•The synthesis of B, N co-doped graphene-like carbon (BNC) by a two-step method.•Ball-milling process creates abundant active sites and introduces the N atoms.•The introducing of B can fix the N ...contents with the B–N bond.•As-prepared BNC exhibits an excellent performance of 254 F/g at 0.25 A/g.•At high current densities, the BNC obtained high retentions of initial capacitance.
Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.
Developing efficient and cheap electromagnetic wave absorption (EWA) materials is highly desirable in modern information society. Herein, based on the abundant and low-cost petroleum asphalt, ...hierarchical porous carbon nanosheets (PCNs) have been rationally fabricated via one-step carbonization process by using water-removable NaCl templates. The NaCl can provide crystal planes for the growth of graphitized carbon layers, and promote the formation of interconnected porous architectures. The porous nanosheets structures realize the multiple reflections and scattering in the void space. The presence of dipole polarization and interfacial polarization in PCNs facilitates the dielectric loss. Remarkably, the EWA performance of optimized PCNs with a low filler content of 20 wt% reaches a strong reflection loss of −53.7 dB and a broad absorption bandwidth of 5.3 GHz at a thin thickness of 1.8 mm. This encouraging performance considerably outperforms most of reported dielectric materials, which also meets the demands of thin, light weight, strong and broad features for new-type EWA materials. Therefore, our strategy may open up new avenues for development of promising EWA materials and realizing the high value-added utilization of petroleum asphalt by considering the facile process and low production cost.
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•Hierarchical porous carbon nanosheets derived from petroleum asphalt are prepared via a NaCl-templated method.•The absorbers exhibit remarkable microwave absorption performance with a thickness of only 1.8 mm.•This unfolds a new avenue for high value-added utilizing of petroleum asphalt.
A lightweight microwave absorber constructed by hierarchically porous carbon with firmly embedded magnetic nanoparticles achieves an excellent microwave absorption performance with an ultralow filler ...loading of 5 wt.%, which outperforms the current magnetic-dielectric hybrids.
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•A feasible strategy is proposed to construct hierarchical porous magnetic carbon with tightly embedded Ni species.•Well-dispered Ni nanoparticles produce strong magnetic coupling networks to enhance magnetic loss of dielectric carbon.•The absorbers exhibit an excellent microwave absorption performance with an ultralow filler loading of 5 wt.%.•This work unfolds a new avenue for the development of high-performance and lightweight microwave absorbers.
Developing microwave absorption (MA) materials with satisfied comprehensive performance is a great challenge for tackling severe electromagnetic pollution. In particular, the magnetic component/carbon hybrids absorbers always suffer from high filler loading. Herein, we propose a feasible strategy to construct hierarchical porous carbon with tightly embedded Ni nanoparticles (Ni@NPC). These highly dispersed Ni nanoparticles produce strong magnetic coupling networks to enhance magnetic loss abilities. Moreover, the interconnected hierarchical dielectric carbon network affords favorable dipolar/interfacial polarization, conduction loss, multiple reflection and scattering. Impressively, with an ultralow filler loading of 5 wt.%, the resultant Ni@NPC/paraffin composite achieves an excellent MA performance with a minimum reflection loss of as high as -72.4 dB and a broad absorption bandwidth of 5.0 GHz. This capability outperforms most current magnetic-dielectric hybrids counterparts. Furthermore, the MA capacity can be easily tuned with adjustments in thickness, content and type of magnetic material. Thus, this work opens up new avenues for the development of high-performance and lightweight MA materials.
Boron and nitrogen co-doped graphene-like carbon (BNG) is a metal-free catalyst that has been synthesized by combining ball-milling with thermal treatment. Firstly, the ...edge-selectively-functionalized graphene nanoplatelets (EFGnPs) were prepared by ball milling of the pristine graphite, which can facilitate boron incorporation. BNG catalysts with a high content of boron and nitrogen can then be obtained by pyrolysis of a mixture of EFGnPs and boric acid. We found that the reduction of nitroarenes can be catalyzed using a low BNG loading and a small amount of N
2
H
4
in ethanol to form aminoarenes in high yields. The type of boron species in the BNG catalyst has an important effect on the reduction reaction. Furthermore, the catalyst containing the most B/N shows the highest catalytic activity during the reduction of nitroarenes, indicating that the doped B/N within the BNG is a key active site in impelling this reaction. Moreover, the BNG catalyst can be used six times, and no dehalogenation phenomenon occurs during the reduction process for halogen-substituted nitroarenes in contrast to the case when conventional metal catalysts are used.
The scalable production of large quantities of defect-free graphene nanosheets (GNs) with low cost and excellent properties is essential for practical applications. Despite the highly intense ...research of this area, the mass production of graphene nanosheets with high solubility remains a key challenge. In the present work, we propose a scalable exfoliation process for hydrophilic GNs by ball-milling-assisted supercritical CO2 exfoliation in the presence of poly(vinylpyrrolidone) via the synergetic effect of chemical peeling and mechanical shear forces. The exfoliation difficulty has been reduced due to the intercalation effects of supercritical CO2 molecules. With the ball-milling assistance, the modifier has been introduced onto the edge or/and surface of the GNs. The process results in hydrophilic GNs with little damage to the in-plane structure. The GNs can be dispersed in various solvents with a concentration of up to 0.854 mg/mL (water) and remain stable for several months.
Merging structural variations (SVs) at the population level presents a significant challenge, yet it is essential for conducting comprehensive genotypic analyses, especially in the era of ...pangenomics. Here, we introduce PanPop, a tool that utilizes an advanced sequence-aware SV merging algorithm to efficiently merge SVs of various types. We demonstrate that PanPop can merge and optimize the majority of multiallelic SVs into informative biallelic variants. We show its superior precision and lower rates of missing data compared to alternative software solutions. Our approach not only enables the filtering of SVs by leveraging multiple SV callers for enhanced accuracy but also facilitates the accurate merging of large-scale population SVs. These capabilities of PanPop will help to accelerate future SV-related studies.
Trombe wall system is an effective passive solar heating, and phase change material can enhance its heat storage performance significantly. However, excessive heat loss during winter nighttime has ...been observed. Setting the curtain in air cavity can improve heat preservation of winter nighttime. The three-dimensional model of a phase change material-Trombe wall (TW-PCM) is established with FLUENT, and the influences of phase change temperature (PCT) and location of curtain/aluminum foil on thermal performance of the TW-PCM are obtained. It indicates that the total heat output reduces and the heating time extends for the TW-PCM, and the proportion of glass heat loss is over 50 %. The heat efficiency of the TW-PCM in the nighttime are significantly improved for TW-PCM with the curtain (CTW-PCM). For a TW with an air cavity width of 0.15 m, when the thickness of circulation air cavity exceeds 0.07 m (turbulent flow), heat efficiency is higher. The aluminum foil should attach to the external surface of the curtain.
The safety of on-orbit satellites is threatened by space debris with large residual angular velocity and the space debris removal is becoming more challenging than before. This paper explores the ...non-contact despinning and traction problem of high-speed rotating targets and proposes an eddy current brake and traction technology for space targets without any propellant consumption. The principle of the conventional eddy current brake is analyzed in this article and the concept of eddy current brake and traction without propellant is put forward for the first time. Secondly, according to the key technical requirements, a brand-new structure of a satellite generating artificial magnetic field is designed accordingly. Then the control mechanism of eddy current brake and traction without propellant is analyzed qualitatively by simplifying the model and conditions. Then, the magnetic pulse control method is proposed and analyzed quantitatively. Finally, the feasibility of the technology is verified by the numerical simulation method. According to the simulation results, the eddy current brake and traction technology based on magnetic pulses can make the angular speed of target decrease linearly without propellant during the process. This technology has huge advantages compared with conventional eddy current brake technology in terms of efficiency and reduced propellant consumption.
Electrocatalytic CO2‐to‐formate conversion is considered an economically viable process. In general, Zn‐based nanomaterials are well‐known to be highly efficient electrocatalysts for the conversion ...of CO2 to CO, but seldom do they exhibit excellent selectivity toward formate. In this article, we demonstrate that a heterointerface catalyst ZnO/ZnSnO3 with nanosheet morphology shows enhanced selectivity with a maximum Faradaic efficiency (FE) of 86% at −0.9 V versus reversible hydrogen electrode and larger current density for the conversion of CO2 to formate than pristine ZnO and ZnSnO3. In particular, the FEs of the C1 products (CO + HCOO−) exceed 98% over the potential window. The experimental measurements combined with theoretical calculations revealed that the ZnO in ZnO/ZnSnO3 heterojunction delivers the valence electron depletion and accordingly optimizes Zn d‐band center, which results in moderate Zn–O hybridization of HCOO* and weakened Zn–C hybridization of competing COOH*, thus greatly boosting the HCOOH generation. Our study highlights the importance of charge redistribution in catalysts on the selectivity of electrochemical CO2 reduction.
A heterointerface ZnO/ZnSnO3 electrocatalyst with enriched oxygen vacancies is designed for electrochemical reduction of CO2 to formate, in which the electronic structure of surface ZnO is regulated and accordingly optimized Zn d‐band center, resulting in moderate Zn–O hybridization of HCOO* and weakened Zn–C hybridization of competing COOH*, thus greatly boosting the HCOOH generation.
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