Unassisted Solar Syngas Production by a Molecular Dye-Cobalt Catalyst Assembly in a Tandem Photoelectrochemical Cell

The ecological transition requires the development of carbon capture and utilization technologies powered by renewable energies. Direct solar conversion of CO 2 in photoelectrochemical cells is a promising approach to produce syngas, en route to fuels and chemicals. We report here on a dyad based on a Ru-based metallorganic dye and a tetraazamacrocyclic cobalt catalyst grafted on NiO to form efficient molecular photocathodes for CO-rich syngas production (ratio of CO/H 2 > 80:20) from a CO 2 -saturated aqueous bicarbonate buffer. After integration with a BiVO 4 /CoPi photoanode in a tandem photoelectrochemical cell in a Z-scheme configuration, syngas could be produced from CO 2 water with Faradaic efficiencies (FE) of 62 % and 14 % for CO and H 2, respectively, under visible light and in the absence of any applied bias, equating to a solar to fuel conversion efficiency of 1.3 × 10 –2 %.