Quantifying Electrocatalytic Reduction of CO₂ on Twin Boundaries

A protocol relying on the use of silver nanostructures with welldefined dimensions and morphologies (e.g., nanocubes and nanowires) has been developed to differentiate and quantitatively determine the atom-specific activities of different surface atoms to ward catalyzing electrochemical CO2 reduction reaction (CO2RR). The atom-specific activity of the twin-boundary edges (TBEs) is comparable to (or slightly higher than) that of the single-crystal edges (SCEs) formed from the crossing of two {100} surfaces, and it is on the order of similar to 16 attoampere/atom (aA/atom) toward electrochemical CO2RR. This value is more than two orders higher than the atomspecific activity of the {100} surface atoms, i.e., similar to 0.1 aA/atom. The high catalytic activity of the TBEs, which represent a class of commonly existing surface defects in stable metal nanostructures with face-centered cubic lattices, is consistent with the DFT calculations, in which the bridge-type binding configuration of COOH* at the TBEs stabilizes this intermediate to promote overall CO2RR.