Addition Of rGO Research Articles

Characteristics of reduced graphene oxide (rGO) mixed HVOF-sprayed nanostructured coatings

ABSTRACT High-velocity oxyfuel (HVOF) sprayed ceramic coatings possess less porosity and exceptional cohesive strength as compared to the air plasma sprayed ceramic coatings. In particular, the HVOF-sprayed tungsten carbide-cobalt (WC-Co) coatings have the disadvantage of unexpected brittle fracture. These coatings usually fail at higher levels of stress because of their lower fracture toughness that results due to decarburization occurring during the deposition of the coatings. In this work, the HVOF-sprayed nanostructured WC-25wt-%Co coatings have been investigated with and without the addition of rGO. It was found in the microstructure of 1.5% rGO-added WC-25wt-%Co coatings that the rGO has been pulled out from the matrix and wrapped in the fractured regions. It was also observed with an increasing percentage of rGO addition that the porosity in the WC-25wt-%Co coatings has been reduced due to a reduction in the number of pores.

Deciphering the role of rGO in tuning dielectric properties of Er2O3/ZnO/rGO nanocomposites synthesized via facile approach

The present research investigated the effect of reduced graphene oxide (rGO) integration with as-synthesized Er2O3/ZnO nanocomposites on dielectric properties. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and energy dispersive spectroscopy (EDS). Complex impedance spectroscopy was utilized to characterize dielectric relaxation phenomena in Er2O3/ZnO and Er2O3/ZnO/rGO nanocomposites. All the samples exhibit single relaxation phenomena which are ascribed to grain boundaries. The addition of rGO to Er2O3/ZnO nanocomposite results in the enhancement of dielectric response due to increased local field intensity caused by the formation of conducting-insulating interfaces. Furthermore, the AC conductivity of the Er2O3/ZnO/rGO is increased at higher frequencies due to the presence of free charge carriers in rGO. At higher frequencies, Er2O3/ZnO/rGO nanocomposite with increased concentration of ZnO exhibits a more stable dielectric constant with extremely low dielectric loss. Hence, the inclusion of rGO in Er2O3/ZnO nanocomposites makes it a novel prospective candidate in the field of energy storage devices.

Un estudio comparativo de diferentes compuestos de poli(3-hexiltiofeno)-carbono como capas transportadoras de huecos sobre la estabilidad de celdas solares de perovskita preparadas bajo condiciones ambientales

Hole transport layers (HTLs) play an important role in efficiency and stability of perovskite solar cells (PSCs).  Most of the highly efficient PSCs use spiro-OMeTAD doped with Li-TFSI as HTLs, which has to be prepared under inert atmosphere, because the hygroscopic feature of the lithium salt deteriorates the stability of PSCs under ambient conditions. In this work, we report a comparative study of the electrical and morphological properties of different poly(3-hexylthiophene) (P3HT) thin films: pristine, doped with FeCl3, and composites with carbon nanotubes (CNT) or reduced graphene oxide (rGO). Although the electrical conductivity of P3HT films is found to increase with any of those modification methods, the photovoltaic performance of PSCs is highly dependent on the modification agent. P3HT:FeCl3 reduces the photocurrent density of PSCs, while the addition of rGO in P3HT improves charge extraction and stability of PSCs. Furthermore, the insertion of conductive carbon paint between P3HT and the metal contact maintains the original efficiency of non-encapsulated PSCs after continuous illumination for 30 min. It is concluded that carbon modifications in P3HT based HTL can improve the stability of perovskite solar cells totally fabricated under ambient conditions.

Reduced graphene oxide influences morphology and thermal properties of silk/cellulose biocomposites

In recent decades, research into biomaterials such as silk or cellulose has rapidly expanded due to their abundance, low cost, and tunable morphological as well as physicochemical properties. Cellulose is appealing due to its crystalline and amorphous polymorphs while silk is attractive due to its tunable secondary structure formations which is made up of flexible protein fibers. When these two biomacromolecules are mixed, their properties can be modified by changing their material composition and fabrication methodology, e.g., solvent type, coagulation agent, and temperature. Reduced graphene oxide (rGO) can be used to increase molecular interactions and stabilization of natural polymers. In this study, we sought to determine how small amounts of rGO affect the carbohydrate crystallinity and protein secondary structure formation as well as physicochemical properties and how they affect overall ionic conductivity of cellulose-silk composites. Properties of fabricated silk and cellulose composites with and without rGO were investigated using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, X-Ray Scattering, Differential Scanning Calorimetry, Dielectric Relaxation Spectroscopy, and Thermogravimetric Analysis. Our results show that addition of rGO influenced morphological and thermal properties of cellulose-silk biocomposites, specifically through cellulose crystallinity and silk β-sheet content which further impacted ionic conductivity.

Hybrid material of α-Fe2O3 nanostructure with reduced graphene oxide: Enhanced dielectric and optical properties in relation to their composition and morphology

The enhancement in the optical and dielectric properties in advanced technologies demands the development of novel nanomaterials. The present study discusses the synthesis of iron oxide (α-Fe2O3) using chemical precipitation method and Hummer's modified method for reduced graphene oxide (rGO). A nanocomposite of both α-Fe2O3 and rGO is prepared by using sonication method which provide better interface between the ferromagnetic and ferroelectric materials. XRD and TGA studies were performed to confirm the structural changes and compositional phases in the samples. FT-IR analysis confirms the presence of the various functional groups in addition to phase purity of the samples and stretching vibration bands of Fe-O for α-Fe2O3 NPs. TEM images displays the illustrious dispersion of α-Fe2O3 NPs on the rGO sheet of synthesized NC. UV–Vis investigation reveals that sample has an optical gap of about 2.25 eV and that this value increases with rGO addition. The attributes of dielectric characteristics like dielectric constant (ε′), loss tangent (tan δ), and ac conductivity (σac) are examined at different frequencies. These important electrical and dielectric results obtained for NC with desirable properties make it advanced multifunctional material for electronic devices.

Engineering a conduction-consistent cardiac patch with rGO/PLCL electrospun nanofibrous membranes and human iPSC-derived cardiomyocytes.

The healthy human heart has special directional arrangement of cardiomyocytes and a unique electrical conduction system, which is critical for the maintenance of effective contractions. The precise arrangement of cardiomyocytes (CMs) along with conduction consistency between CMs is essential for enhancing the physiological accuracy of in vitro cardiac model systems. Here, we prepared aligned electrospun rGO/PLCL membranes using electrospinning technology to mimic the natural heart structure. The physical, chemical and biocompatible properties of the membranes were rigorously tested. We next assembled human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) on electrospun rGO/PLCL membranes in order to construct a myocardial muscle patch. The conduction consistency of cardiomyocytes on the patches were carefully recorded. We found that cells cultivated on the electrospun rGO/PLCL fibers presented with an ordered and arranged structure, excellent mechanical properties, oxidation resistance and effective guidance. The addition of rGO was found to be beneficial for the maturation and synchronous electrical conductivity of hiPSC-CMs within the cardiac patch. This study verified the possibility of using conduction-consistent cardiac patches to enhance drug screening and disease modeling applications. Implementation of such a system could one day lead to in vivo cardiac repair applications.

Supersonically sprayed self-aligned rGO nanosheets and ZnO/ZnMn2O4 nanowires for high-energy and high-power-density supercapacitors

• ZnO nanospheres and ZnMn 2 O 4 nanowires were produced by a hydrothermal method for supercapacitor applications • The MnSO 4 concentration was varied from 0.05 to 0.15 mol/L to identify the electrode with the highest capacitance. • The optimal electrode exhibited a specific capacitance of 276.3 mF cm −2 at a current density of 0.5 mA cm −2 . • The highest energy density was 98.2 μWh cm −2 at a power density of 1600 μW cm −2 . Core-shell-type bimetallic oxide and carbon composites comprising zinc oxide (ZnO) nanospheres and zinc manganese oxide (ZnMn 2 O 4 ) nanowires were produced by a hydrothermal method, and supersonically sprayed together with reduced graphene oxide (rGO) nanosheets onto Ni foil to fabricate flexible supercapacitors. The supersonic impact facilitated the exfoliation of the rGO nanosheets, thereby increasing the surface area and adhesion of the composite particles to the substrate. The rGO nanosheets were vertically aligned during the supersonic impact and formed localized zones, enabling optimal accommodation of the ZnO/ZnMn 2 O 4 particles. This localization, with the addition of rGO, reduced the agglomeration of ZnO/ZnMn 2 O 4 particles. The molar concentration of MnSO 4 used in the synthesis of ZnO/ZnMn 2 O 4 was varied from 0.05 to 0.15 mol/L to determine the optimal MnSO 4 concentration that would result in the highest energy storage capacitance. The unique nanostructure of ZnO/ZnMn 2 O 4 and the self-alignment of rGO sheets facilitated a favorable environment for high energy storage capability with a specific capacitance of 276.3 mF cm −2 at a current density of 0.5 mA cm −2 and an energy density of 98.2 μWh cm −2 at a power density of 1600 μW cm −2 . The width of the potential window was increased to 1.2 V, implying a significant increase in the energy storage capability of the supercapacitor. Capacitance retention of 88% was achieved after 10,000 charge/discharge cycles for the supercapacitor fabricated using an optimal MnSO 4 concentration (0.10 mol/L) during the composite synthesis.

Green synthesis of Fe2O3 deposited g-C3N4: Addition of rGO promoted Z-scheme ternary heterojunction for efficient photocatalytic degradation and H2 evolution reaction

Construction of heterojunction photocatalysts with robust charge separation, efficiency light utilization and better charge transportation are hotspot in photocatalytic energy and environmental remediation applications. Herein, we have prepared the Z-scheme ternary heterojunction (rGO/g-C3N4/Fe2O3) photocatalysts using green tea extract assisted hydrothermal method for visible-light active photocatalytic degradation and H2 production. The heterojunction formation provides the more active sites for photocatalytic redox reaction in comparison with pure photocatalysts, which was confirmed by BET analysis. Moreover, elemental trapping experiment, photocurrent analysis, and band alignment derived from valance band XPS, clearly revealed that, the prepared photocatalyst shows Z-scheme charge separation. Photocatalytic activity demonstrated that, the prepared Z-scheme heterojunction exhibits 97 and 94% of degradation efficiency against methylene blue (MB) and ciprofloxacin (CIP) model organic pollutants. Moreover, the ternary heterojunction photocatalyst exhibits almost 100% of recycling efficiency towards H2 production even at 5th cycle with 20,786 μmol/g. Hence, we hope that this green synthesis approach would provide the new way to prepare the heterojunction photocatalysts for energy and environmental remediation applications.

Fabrication and Characterization of Piezoelectric Polymer Composites and Cytocompatibility with Mesenchymal Stem Cells.

Piezoelectric materials are promising for biomedical applications because they can provide mechanical or electrical stimulations via converse or direct piezoelectric effects. The stimulations have been proven to be beneficial for cell proliferation and tissue regeneration. Recent reports showed that doping different contents of reduced graphene oxide (rGO) or polyaniline (PANi) into biodegradable polyhydroxybutyrate (PHB) enhanced their piezoelectric response, showing potential for biomedical applications. In this study, we aim to determine the correlation between physiochemical properties and the in vitro cell response to the PHB-based composite scaffolds with rGO or PANi. Specifically, we characterized the surface morphology, wetting behavior, electrochemical impedance, and piezoelectric properties of the composites and controls. The addition of rGO and PANi resulted in decreased fiber diameters and hydrophobicity of PHB. The increased surface energy of PHB after doping nanofillers led to a reduced water contact angle (WCA) from 101.84 ± 2.18° (for PHB) to 88.43 ± 0.83° after the addition of 3 wt % PANi, whereas doping 1 wt % rGO decreased the WCA value to 92.56 ± 2.43°. Meanwhile, doping 0.2 wt % rGO into PHB improved the piezoelectric properties compared to the PHB control and other composites. Adding up to 1 wt % rGO or 3 wt % PANi nanofillers in PHB did not affect the adhesion densities of bone marrow-derived mesenchymal stem cells (BMSCs) on the scaffolds. The aspect ratios of attached BMSCs on the composite scaffolds increased compared to the PHB control. The study indicated that the PHB-based composites are promising for potential applications such as regenerative medicine, tissue stimulation, and bio-sensing, which should be further studied.

Biosynthesis, Characterization, and Augmented Anticancer Activity of ZrO2 Doped ZnO/rGO Nanocomposite.

Fabrication of ZnO nanoparticles (NPs) via green process has received enormous attention for its application in biomedicine. Here, a simple and cost-effective green route is reported for the synthesis of ZrO2-doped ZnO/reduced graphene oxide nanocomposites (ZnO/ZrO2/rGO NCs) exploiting ginger rhizome extract. Our aim was to improve the anticancer performance of ZnO/ZrO2/rGO NCs without toxicity to normal cells. The preparation of pure ZnO NPs, ZnO/ZrO2 NCs, and ZnO/ZrO2/rGO NCs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), photoluminescence (PL), and dynamic light scattering (DLS). XRD spectra of ZnO/ZrO2/rGO NCs exhibited two distinct sets of diffraction peaks, ZnO wurtzite structure, and ZrO2 phases (monoclinic + tetragonal). The SEM and TEM data show that ZrO2-doped ZnO particles were uniformly distributed on rGO sheets with the excellent quality of lattice fringes without alterations. PL spectra intensity and particle size of ZnO decreased after ZrO2-doping and rGO addition. DLS data demonstrated that green prepared samples show excellent colloidal stability in aqueous suspension. Biological results showed that ZnO/ZrO2/rGO NCs display around 3.5-fold higher anticancer efficacy in human lung cancer (A549) and breast cancer (MCF7) cells than ZnO NPs. A mechanistic approach suggested that the anticancer response of ZnO/ZrO2/rGO NCs was mediated via oxidative stress evident by the induction of the intracellular reactive oxygen species level and the reduction of the glutathione level. Moreover, green prepared nanostructures display good cytocompatibility in normal cell lines; human lung fibroblasts (IMR90) and breast epithelial (MCF10A) cells. However, the cytocompatibility of ZnO/ZrO2/rGO NCs in normal cells was better than those of pure ZnO NPs and ZnO/ZrO2 NCs. Augmented anticancer potential and improved cytocompatibility of ZnO/ZrO2/rGO NCs was due to ginger extract mediated beneficial synergism between ZnO, ZrO2, and rGO. This novel investigation emphasizes the significance of medicinal herb mediated ZnO-based NCs synthesis for biomedical research.

Cell Behavior Changes and Enzymatic Biodegradation of Hybrid Electrospun Poly(3-hydroxybutyrate)-Based Scaffolds with an Enhanced Piezoresponse after the Addition of Reduced Graphene Oxide.

This is the first comprehensive study of the impact of biodegradation on the structure, surface potential, mechanical and piezoelectric properties of poly(3-hydroxybutyrate) (PHB) scaffolds supplemented with reduced graphene oxide (rGO) as well as cell behavior under static and dynamic mechanical conditions. There is no effect of the rGO addition up to 1.0 wt% on the rate of enzymatic biodegradation of PHB scaffolds for 30 d. The biodegradation of scaffolds leads to the depolymerization of the amorphous phase, resulting in an increase in the degree of crystallinity. Because of more regular dipole order in the crystalline phase, surface potential of all fibers increases after the biodegradation, with a maximum (361 ± 5mV) after the addition of 1 wt% rGO into PHB as compared to pristine PHB fibers. By contrast, PHB-0.7rGO fibers manifest the strongest effective vertical (0.59 ± 0.03 pm V-1 ) and lateral (1.06 ± 0.02 pm V-1 ) piezoresponse owing to a greater presence of electroactive β-phase. In vitro assays involving primary human fibroblasts reveal equal biocompatibility and faster cell proliferation on PHB-0.7rGO scaffolds compared to pure PHB and nonpiezoelectric polycaprolactone scaffolds. Thus, the developed biodegradable PHB-rGO scaffolds with enhanced piezoresponse are promising for tissue-engineering applications.

CdO nanocubes decorated on rGO sheets as novel high conductivity positive electrode material for hybrid supercapacitor

Hybrid supercapacitor devices (HSs) are critical in developing electrochemical energy storage systems with large energy storage capacity and low operating costs. Here, we present the development of novel CdO-rGO nanocomposites, with changing rGO concentrations, as positive electrodes exhibiting outstanding energy storage performance. The nanocomposites were synthesized using a controlled and cost-effective hydrothermal technique. Interestingly, the composite with 25% optimal concentration (from now on referred to as CdO-25%rGO) demonstrated excellent specific capacitance (1195 F g−1 at 1 A g−1) with superior rate performance due to the addition of conductive rGO, allowing quick charge transfer kinetics. Inspired by the outstanding performance, we built CdO-25%rGO//AC HSC that expanded the voltage frame to 2 V when tested in a 3 M KOH alkaline electrolyte. Notably, the fabricated CdO-25%rGO//AC HSC delivered a high specific capacitance of 55 F g−1 at 1 A g−1 and displayed a large energy density of 30 Wh kg−1 at a maximum power density of 5000 W kg−1 coupled with excellent stability (12% capacity fade after 7000 cycles). These findings provide a helpful, logical direction for developing materials with unique compositional properties and electrochemical performance for energy storage applications.

Reverse saturation absorption of CaWO4 and Ce3+ substituted CaWO4 growth on rGO sheets an 2D/3D nanocomposite for smart filtering optical radiation

The CaWO4, CaWO4/rGO and Ce3+:CaWO4/rGO nanocomposites are synthesized and subjected to hydrothermal treatment. The optical filtering behavior of materials was explored using reliable Z-scan analysis. It utilizes the focused Gaussian beam of He:Ne laser (632.8 nm) in a continuous wave regime. Closed aperture Z-scan analysis of the synthesized samples exhibits negative refraction evident from the pre-focal peak to post-focal valley. The explicit third order nonlinear parameters such as kerr nonlinearityΔn = 5.6 x10-7 (W/cm2), two photon absorption β = 2.3 x10-4 (W/cm) and optical susceptibility χ3 = 10.5 x10-8 esu were obtained for the Ce3+:CaWO4/rGO (5 wt%) nanocomposites. Ce3+:CaWO4 micro dumbbells grown on the sheets of rGO is observed using HRSEM and HRTEM images. The C 1 s spectra recorded from XPS displays the area of sp2 hybridized (CC) graphitic like structure increases which enhances the optical nonlinearities. Id/Ig ratio increases by increasing the addition of rGO signifies the reduction of oxygenated functional groups in the nanocomposite evidenced by Raman spectra analysis. The bandgap calculated from the Tauc-plot relation is found to be around 3.0 eV and it decreases to 2.9 eV when the wt.% of rGO is increased.

Facile synthesis of CoCo2O4/rGO spinel nanoarray as a robust electrode for energy storage devices

• Graphene based CoCo 2 O 4 nanostructure array was developed through hydrothermal route. • The electrochemical activity of CoCo 2 O 4 /rGO was performed for supercapacitor application. • The fabricated electrode CoCo 2 O 4 /rGO exhibited the specific capacitance of 1352.2 F g -1 with high energy density (E d ) of 75.96 Wh Kg -1 at low current density of 2 A g -1 . • The enhanced CoCo 2 O 4 /rGO was ascribed to the synergistic effect, diverse morphology and larger surface area. Pseudocapacitor electrodes made of spinel oxide nanomaterial is considered as a better solution to overcome the current energy crisis. In this work, CoCo 2 O 4 is fabricated and then combined with reduced graphene oxide (rGO) through clean hydrothermal method. The microscopic and spectroscopic tools were employed to examine the properties of the fabricated electrode material. The electrochemical activity of the material was determined by using polarization curves (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge methods (GCD) and chronoamperometry (CA). The electrochemical results revealed that the addition of rGO into CoCo 2 O 4 electrode, increases the discharge duration, improves its specific capacitance, and its extensive stability. The electrochemical results of CoCo 2 O 4 /rGO display the specific capacitance (Csp) of 1352.2 Fg -1 , energy density (E d ) of 75.96 Wh Kg -1 and power density (P d ) of 636 W Kg -1 at low current density of 2 Ag -1 . The nanocomposite exhibited the capacitance retaining of 98.22% over 2000 cycles and stable for 40 h. Though, the capacitive activity of fabricated electrode was further improved with change in electronic and structural arrangement, alteration in the morphology, or incorporation of other metal or non-metals.

Single and double thermal reduction processes for synthesis reduced graphene oxide assisted by a muffle furnace: A facile robust synthesis and rapid approach to enhance electrical conductivity

Nowadays, with the rapid development of electronic devices, it is increasingly important to enhance the electrical conductivity of reduced graphene oxide (rGO). Thermal reduction (TR) temperature and time play the most crucial role as they control the electrical conductivity of rGO in terms of removal of oxygen-containing functional (OCF) groups. This work proposes a novel systematic approach for quick calibration of the OCF groups and lattice defects of GO to increase the conductivity by tuning the temperature and exposure time of the sample to the temperature. Single TR (STR) and double TR (DTR) processes were used in the current work, in which samples were exposed to temperatures of 500, 700, and 900 °C for 5 min. Further annealing took place for each sample at the same temperature with various reduction times. The results indicate that the DTR process improved the electrical conductivity of rGO samples. The highest enhancement of rGO500-5, rGO700-5, and rGO900-5 conductivities was 52.36%, 57.58%, and 231.81%, respectively. Consequently, this material can be used as a filler to get a well dispersed nanocomposite by accurate addition of rGO in a matrix, which enhances its electrical properties. Based on x-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and electrical analyses, the plausible STR and DTR mechanism of GO to rGO is effectively proposed.

Effect of graphene-based additives on mechanical strength and microstructure of gypsum plaster

In this study, graphene-based materials such as graphene oxide, reduced graphene oxide, and boron-doped reduced graphene oxide were synthesized, and their effects on the microstructure and mechanical properties of gypsum plaster were investigated. The graphene oxide (GO) sample was synthesized by modified Hummers’ method, and reduced graphene oxide (rGO) was obtained with the thermal reduction of GO. Boron doped reduced graphene oxide (B-rGO) was prepared via the impregnation method. The synthesized graphene-based materials were characterized using H 2 -TPR, TGA-DTA, XRD, FT-IR, SEM-EDS, TEM, Raman, and N 2 adsorption-desorption analysis. Analysis results confirmed that 450 o C was a sufficient temperature under an H 2 atmosphere to reduce GO and preserve rGO structure. XRD results revealed the presence of multilayer graphene structure in the rGO and B 2 O 3 crystals in the B-rGO sample. Multilayer graphene formation was also determined from the I 2D /I G ratio (0.1) of Raman analysis. Mechanical strength studies showed that while GO had a negative effect on both bending and compressive strength of gypsum plaster, rGO enhanced its bending and compressive strength. The addition of 0.1 wt% rGO added gypsum plaster increased the bending strength by 15.1% and compressive strength by 3.70%. SEM, He Pycnometry, and N 2 adsorption-desorption analyses revealed that rGO addition significantly changed the microstructure of gypsum plaster. The addition of B-rGO positively affected the compressive strength of the plaster and the highest increase was obtained as 8.6%; however, no significant change was observed in the microstructure of gypsum. • Electron microscopy images represented graphene nanosheets and graphene layers • X-ray diffraction results revealed the B 2 O 3 crystals in the boron-doped sample • Reduced graphene oxide increased the bending and compressive strength • Boron doped reduced graphene oxide enhanced the compressive strength • Reduced graphene oxide decreased the porosity of the gypsum

Tin Oxide (SnO2)-Decorated Reduced Graphene Oxide (rGO)-Based Hydroelectric Cells to Generate Large Current.

Nonphotocatalytic water splitting through oxygen-deficient, mesoporous metal oxide design-based hydroelectric cells (HECs) is a well-known phenomenon. To exploit more power from HECs, a metal oxide with more oxygen deficiency is desirable. In this study, oxygen-deficient mesoporous SnO2 via a sol-gel method and its composites with reduced graphene oxide (rGO) have been presented. Raman spectra of SnO2-rGO nanocomposites revealed an increase in the oxygen vacancies, while the X-ray diffraction (XRD) pattern confirmed the strain formation in the nanocomposite lattice owing to defect formation. The X-ray photoemission spectroscopy (XPS) results also indicated the presence of oxygen vacancies on the surface of SnO2, whereas Brunauer-Emmett-Teller (BET) measurements revealed that adding rGO into SnO2 increased the surface area from 44.54 to 84.00 m2 g-1. The water molecules are chemidissociated on the oxygen-deficient mesoporous surface of the pellet followed by physiodissociation at the mesopores. The redox reaction of the dissociated ions at the Zn anode and the Ag inert cathode produces current in the outer circuit. Interestingly, adding few drops of water into a SnO2-rGO-based HEC resulted in a short-circuit current of 148 mA with an open-cell voltage of 1.0 V. The maximum power delivered by the SnO2-rGO-based HEC is 148 mW. The addition of rGO into SnO2 boosts the peak current remarkably from 68 to 148 mA, which is the highest reported current generated by a hydroelectric cell.

Synergistic effects of boron nitride sheets and reduced graphene oxide on reinforcing the thermal conduction, SERS performance and thermal property of polyimide composite films

AbstractPolyimide (PI) composite films with hybrid fillers containing hBN (hexagonal boron nitride) sheets and rGO (reduced graphene oxide) were successfully fabricated by in‐situ polymerization. Herein, hBN sheets and rGO were obtained by ball milling and chemical reduction, respectively. In PI composite films, hBN can be tightly attached onto the surface of rGO via π‐π interaction, which can benefit the construction of heat‐conduction pathways and reduce boundary of heat resistance. The results show that the addition of rGO and hBN could enhance the thermal conductivity by synergistic effects. Specially, hBN and rGO are at the weight ratio of 1:1 and at the total loading of 33 wt%, thermal conductivity of PI composites can reach up to 1.19 Wm−1 K−1, which is 5.61 times higher than that of pure PI. Thermal property and dynamic mechanical property of composite films were also investigated. Besides, compared with pure PI, mixed fillers have obvious surface‐enhanced Raman scattering signals, indicating the synergistic effect of the mixed fillers. Overall, this study gives insights into heat dissipative and high sensitivity analysis components which may be used in the field of high‐temperature micro fabrication.

Construction of Sandwich‐Like r‐Fe3O4/rGO@CN Anode Materials as Conductive Agent‐Free Anode for Lithium‐Ion Batteries

AbstractFe3O4 is a prospective anode material but faces challenges to develop high‐performance electrodes for lithium‐ion battery. In this paper, Fe3O4 nanorods wrapped with reduced graphene oxide (rGO) as the conducting matrix and an amorphous nitrogen‐doped carbon (CN) as the protective coating were prepared using the hydrothermal method and freeze‐drying process. The obtained Fe3O4 nanorods are uniformly dispersed on the rGO nanosheet. The addition of rGO improves the electrical conductivity of the composite, while the amorphous carbon layer mitigates the volume expansion effect of Fe3O4 nanorods. Moreover, the in‐situ nitrogen doping accelerates the wetting effect of the electrolyte as well as reduces the diffusion and transfer resistance. Therefore, the obtained r‐Fe3O4/rGO@CN composite as conductive agent‐free anode exhibits outstanding performance and cycling stability at suitable nitrogen‐doped carbon coverage. The capacity could be maintained at 1020.7 mA h g−1 after 100 cycles at a current density of 0.5 A g−1. In addition, the capacity fading rate of per cycle is only 0.08% at a high current density of 2 A g−1. Our findings suggest that the prepared r‐Fe3O4/rGO@CN composite is a prospective candidate for utilization as an anode material in lithium‐ion batteries.

Enhanced Catalytic Performance and Sulfur Dioxide Resistance of Reduced Graphene Oxide-Promoted MnO2 Nanorods-Supported Pt Nanoparticles for Benzene Oxidation

The reduced graphene oxide (rGO)-promoted α-MnO2 nanorods-supported Pt (xPt-yrGO/α-MnO2, x = 0.93 wt%, y = 0.5, 1.0, and 2.0 wt%) nanocatalysts were prepared using a polyvinyl alcohol (PVA)-protected reduction method. After an appropriate loading of Pt on α-MnO2, the strong metal–support interaction between Pt and α-MnO2 was beneficial for an increase in catalytic activity. The simultaneous addition of rGO to α-MnO2 not only provided a more amount of benzene adsorption sites, but also acted as an electron transfer channel to accelerate charge migration, thus further improving catalytic activity of α-MnO2. Among all of the catalyst samples, 0.94Pt-1.0rGO/α-MnO2 showed the best catalytic performance with 90% benzene conversion at 160 °C and a gas hourly space velocity (GHSV) of 60,000 mL/(g h), which was better than that over the other Pt-based catalysts. The results of in situ DRIFTS characterization revealed that phenol, benzoquinone, and carboxylate species were the intermediates and eventually oxidized to CO2 and H2O. When sulfur dioxide was present, catalytic activity of α-MnO2 decreased due to the formation of manganese sulfate that blocked the active sites, while the loading of Pt and rGO hindered the chemisorption of SO2 and prevented the active sites of the catalyst from being poisoned by SO2, thus enhancing sulfur resistance of the catalyst. The 0.94Pt-1.0rGO/α-MnO2 catalyst presented in this work can be considered as a cost-effective and promising catalyst for the oxidative removal of volatile organic compounds.