Sub-5 nm Cu Clusters for Efficient CO(2)-to-C(2)H(4) Conversion: Synergistic Microstructure and Catalytic Microenvironment.

The electrochemical CO reduction reaction (CORR) is one of the most promising pathways to achieving carbon neutrality. However, in acidic electrolytes, the CORR tends to suffer from competitive hydrogen evolution side reactions. Alkaline electrolytes are typically employed to suppress side reactions and promote the formation of valuable multicarbon (C) products (e.g., ethylene(CH)). In this study, we fabricated surface-loaded copper cluster catalysts with particle sizes below 5 nm by magnetron sputtering and inert gas condensation in combination with cluster beam deposition. This approach enabled precise control over the catalyst surface structure, allowing for in-depth investigation of the synergistic effects between the catalyst microstructure and its catalytic microenvironment. We demonstrate that the Faradaic efficiency (FE) for CO-to-CH conversion exceeds 50% across a broad current density range of 50 to 180 mA cm in a flow cell using 1 M KOH electrolyte. Compared with a pristine Cu/PTFE catalyst, the optimized Cu cluster catalyst not only exhibits a significant enhancement in FE but also expands the effective current density range. Furthermore, finite element simulations combined with Raman spectroscopy reveal synergistic interactions among interfacial species (e.g., *CO, OH, and K). Therefore, this study proposes a general strategy to regulate the dynamic evolution of catalytic interfaces through an initial nanostructure design, thereby opening a promising avenue for the selective conversion of CO to ethylene.