High-efficient CO2 electrocatalysis over nanoporous Au film enabled by a combined pore engineering and ionic liquid-mediated approach

Abstract Electrochemical reduction of CO2 in ionic liquid-based electrolytes has received increasing interest due to its high selectivity and low overpotential. However, it has been plagued with a low yield rate due to the typically lower conductivity and higher viscosity of the electrolytes compared to aqueous electrolytes. Here, we report a rational electrode-electrolyte design by using nanoporous Au film electrode in combination with a 1-ethyl-3methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid-based binary electrolyte for electrochemical CO2 conversion. The CO2 reduction activity increases with the increase of the pore size of Au film, which is attributed to the increase in electrocatalytic surface area and enhancement in mass transport. Experimental and density functional theory studies show that EMIMBF4 ionic liquid increases the CO2 reduction activity and selectivity. Electrocatalytic reduction of CO2 with Faradaic efficiency up to 92.5% and mass activity of 3.0 A/g for CO is achieved at −0.55 V (vs RHE) in ionic liquid/water electrolyte.