Efficient CO2 Electroreduction to CO Facilitated by Porous Ag(111)-dominant Ag Nanofoams and Cooperative Ionic Liquid Electrolytes

The application of electrochemical CO2 reduction reaction (CO2RR) to generate value-added products, including carbon monoxide (CO), represents a sustainable strategy for addressing the global carbon balance. Silver (Ag) has gained significant attention as an attractive and cost-effective electrocatalyst for CO2RR-to-CO due to high activity.  Here, the porous Ag nanofoam catalysts with Ag(111)-dominant were prepared by in-situ electrolysis-deposition method in the ionic liquid (IL) electrolyte. The Ag nanofoam catalysts exhibited exceptional activity in converting CO2 to CO, with a high Faradaic efficiency (> 95%) in a wide range of -1.9 ~ -2.4 V vs. Ag/Ag+ in the 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) electrolyte. The maximum CO partial current density of -125.40 mA cm-2 was obtained on this Ag nanofoam catalyst, representing 62% improvement over Ag(110)-dominant Ag electrode (-77.35 mA cm-2) at -2.4 V vs Ag/Ag+ in the [Bmim][BF4] electrolyte. Density functional theory calculations demonstrate that the Ag(111) crystal facet formed by in-situ electrolysis-deposition method prefers to adsorb [Bmim][BF4] which can stabilize the reaction intermediate, thereby weakening the reaction free energy and promoting CO2 electroreduction.