Effect of friction on oxidative graphite intercalation and high-quality graphene formation

Abstract

Oxidative wet-chemical delamination of graphene from graphite is expected to become a scalable production method. However, the formation process of the intermediate stage-1 graphite sulfate by sulfuric acid intercalation and its subsequent oxidation are poorly understood and lattice defect formation must be avoided. Here, we demonstrate film formation of micrometer-sized graphene flakes with lattice defects down to 0.02% and visualize the carbon lattice by transmission electron microscopy at atomic resolution. Interestingly, we find that only well-ordered, highly crystalline graphite delaminates into oxo-functionalized graphene, whereas other graphite grades do not form a proper stage-1 intercalate and revert back to graphite upon hydrolysis. Ab initio molecular dynamics simulations show that ideal stacking and electronic oxidation of the graphite layers significantly reduce the friction of the moving sulfuric acid molecules, thereby facilitating intercalation. Furthermore, the evaluation of the stability of oxo-species in graphite sulfate supports an oxidation mechanism that obviates intercalation of the oxidant.

Brodie's or Hummers’ Method: Oxidation Conditions Determine the Structure of Graphene Oxide

“…Consequently, the degree of oxidation is very similar for oxo‐G ref and oxo‐G B . In contrast, for oxo‐G 4 % the degree of functionalization is only about 4 %, and consequently a C content of about 86 % is found.…”

“…Upon washing the ionic strength is reduced, which triggers delamination of this oxo‐G by osmotic swelling. In addition, oxo‐G 4 % was synthesized from the intercalation compound graphite sulfate and aqueous treatment . Oxo‐G 4 % possesses, to a first approximation, 4 % of hydroxyl addends related to the number of C atoms .…”

“…In addition, oxo‐G 4 % was synthesized from the intercalation compound graphite sulfate and aqueous treatment . Oxo‐G 4 % possesses, to a first approximation, 4 % of hydroxyl addends related to the number of C atoms . Moreover, over‐oxidized graphene oxide (GO st ) was prepared as described in the literature …”

Selektive Funktionalisierung von Graphen an defektaktivierten Bereichen durch Arylazocarbonsäure‐tert‐butylester

“…In früheren Studien haben wir die Art der Gitterdefekte von oxo‐ S G/ S G und oxo‐ * G/ * G mittels Transmissionselektronenspektroskopie mit atomarer Auflösung visualisiert. Es handelt sich um Defekte mit wenigen fehlenden C‐Atomen (Fehlstellen), um vereinzelt auftretende Löcher mit einem Durchmesser von etwa 1 nm und in seltenen Fällen um ein ungeordnetes Kohlenstoffgitter ,…”

Structure Design and Composition Engineering of Carbon‐Based Nanomaterials for Lithium Energy Storage

“…The performance of the as‐prepared graphene varies between 100 and 1000 mAh g −1 when used as electrodes for LIBs, depending especially on the structural design, electrode processing, mass loading, and the way to assemble graphene sheets. Seiler et al found that only well‐ordered, highly crystalline graphite delaminates into oxo‐functionalized graphene, whereas other graphite grade reverts back to graphite during hydrolysis . The electronic oxidation significantly lowered the friction of sulfuric acid confined between layers, initiating the intercalation process.…”