Artificial Photosynthesis: from CO2 to Fuels

The development of solar energy requests new technologies for energy storage. One fascinating option resides in the selective reduction of CO2 into energy-dense organic compounds. This strategy is used in photosynthetic organisms which have evolved a unique mechanism to convert CO2 and H2O into biomass under sunlight. PhotoCarb is aimed at developing novel energy storage systems via an artificial photosynthesis approach. This consists in the preparation, characterization, heterogenization of photosensitizer/electron reservoir/catalyst molecular assemblies and their evaluation as catalysts for CO2 photoelectroreduction. The objective of PhotoCarb is the development of a complete PhotoElectrochemical Cell (PEC) based exclusively on non-noble metals. Thus three tasks are proposed. Task 1 is devoted to the optimization of catalysts discovered within the previous CarBioRed ANR project, namely metal-terpy (metal = Co, Ni or Mn) complexes, cobalt-diphosphine-cyclopentadienyl complexes and metal-dithiolene (metal= Mo and Ni) complexes. In addition an original issue, specifically their combination with proton- and electron-reservoirs appropriate for the multi-proton and multi-electron processes at work, is addressed in the PhotoCarb project. Polyoxometalates (POMs) exquisitely fit such properties and are chosen for exploring the potential of POM-catalyst supramolecular systems. Task 2 will select the best systems to engineer and evaluate the performances of molecular-based photocathodes, via their immobilization on low band-gap semiconductors and the elaboration of dye-sensitized photocathodes. Task 3 finally will integrate the best photocathodes within a PEC. This research will not only provide new insights into basic questions regarding multi-electron multi-proton CO2 reduction (photo)catalysis but also translate this knowledge into a practical proof-of-concept device, which is still a challenging issue.