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The most difficult aspect in electrochemical synthesis of graphene oxide (GO) is preventing graphite from disintegrating on the surface of the anode, which affects microstructural characteristics and yield. In this study, the effect of applied potential, electrolytic temperature, and types of electrolytic solution on yield, anode surface disintegration and microstructural properties of electrochemically synthesized GO has been investigated. The GO has been synthesized in an aqueous solution of 1 M piranha solution and sulfuric acid (${\mathrm{\text{H}}}_2{\mathrm{\text{SO}}}_4$) via electrochemical method by applying 24 V DC power source. After that, the GO was thermally reduced at around 650${\circ }^{}$C in a muffle furnace, and cooled down inside the muffle furnace. The yield, pH of the electrolytic solution, and anode surface disintegration all looked to be affected by the applied voltage and electrolyte temperature. Between the temperatures of 50${\circ }^{}$C and 70${\circ }^{}$C, the maximum yield was observed. During UV–Vis and XRD investigation, the absorbance, crystal structure, and interplanar distance appear to be unaffected by the reduction temperature, high voltage, electrolyte temperature and hydrogen peroxide addition. As demonstrated by Raman spectra, TEM, FE-SEM, AFM, and TGA analysis, high voltage, electrolyte temperature, and hydrogen peroxide addition have an important effect on the degree of defect, microstructure, and oxygen percentage, surface roughness and thermal stability of thermally reduced graphene oxide (TRGO).

The control over microstructural characteristics of graphene oxide (GO) is one of the most serious issues in the domain of graphene synthesis as this affects the graphene’s properties, and functionality. In this study, the primary objective is electrochemical synthesis graphene in the presence of magnetic field that is applied externally. During the synthesis process, the magnetic field was applied in a direction that was perpendicular to the applied potential. This causes the electrolyte to spin flow around the cell. Subsequently, the goal is to provide a comparative analysis between the microstructural characteristics of graphene that has been synthesized in situ and ex situ magnetic field. The cylindrical graphite was used as an anode, and a carbon electrode that had been recovered from a waste dry cell battery was used as a cathode. The pre-oxidized graphite was sonicated (synthesized under magnetic field, and without magnetic field) in sterilized water for 10min with a probe-type sonicator and thermally reduced at same temperature i.e., 850^∘C followed by furnace cooling. The findings of the Raman spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) characterizations indicate that the magnetic flux that was applied has a significant influence on the surface height and roughness, microstructure, and surface state, a structural disorder in comparison to when there was no magnetic field applied to the thermally reduced graphene oxide (rGO). On the other side, from the data obtained by XRD and TGA analysis, the applied magnetic field seems to have very little effect on phase, lattice parameter and thermal stability.

A high-quality, bulk synthesis of graphene that is inexpensive, and environmentally safe is highly desired because of the broad range of applications. In comparison to the chemical vapor deposition (CVD) method, epitaxial growth on silicon carbide, etc., the electrochemical approach is thought to be the most straightforward and eco-friendly way for the cost-effective bulk production of graphene from graphite. Moreover, the thermal reduction method appears to be a particularly cost-effective way to eliminate oxygen-containing functional groups when compared to chemical reduction. The yield of graphene is also impacted by the choice of cathode low-cost, which is extremely important and played a critical role during the synthesis process. In this work, we demonstrate a green, eco-friendly, and cost-effective electrochemical method for the synthesis of reduced graphene oxide (RGO) followed by thermal reduction. To accomplish electrochemical exfoliation for the graphene synthesis, a constant DC power of 65W ($\mathrm{\text{voltage}}=\sim 20$V and $\mathrm{\text{current}}=\sim 3.25$amp) has been supplied within an electrolytic cell that contains 2M of sulphuric acid as an electrolytic solution. The aluminium has been utilized as a cathode in place of the platinum, carbon cathode, etc. Moreover, to prepare the electrolytic solution and for the sonication process, sterilized water has been used in place of DI (deionized water). Thereafter, previously oxidized graphite oxide has been thermally reduced at a temperature of $800^{\circ }$C. The phase, crystallinity, and interatomic distance were investigated using X-Ray diffraction (XRD) analysis. X-Ray data show that the RGO crystal structure has been recovered following high-temperature annealing. The diffraction peak seems to be at $26.4^{\circ }$ with an interplaner distance of 3.48Å. The intensity of the defect, as measured by the $I_{\mathrm{\text{D}}}∕I_{\mathrm{\text{G}}}$ ratio (intensity ratio), was analyzed using Raman spectra, and the result of that investigation was found to be 0.196. The findings of the Raman study unambiguously reveal that the severity of the defects is judged to be on the lower end of the spectrum. The surface texture, microstructure, and elemental analysis were performed using atomic force microscopy (AFM), Field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), and EDX analysis. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to determine the number of oxygen-containing functional groups that existed in the RGO sample and their thermostability. The results of FTIR and TGA analysis clearly demonstrate that the reduction temperature has a major role in determining the proportion of oxygen that is present in the graphene. This study presents a large-scale, cost-effective, and eco-friendly graphene synthesis method for industrial applications.

This investigation aimed to explore the characteristics of reduced graphene oxide (rGO) through a comprehensive approach. The synthesis of graphene oxide (GO) began with a customized adaptation of the modified Hummer’s method, followed by subsequent chemical and thermal reduction processes. Chemical reduction involved the use of ascorbic acid, hydrazine hydrate, and sodium borohydride, while thermal reduction occurred at various temperatures in the presence of hydrogen. The study employed a diverse array of analytical techniques to unravel the structural and chemical intricacies of the material. X-ray diffraction (XRD) revealed significant changes indicative of structural transformations. Raman spectroscopy meticulously examined defects and layer formations. Scanning Electron Microscopy (SEM) visualized the evolutionary aspects of the material’s structure. UV–VIS spectroscopy is employed to analyze the optical bandgap of the sample, and the primary importance of this study lies in its application potential for solar cells.

Graphene platelets with a large scale have been synthesized by reduction of graphene oxide (GO) in aqueous solution of hydrazine hydrate under microwave irradiation (MWI). Microstructure of the graphene was characterized by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) together with the selected area electron diffraction (SAED). The electrochemical properties were evaluated by the analysis of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M Na₂SO₄ aqueous solution. The results show that the as-prepared materials consist of crumpled, few-layer (~ 3 nm) thick and electronically conductive graphitic sheets. The supercapacitors fabricated using this material possess a low equivalent series resistance (ESR) value ~ 1.6Ω and a high specific capacitance of 285 F ⋅ g^-1. In addition, the graphene reduced under a diverse duration of MWI displays a different interlayer spacing, extent of reduction, level of graphitization and specific capacitances. The duration of MWI and the treatment methods strongly affect the microstructure of graphene, and then dominate its electrochemical properties.

Gold nanoparticles (AuNPs)-decorated reduced graphene oxide (rGO) is a compelling material from both aspects of processing and functionality. This paper presents an alternative method to prepare and alter the optoelectronic properties of the AuNPs-rGO hybrid film. Au was sputtered for a duration of 0–60 s on graphene oxide (GO) film before subjected to thermal reduction at 700^∘C. The surface of rGO was decorated by spherical AuNPs with a mean particle size of around 10nm due to the solid-state dewetting process. The surface plasmon resonance (SPR) of AuNPs around 550nm was intense when the Au sputter duration exceeded 20s. Remarkably, the AuNPs layer retarded the de-oxygenation of GO during thermal annealing. The AuNPs-rGO hybrid film with long-duration Au sputtering exhibited low optical constants and thicker rGO film. The AuNPs also played the role in lowering the bandgap, increasing the lattice disorder and assisting the high-energy photon absorption in the thermally reduced rGO film. The sample of 30s and 40s Au sputtering was optimum to obtain the lowest sheet resistance of 59k$\mathrm{\Omega }$/sq and 56k$\mathrm{\Omega }$/sq, respectively. The sheet resistance was bargained between de-oxygenation retardation and doping by the AuNPs. Both samples of 30 s and 40 s Au sputtering were having a unique and satisfyingly strong absorption band around 260nm, 350nm and 555nm corresponding to $n-\pi$* transition, $\pi -\pi$* transition and SPR of AuNPs, respectively. Such properties are desirable in several applications such as a transparent electrode and optoelectronic sensor.

The requirement for restoring graphene’s electrical and thermal properties necessitates the implementation of reduction processes that remove oxygen atoms from the surface of graphene oxide sheets. Nevertheless, has been reported that the synthesis of graphene with a minimal oxygen content remains an obstacle in the field of graphene synthesis. The partial restoration of the initial graphene characteristics brought on by the recombination of carbon–carbon double bonds is primarily constrained by the existence of leftover oxygen atoms and lattice flaws. However, the absence of polar dioxide-based groups of function makes it difficult for the substance to disperse. Oxygen-containing functional groups also serve as reaction sites to bond active molecules to reduce graphene sheets. The literature describes many chemical methods to reduce graphene oxide for these reasons. It’s crucial to choose a chemical method that allows a thin modulation of residual oxygen content to tune the end product’s properties. This research demonstrates a synthesis mechanism for the low oxygen-containing thermally reduced graphene oxide (T-R-GO) by employing an electrochemical technique, which is then followed by thermal reduction. An environment-friendly, eco-friendly, simpler, and scalable electrochemical approach was initially used to synthesize graphite oxide. A steady power source of 24V DC (direct current) has been applied while the exfoliation process is being carried out. It has been noticed that there is a potential difference of 1V during the process of exfoliation. This difference is because the electrochemical cell creates a resistance, which results in a potential difference. Within the muffle furnace, the preoxidized graphite was subjected to a thermal reduction process at a temperature of 900${}^{\circ }$C. The microstructure, elemental composition, as well as C/O ratio (ratio of carbon and oxygen), was analyzed using field emission scanning electron microscopy (FESEM), transmission electron microscopy as well as energy dispersive X-ray (EDX). According to the results of EDX, reduction temperature serves a crucial role in the elimination of oxygen functionalities or their derived compounds. The surface topography and thermal stability analysis were analyzed using atomic force microscopy (AFM) and thermogravimetric analysis (TGA). The crystallinity and disorder in microstructure were investigated using X-ray powder diffraction (XRD) and Raman spectroscopy analysis. X-Ray data show that high-temperature annealing restored the RGO structure of the crystal. The interplanar distance is 3.824Å and the diffraction peak is 26.42${}^{\circ }$. Raman bands measured the defect’s I${}_D$/I${}_G$ ratio (intensity ratio) as 0.423. The Raman study shows that the flaws are minimal. This research offers a massive, economical, and environmentally friendly method for synthesizing graphene for use in industry.

Oxide precursors NdCaCo${}_{1-x}$Ni_xO_n ($x=0;0.2;0.4;0.6;0.8;1$) are obtained by the solid-state synthesis method at 1100${}^{\circ }$C. According to XRD analysis, the main components of these precursors are complex oxides with K₂NiF₄-like structure at $x\le 0.8$ and with rhombically distorted K₂NiF₄ structure at $x=1$. A thermal decomposition of these precursors in the mixture of CH₄/O${}_2=2$ at T $\ge$ 800${}^{\circ }$C results in the formation of dense metal-oxide nanocomposite particles. As-obtained nanocomposites demonstrated a considerable catalytic activity and selectivity in the reaction of partial oxidation of methane; their catalytic properties vary non-monotonously with Co/Ni ratio. The maximum CH₄ conversion and CO selectivity at 820${}^{\circ }$C is demonstrated by the composite comprising Nd₂O₃, CaO, NiO and Ni metal nanoparticles.

In this study, we provide electrochemical techniques for synthesizing thermally reduced graphene nanomaterial that have high potential, low defects, cost-effectiveness, and ecological sustainability. The electrochemical exfoliation is carried out by employing a 195 W DC (voltage = 60V and current = 3.25 A) power source at a maximum electrolyte temperature of about 92.5^∘C within the aqueous suspension of 2M of sulfuric acid (H₂${\text{SO}}_4)$. Thereafter, the synthesized nanomaterial was treated in the weak piranha [combination of sulfuric acid and hydrogen peroxide (H₂${\text{O}}_2)$] solution using an electrochemical technique inside the water bath sonicator at 80^∘C. X-ray diffraction (XRD) analysis shows the peak of diffraction to the (002) plane of the reduced graphene oxide (RGO) samples emerges at around 2$\theta =26.40^{\circ }$ and 26.56^∘ with an interplanar distance of 3.40 Å and 3.54 Å. According to the XRD data, after the high-temperature thermal reduction phase, the structure of the crystals and interplanar separation were recovered. The size of the crystallite of RGO produced under H₂SO₄ conditions was discovered to be greater than the crystallite size of graphene oxide produced under piranha solution conditions. The Raman analysis results show that the degree of disorder of the graphene synthesized within the H₂O₂ was higher than in comparison to the graphene synthesized in H₂SO₄. Field emission scanning electron microscopy (FE-SEM) results show that graphene synthesized in the presence of H₂O₂ has a thin and porous microstructure in comparison to H₂SO₄ with no significant effect on the presence of the availability of the C/O ratio. The atomic force microscopy (AFM) analysis indicates that the surface roughness of the graphene synthesized in the H₂O₂ was higher than that of the H₂SO₄. The Fourier transform infrared spectroscopy (FT-IR spectroscopy) analytical results show that the majority of the functional groups have been eliminated within the samples.