Kernel Geometry Transformation by Controlled S Incorporation in Cu₁₄ Nanocluster and Its Impact on Electrocatalysis

Cu nanoclusters have recently enabled the understanding of active sites and structural factors determining the electrocatalysis performance due to their atomic precision. However, the influence of structure geometry has so far remained elusive to Cu-nanoclusters-catalyzed electroreduction of CO₂. Here, we reported the controlled S incorporation based on the reductant dosage, achieving the geometry transformation of the Cu₈ kernel in the Cu₁₄ nanocluster while retaining the composition, outer motifs, and Cu valence state. Cu₁₄ with a parallelepiped kernel exhibits a distinct selectivity toward CH₄ (FE ∼51%), which contrasts with Cu₁₄-S containing a cubic kernel (mainly C₂₊ products, FE ∼33.8%). The electronic structures of Cu₁₄ nanoclusters are further revealed to be modulated by kernel geometry, altering the binding modes or energetics of the intermediates, as evidenced by in situ spectroscopy and theoretical calculation.