How Carbene Ligands Transform AuAg Alloy Nanoclusters for Electrocatalytic Urea Synthesis

Abstract

Metal nanoclusters stabilized by N‐heterocyclic carbene (NHC) ligands have attracted increasing interest for their special structures and diverse applications. However, developing synthetic strategies and extending the database of NHC‐protected nanoclusters are still challenging tasks. In this work, a novel and rapid synthetic method is developed to prepare AuAg alloy nanocluster ligated by carbene based on the reactivity of nanoclusters. The rod‐like carbene‐capped bimetal nanocluster, [Au13Ag12(PPh3)8(BMIm)2I8]SbF6 (Au13Ag12:BMIm), was achieved and characterized by a series of techniques. The alloy nanocluster consists of two vertex‐sharing icosahedrons and carbene ligands, phosphine ligands, and I atoms. Interestingly, the introduced carbene ligands show strong coordination capabilities with Au, enhancing the interaction between metal core and ligands. To the best of our knowledge, the carbene‐capped Au13Ag12:BMIm nanocluster is the first of its kind to show higher thermostability and higher sensitivity to light compared with the homogeneously capped analogue nanocluster ([Au13Ag12(PPh3)10I8]SbF6). Density functional theory calculations attribute these properties to a unique delocalization of electrons within the frontier orbitals. Finally, the Au13Ag12:BMIm anchored on NiFe‐LDH exhibits remarkable electrocatalytic activity in the electrosynthesis of urea from NO3− and CO2, achieving a urea production rate of 29.5 mmol gcat–1 h–1 with a Faradaic efficiency of 34% at ‐0.5 V (vs. RHE).