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 ([Bmim][PF₆])-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-mTriz 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.