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

Electrochemical reduction of CO is a promising approach to convert CO 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 CO affinity to regulate Ag catalyst for promoting electrochemical reduction of CO 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 CO to carbon monoxide (CO). This Ag-m-Triz exhibits excellent performance for CO reduction with a high CO Faradaic efficiency (FE) of 99.2% and CO partial current density of 85.0 mA cm 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][PF])-65 wt% acetonitrile (AcN)-5 wt% HO, 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 CO 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 CO to CO. This research provides a facile way to regulate electrocatalysts for efficient CO reduction by introducing functionalized molecules.