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

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 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.