Ultrahigh-content nitrogen-decorated nanoporous carbon derived from metal organic frameworks and its application in supercapacitors

Single electric double-layer capacitors cannot meet the growing demand for energy due to their insufficient energy density. Generally speaking, the supercapacitors introduced with pseudo-capacitance by doping heteroatoms (N, O) in porous carbon materials can obtain much higher capacitance than electric double-layer capacitors. In view of above merits, in this study, nanoporous carbon materials with ultrahigh N enrichment (14.23 wt%) and high specific surface area (942 m2 g−1) by in situ introduction of N-doped MOF (ZTIF-1, Organic ligands 5-methyltetrazole/C2H4N4) were produced. It was found that as supercapacitors' electrode materials, these nanoporous carbons exhibit a capacitance as high as 272 F g-1 at 0.1 A g−1, and an excellent cycle life (almost no attenuation after 10,000 cycles.). Moreover, the symmetric supercapacitors were assembled to further investigate the actual capacitive performance, and the capacitance shows up to 154 F g-1 at 0.1 A g−1. Such excellent properties may be attributed to a combination of a high specific surface area, ultrahigh nitrogen content and hierarchically porous structure. The results shown in this study fully demonstrate that the nanoporous carbon materials containing ultrahigh nitrogen content can be used as a potential electrode material in supercapacitors

Facile synthesis of ultrahigh-surface-area hollow carbon nanospheres and their application in lithium-sulfur batteries

Hollow carbon nanospheres (HCNs) with specific surface areas up to 2949 m2 g−1 and pore volume up to 2.9 cm3 g−1 were successfully synthesized from polyaniline‐co‐polypyrrole hollow nanospheres by carbonization and CO2 activation. The cavity diameter and wall thickness of HCNs can be easily controlled by activation time. Owing to their large inner cavity and enclosed structure, HCNs are desirable carriers for encapsulating sulfur. To better understand the effects of pore characteristics and sulfur contents on the performances of lithium‐sulfur batteries, three composites of HCNs and sulfur are prepared and studied in detail. The composites of HCNs with moderate specific surface areas and suitable sulfur content present a better performance. The first discharge capacity of this composite reaches 1401 mAh g−1 at 0.2 C. Even after 200 cycles, the discharge capacity remains at 626 mAh g−1

Topographic knowledge-aware network for automatic small-scale impact crater detection from lunar digital elevation models

Impact craters represent the most prevalent and prominent topographical features on the surfaces of planets. They provide crucial insights into the internal and surface-level geological activities of planets but are difficult to identify from digital topographic data due to heterogeneous planetary surfaces and lack of distinguishing features. Previous studies, which implemented convolutional neural networks to automatically detect the planetary impact craters, focus on designing the state-of-the-art architectures to achieve optimal detection performance, without taking topographic knowledge into consideration. Therefore, we construct a topographic knowledge-aware network aimed at the automatic detection of small-scale impact craters utilizing lunar digital elevation models. In our work, we investigate the transfer-learning performances of one detector and conduct experiments on transferability from the perspectives of the geographic or topographic differences, which shows the knowledge transfer from source domain to target domain works well. Moreover, we calculate some quantitative metrics to describe the complexity of terrains and further find that the selected representative samples provide more valuable source of information for the generalization of one detector. For evaluative purposes, both qualitative and quantitative, each detector is comprehensively trained and then utilized for the detection of impact craters, drawing from the integrated digital elevation model of the Lunar Reconnaissance Orbiter (LRO) and Kaguya that extends over latitudes of ± 60° and the complete longitudinal spectrum, as well as its detection outcomes are benchmarked with the pre-existing crater catalog LU1319373. Experimental results that the topographic knowledge-aware detection outperforms traditional detection, with average differences of approximately 5 % in mAP and approximately 4 % in F1-score. The benefits of topographic knowledge-aware progressive detector training solution primarily derive from discrepancies in visual characteristics, heterogeneous lunar surfaces around the impact craters for generalization purposes. Our findings would be significantly applied to the discovery of scientific insights in both existing and new planetary datasets through the use of machine learning

The complete mitochondrial genome of an endangered mangrove plant: Scyphiphora hydrophyllacea

The complete mitochondrial genome of an endangered mangrove plant: Scyphiphora hydrophyllacea was analyzed in this paper, which is the first for the genus within the family Rubiaceae. The mitogenome sequence is 354,155 bp in length containing 3 ribosomal RNA genes, 16 transfer RNA genes, and 37 protein-coding genes. Gene ccmFc, ccmFn, rps3, rps13, rps10, rpl12, nad3 and cox1 contain one intron, gene cox2 and atp9 contain three introns and gene nad1, nad4 and nad7 contain four introns. Furthermore, Gene nad2 and nad5 have five introns. Gene nad1, nad2, nad5, nad7and Cox2 are trans-splicing genes. Phylogenetic analysis using the maximum likelihood method positioned S. hydrophyllacea closely with Asclepias syriaca in Gentianales

Comparative study of catalytic activity of N, S, N-S doping P25 on degradation of acid red B in visible light

In order to improve the photocatalytic properties of P25, using urea, thiourea and methionine as modifiers, the modified catalysts N-P25, S-P25 and N,S-P25 with visible light catalytic activity are prepared by grinding-calcination method, respectively. The properties of modified photocatalysts are characterized by scanning electron microscopy (SEM) and UV-Vis absorption spectroscopy, and the degradation property of acid red B in visible light by the modified photocatalysts is investigated. The results show that the wavelength ranges of light response of the N-P25, S-P25 and N,S-P25 modified photocatalysts expands, intensive absorption appears in both ultraviolet and visible light regions; the N,S-P25 prepared under the condition of calcination temperature of 700 ℃ and calcination time of 20 h has the highest catalytic activity on the degradation of acid red B, and the degradation reaction of acid red B in visible light conforms to the apparent first order reaction kinetics. The study proves that the modified P25 catalyst can improve the photocatalytic degradation of acid red B under visible light conditions, and enriches the research ideas of photocatalytic degradation of dye wastewater in visible light