LAUSR

Silver‐based electrocatalysts are active in catalyzing electrochemical reduction of CO2 to CO. We herein report synthesis of capping ligand‐free Ag cubes and octahedra by morphology‐preserved CO reduction from corresponding Ag2O counterparts and their performance in electrochemical reduction of CO2. Ag cubes are much more active than Ag octahedra and exhibit a stable CO formation rate as high as 142.4 mmolCO gcat−1 h−1 at −0.95 V (vs. RHE). Ag films transiently formed on Ag2O crystals during CO2 electroreduction were observed more active than Ag crystals, revealing a promoting effect of Ag2O substrate on electrocatalytic activity of Ag film. These results clearly identify a facet sensitivity of silver electrocatalysts and highlight the importance of surface cleanness of Ag colloids as efficient electrocatalysts.