Conductivity Of Graphene Oxide Research Articles

Recent Progress Using Graphene Oxide and Its Composites for Supercapacitor Applications: A Review

Supercapacitors are prospective energy storage devices for electronic devices due to their high power density, rapid charging and discharging, and extended cycle life. Materials with limited conductivity could have low charge-transfer ions, low rate capability, and low cycle stability, resulting in poor electrochemical performance. Enhancement of the device’s functionality can be achieved by controlling and designing the electrode materials. Graphene oxide (GO) has emerged as a promising material for the fabrication of supercapacitor devices on account of its remarkable physiochemical characteristics. The mechanical strength, surface area, and conductivity of GO are all quite excellent. These characteristics make it a promising material for use as electrodes, as they allow for the rapid storage and release of charges. To enhance the overall electrochemical performance, including conductivity, specific capacitance (Cs), cyclic stability, and capacitance retention, researchers concentrated their efforts on composite materials containing GO. Therefore, this review discusses the structural, morphological, and surface area characteristics of GO in composites with metal oxides, metal sulfides, metal chalcogenides, layered double hydroxides, metal–organic frameworks, and MXene for supercapacitor application. Furthermore, the organic and bacterial functionalization of GO is discussed. The electrochemical properties of GO and its composite structures are discussed according to the performance of three- and two-electrode systems. Finally, this review compares the performance of several composite types of GO to identify which is ideal. The development of these composite devices holds potential for use in energy storage applications. Because GO-modified materials embrace both electric double-layer capacitive and pseudocapacitive mechanisms, they often perform better than pristine by offering increased surface area, conductivity, and high rate capability. Additionally, the density functional theory (DFT) of GO-based electrode materials with geometrical structures and their characteristics for supercapacitors are addressed.

Topological insulator Bi2Te3 and graphene oxide synergistically enhance the photothermal effect and photocatalytic hydrogen evolution activity

Photothermal co-catalysis with the partial conversion of solar energy to thermal energy has the potential to overcome the current bottleneck of realizing efficient photocatalytic hydrogen production with zero artificial energy consumption. However, it is still challenging to design highly efficient photocatalysts that can make use of light and thermal energy synergistically. In this work, we successfully improved the photothermal effect and visible-light-catalyzed hydrogen evolution performance by constructing a novel heterojunction based on the topological insulator Bi2Te3 and graphene oxide (GO) synergistically modified with Zn0.67Cd0.33S. The photocatalytic hydrogen evolution rate of the 1.1 wt% Bi2Te3@0.05% GO@Zn0.67Cd0.33S heterojunctions reached 11.52 mmol/h/g (Apparent Quantum Yield of 21.7%), which was 12.9 times higher than that of pure Zn0.67Cd0.33S. Furthermore, the hydrogen production rate reached 71.79 mmol/h/g without cooling. The improved photocatalytic activity originated from the synergistic enhancement of visible-light absorption and the systematic enhancement of the photothermal effect by the Bi2Te3 and GO. In addition, the high electrical conductivity of Bi2Te3 and the high proton conductivity of GO not only increased the electron transfer rate but also synergistically mediated the acceleration of the hydrogen generation reaction. A strong built-in electric field is formed between Bi2Te3 and Zn0.67Cd0.33S, which greatly facilitates the efficient separation of photogenerated carriers. The obtained results illustrate a promising strategy for the development of efficient new photothermal catalysts.

Tailoring the multifunctional properties of hydrothermally synthesized reduced graphene oxide/tungsten oxide supported nanorods to enhance the electrochemical and water-splitting activities

Herein, we employ the synergistic effect and better conductivity of graphene oxide (GO) and reduced graphene oxide (rGO) to boost the energy storage capacity and electrical conductivity of tungsten oxide (WO3) nanomaterials. The structural analysis of the WO3 and its composites revealed the presence of a monoclinic phase with a periodic arrangement. However, the field emission scanning electron microscopy revealed the nanorod-shaped morphology for WO3 and the nonuniform interconnected nanorod nanosheet-like morphology for composites. The identification of functional groups and stretching–bending vibrations of W–O, CO WO, and C–C bonds are revealed by FT-IR and Raman spectroscopy. Additionally, the transmission electron microscopy and X-ray photoelectron spectroscopy confirmed the morphological, structural, and electronic states of hybrid rGO/WO3 nanostructures. The supercapacitive properties and electrocatalytic activity of WO3, GO/WO3, and rGO/WO3–nickel foam (NF) electrodes were investigated using a 2 M KOH via an three-electrode system in the desired potential window. As a result, the rGO/WO3 electrode exhibited promising electrochemical performance with a large specific capacity, 135 mAh/g (972 F/g) with high energy (ED), and power density (PD) of 33 Wh/kg and 1100 W/kg at 5 mA/cm2, and excellent retention of 92 % after 5000 CV cycles. However, the hybrid device is fabricated using rGO/WO3//rGO-NF as electrodes and exhibited a high specific capacity (78 mAh/g and 177 F/g at 5 mV/s), decent cycling stability (85 % after 5000 cycles), and high ED/PD (33 Wh/kg /1166 W/kg) respectively. Moreover, the electrocatalytic activity of WO3, GO/WO3, and rGO/WO3 electrodes was studied using 2 M KOH respectively. The superior electrochemical activities such as overpotential, Tafel slope, and the good electrochemical surface area (ESCA) of 328 mV, 95.5 mV/dec, and 38.2 cm2 with good stability were observed for rGO/WO3 electrode. The proposed asymmetric design provides promising material for developing next-generation energy storage devices for various portable electronic systems and water-splitting activity.

Synthesis of M-type hexaferrite reinforced graphene oxide composites for electromagnetic interference shielding

This study focused on addressing the increasing demand for materials that can effectively shield against electromagnetic interference. In particular, Ba0.7Mn0.3Nd0.1Fe11.9O19 M-type hexaferrite was synthesized using the sol–gel auto-combustion method and sintered at 1050 °C. The modified Hummer process was used to prepare graphene oxide (GO), and three composites were then synthesized with the ultrasonication method, which were denoted as C-1 (90 % M-ferrite + 10 % GO), C-2 (80 % M-ferrite + 20 % GO), and C-3 (70 % M-ferrite + 30 % GO). X-ray diffraction (XRD) analysis confirmed the formation of the hexagonal phase of the M-type barium hexaferrite and GO. A prominent peak at an angle of 8.82° corresponding to the (001) reflection was observed by XRD analysis for the GO sample and it confirmed the effective oxidation of graphite and formation of GO. Scanning electron micrographs of M-type hexaferrite demonstrated the formation of platelet-like grains with hexagonal shapes, which were suitable for microwave absorption. The direct current electrical resistivity at room temperature was determined as 2.08 × 10−8 Ω-cm for the M-type ferrite, and the resistivity of the composites decreased as the concentration of GO increased due to the superior conductivity of GO compared with the ferrite. The dielectric properties of all samples followed the Maxwell–Wagner model. The dielectric characteristics increased in magnitude as the GO content increased. The AC magnetic susceptibility decreased for the M-type ferrite and three composites as the temperature increased to eventually reach a steady state at a specific temperature known as the Curie temperature. Except for GO, the Curie temperatures of all samples were within the range of 348 K–450 K. Coupling magnetic ferrite with GO allows the magneto-electrical characteristics to be tuned, with possible uses in electronic devices, electromagnetic shielding, supercapacitors, and water purification.

Notable electrical and mechanical properties of polyacrylamide (PAM) with graphene oxide (GO) and single-walled carbon nanotubes (SWCNTs)

Abstract In the present investigation, a polyacrylamide (PAM) – graphene oxide (GO)-single-walled carbon nanotubes (SWNTs) composite has been prepared through a cost effective solution cast method and physical properties (electrical and mechanical) measurements have been carried out. The GO sheets contain oxygen functional groups which enhance the interfacial adhesion with the polymer matrix, while the SWNTs act as wires joining the GO together in the composite matrix. This interconnected network creates a conducting path, lowering film resistance and improving PAM films’ electrical, mechanical, and thermal properties. Raman study demonstrated that carbon nanofiller (SWNTs, GO) and polymer PAM have good interfacial bonding. The electrical conductivity and mechanical characteristics (hardness and elastic modulus) of these composite films were enhanced at a loading of 15 wt% GO and 15 wt% SWNTs in PAM matrix. Electrical conductivity of GO (15 wt%) – SWNTs (15 wt%)-PAM composite film was found to be 2.8 × 10−2 S/cm, which is five orders of magnitude higher than that of the PAM polymer. In comparison to pure PAM polymer, the elastic modulus and hardness are found to be 1.14 and 65 times higher, respectively.

Three-Dimensional Sulfonated Graphene Oxide Proton Exchange Membranes for Fuel Cells

During the last decades, graphene oxide (GO)-based materials have been extensively studied as low-cost efficient solid electrolytes for fuel-cell application. However, the observed limited proton conductivity of GO in the out-of-plane directions and associated lower fuel-cell performance largely limit their practical application. Herein, we have demonstrated a sulfate ion-intercalated three-dimensional graphene oxide (3DSGO) showing an exceptionally high out-of-plane proton conductivity of 0.74 S cm–1 at room temperature and 90% RH, and an in-plane proton conductivity of 3.19 S cm–1. Additionally, measurement of cell performance using the prepared membrane as the electrolyte of the proton exchange membrane fuel cell (PEMFC) showed an optimum power density of 112.65 mW cm–2 at 100% RH and 30 °C, which is more than double that achieved for 3DGO (50 mW cm–2). This efficient proton conduction ability and PEMFC performance of the 3DSGO is linked with the 3D interconnected ionic highways and substantial interlayer void space, which provide the higher water retention capacity in the 3D spongy architecture and a facile proton conduction pathway.

Bioinspired GO/Au nanocomposite synthesis: Characteristics and use as a high-performance dielectric material in nanoelectronics

• O/Au nanocomposites were successfully synthesised using Ocimum basilicum . (basil) seed extract. • The GO/Au nanocomposite can also be used to demonstrate high-performance electronic devices. • The bioinspired approach enhances the dielectric behaviour of GO/Au nanocomposite matrixes by adding organic macromolecules capable of modest GO reduction. A bioinspired method was used to synthesise graphene oxide (GO) based noble metal (Au) nanocomposite (GO/Au nanocomposite) using chemical exfoliated graphene oxide as the base matrix and biosynthesised gold (Au) nanoparticles. The morphological characterization of GO and the GO/Au nanocomposite was determined using TEM and SEM analysis. The amount of Au nanoparticles conjugated with GO was determined using an EDAX analysis. The absorption and emission properties of GO and GO/Au nanocomposite are revealed through optical studies. FTIR analysis revealed the presence of different functional groups in GO and GO/Au nanocomposite, while XRD analysis confirmed the formation of crystalline GO and GO/Au nanocomposite of different sizes. TGA analysis was used to determine the degradation behaviour of the two products with respect to temperature. An LCR analysis was used to characterise the electrical characteristics of GO dielectric features as a function of frequency between 1 Hz and 1 MHz. The dielectric permittivity and electrical conductivity of GO were very frequency-driven. The results demonstrated that GO has direct current and correlated barrier hopping conductivity processes in the low and high frequency bands. The dielectric constant and loss factors of the GO/Au nanocomposite show that the bioinspired approach includes organic macromolecules capable of modest GO reduction and so modifying the C/O ratio, resulting in an enhancement in the matrix's dielectric characteristics. This study further demonstrates that high-performance electronic devices, as well as electrical and energy storage systems based on high dielectrics, might be scaled using GO-based materials.

Preparation of AQS/GO/PVDF redox mediator membrane and the decolorization of azo dyes

AQS/PVDF and AQS/GO/PVDF redox mediator membranes were prepared with poly (vinylidene fluoride) (PVDF) as the raw supporting material of membrane, anthraquinone-2-sulfonic acid (AQS) as the redox mediator, and graphene oxide (GO) as an additive by an immersion precipitation method. The AQS content in the redox mediator membrane was optimized with the formation performance of AQS/PVDF membrane. With the optimal casting solution for AQS/PVDF membrane, GO was introduced as an additive to form AQS/GO/PVDF membrane. The effects of the redox mediator membranes on the bacterial decolorization of dye wastewaters were investigated. The results suggest that both AQS/PVDF and AQS/GO/PVDF membranes can promote the bacterial decolorization of dyes and the introduction of GO improves the decolorization rate more significantly because it can accelerate the electron transfer. Therefore, the conductivity of GO and the electron shuttle of AQS show a synergetic effect on accelerating the bacterial decolorization of dyes.

Laser‐Assisted Rapid Fabrication of Large‐Scale Graphene Oxide Transparent Conductors

AbstractAlthough graphene films are the main candidate for replacing scarce and brittle metal‐oxide transparent conductors, the current challenges on graphene deposition and patterning are severely limiting their commercial application. Here, materials and methods that allow large‐scale, efficient, and low‐cost fabrication of highly transparent conductors in a few minutes are demonstrated. First, a low‐cost graphene oxide (GO) solution through spray coating is deposited, followed by simultaneous reduced graphene oxide reduction and thinning through a low‐cost nanosecond fiber laser. It is shown that a 1064 nm master oscillator power amplifier laser enhances the conductivity of GO coated sample by ≈60 times, with excellent optical transparency of 90%. The laser parameters are adjusted, and creation of various shades of transparency, conductivity, and a full ablation are demonstrated. This way, complex GO‐based circuits can be produced rapidly. Compared to the existing techniques that require chemical vapor deposition, and chemical/thermal reduction, this technique is considerably more accessible, replicable, and can open doors for various applications in optoelectronics, energy storage/harvesting, and sensing. The electrical, chemical, and optical properties of the samples are characterized before and after laser treatment, through optical profilometry, scanning electron microscopy, and (UV, Raman, and energy dispersive X‐ray) spectroscopy and applications in transparent conductors, and laser‐patterned high‐resolution and miniaturized interdigitated sensors are shown.

Electrospun 1D and 2D Carbon and Polyvinylidene Fluoride (PVDF) Piezoelectric Nanocomposites

Piezoelectric nanocomposite fibrous membranes consisting of polymer polyvinylidene fluoride (PVDF) as matrix and incorporating 1D carbon nanotubes (CNTs) and 2D graphene oxide (GO) were prepared using an electrospinning process. The influence of the filler type, loading, and dispersion status on the total PVDF crystallinity ( X c ); the relative fraction of the β phase (piezoelectric phase) in crystalline PVDF ( F β ); the volume fraction of β phase in the samples ( v β ); and the piezoelectric coefficient d 33 were investigated. The v β is used to assess the formation of β phase for the first time, which considered the combined influence of fillers on X c and F β , and is more practical than other investigations using only F β for the assessment. The inclusion of all types of carbon fillers had resulted in a considerable reduction in the X c compared with the neat PVDF, and the X c decreased with the CNT loading while increased with the GO loading. The addition of CNT and GO had also reduced the F β compared with the neat PVDF, and F β increased with CNT loading while decreased as GO loading increased. The v β is significantly reduced by the addition of CNT and GO, while v β decreases with CNT and GO loading increases. Since the calculation of v β has considered the combined influence of fillers on X c and F β , both of which were reduced by incorporating CNT and GO, the reduction of v β was expected. The v β of the PVDF/CNT composites were higher than that of the PVDF/GO composites. Although it is generally anticipated that d 33 increases with v β , it is observed that in the presence of CNT, d 33 is dominated by the increase in electric conductivity of the composites during and after the electrospinning process, giving rise to transport of charges, produced by β crystals within the fiber to the surface of the sample. In addition, the 1D CNTs may have promoted the orientation of β crystals in the d 33 direction, therefore, enhancing the d 33 of the composites despite the hindrance of the β-phase formation (i.e., the reduction of v β ). Adding CNTs can also improve piezoelectricity through interfacial polarization, which increases the dielectric constant of composite (mobile charges within CNTs facilitate composite polarization). CNT loadings higher than 0.01 wt.% are sufficient to outperform the neat PVDF, and d 33 becomes 59.7% higher than the neat PVDF at 0.03 wt.% loading, but only GO loadings of 0.5 wt.% achieved comparable d 33 to the neat PVDF; further increase in GO loading had resulted in a decline in d 33 . The low conductivity of GO, the influence of flocculation, and the lower aspect ratio compared with CNT may result in lower electron transfer and less orientation of the β-phase polycrystalline. The d 33 of the PVDF/CNT composites is higher than that of the PVDF/GO composites despite much higher loading of GO. This study aims to contribute to the development of PVDF nanocomposites in piezoelectric energy harvesting applications (e.g., self-powered biosensors and wireless sensor networks).

Two-dimensional cluster catalysts with superior thermal stability and catalytic activity for AP

The preparation of catalysts with small particle size, large specific surface area and high atomic utilization has always been the focus of research in the field of catalysis. As for energetic materials, catalysts are always used to improve the thermal decomposition performance of ammonium perchlorate (AP) as it has significant effect on the power of engine. In this work, a two-dimensional metal clusters catalyst has been successfully prepared by solvothermal and heat treatment to improve thermal decomposition performance of AP. In detail, the transition metal ions were supported on the graphene oxide (GO) surface by organic ligands linking, followed by heat treatment to obtain two-dimensional rGO based metal clusters catalyst. The morphology and structure of the catalysts at different temperatures and their effect on AP decomposition were studied, the results show that catalyst at 300 °C has a particle size of 20 nm and uniformly distributed on rGO. The catalyst promotes the high temperature decomposition of AP by 73.7 °C with improved stability, and increases the heat release from 652.73 J/g to 1392.11 J/g. This may be attributed to good conductivity of GO and the strong gain-loss electron ability of the metal clusters. The presence of GO increased the active sites for cluster catalysis, additional, the metal clusters have a positive synergistic effect with GO. Thus, the thermal decomposition performance of AP was enhanced meanwhile thermal stability can also be improved.

Simultaneously enhancing the photocatalytic and photothermal effect of NH2-MIL-125-GO-Pt ternary heterojunction for rapid therapy of bacteria-infected wounds

Infections caused by bacteria threaten human health, so how to effectively kill bacteria is an urgent problem. We therefore synthesized a NH2-MIL-125-GO-Pt ternary composite heterojunction with graphene oxide (GO) and platinum (Pt) nanoparticles co-doped with metal-organic framework (NH2-MIL-125) for use in photocatalytic and photothermal synergistic disinfection under white light irradiation. Due to the good conductivity of GO and the Schottky junction between Pt and MOF, the doping of GO and Pt will effectively separate and transfer the photogenerated electron-hole pairs generated by NH2-MIL-125, thereby effectively improving the photocatalytic efficiency of NH2-MIL-125. Meanwhile, NH2-MIL-125-GO-Pt has good photothermal effect under white light irradiation. Therefore, the NH2-MIL-125-GO-Pt composite can be used for effective sterilization. The antibacterial efficiency of NH2-MIL-125-GO-Pt against Staphylococcus aureus and Escherichia coli were as high as 99.94% and 99.12%, respectively, within 20 min of white light irradiation. In vivo experiments showed that NH2-MIL-125-GO-Pt could effectively kill bacteria and promote wound healing. This work brings new insights into the use of NH2-MIL-125-based photocatalyst materials for rapid disinfection of environments with pathogenic microorganisms.

Investigation of the thermal and light sensing properties of graphene oxide and reduced graphene oxide films obtained by spin coating method

This paper reported the thermal and light sensing properties of graphene oxide (GO) and reduced graphene oxide (RGO) films obtained by spin coating on soda lime glass. GO showed a higher thermal sensing response of 9.0 compared to RGO which had a maximum thermal sensing response of 2.2 at 623 K. The thermal conductivity of GO and RGO increased with temperature although RGO typified better thermal conductivity. For GO, a negative temperature coefficient of resistance (NTC) of 0.0032153 /K was obtained which is higher than values obtained in literatures while RGO had a NTC value of 0.00201/K. For the photo sensing, the peak photo resistance of GO corresponds to an energy band gap of 3.5 eV while the peak photo resistance of RGO corresponds to a decreased energy band gap of 2.76 eV. It was also confirmed that lower bandgap favored improved photosensing function. RGO film showed intrinsic photoconductivity as the photoconductivity increased at longer wavelengths. The photo sensing of GO and RGO were dominated by inter-band optical transitions in the UV to mid infrared region. The obtained NTC values for GO and RGO and the photoconductivity of the materials can promote further utilization in robotics and optical applications.

Novel synthesis of graphene oxide/In2S3/TiO2 NRs heterojunction photoanode for enhanced photoelectrochemical (PEC) performance

Novel heterostructure photocatalyst built from titanium dioxide (TiO2), graphene oxide (GO) and indium sulfide (In2S3) has been successfully prepared for photoelectrochemical hydrogen production. The stepwise introduction of three materials on conductive glass substrate has been realized through hydrothermal, electrochimical and spin coating deposition methods, respectively. The structure, morphology, composition, optical and photoelectrochemical properties of the resultant photoanodes were investigated in detail. The presence of GO in the heterostructure film was confirmed by Raman analysis with D and G band intensity. Surface morphology analysis of the GO/In2S3/TiO2 NRs structure reveal the homogenous distribution of graphene oxide on In2S3/TiO2 NRs surface. From UV–Vis analysis, band gap energy of the samples decreases gradually from 3.34 eV (TiO2 NRs) to 3.12 eV, with In2S3 and GO addition. The electrochemical impedance spectroscopy (EIS) further confirmed that GO/In2S3/TiO2NRs heterostructure possessed the lowest charge-transfer resistance, revealing that In2S3 and GO could significantly accelerate the electron mobility compared with bare TiO2. From Mott-Schottky plots, several parameters such as flat-band potential and free carrier concentration were determined. Next, The GO/In2S3/TiO2 NRs electrode achieved remarkably improved current density (0.45 mAcm2 at 0.8 V vs Ag/AgCl) compared to pure TiO2 NRs or In2S3/TiO2 NRs electrodes, which attributes to the uniform structure and excellent electrical conductivity of GO, which could reduce the combination rate of the photo electron-hole pairs. These results reveal that GO/In2S3/TiO2 NRs possesses great potential toward the development of newly synthesizable catalysts in the field of photoelectrochemical water splitting.

Oscillation in the electrical conductivity of a thick graphene oxide membrane

Because of their unusual fundamental behavior that arises at the molecular scale, the electrical conductivity of stacked graphene oxide (GO) sheets in the presence of external parameters is not adequately understood. Previous studies concentrated on the DC response of thin GO membranes giving their resistive switching properties. Here, we observe anomalous low-frequency (<1 Hz) oscillations in the electrical conductivity of micrometer size GO, which is repeated in a process over and over in an ongoing feedback loop. Such vibrations and their unique trajectories are not only fundamentally important but also have characteristic frequencies that can be directly linked to the formation and destruction of regions with sp2 hybridization. Also, the reported switching time (of the order of seconds) makes our resistive switching system different than all the previously reported systems and introduces a new class of switching phenomena. The observed phenomena improve our understanding of the electrical conductivity of GO membranes and the corresponding microscopic details that pave the way for the promising application of these new observed low-frequency oscillations.

Surface modification on ammonium polyphosphate and its enhanced flame retardancy in thermoplastic polyurethane

Ammonium polyphosphate (APP) is an effective flame retardant in thermoplastic polyurethane (TPU). In order to further enhance the flame retardant efficiency of APP, it was coated with graphene oxide (GO) and melamine formaldehyde (MF) successively, by using 5 wt% end product of MF‐GO@APP in TPU, the sample produced little dripping during burning and reached UL‐94V‐0 grade, peak smoke production rate was reduced from 0.132 m2/s in TPU to 0.051 m2/s, that was 61.4% decrease. Neat TPU burned out with little residue left, but by the help of 5 wt% MF‐GO@APP, 24.4 wt% of char was left. These results were tried to be analyzed as relative higher heat conductivity of GO, in heating GO transferred more heat to APP and MF, resulting in earlier degradation of APP and MF, the decomposed product of MF and APP cross‐linked together to form more compact char above substrate. MF‐GO@APP acted as an integrated intumescent flame retardant.

Interface of GO with SnO2 quantum dots as an efficient visible-light photocatalyst

Graphene oxide (GO) with beneficial functional groups regulates the surface chemistry for catalytic applications. However, the low electrical conductivity of GO invokes further treatments that compromise the above-valued properties. We report an interfacial engineering of GO decorated with SnO2 quantum dots (QDs) for the visible-light-driven catalysis of dye degradation. Retention of beneficial functional features of GO and QDs in the GO-SnO2 composite is established by using TEM, FTIR, and Raman spectroscopy techniques. Further, investigations with EXAFS and lifetime-measurements provide the local structure and defects distributions in QDs which are correlated with the improved conductivity. PL and electrochemical impedance spectroscopic measurements help unraveling the charge-transfer across the interface of the GO-SnO2 composite. The unique ability of ∼94% degradation of MB using only 0.5 mg of GO-SnO2 catalyst within half an hour under the visible light is demonstrated for the first time with insights on the photocatalytic mechanism.

Self-assembled ZIF-67@graphene oxide as a cobalt-based catalyst precursor with enhanced catalytic activity toward methanolysis of sodium borohydride

In this work, a composite consisting of ZIF-67 and graphene oxide (GO) was successfully synthesized by a facile in-situ synthesis method and applied in hydrogen release from the methanolysis of sodium borohydride (NaBH4). Physicochemical properties of pure ZIF-67 and the ZIF-67@GO composites are well characterized by XRD, BET, SEM and HRTEM. It was observed that the ZIF-67 crystals are intimately anchored on GO sheets. An increase of GO in the composite led to a marked decrease of the BET surface area and an increased average pore size. However, the ZIF-67@GO precursor with high GO doping exhibited much higher activity toward the methanolysis of NaBH4, which suggests that the good conductivity of GO is beneficial to improve the catalytic performance. The ZIF-67@GO precursor experienced a structure reconstruction during the methanolysis reaction due to the presence of reducible Co2+. Moreover, the reduced ZIF-67@GO displayed a slightly higher activity as compared to the pristine composite and retained excellent durability after five cycles. A possible mechanism for the hydrogen generation from the methanolysis of NaBH4 using a ZIF-67@GO catalyst was proposed.

“Labyrinthine structure” anticorrosive water-based composite coatings

A new environmentally friendly modified graphene oxide/waterborne epoxy composite coating (W-EMGO) is reported. The composite coating, developed by introducing graphene oxide modified with [3-(2-aminoethyl) aminopropyl] trimethoxysilane (MGO) into waterborne epoxy, exhibited excellent corrosion resistance and slight harm of solvent-based coating to the environment. The MGO displayed perfect dispersion and corrosion resistance, which reduced the aggregation of graphene oxide (GO) due to the coupling of functional groups. After modification, the lamellar structure of GO remains unchanged, and the interlayer spacing was increased. Crosslinking with resin to form a “labyrinth structure” corrosion path in the coating. Furthermore, the conductivity of GO decreased after the insertion of functional groups. The results demonstrated that the composite with a 0.5 wt.% content of MGO presented remarkably improved corrosion resistance with a protection efficiency (PE) of 99.7%.

Photocatalytic performance improvement by utilizing GO_MWCNTs hybrid solution on sand/ZnO/TiO2-based photocatalysts to degrade methylene blue dye.

In this work, sand/zinc oxide (ZnO)/titanium dioxide (TiO2)-based photocatalysts were hybridized with graphene oxide (GO) and GO_multi-walled carbon nanotubes (MWCNTs) hybrid solution. The novel hybrid was then used in photocatalysis to degrade dye contamination. The nanocomposite photocatalyst was initially fabricated by growing ZnO nanorods (NRs) via sol-gel immersion followed by synthesizing TiO2 NRs for different times (5 and 20 h) using a hydrothermal method on sand as a substrate. Prior to the hybridization, the initial GO was synthesized using electrochemical exfoliation and further mixed with 1 wt% MWCNTs to form GO_MWCNTs hybrid solution. The synthesized GO and GO_MWCNTs hybrid solution were then incorporated onto sand/ZnO/TiO2 nanocomposite-based photocatalysts through immersion. Various sand/ZnO/TiO2-based photocatalysts were then tested for methylene blue (MB) dye degradation within 3 days. On the basis of UV-Vis measurement, the highest MB degradation was achieved by using sand/ZnO NRs/TiO2 NRs (5 h)/GO_MWCNTs (92.60%). The high surface area and high electrical conductivity of GO_MWCNTs prolonged the lifetime of electron/hole separation and thus enhanced the photocatalytic performance.