Electron-Driven Metal Oxide Effusion and Graphene Gasification at Room Temperature

Metal oxide nanoparticles decorating graphene have attracted abundant interest in the scientific community owing to their significant application in various areas such as batteries, gas sensors, and photocatalysis. In addition, metal and metal oxide nanoparticles are of great interest for the etching of graphene, for example, to form nanoribbons, through gasification reactions. Hence it is important to have a good understanding of how nanoparticles interact with graphene. In this work we examine, in situ, the behavior of CuO and ZnO nanoparticles on graphene at room temperature while irradiated by electrons in a transmission electron microscope. ZnO is shown to etch graphene through gasification. In the gasification reaction C from graphene is released as CO or CO₂. We show that the reaction can occur at room temperature. Moreover, CuO and ZnO particles trapped within a graphene fold are shown to effuse out of a fold through small ruptures. The mass transport in the effusion process between the CuO and ZnO particles is fundamentally different. Mass transport for CuO occurs in an amorphous phase, while for ZnO mass transport occurs through the short-lived gliding of vacancies and dislocations. The work highlights the potential and wealth of electron beam driven chemical reactions of nanomaterials, even at room temperature.