Mass Ratio Of GO Research Articles

Degradation of aqueous methylparaben by non-thermal plasma combined with ZnFe2O4-rGO nanocomposites: Performance, multi-catalytic mechanism, influencing factors and degradation pathways

Non-thermal plasma (NTP) combined with zinc ferrite-reduced graphene oxide (ZnFe2O4-rGO) nanocomposites were used for the degradation of aqueous methylparaben (MeP). ZnFe2O4-rGO nanocomposites were prepared using the hydrothermal method, with the structure and photoelectric properties of nanocomposites then characterized. The effects of discharge power, initial MeP concentration, initial pH, and air flow rate on MeP degradation efficiency were investigated, and the multi-catalytic mechanism and MeP degradation pathways were established. Results showed that ZnFe2O4-rGO nanocomposites with a 10%:90% mass ratio of GO:ZnFe2O4 had an optimal catalytic effect. The MeP degradation efficiency of NTP combined with ZnFe2O4-rGO (10 wt%), was approximately 25% higher than that of NTP alone. Conditions favorable for MeP degradation included higher discharge power, lower MeP concentration, neutral pH value, and higher air flow rate. The degradation of MeP by NTP combined with ZnFe2O4-rGO nanocomposites followed pseudo-first-order kinetics. O2•-, •OH, H2O2, and O3 were found to play important roles in the MeP degradation, as part of the multi-catalytic mechanism of NTP combined with ZnFe2O4-rGO nanocomposites. MeP degradation pathways were proposed based on the degradation intermediates detected by gas chromatography mass spectrometry, including demethylation, hydroxylation, carboxylation, ring-opening, and mineralization reactions. The prepared ZnFe2O4-rGO nanocomposites provide an approach for improved contaminant degradation efficiency, with reduced energy consumption in the NTP process.

Preparation of high-quality graphene oxide-carbon quantum dots composites and their application for electrochemical sensing of uric acid and ascorbic acid

Graphene oxide-quantum dots systems are emerging as a new class of materials that hold promise for biochemical sensing applications. In this paper, the eco-friendly carbon quantum dots (CQDs) are prepared with cheap and recyclable coke powders as carbon source. The graphene oxide-carbon quantum dots (GO-CQDs) composites are synthesized using graphene oxide as the conductive skeleton to load the CQDs by a one-step calcination method. The obtained GO-CQDs composites demonstrate the successful decoration of CQDs on GO nanosheets. The CQDs acting as spacers create gaps between GO sheets, resulting in a high surface area, which electively increases the electrolyte accessibility and electronic transmission. The electrocatalytic activity and reversibility of GO-CQDs composites can be effectively enhanced by tuning the mass ratio of GO to CQDs and the heating process. Furthermore, a highly sensitive and selective electrochemical sensor for determining uric acid (UA) and ascorbic acid (AA) was developed by modifying GO-CQDs composites onto a glassy carbon electrode. The results show that the linear range, minimum detection limit, and sensitivity of the GO-CQDs electrode for UA detection are 1–150 μM, 0.01 μM, and 2319.4 μA mM−1 cm−2, respectively, and those for AA detection are 800–9000 μM, 31.57 μM, and 53.1 μA mM−1 cm−2, respectively. The GO-CQDs are employed as the electrode materials for the serum and urine samples electrochemical sensing, the results indicate that the sensor can be used for the analysis of real biological samples.

Enhanced Chromate (Ⅵ) Removal Characteristics and Mechanism Using Graphene Oxide Immobilized Nanoscale Zero-Valent Iron Coupled with a Weak Magnetic Field (GO-nFe0/WMF)

A green, high-efficiency mesoporous magnetic material with strong reusability and oxidation resistance, named graphene oxide immobilized nanoscale zero-valent iron (GO-nFe0), was prepared by a co-precipitation method. The structure, appearance, surface elements, and valence of GO-nFe0 were characterized via FESEM, TEM, FTIR, BET, XRD, and XPS. The characteristics and mechanism of Cr(Ⅵ) treatment in water using a weak magnetic field (WMF) coupled with GO-nFe0 (GO-nFe0/WMF) were studied. Batch experiments established that when the load mass ratio of GO to nFe0 was 1:10 under 20 mT weak magnetic field strength, the GO-nFe0/WMF system could completely remove the 10 mg·L-1 of Cr(Ⅵ) solution in 30 min, consistent with first-order dynamics. With a decrease in initial pH value and an increase in material dosage, the removal efficiency of Cr(Ⅵ) increased significantly by enhancing the release rate of Fe2+. ClO4- had no effect on the reaction, Cl- could encourage corrosion and promote the corrosion of nFe0 to release Fe2+, CO32- restrained the reaction through an increase in initial pH of the solution, and SO42- could promote the dissolution of the nFe0 surface passivation film to accelerate the reaction process. The GO-nFe0/WMF system can maintain high activity after five reuses and 30 days of exposure to air. XRD, XPS, and 1,10-phenanthroline shielding experiments proved that its great conductivity allowed GO to provide electron transfer sites to accelerate the transfer of electrons, and nFe0 could quickly release Fe2+. WMF generated a magnetic gradient force (FΔB) that pushed the paramagnetic Fe2+ ions in the diffusion boundary layer concentrated on the two poles of GO-nFe0, where the most magnetic intensity was present, to exposed active sites on both sides. The high removal rate ability of GO-nFe0 to release Fe2+ continuously was maintained.

Insight into charge carrier separation and solar-light utilization: rGO decorated 3D ZnO hollow microspheres for enhanced photocatalytic hydrogen evolution

Improving efficient solar light utilization, facilitating charge transportation and reducing electron-hole recombination, are the three major challenges in photocatalysis, and numerous interests have been devoted into overcoming these issues for obtaining high performance photocatalysts. Herein, ZnO hollow microspheres/reduced graphene oxide (ZnO/rGO) composites were constructed as a high performance photocatalyst for splitting water into H2 via a one-step microwave-assisted solvothermal process. The optimized ZnO/rGO nanocomposite (the mass ratio of GO to ZnO is 1%) reached a maximum H2 evolution rate of 648.1 μmol/h/g without using noble metal as cocatalyst, which exhibiting ~2.3-fold enhancement as compared to that of the bare ZnO. This significant improvement was primarily attributed to great light-harvesting capacity and the efficient charge carrier separation and transfer. The detailed characterization of PL and EIS revealed that, in the ZnO/rGO composite, the rGO nanosheets played important roles in promoting the charge carrier separation and transfer, which therefore resulting in an enhanced activity in H2 evolution. Our present observations provide a valuable methodology for exploring novel high performance photocatalyst, especially in graphene-based inorganic hybrid systems.

Fabrication of RHA-silica/graphene oxide nanocomposites for removal of lead ions from water

ABSTRACT In this study, rice husk ash-silica/graphene oxide (RHA-SiO2/GO) nanocomposites were synthesized by the in situ method using (3-aminopropyl) triethoxysilane as a coupling agent. The obtained products were used to remove lead ions (Pb2+) from aqueous solution. Effects of SiO2:GO mass ratio, contact time, pH and initial Pb2+ concentration on the adsorption capacity were studied. It was found that the suitable ratio of SiO2:GO for Pb2+ adsorption is 100:2. The suitable RHA-SiO2/GO was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area and thermal gravimetric analysis. Accordingly, RHA-SiO2/GO nanocomposite could be used as promising adsorbent for the removal of Pb2+ from water.

Construction of interconnected Al2O3 doped rGO network in natural rubber nanocomposites to achieve significant thermal conductivity and mechanical strength enhancement

Rubber promises to be an excellent matrix for heat dissipation composites due to its unique elasticity and flexibility. However, restricted by traditional processing approaches, it remains challenging to fabricate high-performance rubber nanocomposites with both good mechanical strength and high thermal conductivity (TC). Herein, we develop a novel GO-assisted gelation method to construct a 3D interconnected rGO@Al2O3 hybrid fillers network as efficient heat transfer path in natural rubber nanocomposite acquiring desirable performance. The as-prepared rubber nanocomposite, at a filler loading of 18.0 vol%, exhibits not only a largely increased tensile strength (25.6 MPa) but also a high TC (0.514 W/(m·K)). Owing to the construction of a highly interconnected filler network, the resulting 3D rGO@Al2O3-NR shows apparently higher TC than the nanocomposites prepared by conventional method at the same filler content. More promisingly, the filler network tends to orient perpendicular to the compressing direction at ultrahigh filler loading, causing surprisingly enhanced in-plane TC which is up to 3.233 W/(m·K) at 33.9 vol% filler content. Moreover, we can easily control electrical resistance by adjusting the mass ratio of GO to Al2O3, making the nanocomposites satisfy the use requirement of electrical insulation. This study provides a creative insight to the design of high-performance rubber nanocomposites with a bright application prospect in advanced heat dissipation materials.

Activation of persulfate by stability-enhanced magnetic graphene oxide for the removal of 2,4-dichlorophenol

A stability-enhanced magnetic catalyst, composed of α-Fe2O3@Fe3O4 shell–core magnetic nanoparticles and graphene oxide (MGO), was prepared and characterized by scanning electron micrope (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET). Catalyst synthesis was used to efficiently activate persulfate for the removal of 2,4-dichlorophenol (2,4-DCP). A magnetic nanoparticle:GO mass ratio of 5 (MGO-5) exhibited a better catalytic efficiency and could be effectively reused four times. The influences of the pollutant, catalyst, and oxidant concentrations were investigated, and the intrinsic relationships among these factors and the degradation kinetic constant were evaluated by a fitting method. It was found that the catalytic degradation process in the MGO-5-persulfate-2,4-DCP system was most likely dominated by an interfacial catalytic reaction, with an activation energy of 13.88 kJ/mol. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that both sulfate radicals (SO4−) and hydroxyl radicals (OH) were responsible for 2,4-DCP removal, but surface-bounded SO4− played a greater role. Chloride ions at a concentration of 0–60 mg/L had no effect on 2,4-DCP removal. The proposed advanced oxidation technology has potential applications for the practical removal of aqueous organic pollutants.

Preparation of magnetic iron oxide/graphene aerogel nanocomposites for removal of bisphenol A from water

• Fe 3 O 4 /GAs were synthesized in the presence of ethylenediamine as a reducing agent. • Effect of Fe 3 O 4 :GO mass ratio was studied. • The adsorption process of Fe 3 O 4 /GA for BPA was investigated. • The adsorption mechanism of Fe 3 O 4 /GA for BPA adsorption was determined. In this study, magnetic iron oxide nanoparticles decorated graphene aerogel (Fe 3 O 4 /GA) with different Fe 3 O 4 :GO mass ratios of 0.5:1, 1:1, and 2:1, which were synthesized in the presence of ethylenediamine as a reducing agent. The suitable mass ratio of Fe 3 O 4 :GO was determined to be 1:1 for the preparation of Fe 3 O 4 /GA (FGA2). The FGA2 was characterized by vibrating sample magnetometer, contact angle and Fourier transform infrared spectroscopy, X–ray diffraction, transmission electron microscopy, scanning electron microscope, Raman spectroscopy and Brunauer–Emmett–Teller specific surface area. The adsorption process of FGA2 for bisphenol A (BPA) was studied by single factor experiments including contact time, pH and initial BPA concentration. The adsorption data were followed the intraparticle diffusion and pseudo-second-order kinetic models. The maximum adsorption capability of FGA2 for BPA from Langmuir isotherm model was calculated to be 253.80 mg/g. The adsorption mechanism of FGA2 for BPA was mainly described by π−π interactions. Based on these results, the FGA2 could be concerned as an efficient adsorbent for the removal of BPA from water.

Facile preparation of binder–free electrode for electrochemical capacitors based on reduced graphene oxide composite film

Binder-free electrode based on reduced graphene oxide (rGO) is attracting attention for electrochemical capacitors. Here the binder-free electrodes have been fabricated by activating the composite films of GO and carbonized cornstalk-cores. In the composites, the rGO sheets are found to be tightly adhered to the activated bio‑carbon which is intercalated between the rGO sheets to prevent them from stacking. Moreover, the influences of the mass ratios of GO to bio‑carbon on the electrochemical performance have been systematically investigated. The optimal binder-free electrode (rGO/ACCS1/1) prepared from the composite films with 1:1 mass ratio of GO to bio‑carbon exhibits a specific capacitance as high as 278Fg−1 at scan rate of 1mVs−1 and shows excellent stability in 6M KOH electrolyte. Furthermore, the optimal electrode can retain 47.8% of the initial specific capacitance even at current density of 100Ag−1, indicating a fast charge-discharge capability. This work provides a simple method to prepare binder-free composite electrodes by introducing renewable and inexpensive biomass based carbon into activated rGO films.

Electrochemical performance of carbon paper supercapacitor using sodium molybdate gel polymer electrolyte and nickel molybdate electrode

Graphene oxide–modified poly (vinyl alcohol)/sodium sulfate-sodium molybdate (GO/PVA-Na2SO4-Na2MoO4, GPSS) gel polymer electrolyte and nickel molybdate (NiMoO4) electrode are integrated to fabricate carbon paper (CP) supercapacitor to improve capacitance performance. GO in PVA gel can introduce an effective ion transport pathway to improve ionic conductivity of gel polymer electrolyte. The ionic conductivity increases from 3.73 mS cm−1 for PVA-Na2SO4 to 6.46 mS cm−1 for GO/PVA-Na2SO4 at optimal GO mass ratio of 0.6% in GO/PVA gel. It also obviously increases from 4.33 mS cm−1 for PVA-Na2SO4-Na2MoO4 to 28.86 mS cm−1 for GO/PVA-Na2SO4-Na2MoO4. Both Na2MoO4 electrolyte and NiMoO4 electrode show reversible redox electroactivity to provide superior pseudocapacitance. Accordingly, the CP supercapacitor using GPSS gel shows specific capacitance of 41.67 mF cm−2 and energy density of 70.02 mWh m−2 at 0.5 mA cm−2, presenting higher performance than 15.91 mF cm−2 and 26.74 mWh m−2 using GO/PVA-Na2SO4 gel. Furthermore, the NiMoO4/CP supercapacitor using GPSS gel shows even higher specific capacitance of 78.18 mF cm−2 and energy density of 131.39 mWh m−2 at 0.5 mA cm−2. It also exhibits high cycling capacitance retention of 85% at 0.5 mA cm−2 for 1000 cycles. The improved capacitance performance of CP supercapacitor using Na2MoO4 gel polymer electrolyte and NiMoO4 electrode is ascribed to reversible redox reaction of Mo(VI)/Mo(V), Mo(VI)/Mo(IV), and Ni(II)/Ni(III). The NiMoO4/CP supercapacitor using GO/Na2MoO4 gel polymer electrolyte becomes desirable for the promising application in energy storage devices.

Graphene oxide as stable electrocatalytic substrate for solid-state bifacial dye-sensitized solar cells

Bifacial dye sensitized solar cells (BDSSCs) are regarded as advanced photovoltaics for markedly increased light-harvesting efficiency and the ability of both-side incident illumination absorption. We present here the fabrication of graphene oxide electrocatalyst supported polyaniline (GO/PANI) composite film via an in-situ electrochemical polymerization method and used it as transparent counter electrode (CE) for solid-state BDSSCs. The GO provides a large number of active nucleation sites, resulting in the formation of continuous PANI films through strong covalent bonds, which significantly increase the specific surface area and catalytic activity of the CE and further accelerate the charge transfer in the corresponding BDSSC. Due to the improved electrochemical catalytic activity of the GO/PANI CE with GO mass ratio of 0.6 wt%, both-illuminated power conversion efficiency of 5.74% with short-circuit current density of 20.23 mA cm−2 and open circuit voltage of 0.63 V is obtained for the solid-state BDSSC, which is 155.6% of the conventional bare PANI based BDSSC under front-irradiation. Electrochemical and electron transport/recombination performances have also been demonstrated for this type of device.

Graphene oxide modified nano-sized BaTiO3 as photocatalyst

In current work, for improving the photocatalytic efficiency of BaTiO3, a series of BaTiO3/Graphene oxide (GO) nanocomposites with different mass ratio of GO were prepared via a convenient freeze-drying approach. The enhanced photocatalytic activity was confirmed by the degradation of Methylene blue (MB) under the irradiation of Xe light. In comparison with other nanocomposites, the composite with 80% of GO exhibits relatively higher degradation rate of 67% in 150 min. The research here rendered useful information for understanding the mechanism of this improved photocatalytic behavior. It was indicated that the combination of ferroelectric materials and two-dimensional materials as a high-efficiency photo-catalyst is of great significance.

Tribological and machining characteristics of a minimum quantity lubrication (MQL) technology using GO/SiO2 hybrid nanoparticle water-based lubricants as cutting fluids

Minimum quantity lubrication (MQL) technologies using vegetable oil lubricants as cutting fluids have attracted much attention as they have excellent machining performance and are environmentally friendly. Nevertheless, oil-based MQL tends to produce high cutting temperatures owning to the low cooling capability of oil lubricants. In this work, an MQL technology that utilizes graphene oxide/silicon dioxide (GO/SiO) hybrid nanoparticle water-based lubricants as cutting fluids was developed, and its tribological and machining characteristics were comparatively investigated using four-ball and milling testing units. The mass ratio of GO to SiO was also varied to achieve optimal performance. The results showed that GO/SiO water-based MQL reduced coefficient of friction (COF) and worn scar diameter (WSD) significantly, and improved machining performance compared with individual GO and SiO water-based MQLs, as well as showed a comparative performance with traditional vegetable oil-based MQL. The superior performance of GO/SiO water-based MQL was attributed to the fact that GO/SiO hybrid nanoparticle additives entered the rubbing interface and formed a composite protecting film consisting of a self-lubrication layer of GO and a tribo-thin layer of SiO, which prevented the interface from direct contact and smoothened asperities.

Facile preparation and microwave absorption properties of RGO/MWCNTs/ZnFe2O4 hybrid nanocomposites

In this work, hybrid nanocomposites of reduced graphene oxide/multi-walled carbon nanotubes/zinc ferrite (RGO/MWCNTs/ZnFe2O4) were fabricated by a facile one-pot hydrothermal strategy. Effect of the mass ratio of GO to MWCNTs on the structure, morphology, magnetic properties and microwave absorption properties of the as-prepared hybrid nanocomposites was investigated in detail. Results demonstrated that the surface of MWCNTs were loaded with ZnFe2O4 nanoparticles and interlinked with RGO, which constructed the three-dimensional (3D) conductive networks in the ternary nanocomposites. Moreover, the ternary nanocomposites exhibited enhanced microwave absorption with the minimum reflection loss of −23.8 dB and effective absorption bandwidth (less than −10 dB) of 2.6 GHz. Significantly, the dual-waveband absorption characteristics covering the C and Ku bands were observed. Therefore, the obtained hybrid nanocomposites were potential candidates for application in the field of microwave absorption.

Self-assembly and enhanced visible-light-driven photocatalytic activity of reduced graphene oxide-Bi2WO6 photocatalysts

AbstractThe reduced graphene oxide-Bi2WO6(rGO-BWO) photocatalysts with different RMvalues (mass ratio of GO and Bi2WO6) had been successfully synthesized via hydrothermal method in the presence of GO. When increasing the RMvalues from 0 to 2%, the evident red shift of the absorption edges of rGO-BWO samples occurred, and the photocatalytic activities for the degradation of Rhodamine-B were enhanced gradually. However, there was a significant blue shift in the absorbance band, and the morphology of the incomplete rGO-BWO microspheres led to the lower photocatalytic activity when RMis increased from 4 to 10%. The enhanced photocatalytic activity can be attributed to the smaller band gap, which means needing less energy for the electron transition, the morphology of the unbroken microsphere that provides more possible reaction sites for the photocatalytic reaction, the appropriate GO content that may effectively mitigate electron-hole pair recombination by the migration of photoinduced electrons.

Facile fabrication of N-doped three-dimensional reduced graphene oxide as a superior electrocatalyst for oxygen reduction reaction

Nitrogen-doped graphene materials provide the attractive potentials to replace the high-priced Pt and Pt-based catalysts for oxygen reduction reaction (ORR) to accelerate the industrialization of fuel cells (FCs). Herein, the nitrogen-doped three-dimensional reduced graphene oxide (N-3DrGO) catalysts have been prepared by a facile hydrothermal method using the raw materials of GO, melamine and formaldehyde. The N contents in N-3DrGO products vary from 3.12 to 9.69 at.% which can be easily regulated by adjusting the feed mass ratios of GO and melamine. It is found that a higher content of N does not necessarily result in enhanced electrocatalytic activity. Rather, with the highest total percentage of graphitic N and pyridinic N (69.2%), superior solvent dispersibility, as well as a smaller interfacial and charge-transfer resistance, the N-3DrGO catalyst obtained by a mass ratio of 1:1.5 between GO and melamine presents the most excellent activity towards ORR. As a catalyst using in FCs for ORR, the obtained N-3DrGO catalysts exhibit favorable electrocatalytic performance, excellent methanol tolerance and much enhanced durability compared with that of commercial Pt/C (20wt%) catalyst in alkaline media. Furthermore, the above-mentioned approach is demonstrated to be a versatile method in fabricating N-3DrGO-based catalysts by introducing the foreign active atoms such as sulfur (S) to realize the N and S co-doping, which can further enhance the catalysts’ ORR activity.

One-step hydrothermal treatment to fabricate Bi2WO6-reduced graphene oxide nanocomposites for enhanced visible light photoelectrochemical performance.

Considering that ultraviolet light may cause the denaturation of biomaterials, searching for and engineering innovative and advanced nanomaterials with excellent photoelectrochemical properties under visible light illumination are of great significance in the fundamental understanding and application of photoelectrochemical (PEC) sensors. As a widely applied visible light response material, the applications of Bi2WO6 in PEC fields were restricted because of the rapid recombination of photoinduced electron-hole pairs. In this work, Bi2WO6 functionalized reduced oxide (Bi2WO6-rGO) nanocomposites (NCs) were prepared by a one-step solvothermal method. After optimizing the content of rGO, the Bi2WO6-rGO2.94% NCs displayed enhanced photocurrent intensity (the starting mass ratios of GO to Bi2WO6 = 0.0294), which was nearly 2.7-fold compared to that of pure Bi2WO6 nanoparticles because of the separation of the photoinduced carriers and the enhancement of visible light absorption. Based on the coupling of Pb2+-induced allosteric transition of G-quadruplex DNAzyme and the enzymatic biocatalytic precipitation (BCP), Bi2WO6-rGO2.94% NCs were applied in the construction of a novel PEC sensor for the determination of Pb2+. The as-fabricated PEC sensor exhibited good anti-interference ability and a good linear relationship was obtained between the photocurrent intensity and the logarithm of the Pb2+ concentration over a concentration range from 0.01 to 50 μM and with a detection limit of 3.3 nM (S/N = 3), indicating that Bi2WO6-rGO NCs would be promising materials for PEC sensing.

Preparation of SnO2/rGO Photoanode and Its Effect on the Property of Dye-Sensitized Solar Cells

SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanocrystals and reduced graphene oxide (rGO) nanoplatelets composite was prepared in a one-pot hydrothermal route utilizing the redox reaction between Sn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions and GO. The dye-sensitized solar cells (DSSCs) were assembled with N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -dipped SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO photoanode, Pt plate as the counter electrodes, and I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> as the electrolyte. Flower-like SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanocrystals dispersed on plate-like rGO to constitute a composite photoanode film were characterized by scanning electron microscope, transmission electron microscope, and XRD measurements. Photoelectric properties of DSSCs were analyzed with volt-ampere (J-V) characteristic curve and electrochemical impedance spectroscopy. The results show that DSSC with SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO nanocomposites as the photoanode exhibited better photoelectric properties than pure SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -DSSC due to a more stable nanocrystal oxide particle/rGO platelet structure. When the mass ratio of GO and SnCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 2H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O was 20%, the short-circuit current density (J sc) of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO-DSSC was up to 15.52 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the photoelectric conversion efficiency increased 34% compared to pure SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -DSSC. The synergistic effect of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rGO nanocomposites on electron transportation in the photoanode and photoelectricity conversion efficiency of DSSCs was discussed.

Electrochemically reduced graphene oxide/carbon nanotubes composites as binder-free supercapacitor electrodes

Binder-free composites of electrochemically reduced graphene oxide (ecrGO) and multiwalled carbon nanotubes (MWCNTs) were fabricated as supercapacitors electrodes operating in aqueous systems. GO was found to be electrochemically reduced according to the XRD and Raman data. Therefore, this facile and controllable method was applied to reduce GO in the GO/MWCNTs composites, generating ecrGO/MWCNTs composites. The ecrGO/MWCNTs composites exhibit higher specific capacitance (Csp) than ecrGO because the intercalation of MWCNTs into ecrGO sheets increases the surface areas, according to the TEM, XRD and N2 adsorption-desorption results. The composites with different mass ratios of GO to MWCNTs (10:1, 5:1, 1:1, 1:5, 1:10) were investigated. The ecrGO/MWCNTs composite (GO: MWCNTs = 5:1) showed the highest Csp from the cyclic voltammetry results at a scan rate of 10 mV s−1, and it expressed Csp of 165 F g−1 at a current density of 1 A g−1 and 93% retention after 4000 cycles of charge/discharge. When the mass ratio of GO to MWCNTs further decreases to 1:10, the Csp of the composites declines, and the ecrGO/MWCNTs composite (GO: MWCNTs = 1:10) performs a nearly pure double-layer capacitor. However, the composites containing more MWCNTs can maintain better capacitive behavior at higher rates of charge/discharge.

Catalytic Reduction of NOX Over TiO2–Graphene Oxide Supported with MnOX at Low Temperature

TiO2–graphene oxide (TiO2–GO) nanocomposites were prepared by the sol–gel method with different mass ratios of GO. The MnOX active components were loaded by means of ultrasonic impregnation. The catalysts exhibited excellent physical structures and electron transfer properties, which favored the catalytic activity. All of the catalysts were characterized by FESEM, XRD, TEM, BET, FT-IR, and XPS. The catalytic reduction activities of NOX were studied under low temperature conditions using ammonia as the reductant. Results indicated GO formation in the TiO2–GO supports, which reveals that TiO2–GO can be readily indexed as anatase TiO2 in all samples. Various valence states of manganese species coexisted in the MnOX/TiO2–GO catalysts. Non-stoichiometric (MnOX/Mn) on the surface of the composite catalysts was particularly beneficial to electron transfer, resulting in good redox performance. The optimum mass ratio of Mn in MnOX/TiO2–0.8 % GO was 9 wt%, and catalyst with this amount of Mn exhibited good resistance to H2O and SO2. All of the samples showed excellent N2 selectivity. The surface of the GO sheets is covered by a uniform layer of MnOX which increasing the activity of the catalyst by 9 % MnOX/TiO2–0.8 % GO.