Top-down synthesis strategies: Maximum noble-metal atom efficiency in catalytic materials

Top-down synthesis has been used to prepare catalytic materials with nanometer sizes, but fabricating atomically dispersed metal catalysts remains a challenge because surface single metal atoms are prone to aggregation or coalescence. A top-down strategy is used to synthesize atomically dispersed metal catalysts, based on supported Ag nanoparticles. The changes of the geometric and electronic structures of the Ag atoms during the top-down process are studied using the in situ synchrotron X-ray diffraction technique, ex situ X-ray absorption spectroscopy, and transmission electron microscopy. The experimental results, coupled with the density functional theory calculations, demonstrate that the electronic perturbation of the Ag frontier orbitals, induced by the Ag-O interactions at the perimeter of the metal-support interface, is the driving force of the top-down process. The top-down synthesis has two important functions: to increase the number of catalytic active sites and to facilitate the study of complex reaction mechanisms (e.g., formaldehyde oxidation) by developing single-site model catalysts. (C) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.