Hydrophobically made Ag nanoclusters with enhanced performance for CO2 aqueous electroreduction

Silver-containing material is one of the efficient electrocatalysts in converting CO2 into CO, but competing hydrogen evolution reaction (HER) in aqueous solutions results in poor energy efficiency. Here, Ag3 subnanoclusters with the structure sensitive to CO2 activation are in situ prepared by the cyclohexene oxidation. Hydrophobically modified Ag nanomaterials with an average particle size from 1.0 to 3.3 nm are water-repulsive, organic-soluble, and composited of the Ag3 cluster units, possessing the electron donation and strong chemical adsorption of CO2. In the electroreduction of CO2, a high mass activity about 10,200 A cm−2 gAg−1 is achieved for CO production at −1.4 V vs. reverse hydrogen electrode (RHE) on Ag nanoclusters with the external size of 1.9 nm, exhibiting 20 times higher than commercial Ag nanoparticles (diameters of 60–120 nm). Electrochemical tests in flow cells show an excellent mass activity of 55,000 A cm−2 gAg−1 with a large current density of around 30 mA cm−2 for the CO production at −0.71 V vs. RHE, much higher than the previously reported Ag catalysts. Hydrophobically made Ag3 subnanoclusters facilitate the CO2 electroreduction to CO in aqueous solutions through accelerating the electron donation and suppressing the side reaction of water reduction.