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- Asymmetric supercapacitor (1)
- Binary mixtures (1)
- Density measurements (1)
- EURAMET.QM-K111 (1)
- Electrochemical behavior (1)
- GERG-2008 equation of state (1)
- Graphene oxide (1)
- Nanocluster (1)
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- Ni-Co oxide (1)
The experimental density data of the binary System nitrogen−hydrogen available at the time of the development of the equation of state for natural gases and related mixtures, GERG-2008, were limited to hydrogen contents higher than 0.15 (amount-of-substance fraction) and temperatures above 270 K. This work provides accurate experimental (p, ρ, T) data for three binary mixtures of nitrogen and hydrogen: (0.95 N2 + 0.05 H2), (0.90 N2 + 0.10 H2), and (0.50 N2 + 0.50 H2) at temperatures of 240, 250, 260, 275, 300, 325, and 350 K, thus extending the range of available experimental data to low hydrogen contents and low temperatures. The density measurements were performed by using a single-sinker densimeter with magnetic suspension coupling at pressures up to 20 MPa. Experimental data were compared with the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state. The relative deviations of the experimental data from both equations of state were within the estimated uncertainty value of the equations. Therefore, the experimental data agree very well with the values estimated from the equations. The virial coefficients B(T,x), C(T,x), and D(T,x) as well as the second interaction virial coefficient B12(T) for the nitrogen−hydrogen binary system were also calculated from the experimental data set at temperatures from 240 to 350 K. The resulting values agree with those from literature.
This key comparison aims to assess the core capabilities of the participants in gas analysis. Such competences include, among others, the capabilities to prepare Primary Standard gas Mixtures (PSMs), perform the necessary purity analysis on the materials used in the gas mixture preparation, the verification of the composition of newly prepared PSMs against existing ones, and the capability of calibrating the composition of a gas mixture. According to the Strategy for Key Comparisons of the Gas Analysis Working Group, this key comparison is classified as an RMO track A key comparison.
The artefacts were binary mixtures of propane in nitrogen at a nominal amount-of-substance fraction level of 1000 μmol/mol. The values and uncertainties from the gravimetric gas mixture preparation were used as key comparison reference values (KCRVs). Each transfer standard had its own KCRV. The results are generally good. All results are within ± 1 % of the KCRV.
Novel MnS nanoclusters were synthesized on nickel foam (NF) using a successive ionic layer adsorption and reaction (SILAR) method. MnS nanoclusters with different sizes were obtained by varying the number of deposition cycles. The crystal structure, chemical composition, and surface microstructure of the electrodes were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field Emission scanning electron microscopy, and high-resolution transmission electron microscopy. The electrochemical behavior of the MnS nanoclusters was examined by cyclic voltammetry, galvanostatic charge–discharge, cycling test, and electrochemical impedance spectroscopy. The MnS nanoclusters prepared with 90 SILAR cycles showed the best supercapacitance in a 6 M KOH aqueous electrolyte with a specific capacitance of 828 F/g at a scan rate of 5 mV/s and cycling stability of 85.2 % after 5000 charge–discharge cycles.
Moreover, an asymmetric supercapacitor (ASC) was assembled with the as-prepared MnS electrode on NF as the positive electrode, hydrothermally prepared reduced graphene oxide (rGO) on NF as the negative electrode, and PVA–KOH gel as the electrolyte. The MnS@NF//rGO@NF ASC showed excellent electrochemical performance with maximum energy and power densities of 34.1 Wh/kg and 12.8 kW/kg, respectively. The ASC also showed a capacitive retention of 86.5 % after 2000 charge–discharge cycles, highlighting its practical application for energy storage.
Nanocomposites of Ag-ZnFe2O4@reduced graphene oxide (rGO) were synthesized using a one-pot microwave-assisted self-assembly method. The morphology and structure of the Ag-ZnFe2O4@rGO nanocomposites were characterized. The nanocomposites formed with 15.2 wt% rGO showed excellent adsorption properties and high photocatalytic activity for the degradation of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO). The synergistic interactions between Ag, ZnFe2O4, and rGO decreased the aggregation of the nanoparticles (NPs) and increased the surface area, resulting in better absorption in both UV and visible light. Such a structure was helpful for separating the photoexcited electron-hole pairs and accelerating electron transfer. Electrochemical impedance spectroscopy (EIS) revealed a smaller resistance in the solid-state interface layer and charge transfer on the composite surface than that of the bare ZnFe2O4 NPs and ZnFe2O4@rGO nanocomposite. The Ag-ZnFe2O4@rGO nanocomposite could be recovered easily by a magnet and reused five times with no significant decrease in photocatalytic activity. The as-prepared Ag-ZnFe2O4@rGO nanocomposite catalyst could be applied to the removal of hard-to-degrade waste materials owing to its high efficiency in both UV and visible light and its excellent reusability.
Supercapacitors are an emerging energy-storage system with a wide range of potential applications. In this study, highly porous nickel-cobalt-oxide@reduced graphene oxide (Ni-Co-O@RGO-s) nanosheets were synthesized as an active material for supercapacitors using a surfactant-assisted microwave irradiation technique. The RGO-modified nanocomposite showed a larger specific area, better conductivity, and lower resistivity than the unmodified nanocomposite because the RGO facilitated faster ion diffusion/transport for improved redox activity. The synergistic effect of Ni-Co-O@RGO-s resulted in a high capacitance of 1903 F/g (at 0.8 A/g) in a mixed KOH/redox active K3Fe(CN)6 electrolyte. The asymmetric Ni-Co-O@RGO-s//AC supercapacitor device yielded a high energy density and power density of 39 Wh/kg and 7500 W/kg, respectively. The porous structure and combination of redox couples from both the electrode and electrolyte provided a highly synergistic effect, which improved the performance of the supercapacitor device.