Constructing Active Sites in an Atomically Precise Silver Nanocluster toward Electrochemical Hydrogenation of...

Tailoring the electrocatalytic hydrogenation (ECH) performance of silver nanoclusters at the atomic level remains challenging. A mixed-ligand-protected superatomic silver nanocluster, Ag₂₈(PNP)₃(p-TBBT)₂₀ (Ag₂₈) (PNP= 2,6-bis(diphenylphosphino)pyridine; p-TBBT = 4-tert-butylthiophenol), was synthesized, and its structure was determined by single-crystal X-ray diffraction (SCXRD). Ag₂₈ consisted of a capped icosahedral Ag₁₈ kernel and accessible Ag(RS)₃ and Ag(RS)₂ motifs. Density functional theory calculations revealed that Ag₂₈ can be rationalized as a closed-shell 8-electron superatom with a jellium configuration of 1S²1P⁶. Remarkably, in comparison to other previously reported Ag_19/21/25/29 nanoclusters that possess similar metal kernels but disparate surface ligands or coordination structures, Ag₂₈ exhibited a significantly improved ECH performance for the conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bishydroxymethylfuran (BHMF), with excellent selectivity and faradaic efficiency toward BHMF reaching 100% and 91.1%, respectively. It has been demonstrated through experimental and theoretical calculations that the more accessible Ag(RS)₃ site, which is constructed using the steric hindrance effect of PNP on the surface of Ag₂₈, plays a crucial role in the improved catalytic performance. This work represents the inaugural application of atomically precise Ag nanoclusters to the ECH of HMF and paves a new avenue for the rational design and application of cluster catalysts for electrocatalytic hydrogenation.