Heterogeneous isomorphism hollow SiGe nanospheres with porous carbon reinforcing for superior electrochemical lithium storage

Silicon is emerging as a promising next-generation lithium-ion battery anode because of its high theoretical capacity and low cost. However, the poor cyclability and inferior rate performance hinder its largescale applications. Here, hollow silicon/germanium(H-SiGe) nanospheres with a binary-active component and heterogeneous structure combined with porous carbon(pC) reinforcing are synthesized as lithium-ion battery anodes. Experimental studies demonstrate that the H-SiGe/pC anodes possess tiny...     

Ordered porous thin films in electrochemical analysis

Recently, the field of highly-ordered mesoporous and macroporous thin films coated onto solid electrode surfaces has begun to receive attention due to their great interest for electrochemical analysis. This review highlights the features of both electricallyconducting and non-conducting organized layers, which are applicable to designing electrochemical sensors, and the methods applied to construct these novel nanomaterials.We emphasize methods based on use of self-assembled colloidal templates (e.g., surfactants or nanoparticles), around which the materials of interest are formed. We then describe their basic electrochemical behavior and discuss their possible use as electrochemical sensors and biosensors, mostly in the particular case of structured metallic layers, functionalized mesoporous silica films, and some other continuous three-dimensional ordered porous structures.     

The study of controlling pore size on electrospun carbon nanofibers for hydrogen adsorption

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared by using electrospinning method and heat treatment to get the media for hydrogen adsorption storage. Potassium hydroxide and zinc chloride activations were conducted to increase specific surface area and pore volume of CNFs. To investigate the relation between pore structure and the capacity of hydrogen adsorption, textural properties of activated CNFs were studied with micropore size distribution, specific surface area, and total pore volume by using BET (Brunauer-Emmett-Teller) surface analyzer apparatus and the capacity of hydrogen adsorption was evaluated by PCT (pressure-composition-temperature) hydrogen adsorption analyzer apparatus with volumetric method. The surface morphology of activated CNFs was observed by SEM (scanning electron microscope) images to investigate the surface change through activation. Even though specific surface area and total pore volume were important factors for increasing the capacity of hydrogen adsorption, the pore volume which has pore width (0.6-0.7 nm) was a much more effective factor than specific surface area and pore volume in PAN-based electrospun activated CNFs.     

Nitrogen-doped porous carbon plates derived from fallen camellia flower for electrochemical energy storage

Journal of Solid State Electrochemistry - Nitrogen-doped porous carbon plates have been prepared by simple and cost-effective pyrolysis carbonization of an easily available biomass-fallen camellia...     

Amine-functionalised SBA-15 of tailored pore size for heavy metal adsorption

This study examines the synthesis of SBA-15 with tailored pore sizes through controlled thermal treatment for the adsorption of Pb and Cd ions. The aim is to produce a material that can adsorb heavy metals at both high and low concentrations. The materials were characterised by means of N(2) physisorption, powder X-ray diffraction (PXRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), microanalysis and transmission electron microscopy (TEM). The surface areas ranged from 410 to 871 m(2)g(-1), and pore diameter was increased from 5.9 to 10.8 nm. This method allows for maximum adsorption of metal ions at very low concentrations. Metal ion adsorption was determined using an Atomic Absorption Spectrophotometer. The effects of pH were found to play a major role in the precipitation and, therefore, adsorption of metal ions. This method proved to be efficient at adsorbing large quantities of both metals (39 and 41 mg g(-1) for Pb and Cd, respectively).     

Intensified electrochemical hydrogen storage capacity of multi-walled carbon nanotubes supported with Ni nanoparticles

The electrochemical hydrogen storage properties of Ni-supported multi-walled carbon nanotube (Ni/MWCNT) electrodes were investigated using charge/discharge (C&D) and cyclic voltammetry (CV) techniques. Nickel NPs were deposited on the MWCNT surface, which was first chemically oxidized by H₂SO₄ and HNO₃ (3:1, v/v). Hydrogen storage was carried out by using the Ni/MWCNT electrode as the working electrode in the electrochemical cell. A set of various current densities were applied to the cell to produce (C&D) cycles, and it became optimum corresponding to 1.5 mA current. According to the electrochemical test results, the highest electrochemical discharge capacity of 1625 mAh g^?1 was obtained for the electrode with ratio of 4:1 (MWCNTs to Ni) in the initial cycle, which corresponded to 6.07 wt% H₂. The storage capacity was increased and reached to 4909 mAh g^?1 (18.34 wt% H₂) after 20 cycles, and the electrode maintained the specific capacity as cycling continued. Thus, the Ni/MWCNT electrode displays an excellent cycle stability and a high capacity reversibility. CV measurements also showed that the electrochemical adsorption and desorption amount of hydrogen was increased by Ni loading onto the CNTs and indicated that the electrochemical hydrogen adsorption of the electrode has an activated period.     

The controllable synthesis of porous MoN nanorods/carbon for highly efficient electrochemical hydrogen evolution

MoN is a promising material for electrochemical hydrogen evolution due to its cheap price and excellent catalytic activity sites, but the low conductivity prevents further improvement of its catalytic performance. In this work, porous MoN nanorods have been fabricated with an efficient and facile precursor method. XRD, Raman and TEM showed MoN nanorods with diameters of about 100 nm. With a simple mechanical mixing method, MoN/conductive carbon black (CB) composites with different weight ratios have been fabricated. The composite possessed two merits, that is, the more catalytic active site in MoN nanorods due to the porous structure, and fast electron transfer due to the CB. So, it has been used as a hydrogen evolution material. With the proper weight ratio, the composite exhibited brilliant catalytic activity and durability in acidic media. It possesses an overpotential of 162 mV to approach 10 mA cm^?2, a small Tefel slope of 54 mV dec^?1 and maintains the good electrocatalytic activity for at least 10 h. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the electrocatalyst possessed a high catalytic active area and fast electron transfer. These results can compare with many other recently reported nitride catalysts. Our work possibly provides a new avenue for the preparation of a MoN-based catalyst for highly efficient electrochemical hydrogen evolution.     

Controllable synthesis of hierarchical nanostructured hollow core/mesopore shell carbon for electrochemical hydrogen storage

Hierarchical nanostructured hollow core/mesopore shell carbon (HN-HCMSC) represents an innovative concept in electrochemical hydrogen storage. This work deals with physical characteristics and electrochemical hydrogen storage behavior of the HN-HCMSCs, produced by a replica technique using solid core/mesopore shell (SCMS) silica as template. HN-HCMSCs with various core sizes and/or shell thicknesses have been fabricated through the independent control of the core sizes and/or shell thicknesses of the SCMS silica templates. The superb structural characteristics of the HN-HCMSCs including large specific surface area and micropore volume, and particularly well-developed three-dimensionally interconnected hierarchical nanostructure (hollow macroporous core in combination with meso-/microporous shell), provide them with great potential for electrochemical hydrogen storage. A discharge capacity up to 586 mAh/g, corresponding to 2.17 wt % hydrogen uptake, has been demonstrated in 6 M KOH for the HN-HCMSC with a core size of 180 nm and a shell thickness of 40 nm at a discharge rate of 25 mA/g. Furthermore, the HN-HCMSC also possesses excellent cycling capacity retainability and rate capability.     

Nitrogen-doped porous carbon derived from bimetallic zeolitic imidazolate frameworks for electrochemical Li+/Na+ storage

Journal of Solid State Electrochemistry - Porous carbon is regarded as one of the most promising anode candidates for Li-ion battery and Na-ion battery, and the specific porous structure and...     

Architected porous metals in electrochemical energy storage

Porous metallic structures are regularly used in electrochemical energy storage (EES) devices as supports, current collectors, or active electrode materials. Bulk metal porosification, dealloying, welding, or chemical synthesis routes involving crystal growth or self-assembly, for example, can sometimes provide limited control of porous length scale, ordering, periodicity, reproducibility, porosity, and surface area. Additive manufacturing has shown the potential to revolutionize the fabrication of architected metals, allowing complex geometries not usually possible by traditional methods, by enabling complete design freedom of a porous metal based on the required physical or chemical property to be exploited. We discuss properties of porous metal structures in EES devices and provide some opinions on how architected metals may alleviate issues with electrochemically active porous metal current collectors, and provide opportunities for optimum design based on electrochemical characteristics required by batteries, supercapacitors or other electrochemical devices.     

金属改性与碳包覆的多孔硅微球复合材料的制备及其电化学储锂性能

以工业级SiAl合金微球为前驱物,采用多步刻蚀-热处理策略,制备了金属(Sb-Sn)改性与碳包覆的多孔硅微球复合材料(pSi/Sb-Sn@C)。pSi/Sb-Sn@C具有以 Sb-Sn改性的多孔硅微球(pSi/Sb-Sn)为核、碳包覆层为壳的三维结构。碳外壳可以提高多孔硅微球的电子导电性和机械稳定性,有利于获得稳定的固体电解质界面(SEI)膜;而三维多孔核可以促进锂离子的扩散,增加嵌/脱锂活性位,缓冲嵌锂过程中的体积膨胀。此外,活性金属(Sb-Sn)的引入能够提高复合材料的导电性,并可以贡献一定的储锂容量。由于其特殊的组成和独特的微观结构,pSi/Sb-Sn@C复合材料在1.0 A·g^-1电流密度下充放电300次后的可逆容量为1 247.4 mAh·g^-1,显示了良好的高速率储锂性能和优异的电化学嵌/脱锂循环稳定性。     

Zeolite-templated carbon materials for high-pressure hydrogen storage

Zeolite-templated carbon (ZTC) materials were synthesized, characterized, and evaluated as potential hydrogen storage materials between 77 and 298 K up to 30 MPa. Successful synthesis of high template fidelity ZTCs was confirmed by X-ray diffraction and nitrogen adsorption at 77 K; BET surface areas up to ~3600 m(2) g(-1) were achieved. Equilibrium hydrogen adsorption capacity in ZTCs is higher than all other materials studied, including superactivated carbon MSC-30. The ZTCs showed a maximum in Gibbs surface excess uptake of 28.6 mmol g(-1) (5.5 wt %) at 77 K, with hydrogen uptake capacity at 300 K linearly proportional to BET surface area: 2.3 mmol g(-1) (0.46 wt %) uptake per 1000 m(2) g(-1) at 30 MPa. This is the same trend as for other carbonaceous materials, implying that the nature of high-pressure adsorption in ZTCs is not unique despite their narrow microporosity and significantly lower skeletal densities. Isoexcess enthalpies of adsorption are calculated between 77 and 298 K and found to be 6.5-6.6 kJ mol(-1) in the Henry's law limit.     

Effects of fluorination modification on pore size controlled electrospun activated carbon fibers for high capacity methane storage

Electrospun carbon fibers were prepared as a methane storage medium. Chemical activation was carried out using potassium carbonate to develop the pore structure, which can provide sites for the uptake of methane, and then fluorination surface modification was conducted to enhance the capacity of storage. Chemical activation provided a highly microporous structure, which is beneficial for methane storage, with a high specific surface area greater than 2500 m²/g. The pore size distribution showed that the prepared samples have pore sizes in the range of 0.7–1.6 nm. The effect of fluorination surface modification was also investigated. The functional groups, which were confirmed by XPS analysis, played an important role in guiding methane gas into the carbon silt pores via the attractive force felt by the electrons in the methane molecules due to the high electronegativity of fluorine. Eventually, the methane uptake increased up to 18.1 wt.% by the synergetic effects of the highly developed micropore structure and the guiding of methane to carbon pores by fluorine.     

Interactive effects of pore size control and carbonization temperatures on supercapacitive behaviors of porous carbon/carbon nanotube composites

Porous carbon-based electrodes were prepared by carbonization with poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composites to further increase the specific capacitance for supercapacitors. The specific capacitance, pore size distribution, and surface area of the PVDF/CNT composites were measured, and the effect of the carbonization temperatures was examined. The electrochemical properties were examined by cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge performance using a two-electrode system in TEABF(4) (tetraethylammonium tetrafluoroborate)/acetonitrile as a non-aqueous electrolyte. The highest specific capacitance of ～101 Fg(-1) was obtained for the samples carbonized at 600 °C. The pore size of the samples could be controlled to below 7 nm through the carbonization process. This suggests that micropores make a significant contribution to the specific capacitance due to improved charge transfer between the pores of the electrode materials and the electrolyte.     

Electrochemical storage of hydrogen in nanocarbon materials: electrochemical characterization of carbon black matrices

In this work, various types of carbon black are electrochemically characterized to study their possible use in the electrochemical evaluation of fullerene materials as hydrogen storage candidates. The cyclic voltammetry and chronopotentiometry studies were performed in alkaline media, 6 M KOH, with carbon paste electrodes. Differences in the electrodes' electrochemical response and their correlation with the various surface chemistries, morphology and doping species of carbon blacks suggest a stronger dependency on the presence of doping agents (foreign metals) and on the surface structure than on the carbon black surface area. The study allows the selection of appropriate carbon black materials to be used as matrixes in future fullerene composite studies. Electronic Publication     

Mg1.8La0.2Ni-xNi nanocomposites for electrochemical hydrogen storage

Mg1.8La0.2Ni hydrogen storage alloy was ball-milled with Ni powder, leading to the formation of a nanocrystalline and amorphous microstructure with particle sizes less than 50 nm in diameter. Each sample was examined by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This structure was beneficial for the reduction of electrochemical impedance, as well as significant improvement of its discharge capacity, cycle life, and rate capability for electrochemical hydrogen storage in an alkaline solution. When the molar ratio (x) of Ni over Mg1.8La0.2Ni was equal to 2, the dehydriding capacity reached 2.55 wt % from electrochemical pressure-temperature isotherms (P-C-T). It was in good agreement with its initial discharge capacity, 716 mA*h/[g of (Mg1.8La0.2Ni)], observed from the electrochemical charge and discharge process. After 50 cycles, its discharge capacity still reached 381 mA*h/[g of (Mg1.8La0.2Ni)]. Further results showed that this composite had a promising high rate capability. At the current density of 1200 mA/g its discharge capacity reached 48% of its initial capacity.     

Enhanced electrochemical performance of straw-based porous carbon fibers for supercapacitor

The efficient utilization of natural biomass as renewable raw materials is of importance. We herein prepared porous carbon fibers (PCFs) by activation of the extracted cellulose microfibers from the agriculture byproduct of corn straw. Different from the porous carbons (PCs) by directly activating straw, the obtained PCFs had typical one-dimensional morphology with high surface area (2013 m² g^?1) and large pore volume (1.27 cm³ g^?1). The influence of the ZnCl₂/cellulose mass ratio on the electrochemical performance was studied, and the optimized PCF(1:1) possessed a much higher specific capacitance than the PC(1:1) sample, which was attributed to the improved specific surface area as well as the fiber-like morphology where it had short ion diffusion route and small interfacial resistance in comparison to PCs. PCFs have a high specific capacitance of 230 F g^?1 at 0.5 A g^?1, and 183 F g^?1 was retained at 20 A g^?1 (79.6%), revealing an excellent rate capability. The assembled symmetrical supercapacitor exhibited a wide potential window of 1.8 V, small electrochemical impedance, and superior cycle performance. Moreover, a high energy density of 16.0 Wh kg^?1 was obtained at a power density of 450.4 W kg^?1, which was preserved of 6.9 Wh kg^?1 at a high power density of 14,194.3 W kg^?1.