In Situ Study On The Dynamic Evolution Of Gold Surface Defects In N₂/O₂ Atmosphere

Nanocatalysts often exhibit excellent catalytic activity due to their high surface activity and high specific surface area.Gold is considered an inert metal,but when its size is reduced to nanoscale,it also exhibits extraordinary low-temperature oxidation catalytic activity.However,from the perspective of reaction mechanism,the source of oxidation activity of nano gold under mild conditions is a very complex topic,and the main source of its oxidation activity is still controversial,and further research is needed.Studying the surface structure evolution at the atomic scale during the nitrogen oxidation reaction catalyzed by nano gold can provide direct evidence of the source of gold oxidation activity,provide important information for understanding the mechanism of gold oxidation activity,and also provide scientific basis for regulating the design of nitrogen oxidation catalysts under mild conditions.This article investigates the structural evolution of nano gold catalysts in nitrogen oxidation reactions at the atomic scale using in-situ electron microscopy technology,and analyzes the sources of oxidation activity.The results are as follows:（1）During the catalytic oxidation of nitrogen at room temperature,the distortion of nano porous gold ligaments,especially surface stretching,is beneficial for the adsorption and dissociation of oxygen,resulting in the formation of active oxygen atoms that react with nitrogen to generate N₂O.Theoretical calculations indicate that under room temperature conditions,the tensile strain on the surface of nano porous gold changes the surface charge distribution,which is conducive to the adsorption and dissociation of oxygen,generating active oxygen atoms and reacting with nitrogen.（2）In a mixed gas environment of N₂ and O₂,the surface of fivefold twin nanoparticles（NPs）with high internal stress exhibits highly active surface behavior,and their surface interfaces undergo significant surface reconstruction,indicating that defects（lattice distortion）on the surface of gold NPs are an important source of their oxidation activity.After introducing Ag atoms into gold NPs,the distortion of the surface interface and the fivefold twin NPs further increases,resulting in better activity exhibited during the reaction process and more intense reconstruction behavior.