Search

Vehicular lithium-ion batteries (LIBs) may suffer from minor damage or defects owing to external mechanical abuse, such as deformation and scratches, during cycling. This study uses non-destructive testing methods to analyze the effects of minor mechanical deformation on the lifetime and performance of commercial 21700 lIBs. Firstly, incremental capacity analysis (ICA) is performed to quantify the charge/discharge performance and cycle aging behavior of LIBs under different deformations. Secondly, X-ray computed tomography (XCT) technology is utilized to qualitatively analyze the internal structure variations of LIBs caused by minor mechanical deformation. Results show that with an increase in mechanical deformation, the internal resistances of LIBs increase, charging curves move to high voltage areas, and peak points of the incremental capacity (IC) curves decrease and move to high voltage areas. Cyclic charge/discharge of LIBs with different deformations show that with an increase in cycles, the capacity and state-of-health (SOH) of mechanically deformed LIBs decrease significantly due to the changes in the internal structure of batteries. Furthermore, the tomographic images of LIBs demonstrate that the increased internal gaps within the electrodes result in the increase of internal resistance, and the mechanism for capacity loss of batteries in the cyclic is revealed. [ABSTRACT FROM AUTHOR]

In this study, nanotwinned copper (nt-Cu) foils were fabricated using a rotary electroplating system. Their microstructures (orientation, grain size, and twin spacing) and correlated tensile properties were substantially tuned by manipulating the electroplating current density. The nt-Cu foils were further heat-treated at 150 °C for 1 h and tensile-tested to characterize their thermal stability. We found that the mechanical properties of the nt-Cu foils are directly associated with the electroplating current density. The ultimate tensile strength (UTS) increases with increasing in the current density, reaching the maximum values at 25 ASD. The great enhancement can be attributed to the decrease in twin spacing and grain size. We also discovered that the UTS and ductility remain approximately intact under a high temperature, indicating the excellent thermal stability of such nt-Cu foils. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of morphology on the analytical performance of α-Fe2O3 nanostructures-based electrochemical sensors toward chloramphenicol (CAP) antibiotic using three designed morphologies including α-Fe2O3 nano-tube (α-Fe2O3-T), α-Fe2O3 nano-rice (α-Fe2O3-R), and α-Fe2O3 nano-plate (α-Fe2O3-P). Among these morphologies, α-Fe2O3-T displayed an outstanding electrochemical activity owing to the unique hollow structure and large specific surface area. However, due to the small pores size, α-Fe2O3-T showed the high steric hindrance (SD) effect towards an antibiotic with complex molecular structure, as CAP, leading to a significant decrease of their CAP electrochemical sensing performance. The CAP analytical performance of α-Fe2O3-R was highest in investigated morphologies owing to a high density of exposed Fe3+ as well as less SD effect towards CAP molecules. Under optimized conditions, α-Fe2O3-R-based CAP electrochemical sensor reached an electrochemical sensitivity of 0.92 µA µM-1 cm-2 with a LOD of 0.11 µM in the detection range from 2.5-50 µM. In addition, all these α-Fe2O3 nanostructures-based electrochemical sensors had excellent stability and high anti-interference ability for CAP analysis in a complex food matrix, as shrimp sample. This study provides valuable insights into the morphology-dependent sensing properties of α-Fe2O3 nanostructures towards antibiotics, which is helpful to the design of novel α-Fe2O3-based electrochemical nanosensors. [ABSTRACT FROM AUTHOR]

A passive air-breathing formate fuel cell with PdAuAg alloy nanoparticles supported on the carbon nanotube (CNT) pasted on nickel foam (NF) as anode is reported in this work. With optimization, a maximum power density of 16 mW cm-2 with PdAuAg/CNT on NF as anode is achieved, which is 2.2 time of that achieved by using commercial Pd/C on NF (7.3 mW cm-2). Furthermore, the cell with PdAuAg/CNT on NF as anode can steadily discharge at 5 mA cm-2 for more than 28 h continuously. This is, to our knowledge, the best performance of passive air-breathing formate fuel cells reported so far and PdAuAg/CNT on NF as anode can be considered as the state-of-the-art for the passive air-breathing formate fuel cell. These results suggested that the PdAuAg/CNT catalyst probably provides an alternative avenue for developing the anode electrocatalysts for passive air-breathing formate fuel cell applications. [ABSTRACT FROM AUTHOR]

The effect of S-doping on the performance of Fe/N-C catalysts for ORR was studied. It was found that the abundant C-S-C bonds in the sulfur-doped catalysts enhanced the ORR activity greatly, while the existence of excessive C-SOX-C bonds was adverse to the kinetics of ORR. Also, the existence of Fe was able to increase the contents of both C-S-C bond and graphite N during the pyrolysis stage of preparation, thus generating more ORR active sites. The resulted effective configurations of S (C-S-C) and active N (both graphitic N and pyridinic N), and the combination of rich hierarchical porous structure with the encased Fe3C nanoparticles were responsible for the excellent performance of catalysts. Specifically, the E1/2 of the prepared FeNSC-10S catalyst reached 0.91 V in a 0.1 M KOH electrolyte solution, which was 20 mV positive shift to the E1/2 of the 20 wt.% Pt/C commercial catalyst. The electron transfer number was determined to be 3.85-3.91 over the potential range of 0.4-0.8 V, indicating that the ORR catalytic process proceeded in a reaction pathway with nearly 4e- transfer. The developed catalyst also demonstrated a longterm stability as well as a superior methanol tolerance in alkaline conditions. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoribbons, nanotubes, nanorods were fabricated in a reverse microemulsion system by adjusting the ratio of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) and FeCl3 aqueous solution. The morphologies and structures of nanostructured PEDOT were characterized by SEM, TEM, FTIR, XRD, and XPS. The PEDOT nanoribbons, nanotubes and nanorods can be obtained, when the volume ratio of FeCl3 aqueous solution to AOT hexane (Va/Vh) was between 2.0 × 10-2 and 3.0 × 10-2. As-obtained PEDOT nanotubes showed a high specific capacitance of 171.5 F g-1 at 0.4 A g-1, which was greater than the nanoribbons (134 F g-1) and nanorods (145.7 F g-1), respectively. Additionally, the PEDOT nanotubes exhibited excellent stability with a retention rate of 105% after 5000 cycles. This indicates that the as-prepared PEDOT nanotubes have potential applications in high capacity supercapacitors. [ABSTRACT FROM AUTHOR]

Parasitic gas evolution in lithium ion battery (LIB) cells especially occurs within the first charge cycle, but can also take place during long-term cycling and storage, thereby, negatively affecting the cell performance. Gas formation is influenced by various factors, such as the cell chemistry and operating conditions, thus, demanding fundamental studies in terms of interphase and gas formation (gas volume and composition) and electrolyte consumption. Gas analyses in terms of mass spectrometry of gaseous products are regularly performed, however, usually using custom-made cell designs with a high excess of electrolyte. Here, a gas sampling port (GSP) is incorporated in a commercial small-scale multilayer pouch cell in a simple post-production process and systematically evaluated as proof-of-principle approach towards effective electrolyte additive research under practically relevant conditions, i.e., when applying a limited amount of electrolyte per cell capacity. The GSP-based LIB pouch cell design allows the voltage-dependent identification and separation of formed gases, while a clear correlation between electrolyte reduction peaks, observed in differential capacity profiles, and the onset of gas evolution is demonstrated. In summary, the novel GSP-based pouch cell setup benefits from the possibility of multiple time-, cell voltage- or state-of-charge-dependent gas measurements, without significantly influencing the original cell performance. [ABSTRACT FROM AUTHOR]

Semiconductor heterostructure SrTiO3/CeO2 (STO/CeO2) membrane was used as the electrolyte material of low-temperature solid oxide fuel cells. This STO/CeO2 membrane demonstrated a high ionic conductivity of 0.24 S cm-1 under fuel cell conditions at 550°C, and also its fuel cell delivered a maximum power output of 745.6 mW cm-2 at the same temperature. Moreover, the high electronic conductivity of CeO2 is blocked by the STO/CeO2 semiconductor heterojunction, thus resulting in the open circuit voltage increasing from 0.90 to 1.09 V at 550°C. The semiconductor heterointerface is found to play an important role in inhibiting the electron transfer between CeO2 particles. Thus, this work makes it feasibility of using semiconductor materials as the electrolyte by constructing heterojunctions to suppress the electronic conductivity. [ABSTRACT FROM AUTHOR]

It is a universal quest to produce molecular hydrogen (H2) from sustainable green routes to diversify the heavy dependence of fossil fuels for energy consumption. Developing earth-abundant electrocatalysts for water electrolysis is a promising method to generate hydrogen via hydrogen evolution reaction (HER). In this work, we strategically promote electron transport and activate the basal planes of MoS2 via a thermal hybridization with vertically-aligned hierarchical nickel phosphide Ni5P4-Ni2P (denoted as MoS2/Ni5P4-Ni2P) for HER. The metallic-like Ni5P4-Ni2P foam promotes electron transportation into the MoS2 matrix by electron injection due to the difference of their Fermi levels. Moreover, MoS2 basal planes are activated by Ni5P4-Ni2P due to phosphorus doping effects, triggering additional actives sites and boosting the overall HER performances. Notably, the HER performance of MoS2/Ni5P4-Ni2P electrode only requires an overpotential of 96 mV to reach a geometric current density of -10 mA cm-2 with relatively low Tafel slope of 74 mV dec-1. The catalytic performances can last for at least 22 h at -10 mA cm-2 without discernible degradation, indicating the extraordinary long-term operation stability. This work provides insights into the synergistic effects of a hybridized catalyst, which may potentially serve as a next-generation electrocatalyst for efficient water splitting. [ABSTRACT FROM AUTHOR]

Transition-metal carbides (MXenes) are an emerging class of two-dimensional (2D) materials with promising electrochemical sensing performance due to their unique structural and electronic properties. To further improve its sensing performance, herein, the composite of Ti3C2Tx (MXene) and electrochemically reduced graphene oxide (MXene/ERGO) was proposed as electrode material for electrochemical detection of pesticide carbendazim (CBZ). The MXene/ERGO was synthesized by a facile and green electrochemical approach, where the mixture of MXene and graphene oxide (GO) was firstly dropped on the electrode surface, followed by electrochemical reduction of GO. The ERGO conductive networks tightly linked the separated layers of Ti3C2Tx and connected the separated Ti3C2Tx particles, which leading to enhanced electronic conductivity, improved the electrochemical reactivity of electrode materials and facilitated electron transfer between electrode and detection molecules. Consequently, the sensor based on MXene/ERGO exhibited a high sensitive detection of CBZ with a wide linear range of 2.0 nM~10.0 µMand a low limit of detection (LOD) of 0.67 nM. Moreover, the sensor showed good selectivity and reproducibility toward CBZ detection. The proposed sensor was successfully subjected to detect CBZ in cucumber and orange juice samples with acceptable results. [ABSTRACT FROM AUTHOR]

Poor capacity stability during long cycle and poor adhesion under high potential hinder the Lithium-manganese rich layered oxides cathode from applications, and necessary strategy for this is clearly needed. In this work, a novel aqueous binder (lithium poly (acrylic acid), Li-PAA) is introduced for stabilized cyclic performance of Li1.15Ni0.17Co0.11Mn0.57O2 materials. Contrasting with the commercial ones (polyvinylidene fluoride, PVDF), this binder is beneficial to enhance the connection between the electrode and current collector, which can improve cycle stability. In the meanwhile, optimization mechanisms are revealed via detailed measurements, which indicate the suppressed formation of spinel phase during cycling. As a result, the electrode with Li-PAA still delivers the specific capacity of 254.7 mAh g-1 with the retention of 90.77% after 200 cycles at 0.1C, higher than that of electrode with PVDF (223.6 mAh g-1,76.21%). The current subject study provides a conducive insight to develop an excellent binder based on Li-PAA for potential low-riced and environmentally friendly high energy density Li-ion batteries. [ABSTRACT FROM AUTHOR]

Silver-copper oxide brazes are commonly used to bond zirconia to stainless steel (SS) for Solid Oxide Fuel Cell (SOFC) and other high temperature joining applications. In fact, conventional Ag-CuO compositions (where Cu segregates to the surface, oxidizes, and reduces the silver wetting angle on zirconia from ~85 to ~40°) allow brazing to be performed in air. Unfortunately, the relatively high ~40° wetting angles of these reactive air brazes, and the ability of SOFC anode gases to reduce the CuO in them, produce pores during SOFC manufacturing and operation that reduce joint strength, impermeability, and longevity. Recently, Ag brazes utilizing transient porous nickel layers, instead of CuO additions, have been shown to produce high quality braze joints between SS and yttria stabilized zirconia (YSZ). Here, the microstructural and compositional evolution of SS|Ag-3CuO|YSZ and SS|Ag-Ni|YSZ braze joints exposed to air on one side and humidified 4%H2-96%N2 on the other side for either ~300 hours of ~750°C aging or ~300 25°C/min 35-830°C rapid thermal cycles are compared. While both brazes display considerable microstructural and compositional evolution, only the Ag-Ni brazes remain pore free and well bonded, indicating that Ag-Ni brazes may be more suitable for long term SOFC operation. [ABSTRACT FROM AUTHOR]

In this work, Ag nanoparticles (Ag NPs) decorated CoS nanoflowers (CoS NFs) were firstly used as bis-coreaction accelerator for signal amplification to establish an highly sensitive electrochemiluminescence (ECL) immunosensor for cardiac troponin T (cTnT) detection. Due to the synergistic catalysis between CoS NFs and Ag NPs, the decomposition rate of the co-reaction reagent H2O2 was largely improved, generating more ROS for signal amplification. Using the N-(4-aminobutyl)-N-ethylisoluminol (ABEI) as ECL luminophore, a new signal tag was acheived according to the assembly of ABEI functionalized Ag NPs (ABEI-Ag) on the CoS NFs via Ag-S bond, which integrated with the ECL luminophore and bis-co-reaction accelerator. In addition, to fabricate sensing interface, primary antibodies (Ab1) was immobilized on the glassy carbon electrode which decorated with Au nanoparticles (Au NPs), almost providing a zero background signal. As a result, this developed immunosensor for cTnT possessed a linear range from 0.1 fg mL-1 to 100 pg mL-1 and the limit of detection down to 0.03 fg mL-1 for ultrasensitive detection of cTnT, which was expected to be applicable to cTnT detection in clinic acute myocardial infarction. [ABSTRACT FROM AUTHOR]

Aluminum reactivity in cement-based matrices, generally used for conditioning low- and intermediate-level radioactive wastes, is a problem due to dihydrogen produced by the corrosion reaction which depends on the pH of the pore solution. Electrochemical impedance spectroscopy has been used to propose a mechanism for aluminum corrosion in cementitious matrices based on ordinary Portland cement (OPC, pH ≈ 13) or magnesium phosphate cement (MKP, pH ranging between 4 and 9) containing or not LiNO3 as a corrosion inhibitor. The fit of impedance diagrams recorded on aluminum electrode as a function of time has been realized using electrical parameters to model the cement and kinetic constants for the faradaic impedance. The so determined kinetic constants are used to calculate the corrosion current and the dihydrogen production as a function of time. Comparison of these results with experimental measurements of dihydrogen release obtained by gas chromatography shows a very good agreement except in the MKP matrix containing LiNO3. In the OPC matrix, dihydrogen production is between 500 and 1000 times higher than in the MKP matrix, which put in evidence the significant benefit in using MKP cements for aluminum encapsulation. [ABSTRACT FROM AUTHOR]

In this work, we proposed a novel ultrasonic transducer array based on an array of 50 × 50 piezoelectric micromachined ultrasonic transducers (pMUTs). The structure was specially designed for fingerprint imaging application. The pMUTs array were fabricated with isolated piezoelectric lead zirconate titanate (PZT) cells to reduce the crosstalk between adjacent units, and released by deepsilicon etching from the back side. The cell size and pitch of pMUTs were 50 μm and 100 μm, respectively. Layer-by-layer annealing method was used instead of one-time annealing during the fabrication of sol-gel based PZT film. The resonance frequency of the pMUT was about 24.82 MHz which agreed well with simulated 25.02 MHz. Besides, the effective electro-mechanical coupling coefficient (keff) and mechanical quality factor (Q factor) of the transducer were 0.1293 and 198, respectively. The equivalent circuit of the transducer was established and analyzed. The fitted admittance circle agreed well with the experimental result. This demonstration of pMUTs array has profound potential for large-scale, high-density, and high-frequency fingerprint imaging. [ABSTRACT FROM AUTHOR]

Spinel Li4Ti5O12 has been considered as a promising anode material to substitute graphite in lithium ion batteries (LIBs) for large scale electrical energy storage due to its high safety and long cycling stability. However, the drawback of its poor rate performance still hinders it from wide practical application. In this study, with the aim to solve this issue, we have designed a wrinkled graphene layer between the active spinel Li4Ti5O12 and aluminum current collectors by a blade coating method. This introduced wrinkled graphene layer provides larger contact area, lower contact resistance, stronger adhesion and better electrode stability of Li4Ti5O12 electrode. As a result, the rate performance of spinel Li4Ti5O12 has been significantly improved, without compromising its other properties. [ABSTRACT FROM AUTHOR]

Enormous work has been devoted to the vanadium redox flow battery (VRFB) in recent years; however, the electrochemical behavior of the vanadium redox couples in solutions has not been well understood. In the present work, the transition between the adjacent redox couples (V2+↔V3+↔V4+↔V5+) was extensively investigated on a typical electrode material (Vulcan XC72 carbon black) by the cyclic voltammetry (CV) in various potential windows. It was found that the two redox reactions, V3+/2+ and V5+/4+, could be seen as quasi-reversible electrochemical processes. With the simulation of the CV results, the standard rate constant was found to be (1.5 ± 0.4)*10-3 cm s-1 (V5+/4+) and (2.0 ± 0.4)*10-3 cm s-1 (V3+/2+), and the diffusion coefficient was determined to be (3.2 ± 0.5)*10-6 cm2 s-1 (V5+), (3.3 ± 0.5)*10-6 cm2 s-1 (V4+), (9.0 ± 1.3)*10-7 cm2 s-1 (V3+) and (9.0 ± 1.3)*10-7 cm2 s-1 (V2+), respectively. In comparison, V4+/3+ was rarely observed in the thermodynamic potential region, of which the anodic and cathodic waves overlapped with the other two redox couples. Also, the kinetic parameters were extracted by the Nicholson analysis for comparison. In terms of the electrochemical kinetics, Vulcan XC72 meets the requirement as the electrode material in VRFB, which yields promising electrochemical properties and is worth further investigating. The above findings shed lights on both the mechanism of redox reactions and the charging/discharging processes in the VRFB. [ABSTRACT FROM AUTHOR]

Highly ordered MoSe2 nanospheres are successfully fabricated via a facile colloidal route. The unique as-obtained MoSe2 nanospheres render the high-rate transporation of sodium ion due to small size and high specific surface area. As the anode, MoSe2 nanospheres yield the initial discharge/charge capacities of 520/430 mAh g-1 for potentials ranging from 0.1 to 3 V at a current rate of 0.1 C with an 80% capacity retention over 200 cycles. In addition, MoSe2 nanospheres also demonstrate excellent electrochemical performance at high current densities. Using first-principles simulation, the activation barriers for sodium ion transportation on the surface as well as interlayer of the MoSe2 are 0.344/1.31 eV respectively, suggesting that high specific surface area MoSe2 nanospheres can serve as an attractive anode material for Na ion batteries. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the effect of three key fabrication factors (i.e. pressure, AC/PTFE mass ratio, and AC load) on the performance of activated carbon air-cathode (ACAC). The design of experiment work was performed with the response surface methodology (RSM) using the central composite design. 20 combinations of the three variables were optimized based on the responses evaluated by linear sweep voltammetry (LSV). The results showed that the proposed mathematical model in the RSM could be used adequately for prediction and optimization within the factor levels investigated. The combined optimum fabrication parameters that gave the highest performance of ACAC were pressure 10 MPa. AC/PTFE mass ratio 6 and AC load 0.3 g. The fabricated ACACs were characterized by Electrochemical Impedance Spectroscopy (EIS), Brunauer-Emmett-Teller (BET) test and fuel cell test. The characterization results demonstrated that the improved performance of ACAC owed to the increase of both specific surface area and conductivity, and the controlled surface hydrophilicity/hydrophobicity. [ABSTRACT FROM AUTHOR]

Metal-coordinated nitrogen-doped carbons are catalytically active for oxygen reduction reaction (ORR). The present study describes in detail the ORR on Fe-coordinated, pyrrolic nitrogen-doped graphene (FeN4-G) based on a density functional theory calculation. On this model, pathways of four- and two-electron reductions are investigated for ORR. The most feasible four-electron reduction pathways are arranged in the following order: O2(ads)→OOH(ads)→O(ads)+H2O(ads) (or 2OH(ads))→OH(ads)+H2O(ads)→2H2O(ads). Free energy diagrams show that the elementary steps of the ORR along the four-electron pathway are downhill at a low electrode potential (up to 0.41 V vs. standard hydrogen electrode). The rate-determining step appears at the OH(ads)-to-H2O(ads)reduction, with a reaction barrier of 1.02 eV. The two-electron reduction product H2O2 can chemisorb on the surface. However, the free energy diagrams show that the reduction of OOH into H2O2 remains uphill for all positive electrode potential vs. the normal hydrogen electrode. The high endothermic AG value of H2O2 formation indicates that the two-electron ORR pathway is unfavorable on FeN4-G catalysts. [ABSTRACT FROM AUTHOR]

As a promising anode material for Li-ion batteries, pristine Cr2O3 powder shows poor cycling performance due to its low electrical conductivity, the unstable of SEI film and large volume change during cycling. To better understand these problems, anode material Cr2O3/C composite is prepared by high-temperature solid-state reaction, the lithiation mechanisms of the commercial Cr2O3 and Cr2O3/C composite electrodes have been investigated by electrochemical impedance spectroscopy (EIS), respectively. It is found that at the thermodynamic equilibrium voltage for the conversion reaction, the Nyquist plots of the commercial Cr2O3 and Cr2O3/C electrodes both consist of three semicircles and an inclined line, and the three semicircles are ascribed to the Li ion migration through the surface film, the electronic properties of the material, and a charge transfer step, respectively. Furthermore, an equivalent circuit including elements related to the electronic and ionic transport as well as the charge transfer process is put forward to simulate the experimental EIS data. Variations of kinetic parameters for lithiation of Cr2O3 as a function of potential in the initial discharge process are discussed in detail, and the reasonable explanation is given. [ABSTRACT FROM AUTHOR]

Cycle life prediction is an essential component in the health management of nickel hydrogen battery. Before cell fail, the electrical behavior EODV could reduce with the use. This paper presents a multi-phase EODV degradation model through aging mechanism study and experimental data analysis to evaluate the extent of deterioration of the battery at a specified future time. The model incorporates parameter transformation and accelerated extrapolation for different stress testing. By using such a model, the EODV of the Ni-H2 cell over time for varied stress aging conditions can be accurately described. The model and inference methods are illustrated with a case application involving charge-discharge test of 15 N-H2 cells in accelerated condition. The test results are as expected. [ABSTRACT FROM AUTHOR]

A heat resistant and flame-retardant polysulfonamide/polypropylene composite nonwoven has been developed and exploited as an advanced separator for high performance lithium ion battery via melt-blown spinning followed by a phase-inversion process. It was manifested that such composite nonwoven exhibited improved flame retardance, superior thermal resistance and better electrolyte wettability as compared to commercialized polypropylene separator. It was also demonstrated that the lithium cobalt oxide (LiCoO2)/graphite cells employing the composite separator possessed better rate capability and superior cycling stability than those of polypropylene separator. Furthermore, this study verified the beneficial impact of polysulfonamide/polypropylene composite separator with respect to commercial polypropylene separator on cycle performance of lithium iron phosphate (LiFePO4)/lithium (Li) cells even at an elevated temperature of 120°C. These fascinating results suggest that such composite nonwoven is promising separator for high performance lithium ion battery. [ABSTRACT FROM AUTHOR]

A novel anion exchange composite membrane was prepared based on glutaraldehyde crosslinked quaternized chitosan (QCS) and positively charged polystyrene (PS). The PS was synthesized by emulsion polymerizing styrene monomers in an ethanol aqueous solution (1:2, v:v) containing a surfactant of cetyltrimethyl ammonium bromide (CTAB) and an initiator of potassium persulfate (KPS). The obtained PS microemulsion with an average diameter of 709 nm exhibited a zeta potential of +88.4 mV due to the enwrapped CTAB cations. The positive charges carried by the PS facilitated the composite membrane to have a high ion exchange capacity without increasing the methanol permeation. The conductivities of the membranes at a level of 10-2S cm-1 were achieved at 80°C. The methanol permeability of the membranes was in a range of 2.7 x 10-6 - 3.3 x 10-7cm². The obtained anion exchange membranes were stable up to 200°C in air atmosphere according to the data of thermal gravimetric analysis. The tensile stress at break of the membranes was in a range of 16.9-24.9 MPa under ambient atmosphere, and 12.2-13.4 MPa of which were retained after immersing the membranes in a 10 mol L-1 KOH solution at room temperature for 96 h. [ABSTRACT FROM AUTHOR]

A two-step hydrothermal method is reported here for the synthesis of a sulfur-graphene hybrid material. The scanning electron microscopy, X-ray diffraction and Raman spectroscopy characterizations have confirmed that this method can produce a homogeneous sulfur coating on the graphene surface and prevent the graphene sheets from aggregation simultaneously to form a three dimensional carbon network. When tested as a cathode in lithium sulfur batteries, the hybrid material exhibits a high discharge capacity and good cycling stability at a current density of 1 A/g, even as the sulfur content reaches an extremely high level (75.2% wt). Its excellent electrochemical performance can be attributed to the stable carbon skeleton formed by the monolayer graphene sheets and the good contact between sulfur and graphene. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for the detection of chloramphenicol (CAP) was developed by modifying carboxyl acid functionalized multiwall carbon nanotubes (c-MWNTs) doped with gold nanoparticles (AuNPs) with a molecularly imprinted polymer (MIP) film on the surface of a glassy carbon electrode (MIP/c-MWNTs-AuNPs/GCE). The resulting electrode exhibited good performance for CAP detection based on the recognition capability of the imprinted film, as well as the specific surface area and electron transfer ability of c-MWNTs doped with AuNPs. A linear response to a concentration range of 0.1-100 mg L-1 (r2 = 0.9962) and a detection limit (with a signal to noise ratio of 3) of 0.024 mg L-1 CAP were achieved under optimized conditions. When penicillin-G (Pen-G), thiamphenicol (TAM) and p-nitrophenol (p-NP) were used as the interferents, the MIP/c-MWNTs-AuNPs/GCE sensor showed good selectivity and interference immunity, and the signal responses of Pen-G and TAM were 0.11% and 5.8% that of the response for CAP, respectively. The MIP/c-MWNTs-AuNPs/GCE electrode showed a pronounced electrochemical response to CAP, and as such constitutes a promising strategy for the electrochemical detection of CAP. [ABSTRACT FROM AUTHOR]

Electrochemical luminescence (ECL) under anodic polarization involves an excitation process that is analogous to the excitation process of inorganic electroluminescence (EL) devices, i.e., the so-called impact excitation process. ECL is suitable for facilitating the exploration of new materials to be used for fabricating EL devices, because the luminescent property associated with ECL can be examined by simple electrochemical measurements without fabricating an emitting device. In the present study, MgIn2O4 (MgGaxIn2-xO4) doped with various amounts of Ga3+ were synthesized and their ECL property was investigated to develop a new white-emitting EL material. The ECL spectra of the MgGaxIn2-xO4 largely depended on the doped Ga3+ content. The main peak in the emission spectra of a sample with x = 0.1 was a broad one (400-600 nm). With an increase in the Ga3+ content, the MgGaxIn2-xO4 samples with x = 0.2 and 0.3 showed two sharp emissions (in the form of lines) in the green region and these two sharp lines became main luminescence in the sample with x = 0.3. The surface of an electrode showed white-plane emission in the sample with x = 0.3. This change in the luminescent property upon changing the Ga3+ content appears to be caused by the change in the distribution of the Ga3+ ions in the MgGaxIn2-xO4 structure [ABSTRACT FROM AUTHOR]

The compounds, Li1.03Mn1.97O4 and Li1.06Mn1.94O4 were prepared by the polymer precursor method followed by heat treatment at 650°C for 6 hours in air. X-ray and neutron diffraction, scanning electron microscopy, and the Brunauer-Emmett-Teller surface area and density determination techniques were used to characterise the compounds. The lattice parameters obtained using neutron diffraction data of Li1.03Mn1.97O4 and Li1.06Mn1.94O4 are smaller than the parent LiMn2O4 at a = 8.20717(17) and 8.22899(13) Å, respectively. Cyclic voltammetry studies were carried out in the potential range of 3.5-4.4V at scan rate of 0.058 mV/sec. Li-doped LiMn2O4 showed the main cathodic and anodic redox peaks at ~3.9/4.0 and ~4.1/4.15V, respectively. The reversible charge capacities of Li1.03Mn1.97O4 with an applied current rate of 360 mA g-1 at the end of 2nd and 230 th cycle are 88 and 83 (±3) mAh g-1, respectively. At a current rate of 600 mA g-1 these charge capacities are 67 and 61 (±3) mAh g-1, respectively. Li1.06Mn1.94O4 shows a capacity of 64 and 62 (±3) mAh g-1 at the end of 2nd and 100th cycles, respectively, at a current rate of 360 mA g-1. [ABSTRACT FROM AUTHOR]

Because of an improved mass transfer process, chemical energy in a liquid phase, which has been absorbed into the micro-pores of porous electrodes, may be electrochemically converted into electrical energy at a high rate and with a long cycle life. Based on this principle, we demonstrated methods for a new electrochemical storage device, which had higher specific power, a much longer cycle life than existing storage batteries and a greater specific energy than existing supercapacitors. Even at the high current rate of 80 C for deep charge/discharge, a long cycle life (30,000) and good utilization efficiency have been achieved. This new device may be developed into a new family of energy storage systems with a variety of applications. The first important practical application could be on-board, rechargeable electric energy storage devices for electric vehicles. [ABSTRACT FROM AUTHOR]

LiNi1/3Co1/3Mn1/3O2 with a well-ordered layered structure, which is confirmed by X-ray diffraction, was synthesized by the sol-gel method. The electrochemical performance of LiNi1/3Co1/3Mn113O2 was investigated in a 2 M LiNO3 aqueous solution and in an organic solution. LiNi1/3Co1/3Mn1/3O2 showed a much better rate capability in the aqueous solution than in the organic solution; both charge and discharge processes were finished in a few seconds. The cycle performance of the LiNi1/3Co1/3Mn1/3O2 electrode with different charge/discharge rates from 80 to 200C was tested, and it exhibited good cycle performance in the aqueous solution with only 9.1% capacity loss after 1000 cycles at 80C (charge and discharge processes both within 20 s). The diffusion coefficients of lithium ion in the bulk of LiNi1/3Co1/3Mn1/3O2 in the aqueous and organic solutions were calculated to be 1.39 X 10-1s and 1.51 X 10-10 cm2/s, respectively, by slow scan cyclic voltammetry. The electrochemistry impedance spectrum indicates that Ret in the aqueous solution is less than I Ω, which is 1-2 magnitude lower than in the organic solution. The fast and stable interfacial charge transfer in the aqueous solution should lead to improved electrochemical performance. [ABSTRACT FROM AUTHOR]

The effects of temperature on the formation of graphite/LiCoO2 batteries were studied using various electrocheinical techniques, such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and battery performance testing: Results showed that the coulombic efficiency of the first charge and discharge for batteries at 25°C was higher than that at 50°C. The batteries with different formation temperatures of 25 and 50°C exhibited very similar cycling performance at 25°C. The EIS of batteries at 25°C was composed of two overlapped semicircles at high to medium frequency and a slope line at low frequency, while the EIS of batteries at 50°C was composed of an inductive loop at very high frequency followed by two overlapped semicircles at high to medium frequency and a slope line at low frequency. The bulk resistance (Rct) of batteries at 50°C was much larger than that at 25°C. The resistance of solid electrolyte interface (RSEI) and charge-transfer resistance (Rb) of batteries at 50°C, which were subjected to 50 cycles at 50°C, were increased greatly, and the cycle performance of batteries became obviously worse with the increase in formation temperature. [ABSTRACT FROM AUTHOR]

Phenolic-based activated carbon fibers (ACFs) were prepared by catalytic activation using Zr(acac)4 and ferrocene in CO2, respectively. The presence of the metal catalysts can promote the formation of mesopores and enhance the electric conductivity, particularly in the presence of Zr(acac)4. The electrochemical performance of the ACFs as electrodes of electric double-layer capacitors in 1 mol L-1 LiClO4/propylene carbonate (PC) was studied using galvanostatic charge/discharge and ac impedance techniques. The number of ions participating in the double layers per surface area unit increases with increasing the pore size above 11 Å, and from 25 to 81 Å it is nearly constant. The capacitance per unit mesopore surface area (8.08 µF cm-2) is higher than that per unit micropore surface area (4.29 µF m-2) at a current density of 50 mA g-1. The organic ions could enter the larger pore easily and quickly. But if the pore size is larger than 26.5 Å, the ac impedance increases due to the poor electric conductivity of the ACFs. The optimal pore size seems to be around 25 Å in LiClO4/PC solution. [ABSTRACT FROM AUTHOR]

Y3Al5O12:Tb3+ phosphor was prepared by using a sol-gel method and the process of particle growth was investigated by X-ray diffraction, scanning electron microscopy, particle size, and Brunauer-Emmett-Teller surface area measurements. As-dried Y3Al5O12:Tb3+ precursor is amorphous bulk. After heating above 800°C, the samples become polycrystalline powders. The low-temperature heated sample (e.g., 900°C) has a porous texture with large particle size (>10 μm). When the samples are heated at higher temperatures (e.g., 1100°C), the pores become larger and the grains start to appear. When the samples are heated at 1400°C, the large-size particles break into small particles (~1 μm), which are actually agglomerated particles by even smaller grains (in submicrometer scale). Under the excitations of the low-voltage cathode ray (<1500 V), the phosphor prepared in this sol-gel method has brighter cathodoluminescent intensity than the commercial phosphor. [ABSTRACT FROM AUTHOR]