Search

Nanostructured carbon materials have attracted enormous attention in last two decades due to their unique chemical, electrical, and mechanical properties. In this work, amorphous hollow carbon spheres (AHCSs) with diameters in the range of 100-750 nm, which are dispersed among bent graphitized carbon nanotubes, are synthesized by using radio frequency plasma enhanced chemical vapor deposition in mixed CH/H gases. The carbon spheres were characterized with scanning electron microscope, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and transmission electron microscopy. It is found that MgO and Co/Ni nanoparticles as well as hydrogen play crucial roles in the formation of AHCSs. Moreover, a possible growth mechanism of AHCSs was proposed. The results of this study provide new insights into the fundamental understanding of nonstructural carbon materials toward applications in nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: Poly(vinylidene fluoride) (PVDF)/clay nanocomposites with different clay contents were prepared by melt intercalation. The effects of clay on crystalline structure of PVDF were characterized, compared and discussed. For the nanocomposite containing 0.4 wt.% clay, the α phase coexists with the γ phase in the PVDF matrix in room temperature, however, the γ phase is unstable at 160 °C. When clay contents in the nanocomposites are greater 1 wt.%, the α phase coexists with the β phase. The β phase remains unchanged even after annealing. With increasing clay content, the location of the (021) reflection of α phase shifts to lower angle, while that of the (002) refection shifts to higher angle. Clay loading also induces the imperfection of α crystals. The results are attributed to the nucleation of PVDF on nanometer-size clay layers and the confining effect of nanometer-size clay on PVDF. [Copyright &y& Elsevier]

The development of low-price and highly efficient catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has always been challenging with regard to water splitting. Pyrrhotite Fe 7 S 8 has become a research hotspot due to its abundant reserves, high electrical conductivity and excellent catalytic activity. In general, introducing metal heteroatoms into transition metal sulfides (TMSs) can effectively enhance the activity and stability of TMSs. Herein, Co-doped pyrrhotite Fe 7 S 8 nanosheets were obtained by a straightforward two-step method consisting of hydrothermal treatment followed by subsequent heat treatment. Results from XPS analysis and contact angle measurements showed that doping optimized the chemical environment around iron atoms and enhanced the adsorption of water molecules on the surface of Fe 7 S 8 , thereby greatly improving the electrocatalytic efficiency of water electrolysis. Compared with other counterparts, Co 0 · 95 Fe 6 · 05 S 8 exhibited superior OER activity with an overpotential of 311 mV at a current density of 10 mA cm−2, and higher performance towards HER with an overpotential of 284 mV at 10 mA cm−2 in alkaline solution. In sum, Co 0 · 95 Fe 6 · 05 S 8 is promising as a bifunctional catalyst for water splitting under alkaline conditions. [ABSTRACT FROM AUTHOR]

It is a big challenge to construct proton-conductive materials for practical applications operating at high temperatures and low humidity. Herein, we propose an ionothermal strategy for the preparation of highly stable NH2-MIL-53(Al)it nanomaterials with high proton conductivity. The crystalline structure and the direct incorporation of the 1-ethyl-3-methyl-imidazolium ionic liquid within NH2-MIL-53(Al)it are identified by XRD, TG/DTA and IR techniques. The as-prepared NH2-MIL-53(Al)it exhibits a high proton conductivity of 3.0 × 10−5 S cm−1 at 80 °C and low relative humidity of ∼26%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni(OH)2/vertically oriented graphene nanosheets (V-GNs) was prepared. [•] Ni(OH)2/V-GNs had enhanced specific capacitance, cycling reversibility and stability. [•] Performance of Ni(OH)2/GNs/NF-AC asymmetric supercapacitor was studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] Co(OH)2/graphene and Co(OH)2/amorphous carbon were prepared. [•] Co(OH)2/graphene reveals a high cycling stability even at a high current density. [•] Co(OH)2/amorphous carbon exhibits a high specific capacitance. [•] Influence of carbon on pseudocapacitive behaviors of Co(OH)2 has been studied. [ABSTRACT FROM AUTHOR]

Graphene oxide nanosheet is an ideal platform to capture nanoparticles for highly efficient catalysis, electrochemical sensing and biosensing. In this work, we have described a simple synthesis method for preparation graphene oxide- nanohybrid. nanodots with an average size of 1.6 nm uniformly dispersed on the surface of graphene oxide. The well-defined nanostructure has been characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanohybrid also exhibits enhanced catalytic activity toward the reduction of 4-nitrophenol by . Comparing with pure nanodots and graphene oxide, graphene oxide- nanohybrid shows the highest catalytic activity. This approach not only suggests a wide potential application of graphene oxide nanosheet as a host material for supporting a variety of nanoparticles, but also provides a new approach for the fabrication of graphene-based nanohybrids with multiple physical and chemical properties. Graphene oxide-Au nanohybrid has been prepared to enhance the catalytic activity toward the reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

Abstract: A convenient and efficient preparation method for separation graphene oxide with well-defined size distribution is developed using a centrifugation technique. The graded profile of graphene oxide nanosheets with narrow size distribution is effectively controlled by varying the centrifugation speed. The results show that the oxygen content of graphene oxide is highly dependent on their size distribution. Graphene oxide nanosheet with large size shows a red-shift in UV–vis absorption spectra, compared to graphene oxide with small size. This phenomenon is interpretation by a density functional theory calculation. The present work will provide a simple method to prepare graphene oxide nanosheets with controllable size distribution and C/O ratio, which will be valuable for the functionalization of graphene-based hybrids and the fabrication of graphene nano-devices. [Copyright &y& Elsevier]

Graphite nanosheets have been grown on Ni foam by radio-frequency plasma-enhanced chemical vapor deposition, which are used as substrates for electrodepositon of Ni(OH)2 with a porous and 3D nanostructure. The Ni foam/graphite nanosheets/Ni(OH)2 electrode has a high specific capacitance of 1667 F g−1 and the specific capacitance can maintain 93.3% after 700 cycles at the current density of 60 A g−1 in 1 M KOH. [ABSTRACT FROM AUTHOR]

Abstract: Vertically aligned graphene nanosheets have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition on nickel-foam current collectors and that have been used as substrates for cathodic electrodeposition of cobalt hydroxide nanosheets in Co(NO3)2 aqueous solution. Raman spectrum exhibits that high-quality graphene nanosheets have been synthesized. The composites have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and galvanostatic charge/discharge. It indicates that hexagonal Co(OH)2 has a network microstructure, consisting of interlaced sheets with the thickness of 12 nm coated on the graphene nanosheets. The binder-free nano-electrode exhibits excellent pseudocapacitive behavior with pseudocapacitances of 693.8 and 506.2 Fg−1 at current density of 2 and 32 Ag−1, respectively, in a potential range of −0.1–0.45 V. The capacitance can retain about 91.9% after 3000 charge–discharge cycles at 40 Ag−1, which is higher than that of Co(OH)2/Ni foam (after 2000 cycles, 75.5% of initial capacitance remains). The introduction of graphene between Co(OH)2 and Ni foam demonstrates an enhancement of electrochemical stability of the nano-electrodes. [Copyright &y& Elsevier]

Abstract: Cubic ZnSnO3 nanocages, a geometrical cube-shape with a hierarchical structure composed of small nanoparticles as secondary units, are successfully synthesized via a facile hydrothermal process. These ZnSnO3 nanocages have hollow interiors and good-permeation surfaces, and are used for detecting different gases such as ethanol (C2H5OH), formaldehyde (HCHO), and hydrogen sulfide (H2S). These ZnSnO3 nanocages show good response, selectivity, response and recovery characteristics to H2S. It is found that ZnSnO3 nanocages have a response of 17.6–50ppm H2S at the optimal operating temperature of 310°C and the response time is shorter than 20s. [Copyright &y& Elsevier]

Perovskites are solution-processed, high-performance semiconductors of interest in low-cost photovoltaics. The interfaces between the perovskite photoactive layers and the top and bottom contacts are crucial for efficient charge transport and minimizing trapping. Control of the collection of charge carriers at these interfaces is decisive to device performance. Here, we review recent progress in the realization of efficient perovskite solar cells using cheap, easily processed, stable, carbon-based interlayers. Interface materials including graphene, carbon nanotubes, fullerenes, graphene quantum dots and carbon dots are introduced and their influence on device performance is discussed. • The use of carbon nanomaterials in perovskite photovoltaic devices is reviewed. • Carbon nanomaterials allow precision tuning of their properties to serve as both electron- and hole-transporting material. • Carbon nanomaterials facilitate an optimized charge balance, device stability, and efficiency. [ABSTRACT FROM AUTHOR]