Enhanced capacitive performance by improving the graphitized structure in carbon aerogel microspheres

Herein, good electrical conductivity and high specific surface area carbon aerogel (CA) microspheres were synthesized by a facile and economical route using a high temperature carbonization and CO₂ activation method. The electroconductive graphitized structure of the CA microspheres could be easily improved by increasing the carbonization temperature. Then the CA microspheres were activated with CO₂ to increase the specific surface area of the electrode material for electric double layer capacitors (EDLC). The sample carbonized at 1500 °C for 0.5 h and CO₂ activated at 950 °C for 8 h showed an acceptable specific surface area and excellent cycle performance and rate capability for EDLC: 98% of the initial value of the capacitance was retained after 10 000 cycles, a specific capacitance of 121 F g⁻¹ at 0.2 A g⁻¹ and 101 F g⁻¹ at 2 A g⁻¹.

Carbon aerogels (CAs) microspheres with good electrical conductivity and high specific surface area were synthesized by high temperature carbonization and CO₂ activation method, which exhibit an enhanced capacitive performance in supercapacitors.     

Preparation of high-performance toluene adsorbents by sugarcane bagasse carbonization combined with surface modification

A series of activated carbons were prepared by carbonizing sugarcane bagasse combined with surface modification, which showed an excellent performance of adsorbing toluene (522 mg g⁻¹ at 30 °C). The results demonstrated that the enhancement of the activated temperature was benefit to promote the porosity and specific surface area (BET) of ACs. Thus, AC-800 showed optimal adsorption and its toluene adsorption performance was better than that of most ACs in the literature. Five consecutive adsorption–desorption cycles presented that AC-800''s toluene adsorptive capacity was as high as 522 mg g⁻¹ (30 °C), and toluene adsorptive capacity was only decreased by 4.5%. According to the fraction of N-containing functional groups and the binding energy of toluene on N-containing functional groups, pyridinic-N (N-6) was believed to contribute more to toluene adsorption. Moreover, the Bangham model was considered as the best model of describing toluene adsorption on AC-800. Therefore, both surface adsorption and pore diffusion were the two mechanisms of toluene adsorption, and the diffusion of toluene molecules in the pores was considered as the key factor that affected the adsorption rate.

A series of activated carbons were prepared by carbonizing sugarcane bagasse combined with surface modification, which showed an excellent performance of adsorbing toluene (522 mg g⁻¹ at 30 °C).     

Roll-to-roll continuous carbon nanotube sheets with high electrical conductivity

Large scale manufacturing of electrically conductive carbon nanotube (CNT) sheets with production capability, low cost, and long-term electrical performance stability is still a challenge. A new method to fabricate highly conductive continuous buckypaper (CBP) with roll-to-roll production capability and relatively low cost is reported. The electrical conductivity of CBP can be improved to 7.6 × 10⁴ S m⁻¹ by using an oxidant chemical (i.e. HNO₃ and I₂) doping method. To compensate for the conductivity degradation caused by the instability of the oxidant chemical doping, a polymer layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was coated on the chemically doped CBP. The fabricated highly conductive CBP showed stable electrical performance in air for more than a month. This CBP material with high electrical conductivity, relatively low cost, and roll-to-roll manufacturing capability could enable a wide range of engineering applications including flexible conductors, electromagnetic interference (EMI) shielding materials, and electrodes in energy devices.

Highly electrically conductive, roll-to-roll continuous buckypaper (CBP) with stable performance was achieved by chemical doping and polymer coating (PEDOT:PSS).     

TiO2@Sn3O4 nanorods vertically aligned on carbon fiber papers for enhanced photoelectrochemical performance

Semiconductor heterostructures are regarded as an efficient way to improve the photocurrent in photoelectrochemical cell-type (PEC) photodetectors. To better utilize solar energy, TiO₂@Sn₃O₄ arrays vertically aligned on carbon fiber papers were synthesized via a hydrothermal route with a two-step method and used as photoanodes in a self-powered photoelectrochemical cell-type (PEC) photodetector under visible light. TiO₂@Sn₃O₄ heterostructures exhibit a stable photocurrent of 180 μA, which is a 4-fold increase with respect to that of the Sn₃O₄ nanoflakes on carbon paper, and a two-order increase with respect to that of the TiO₂ NRs arrays. The evolution of hydrogen according to the photo-catalytic water-splitting process showed that Sn₃O₄/TiO₂ heterostructures have a good photocatalytic hydrogen evolution activity with the rate of 5.23 μmol h⁻¹, which is significantly larger than that of Sn₃O₄ nanoflakes (0.40 μmol h⁻¹) and TiO₂ nanorods (1.13 μmol h⁻¹). Furthermore, the mechanism behind this was discussed. The detector has reproducible and flexible properties, as well as an enhanced photosensitive performance.

Semiconductor heterostructures are regarded as an efficient way to improve the photocurrent in photoelectrochemical cell-type (PEC) photodetectors.     

Comparison of different pretreatments on the synergistic effect of cellulase and xylanase during the enzymatic hydrolysis of sugarcane bagasse

Sugarcane bagasse (SCB) substrates with different chemical compositions were prepared by different pretreatments including dilute acid (DA), acidic sodium chlorite (ASC), alkali solution (AS), and alkali hydrogen peroxide (AHP). The compositions and chemical structures of pretreated SCB were characterized by HPLC, FTIR, XRD, and SEM. The addition of xylanase can significantly boost cellulase to hydrolyze cellulose and xylan especially for AS and AHP treated substrates. The obvious linear relationships between lignin removal and substrate digestibility were observed. ASC treated substrates obtained the highest digestibility (98.87%) of cellulose due to sufficiently removing lignin from SCB, whereas AHP treated substrates achieved the highest digestibility (84.61%) of xylan by cleaving the acetyl group on xylan and extending delignification. It was found that the synergistic effects between cellulase and xylanase were substrate and time specific. The better degree of synergy for the sugar production was in the initial hydrolysis stage but decreased in the later hydrolysis stage.

The synergistic effects between cellulase and xylanase were substrate and time specific during the hydrolysis of pretreated SCB.     

Pressurized carbonization of mixed plastics into porous carbon sheets on magnesium oxide

Conversion of waste thermoplastics into porous carbons has attracted wide attention due to the requirement of recycling of large quantities of municipal solid waste. This work reports the preparation of porous carbon sheets on magnesium oxide from mixed thermoplastics including polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate in a closed autoclave at 500 °C. The influence of the weight ratio of magnesium oxide to mixed plastics on the yield and textural properties of the carbon was examined. The morphology and structure of the porous carbon were also characterized. The maximum BET surface area was 713 m² g⁻¹ at a weight ratio of MgO/polymer of 4 and the maximum pore volume was 5.27 cm³ g⁻¹ at a weight ratio of MgO/polymer of 6. The reaction mechanism was explored by analyzing the product distribution and composition of gas and liquid at different reaction times. Aromatics were the main source for the growth of carbon. Model experiments of carbonization of different aromatics were conducted to evaluate the carbonization reactivity of aromatics. Polycyclic aromatic hydrocarbons, especially acenes, produced more carbon.

Mixed thermoplastics were converted into porous carbon sheets over a magnesium oxide template with high yield in an autoclave reactor at 500 °C.     

A novel n-type CdS nanorods/p-type LaFeO3 heterojunction nanocomposite with enhanced visible-light photocatalytic performance

In this work, a novel n-type CdS nanorods/p-type LaFeO₃ (CdS NRs/LFO) nanocomposite was prepared, for the first time, via a facile solvothermal method. The as-prepared n-CdS NRs/p-LFO nanocomposite was characterized by using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible diffuse reflection spectroscopy (DRS), vibrating sample magnetometry (VSM), photoluminescence (PL) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. All data revealed the attachment of the LFO nanoparticle on the surface of CdS NRs. This novel nanocomposite was applied as a novel visible light photocatalyst for the degradation of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes under visible-light irradiation. Under optimized conditions, the degradation efficiency was 97.5% for MB, 80% for RhB and 85% for MO in the presence of H₂O₂ and over CdS NRs/LFO nanocomposite. The photocatalytic activity of CdS NRs/LFO was almost 16 and 8 times as high as those of the pristine CdS NRs and pure LFO, respectively. The photocatalytic activity was enhanced mainly due to the high efficiency in separation of electron–hole pairs induced by the remarkable synergistic effects of CdS and LFO semiconductors. After the photocatalytic reaction, the nanocomposite can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Trapping experiments indicated that ·OH radicals were the main reactive species for dye degradation in the present photocatalytic system. On the basis of the experimental results and estimated energy band positions, the mechanism for the enhanced photocatalytic activity was proposed.

A novel n–p CdS nanorods/LaFeO₃ (CdS NRs/LFO) heterojunction nanocomposite was prepared via a solvothermal route and applied as a visible-light photocatalyst for enhanced degradation of organic dye pollutants.     

Enhanced capacitive performance of cathodically reduced titania nanotubes pulsed deposited with Mn2O3 as supercapacitor electrode

A facile and simple pulse electrodeposition method was employed to deposit Mn₂O₃ nanoparticles on cathodically reduced titania nanotubes (R-TNTs) at different deposition time in the range of 3–15 min to investigate the influence of mass loading of Mn₂O₃ on the electrochemical performance of Mn₂O₃/R-TNTs nanocomposite for supercapacitor application. Mn₂O₃ nanoparticles were deposited on circumference of R-TNTs as well as in the nanotubes as revealed by FESEM images for all the deposited time. XPS result confirmed the presence of MnO₂ (Mn⁴⁺) and MnO (Mn²⁺) on the Mn₂O₃/R-TNTs composite which provide pseudocapacitive behaviour for the electrode. Mass loading of Mn₂O₃ increased linearly with deposition time as confirmed by EDX analysis. The sample deposited for 12 min exhibits the highest areal capacitance of 51 mF cm⁻² (which is 22 times enhancement over R-TNTs) at a current density of 0.1 mA cm⁻² and specific capacitance of 325 F g⁻¹ at 6 A g⁻¹. The sample also show a high-rate capability by retaining 80% of its capacitance even at higher current density of 30 A g⁻¹. Interestingly, it retained 98% of the capacitance over 5000 charge discharge cycles at 10 A g⁻¹ after initial drop to 95% at 200th cycles suggesting an excellent long-term chemical stability. A considerably low equivalent series resistance (ESR) and charge transfer resistance (R_ct) of 9.6 Ω and 0.4 Ω respectively was deduced from electrochemical impedance spectroscopy (EIS) analysis indicating good conductivity and improved charge transfer efficiency of Mn₂O₃/R-TNTs nanocomposite.

The mass loading of Mn₂O₃ by pulse electrodeposition (PED) onto reduced titania nanotubes (R-TNTs) greatly influences the electrochemical performance of the composite.     

Hierarchical TiO2 microspheres composed with nanoparticle-decorated nanorods for the enhanced photovoltaic performance in dye-sensitized solar cells

Hierarchical TiO₂ microspheres composed of nanoparticle-decorated nanorods (NP-MS) were successfully prepared with a two-step solvothermal method. There were three benefits associated with the use of NP-MS as a photoanode material. The decoration of nanoparticles improved the specific surface area and directly enhanced the dye loading ability. Rutile nanorods serving as electron transport paths resulted in fast electron transport and inhibited the charge recombination process. The three-dimensional hierarchical NP-MS structure supplied a strong light scattering capability and good connectivity. Thus, the hierarchical NP-MS combined the beneficial properties of improved scattering capability, dye loading ability, electron transport and inhibited charge recombination. Attributed to these advantages, a photoelectric conversion efficiency of up to 7.32% was obtained with the NP-MS film-based photoanode, resulting in a 43.5% enhancement compared to the efficiency of the P25 film-based photoanode (5.10%) at a similar thickness. Compared to traditional photoanodes with scattering layers or scattering centers, the fabrication process for single layered photoanodes with enhanced scattering capability was very simple. We believe the strategy would be beneficial for the easy fabrication of efficient dye-sensitized solar cells.

Hierarchical NP-MS combines the beneficial properties of improved scattering capability, dye loading ability, electron transport and inhibited charge recombination. The photoelectric conversion efficiency up to 7.32% has been obtained.     

Infusion pump performance with vertical displacement: effect of syringe pump and assembly type

OBJECTIVE: To evaluate the effect of different infusion pump models on continuity of drug delivery during vertical displacement of syringe pumps. DESIGN: Zero-drug delivery time (ZDDT), retrograde aspiration volume, and infusion bolus were recorded using the same syringe in three different models of syringe pump after lowering and elevating the pump. Compliance of each infusion assembly was measured using the occlusion release technique at 38 mmHg. RESULTS: Lowering the pump by 50 cm at an infusion rate of 1 ml/h resulted in ZDDT values ranging from 2.78 +/- 0.29 to 5.99 +/- 1.09 min. Elevating the syringe pump to its original position caused infusion boluses between 44.1 +/- 3.2 and 77.1 +/- 5.1 microl. The results demonstrated that there are large differences between syringe pump models (F = 66.8, df = 2/33, p < 0.0001) and between pumps of the same model (F = 21.3, df = 1/34, p < 0.0001). A similar pattern was found in retrograde aspiration volume and infusion bolus. CONCLUSION: All tested pumps led to clinically relevant flow irregularities during vertical displacement of the syringe pump. Thus, vertical displacement of any syringe pump connected to an infusion line delivering highly potent drugs at low infusion rates should be avoided. The variability across syringe pumps indicates that syringe pump design remains an area of potential further improvement for reducing the risk of adverse patient events.     

A new oxygen-rich energetic salt dihydrazine tetranitroethide: a promising explosive alternative with high density and good performance

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction. Compound 5 exhibits high crystal density (1.81 g cm⁻³) and impressive detonation velocity (9508 m s⁻¹) and detonation pressure (37.9 GPa), showing potential applications as a high performance explosive and a promising additive of propellants.

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction.

For applications in propellants, explosives and pyrotechnics, new energetic materials are required with high energy, insensitivity, high thermal stability and environment-friendly decomposition gases.¹ To achieve these goals, chemists have adopted a variety of strategies, such as construction of nitrogen-rich compounds,² energetic salts,³ metal organic framework (MOFs)⁴ and cage structure molecules.⁵ Oxygen balance (OB) is an important parameter to weigh the detonation performance of the nitrogen-rich compounds. Generally explosives may exhibit good performance when the OB close to zero.⁶ One conventional method of increasing the OB of energy materials is to introduce nitro groups, a typical high-energy and oxygen-rich substituent.⁷ Recently, gem-nitro and poly-nitro fragments, such as dinitromethyl,⁸ trinitroethyl⁹ and trinitromethyl,¹⁰ have been of interest to researchers. The compounds consisting of poly-nitro groups exhibit good OB, which largely improves their detonation velocities and pressures.¹¹ In our recent study,¹² we considered using tetranitroethylene instead of nitro as a pre-packaged module, linked to insensitive backbones, just like building blocks. The tetranitroethylene fragment has a high nitrogen content, a positive OB, and high energy within the molecule.¹³ The molecules consisting of the tetranitroethylene fragment are expected to be excellent energetic materials with superior properties.¹² But tetranitroethylene is an unstable intermediate, which is difficult to isolate.¹⁴ Hexnitroethane,¹⁵ a stable tetranitroethylene derivative, can be effectively used to synthetize poly-nitro bridged compound (Scheme 1). Previously, we discussed the possibility of constructing poly-nitro bridged-ring compounds with nitrogen-containing heterocycles and tetranitroethylene by using the Diels–Alder reaction.^12,16Open in a separate windowScheme 1Synthetic pathway for poly-nitro bridged compound.¹⁴Dipotassium tetranitroethide,¹⁷ another tetranitroethylene derivative, lead another thought to synthesize high energy salts with the tetranitroethane anion. The salt-based energetic materials often exhibit lower vapour pressure and higher densities than the non-ionic energetic materials.^3c In addition, the energetic salt can improve the properties by selecting different constituent ions.¹⁸ Based on the advantages of high-energy salt, we chose tetranitroethane anion and hydrazine cation to construct energetic salt by considering both energy and sensitivity. The synthetic route can be seen in Scheme 2. The good OB and large amounts of hydrogen-bonds prompt the target compound (dihydrazine tetranitroethide, 5) with suitable sensitivity and good performance. 5 possesses a crystal density of 1.81 g cm⁻³, detonation velocity of 9508 m s⁻¹ and detonation pressure of 37.9 GPa, which are higher than those of RDX. In addition, the salt-formation improves the carcinogenic and high toxic properties of hydrazine.Open in a separate windowScheme 2The route to synthesis of 5.The intermediate dipotassium tetranitroethide (3) was prepared from tetraiodoethylene (1) after two nitrification reactions, according to literature.¹⁹ The suspension of 3 in dichloromethane dissolves in concentrated sulfuric acid to give the solution of tetranitroethane (4) in dichloromethane. Treatment of the solution of 4 with hydrazine hydrate resulted in dihydrazine tetranitroethide (5), a yellow solid precipitated, that was confirmed by single crystal X-ray diffraction. Single crystal 5 is crystallized by using the method of the evaporation of water.Tetranitroethane 4 is also an unstable compound that is soluble in dichloromethane and difficult to isolate. It decomposed and released a brown gas as the solvent removed. Thus, we analysed the UV spectrum of the solution of 4, instead of the pure compound 4. Compared with the experimental and calculated UV spectrum of solution 4 (Fig. 1), we find that the maximum absorption wavelengths of the two curves match well, 240 nm (tested) and 239.5 nm (calculated). It can be inferred that compound 4 would be tetranitroethane.Open in a separate windowFig. 1The UV spectrum curve of tetranitroethane 4.Dihydrazine tetranitroethide 5 in the monoclinic space group C2/c with a good density of 1.81 g cm⁻³ (298 K). The gem-dinitro group is nearly planar, with the torsion angle of O5–N3–C2–N4, 179.52(17)°. However, the torsion angle of N3–C2–C2′–N4′ and N4–C2–C2′–N3′ are 77.57 (255)° and 77.57 (255)°, respectively, which shows the twist of adjacent dinitromethyl groups is caused by the steric effect. The strong hydrogen-bond interactions are presented between ammonium and nitro groups (Fig. 2b). The details of donor–acceptor distance are given in the ESI.^† Many studies have shown that the hydrogen-bonds enhance the stability of energetic molecules. At the molecular level, intermolecular hydrogen bonds between hydrazine cation and nitro groups play an important role in stabilizing energetic compounds. This kind of hydrogen-bonding interaction and cation–anion contact in the energetic salt is suggested as part of the explanation for closer packing, which causes the good density. As seen in Fig. 2c, the tetranitroethide anions are found in cross-stacking arrangements and layer by layer. While the hydrazine cation in the crystal, as the adhesive between the bricks, help to create a better stacking arrangement.Open in a separate windowFig. 2(a) Molecular structure of 5; (b) hydrogen-bonding interactions of 5 between hydrazine cation and tetranitroethide anion; (c) packing diagram of 5 (unit cell viewed along the b axis).The physical properties and calculated detonation performances are summarized in 20 Compound 5 has a detonation velocity of 9508 m s⁻¹ and a detonation pressure of P: 37.9 GPa, which is better than RDX (8748 m s⁻¹; 34.9 GPa) and similar to HMX (9320 m s⁻¹; 39.5 GPa). The sensitivities to impact and friction are 1.25 J and 34 N, respectively.Physical properties of dihydrazine tetranitroethide 5 and comparison with ADN, RDX and HMX

An ultrasonic-assisted synthesis of rice-straw-based porous carbon with high performance symmetric supercapacitors

Biomass porous carbon materials are ideal supercapacitor electrode materials due to their low price, rich source of raw materials and environmental friendliness. In this study, an ultrasonic-assisted method was applied to synthesize the rice-straw-based porous carbon (UPC). The obtained UPC exhibited a two-dimensional structure and high specific surface area. In addition, the electrochemical test results showed that the UPC with a 1 hour ultrasonic treatment and lower activation temperature of 600 °C (UPC-600) demonstrated optimal performance: high specific capacitances of 420 F g⁻¹ at 1.0 A g⁻¹ and 314 F g⁻¹ at a high current of 10 A g⁻¹. Significantly, the symmetric supercapacitors showed a high energy density of 11.1 W h kg⁻¹ and power density of 500 W kg⁻¹. After 10 000 cycles, 99.8% of the specific capacitance was retained at 20 A g⁻¹. These results indicate that UPC-600 is a promising candidate for supercapacitor electrode materials.

Rice-straw-based porous carbon was successfully prepared via an ultrasonic-assisted method to lower activation temperature and for ultra-stable electrode materials of symmetric supercapacitors.     

Dual-functional SiOC ceramics coating modified carbon fibers with enhanced microwave absorption performance

Multi-functional carbon fiber (CF) based composites have great potential as new-type microwave absorption materials (MAMs). However, it was still a huge challenge to integrate antioxidation and MA properties into CF based composites. Herein, the SiOC ceramics coating modified carbon fibers (SiOC/CFs) were prepared by a polymer precursor pyrolysis method. The X-ray photoelectron spectroscopy (XPS) revealed that the SiOC coating was composed of SiOC, SiO₂, and amorphous carbon phases. The SiOC ceramics as dual-functional coating not only heightened the oxidation temperature from 415 °C to 890 °C, but also highly improved the microwave absorbing ability from −12.60 dB to −47.50 dB. The enhanced MA performance could be attributed to multiple reflections in the cross-linked structure, various polarization relaxation processes, and the favorable impedance matching effect. The SiOC ceramics coating as a semiconductor could suppress the skin effect originating from the cross-linked CF network, thus leading to a favorable impedance matching behavior.

The SiOC ceramics coating modified carbon fibers improved anti-oxidation and refine microwave absorption properties.     

Interlaboratory study on thermal cycler performance in controlled PCR and random amplified polymorphic DNA analyses

BACKGROUND: Intercomparisons of PCR-based data between laboratories require an assurance of assay reproducibility. We performed an interlaboratory study to investigate the contribution made by a variety of thermal cyclers to PCR performance as measured by interblock reproducibility and intrablock repeatability. METHODS: Two standardized assays designed to minimize the introduction of non-thermal-cycler-dependent variations were evaluated by 18 laboratories in the United Kingdom, using 33 thermal cyclers of various makes and models. We used a single-product (590 bp) PCR, established in our laboratory as a robust and specific reaction. The second reaction, a multiproduct random amplified polymorphic DNA (RAPD) PCR, was known to be more susceptible to small changes in block temperature and was therefore considered a way of assessing block uniformity with respect to temperature. Assay repeatability data were analyzed with respect to temperature calibration status, the type of temperature control mechanism, thermal cycler age, and the presence of oil overlay or heated lid systems. RESULTS: All (100%) of the laboratories produced the correct target for the single-product PCR assay, although substantial variation in yield in replicate reactions was observed in 9.4% of these. The RAPD reaction generated results that varied extensively both within the same block and between different thermal cyclers. For eight replicates of a positive sample, 88% intrablock repeatability was demonstrated in calibrated thermal cyclers, which decreased to 63% in noncalibrated instruments. CONCLUSIONS: Irrespective of the make and model of thermal cycler, temperature-calibrated instruments consistently generated more repeatable RAPD data than noncalibrated instruments. Guidelines are offered on optimizing and monitoring thermal cycler performance.     

A p-type multi-wall carbon nanotube/Te nanorod composite with enhanced thermoelectric performance

In this study, multi-walled carbon nanotube (MWCNT)/tellurium (Te) nanorod composites with various MWCNT contents are prepared and their thermoelectric properties are investigated. The composite samples are prepared by mixing Te nanorods with surface-treated MWCNTs. Te nanorods are synthesized by solution phase mixing using polyvinylpyrrolidone (PVP). The MWCNTs used in this study are surface-treated with a solution consisting of H₂SO₄ and HNO₃. With increasing MWCNT content, the composite samples exhibit a reduction in the Seebeck coefficient and enhanced electrical conductivity. The maximum power factor of 5.53 μW m K⁻² is observed at 2% MWCNT at room temperature. The thermal conductivity of the composite reduced after the introduction of MWCNTs into the Te nanorod matrix; this is attributed to the generation of heterostructured interfaces between MWCNTs and the Te nanorods. At room temperature, the composites containing 2% MWCNTs exhibited the maximum thermoelectric figure of merit (ZT), which is ∼3.91 times larger than that of pure Te nanorods.

In this study, multi-walled carbon nanotube (MWCNT)/tellurium (Te) nanorod composites with various MWCNT contents are prepared and their thermoelectric properties are investigated.     

α-Fe2O3 hollow meso–microspheres grown on graphene sheets function as a promising counter electrode in dye-sensitized solar cells

Although nanoparticles, nanorods, and nanosheets of α-Fe₂O₃ on graphene sheets have been synthesized, it remains a challenge to grow 3D α-Fe₂O₃ nanomaterials with more sophisticated compositions and structures on the graphene sheets. Herein, we demonstrate a facile solvothermal route under controlled conditions to successfully fabricate 3D α-Fe₂O₃ hollow meso–microspheres on the graphene sheets (α-Fe₂O₃/RGO HMM). Attributed to the combination of the catalytic features of α-Fe₂O₃ hollow meso–microspheres and the high conductivity of graphene, α-Fe₂O₃/RGO HMM exhibited promising electrocatalytic performance as a counter electrode in dye-sensitized solar cells (DSSCs). The DSSCs fabricated with α-Fe₂O₃ HMM displayed high power conversion efficiency of 7.28%, which is comparable with that of Pt (7.71%).

Although nanoparticles, nanorods, and nanosheets of α-Fe₂O₃ on graphene sheets have been synthesized, it remains a challenge to grow 3D α-Fe₂O₃ nanomaterials with more sophisticated compositions and structures on the graphene sheets.     

Electrochemical performance of activated carbon fiber with hydrogen bond-induced high sulfur/nitrogen doping

The sulfur/nitrogen co-doped activated carbon fiber (S/N-ACF) is prepared by the thermal treatment of thiourea-bonded hydroxyl-rich carbon fiber, which can bond the decomposition products of thiourea through hydrogen bond interaction to avoid the significant loss of sulfur and nitrogen sources during the thermal treatment process. The sulfur/nitrogen co-doped carbon fiber (S/N-CF) is prepared by the thermal treatment of thiourea-adsorbed carbon fiber. The doping degree of the carbon fiber is improved by reasonable strategy. S/N-ACF shows a higher amount of S/N doping (4.56 at% N and 3.16 at% S) than S/N-CF (1.25 at% N and 0.61 at% S). S/N-ACF with high S/N doping level involves highly active sites to improve the capacitive performance, and high delocalization electron to improve the conductivity and rate capability when compared with the normal S/N co-doped carbon fiber (S/N-CF). Accordingly, the specific capacitance increases from 1196 mF cm⁻² for S/N-CF to 2704 mF cm⁻² for S/N-ACF at 1 mA cm⁻². The all-solid-state flexible S/N-ACF supercapacitor achieves 184.7 μW h cm⁻² at 350 μW cm⁻². The results suggest that S/N-ACF has potential application as a CF-based supercapacitor electrode material.

Sulfur/nitrogen co-doped activated carbon fiber is prepared by thermal treatment of thiourea-bonded hydroxyl-rich carbon fiber, which achieves high doping level and electrochemical performance.     

Nitrogen and sulfur co-doped cobalt carbon catalysts for ethylbenzene oxidation with synergistically enhanced performance

Heteroatom doping has been demonstrated to be an effective strategy for improving the performance of catalysts. In this paper, cobalt carbon catalysts co-doped with nitrogen and sulfur (N and S) were synthesized through a hydrothermal method with chelate composites involving melamine, thioglycolic acid (C₂H₄O₂S), and tetrahydrate cobalt acetate (Co(OAc)₂·4H₂O). In addition, the selective oxidation of ethylbenzene under solvent-free conditions with molecular oxygen was used as a probe reaction to evaluate the activity of the catalysts. The optimized catalyst shows an ethylbenzene conversion of 48% with an acetophenone selectivity of 85%. Furthermore, the catalysts were systematically characterized by techniques such as TEM, SEM, XRD, Raman, and XPS. The results reveal that the species of cobalt sulfides and synergistic effects between N and S has inserted a key influence on their catalytic performance.

Co-N-S-C catalysts with rod-like structures were synthesized for the selective oxidation of ethylbenzene using O₂ as an oxidant.     

Ultrafine MnO2 nanowires grown on RGO-coated carbon cloth as a binder-free and flexible supercapacitor electrode with high performance

Reduced graphene oxide coated carbon cloth has been used as a substrate for the growth of ultrafine MnO₂ nanowires (CC/RGO/MnO₂), forming binder-free and flexible supercapacitor electrode materials. The experimental results indicate that a maximum area-specific capacitance of 506.8 mF cm⁻² was gained from the CC/RGO/MnO₂ electrode at the current density of 0.128 mA cm⁻². Furthermore, the electrode exhibits excellent cycling stability (98.6% specific capacitance was still retained after 10 000 galvanostatic charge–discharge (GCD) tests when the current density was 1.28 mA cm⁻²). What''s more, the area-specific capacitance of the CC/RGO/MnO₂ electrode was hardly changed, when the electrode was operated under bending mechanical conditions. In addition, the charge storage performance and mechanism of the MnO₂ nanostructures was discussed.

Reduced graphene oxide coated carbon cloth has been used as a substrate for the growth of ultrafine MnO₂ nanowires (CC/RGO/MnO₂), forming binder-free and flexible supercapacitor electrode materials.     

Lightweight MWCNT/hollow mesoporous carbon/WPU composite material with excellent electromagnetic shielding performance

With the rapid increase of intelligent communication equipment, electromagnetic pollution is becoming more and more serious, and the research and application of high-performance electromagnetic shielding materials have attracted great attention from the academic and engineering circles. Traditional metal-based electromagnetic shielding materials have high reflection loss, high density, and are difficult to process. Polymer-based materials with carbon materials as fillers have the advantages of flexibility, light weight, corrosion resistance and low processing costs. They have become the most important materials in the field of electromagnetic shielding in recent years. However, the conductivity of conductive polymer materials is not high. Therefore, improving the electromagnetic shielding performance and the proportion of absorption loss under low density conditions have become key issues for polymer-based electromagnetic shielding materials. MWCNT/MCHMs/WPU composites were prepared by a solution mixing method, with 20 wt%, 40 wt%, 60 wt% MWCNTs and 40 wt% MWCNT/10 wt% MCHMs as fillers. By comparing the effects of different MWCNT content and MCHMs on the dielectric properties, electromagnetic shielding properties and mechanical properties of the MWCNT/MCHMs/WPU composites, the relationship between the structure and properties of the composites has been explored. The 0.6 mm WPU/60 wt% MWCNT composite has an electrical conductivity of 95.4 S m⁻¹ and an electromagnetic shielding effectiveness of 40 dB in the X band. Adding 10 wt% MCHMs to the WPU/40 wt% MWCNT composite material can significantly improve the composite. The δ of the material increased from 51.2 S m⁻¹ to 55.4 S m⁻¹, and the SE increased from 30 dB to 33 dB. The research results show that the increase in MWCNT content and MCHMs is beneficial to improving the electrical conductivity and electromagnetic shielding performance of the composite materials.

The interaction between electromagnetic waves and conductive fillers shielding performance.