Speaker
Description
Generating pores in graphene by decoupled nucleation and expansion is desired to achieve a fine control over the porosity and is desired to advance several applications. In situ studies of pore formation are particularly valuable, as they enable direct observation of the process while simultaneously allowing measurement of the associated properties within the same experimental setup.1
Herein, we present a nucleation-decoupled and site-specific pore engineering strategy based on the controlled epoxidation of graphene, where epoxy groups are grafted on graphene surface.2 The high-density (~10¹² cm⁻²) nanoscale epoxy clusters on highly oriented pyrolytic graphite (HOPG) were observed by low-temperature scanning tunneling microscopy (LTSTM). It reveals that these epoxy clusters act as stable pore precursors, exhibiting no carbon vacancy formation in the absence of external energy input. Upon introducing an energy stimulus via electron beam irradiation, the epoxy clusters are transformed into vacancy defects. Real-time evolution of this process was captured using aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) under an 80 keV electron beam with the maximum transferable energy (15.6 eV). A mathematical model describing the conversion of epoxy clusters to pores was developed, enabling extraction of the displacement energy (Ed) for carbon removal. Using the Seitz–Koehler formalism3 for relativistic electron–nucleus scattering, cross-sectional analysis yielded an average displacement energy of ~1.3 eV for functionalized carbon atoms within epoxy clusters, indicating significantly lower energy requirement compared to knockout energy of pristine graphene (~20 eV).4 This strategy enables pore formation to be confined strictly to the epoxidized regions, i.e., the clusters, thereby achieving precise site-specific pore generation. Additionally, it constrains pore growth, with the maximum pore size inherently limited by the dimensions of the epoxy cluster.