A Molecular Z-Scheme Artificial Photosynthetic System Under the Bias-Free Condition for CO2 Reduction Coupled with Two-electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2O2

Bio-inspired molecular-engineered systems have been extensively investigated for the half-reactions of H2O oxidation or CO2 reduction with sacrificial electron donors/acceptors. However, there has yet to be reported a device for dye-sensitized molecular photoanodes coupled with molecular photocathodes in an aqueous solution without the use of sacrificial reagents. Herein, we will report the integration of Sn-IV- or Al-III-tetrapyridylporphyrin (SnTPyP or AlTPyP) decorated tin oxide particles (SnTPyP/SnO2 or AlTPyP/SnO2) photoanode with the dye-sensitized molecular photocathode on nickel oxide particles containing [Ru(diimine)(3)](2+) as the light-harvesting unit and [Ru(diimine)(CO)(2)Cl-2] as the catalyst unit covalently connected and fixed within poly-pyrrole layer (RuCAT-RuC2-PolyPyr-PRu/NiO). The simultaneous irradiation of the two photoelectrodes with visible light resulted in H2O2 on the anode and CO, HCOOH, and H-2 on the cathode with high Faradaic efficiencies in purely aqueous conditions without any applied bias is the first example of artificial photosynthesis with only two-electron redox reactions.