Bias-Free Solar-Driven Syngas Production: A Fe 2 O 3 Photoanode Featuring Single-Atom Cobalt Integrated with a Silver-Palladium Cathode.

Photoelectrochemical syngas production from aqueous CO 2 is a promising technique for carbon capture and utilization. Herein, we demonstrate the efficient and tunable syngas production by integrating a single-atom cobalt-catalyst-decorated α-Fe 2 O 3 photoanode with a bimetallic Ag/Pd alloy cathode. A record syngas production activity of 81.9 μmol cm -2  h -1 (CO/H 2 ratio: ≈1 : 1) was achieved under artificial sunlight (AM 1.5 G) with an excellent durability. Systematic studies reveal that the Co single atoms effectively extract the holes from Fe 2 O 3 photoanodes and serve as active sites for promoting oxygen evolution. Simultaneously, the Pd and Ag atoms in bimetallic cathodes selectively adsorb CO 2 and protons for facilitating CO production. Further incorporation with a photovoltaic, to allow solar light (>600 nm) to be utilized, yields a bias-free CO 2 reduction device with solar-to-CO and solar-to-H 2 conversion efficiencies up to 1.33 and 1.36 %, respectively.