Atomic-level engineering of single Ag1+ site distribution on titanium–oxo cluster surfaces to boost CO2 electroreduction

Precise control over the distribution of active metal sites on catalyst surfaces is essential for maximizing catalytic efficiency. Addressing the limitations of traditional cluster catalysts with core-embedded catalytic sites, this work presents a strategy to position catalytic sites on the surfaces of oxide clusters. We utilize a calixarene-stabilized titanium–oxo cluster (Ti₁₂L₆) as a scaffold to anchor Ag¹⁺ in situ, forming the unique nanocluster Ti₁₂Ag_4.5 with six surface-exposed Ag¹⁺ sites. The in situ transformation from Ti₁₂L₆ into Ti₁₂Ag_4.5 clusters was traced through mass spectrometry, revealing a solvent-mediated dynamic process of disintegration and reassembly of the Ti₁₂L₆ macrocycle. The unique Ti₁₂Ag_4.5 cluster, featuring a surface-exposed catalytic site configuration, efficiently catalyzes the electroreduction of CO₂ to CO over a broad potential window, achieving CO faradaic efficiencies exceeding 82.0% between −0.4 V and −1.8 V. Its catalytic performance surpasses that of bimetallic Ti₂Ag₂, which features a more conventional design with Ag¹⁺ sites embedded within the cluster. Theoretical calculations indicate that the synergy between the titanium–oxo support and the single Ag¹⁺ sites lowers the activation energy, facilitating the formation of the *COOH intermediate. This work reveals that engineered interactions between active surface metal and the oxide support could amplify catalytic activity, potentially defining a new paradigm in catalyst design.