In Situ Nucleation‐Decoupled and Site‐Specific Incorporation of Å‐Scale Pores in Graphene Via Epoxidation

Abstract

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. Herein, epoxidation is introduced, which is the formation of nanosized epoxy clusters on the graphitic lattice as nucleation sites without forming pores. In situ gasification of clusters inside a transmission electron microscope shows that pores are generated precisely at the site of the clusters by surpassing an energy barrier of 1.3 eV. Binding energy predictions using ab initio calculations combined with the cluster nucleation theory reveal the structure of the epoxy clusters and indicate that the critical cluster is an epoxy dimer. Finally, it is shown that the cluster gasification can be manipulated to form Å‐scale pores which then effectively sieve gas molecules based on their size. This decoupled cluster nucleation and pore formation will likely pave the way for an independent control of pore size and density.

Selective Photonic Gasification of Strained Oxygen Clusters on Graphene for Tuning Pore Size in the Å Regime

“…This provides evidence of the absence of pores in the as-oxidized sample, as semiquinone groups can only be present in the presence of vacancy defects given the bonding requirement of C (which will be discussed later). 37,40 Another indication of oxidation came from the Raman data of oxidized single-layer graphene on Si/SiO 2 , which appeared similar to that for GO, marked by broad D and G peaks and a negligible 2D peak (Figure S6). 41 Next, we carried out room-temperature photonic gasification by exposing the as-oxidized sample to 3.2 eV of light (390 nm, 4 W cm −2 , 0.5 cm from the sample) for a short time (5 s, Figures S3 and S4).…”

“…In situ aberration-corrected transmission electron microscopy (AC-HRTEM) experiments have revealed that the clusters gasify to form pores with an energy barrier of 1.3 eV, and the pore size is limited by the size of the cluster. 37 Spectroscopic evidence has shown that ether groups manifest within the large epoxy clusters; however, their exact location has not been pinpointed. 37 Additionally, the role of the ether group in the gasification process and the resulting pore size has remained unclear.…”

“…37 Spectroscopic evidence has shown that ether groups manifest within the large epoxy clusters; however, their exact location has not been pinpointed. 37 Additionally, the role of the ether group in the gasification process and the resulting pore size has remained unclear. Herein, we demonstrate that the ether group plays a critical role in regulating the size of the pore within the oxygen cluster.…”

“…They form energy-minimizing clusters, which are helped by their low barrier for diffusion (0.7 eV) on the graphitic lattice, that subsequently bind together in order to reduce the net energy of the system . Clusters as small as epoxy dimers serve as stable nuclei for further growth into larger clusters . These clusters grow as cyclic epoxy trimers, starting out as linear chains that then coalesce to form larger clusters where the trimers are organized in a honeycomb superstructure (Scheme ).…”

“…Spectroscopic evidence has shown that ether groups manifest within the large epoxy clusters; however, their exact location has not been pinpointed . Additionally, the role of the ether group in the gasification process and the resulting pore size has remained unclear.…”