Coral-like and binder-free carbon nanowires for potassium dual-ion batteries with superior rate capability and long-term cycling life

Owing to the advantages of high operating voltage,environmental benignity,and low cost,potassium-based dual-ion batteries(KDIBs)have been considered as a potential candidate for large-scale energy storage.However,KDIBs generally suffer from poor cycling performance and unsatisfied capacity,and inactive components of conductive agents,binders,and current collector further lower their overall capacity.Herein,we prepare coral-like carbon nanowres(CCNWs)doped with nitrogen as a binder-free anode material for K^(+)-ion storage,in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability,to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process.As a result,the CCNW anode possesses a hybrid K^(+)-storage mechanism of diffusive behavior and capacitive adsorption,and stably delivers a high capacity of 276 mAh g^(-1)at 50 mA g^(-1),good rate capability up to 2 A g^(-1),and long-term cycling stability with 93%capacity retention after 2000 cycles at 1 A g^(-1).Further,assembling this CCNW anode with an environmentally benign expanded graphite(EG)cathode yields a proof-of-concept KDIB,which shows a high specific capacity of 134.4 mAh g^(-1)at 100 mA g^(-1),excellent rate capability of 106.5 mAh g^(-1)at 1 A g^(-1),and long-term cycling stability over 1000 cycles with negligible capacity loss.This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.

Atomic Pt anchored on hierarchically porous monolithic carbon nanowires as high-performance catalyst for liquid hydrogenation

Monolithic catalysts play a crucial role in various catalytic applications,e.g.,chemical synthesis,energy conversion,and environmental treatment,but their catalytic efficiency is often limited by the restricted mass transfer and insufficient exposure of active sites.Herein,we present a dual-templating strategy to fabricate atomic Pt dispersed on monolithic N-doped mesoporous carbon nanowires(Pt_(1)/NMCW)with abundant super-/macropores,which,as monolithic catalyst,exhibits high catalytic performance in hydrogenation of 4-nitrophenol(4-NP).During synthesis,triblock copolymer(Pluronic F127)is employed as a primary soft template to generate the mesoporous structured carbon nanowires to improve the accessibility of Pt single sites;KCl crystallite is used as a secondary hard template to create the super-/macropores,which are beneficial for enhancing the mass transfer efficiency.Thanks to the dual-templating strategy that creates the monolithic carbon nanowires with hierarchically porous structure,the obtained Pt_(1)/NMCW shows highly enhanced catalytic activity in 4-NP hydrogenation,outperforming its analogue synthesized without using KCl as template and being comparable to the nano-powder catalyst(i.e.,atomic Pt loaded on the Ndoped carbon nanospheres,Pt_(1)/NCS).

Porous NiCo_2O_4 nanowires supported on carbon cloth for flexible asymmetric supercapacitor with high energy density

Recently, binary metal oxides have been considerably researched for energy storage since it can provide higher electrical conductivity and electrochemical activity than single components. Besides, rational arrays structure design can effectively enhance the utilization of active material. In this article, we synthesis a porous NiCo_2O_4 nanowires arrays, which were intimate contact with flexible carbon cloth（CC）by a facile hydrothermal reaction and calcination treatment. The rational array structures of NiCo_2O_4 facilitate the diffusion of electrolyte and effectively increase the utilization of active material. The asobtained NiCo_2O_4@CC electrode exhibits a high capacitance of 1183 mF cm^（-2） and an outstanding capacitance retention of 90.4% after 3000 cycles. Furthermore, a flexible asymmetric supercapacitor（ASC）using NiCo_2O_4@CC as positive electrode and activated carbon cloth（ACC） as negative electrode was fabricated, which delivers a large capacitance of 750 mF cm^（-2）（12.5 F cm^（-3））, a high energy density of 0.24 mWh cm^（-2）（3.91 mWh cm^（-3））, as well as excellent cycle stability under different bending states.These remarkable results suggest that as-assembled NiCo_2O_4@CC//ACC ASC is a promising candidate in flexible energy storage applications.

Structural,electronic,and optical properties of hexagonal and triangular SiC NWs with different diameters

Silicon carbide（SiC） is a wideband gap semiconductor with great application prospects,and the SiC nanomaterials have attracted more and more attention because of their unique photoelectric properties.According to the first-principles calculations,we investigate the effects of diameter on the electronic and optical properties of triangular SiC NWs（T-NWs）and hexagonal SiC NWs（H-NWs）.The results show that the structure of H-NWs is more stable than T-NWs,and the conduction band bottom of H-NWs is more and more deviated from the valence band top,while the conduction band bottom of T-NWs is closer to the valence band top.What is more,H-NWs and T-NWs have anisotropic optical properties.The result may be helpful in developing the photoelectric materials.

Nb_2O_5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)

Niobium oxide nanowire-deposited carbon fiber（CF） samples were prepared using a hydrothermal method with amorphous Nb2O5·nH2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction（XRD）, energy-dispersive spectroscopy（EDS）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（SAED）, UV–visible spectroscopy（UV–vis）, N2 adsorption–desorption, Fourier transform infrared spectroscopy（FT-IR）, and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr（VI） was determined.Parameters such as pH value and initial Cr（VI） concentration could influence the Cr（VI） removal efficiency or adsorption capacity of the Nb2O5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14 hr. The maximal Cr（VI） adsorption capacity of the Nb2O5 nanowire/CF sample was 115 mg/g. This Nb2O5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr（Ⅵ） under UV-light irradiation： the Cr（VI） removal efficiency reached 99.9% after UV-light irradiation for 1 hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr（VI） adsorption capacity and photocatalytic performance was related to its high surface area,abundant surface hydroxyl groups, and good UV-light absorption ability.

Composition-Dependent Mechanical and Thermal Transport Properties of Carbon/Silicon Core/Shell Nanowires

Molecular dynamics(MD) simulations are performed to study the composition-dependent elastic modulus and thermal conductivity for carbon/silicon core/shell nanowires(NWs).For each concerned carbon/silicon core/shell NW with a specified diameter,it is found that elastic modulus is reduced with a linear dependence on cross-sectional area ratio.The fact matches well with the results of theoretical model.Analysis based on the cross-sectional stress distribution indicates that the core region of core/shell NW is capable of functioning as a mechanical support.On the other hand,thermal conductivity also relies on the cross-sectional area ratio of amorphous silicon shell.The core/shell interface plays a considerable influence on the thermal transport property. The decreasing rate of thermal conductivity is gradually decreased as the composition of amorphous silicon shell increases.In addition,by calculating the phonon density of state,we demonstrate that the reduction in thermal conductivity of the core/shell NW stems from the increase of the low frequency modes and the depression of high-frequency nonpropagating diffusion modes.These results provide an effective way to modify the properties of core/shell NWs for related application.

Regeneration of photovoltaic industry silicon waste toward high-performance lithium-ion battery anode

The diamond-wire sawing silicon waste(DWSSW)from the photovoltaic industry has been widely considered as a low-cost raw material for lithium-ion battery silicon-based electrode,but the effect mechanism of impurities presents in DWSSW on lithium storage performance is still not well understood;meanwhile,it is urgent to develop a strategy for changing DWSSW particles into high-performance electrode materials.In this work,the occurrence state of impurities presents in DWSSW was carefully analyzed using in situ Ar ion etching technology Then,the novel Si@C@SiO_(x)@PAl-NDC composite was designed through in situ encapsulation strategy.The obtained Si@C@SiO_(x)@PAl-NDC electrode shows a high first capacity of 2343.4 mAh·g^(-1)with an initial Coulombic efficiency(ICE)of 84.4%under current density of 1.0 A·g^(-1),and can deliver an impressive capacity of 984.9 mAh·g^(-1)after 200 cycles.Combined numerical simulation modeling calculations,the increase in proportion of Si^(4+)/Si^(0)and Si^(3+)/Si^(0)valence states in SiO_(x)layer leads to a decrease in von Mises stress,which ultimately improves the cycling structural stability.Meanwhile,the porous 2D-3D aluminum/nitrogen(Al/N)co-doped carbon layer and nanowires on SiO_(x)layer can provide abundant active sites for lithium storage due to its developed hierarchical pores structure,which facilitates ion transport What is more,the performance of Si@C@SiO_(x)@PAl-NDC//LiFePO_(4)full cell shows its great potential in practical application.

Self-supported ternary Co0.5Mn0.5P/carbon cloth （CC） as a high-performance hydrogen evolution electrocatalyst

Scalable production of earth-abundant, easy-to-prepare, and cost-effective electrocatalysts for the hydrogen evolution reaction （HER） is essential for sustainable energy-based systems. Herein, we systematically studied the electrocatalytic HER performance of a self-supported ternary Co0.5Mn0.5P/carbon cloth （CC） nanomaterial prepared using a hydrothermal reaction and phosphorizafion process. Electrochemical tests demonstrated that the ternary Co0.5Mn0.5P/CC nanomaterial could be a highly active electrocatalyst in acidic media, with overpotentials of only 41 and 89 mV, affording current densities of 10 and 100 mA.cm-2, respectively, and a Tafel slope of 41.7 mV.dec-1. Furthermore, the electrocatalyst exhibited superior stability, with 3,000 cycles of cyclic voltammetry from -0.2 to 0.2 V at a scan rate of 100 mV.s-1 and 40 h of static polarization at a fixed overpotential of large-scale hydrogen production. 83 mV, indicating its potential for

将Cu_(2)S超细纳米粒子均匀植入碳纳米线以实现高效钾离子电池负极

由于其高容量和丰富的资源,过渡金属硫化物(TMS)已被证明是钾离子电池具有吸引力的负极材料之一.然而,TMS通常受到导电性差和体积膨胀大的限制,可能导致结构不稳定和电池循环性能差.本工作通过将超小Cu_(2)S纳米粒子植入碳纳米线(Cu_(2)S@C NWs),显著减轻了纳米粒子聚集和有害的结构退化.与传统的Cu_(2)S颗粒相比,每根纳米线的体积变化都得到了有效调节,这极大地改善了形态完整性,从而显著提高了循环寿命.正如预期的那样,Cu_(2)S@C NW负极可提供391.1 mA h g^(-1)的大可逆容量,在5 A g^(-1)时具有118.1 mA h g^(-1)的出色倍率性能,以及在2 A g^(-1)下经过500次循环后77.2%的高容量保持率.此外,当Cu_(2)S@C NW负极与KVP04F/CNTs正极组装形成钾离子全电池时,在50 mA g^(-1)下循环100次后显示出110.8 mA h g^(-1)的良好放电容量.这种纳米颗粒阻聚策略拓宽了纳米工程的视野,以释放嵌脱钾引起的应力,并促进钾离子电池高效负极的进一步发展.