Direct imaging of light-element impurities in graphene reveals triple-coordinated oxygen

Abstract

Along with hydrogen, carbon, nitrogen and oxygen are the arguably most important elements for organic chemistry. Due to their rich variety of possible bonding configurations, they can form a staggering number of compounds. Here, we present a detailed analysis of nitrogen and oxygen bonding configurations in a defective carbon (graphene) lattice. Using aberration-corrected scanning transmission electron microscopy and single-atom electron energy loss spectroscopy, we directly imaged oxygen atoms in graphene oxide, as well as nitrogen atoms implanted into graphene. The collected data allows us to compare nitrogen and oxygen bonding configurations, showing clear differences between the two elements. As expected, nitrogen forms either two or three bonds with neighboring carbon atoms, with three bonds being the preferred configuration. Oxygen, by contrast, tends to bind with only two carbon atoms. Remarkably, however, triple-coordinated oxygen with three carbon neighbors is also observed, a configuration that is exceedingly rare in organic compounds.

Advances and Trends in Chemically Doped Graphene

“…For instance, researchers have directly observed nitrogen and oxygen atoms in N-doped graphene lattice and graphene oxide, respectively, along with their chemical forms via atomic resolution imaging (Figure 3c,d). [99] (Surprisingly, oxygen bound with three carbon atoms was also visualized, which had been rarely www.advancedsciencenews.com www.advmatinterfaces.de…”

“…[64] Recently, Hofer et al demonstrated nitrogen doping by irradiating nitrogen ions onto graphene on a TEM grid, and atomic resolution imaging confirmed that the doped nitrogen prefers to bind with three carbon atoms (graphitic form). [99] Based on these observations from different research groups, high-quality tunable nitrogen doping of graphene is possible; and particular bonding configurations, a large continuous area, and single-layer thickness can be achieved by controlling the synthesis parameters such as, the growth temperature, growth duration, precursor sublimation temperature (for solid precursors only), and even by laser deposition and ion implantation methods.…”

Recent advances in defect electrocatalysts: Preparation and characterization

“…1B, Yao and co-workers observed structural defects with different combinations (e.g., pentagons, heptagons and octagons), which mainly dominated on the hole-edge defects, while the regular hexagonal graphene structure dominated the main region of the carbon material [34]. Recently, Hofer and co-workers proposed an AC-TEM method for the direct visualization of triple-coordinated oxygen in graphene [140]. In addition, other kinds of defects, such as oxygen defects, have also been visualized by AC-TEM [141][142][143].…”

Molecular dynamics study of the pore formation in single layer graphene oxide by a thermal reduction process

“…31 The formation of triplecoordinated oxygen should not surprise as this configuration was already proven to exist both theoretically and experimentally in graphene. 41,42 When there are two initial zig-zag lines of oxygens, the resulting pore area is minimal (Fig. 3c), although in some cases, very small holes appear as in Panel II of Fig.…”