Ratio Of Reduced Graphene Oxide Research Articles

Construction of BiOCl/reduced graphene oxide nanocomposites heterojunction with abundant oxygen vacancies for efficient photocatalytic organic pollutant removal

Precisely manipulating defects in semiconductor is an effective way to improve their photocatalytic activity. In this work, bismuth oxychloride (BiOCl)/reduced graphene oxide (RGO) nanocomposites with abundant oxygen vacancies (OVs) are successfully constructed by a facile solvothermal method. BiOCl nanosheets are uniformly distributed on the RGO with superior conductivity. The RGO served as a pivotal charge transmission bridge substantially accelerates the transfer of photogenerated charge carriers, resulting in the improvement of the charge separation efficiency. The abundant oxygen vacancies in BiOCl/RGO nanocomposites increase light harvesting and enhance the adsorption of O2 to promote the formation of superoxide free radicals (·O2−). By virtue of these merits, the unique BiOCl/RGO nanocomposite shows excellent degradation efficiency. When the mass ratio of RGO was 2 %, 99.07 % of 20 mg/L(100 mL) methyl orange (MO) was removed after 80 min, which was much higher than that of pure BiOCl.

Photocatalytic degradation of antibiotic drug and dye pollutants under visible-light irradiation by reduced graphene oxide decorated MoO3/TiO2 nanocomposite

This study explored the effect of reduced graphene oxide (RGO) amount (1, 3, and 5 wt%) loading on the MoO3/TiO2 nanocomposite (Gr1/MoO3/TiO2 NCs, Gr3/MoO3/TiO2 NCs, and Gr5/MoO3/TiO2 NCs) for their photocatalytic activity against the Tetracycline (TC) antibiotic drug and Rhodamine B (RhB) dye under visible light illumination and compared it with the MoO3/TiO2 nanocomposite. Crystallite sizes of MoO3/TiO2 NCs, Gr1/MoO3/TiO2 NCs, Gr3/MoO3/TiO2 NCs, and Gr5/MoO3/TiO2 NCs are 17.69 nm, 16.24 nm, 12.64 nm, and 11.74 nm, respectively, with energy band gaps of 2.72 eV, 2.59 eV, 2.49 eV, and 2.38 eV correspondingly. The photocatalytic performance of the nanocomposites was revealed to be highly affected by the weight ratio of RGO on MoO3–TiO2. The results showed that about 98% of RhB and 94% of TC drug were photodegraded under visible light irradiation during the 60 min and 80 min respectively. RhB and TC drug photocatalysis degradation showed pseudo-first-order reaction kinetics, with order rate constants of 0.06435 min−1 and 0.0351 min−1, respectively. By electrostatic interactions, the stacked MoO3 being bound to the surface of TiO2 nanoparticles and concurrently anchored onto graphene nanosheets through π–π stacking. In addition, the inclusion of reduced graphene oxide nanosheets was shown to enhance photocatalytic activity. The mechanism was also portrayed: the synergetic (interfacial) interaction of the graphene sheets and the MoO3/TiO2 was responsible for the excellent photo-degradation impact of the RhB dye and the TC drug pollutants through the Gr/MoO3/TiO2. Furthermore, the MoO3/TiO2 has been used as a migration vehicle for the visible light carrier, while a high surface area and the number of active sites of the reduced graphene sheet enhanced the photocatalytic activity.

Nitrogen and nitrogen-sulfur doped graphene nanosheets for efficient hydrogen productions for HER studies

Carbon based electrocatalysts are promising candidates to achieve the production of hydrogen energy in a sustainable wayby simple water splitting technique. Thermally treated reduced graphene oxide (RGO) and N–S doped RGO employing urea and thiourea as electrocatalysts for hydrogen evolution reaction (HER). The performance of electrochemical HER has been thoroughly examined via linear sweep voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Furthermore, the Raman ID/IG ratio of RGO, N-RGO and NS-RGO were found to be 1.43, 1.10 and 1.11 respectively. From electrochemical HER analysis, we found that the NS-doped RGO exposed the low overpotential, low Tafel slope and low solution resistance value of 211 mV, 197 mV/dec and 0.34 Ω respectively. In addition, the chronoamperometry study revealed, the electrocatalyst NS-RGO showed an excellent stability (81.3% retention) with low 211 mV and remained unchanged for more than 16 h. Therefore, this work concludes that heteroatom dopant participate in improving electrocatalytic HER action.

Controllable thermal treatment of reduced graphene oxide for tunable electromagnetic wave absorption performance

The complex process of reduced graphene oxide (RGO) preparation hindered its merits of lightweight, high surface area, and notable dielectric loss in electromagnetic (EM) wave absorption performance. This work introduced a controllable ethanol-assisted hydrothermal and annealing treatment to simplify the preparation of RGO with improved agglomeration and achieved tunable EM wave absorption performance. Among series of RGO materials fabricated with different annealing temperatures, the optimized RGO achieves a strong reflection loss of −49.9 dB with a thickness of 3.9 mm, and a broad effective absorption bandwidth of 7.65 GHz with a thickness of 3.1 mm based on a 2 wt% filler content in the matrix. The vacancy defect density and C/O ratio of RGO were demonstrated to be correlated to the behavior of conductive loss and polarization relaxation for RGO and the interface reflection of EM wave. This controllable thermal treatment successfully enabled the simple preparation of RGO with reduced agglomeration and tunable EM wave absorption and effectively contributed to fabricating other carbon-based dielectric/magnetic materials as high-efficiency electromagnetic absorbers in future.

Improvement of Mechanical Properties of Cu/Graphene Composite by <i>In Site</i> Reduction and Matrix Alloying with Titanium

To reduce the agglomeration of graphene and enhance the interface bonding between reduced graphene oxide (RGO) and copper substrate, copper plating on the graphene surface was prepared by the in-situ reduction method. To improve the strength of the copper matrix, the microalloying strategy of adding titanium to the matrix was adopted. By changing the mass fraction of titanium in the matrix, the optimum ratio of RGO was obtained( Ti mass fraction was 5:1), and the tensile strength was maximized. The results show that RGO did not agglomerate obviously in the matrix. At the same time, the composite powder could be densified rapidly by spark plasma sintering (SPS), which could effectively protect the original distribution of the additive phase in the matrix. In this paper, Cu@RGO/Cu-Ti was prepared and the strengthening mechanism of the composites discussed, providing a new insights into the interface design and carbide formation mechanism of advanced graphene/copper composites with high mechanical properties.

Reduced Graphene Oxide-Supported Pt-Based Catalysts for PEM Fuel Cells with Enhanced Activity and Stability

Platinum (Pt)-based electrocatalysts supported by reduced graphene oxide (RGO) were synthesized using two different methods, namely: (i) a conventional two-step polyol process using RGO as the substrate, and (ii) a modified polyol process implicating the simultaneous reduction of a Pt nanoparticle precursor and graphene oxide (GO). The structure, morphology, and electrochemical performances of the obtained Pt/RGO catalysts were studied and compared with a reference Pt/carbon black Vulcan XC-72 (C) sample. It was shown that the Pt/RGO obtained by the optimized simultaneous reduction process had higher Pt utilization and electrochemically active surface area (EASA) values, and a better performance stability. The use of this catalyst at the cathode of a proton exchange membrane fuel cell (PEMFC) led to an increase in its maximum power density of up to 17%, and significantly enhanced its performance especially at high current densities. It is possible to conclude that the optimized synthesis procedure allows for a more uniform distribution of the Pt nanoparticles and ensures better binding of the particles to the surface of the support. The advantages of Pt/RGO synthesized in this way over conventional Pt/C are the high electrical conductivity and specific surface area provided by RGO, as well as a reduction in the percolation limit of the components of the electrocatalytic layer due to the high aspect ratio of RGO.

A potential application of polyethyleneimine-reduced graphene oxide nanocomposite sensing film coated on interdigitated electrode prepared from copper-clad for carbon dioxide detection

ABSTRACT In the present investigation, the response capabilities of the sensors fabricated by the drop-casting process were examined at room temperature. Polyethyleneimine (PEI) and synthesised reduced graphene oxide (RGO) with varied weight percentage are the materials selected for sensing Carbon dioxide (CO2). The novelty of the present work resembles the preparation of interdigitated electrodes (IDE) from patterning the copper clad. Four different varieties of sensors with a varied weight percentage of RGO in PEI were fabricated by drop-casting the sensitive films on prepared IDE. Capabilities of resistance over CO2 concentration, sensitivity, repeatability, measurements of response and recovery time were examined. It was found that appropriate weight ratio of RGO and PEI was critical for sensing response. A comparison between sensing responses of the fabricated sensors to CO2 under nitrogen (N2) was done. Addition to that appropriate sensing process was also analysed.

Low effective content of reduced graphene oxide/silver nanowire hybrids in epoxy composites with enhanced conductive properties

Hybrids of reduced graphene oxide (RGO) and silver nanowires (AgNWs) (RGO/AgNWs) with different ratios were prepared, characterized and added in epoxy resins as conductive fillers. Fourier-transform infrared spectroscopy results indicated graphene oxide had been reduced to RGO. X-ray diffraction patterns and scanning electron microscopy revealed that the hybrids could be formed by RGO and AgNWs, the graphene restacking might be prevented with RGO embedding in the unconnected spaces of AgNWs when the ratio of RGO: AgNWs was 1:2. Dynamic mechanical properties and electrical resistivities as well as thermal conductivity have been measured for the obtained epoxy nanocomposites. At low content of 0.6 wt% RGO/AgNWs (1:2), higher storage modulus of 2831 MPa, appropriate electrical resistivities of 4.8 $$\times \hspace{0.17em}$$ 108 Ω cm and thermal conductivity increased by 66.7% could be obtained for antistatic and thermal conductive applications.

Detection of Triacetone Triperoxide (TATP) Precursors with an Array of Sensors Based on MoS₂/RGO Composites.

Triacetone triperoxide (TATP) is a self-made explosive synthesized from the commonly used chemical acetone (C3H6O) and hydrogen peroxide (H2O2). As C3H6O and H2O2 are the precursors of TATP, their detection is very important due to the high risk of the presence of TATP. In order to detect the precursors of TATP effectively, hierarchical molybdenum disulfide/reduced graphene oxide (MoS2/RGO) composites were synthesized by a hydrothermal method, using two-dimensional reduced graphene oxide (RGO) as template. The effects of the ratio of RGO to raw materials for the synthesis of MoS2 on the morphology, structure, and gas sensing properties of the MoS2/RGO composites were studied. It was found that after optimization, the response to 50 ppm of H2O2 vapor was increased from 29.0% to 373.1%, achieving an increase of about 12 times. Meanwhile, all three sensors based on MoS2/RGO composites exhibited excellent anti-interference performance to ozone with strong oxidation. Furthermore, three sensors based on MoS2/RGO composites were fabricated into a simple sensor array, realizing discriminative detection of three target analytes in 14.5 s at room temperature. This work shows that the synergistic effect between two-dimensional RGO and MoS2 provides new possibilities for the development of high performance sensors.

Enhanced Electromagnetic Wave Absorption Performance of Co0.5Zn0.5 ZIF-Derived Binary Co/ZnO and RGO Composites

Composites of porous Co0.5Zn0.5 zeolitic imidazolate framework (CZ-ZIF)-derived binary Co/ZnO with reduced graphene oxide (RGO) have been prepared by a wet chemical method and carbonization process. CZ-ZIF-derived Co/ZnO microframes with diameter of about 250 nm were dispersed onto the surface of RGO nanosheets. The impedance matching of the composite could be adjusted by controlling the weight ratio of RGO to Co/ZnO microframes. Due to its porous structure, excellent impedance matching, and dielectric loss characteristics, the Co/ZnO/RGO composite exhibited maximum reflection loss (RL) of − 52.2 dB at 10.96 GHz. Coatings with thickness of 2.0 mm to 4.0 mm showed bandwidth of 5.6 GHz (from 8.72 GHz to 14.32 GHz) for RL of − 10 dB (90% absorption). Additionally, the amount of composite added into paraffin matrix was only 8 wt.%, less than for most electromagnetic (EM) wave absorbers in previous reports. Therefore, such Co/ZnO/RGO composites may be promising candidate EM wave absorbing materials.

Enhanced TiO2 nanorods photocatalysts with partially reduced graphene oxide for degrading aqueous hazardous pollutants.

Enhanced TiO2 nanorods (TNRs) with partially reduced graphene oxide (RGO) (designated as GT) were prepared for degrading aqueous hazardous pollutants. The degree of RGO oxidation had an important role in affecting the photoelectronic and photocatalytic activities of GT composites. The study examined the impact of the degree of RGO oxidation on the photocatalytic activities. The photocatalytic activity of the materials was investigated for degrading rhodamine b (RhB), methyl orange (MO), methylene blue (MB), and phenol by using ultraviolet (UV) light. The highest photocatalytic activity was observed when the atomic oxygen-to-carbon (O/C) ratio of RGO was 0.130 ± 0.003. This study suggested the photocatalytic performance was maximized by preserving a selected amount of the RGO oxygen-containing groups. The work reported in this study on optimizing the RGO-based TiO2 photocatalyst could serve as a promising approach for preparing and optimizing other types of carbon-based photocatalysts such as graphene-based CdS.

Noble metal-free RGO/TiO2 composite nanofiber with enhanced photocatalytic H2-production performance

1D reduced graphene oxide (RGO)/TiO2 nanocomposite fibers were fabricated by a facile two-step method. These samples demonstrated high photocatalytic H2-production activity from methanol aqueous solution, even without the aid of noble metal. When the ratio of RGO is 0.25wt%, the highest H2-production rate was achieved. It increased by 10 fold than bare TiO2, reaching 149μmolh−1g−1 with quantum efficiency (QE) of 0.75%. The reasons were as follows. Firstly, the RGO nanosheets acted as electron acceptors. Secondly, some shallow trap states at the surface or interface of TiO2 were created by the reduction of GO during calcination. Thirdly, the redox potential position of graphene/graphene− was suitable. Fourthly, RGO could efficiently promote the separation of photogenerated electron-hole pairs and significantly enhance the photocatalytic H2-production activity. This interpretation was corroborated by transient photocurrent response. The aforementioned marvelous results provided a probable solution to replace noble metals (such as Pt) by graphene as an effective cocatalyst.

Synthesis of hollow tubular reduced graphene oxide/SnO2 composites and their gas sensing properties

Structured, porous, and hollow tubular tin oxide (SnO2) and reduced graphene oxide (RGO) composites were synthesized through a combination of electrospinning and hydrothermal procedures. The morphology and structural features of the samples were analyzed and their sensing performance was tested. RGO/SnO2 composites exhibited a better sensing performance than SnO2. The optimum mass ratio of RGO in the composite was assessed as 1w%, leading to an excellent sensing response of 10.0–32.2ppm NO2 at a temperature of 150°C, approximately 10-fold that of SnO2. Thus, the enhancement of the gas sensing properties was attributed to the addition of RGO.

Remarkable enhancement in solar hydrogen generation from MoS2-RGO/ZnO composite photocatalyst by constructing a robust electron transport pathway

Exploiting an efficient and noble-metal-free cocatalyst is highly desired for photocatalytic H2 evolution from water. Here, we synthesized the MoS2-RGO/ZnO composite photocatalysts via a facile two-step solvothermal process. Through optimizing of the MoS2 and reduced graphene oxide (RGO) cocatalyst component proportion, the 0.75wt%5G95M/ZnO composite photocatalyst shows the highest H2 production rate of 288.4μmolg−1h−1 when the amount of MoS2-RGO is 0.75wt% and the weight ratio of RGO to MoS2 is 5:95, which is about 14.1 times higher than the pure ZnO. More importantly, the ternary MoS2-RGO/ZnO composite photocatalyst exhibits much higher H2 evolution activity than the Pt loaded ZnO under the same condition. The significant improvement in the H2 evolution activity is ascribed to the positive synergetic effect between MoS2 and RGO, which acts as a hydrogen evolution cocatalyst and a robust electron transport pathway, respectively. This study suggests that MoS2-RGO can serves as an efficient and noble-metal-free cocatalyst to improve the H2 production performance of ZnO by suppressing the electron-hole pairs recombination.

Tuning microstructure and surface chemistry of reduced graphene oxide by mild reduction

Reduced graphene oxide (RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing (0.852 nm) of graphene oxide (GO), the (002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The I D/I G ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp2 domains have smaller sizes and larger quantity. The content of sp2 bonded C in GO (36.93%, molar fraction) increases to 45.48%-72.92% (molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.

Fast and Energy Efficient Synthesis of ZnO@RGO and its Application in Ni–Zn Secondary Battery

ZnO with a uniform and complete coating of reduced graphene oxide (RGO) was prepared by a facile and rapid reaction using a solution synthesis scheme. A synthetic route that ZnO was first grown in situ on the GO surface and then reduced by NaBH4 was proposed, and an optimum coating structure was obtained by investigating the effect of precipitators, surfactant and additive amount of GO. After the reduction of NaBH4, 26.84% oxygen-containing groups were reduced and the weight ratio of RGO in the composite was 10.42 wt %, it was very close to the theoretical content of 11.8 wt %. The electrochemical measurements of ZnO@RGO negative electrode in the Zn–Ni secondary battery exhibited a stable cycle performance with a discharge capacity of 510 mAh g–1 after 300 cycles that it was 120 mAh g–1 higher than the capacity of bare ZnO. RGO layer effectively inhibited the direct contact between ZnO with the electrolyte and provided enough active area for the deposition of Zn which plays key roles to enhance the cycle ...

RGO/MnO2/polypyrrole ternary film electrode for supercapacitor

The binder-free electrode is expected for developing supercapacitor with high energy density. By using the good conductivity and forming-film property of PPy (Polypyrrole) and RGO (Reduced Graphene Oxide), as well as the high capacitance of MnO2 and PPy, [RGO/MnO2+PPy]10 ternary film electrode with high capacitance and good flexibility is prepared by a filtration-directed self-assembly technique. PPy nanoparticles (PPy) and MnO2 nanoparticles (MnO2) are uniformly embedded in RGO matrix constructed by the RGO nanosheets, decreasing the agglomeration of PPy and MnO2 and the reassembling of RGO nanosheets. RGO and PPy improve the conductivity, the ion diffusion rate and the charge-transfer resistance of the [RGO/MnO2+PPy]10 ternary film electrode, thus making it shows high capacitance and good flexibility. The [RGO/MnO2+PPy]10 ternary film electrode with a mass ratio of RGO:MnO2:PPy = 2:1:2 delivers the highest specific capacitance of 682 F g−1 at a scan rate of 5 mV s−1 and good cycling stability with about 86% retention of its original capacitance after 1000 consecutive cycles. The superior performance of [RGO/MnO2+PPy]10 ternary film electrode is probably ascribed to the novel film structure, the synergistic effect among PPy, RGO and MnO2 and the high packing density of PPy and MnO2.

Influence of reducing reagent combination in graphene oxide reduction

Large-scale production of high-quality graphene nanosheets has been considered to be an interesting and significant challenge. A new approach is reported regarding the fabrication of high-quality graphene nanosheets via chemical reduction with the combination of reducing reagents from graphene oxide (GO). High-conducting reduced GO (RGO) was provided with the combination of hydrazine hydrate and hydroiodic acid. RGO was characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman, thermo gravimetric analysis, atomic force microscopy and four-probe conductivity tester. Characterisation results indicated that oxygenated functional groups were removed from GO, and high graphitisation has occurred in GO reduction process. The electrical conductivity of RGO was considerably improved and the C/O ratio of RGO was higher than that prepared by single reducing reagent. Combination of hydrate hydrazine and hydroiodic acid have showed high reduction efficiency and good synergistic effect in GO reduction process. The findings in this work can promote research on prepared graphene-based nanosheets composites by a quick and effective processing technique.

Facile synthesis of TiO2-RGO composite with enhanced performance for the photocatalytic mineralization of organic pollutants.

Current research reports the synthesis of reduced graphene oxide (RGO)-TiO2 nanocomposite by in-situ redox method and graphene oxide by modified hummers method. The ratio of RGO and TiO2 in the composite was optimized to show best photocatalytic activity for the degradation of targeted pollutants. Optimized (1:10) RGO-TiO2 nanocomposite was characterized by various techniques viz. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller surface area (BET), Raman and diffuse reflectance spectroscopy (DRS) technique confirming successful formation of nanocomposite. XRD results confirm the presence of anatase phase in RGO-TiO2. Uniform dispersion of TiO2 nanoparticles on RGO could be seen from TEM images. The obtained results of (1:10) RGO-TiO2 showed five-fold and two-fold enhancement for the visible light and UV light, respectively, for the photocatalytic mineralization of methylene blue dye as compared to commercial Aeroxide P25 TiO2. The excellent photocatalytic mineralization activity of (1:10) RGO-TiO2 could be attributed to the enhanced surface area of composite as well as to its good electron sink capability. (1:10) RGO-TiO2 could be recycled easily and was found to be equally efficient even after the fourth cycle for the photocatalytic mineralization of methylene blue dye. The non-selectivity of synthesized composite was checked by the mineralization studies of oxalic acid.

Pt-functionalized reduced graphene oxide for excellent hydrogen sensing at room temperature

Cost effective and faster detection of H2 has always remained a challenge. We report synthesis of reduced graphene oxide (RGO)–Pt composite and its application as highly sensitive and selective H2 sensors at room temperature. Four samples by varying the ratio of RGO and Pt were prepared to test their sensing performance. The tests were carried out in inert (N2) ambience as well as air ambience. It was observed that the RGO:Pt (1:3) 1 h reduced sample demonstrated the best H2 sensing performance in terms of sensitivity, response time, and recovery time at room temperature. Its response varied from ∼19% (200 ppm) to 57% (5000 ppm) against H2 in air ambience. Also, the response time and recovery time of the RGO:Pt (1:3) sample were found to be as fast as 65 s and 230 s against 5000 ppm, respectively, in air ambience. In N2 ambience, the RGO:Pt (1:3) sample demonstrated the best response of −97% (500 ppm), but its recovery was found to be poor. The RGO–Pt composite formation was verified by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The detailed physics behind the sensing mechanisms have been explained and experimentally verified in this work.