Modulation of Oxygen Content in Graphene Surfaces Using Temperature-Programmed Reductive Annealing: Electron Paramagnetic Resonance and Electrochemical Study

Abstract

The oxidation level and properties of reduced graphene oxides (rGOs) were fine-tuned using temperature-programmed reductive annealing. rGOs were annealed at different temperatures (from 500 to 1000 °C) in hydrogen to modulate their oxidation levels. The surface of the rGOs was fully characterized using electron paramagnetic resonance backed by Raman, X-ray diffraction, and chemical analysis measurements. These experiments were used to study the changes in the surface of the rGO, its surface functionalities, and its defects as a function of the reduction temperature. In addition, electrochemical measurements to quantify the oxidation level of the rGOs offer a simple tool to correlate the properties of rGOs with their structure. Finally, we explored the effect of different levels of reduction on conductivity, capacitance, and surface reactivity. This research offers simple methodological techniques and routes to control and characterize the oxidation level of bulk quantities of rGO.

Effect of the GO Reduction Method on the Dielectric Properties, Electrical Conductivity and Crystalline Behavior of PEO/rGO Nanocomposites

“…This implies a reduction in the domain size of sp 2 bonded carbon atoms in the various rGO flakes, which may appear counter-intuitive. However, this increase of I D / I G with increasing extent of reduction was also observed by Zhang et al [36] for increasing treatment times with hydrazine hydrate and by Marciano et al [37] for increasing reduction temperatures during thermal reduction. The latter authors suggest that the removal of oxygen groups can cause dangling bonds that introduce sp 3 carbons.…”

Structure of graphene and its disorders: a review

“…However, in most cases the properties of graphene are supposed to be tailored for satisfying different requirements in industries. Tuning properties of graphene can be realized by several defects modulations approaches, including particle irradiation [326–328], thermal annealing [329,330], chemical reaction [331,332] and strain treatment [333,334], as summarized in Table 2.…”

“…Further, it is evidenced from Figure 18(e) that suspended graphene seems to be more sensitive to temperature than SiO 2 supported graphene, and the 2D blue-shift is more significant at higher temperature. In the annealing treatment of rGO [330], a smaller amount of free radicals was created when rGO was annealed at low-temperature. As the annealing temperature was increased from 500 to 1000 °C, the amount of oxygen groups on the graphene surface decreased.…”

Functionalized Carbon Dots on Graphene as Outstanding Non‐Metal Bifunctional Oxygen Electrocatalyst

“…Slight increase in the activity is shown at carbonization temperature of 800 °C with improved diffusion properties (compared to the untreated sample). However, it can be assumed that at 800 °C there are still some oxygen functionalities interfering with the performance as well as the low conversion ratio of graphitic N . At 1000 °C, on the other hand, despite the increase in rate of conversion with 60 mV reduction in overpotential (low oxygen and high graphitic N), the loss of sulfur‐containing groups (Table S4 and Figure S18, Supporting Information) results in no change in limiting current density, compared with 800 °C .…”