Mechanistic Insights into CO2 Reduction to C2 Products on Cu3Zn Surfaces: The Role of Stepped Surfaces and Zn Atoms

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 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.