser and Acciaierie d’Italia’s Rosella Attrotto in a research paper have unveiled possibilities of steel slag as low-cost catalyst for artificial photosynthesis to convert CO2 and water into hydrogen and methanol.Photo reduction of CO2 with sunlight to produce solar fuels, also named artificial photosynthesis, is considered one of the most attractive strategies to face the challenge of reducing greenhouse gases and achieving climate neutrality. Following an approach in line with the principles of the circular economy, the low-cost catalytic system based on an industrial by-product such as steel slag was assessed, which was properly modified with nanostructured palladium on its surface in order to make it capable of promoting the conversion of CO2 into methanol and hydrogen through a two-stage process of photo reduction and thermal conversion having formic acid as the intermediate. Notably, for the first time in the literature steel slag is used as photo reduction catalyst.Pristine steel slag, supplied by AcciaieriedItalia’s Taranto Plant, consists of two crystalline phases, namely CaAl2O413 and Fe3O414 in a 65 and 35 ratio respectively, based on a Rietveld profile refinement. Nanostructured palladium was deposited onto the slag by a wet impregnation method15 affording the nanocomposite Pd@slag labelled as catalyst.In conclusion, these preliminary studies demonstrate that a catalyst material composed by steel slag decorated with Pd structured can convert CO2 and water into methanol and hydrogen via formic acid as intermediate, through a two-step reaction involving a photochemical and thermal reaction. Steel slag has been involved for the first time in the photo reduction of CO2, most probably by virtue of the iron impurities, while Palladium account for the thermal conversion of formic acid into hydrogen and methanol.This process is important not only for matching the Circular Economy principles making use of wastes as both reagents CO2 and catalysts slag, but also for producing in high selectivity an attractive storage medium such as formic acid. In fact, although HCOOH contains only 4.4% hydrogen by mass, it is a precious intermediate because is liquid at room temperature and therefore easy to handle and transport, commercially available on a large scale, and the by-product of H2 release, carbon dioxide, can be trapped and either recycled or used as a C1 source for other chemicals. Studies are in progress to ascertain the exact mechanism with which palladium converts formic acid into methanol and hydrogen.