In-situ Characterization Of Surface Reconstruction Of Nanoporous Gold During The Catalytic Gas Phase Process

Surface reconstruction is a common phenomenon in gas-catalyzed reactions.In general,during the gas-phase catalytic reaction,because the surface contains a large number of low-coordination atoms and comes into contact with the reaction gas first,it is the main place for the catalytic reaction to occur,and the surface atoms are more easily induced to arrange and recombine.In this paper,nanoporous gold（NPG）was used as the research object,and in situ transmission electron microscopy and gas phase systems were used to study the surface reconstruction behavior of nanoporous gold in the gas phase catalytic process at the atomic scale,and their theoretical models were explored.The specific research contents and results are as follows:（1）The surface of NPG catalyzing the methane gas pyrolysis reaction gradually became regular,thereby forming a large number of stable and regular crystal planes,such as（111）and（200）.The theoretical calculation results show that the CH₄ pyrolysis intermediate can greatly affect the binding energy between Au atoms on the low coordination surface of NPG.All these atoms are easier to recombine to produce a more stable,highly coordinated structure.（2）The atomic layer on the surface of the NPG ligament would fall off layer by layer during the process of NPG catalyzing the reaction of N₂ and O₂.In situ observations revealed that the distance between the outermost atomic layer and the next outer atomic layer gradually increased,and as the reaction progressed to complete detachment.The second outer atomic layer became the new outermost atomic layer,and the distance from the new outer outer layer gradually increasesd to separate.This reconstruction process is repeated on the surface.