Carbon nanotubes (CNTs) filled with iron sulfide nanoparticles (NPs) are prepared by inserting sulfur and ferrocene into the hollow core of CNTs followed by heat treatment. It is found that pyrrhotite-11T iron sulfide (Fe-S) NPs with an average size of ≈15 nm are encapsulated in the tubular cavity of the CNTs (Fe-S@CNTs), and each particle is a single crystal. When used as the anode material of lithium-ion batteries, the Fe-S@CNT material exhibits excellent electrochemical lithium storage performance in terms of high reversible capacity, good cyclic stability, and desirable rate capability. In situ transmission electron microscopy studies show that the CNTs not only play an essential role in accommodating the volume expansion of the Fe-S NPs but also provide a fast transport path for Li ions. The results demonstrate that CNTs act as a unique nanocontainer and reactor that permit the loading and formation of electrochemically active materials with desirable electrochemical lithium storage performance. CNTs with their superior structural stability and Li-ion transfer kinetics are responsible for the improved rate capability and cycling performance of Fe-S NPs in CNTs.

Wan Jing Yu;畅 刘;Lili Zhang;Peng Xiang Hou;锋 李;Bao Zhang;会明 成

Advanced Science

2016-10-1

In order to achieve high energy and power densities, we developed a high-voltage asymmetric electrochemical capacitor (EC) based on graphene as negative electrode and a MnO₂ nanowire/graphene composite (MGC) as positive electrode in a neutral aqueous Na₂SO₄ solution as electrolyte. MGC was prepared by solution-phase assembly of graphene sheets and α-MnO₂ nanowires. Such aqueous electrolyte-based asymmetric ECs can be cycled reversibly in the high-voltage region of 0-2.0 V and exhibit a superior energy density of 30.4 Wh kg^-1, which is much higher than those of symmetric ECs based on graphene//graphene (2.8 Wh kg^-1) and MGC//MGC (5.2 Wh kg^-1). Moreover, they present a high power density (5000 W kg^-1 at 7.0 Wh kg^-1) and acceptable cycling performance of ∼79% retention after 1000 cycles. These findings open up the possibility of graphene-based composites for applications in safe aqueous electrolyte-based high-voltage asymmetric ECs with high energy and power densities.

Zhong Shuai Wu;文才 任;Da Wei Wang;锋 李;Bilu Liu;会明 成

ACS Nano

2010-10-26

Single-walled carbon nanotubes (SWNTs) were mechanically milled with lithium borohydride (LiBH₄) and examined with respect to its effect on the reversible dehydrogenation reactions of LiBH₄. It was found that as-prepared SWNTs possess pronounced promoting effects on the dehydrogenation/rehydrogenation reactions of LiBH₄, thus rendering the composite material reversible hydrogen storage at markedly reduced operation temperature and pressure conditions. For the LiBH₄-30 wt % SWNTs composite milled for 1 h, 11.4 wt % hydrogen can be discharged within 50 min at 450 °C; over 6.0 wt % hydrogen can be recharged at 400 °C under an initial hydrogen pressure of 10 MPa. The systematic property/phase/structure studies of the LiBH₄-SWNTs composite and related materials suggest that the observed property enhancement should be understood as combined effects of the metal nanoparticles or their borides, and carbon nanotubes. Additionally, the mechanism underlying the characteristic capacity loss in the dehydrogenation/rehydrogenation cycles of LiBH₄ was also discussed.

Zhan Zhao Fang;Xiang Dong Kang;Ping Wang;会明 成

Journal of Physical Chemistry C

2008-10-30

Photoelectrochemical (PEC) water splitting is a very promising process to produce hydrogen as a clean energy carrier. To achieve 10% solar to hydrogen (STH) conversion efficiency required for practical applications, the current central task in PEC water splitting is the development of efficient photoelectrodes, particularly photoanodes for water oxidation, used in PEC cells. Tantalum (oxy)nitrides with bandgaps ranging from 2.5 to 1.9 eV, corresponding to theoretical STH efficiencies varying from 9.3% to 20.9%, are considered a class of attractive light adsorbers for use in photoanodes for PEC water oxidation and have attracted much recent research attention. In this review, the recent development of tantalum (oxy)nitride photoanodes is summarized. Special interest is focused on the synthesis methods of tantalum (oxy)nitride films and important approaches for improving PEC conversion efficiency and stability of these films as photoanodes. The future trends of tantalum (oxy)nitride based photoanodes are also discussed.

Chao Zhen;Runze Chen;Lianzhou Wang;Gang Liu;会明 成

Journal of Materials Chemistry A

2016

At present, there is ongoing search for a potential non-polluting renewable substitute with higher hydrogen storage capacity so as to obtain an appropriate weight-energy ratio. This article discusses the efforts aimed at the mass production of pure vapor-grown carbon nanofibers (VGCNFs).

Yue Ying Fan;Bin Liao;Min Liu;Yong Liang Wei;Man Qi Lu;会明 成

Carbon

1999

Herein, we systematically investigate the structural, electronic, and vibrational properties of ammonia borane (NH₃BH₃, AB) and lithium amidoborane (LiNH₂BH₃ LAB) through both density functional calculations and experiments. AB and LAB samples are generated and their vibrational spectra are obtained by using Fourier transformed infrared spectroscopy (FTIR). The measured vibrational spectra are in good agreement with the calculated ones. Our calculations show that the Li-related vibration modes are primarily found in the low-frequency region (< 1000 cm^-1), and that the intermolecular interactions significantly influence the vibrational spectra. Electronic structure calculations provide insights into the differences between the binding natures of AB and LAB and their influence on the vibrational properties of these compounds.

Seung Mi Lee;Xiang Dong Kang;Ping Wang;会明 成;Young Hee Lee

ChemPhysChem

2009-8-3

A combined structure/property investigation is performed to understand the catalytic effect of TiF₃ additive on the absorption /desorption reactions of MgH₂. It was found that both TiH₂ and MgF₂ phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH₂-TiF₃ system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF₃ and its analog TiCl₃, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.

Lai Peng Ma;Ping Wang;Xiang Dong Kang;会明 成

Journal of Materials Research

2007-7

Upon mechanically milling with as-prepared single-walled carbon nanotubes, the dehydriding/rehydriding kinetics of LiBH₄ can be markedly improved, thus rendering the system partial reversibility at reduced temperature/pressure conditions. Based on the property/phase analysis results, as well as the results of the designed experiments, the observed catalytic enhancement was understood as combined effects of metallic Ni, Co, Fe or their borides nanoparticles, and carbon nanotubes.

Z. Z. Fang;X. D. Kang;H. B. Dai;M. J. Zhang;P. Wang;会明 成

Scripta Materialia

2008-5

An effective, nondestructive, and universal strategy to homogeneously modify freestanding carbon nanotube (CNT) films with various active species is essential to achieve functional electrodes for flexible electrochemical energy storage, which is challenging and has attracted considerable research interest. In this work, a generalizable concept, to utilize silicon oxide as the intermediate to uniformly decorate various metal sulfide nanostructures throughout CNT films is reported. Taking nickel sulfide nanosheet/CNT (NS/CNT) films, in which the NS nanosheets are homogeneously attached on the intact few-walled CNTs, as an example, the sheet-like NS provides sufficient active sites for redox reactions and the CNT network acts as an efficient electron highway, maintaining the structural integrity of the composite and also buffering volume changes. These merits enable NS/CNT films to meet the requirements of versatile energy storage applications. When used for supercapacitors, a high specific capacitance (2699.7 F g ⁻¹ /10 A g ⁻¹ ), outstanding rate performance at extremely high rates (1527 F g ⁻¹ /250 A g ⁻¹ ), remarkable cycling stability, and excellent flexibility can be achieved, among the best performance so far. Moreover, it also delivers excellent performance in the storage of Li and Na ions, meaning it is also potentially suitable for Li/Na ion batteries.

Pengyi Lu;Xiaowei Wang;Lei Wen;Xiaotong Jiang;Wenlei Guo;Lei Wang;Xiao Yan;Feng Hou;Ji Liang;会明 成;Shi Xue Dou

Small

2019-4-12

Multi-walled carbon nanotubes (MWCNTs) enhanced high-density polyethylene (HDPE) composites were prepared and their thermophysical properties were measured. The thermal diffusivity of the composites increases with the increase in the amount of MWCNTs. A thermal diffusivity of more than three times that of pure HDPE was obtained for 38vol.∈% MWCNTs/HDPE composites. An equation based on an effective medium approach model was used to discuss the thermal diffusivity enhancement of MWCNTs/HDPE composites as a function of the volume fraction of MWCNTs. The results from this analysis can be a predictive guideline for further improvements in the thermal transport properties of MWCNTs/HDPE composites. Moreover, the intrinsic longitudinal thermal conductivity k _z of an individual MWCNT was deduced from the measured results on the MWCNTs/HDPE composites.

F. Wu;X. He;Y. Zeng;会明 成

Applied Physics A: Materials Science and Processing

2006-10