Predicted Structures of the Active Sites Responsible for the Improved Reduction of Carbon Dioxide by Gold Nanoparticles.

Gold (Au) nanoparticles (NPs) are known experimentally to reduce carbon dioxide (CO2) to carbon monoxide (CO), with far superior performance to Au foils. To obtain guidance in designing improved CO2 catalysts, we want to understand the nature of the active sites on Au NPs. Here, we employed multiscale atomistic simulations to computationally synthesize and characterize a 10 nm thick Au NP on a carbon nanotube (CNT) support, and then we located active sites from quantum mechanics (QM) calculations on 269 randomly selected sites. The standard scaling relation is that the formation energy of *COOH (ΔE*COOH) is proportional to the binding energy of *CO (Ebinding*CO); therefore, decreasing ΔE*COOH to boost the CO2 reduction reaction (CO2RR) causes an increase of Ebinding*CO that retards CO2RR. We show that the NPs have superior CO2RR because there are many sites at the twin boundaries that significantly break this scaling relation.