Hydrophilic bi-functional B-doped g-C_(3)N_(4) hierarchical architecture for excellent photocatalytic H_(2)O_(2) production and photoelectrochemical water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has attracted great interest in photocatalysis and photoelectrocatalysis.However,their poor hydrophilicity poses a great challenge for their applications in aqueous environment.Here,we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C_(3)N_(4)nanoplatelets.Such hierarchical B-doped g-C_(3)N_(4)material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium,leading to an excellent photocatalytic H_(2)O_(2)production rate of 4240.3μM g^(-1)h^(-1),2.84,2.64 and 2.13 times higher than that of the bulk g-C_(3)N_(4),g-C_(3)N_(4)nanoplatelets and bulk B doped g-C_(3)N_(4),respectively.Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 m A cm^(-2)at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting.This work makes a fundamental improvement towards large-scale exploitation of highly active,hydrophilic and stable metal-free g-C_(3)N_(4)photocatalysts for various practical applications.

Interwoven scaffolded porous titanium oxide nanocubes/carbon nanotubes framework for high-performance sodium-ion battery

Supercapacitor-like Na-ion batteries have attracted much attention due to the high energy density of batteries and power density of capacitors.Titanium dioxide(TiO_(2)),is a promising anode material.Its performance is however seriously hindered by its low electrical conductivity and the sluggish diffusion of sodium ions(Na^(+))in the TiO_(2)matrix.Herein,this work combines porous TiO_(2)nanocubes with carbon nanotubes(CNTs)to enhance the electrical conductivity and accelerate Na^(+)diffusivity for Na-ion batteries(NIBs).In this composite,an interwoven scaffolded TiO_(2)/CNTs framework is formed to provide abundant channels and shorter diffusion pathways for electrons and ions.The in-situ X-ray diffraction and cyclic voltammetry confirm the low strain and superior transport kinetics in Na^(+)intercalation/extraction processes.In addition,the chemically bonded TiO_(2)/CNTs hybrid provides a more feasible channel for Na^(+)insertion/extraction with a much lower energy barrier.Consequently,the TiO_(2)/CNTs composite exhibits excellent electrochemical performance with a capacity of 223.4 m Ah g^(-1)at 1 C and a capacity of 142.8 m Ah g^(-1)at 10 C(3.35 A g^(-1)).The work here reveals that the combination of active materials with CNTs can largely improve the utilization efficiency and enhance their sodium storage.

Improvement in potassium ion batteries electrodes: Recent developments and efficient approaches

Demand for efficient and continuous application for high-grid energy storage systems involves the study towards novel battery technologies. Hence, considering the vast naturally available resources of potassium all over the world and its encouraging intercalation chemistries, it has recently enticed attention in electrochemical energy storage industry in the form of potassium ion batteries (PIBs). The major factor in this K+ based battery, is to develop efficient approaches to manufacture electrode substance to intercalate its big size potassium ions with considerable voltage, kinetics, charge/discharge capacity, capacity retention, cost, etc. This study contributes in the recent developments of anode and cathode materials for PIBs, including several electrode materials in regards to synthesis, structure, electrochemical performance, and K-storage mechanisms. Finally, the review contributes to provide helpful sources for the increasing number of scientists working in this industry regarding its critical issues and challenges and also to indicate the future direction of electrode materials in PIBs.

Bioinspired urchin-like murray carbon nanostructure with protection shell for advanced lithium-sulfur batteries

Commercial application of lithium-sulfur(Li-S) batteries is hindered by the insulating nature of sulfur and the dissolution of polysulfides. Here, a bioinspired 3D urchin-like N-doped Murray's carbon nanostructure(N-MCN) with interconnected micro-meso-macroporous structure and a polydopamine protection shell has been designed as an effective sulfur host for high-performance Li-S batteries. The advanced 3D hierarchically porous framework with the characteristics of the generalized Murray's law largely improves electrolyte diffusion, facilitates electrons/ions transfer and provides strong chemisorption for active species, leading to the synergistic structural and chemical confinement of polysulfides. As a result,the obtained P@S/N-MCN electrode with high areal sulfur loading demonstrates high capacity at high current densities after long cycles. This work reveals that following the generalized Murray's law is feasible to design high-performance sulfur cathode materials for potentially practical Li-S battery applications.

Solution processed MoS2-PVA composite for subbandgap mode-locking of a wideband tunable ultrafast Er：fiber laser

We fabricate a free-standing few-layer molybdenum disulfide （MoS2）-polymer composite by liquid phase exfoliation of chemically pristine MoS2 crystals and use this to demonstrate a wideband tunable, ultrafast mode-locked fiber laser. Stable, picosecond pulses, tunable from 1,535 nm to 1,565 nm, are generated, corresponding to photon energies below the MoS2 material bandgap. These results contribute to the growing body of work studying the nonlinear optical properties of transition metal dichalcogenides that present new opportunities for ultrafast photonic applications.

Few-layer MoS2 saturable absorbers for short-pulse laser technology: current status and future perspectives [Invited]

Few-layer molybdenum disulfide（MoS2） is emerging as a promising quasi-two-dimensional material for photonics and optoelectronics, further extending the library of suitable layered nanomaterials with exceptional optical properties for use in saturable absorber devices that enable short-pulse generation in laser systems. In this work, we catalog and review the nonlinear optical properties of few-layer MoS2, summarize recent progress in processing and integration into saturable absorber devices, and comment on the current status and future perspectives of MoS2-based pulsed lasers.

Phase boundary engineering of metal-organic-framework-derived carbonaceous nickel selenides for sodium-ion batteries

Nano Research volume 13,pages2289–2298(2020)Cite this article 347 Accesses 1 Altmetric Metrics details Abstract Sodium-ion batteries(SIBs)are promising power sources due to the low cost and abundance of battery-grade sodium resources,while practical SIBs suffer from intrinsically sluggish diffusion kinetics and severe volume changes of electrode materials.Metal-organic framework(MOFs)derived carbonaceous metal compound offer promising applications in electrode materials due to their tailorable composition,nanostructure,chemical and physical properties.Here,we fabricated hierarchical MOF-derived carbonaceous nickel selenides with bi-phase composition for enhanced sodium storage capability.As MOF formation time increases,the pyrolyzed and selenized products gradually transform from a single-phase Ni3Se4 into bi-phase NiSex then single-phase NiSe2,with concomitant morphological evolution from solid spheres into hierarchical urchin-like yolk-shell structures.As SIBs anodes,bi-phase NiSex@C/CNT-10h(10 h of hydrothermal synthesis time)exhibits a high specific capacity of 387.1 mAh/g at 0.1 A/g,long cycling stability of 306.3 mAh/g at a moderately high current density of 1 A/g after 2,000 cycles.Computational simulation further proves the lattice mismatch at the phase boundary facilitates more interstitial space for sodium storage.Our understanding of the phase boundary engineering of transformed MOFs and their morphological evolution is conducive to fabricate novel composites/hybrids for applications in batteries,catalysis,sensors,and environmental remediation.

Core processing neuron-enabled circuit motifs for neuromorphic computing

Based on brain-inspired computing frameworks,neuromorphic systems implement large-scale neural networks in hardware.Although rapid advances have been made in the development of artificial neurons and synapses in recent years,further research is beyond these individual components and focuses on neuronal circuit motifs with specialized excitatory-inhibitory(E-I)connectivity patterns.In this study,we demonstrate a core processor that can be used to construct commonly used neuronal circuits.The neuron,featuring an ultracompact physical configuration,integrates a volatile threshold switch with a gate-modulated two-dimensional(2D)MoS_(2) field-effect channel to process complex E-I spatiotemporal spiking signals.Consequently,basic neuronal circuits are constructed for biorealistic neuromorphic computing.For practical applications,an algorithm-hardware co-design is implemented in a gatecontrolled spiking neural network with substantial performance improvement in human speech separation.

Bioinspired Noncyclic Transfer Pathway Electron Donors for Unprecedented Hydrogen Production

Electron donors are widely exploited in visible-light photocatalytic hydrogen production.As a typical electron donor pair and often the first choice for hydrogen production,the sodium sulfide-sodium sulfite pair has been extensively used.However,the resultant thiosulfate ions consume the photogenerated electrons to form an undesirable pseudocyclic electron transfer pathway during the photocatalytic process,strongly limiting the solar energy conversion efficiency.Here,we report novel and bioinspired electron donor pairs offering a noncyclic electron transfer pathway that provides more electrons without the consumption of the photogenerated electrons.Compared to the state-of-the-art electron donor pair Na_(2)S-Na_(2)SO_(3),these novel Na_(2)S-NaH_(2)PO_(2)and Na_(2)S-NaNO_(2)electron donor pairs enable an unprecedented enhancement of up to 370%and 140%for average photocatalytic H_(2)production over commercial CdS nanoparticles,and they are versatile for a large series of photocatalysts for visible-light water splitting.The discovery of these novel electron donor pairs can lead to a revolution in photocatalysis and is of great significance for industrial visible-light-driven H_(2)production.

Enhanced composite thermal conductivity by percolated networks of in-situ confined-grown carbon nanotubes

Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry,nanomaterials like carbon nanotubes(CNTs)have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional(3D)conduction network with low loading and desired isotropic or anisotropic(specific preferred heat conduction)performances.Herein,we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances.First,to in-situ construct an isotropic percolated conduction network,with spherical cores as support materials,we developed a confined-growth technique for CNT-core sea urchin(CNTSU)materials.With 21.0 wt.%CNTSU loading,the thermal conductivity of composites reached 1.43±0.13 W/(m·K).Secondly,with aligned hexagonal boron nitride(hBN)as an anisotropic support,we constructed CNT-hBN aligned networks by in-situ CNT growth,which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers.With~8.5 wt.%loading,the composites possess thermal conductivity up to 0.86±0.14 W/(m·K),374%of that for neat matrix.Due to the uniformity of CNTs in hBN network,the synergistic thermal enhancement from one-dimensional(1D)+two-dimensional(2D)hybrid materials becomes more distinct.Based on the detailed experimental evidence,the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed,particularly compared with the traditional direct-mixing method.This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required.