Selectivity of Electrochemical CO₂ Reduction toward Ethanol and Ethylene: The Key Role of Surface-Active Hydrogen

Electrochemical reduction offers promise for converting CO2 into a range of hydrocarbons and oxygenates, yet the production of alcohols remains an ongoing challenge. The elusive understanding of the underlying factors governing alcohol selectivity has hindered the optimization of alcohol yields. Herein, we clarify the insight mechanism of enhanced ethanol selectivity over modified copper catalysts via explicit solvent models combined with slow-growth molecular dynamics. The surface-active hydrogen, introduced by guest metals and high-facet atomic arrangements, emerges as a pivotal factor in promoting the kinetics of surface-coupled hydrogenation of intermediates while indirectly inhibiting solvent hydrogenation of intermediates. This intricate interplay unlocks the reaction pathway toward ethanol products. Moreover, the evaluation of hydrogen activity allows rapid screening of a Cu-based catalyst aiming for alcohols, and the qualitative agreement with available experimental results, in turn, confirms the rationality of the mechanism. This study discloses that promoting surface-coupled hydrogenation and suppressing solvent hydrogenation are two fundamental strategies to improve alcohol selectivity, which provides insights into the design of catalytic systems for electrochemical CO2 reduction with desired products.