Facet Sensitivity of Capping Ligand‐Free Ag Crystals in CO2 Electrochemical Reduction to CO

Abstract Silver‐based electrocatalysts are active in catalyzing electrochemical reduction of CO 2 to CO. We herein report synthesis of capping ligand‐free Ag cubes and octahedra by morphology‐preserved CO reduction from corresponding Ag 2 O counterparts and their performance in electrochemical reduction of CO 2 . Ag cubes are much more active than Ag octahedra and exhibit a stable CO formation rate as high as 142.4 mmol CO g cat −1 h −1 at −0.95 V (vs. RHE). Ag films transiently formed on Ag 2 O crystals during CO 2 electroreduction were observed more active than Ag crystals, revealing a promoting effect of Ag 2 O 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.