Mechanistic insights into CO2 reduction to C2 products on Cu3Zn surfaces: the role of stepped surfaces and Zn atoms

Abstract

The electrochemical reduction of CO₂ is a key technology for converting CO₂ into valuable chemicals and fuels, addressing both environmental and energy challenges. In this study, we employ density functional theory (DFT) with an explicit solvent model to investigate the mechanisms of CO₂ reduction to C₂ products on CuZn alloy surfaces with a 3 : 1 Cu-to-Zn ratio (Cu₃Zn). We investigate how stepped surface features and the presence of Zn influence the reaction pathways. Our simulations reveal that both surface facets and Zn play significant roles in stabilizing key reaction intermediates, facilitating C–C coupling, and steering selectivity between ethanol and ethylene. Specifically, stepped surfaces, particularly the (221) facet, exhibit enhanced reactivity and selectivity for ethanol due to the combined effects of Zn and the stepped surface. These factors promote the *CO–*CH coupling reaction and stabilize *CH₃CH₂O, leading to ethanol more effectively than *CH₂CH₂OH, which results in ethylene. In contrast, the flat (111) surface, which lacks these stepped features, tends to favor ethylene formation through a different reaction pathway. Overall, this study provides valuable insights into how stepped surfaces and Zn affect ethanol and ethylene selectivity in the Cu₃Zn alloy. These insights are crucial for designing more efficient and selective catalysts for producing valuable C₂ chemicals.