Visualization of Shallow‐Groove Expansion of Au(111) Facet under Methane Pyrolysis

Abstract Metallic catalyst facets are considered pivotal in determining the activity and selectivity of heterogeneous catalysis. However, the characterization of the dynamic evolution of metallic catalyst facets remains unsatisfactory, and the identification of evolved facets relies upon phenomenological criteria. Here, to understand the functional mechanism of catalyst facet formation, the dynamic evolution of the Au(111) facet is investigated by in situ transmission electron microscopy during methane pyrolysis. A shallow groove of a few atoms in depth is formed and expanded on the Au(111) facet. Density functional theory results show that the adsorption of carbon weakens the AuAu bonds, facilitating Au atom removal from the surface. Finally, a new flat Au(111) facet is formed. Thus, the facets undergo dynamic evolution during the actual pyrolytic reaction. This research may promote understanding of the catalytic mechanism and guide the design of the next generation of highly efficient catalysts.