Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active‐Site Distance in LnCu₆ Clusters

Abstract Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water‐soluble heterometallic clusters LnCu₆, abbreviated as LnCu₆‐AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu₆‐IM (Ln = La and Nd; IM = Imidazole), and LnCu₆‐IDA (Ln = Nd; H₂IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu²⁺ ions around one Ln³⁺ ion in LnCu₆, with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu₆ clusters exhibit different OER activities with remarkable turnover frequency of 135 s⁻¹ for NdCu₆‐AC, 79 s⁻¹ for NdCu₆‐IM and 32 s⁻¹ for NdCu₆‐IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active‐site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.