The porous Ag(111)-dominant Ag nanofoam catalysts were prepared by the in-situ electrolysis-deposition method in the IL electrolyte. This Ag nanofoam catalysts exhibited superior CO₂RR-to-CO performance of −125.40 mA cm⁻² j _CO and 99.37 % FE_CO than common Ag(100)-dominant Ag electrode due to the synergic effects of the dominant Ag(111) crystal facet and the [Bmim][BF₄] electrolyte.

Abstract

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 demonstrated 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.