Definitive Insight into the Graphite Oxide Reduction Mechanism by Deuterium Labeling

Abstract

The reduction of graphite oxide is one of the most important reactions in the production of graphene in gram quantities. The mechanisms of these widely used reactions are poorly understood. The mechanism of the chemical reduction of two different graphite oxides prepared by the chlorate (Hofmann method) and permanganate methods (Hummers method) has been investigated. Three different reduction agents, lithium tetrahydridoaluminate, sodium tetrahydridoborate, and lithium tetrahydridoborate, as well as their deuterated counterparts, were used for the reduction of graphite oxide. Reduced graphite oxides were analyzed by scanning electron microscopy, energy‐dispersive spectroscopy, elemental combustion analysis, Raman spectroscopy, high‐resolution X‐ray photoelectron spectroscopy, and simultaneous thermal analysis. The concentration of boron incorporated into graphene was measured by prompt gamma activation analysis. Rutherford back‐scattering spectroscopy and elastic recoil detection analysis were used for the determination of the elemental composition, including deuterium concentration, as evidence of CH bond formation.

Laser modification of graphene oxide layers

“…The D band is defect induced Raman feature that originates from structural defects, edge effects and appearance of dangling sp 2 bonds breaking symmetry [26]. The G band is associated with the in plane stretching motion of sp 2 bonded carbon atoms in graphene [19,27,28] and the broad multi-peak with wavenumber above 2400 cm -2 is typical for multilayer graphene structures [29]. No significant changes are observed in the peaks shape and position after laser irradiation in Figure 3.…”

“…The H/O ratio in the pristine GO foil is ~0.43 and after the laser modification using energy density 6 mJ.cm -2 slightly increases to value ~0.53, this value then stays similar for all other used laser energy densities. Hydrogen is in GO generally present in the form of hydroxyl functional groups (the H/O ratio is ~1), carboxylic groups (H/O ~0.5) or epoxides (H/O ~0) [19] and we can assumed the presence of carboxyl groups in the used GO structure. The O and H concentration increases with increasing depth and the concentration of these two elements achieves the pristine sample values in the depth about 180 nm (see Fig.…”

Hydrogenation of Fluorographite and Fluorographene: An Easy Way to Produce Highly Hydrogenated Graphene

“…Unlike XPS, which cannot determine hydrogen atoms and probes only af ew surface layers, elemental-combustion analysisc an determine hydrogen concentration and average bulk composition. [26] In addition, this procedure removedf luorine atoms verye ffectively.M oreover,t he mosts ignificant advantage of these methods is that handlingo ft he alkali metal and liquid ammonia are avoided. Fluorographene was more reactivet han fluorographited ue to its highers urface area.…”

“…Several interesting properties, such as ferromagnetism, [7,8] tuneable band gaps, [9,10] reversible hydrogenation, [5,6] and fluorescence, [7] have been reported for graphene-based materials. [25] Other methods have been based on hydrogenation using complex hydrides, [26] in whichL iAlH 4 provedt ob eh ighly effective by yieldingt he highest degree of hydrogenation. Several hydrogenationp rocedures have been proposed for graphane preparation,i ncluding low-pressure H 2 plasma hydrogenation, [11,14] high-pressure hydrogenation, [15] and wet-chemistry Birch reactions.…”

The Structural and Compositional Changes of Graphene Oxide Induced by Irradiation With 500 keV Helium and Gallium Ions

“…The permanganate oxidation method (modified Hummers method) was used for graphene oxide preparation as cited in ref. . Shortly, 3 g of natural graphite powder (APS 2–15 μm) from Alfa Aesar company were mixed with concentrated H 2 SO 4 (360 mL), H 3 PO 4 (40 mL), and 18 g of KMnO 4 and this mixture was heated to 50 °C.…”