One-Step Rapid and Facile Synthesis of Subnanometer-Sized Pd6(C12H25S)11 Clusters with Ultra-High Catalytic Activity for 4-Nitrophenol Reduction

Palladium has aroused multitudinous concerns in recent years because of its highly catalytic activity with applications in many reactions. However, the synthesis of atomically precise Pd nanoclusters (Pd NCs) under mild conditions is still challenging. Here, a new facile method is developed to synthesize subnanometer-sized Pd clusters with the molecular formula of Pd-6(C12H25S)(11) under very mild conditions. The composition, morphology, and optical properties of the Pd6 clusters are characterized by MS, XPS, HRTEM, FT-IR, and UV-vis spectroscopy. The Pd NCs loaded on carbon black show an ultrahigh catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). After annealing treatment, the Pd NCs can catalyze the reduction of 4-NP to 4-AP with a 100% conversion in only 0.5 min, which is the highest efficiency so far among the reported Pd-based catalysts. The significantly enhanced catalytic activity can be ascribed to the large fraction of Pd atoms on the surface of subnanoclusters with low coordination and the clean surface after the removal of ligands. The present work not only provides a facile method for synthesizing ultrasmall metal clusters but also indicates that subnanometer-sized Pd clusters can be used as highly efficient catalyst for the degradation of environmental pollutants.