Effects of Magnetoelectrochemical, Electrochemical Methods and Cyclic Thermal Annealing on Physicochemical and Optical Bandgap of Thermally Reduced Graphene Oxide

The controlled synthesis and subsequent processing of graphene are essential for customising its structural order, defect density, and functional characteristics for sophisticated technological applications. This study systematically investigates the synergistic effects of magnetoelectrochemical exfoliation in comparison of the traditional electrochemical method and cyclic thermal annealing at a fixed temperature on the physicochemical, optical, and microstructural characteristics of thermally reduced graphene oxide (TR-GO) for optoelectronic applications. Graphene oxide (GO) was synthesized using the anodic exfoliation of graphite (12B grade) under an externally applied magnetic field, employing magnetohydrodynamic mechanisms to enhance ion transport, exfoliation efficiency, and structural uniformity. The produced GO was subsequently thermally reduced and subjected to cyclic annealing at a constant temperature of 800 °C in an inert argon-rich atmosphere. It has been shown that both thermal and electrical factors play a significant role in determining the yield of TR-GO with maximum exfoliation at 60-75°C; exfoliation is stopped after 85°C, which is accompanied by a sharp decrease in electrolyte pH. Magnetoelectrolysis and cyclic annealing allow for precise control of defect density and surface shape. Structural analysis by X-ray diffraction (XRD) also reveals a peak at 2θ=26.40° with dspacing of 0.3386 nm. Exfoliation via magnetic fields without altering the core XRD features. Peak profile analysis suggests that Lorentzian fitting corresponds better with the experimental data when compared to Gaussian functions, although both provide consistent size trends as a function of temperature. It highlights that XRD and Raman spectroscopy complement one another, as XRD probes the vertical stacking quality of 2D materials, Raman probes lateral sp 2 domain dimensions and in-plane defect density. The effectiveness of a cyclic thermal annealing process at 800 °C to eliminate residual oxygen-containing functional groups that can be observed via FT-IR and heal the sp 2 hybridised network is demonstrated in conjunction with this novel proof of concept, allowing reduction in the optical bandgap down to values comparable with pristine graphene. Raman analysis shows that the (I D /I G ) ratio does not monotonically change but has a net effect of long-range defect integration, followed by structural recovery during the subsequent annealing cycles. Furthermore, magnetoelectrolysis results in TR-GO with reduced thickness, higher porosity and lower surface roughness compared to traditional samples, as shown by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Cyclic loading leads to nanoscale corrugations and varying surface roughness that represent a transition region between recovery of the surface layers and complete failure of the structure. These results provide a comprehensive basis for tailoring the 3D morphology of TR-GO for enhanced microelectronic applications.