Three-dimensional flower-like and hierarchical porous carbon material (FHPC) has been fabricated through a simple and efficient carbonization method followed by chemical activation with flower-like ...ZnO as template and pitch as carbon precursor. The hierarchical porous structure is composed of numerous micropores and well-defined mesopores in the interconnected macroporous walls. The FHPC electrode can achieve a relatively high capacitance of 294Fg−1 at a scan rate of 2mVs−1 and excellent rate capability (71% retention at 500mVs−1) with superior cycle stability (only 2% loss after 5000 cycles) in 6molL−1 KOH electrolyte. The symmetric supercapacitor fabricated with FHPC electrodes delivers a high energy density of 15.9Whkg−1 at a power density of 317.5Wkg−1 operated in the voltage range of 0–1.8V in 1molL−1 Na2SO4 aqueous electrolyte.
We demonstrated the fabrication of functionalized graphene nanosheets via low temperature (300 °C) treatment of graphite oxide with a slow heating rate using Mg(OH)2 nanosheets as template. Because ...of its dented sheet with high surface area, a certain amount of oxygen-containing groups, and low pore volume, the as-obtained graphene delivers both ultrahigh specific gravimetric and volumetric capacitances of 456 F g–1 and 470 F cm–3, almost 3.7 times and 3.3 times higher than hydrazine reduced graphene, respectively. Especially, the obtained volumetric capacitance is the highest value so far reported for carbon materials in aqueous electrolytes. More importantly, the assembled supercapacitor exhibits an ultrahigh volumetric energy density of 27.2 Wh L–1, which is among the highest values for carbon materials in aqueous electrolytes, as well as excellent cycling stability with 134% of its initial capacitance after 10 000 cycles. Therefore, the present work holds a great promise for future design and large-scale production of high performance graphene electrodes for portable energy storage devices.
Understanding the effects of changing climate and long-term human activities on soil organic carbon (SOC) and the mediating roles of microorganisms is critical to maintain soil C stability in ...agricultural ecosystem. Here, we took samples from a long-term soil transplantation experiment, in which large transects of Mollisol soil in a cold temperate region were translocated to warm temperate and mid-subtropical regions to simulate different climate conditions, with a fertilization treatment on top. This study aimed to understand fertilization effect on SOC and the role of soil microorganisms featured after long-term community incubation in warm climates. After 12 years of soil transplantation, fertilization led to less reduction of SOC, in which aromatic C increased and the consumption of O-alkyl C and carbonyl C decreased. Soil live microbes were analyzed using propidium monoazide to remove DNAs from dead cells, and their network modulization explained 60.4% of variations in soil labile C. Single-cell Raman spectroscopy combined with D
O isotope labeling indicated a higher metabolic activity of live microbes to use easily degradable C after soil transplantation. Compared with non-fertilization, there was a significant decrease in soil α- and β-glucosidase and delay on microbial growth with fertilization in warmer climate. Moreover, fertilization significantly increased microbial necromass as indicated by amino sugar content, and its contribution to soil resistant C reached 22.3%. This study evidentially highlights the substantial contribution of soil microbial metabolism and necromass to refractory C of SOC with addition of nutrients in the long-term.
Two-dimensional mesoporous carbon sheet-like framework (MCSF) material has been prepared using mesoporous SiO2 nanosheet as template and coal tar pitch as carbon precursor. MCSF sheets consisting of ...numerous mesopores have a specific surface area of 582.7m2g−1. As a result, the MCSF electrode possesses a maximum specific capacitance of 264Fg−1 at 5mVs−1, excellent rate capability (74% retention ratio at 1000mVs−1), and impressive cycling stability with 91% initial capacitance retained after 5000 cycles at 200mVs−1 in 6molL−1 KOH. MCSF symmetric supercapacitor exhibits a maximum energy density of 9.6Whkg−1 at 5mVs−1 and a maximum power density of 119.4kWkg−1 based on the total mass of the two electrodes in 1molL−1 Na2SO4 electrolyte.
•A hierarchical three-dimensional composite (rGO/LDH) was prepared and well characterized.•Uranium (VI) removal using rGO/LDH was studied for the first time.•The adsorption process for uranium (VI) ...removal was studied in detail.•rGO/LDH exhibited fast and efficient sorption for uranium (VI).
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This study presents a facile route for the fabrication of a hierarchical three-dimensional composite (layered double hydroxide/graphene). The composite was obtained via in situ growth of layered double hydroxide (LDH) nanosheet arrays onto graphene sheets. The materials were characterized by transmission electron microscopy, scanning electron microscope, Fourier-transform infrared spectroscopy, X-ray diffraction and Brunauer–Emmett–Teller surface area measurement. This particularly structured composite has a large specific surface area and typical mesoporous characteristics, which are favorable for achieving high adsorption performance. The influence of conditions for uranium adsorption, including pH of aqueous solution, adsorbent dose, shaking time, and temperature were investigated. The results reveal that the maximum adsorption capacity of the layered double hydroxide/graphene toward uranium (VI) is 277.80mgg−1, displaying a high efficiency for the removal of uranium (VI) from aqueous solution. The thermodynamic parameters, such as ΔH°, ΔS°, and ΔG° show that the process is endothermic and spontaneous. The kinetic adsorption can be described by a pseudo-second-order rate equation. This work describes an efficient, fast, and convenient approach for the removal of uranium (VI) from aqueous solutions.
A facile approach has been developed to fabricate mesoporous PANI film on ultra-thin graphene nanosheet (G-mPANI) hybrid by in situ polymerization using graphene-mesoporous silica composite as ...template. Due to its mesoporous structure, over-all conductive network, G-mPANI electrode displays a specific capacitance of 749 F g-1 at 0.5 A g-1 with excellent rate capability (remains 73% even at 5.0 A g-1), much higher than that of pristine PANI electrode (315 F g-1 at 0.5 A g-1, 39% retention at 5.0 A g-1) in 1 mol L-1 H2SO4 aqueous solution. More interestingly, the G-mPANI hybrid can maintain 88% of its initial capacitance compared to 45% for pristine PANI after 1000 cycles, suggesting a superior electrochemical cyclic stability.
•Synthesis of the HKUST-1 with mesoporous structure.•Exploration of the new application of MOFs materials in uranium removal.•Development of a high-efficiency adsorbent for uranium.
This paper ...reports on the efficient adsorption for uranium by metal-organic frameworks (MOFs) HKUST-1 from aqueous solution. The structure of the prepared HKUST-1 was characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption/desorption analysis. The influences of different experimental parameters were studied, such as initial solution pH, adsorbent dosage, adsorption time, temperature and various concentrations of uranium uptake. The thermodynamic parameters including Gibbs free energy (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) for the process were calculated using the Langmuir constants. The results showed that the equilibrium data fitted well to Langmuir model in the studied range of uranium concentration (10mg/L–800mg/L) and temperature (298K–318K), and the HKUST-1 exhibited the highest uptake for uranium at 318K, at the initial solution pH value of 6 and at the initial uranium concentration of 800mg/L. The thermodynamics of uranium/HKUST-1 system indicated the spontaneous and endothermic nature of the process. And the kinetics of the adsorption process followed the pseudo-second-order kinetics model.
Su, Yang, Zhou, and Tang proposed several new classes of optimal autocorrelation interleaved quaternary sequences with period 2
n
from the twin-prime sequence pairs or GMW sequence pairs. In this ...paper, we determine the 4-adic complexity of these quaternary sequences by using the correlation function. Our results show that the 4-adic complexity of these quaternary sequences exceeds
2
n
-
16
6
, so that they are safe enough to resist the attack of the rational approximation algorithm.
Oleaginous microalgae are promising feedstock for biofuels, yet the genetic diversity, origin and evolution of oleaginous traits remain largely unknown. Here we present a detailed phylogenomic ...analysis of five oleaginous Nannochloropsis species (a total of six strains) and one time-series transcriptome dataset for triacylglycerol (TAG) synthesis on one representative strain. Despite small genome sizes, high coding potential and relative paucity of mobile elements, the genomes feature small cores of ca. 2,700 protein-coding genes and a large pan-genome of >38,000 genes. The six genomes share key oleaginous traits, such as the enrichment of selected lipid biosynthesis genes and certain glycoside hydrolase genes that potentially shift carbon flux from chrysolaminaran to TAG synthesis. The eleven type II diacylglycerol acyltransferase genes (DGAT-2) in every strain, each expressed during TAG synthesis, likely originated from three ancient genomes, including the secondary endosymbiosis host and the engulfed green and red algae. Horizontal gene transfers were inferred in most lipid synthesis nodes with expanded gene doses and many glycoside hydrolase genes. Thus multiple genome pooling and horizontal genetic exchange, together with selective inheritance of lipid synthesis genes and species-specific gene loss, have led to the enormous genetic apparatus for oleaginousness and the wide genomic divergence among present-day Nannochloropsis. These findings have important implications in the screening and genetic engineering of microalgae for biofuels.
A carbon material consisting of hollow carbon spheres anchored on the surface of carbon nanotubes (CNT–HCS) has been synthesized by an easy chemical vapor deposition process using a CNT–MnO2 hybrid ...as template. An electrode made of this material exhibits a maximum specific capacitance of 201.5Fg−1 at 0.5Ag−1 and excellent rate performance (69% retention ratio at 20Ag−1). It has impressive cycling stability with 90% initial capacitance retained after 5000 cycles at 5Ag−1 in 6molL−1 KOH. Symmetric supercapacitors based on CNT–HCS achieve a maximum energy density of 11.3Whkg−1 and power density of 11.8kWkg−1 operated within a wide potential range of 0–1.6V in 1.0molL−1 Na2SO4 solution.
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