Controlled growth of Co9S8 nanoparticle-embedded carbon nanosheets/carbon nanofibers toward high-performance sodium storage.

Transition metal sulfides (TMSs) are considered as promising anodes for sodium-ion batteries (SIBs) due to their high theoretical capacity and low cost. However, TMSs suffer from massive volume expansion, slow sodium-ion diffusion kinetics, and poor electrical conductivity, which severely restrict their practical application. Herein, we design self-supporting Co9S8 nanoparticles embedded carbon nanosheets/carbon nanofibers (Co9S8@CNSs/CNFs) as anode materials for SIBs. The electrospun carbon nanofibers (CNFs) provide continuous conductive networks to accelerate the ion and electron diffusion/transport kinetics, while MOFs-derived carbon nanosheets (CNSs) buffer the volume variation of Co9S8, consequently improving the cycle stability. Benefitting from the unique design and pseudocapacitive features, Co9S8@CNSs/CNFs deliver a stable capacity of 516 mAh g-1 at 200 mA g-1 and a reversible capacity of 313 mAh g-1 after 1500 cycles at 2 A g-1. Note that, it also displays excellent sodium storage performance when assembled into a full cell. The rational design and excellent electrochemical properties endow Co9S8@CNSs/CNFs with the potential stepping into commercial SIBs.

Bowl-shaped hollow carbon wrapped in graphene grown in situ by chemical vapor deposition as an advanced anode material for sodium-ion batteries.

Sodium-ion batteries (SIBs) are expected to be ideal alternatives to lithium-ion batteries (LIBs) in the future due to their abundant and low-cost resource advantages. A key challenge in SIBs is the development of anodes capable of insertion/extraction of sodium ions (Na+) with large radii. Here, hollow bowl-shaped porous carbon materials are uniformly modified with vertically grown graphene (denoted as HBC/VGSs) demonstrating a large specific surface area and three-dimensional structure, which are employed as a viable high-performance anode for SIBs. HBC/VGSs anodes are highly effective at storing sodium because of their structural features. As a result, the HBC/VGSs electrodes provide a high reversible capacity of 409 mAh g-1 after 100 cycles at 0.1 A g-1, as well as outstanding rate capability (301.6 mAh g-1 at 5 A g-1). Moreover, it also shows extraordinary cycling stability (230.3 mAh g-1 after 2500 cycles at a high current density of 5 A g-1) that is significantly better than the pristine hollow bowl-shaped porous carbon (HBC). Cyclic Voltammetry (CV) and Galvanostatic Intermittent Titration Technique (GITT) were used to analyze the pseudocapacitance and sodium storage kinetics. It was found that high electrical conductivity and large surface area can improve Na+ adsorption and diffusion, enhance the electronic conductivity, and deliver superior capacity and rate. The results, taken as a whole, provide new insight into the creation of long-lasting carbon anodes that deliver optimal performance in SIBs.

Flexible cobalt nanoparticles/carbon nanofibers with macroporous structures toward superior electromagnetic wave absorption.

The increasing electromagnetic (EM) pollution that has seriously threatened human health and electronic devices urgently required high-performance absorbents toward attenuating EM wave (EMW). The combination of microstructure modulation and appropriate components regulation has proven to be a feasible strategy for improving the EMW absorption performance of absorbents. In this work, well-designed one-dimensional carbon nanofibers with macroporous structures and uniformly magnetic metal nanoparticles modification were prepared by the hard-template assisted electrospinning method followed by carbonization and template-elimination processes. The strong interfacial polarization loss and multireflection strengthened by the hollow structures and the magnetic loss induced by the introduced cobalt nanoparticles evidently enhanced the impedance matching level of the macroporous carbon nanofibers/cobalt nanoparticles (MCF/Co). As a result, MCF/Co composite offers broad absorption bandwidth (6.24 GHz) and strong electromagnetic wave absorption performance (-40.1 dB) at a thickness of 3.0 mm. This work inspires the rational one-dimensional macroporous carbon nanofibers design for new-generation EMW materials and provides an important research basis for the porous flexible EMW absorption materials.

Insight into the Role of Copper in the Transformation of a [Ag25(2,5-DMBT)16(DPPF)3]+ Nanocluster: Doping or Oxidation.

Structural transformation in nanoclusters is important not only in obtaining functional nanoclusters controllably but also in understanding their structural evolution. This study investigated the role of Cu2+ ions in structural transformation. It was revealed that Cu2+ exhibits two different functions, doping and oxidation, in determining the final products. Starting with a new silver nanocluster, [Ag25(2,5-DMBT)16(DPPF)3]+ (Ag25), a doping process would occur when no more than 0.5 equiv of Cu2+ was added, resulting in the formation of [Ag25-xCux(2,5-DMBT)16(DPPF)3]+ (Ag25-xCux). When 1 equiv of Cu2+ was introduced to Ag25, a structural transformation process would occur instead, forming [Ag22-xCux(2,5-DMBT)12(DPPF)4Cl4]2+ (Ag22-xCux). Considering the similar Cu doping amounts in Ag25-xCux and Ag22-xCux, an oxidation process induced by Cu2+ in the solution can account for this transformation process, which was further demonstrated by the addition of other oxidant substitutions. On the other hand, the role of other valence states of copper in the transformation of the Ag25 cluster was explored. It was found that copper powder can hardly change Ag25 and Cu+ can only proceed the doping process, both of which are different from the role of Cu2+. Overall, this work explores the role of copper in the transformation of the Ag25 cluster in detail, including its concentrations and valence states.

H-bond-induced luminescence enhancement in a Pt1Ag30 nanocluster and its application in methanol detection.

Hydrogen bonding is an important type of interaction for constructing nanocluster assemblies. In this study, the role of hydrogen bonding interactions in regulating the fluorescence properties of nanoclusters is investigated. A [Pt1Ag30(SAdm)14(Bdpm)4Cl5]3+ (Pt1Ag30 for short) nanocluster containing hydrogen-accepting ligands is synthesized and its structure is determined. By introducing N-containing ligands into nanoclusters, hydrogen bonding interactions between nanoclusters and polar solvents can be established, which can result in a 35-fold enhancement in the fluorescence intensity (in MeOH vs. in DCM). A series of experiments are designed to demonstrate hydrogen bonding interactions between N atoms in the Pt1Ag30 cluster and H in the polar solvent and the results show that fluorescence enhancement is derived from the proton-coupled/uncoupled electron transfer between hydrogen bonds. Furthermore, this Pt1Ag30 is used for the naked-eye detection of MeOH on indicator paper.

In Situ Fabrication of Branched TiO2 /C Nanofibers as Binder-Free and Free-Standing Anodes for High-Performance Sodium-Ion Batteries.

Herein, 1D free-standing and binder-free hierarchically branched TiO2 /C nanofibers (denoted as BT/C NFs) based on an in situ fabrication method as an anode for sodium-ion batteries are reported. The in situ fabrication endows this material with large surface area and strong structural stability, providing this material with abundant active sites and smooth channels for fast ion transportation. As a result, BT/C NFs with the character of free-standing membranes are directly used as binder-free anode for sodium-ion batteries, delivering a capacity of 284 mA h g-1 at a current density of 200 mA g-1 after 1000 cycles. Even at a high current density of 2000 mA g-1 , the reversible capacity can still achieve as high as 204 mA h g-1 . By means of kinetic analysis, it is demonstrated that the remarkable surface pseudocapacitive behavior is also a major factor to achieve excellent performance. The rationally designed structure coupled with the inherent pseudocapacitive behavior gives this material potential for sodium-ion batteries.

Carbon-Based Alloy-Type Composite Anode Materials toward Sodium-Ion Batteries.

In the scenario of renewable clean energy gradually replacing fossil energy, grid-scale energy storage systems are urgently necessary, where Na-ion batteries (SIBs) could supply crucial support, due to abundant Na raw materials and a similar electrochemical mechanism to Li-ion batteries. The limited energy density is one of the major challenges hindering the commercialization of SIBs. Alloy-type anodes with high theoretical capacities provide good opportunities to address this issue. However, these anodes suffer from the large volume expansion and inferior conductivity, which induce rapid capacity fading, poor rate properties, and safety issues. Carbon-based alloy-type composites (CAC) have been extensively applied in the effective construction of anodes that improved electrochemical performance, as the carbon component could alleviate the volume change and increase the conductivity. Here, state-of-the-art CAC anode materials applied in SIBs are summarized, including their design principle, characterization, and electrochemical performance. The corresponding alloying mechanism along with its advantages and disadvantages is briefly presented. The crucial roles and working mechanism of the carbon matrix in CAC anodes are discussed in depth. Lastly, the existing challenges and the perspectives are proposed. Such an understanding critically paves the way for tailoring and designing suitable alloy-type anodes toward practical applications.