Quantitative electroreduction of CO2 to CO using Re-oxide doped Ag aerogels with surface-supported ionic liquids

This abstract figure illustrates the use of a novel Re-doped Ag aerogel, functionalized with a surface supported ionic liquid, achieving 100 % selectivity toward CO at elevated current densities while completely suppressing the hydrogen evolution reaction. Silver still faces significant challenges in the electrochemical reduction of CO 2 (eCO 2 RR) to CO under elevated current density with high energy input due to the intensified hydrogen evolution reaction. The doping of 2 mol% Re-oxide into Ag aerogel results in a significant decrease in the onset potential and a two-fold increase in the current density compared to a pure Ag aerogel (Ag 100 ), which tackles the issue. The effect is rationalized in terms of positively shifting the d -band center close to the Fermi energy level to change the density of local electronic states. Moreover, upon the adsorption of the ionic liquid (IL, 1-Allyl-3-methylimidazolium dicyanamide [AMIM][DCN]) onto the surface of Re-oxide doped Ag aerogel (Ag 98 Re 2 /IL), the current density increases to 320 mA/cm 2 at a low of −1.3 V vs. RHE with 96 % selectivity for CO formation in an alkaline medium using a flow cell electrolyzer, and maintains the selectivity above 92 % for up to 17 h using an H-cell electrolyzer. Density Functional Theory revealed that the adsorbed IL forms a highly conductive and hydrophobic layer on the aerogel surface, presumably decreasing the local H + concentration, greatly suppressing the hydrogen evolution reaction while enhancing the eCO 2 RR pathway and mitigating the mass transport issues typically associated with IL use. This work addressed the key challenges in massively producing CO from eCO 2 RR, offering a promising strategy for scalable and industrial CO generation.