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

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 mmol(CO) g(cat)(-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.