In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.
Lithium-sulfur batteries have been regarded as promising candidates for energy storage because of their high energy density and low cost. It is a main challenge to develop long-term cycling stability battery. Here, a catalytic strategy is presented to accelerate reversible transformation of sulfur and its discharge products in lithium-sulfur batteries. This is achieved with single-atomic iron active sites in porous nitrogen-doped carbon, prepared by polymerizing and carbonizing diphenylamine in the presence of iron phthalocyanine and a hard template. The Fe-PNC/S composite electrode exhibited a high discharge capacity (427 mAh g) at a 0.1 C rate after 300 cycles with the Columbic efficiency of above 95.6%. Besides, the electrode delivers much higher capacity of 557.4 mAh g at 0.5 C over 300 cycles. Importantly, the Fe-PCN/S has a smaller phase nucleation overpotential of polysulfides than nitrogen-doped carbon alone for the formation of nanoscale of LiS as revealed by ex situ SEM, which enhance lithium-ion diffusion in LiS, and therefore a high rate performance and remarkable cycle life of Li-sulfur batteries were achieved. Our strategy paves a new way for polysulfide conversion with atomic iron catalysis to exploit high-performance lithium-sulfur batteries.
Herein, we synthesized
a Fe, Ni dual-metal embedded in porous nitrogen-doped
carbon material to endow higher turnover frequency (TOF), lower H2O2 yield, and thus superior durability than for the single-atom catalyst for oxygen reduction
in acid media. Quantitative X-ray absorption near edge structure (XANES)
fitting and density functional theory (DFT) calculation were implemented
to explore the active sites in the catalysts. The results suggest
FeNi-N6 with type I (each metal atom coordinated with four
nitrogen atoms) instead of type II configuration (each metal atom
coordinated with three nitrogen atoms) dominates the catalytic activity
of the noble-metal free catalyst (NMFC). Further, theoretical calculation
reveals that the oxygen reduction reaction (ORR) activity trend of
different moieties was FeNi-N6 (type I) > FeNi-N6 (type II) > Fe–N4 > Fe2–N6. Our research represents an important step
for developing
dual-metal doping NMFC for proton exchange membrane fuel cells (PEMFCs)
by revealing its new structural configuration and correlation with
catalytic activity.
The development of Li‐S batteries is greatly hindered by the polysulfide shuttling and sluggish sulfur redox kinetics, leading to low utilization of active materials and rapid capacity decay. Herein, a freestanding multifunctional interlayer, prepared by layer‐by‐layer assembling of the single‐atom cobalt‐anchored nitrogen‐doped carbon nanosheets (NC@SA‐Co) and dual network of carbon nanotube‐cellulose nanofiber (CNT‐CNF) hybrid, is proposed to effectively enhance the polysulfide immobilization and sulfur redox kinetics. The conductive CNT network acts as the physical barrier to confine the polysulfide diffusion and to facilitate the reuse of polysulfides. The oxygen‐group‐terminated CNF network allows the hopping of Li+ ion and suppresses the polysulfide crossover due to the strong electrostatic repulsion. Moreover, it is demonstrated that the 2D NC@SA‐Co with numerous well‐defined single sites of Co–N4 can effectively serve as an electrocatalyst to boost the reversible reaction of polysulfides. As a result, the assembled Li‐S batteries with the multifunctional interlayer deliver a high reversible specific capacity of 1160 mAh g−1 at 0.1 C and an ultralow capacity decay of 0.058% per cycle over 700 cycles. Even with a high sulfur loading of 7.2 mg cm−2, a high areal capacity of 8.3 mAh cm−2 can be achieved.
The optical force acting on a chiral particle is qualitatively different from that acting on an achiral particle due to chirality-dependent forces which couple mechanical linear momentum with optical spin angular momentum. We show that such chirality-induced coupling can serve as a mechanism to realize optical pulling forces that can be predicted analytically and are also observed in full wave simulations for chiral structures.
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