Effect of Microwave Treatment in a High Pressure Microwave Reactor on Graphene Oxide Reduction Process—TEM, XRD, Raman, IR and Surface Electron Spectroscopic Studies

Abstract

Reduced graphene oxide (rGO) was prepared by chemical reduction of graphene oxide (GO) (with a modified Hummers method) in aqueous solutions of hydrazine (N2H4), formaldehyde (CH2O), formic acid (HCO2H) accompanied by a microwave treatment at 250 °C (MWT) by a high pressure microwave reactor (HPMWR) at 55 bar. The substrates and received products were investigated by TEM, XRD, Raman and IR spectroscopies, XPS, XAES and REELS. MWT assisted reduction using different agents resulted in rGOs of a large number of vacancy defects, smaller than at GO surface C sp3 defects, oxygen groups and interstitial water, interlayer distance and diameter of stacking nanostructures (flakes). The average number of flake layers obtained from XRD and REELS was consistent, being the smallest for CH2O and then increasing for HCO2H and N2H4. The number of layers in rGOs increases with decreasing content of vacancy, C sp3 defects, oxygen groups, water and flake diameter. MWT conditions facilitate formation of vacancies and additional hydroxyl, carbonyl and carboxyl groups at these vacancies, provide no remarkable modification of flake diameter, what results in more competitive penetration of reducing agent between the interstitial sites than via vacancies. MWT reduction of GO using a weak reducing agent (CH2O) provided rGO of 8 layers thickness.

Hydrothermal Synthesis of a Graphene‐based Composite Enabling the Fabrication of a Current Collector‐free Microsupercapacitor with Improved Energy Storage Performance

“…Figure 2A shows the XRD patterns of the three samples GO, rGO and optimized rGO‐PDA deposited on a glass substrate. The pattern of GO shows the (001) diffraction peak at 2θ=10.5° (corresponding to a d‐spacing of 0.842 nm), which is in good agreement with the literature values [25,26] . After hydrothermal treatment, this characteristic peak is no longer detected.…”

“…The pattern of GO shows the (001) diffraction peak at 2θ = 10.5°( corresponding to a d-spacing of 0.842 nm), which is in good agreement with the literature values. [25,26] After hydrothermal treatment, this characteristic peak is no longer detected. This result shows that for both samples, rGO and rGO-PDA, the graphene oxide has been successfully reduced by the hydrothermal method.…”

A molecularly imprinted photoelectrochemical sensor based on an rGO/MoSSe heterojunction for the detection of chlortetracycline

“…19 When MoSSe is recombined with rGO, not only the characteristic diffraction peaks of MoSSe are retained in the spectrum of rGO/MoSSe, but also the characteristic diffraction peaks of rGO appear at 2 θ = 28.0° (002), which is basically consistent with the two-dimensional layer stacking reported in the literature. 20 No diffraction peaks other than those mentioned above are observed, indicating that the formation of the composite did not affect the main crystal structure of MoSSe. The result indicates that the rGO/MoSSe composites have been successfully prepared.…”

Highly Ordered Graphene Polydopamine Composite Allowing Fast Motion of Cations: Toward a High‐Performance Microsupercapacitor

“…Characteristic diffraction peak (001) of GO appeared at 2𝜃 = 10.5°corresponding to a d-spacing of 0.842 nm, which is in good agreement with literature. [8,24,25] After the electrochemical reduction of GO in the absence of dopamine (DA), ERGO PBS , this peak (001) at 10.5 is no more detected, suggesting that the GO was fully reduced. Note that if dopamine molecules are present in the PBS solution a peak is still detected at 12.5°.…”