Over a 15.9% Solar-to-CO Conversion from Dilute CO₂ Streams Catalyzed by Gold Nanoclusters Exhibiting a High CO₂ Binding Affinity

Development of efficient and selective electrocatalysts is a key challenge to achieve an industry-relevant electrochemical CO₂ reduction reaction (CO₂RR) to produce commodity chemicals. Here, we report that Au₂₅ clusters with Au-thiolate staple motifs can initiate electrocatalytic reduction of CO₂ to CO with nearly zero energy loss and achieve a high CO₂RR current density of 540 mA cm^-2 in a gas-phase reactor. Electrochemical kinetic investigations revealed that the high CO₂RR activity of the Au₂₅ originates from the strong CO₂ binding affinity, leading to high CO₂ electrolysis performance in both concentrated and dilute CO₂ streams. Finally, we demonstrated an 18.0% solar-to-CO conversion efficiency using a Au₂₅ electrolyzer powered by a Ga_0.5In_0.5P/GaAs photovoltaic cell. The electrolyzer also showed 15.9% efficiency and a 5.2% solar-driven single-path CO₂ conversion rate in a 10% CO₂ gas stream, the CO₂ concentration in a typical flue gas.