High‐Rate,Tunable Syngas Production with Artificial Photosynthetic Cells

An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H₂O, a Ni‐SNG cathodic catalyst for the dark reaction of CO₂ reduction in a CO₂‐saturated NaHCO₃ solution, and a proton‐conducting membrane enabled syngas production from CO₂ and H₂O with solar‐to‐syngas energy‐conversion efficiency of up to 13.6 %. The syngas CO/H₂ ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h^?1 was recorded with a photoanodic N‐TiO₂ nanorod array for highly stable CO production. The CO‐evolution rate reached a maximum of 154.9 mmol g^?1 h^?1 in the dark compartment of the APS cell. Scanning electrochemical–atomic force microscopy showed the localization of electrons on the single‐nickel‐atom sites of the Ni‐SNG catalyst, thus confirming that the multielectron reduction of CO₂ to CO was kinetically favored.