Boosting electrochemical reduction of CO2 to CO using molecule-regulated Ag nanoparticle in ionic liquids

Electrochemical reduction of CO2 is a promising approach to convert CO2 to high-valued chemicals and fuels. However, developing efficient electrocatalysts featuring desirable activity and selectivity is still a big challenge. In this work, a strategy of introducing functionalized molecules with desirable CO2 affinity to regulate Ag catalyst for promoting electrochemical reduction of CO2 was proposed. Specifically, 3-mercapto-1,2,4-triazole was introduced onto the Ag nanoparticle (Ag-m-Triz) for the first time to achieve selectively converting CO2 to carbon monoxide (CO). This Ag-m-Triz exhibits excellent performance for CO2 reduction with a high CO Faradaic efficiency (FECO) of 99.2% and CO partial current density of 85.0 mA/cm2 at -2.3 V vs. Ag/Ag+ in H-cell when combined with the ionic liquid-based electrolyte, 30 wt% 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6)-65 wt% acetonitrile (AcN)-5 wt% H2O, which is 2.5-fold higher than the current density in Ag-powder under the same condition. Mechanism studies confirm that the significantly improved performance of Ag-m-Triz originates from (i) the stronger adsorption ability of CO2 molecule and (ii) the weaker binding energy to form the COOH* intermediate on the surface of Ag-m-Triz compared with the Ag-powder catalyst, which boosts the conversion of CO2 to CO. This research provides a facile way to regulate electrocatalysts for efficient CO2 reduction by introducing functionalized molecules.