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

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 LnCu(6), abbreviated as LnCu(6)-AC (Ln=La, Nd, Gd, Er, Yb; HAC=acetic acid), LnCu(6)-IM (Ln=La and Nd; IM=Imidazole), and LnCu(6)-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 Cu(2+)ions around one Ln(3+)ion in LnCu(6), with variations in CuCu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu6clustersexhibit 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 CuCu 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.