Preserving Molecular Tuning for Enhanced Electrocatalytic CO2‐to‐Ethanol Conversion

Modifying catalyst surface with small molecular‐additives presents a promising avenue for enhancing electrocatalytic performance. However, challenges arise in preserving the molecular‐additives and maximizing their tuning effect, particularly at high current‐densities. Herein, we develop an effective strategy to preserve the molecular‐additives on electrode surface by applying a thin protective layer. Taking 4‐dimethylaminopyridine (DMAP) as an example of a molecular‐additive, the hydrophobic protection layer on top of the DMAP‐functionalized Cu‐catalyst effectively prevents its leaching during CO2 electroreduction (CO2R). Consequently, the confined DMAP molecules substantially promote the CO2‐to‐multicarbon conversion at low overpotentials. For instance, at a potential as low as ‐0.47 V vs. reversible hydrogen electrode, the DMAP‐functionalized Cu exhibits over 80% selectivity towards multi‐carbon products, while the pristine Cu shows only ~35% selectivity for multi‐carbon products. Notably, ethanol appears as the primary product on DMAP‐functionalized Cu, with selectivity approaching 50% at a high current density of 400 mA cm−2. Detailed kinetic analysis, in‐situ spectroscopies, and theoretical calculations indicate that DMAP‐induced electron accumulations on surface Cu‐sites decrease the reaction energy for C‐C coupling. Additionally, the interactions between DMAP and oxygenated intermediates facilitate the ethanol formation pathway in CO2R. Overall, this study showcases an effective strategy to guide future endeavors involving molecular tuning effects.